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NBS TECHNICAL NOTE 837

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology

and facilitate their effective application for public benefit. To this end, the Bureau conducts

research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology,

the Institute for Computer Sciences and Technology, and the Office for Information Programs.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United

States of a complete and consistent system of physical measurement; coordinates that system

with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of a Center for Radiation Research, an Office of Measurement Services and the following divisions: Applied Mathematics — Electricity — Mechanics — Heat — Optical Physics — Nuclear

Sciences 2 — Applied Radiation 2 — Quantum Electronics * — Electromagnetics 3 — Time

and Frequency " — Laboratory Astrophysics s — Cryogenics s

. THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to improved methods of measurement, standards, and data on the properties of well-characterized

materials needed by industry, commerce, educational institutions, and Government; provides

advisory and research services to other Government agencies; and develops, produces, and

distributes standard reference materials. The Institute consists of the Office of Standard

Reference Materials and the following divisions: Analytical Chemistry — Polymers — Metallurgy — Inorganic Materials — Reactor

Radiation — Physical Chemistry.

THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to promote

the use of available technology and to facilitate technological innovation in industry and Government; cooperates with public and private organizations leading to the development of

technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute consists of a Center for Building Technology and the following divisions and offices: Engineering and Product Standards — Weights and Measures — Invention and Innovation — Product Evaluation Technology — Electronic Technology — Technical Analysis — Measurement Engineering — Structures, Materials, and Life Safety * — Building

Environment * — Technical Evaluation and Application 4 — Fire Technology.

THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides technical services designed to aid Government agencies in improving cost effec- tiveness in the conduct of their programs through the selection, acquisition, and effective

utilization of automatic data processing equipment; and serves as the principal focus within

the executive branch for the development of Federal standards for automatic data processing

equipment, techniques, and computer languages. The Institute consists of the following

divisions: Computer Services — Systems and Software — Computer Systems Engineering — Information Technology.

THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and

accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and

a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum

accessibility to the scientific information of the world. The Office consists of the following

organizational units: Office of Standard Reference Data — Office of Information Activities — Office of Technical

Publications — Library — Office of International Relations.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234.

2 Part of the Center for Radiation Research.

3 Located at Boulder, Colorado 80302.

4 Part of the Center for Building Technology.
Icmaf Bureau of &taft4*nk

L 1 6 1974

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50

53 Barrier Penetration Tests

;7

Raymond T. Moore

Computer Systems Engineering Division

Institute for Computer Sciences and Technology ^ , National Bureau of Standards

Washington, D.C. 20234

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Sponsored by

Defense Nuclear Agency (DNA)

Washington, D.C. 20305

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U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued June 1974
Library of Congress Card Catalog Number: 74-600107

National Bureau of Standards Technical Note 837

Nat. Bur. Stand. (U.S.), Tech. Note 837, 191 pages (June 1974) CODEN: NBTNAE

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.46:837). Price $2.15
CONTENTS

Page

CONTENTS Ill

ILLUSTRATIONS IV

ABSTRACT 1

1. INTRODUCTION 1

2

TEST OBJECTIVES 3

3. TEST IDENTIFICATION 5 4

INSTRUMENTATION 6

5

RESULTS OF TESTS ON THE BARRIER PANELS 9

5.1 Panel 1 9 5.1.1 Test 1A 9

5.1.2 Test IK 11

5.2 Panel 2 17

5.2.1 Test 2A 17

5.2.2 Test 2B 22

5 . 3 Panel 3 31

5.3.1 Test 3A 31

5.3.2 Test 3M 31

5.3.3 Test 3MA 31

5.4 Panel 4 34

5.4.1 Test 4A 37

5.4.2 Test 4AM 37

5.4.3 Test 4B 37

5.5 Panel 5 40

5.5.1 Test 5A 40

5.5.2 Test 5K 44

5.6 Panel 6 44

5.6.1 Test 6B 44

5.6.2 Test 6K 48

5.7 Panel 7 52

5.7.1 Test 7A 52

5.8 Panel 8 60

5.8.1 Test 8A 60

5.8.2 Test 8A3 60

5.9 Panel 9 66

5.9.1 Test 9M 66

5.9.2 Test 9N ; 66

5.10 Panel 10 70

5.10.1 Test ION 70

5.11 Panel 11 78

5.11.1 Test 11U.... 78

5 . 12 Panel 12 78

5.12.1 Test 12U 78

5.12.2 Test 12 86

5.12.3 Test 12Q 87

5.13 Panel 13 93

5.13.1 Test 13B 93

5.13.2 Test 13D 98

5.13.3 Test 13K 98

III
Page

5 . 14 Panel 14 106

5.14.1 Test 14B 106

5 . 15 Panels 15 and 16 112

5

15 . 1 Test 15A 112

5.15.2 Test 15U 116

5.15.3 Test 16A 119

5.15.4 Test 16U 119

6. DISCUSSION OF BARRIER PANEL TEST RESULTS 123

6 . 1 Conclusions 127

7

FENCE TESTS 129

7.1 Test Instrumentation 131

7 . 2 Attack Techniques 131

7.2.1 Fl 136

7.2.2 F2 144

7.2.3 F3 151

7.2.4 F4 156

7.2.5 F5 158

7.2.6 F6 161

7.2.7 F7 168

7.3 Discussion of Fence Test Results 169

7.4 Conclusions 170

APPENDIX 172

ACKNOWLEDGMENT 177

SI Conversion Units 178

Illustrations

Figure Title Page

1 Construction of Panel 1

• 8

2 Multiple Sweep Recording of Vibrational

Disturbances; Test 1A 10

3 Opening Produced by Test.lA 10

4 Test IK. Vibration from Drilling 12

5 Spalling from Hole Pattern; Test IK 13

6 Vibrational Disturbances from Spalling ;Test IK 13

7 Cutting Reinforcing -Rod in Test IK 14

8 Construction of Panel 2 15

9 Multiple Sweep Spectra of Acoustical

Disturbances ; Test 2A 16

10 Multiple Sweep Spectra of Vibrational

Disturbances ; Test 2A 16

11 Vibrational Disturbances Using a 6-pound Cutting Maul ; Test 2A 18

12 Initial Interior Crack in Fibrous

Concrete ; Test 2A 19

13 Initial 3" Diameter Breakthrough Resulting

from Sledgehammer and 6" Cutting Maul Attack; 19

Test 2A

IV
14 Attack 2A. Exterior, Attack in Process 20

15 Attack 2A. Exterior View, Final Opening 20

16 Acoustical Disturbances Resulting from Drilling ;Test 2B 21

17 Vibrational Disturbances Resulting from Drilling;Test 2B 21

18 Spalling Produced by Punch in Center Hole- Test 2B 23

19 Multiple Sweep, Typical Spectra of Acoustical

Disturbances; Test 2B 24

20 Multiple Sweep, Typical Spectra of Vibrational

Disturbances; Test 2B 24

21 Breakthrough Hole after Numerous Blows; Test 2B 25

22 Enlarged Opening with 26-lb. Bar; Test 2B 25

23 Exterior View, Final Enlarged Breakthrough; Test 2B 26

24 Construction of Panel 3 28

25 Opening Produced by 6-lb. Chopping Maul; Test 3A 29

26 Multiple Sweeps of Acoustical Disturbances from

Cutting Maul; Test 3A 29

27 Multiple Sweeps of Vibrational Disturbances from

Cutting Maul ; Test 3A 30

28 Completed Opening, Test 3MA 30

29 Acoustical Disturbances Resulting from

Abrasive Wheel Saw; Test 3MA 32

30 Vibrational Disturbances Resulting from

Abrasive Wheel Saw; Test 3MA 32

31 Construction of Panel 4 33

32 Panel 4 Prior to Tests 34

33 Vibrational Disturbances Produced by Rotohammer's

1-1/2" Toothed Chisel; Test 4A 35

34 Vibrational Disturbances Produced by 14"

Gasoline-Powered Wheel Saw ; Test 4A 35

35 Multiple Sweeps of Vibrational Disturbances

Resulting from Use of 6-lb. Chopping Maul; Test 4B 36

36 Construction of Panel 5 38

37 Multiple Sweeps of Acoustical Disturbances

Produced by 10 lb. Sledgehammer; Test 5A 39

38 Multiple Sweeps of Vibrational Disturbances

Produced by 10 lb. Sledgehammer; Test 5A 39

39 Opening Produced by Test 5A 40

40 Test 5K, Battering Ram Suspended from A-Frame 41

41 Test 5K. Single Man Using Suspended Battering

Ram, Raising Center of Gravity 24" 41

42 Multiple Sweeps of Acoustical Disturbances

Produced by Ram; Test 5K 42

43 Multiple Sweeps of Vibrational Disturbances

Produced by Ram; Test 5K 42

44 Construction of Panel 6 43

45 Acoustical Disturbances Produced by Rotohammer

and 3/4" Drill; Test 6B 45

46 Vibrational Disturbances Produced by Rotohammer

and 3/4" Drill; Test 6B 45
47 Multiple Sweeps of Acoustical Disturbances

Produced by Punch and 10 lb. Sledgehammer; Test 6B 46

48 Multiple Sweeps of Vibrational Disturbances

Produced by Punch and 10 lb. Sledgehammer; Test 6B 46

49 Acoustical Disturbances Resulting from

Oxyacetylene Cutting Torch; Test 6B 47

50 Opening Produced by Test 6B 47

51 Opening Produced by 50 -lb. Battering Ram and

No. 14 Bolt Cutters; Test 6K 48

52 Construction of Panel 7 49

53 Multiple Sweeps of Acoustical Disturbances

Produced by 10 lb. Sledgehammer; Test 7A 50

54 Multiple Sweeps of Vibrational Disturbances

Produced by 10 lb. Sledgehammer; Test 7A 50

55 Test 7A with Ferro-cement Reinforcing

Wires Exposed 51

56 Acoustical Disturbances Produced by No. 14

Bolt Cutters; Test 7A 51

57 Vibrational Disturbances Produced by No. 14

Bolt Cutters; Test 7A 53

58 Test 7A. Cutting Wires with Torch for Time

Comparison 53

59 Construction of Panel 8 55

60 Test 8A, Beginning of Attack 56

61 Acoustical Disturbances Resulting from 10-lb.

Sledgehammer Attacks; Test 8A 56

62 Vibrational Disturbances Resulting from 10-lb.

Sledgehammer Attacks; Test 8A 57

63 Opening Produced in Test 8A 57

64 Acoustical Disturbances from Bolt Cutters; Test 8A 58

65 Vibrational Disturbances from Bolt Cutters; Test 8A 58

66 Test 8A3, Abrasive Wheel Saw 59

67 Opening Produced by 14" Abrasive Wheel Saw; Test 8A3 59

68 Acoustical Disturbances Produced by Abrasive

Wheel Saw; Test 8A3 61

69 Vibrational Disturbances Produced by Abrasive

Wheel Saw; Test 8A3 _ 61

70 Construction of Panel 9 62

71 Panel 9, Hubless Saw Attack; Test 9M 63

72 Acoustical Disturbances Produced by Saw; Test 9M 63

73 Vibrational Disturbances Produced by Saw; Test 9M 64

74- Test 9M, Completed Opening 64

75 Acoustical Disturbances Produced by Abrasive

Wheel Saw; Test 9M 65

76 Vibrational Disturbances Produced by Abrasive

Wheel Saw; Test'9M 65

77 Acoustical Disturbances Produced by Saw; Test 9N 67

78 Vibrational Disturbances Produced by Saw; Test 9N 67

79 Test 9N in Process 68

80 Test 9N. Completed Opening 68

VI
81 Construction of Panel 10 69

82 Vibration Disturbances Produced by Battering

Ram Attacks ; Test ION 71

83 Test ION, Completed Opening 71

84 Vibrational Disturbances Produced by Cutting

Maul ; Test 10 N 72

85 Construction of Panel 11 73

86 Acoustical Disturbances Produced by Cutting

Maul; Test 11U 74

87 Vibrational Disturbances Produced by Cutting

Maul; Test 11U 74

88 Vibrational Disturbances Produced by

Sledgehammer; Test 11U 75

89 Test 11U. Ferro-cement Reinforcing Wire

Exposed 75

90 Multiple Sweep Recording of Vibrational

Disturbances Resulting from Bolt Cutter

Attacks; Test 11U 76

91 Construction of Panel 12 77

92 Multiple Sweep Trace of Acoustical

Disturbances from Electric Drill; Test 12U 79

93 Typical Acoustical Disturbances Produced by

the Saber Saw; Test 12U 79

94 Test 12U. Final Opening 80

95 Multiple Sweep Traces of Acoustical

Disturbances Produced by Hubless Saw; Test 12 82

96 Multiple Sweep Traces of Vibrational

Disturbances Produced by Hubless Saw; Test 12 82

97 Panel 12, Siding and Sheathing Cut; Test 12 83

98 Acoustical Disturbances Produced by Attacks

from 14"Hubbed Power Saw; Test 12 83

99 Vibrational Disturbances Produced by Attacks

from 14" Hubbed Power Saw; Test 12 84

100 Acoustical Disturbances Produced by Attacks

from 14" Hubbed Power Saw ; Test 12 84

101 Vibrational Disturbances Produced by Attacks

from 14" Center-Hubbed Saw ; Test 12 85

102 Cutting with Hubless Saw ; Test 12 85

103 Completed Opening ; Test 12 87

104 Acoustical Disturbances Produced by Drill

and Wood Bit ; Test 12Q 88

105 Vibrational Disturbances Produced by Drill

and Wood Bit ; Test 12Q 88

106 Construction of Panel 13 89

107 Test 13B. Rotohammer Drilling 90

108 Acoustical Disturbances Produced by

Rotohammer and Drill ; Test 13B 90

109 Vibrational Disturbances Produced by

Rotohammer and Drill; Test 13B 91

110 Spalling Activity in Progress; Test 13B 91

VII
111 Vibrational Disturbances Produced by Spalling

Activity; Test 13B 92

112 Enlarged Center Breakthrough; Test 13B 92

113 Test 13B, Using Taper Punch to Spall from Edge of

Holes into Central Opening 94

114 Acoustical Disturbances Produced by Burning Bar; Test 13B 94

115 Test 13B. Completed Opening 95

116 Test 13D. Beginning of Burning Bar Attack 95

117 Test 13D. Continuation of Attack 96

118 Test 13D. Close-up of Hole Melted through the

Concrete 96

119 Test 13D, Acoustical Disturbances Produced by Burning

Bar 97

120 Test 13D. Vibrational Disturbances Produced by

Burning Bar 97

121 Test 13K. Battering Ram 99

122 Test 13K. Multiple Sweep Trace of Vibrational

Disturbances Resulting from Ram Attacks 99

123 Test 13K. Two-man Operation of Suspended Battering Ram 100

124 Spalling Produced by 301 Blows from

Battering Ram; Test 13K 100

125 Construction of Panel 14 102

126 Test 14B. Acoustical Disturbances Produced by

Rotohammer and Drill 103

127 Vibrational Disturbances Produced by Rotohammer

and Drill; Test 14B 103

128 Multiple Sweep Traces of Acoustical Disturbances

Resulting from Spalling; Test 14B 104

129 Multiple Sweep Traces of Vibrational Disturbances

Resulting from Spalling; Test 14B 104

130 Cutting Reinforcing Rod with Bolt Cutters; Test 14B 105

131 Construction of Panel 15 107

132 Construction of Panel 16 108

133 Vibrational Disturbances Resulting from Knocking

Out Portions of Wall with Boot Kicks; Test 15A 109

134 Test 15A. Cutting Steel Plate 109

135 Acoustical Disturbances Produced by Torch Cutting - ±^A HO

136 Vibrational Disturbances Produced by Torch Cutting- 15A 110

137 Test 15A, Completed Opening 111

138 Multiple Sweep Recording of Vibrational

Disturbances Produced by Sledge; Test 15A 111

139 Test 15U. Kicking Out Plasterboard 113

140 Test 15LL Opening Produced by Kicking Out

Plasterboard 113

141 Test 15U. Preparing to Ignite Burner 114

142 Test 15U, Cutting with Burning Bar 114

143 Test 15U. Final Size of Opening 115

144 Test 15U. Vibrational Disturbances Produced

During Burning 115

145 Test 15U. Acoustical Disturbances Observed with

Microphone from 12' 116

VIII
146 Test 16A, Acoustical Disturbances Produced

by Torch 117

147 Test 16A, Vibrational Disturbances Produced

by Torch 117

148 Test 16A. Vibrational Disturbances Produced

by Sledgehammer 118

149 Test 16A. Final Opening 118

150 Burning Bar Cutting through Steel Reinforcing; Test 16U 120

151 Hole Produced by Burning Bar ; Test 16U 120

152 Acoustical Disturbances Produced by Burning Bar - 16U 121

153 Vibrational Disturbances Produced by Burning Bar - 16U 121

154 Single Sample of Vibrational Disturbances

Produced by Second Burning ; Test 16U 122

155 Fencing Using American Fittings to Attach

Tensions Bars to Poles 130

156 Overview of Site Configuration of Fences

during Tests 130

157 Fence Lifted 12" Using 2" X 4" Timber as

Lever; Test Fl 132

158 Climb Over Fence Using Tarpauling as Protection against Barbed Wire ; Test Fl 132

159 Climb Over Fence Using Wire Ladder; Test Fl 133

160 Vibrational Disturbances Observed 15' Away

During Placing of Wire Ladder and Climb Over ;Test Fl 133

161 Climb Over Fence Using Linesman's Pliers to

Make Steps; Test Fl 134

162 Opening Produced by Cutting 13 Wires with

No. 14 Bolt Cutters; Test Fl 134

163 Vibrational Disturbances Observed with Transducer

10' from Attack Point; Test Fl 135

164 Cuts Being Made with Combination Fencing Tool; Test Fl 135

165 Vibrational Disturbances Produced During 13 Cuts

with Combination Fencing Tool; Test Fl 137

166 Abrasive Wheel Saw in Use; Test Fl 137

167 Vibrational Disturbances Produced by

Abrasive Wheel Saw; Test Fl 138

168 Cutting Wire which Attach Outriggers to Tops

of Poles; Test Fl 138

169 Outriggers, Still Attached to Barbed Wire, Cut,

Pulled Down and Used as Hand and Foothold to

Climb Over Fence ; Test Fl 139

170 Abrasive Wheel Saw Used to Cut Nearly Full Height

of Fabric and also to Cut Off One Intermediate

Post; Test Fl 139

171 Gloved Hand Climb Over at Gate where Barbed Wire

Outriggers Were Vertical; Test Fl 140

172 Gloved Hand Climb Over Started from Inside

of Fence; Test Fl 140

173 Placing 2 X 4 in Position; Test F2 141

174 First Man Crawling under F2; Test F2 141

IX
175 First Man Inside the Enclosure ; Test F2 142

176 Beginning to Crawl under Fl ; Test F2 142

177 Both Men 50' Behind Second Fence ; Test F2 143

178 Vibrational Disturbances Produced byDiagonal Cutters at 6' ; Test F2 143

179 Opening Produced by Abrasive Wheel Saw ; Test F2 145

180 Multiple Sweeps of Vibrational Disturbances

Produced by Abrasive Wheel Saw ; Test F2 145

181 25" High Opening Produced in Lighter Gauge

Material ; Test F3 147

182 Appearance of Fabric after Dropping ; Test F3 147

183 Climbing Fence Bare-handed ; Test F3 148

184 Pulling Down Fabric from Top Tension Wire

in Preparation for Climb-over ; Test F3 148

185 Vibrational Disturbances Produced by Vise

Grip Cutters ; Test F3 149

186 Vibrational Disturbances Produced by 6"

Diagonal Cutters ; Test F3 149

187 Completed Opening ; Test F3 150

188 Vibrational Disturbances from 10' Resulting

from Fence Lifting and Man Crawling Under; Test F4 152

189 Climb Over Top of Fence ; Test F4 152

190 Vibrational Disturbances Resulting from

Bolt Cutter Attacks; Test F4 153

191 Vibrational Disturbances Resulting from

Vise Grip Cutter Attacks ; Test F4 153

192 Vibrational Disturbances Resulting from

Linesman's Pliers Attacks; Test F4 154

193 Metric Fence Pole Broken Off by Two-man Attack; Test F4 154

194 Details, Metric Fabric Attachment to Gate Frame;Test F4 155

195 Pulling Metal Fabric Away from Frame; Test F4 155

196 Timber Lift and Crawl Under; Test F5 157

197 Climb Over Top; Test F5 157

198 Lift Bottom Tension Wire and Crawl Through; Test F6 159

199 Vibrational Disturbances Produced by Lifting

Wire and Crawling Through; Test F6 159

200 Vibrational Disturbances Produced by Bolt

Cutter Attacks; Test F6 160

201 Vibrational Disturbances Produced by Vise

Grip Cutter Attacks; Test F6 160

202 Vibrational Disturbances Produced by Linesman's

Cutters Attacks; Test F6 161

203 Multiple Sweep Trace of Vibrational Disturbances

Produced by Wire Cutting; Test F6 162

204 Concertina Wire Spread Apart, Hooked to Other

Strands Resulting in Crawl Through Space; Test F6 162

205 Climb to Throw Heavy Tarpaulin over Concertina

Wire; Test F6 163

206 On Top of Fence Getting Ready to Jump; Test F6 163

X
207 Leap Clearing Concertina Wire Using

Tarpaulin as Safety Factor, Test F6 164

208 Vibrational Disturbances Produced During

Climb with Transducer 4' Away ; Test F6 164

209 Vibrational Disturbances from Bolt Cutters

on F7 ; Test F7 166

210 Cutting Metric Intermediate Post near

Ground with Abrasive Wheel Saw ; Test F7 166

211 Vibrational Disturbances Produced by

Abrasive Wheel Saw Attacks ; Test F7 167

212 Comparison of U. S. and Metric Posts ; Test F7 167

213 Cutting Full Height of Fabric with Abrasive

Wheel Saw • Test F7 168

XI

BARRIER PENETRATION TESTS

R. T. MOORE

ABSTRACT

Sixteen structural barrier panels were tested to determine their re- sistance to forcible penetration through the use of readily available

tooling. Thirteen of these represented experimental techniques to

reinforce an existing structural barrier of low penetration resistance;

the other three were designs which would be most appropriate to consider

as replacement barriers. Minimum man-passable sized openings were made

in the barriers in working times which averaged 7.85 minutes and ranged

from 1.52 to 25.56 minutes. One of the replacement and two of the

reinforcing designs showed superior cost-effectiveness.

Seven woven, wire-mesh security fence specimens were also tested

for their intrusion deterrence capability. The test results indicate

that the deterrent influence of unelectrified fences of the type tested

is largely psychological rather than physical. All of the specimens

could be penetrated in 0.14 minutes or less.

Samples of the acoustical and vibrational data produced during th«

penetration tests add to the growing body of data which are expected

to be useful in the design and selection of electronic intrusion alarm

equipments.

Key Words: Barrier penetration; intrusion detection; intrusion

resistance; physical security.

1. INTRODUCTION

The degree of protection that is afforded to computers, money or negotiable securities, weapons, classified materials, or other valuable

items, is dependent upon the effectiveness of the physical security

measures which are employed to safeguard them. Current physical

security measures are usually based on the concept of employing one or more barriers, such as fencing, a strong room or a vault to enclose a protected area coupled with one or more electronic sensors which are intended to detect penetration of the barrier (s) or any intrusion into

the protected area. Detection of barrier penetration or area intrusion

causes an alarm and initiates some form of reaction on the part of

guards, police or other forces.
The effectiveness of this approach is dependent on a number of

factors including the reliability and detection capability of the

electronic detection systems, the impregnability or penetration re- sistance of the physical barrier (s) and the response time of the

security reaction forces. The most cost-effective physical security

system must take into account the interrelationships between these

factors. A "perfect" electronic detection system might be of little

value in safeguarding a volume whose barriers could be penetrated in

five minutes if the intrusion alarm reaction time were ten minutes.

Given the same ten minute reaction time, a barrier with fifteen minutes

penetration resistance might be ineffectual if the electronic intrusion

detection alarm was not activated until the final moment of breakthrough.

During the latter part of 1971 a number of tests were conducted to

develop information useful in assessing the penetration resistance of

conventional structural barriers. Attacks were made using readily

available portable tools and penetration was assumed to have been

accomplished when an opening had been made with a minimum area of 96

square inches and having one dimension of at least six inches. The time

required to penetrate was recorded together with the acoustic, ultrasonic and vibrational disturbances produced by the attack. These tests

showed that many of the structural barriers which had a superficial

appearance of durability could in fact be breached quite rapidly. Of

the ten structural barriers tested, six were penetrated in less than one minute and only two resisted attack for more than four minutes. A 12-

inch thick brick wall required only nine minutes and an eight-inch thick

reinforced concrete floor would have required an estimated 41 minutes to

penetrate based on extrapolation of measured time for partial penetration.

These test results indicate that there may be many circumstances

where existing barriers might be reinforced in order to favorably

balance the time required for penetration against the intrusion reaction

time of security forces. The possible improvements which might be

realized through the use of unconventional combinations of materials to

reinforce an existing barrier of conventional design were of particular

interest.
A number of candidate experimental designs were prepared and submitted to interested members of the security community for review and

comment. From this, a plan evolved to construct sixteen structural

barriers and a woven-mesh fenced enclosure for testing. Thirteen of the

structural barriers reflected experimental concepts of reinforcing an existing barrier of low penetration resistance. The remaining three

represented possible designs for initial construction of barriers intended for use in applications involving a moderate level of security.

The structural barriers were constructed in the form of four un- roofed boxes using a different construction design selected from the list

for each wall. Each barrier panel was eight feet long and six feet high

so as to provide enough area for multiple attacks when alternative tooling was indicated. They were constructed on an asphalt parking area near

the south edge of the National Bureau of Standards facility. The masonry

work was completed during the fall of 1972, but the concrete and ferrocement construction was delayed by winter weather and was not completed

until April 1973. Testing was begun after a minimum curing time of 28

days.

The woven mesh fencing was constructed on a grassy area adjacent to

the barrier test site in the form of a 20' X 100' enclosure with two

double-hung gates. One-half of the enclosure was constructed from U. S.

gauge materials (two sizes) and the other half employed metric gauge

materials (five sizes). Within the enclosure, a short section of

concertina wire barrier was also set up for test. Construction of the

fencing was completed by mid-June 1973 and the testing followed immediately

thereafter.

2. TEST OBJECTIVES

The objectives of the tests on the structural and fencing barriers

were to develop estimates of the relative cost-effectiveness of

alternative materials and construction techniques; to determine the

times required to make minimum size man-passable penetration openings,

and to collect samples of the acoustic, ultrasonic and vibrational

disturbances produced by the various attacks.
The relative cost-effectiveness of a barrier can be evaluated in

terms of the amount of resistance to penetration which can be obtained

versus the cost required to obtain that resistance. This can be

expressed as the relation R = W/C, where R is the relative cost-effectiveness, W is the minimum working time required to make a penetration

of the required size and C is the cost of the barrier per unit area. Construction costs are a function of labor costs and material costs

which may both vary widely with time and geographic location. They are also influenced by the economies of scale; the cost per square foot of

a 6' X 8' test panel may be considerably different than for an enclosure

with 10,000 square feet of barrier surface area. For these reasons, it

is believed that some means of normalizing the cost factor should be

employed in order to develop a more generally applicable expression of

relative cost-effectiveness. This has been done by using the engineering cost estimates for each of the panels. In the case of the three

panels which reflect initial construction, the total cost was used. The

lowest per-square-foot cost estimate was assigned a value of unity and

the others were scaled up accordingly.

The relative cost-effectiveness of the reinforcing concepts

employed in eleven of the barrier test panels is conceptually similar

and may be expressed as: Rr = (W-X)/Cr, where X is the estimated or measured time to penetrate the barrier without the added reinforcing

(never more than two minutes) and Cr is the estimated cost of re- inforcing which is normalized against the other candidate cost estimates

as previously described.

It is important to recognize that the values of R or Rr have

limited meaning except when considered in terms of a required value of

W. Two barriers could have equal values of R but one could exhibit W

many times larger than the other. The factor W is the actual working

time required to make a penetration of the stipulated area. Working

time is considered that amount of time during which the attack tooling

is being actively employed. It does not include intervals required for

changing tools, selecting the next place to drill a hole, changing

to a fresh operator when the first attacker becomes fatigued, or similar
interruptions to an attack which would be necessary with even a skilled

team of determined attackers. Elapsed time was also recorded to take

into account these additional factors. A barrier is considered to have

been penetrated when an opening had been made which is large enough for

a small man to wriggle through. It is generally accepted that an opening having an area of 96 square inches with one dimension of at least

6" will meet this criterion. In these tests, attack areas were marked

out on the barriers in the form of either an 8" X 12" rectangle or

an 11.1" diameter circle as appropriate to the attack tooling which was

employed. In those instances where the attack produced an opening

larger than, or significantly different from these sizes, its dimensions are reported.

3. TEST IDENTIFICATION

Each proposed structural barrier target area for a penetration

attack was assigned an alphanumeric identifier which was painted on the

external surface of the selected barrier adjacent to the perimeter of

the planned opening. It is used to label test data from each attack and

is especially helpful in identifying photographic records. The

identifier consists of a number-letter sequence in which the first

number indicates the barrier to be attacked. The following letter

indicates the area of the attack and the general nature of the initial

tooling used on that area. Letters designating initial tooling were selected from the following list:

A. Sledgehammer

B. Rotohammer

C. Diamond Drill

D. Burning Bar

E. Linear-Shaped Charge

F. Demolition Saw

G. Pneumatic Jackhammer

H. Rock Melter

J. Water Jet

K. Battering Ram

M. Gasoline-Powered Rotary Saw

N. Electric-Powered Rotary Saw

P. Cutting Torch

Q. Electric Drill

R. Saber Saw

S. Brace and Bit

5
T. Bolt Cutters

U. Cutting Maul

In the case of the fencing materials, identifiers Fl through F7 were

used to cover the' seven types of material tested.

4. INSTRUMENTATION

Acoustic and ultrasonic disturbances produced by the various attadcs

were observed using a 1/4" microphone having a nominally flat frequency response to above 50 kHz . This was mounted on a small tripod arri together with its preamplifier and power supply was positioned 12' from

the attack location and in such a way as to try to minimize the pickup

of signals directly reflected from adjacent barrier panels. Since it

is unlikely that microphone positioning was completely effective in

eliminating the effects of reflected signals, no attempt has been made

to correct the observed data or compensate for minor deviations from

the nominally flat frequency response of the microphone. The data are presented as spectrum analyzer outputs and are expressed as dB above

a zero level of .0002 dynes per square centimeter. They should be

considered as representative values only.

Vibrational disturbances were picked up by piezoelectric transducers which were mounted on the interior surface of each barrier at

the longitudinal center and approximately 8" below the top edge. They

were at a distance of approximately 42" (plus the thickness of the

barrier) from the center of each attack point. The frequency response

of the transducers extended to over 100 kHz. Their associated charge

amplifiers were located within a portable protective enclosure and

were coupled by a low impedance transmission line to the data recording

position. The recorded vibrational spectra are expressed as peak g

values. These, like the acoustical and ultrasonic disturbances, should

be considered only as representative values as the natural resonances

of a panel secured on only three sides could differ considerably from

one secured on all four sides as in a room or vault.
The transmission lines from the charge amplifiers and microphone preamplifier were each terminated at a selector switch box arranged so that

either one could be selected as the input to a real-time spectrum

analyzer. The output of the spectrum analyzer was displayed on a storage tube oscilloscope and photographs were taken of samples of the

spectra of the disturbances. The data recording instrumentation was

located in a garage area adjacent to the barriers.

The spectrum analyzer was operated with a sweep width of 50 kHz, a sweep rate of 5 kHz per cm (on the display) , a sweep speed of 30 ms per

cm and a bandwidth of 500 Hz. The vertical axis of the display showed

the spectral amplitude in a logarithmic mode with sensitivity of 10 dB

per cm and covered a dynamic range of 60 dB. The type of spectrum

analyzer used does not have memory; that is, it displays those spectral

components of the signal which are within its passband at the "instantaneous" center frequency of the sweeping passband. A single sweep provides a reasonably good representation of continuous signals such as from a motor-driven tool or a cutting torch, but on intermittent

signals, such as hammer blows, many sweeps may be required to develop

an estimate of their spectrum over the full 50 kHz sweep width. This is

because on one hammer blow the passband of the analyzer may be sweeping

past the 5 kHz region and on the next it may be sweeping past the 35

kHz region. Under circumstances such as these, multiple sweeps were

collected on the storage tube oscilloscope prior to photographing them

whenever the attack duration was long enough for this to be feasible.

On most of the tests, sound pressure levels (SPL) were also observed

at distances of 8' to 12' from the attack using one of three different

handheld sound pressure level meters. One of these was equipped with a 1/2" microphone and was operated in the linear mode (no frequency

weighting filters). Data from this are reported as dB. The other two

meters were equipped with one-inch microphones and a C weighting network.

Data from these are reported as dB-C. In all cases, the distance from

the attack point to the observer is reported.
EXTERIOR

No. 8^ REINF. BAR EACH CORE

8" CONCRETE BLOCK LAID WITH

CORES IN LINE (RUNNING BOND)-

CORES FILLED WITH MORTAR

Scale 3/4 r =l-0

TYPICAL THRU SECTION

PANEL 1

Figure 1. Construction of Panel 1
Timing information on the penetration tests was obtained using two

manually-controlled clocks. The elapsed time was determined from a largeface, self-starting electric clock located within the field of view of cameras covering the attack. It was equipped with a switch in the power

cord and this was turned on at the beginning and off at the end of each

attack. Prior to each attack, the hands would be set to an integral

hour plus zero minutes and zero seconds. The accrued minutes and seconds

at the end of the , attack then indicated the elapsed time directly. Working time was accumulated on a restartable, handheld stopwatch. The

uncertainty in the accumulated working time values is believed to be on

the order of one second per increment of working time, and probably does

not exceed five percent of the total reported even in the case of the

numerous increments developed in a few of the attacks.

5. RESULTS OF TESTS ON THE BARRIER PANELS

Test results are reported sequentially by panel number although this

does not correspond to the chronological sequence of attacks which was

adjusted to accommodate a number of factors, such as weather, photographic coverage and the minimization of instrumentation relocations.

5.1 Panel 1

The construction of Panel 1 is shown in figure l.It is unlikely

that reinforcing rods and mortar fill could be added to an existing

hollow core concrete block barrier, and, while such a structure could be

built either inside or outside of an existing barrier, it is more

likely to occur as initial construction.

5.1.1 Test 1A

A ten-pound sledgehammer was used to attack the target area. The

initial breakthrough occurred after 54 blows which required 1.31 minutes

working time. After another 47 blows and 1.12 minutes, the opening had

been enlarged to approximately 12" X 15". The hammering produced SPL

readings of 87 to 88 dBC as observed at a distance of 12 feet. A

multiple sweep recording of the vibrational disturbances is shown in

figure 2. A single reinforcing rod bisected the opening and required

two cuts with an oxygen acetylene torch to remove it. The torch was

operated at 20 p.s.i. oxygen pressure and 7 p.s.i. acetylene pressure
Frequency kHz

Figure 2. Multiple Sweep Recording

of Vibrational Disturbances

Test 1A

Figure 3. Opening Produced by Test 1A

10
and a number 5 cutting tip was employed. (Unless otherwise noted, these

same gas pressures and tip size were used for all torch cuts in the test

series.) The two cuts were made by a relatively inexperienced operator

and required 1.41 minutes yielding a total working time of 3.84 minutes

and elapsed time of 5.03 minutes for the penetration shown in figure 3.

A more experienced torch operator then demonstrated that the section of

reinforcing bar removed from the opening could be cut in only 19 seconds.

It appears reasonable to expect that this operator could have completed

the penetration in a total working time of only 3.06 minutes.

5.1.2 Test IK

Using a rotohammer with 3/4-inch drill, a circular pattern of

holes was made at the target location. Five equispaced holes were to be

drilled on the circumference of a 12-1/ 4- inch diameter circle to a depth

of 5 inches. One of the holes was inadvertently drilled completely

through. At a sixth hole at the center of the circle, a reinforcing bar

was encountered at a depth of about 3-1/2 inches. Then five more holes

were drilled to a depth of 3 inches at points along the circumference of

the circle, midway between each of the 5-inch deep holes, and three

additional holes were drilled equispaced on the circumference of a smaller 5-3/4-inch diameter concentric circle. One of these latter

holes also encountered a reinforcing bar. Vibrational disturbances

produced by the drillir '.re shown in figure 4. When any reinforcing

bar was encountered, drilling on that hole was terminated and the hole

was marked so that subsequent spalling operations could readily bypass

such holes. The drilling required 3.60 minutes working time for the

nominal 54 inches giving an average rate of 4.1 seconds per inch.

11
to —

O.i

.01

.00)

• -, (111

iwliSJiiI

I

;:?

25 50

Frequency kHz

Figure 4. Test IK. Vibration from Drilling

Next, using a 10-pound sledgehammer and a variety of steel

punches, material was spalled from the bottoms of the unmarked 5-inch

deep holes on the interior of the panel. Four of these holes were

spalled out with 41 blows of the sledgehammer. The fifth hole was more

resistant and when the punch bent attention was shifted to the intermediate 3-inch deep holes. These also resisted spalling and two more

punches were bent (see figure 5) so it was decided to remove the punches

and drill an inch deeper on the unmarked 3-inch holes. These spalling

activities had consumed an additional 1.89 minutes of working time. The

extra drilling required 0.92 minute. The spalling was then resumed and

proceeded fairly rapidly, being completed in another 1.05 minutes and

producing vibrational disturbances as shown in figure 6. Typical SPL

readings of 82 to 87 dBC were observed at a distance of 12 feet.

12
Figure 5. Spalling from Hole Pattern;

Test IK

o.i-

.01 IMIIrtl

.001 25

Frequency kHz

Figure 6. Vibrational Disturbances from Spalling ; Test IK.

13
At this point the total accumulated working time was 7.55 minutes

and the interior spalling had reduced the thickness of the panel to

about 4 inches over nearly all of the target area. A 50-pound battering ram was then tried against this remaining thickness. It was handheld

by two operators who swung it against the wall by it's steel handles.

This proved to be quite unsatisfactory. The impact shocks that were

transmitted back through the handles were greater than the operators

could tolerate, and after only five blows the ram was abandoned in

favor of the 10-pound sledgehammer which was effective in clearing out

the opening with 55 blows delivered in 1.28 minutes. Then the oxygen

acetylene torch was employed for 1.25 minutes to cut out the reinforcing

bar (see fig. 7). The total working time was 10.22 minutes and elapsed

time was 12,42 minutes.

Figure 7. Cutting Reinforcing Rod in Test IK

14
EXTERIOR

o

i

INTERIOR

8 CONCRETE BLOCK LAID

WITH CORES IN LINE

(RUNNING BOND). CORES

FILLED WITH MORTAR

3' THICK CONCRETE REINFORCED

WITH .010 x 3"STEEL FIBERS

2 1/2 FLAT-HEAD, CASE-HARDENED

NAILS SPACED 6"o.c. BOTH WAYS

DRIVE INTO MASONRY APPROX. l" Scale 3/4" =

TYPICAL THRU SECTION

PANEL 2

Figure 8. Construction of Panel 2

15
134

114 "

dB

25

Frequency KHz

Figure 9. Multiple Sweep Spectra of

Acoustical Disturbances : Test 2A

25

Frequency kHz

Figure 10. Multiple Sweep Spectra of

Vibrational Disturbances; Test 2A

16
5.2 Panel 2 The construction of Panel 2 is shown in figure 8. Here, a mortarfilled concrete block wall has been reinforced with a 3-inch thick

lining of fibrous concrete which was bonded to the block by 2-1/2-inch

case-hardened nails which were driven one inch into the block prior to

casting the liner.

Prior experience had indicated that a mortar-filled 8-inch thick

block wall could be penetrated in less than two minutes— and that a 4-inch thick reinforced fibrous concrete barrier could be penetrated in

2/ less than 10 minutes— . In combination, however, they proved to be

unexpectedly resistant and penetration required more than twice the

working time necessary for any of the other panels in this series.

5.2.1 Test 2A

The attack was initiated with a 10-pound sledgehammer. Typical

multiple sweep spectra of the acoustical disturbances are shown in

figure 9 and the vibrational disturbances in figure 10. After 324 blows,

which required 7.80 minutes of working time and 20 minutes elapsed time,

an opening had been produced which had dimensions of approximately 15" X

14" X 5" deep. The average SPL during this portion of the attack was approximately 86 to 90 dB as observed at a distance of 12 feet.

It had been noted that the sledgehammer seemed to be somewhat

ineffective in removing the mortar filling which appeared to absorb the

energy of the hammer blows with minimal surface spalling so a 6-pound

cutting maul was brought into play. The cutting edge of this tool

appeared to remove more mortar per blow than the sledgehammer. It

produced quite similar vibration disturbances as shown in figure 11.

1/ NBSIR 73-223, Penetration Tests on JSIIDS Barriers, June 4, 1973,

R. T. Moore.

2/ NBSIR 73-101, Penetration Resistance Tests of Reinforced Concrete

Barriers, December 1972, R. T. Moore.

17
to -i

,.:.:. - .. -

o.i —

Figure 11,

25

Frequency kHz

Vibrational Disturbances

Using a 6-pound Cutting Maul,

Test 2A

After 100 blows, the depth of the opening was increased to 7-1/2 inches.

These produced SPL readings of 80 to 85 dB at a distance of 12 feet and

increased the accumulated working time to 10.09 minutes and the elapsed

time to 26.05 minutes. Then the sledgehammer attack was resumed in

order to enlarge the area of the opening slightly to permit better hammer

access to the fibrous concrete lining. Forty additional blows enlarged tie

surface of the opening to approximately 17" X 19", and, after 20

more blows, the liner was reached and immediately the SPL readings increased to 96 to 98 dB at 12 feet. After another 81 blows, an initial

interior spalling crack appeared as shown in figure 12. Four more blows

and the initial breakthrough occurred. This was about three inches in

diameter and approximately the size of the sledgehammer head. It may be

seen in figure 13. On the interior, the spalled surface was irregular in

shape and approximately 13" X 17". This breakthrough required 469 blows

from the sledgehammer and 100 blows from the 6-pound cutting maul which

were delivered in 13.74 minutes working time and 36.42 minutes elapsed

time.

18
.

2 f\

' v V

HnBHBBSRHi

Figure 12. Initial Interior Crack

in Fibrous Concrete ; Test 2A

Figure 13. Initial 3" Diameter Breakthrough

Resulting from Sledgehammer and

6" Cutting Maul Attack; Test 2A

19
m

will

Figure 14. Attack 2A. Exterior, Attack

in Process

mBKmKSBBBKKBmmBmKlmSm

Figure 15. Attack 2A. Exterior View,

Final Opening

20
Frequency kHz

Figure 16. Acoustical Disturbances

Resulting from Drilling;

Test 2B

10 —i

.001

0.1 —

.01

?.5 Frequency kHz

Figure 17. Vibrational Disturbances

Resulting from Drilling;

Test 2B

21
Thereafter, the opening was enlarged by using the cutting maul

and sledgehammer in alternating series of blows as in figure 14 . The

final 96 square inch opening was nearly circular in shape and appears

in figure 15. It required 725 blows with the 10-pound sledgehammer and

300 blows with the 6-pound cutting maul. The total working time was

25.56 minutes giving an average time of 1.575 seconds per blow. The

elapsed time was 58.75 minutes. The penetration was accomplished by a fresh two-man team of Marines who were in excellent physical condition

and who were motivated to try to better penetration times which had been

recorded in prior tests involving Army and Navy personnel. It is believed that a five-man team of intruders would be necessary in order to

reduce the elapsed time to a value just slightly greater than the

working time for an attack of this type and duration.

5.2.2 Test 2B

The plan for attack 2B was to attempt to spall off the fibrous

concrete liner under the target area and then break through the concrete

block. Eight holes, 3/4" in diameter, were drilled with the rotohammer

equally spaced around the circumference of a 12"-diameter circle and a ninth hole was drilled in the center. All were drilled to a depth of

8". This required a working time of 3.77 minutes and 5.62 minutes of

elapsed time. The average drilling rate was 3.95 seconds per inch.

Samples of the acoustical, figure 16, and vibrational, figure 17,

disturbances are typical.

Next, a 3/4" diameter bull point punch was inserted in the

center hole. When 40 blows on this with a 10-pound sledgehammer bent

the punch and failed to spall through the liner, it was decided to try

to spall in easier stages and alternate holes around the periphery of

the attack circle were drilled 1-1/2" deeper to a point which was calculated to be halfway through the liner. These four holes were then

quickly spalled out with the punch using a total of only six blows from

the sledgehammer. At this point the working time was 6.40 minutes and

elapsed time was 8.42 minutes.

22
A 12" cut nail (1/2" square) was then used as a punch in one of

the 8" deep holes and it was bent after only five blows. The bent punch

in the center hole was still jammed in place, so it was decided to free

it by drilling next to it and, in so doing, enlarge the hole to accept

a larger punch. A 1-1/4" taper punch was inserted in the enlarged center

hole, and, after 55 more blows with the 10-pound sledgehammer, the hole was spalled through. An interior view of the spalling is shown in

figure 18. Typical spectral of the acoustic disturbances are shown in

figure 19, and the vibration disturbances in figure 20, both of which

are multiple sweep exposures. At this point, the test was suspended to

permit acquisition of more punches. The accumulated working time was

7.68 minutes and the elapsed time 10.53 minutes.

Figure 18. Spalling Produced by

Punch in Center Hole

;

Test 2B

23
134

114 —

dB

Frequency kHz

Figure 19. Multiple Sweep, Typical

Spectra of Acoustical

Disturbances ; Test 2B

25

Frequency kHz

Figure 20. Multiple Sweep, Typical

Spectra of Vibrational

Disturbances; Test 2B

24
Figure 21. Breakthrough Hole

after Numerous Blows:

Test 2B

Figure 22. Enlarged Opening with

26-lb. Bar ; Test 2B

25
Figure 23. Exterior View, Final

Enlarged Breakthrough;

Test 2B

I

26
The test was resumed after more punches had been obtained, and

spalling began on the four intermediate holes which were 8" deep. These

were cleared with 29 blows of the 10-pound sledgehammer which took 0.59

minute working time. Then a direct attack was begun on the remaining

central section of the target area using the 10-pound sledgehammer.

After 120 blows, only the outer shell of the concrete block had been

cleared so attack tooling was shifted to a 26-pound wrecking bar using

the chisel pointed end. After a total of 140 blows with the bar and at an accumulated working time of 13.97 minutes, a 2" X 4" breakbrough hole

was developed as shown in figure 21. This was enlarged with another 61

blows with the bar, figure 22, and then the 1-1/4" tapered punch was usai

in each of the peripheral holes to spall the remaining material into

the central opening. Four of the holes were spalled out in 210 blows

with the 10-pound sledgehammer „ then the 26-pound bar was used for

another 80 blows. Then three more peripheral holes were spalled into

the central opening using the 1-1/4" diameter taper punch and 19

sledgehammer blows. A final 20 blows with the 10-pound sledgehammer and

123 blows with the 26-pound bar brought the opening to the required size

as shown in figure 23. The total working time was 26.55 minutes and the

elapsed time was 33.5 minutes. In addition to the drilling operations,

it required 484 blows with the 10-pound sledgehammer and 424 blows with

the 26-pound bar. A three-man attack team was used until the time that

the test was suspended and a six-man team worked when the test was

resumed. This larger attack team size accounts for the more favorable

ratio of working-to-elapsed time as compared with test 2A.

27
INTERIOR

3/4 No.9 EXPANDED METAL

I "THICK LAYER OF 40pcf

POLYURETHANE FOAM

3/4" PLYWOOD

8" CONCRETE BLOCK LAID

IN RUNNING BOND

PANEL 3

Figure 24. Construction of Panel 3

28
t?

Figure 25. Opening Produced by

6-lb. Chopping Maul;

Test 3A

134

114 -

dB

94

74

i

54-

fil

25

Frequency kHz

J

I I II I 1 1 I

~150

Figure 26, Multiple Sweeps of Acoustical

Disturbances from Cutting Maul;

Test 3A

29
io -a

o.i

.01

.001

'I

25

Frequency kHz

50

Figure 27. Multiple Sweeps of Vibrational

Disturbances from Cutting Maul

Test 3A

wmgmumit*><>*-> '»dm>»> t

31

3

Figure 28. Completed Opening, Test 3MA

30
5.3 Panel 3

The construction of Panel 3 is shown in figure 24. It represents

an experimental concept for reinforcing a hollow concrete block barrier

with a variety of different materials which hopefully might have re- quired frequent changes in attack tooling or perhaps even be destructive

to tooling. The panel reinforcing proved difficult to fabricate and

ranked rather low in cost-effectiveness.

5.3.1 Test 3A

With the 6-pound chopping maul, 80 blows in 2.11 minutes working

time produced an opening approximately 6" X 6" in size through the plywood, polyurethane, expanded metal and the outer layer of the concrete

block, as shown in figure 25. Multiple sweeps of the acoustical and

vibrational disturbances that were produced are shown in figures 26 and

27, respectively. Then, using the forked end of the 50-pound battering

ram in a two-man attack for 16 blows, the concrete block was completely

broken through and the face of the opening enlarged to 8" X 8". With

27 more blows from the maul and 22 more from the ram, the opening was

enlarged to 14" X 7-1/2". Then a few light blows with the 10-pound

sledgehammer flattened the broken, expanded metal against the sides of

the opening to provide the necessary area (see fig. 28). The total

working time was 3.84 minutes and the elapsed time 5.17 minutes.

5.3.2 Test 3M

A 14" diameter hubless, gasoline-powered rotary saw with carbidetipped blade was used to make a test cut. It penetrated the wood,

polyurethane and expanded metal readily, but, on encountering the

concrete block below this reinforcing, the carbide tips were broken off

of all but five of the blade teeth.

5.3.3 Test 3MA

Since test 3M was unsuccessful, a 12" abrasive wheel saw attack

was set up as an alternate.

An 8" X 12" rectangular attack area was laid out and the abrasive

wheel saw cut through the plywood, expanded metal and polyurethane along

this perimeter in 2.51 minutes working time, 4.03 minutes elapsed time.

Samples of the acoustic and vibrational disturbances produced are shown

31
134

U4

dB

Figure 29,

25

Frequency KHz

Acoustical Disturbances Resulting

from Abrasive Wheel Saw; Test 3MA

10

O.t -

.001

.0001- 25

Frequency kHz

Figure 30. Vibrational Disturbances Resulting

from Abrasive Wheel Saw; Test 3MA

32
EXTERIOR

1 "THICK LAYER OF 40pcf

POLYURETHANE FOAM

2 THICKNESSES DIAMOND

MESH PLAS. LATH

8" CONCRETE BLOCK LAID

IN RUNNING BOND

PANEL 4

Figure 31. Construction of Panel 4

33
in figures 29 and 30, respectively. Sawing was then continued into the

concrete block to the maximum depth permitted by the abrasive wheel

which was about 3". This extended the working time to a total of 8.31

minutes. Then, using a crowbar for 0.4 minute, the plywood, polyurethaie

and expanded metal plug was pried off of the wall. There was rather

poor adhesion between the polyurethane and the concrete block.

Nineteen blows with the 50-pound battering ram cleared the

concrete block from the opening. The total working time was 9.17 minutes

and the elapsed time was 11.17 minutes. The attack could probably have

proceeded much more rapidly if the 5.80 minutes spent cutting the

concrete block with the abrasive wheel saw had been omitted.

5.4 Panel 4

The construction of Panel 4 is shown in figure 31. It was similar

to Panel 3 but did not employ the outer layer of plywood and had two

layers of metal plaster lath in place of the 3/4" No. 9 expanded metal.

The difficulty of fabrication is evidenced by the condition of the

reinforcing materials prior to the attacks as shown in figure 32. The

attacks scheduled for locations 4A and 4B were exchanged as a convenience

to the operators to provide more clearance for attack tooling.

Figure 32. Panel 4 Prior to Tests

34
10 —

I

0.1

.01 -

.001 -j

Figure 33.

25 50

Frequency kHz

Vibrational Disturbances Produced

by Rotohammer's 1-1/2" Toothed Chisel;

Test 4

A

10

o.t

.01

.001 -

.0001-

25

Frequency kHz

Figure 34. Vibrational Disturbances Produced

by 14" Gasoline-Powered Wheel Saw ; Test 4A

35
1 — iMi! o.t — SIMM

BHHHMH

mmmmMMIMNMI

.01 — 1H1II DmmMMIMHM

HBTOW

001

i

1 25

Frequency kHz

Figure 35. Multiple Sweeps of

Vibrational Disturbances

Resulting from Use of

6-lb. Chopping Maul;

Test 4B

50

36
5.4.1 Test 4A

The rotohaimner, equipped with a 1-1/2" toothed chisel, was used

in an attempt to cut through the polyurethane and metal lath around the

perimeter of the target area. After 30 seconds the chisel broke. Just

prior to the break, the vibrational disturbances shown in figure 33 were

observed.

A new test was then started at this location using the 14"

gasoline-powered abrasive wheel saw. In 6.77 minutes working time the

target area perimeter had been cut to a depth ranging from 4-1/4" to 5"

through the polyurethane, metal lath and concrete block. Samples of

the vibrational disturbances are shown in figure 34. SPL readings of

102 to 106 dB were observed at a distance of 12'.

Then 14 blows with the 26-pound bar cleared the opening with a total working time of 7.87 minutes.

5.4.2 Test 4AM

The test was then repeated except that the abrasive wheel saw was

used to cut only through the polyurethane and metal lath. Thirty-five

blows from the 26-pound bar completed the opening in a total working time

of 2.64 minutes and elapsed time of 2.66 minutes.

5.4.3 Test 4B

Using the 6-pound chopping maul, 40 blows effectively cleared the

reinforcing materials from the target area. Multiple sweeps of the

vibrational disturbances are shown in figure 35. Then 33 blows with the

10-pound sledgehammer cleared the concrete away making the complete

penetration in 1.9 minutes working time and 2.83 minutes elapsed time.

SPL readings of 84 to 89 dB were observed at a distance of 12'.

37
EXTERIOR

O

i Vd

INTERIOR

4 BRICK a 4 BLOCK LAID IN COMMON BOND WITH FULL

HEADER EVERY 7th BRICK COURSE

3/4"No.9 EXPANDED METAL

NAILED IN PLACE 6"o.c.

4" CONCRETE BLOCK

PANEL 5

Figure 36. Construction of Panel 5

38
134

114 —

dB

94

74

54-

Figure 37,

25 50

Frequency kHz

Multiple Sweeps of Acoustical

Disturbances Produced by 10 lb.

Sledgehammer; Test 5A

Frequency kHz

Figure 38. Multiple Sweeps of Vibrational

Disturbances Produced by 10 lb.

Sledgehammer; Test 5A

39
5.5 Panel 5

The construction of Panel 5 is shown in figure 36. Reinforcing has

been applied to the interior of the wall in the form of a layer of

expanded metal and 4" thick concrete block.

5.5.1 Test 5A

The 10-pound sledgehammer was used to attack the target area. Multiple sweeps of the acoustical disturbances are shown in figure 37

and the vibrational disturbances in figure 38. SPL readings of

84 to 95 dBC were observed at 12'. Initial breakthrough occurred after

2.66 minutes working time and 106 blows. Forty-six more blows enlarged

the opening to an oval shape approximately 14" X 9" and flattened the

expanded metal against the sides of the hole. The final opening is . shown in figure 39.

Figure 39. Opening Produced by Test 5A

40
Figure 40. Test 5K. Battering Ram

Suspended from A-Frame

Figure 41. Test 5K. Single Man Using Suspended

Battering Ram, Raising Center of

Gravity 24"

41
114

94 -

dB

74 -f

54-

34

1

L

• wmwmmm

ro

i 25 50

Frequency kHz

Figure 42. Multiple Sweeps of Acoustical

Disturbances Produced by Ram ; Test 5K

!0

.01 ««_mvmmmm

.001 25 50

Frequency kHz

Figure 43. Multiple Sweeps of Vibrational

Disturbances Produced by Ram; Test 5K

42
EXTERIOR INTERIOR

8" CONCRETE BLOCK

(RUNNING BONO)

3/4"- No. 9 EXPANDED METAL

NAILED IN PLACE

4" CONCRETE BLOCK

*

PANEL 6

Figure 44. Construction of Panel 6

43
5.5.2 Test 5K

An A-frame was assembled from a pair of 2" X 4" X 10' planks and

clamped to the panel. The 50-pound battering ram was suspended from the

apex of this structure as shown in figure 40. Using this arrangement,

a single man could raise the center of gravity of the ram approximately

24" as shown in figure 41 and deliver a series of fairly reproducible

blows. An opening of about 15" X 5" was broken through after 66 such

blows delivered in 5.10 minutes working time. Then the ram suspension

ropes were shortened slightly and another 19 blows were delivered to

enlarge the vertical dimensions of the opening. Multiple sweeps of the

acoustical disturbances produced by the ram are shown in figure 42 and

the vibrational disturbances in figure 43. SPL values of 94 to 95 dBC

were observed at a distance of 10'.

Finally, the 10-pound sledge was used for 25 blows to complete

the development of a 12" X 9" clear opening through the flattened,

expanded metal. The total working time was 7.53 minutes. The elapsed

time was not recorded.

5.6 Panel 6

The construction of Panel 6 is shown in figure 44.

5.6.1 Test 6B

Using the rotohammer and 3/4" drill, eight equally spaced holes

were made around the perimeter of the target circle to a depth of

8". A similar ninth hole was made in the center of the circle. This

72" of drilling was accomplished in 2.06 minutes working time at an

average rate of 1.7 seconds per inch. Samples of the acoustical and

vibrational disturbances which were produced are shown in figures 45

and 46, respectively. SPL readings of 92 to 95 dB were observed at a

distance of 12'

Then the inner reinforcing layer of 4" concrete block was spalled out using a punch driven by the 10-pound sledgehammer into the

bottom of each of the drilled holes. This required a total of 112 blows

delivered in an additional 2.25 minutes of working time. It produced

SPL readings of 73 to 76 dB and acoustical and vibrational disturbances

as shown in the multiple sweep traces of figures 47 and 48, respectively.

44
134

114 —

dB

94

74

54-

llIH 111

mm

25

Frequency kHz

50

Figure 45. Acoustical Disturbances Produced

by Rotohammer and 3/4" Drill ; Test 6B

Frequency kHz

Figure 46. Vibrational Disturbances Produced by Rotohammer and 3/4" Drill

Test 6B

45
!34

114

dB

Frequency kHz

Figure 47. Multiple Sweeps of Acoustical

Disturbances Produced by Punch

and 10 lb. Sledgehammer; Test 6B

10

0.1 —

.01

.001

IK1K1 IlflFPff

mmmwm

25

Frequency kHz

50

Figure 48. Multiple Sweeps of Vibrational

Disturbances Produced by Punch

and 10 lb. Sledgehammer; Test 6B

46
134

114

dB

S4

74

54-

25 50

Figure 49.

Frequency kHz

Acoustical Disturbances Resulting from

Oxyacetylene Cutting Torch; Test 6B

'X*

Figure 50. Opening Produced by Test 6B

47
Next, the 10-pound sledge was used to break out the exterior

concrete block to expose the expanded metal. This required 80 blows and

2.62 minutes of working time. Then the oxyacetylene cutting torch was

used for 3.74 minutes to cut the expanded metal around the periphery of

the opening. It produced acoustical disturbances as shown in figure 49.

A final 0.20 minute with the 26-pound bar produced the completed

opening shown in figure 50 with a total working time of 10.87 minutes

and elapsed time of 14.45 minutes.

5.6.2 Test 6K

The 50-pound battering ram was supported by its handles by two

men and was swung for 155 blows in 3.17 minutes working time to produce

an opening with external dimensions of approximately 16" X 24". Then,

No. 14 bolt cutters were used to cut the expanded metal. This required

1.74 minutes for a total working time of 4.91 minutes and 6.40 minutes

of elapsed time and produced a clear opening of 10" X 12" as shown in

figure 51.

Figure 51. Opening Produced by 50-lb,

Battering Ram and No. 14

Bolt Cutters; Test 6K

48
INTERIOR EXTERIOR

8 CONCRETE BLOCK

(RUNNING BONO)

6 LAYERS OF 2x4 No. II Go. WELDED WIRE FENCING.

STAGGER STRANDS VERTICALLY

8H0RIZ. 8 NAIL IN PLACE

FERRO CEMENT APPLICATION

PANEL 7

Figure 52. Construction of Panel 7

49
J 34

114

dB

Figure 53,

25

Frequency kHz

Multiple Sweeps of Acoustical

Disturbances Produced by 10 lb,

Sledgehammer ; Test 7A

50

10

O.I

.01

.00!

ilHI h

mimmmx

l-requency kHz

Figure 54. Multiple Sweeps of Vibrational

Disturbances Produced by 10 lb,

Sledgehammer ; Test 7A

50

1

50
Figure 55,

f .***», « " . *

Test 7A with Ferro-cement

Reinforcing Wires Exposed

HSf

ti- i

•"- -,

i

25

Frequency kHz

i 50

Figure 56. Acoustical Disturbances

Produced by No. 14 Bolt Cutters;

Test 7A

51
5.7 Panel 7 The construction of Panel 7 is shown in figure 52. The mix

formulation used in this and the other panels which were reinforced with

ferro-cement was obtained from a manufacturer of ferro-cement boat hulls.

It is shown in table 1.

At the time that the reinforcing was applied to Panel 7, three

samples of the material were cast. These were tested on the same day

that Panel 7 was tested and developed an average compression strength

of 7780 p.s.i.

Table 1. Ferro-cement Mix

Water 40 lb.

Portland Cement 94 lb.

Sand 150 lb.

Pozzolan Densifier 15 lb.

5.7.1 Test 7A

The initial attack was with the 10-pound sledgehammer. Multiple

sweep examples of the acoustical and vibrational disturbances are shown

in figures 53 and 54, respectively. After 130 blows delivered in 3.0

minutes working time, the front face of the concrete block had been

broken out in an area approximately 18" X 24" in size to a depth of

about 6-1/2". During this portion of the attack, SPL readings of 82 to

94 dBC were observed at a distance of 12'. Then, 40 blows with the

6-pound cutting maul and 80 blows with the 26-pound bar produced the

opening shown in figure 55. At this point the total working time was

5.40 minutes and the elapsed time was 7.15 minutes.

The six layers of 2" X 4", No. 11 wire fencing were then cut with

No. 14 bolt cutters to make a clear 15" X 10" aperture. This required

105 cuts which took 5.30 minutes to make for an average of 3 seconds per

cut. Samples of the acoustical and vibrational disturbances produced

by the bolt cutters are shown in figures 56 and 57, respectively. The

total working time required for this penetration was 10.70 minutes and

the elapsed time was 14.50 minutes.

52
25

Freqjency kHz

Figure 57. Vibrational Disturbances

Produced by No. 14 Bolt Cutters;

Test 7A

1SO

Figure 58. Test 7A. Cutting Wires with Torch

for Time Comparison

53
Because of the relatively large amount of time used with the

bolt cutters, it was decided to check alternative techniques which might

have been used to cut the reinforcing wires. The opening in the

concrete block was enlarged a bit and 20 linear inches of reinforcing

wire was cut using the abrasive wheel cutoff saw. The rate was 2.35

seconds per inch, thus the 40-inch perimeter of an 8" X 12" opening

could have been cut in 0.9 minute and Test 7A could have been completed

in 6.30 minutes working time using this technique.

Finally, the oxyacetylene cutting torch was used in a similar

test as shown in figure 58. The measured cutting rate was 13.26 seconds

per linear inch and test 7A could have been completed in 9.82 minutes

using this approach.

54
INTERIOR EXTERIOR

8' CONCRETE BLOCK

(RUNNING BOND)

I LAYER OF No.9 Go. CHAIN

LINK FENCE

I LAYER OF 3/4" No.9

EXPANDED METAL

2nd LAYER OF No.9 Go.

CHAIN LINK FENCE

FERRO CEMENT APPLICATION

PANEL 8

Figure 59. Construction of Panel 8

55
Figure 60. Test 8A, Beginning of Attack

134

H4

d6 V M

74 -

54

i MMMMMMWi

25

Frequency kHz

50

Figure 61. Acoustical Disturbances

Resulting from 10-lb. Sledgehammer

Attacks; Test 8A

56
Hm.

UHL!

i

25 SO Frequency kHz

Figure 62. Vibrational Disturbances Resulting

from 10-lb. Sledgehammer Attacks;

Test 8A

¥t

Figure 63. Opening Produced in Test 8A

57
U4

Figure 64

Frequency kHz

Acoustical Disturbances

from Bolt Cutters; Test 8A

O.l -

.01

.001 - IMMMV

.0001

Figure 65,

25 50

Frequency kHz

Vibrational Disturbances

from Bolt Cutters ; Test 8A

58
Figure 66. Test 8A3, Abrasive Wheel Saw

BA

Figure 67. Opening Produced by 14"

Abrasive Wheel Saw; Test 8A3

59
5.8 Panel 8

As shown in figure 59, Panel 8 is similar to Panel 7 except for

reinforcing configuration in the ferro-cement liner.

5.8.1 Test 8A

In a manner similar to that employed in Test 7A, the 10-pound

sledgehammer was used to break out the concrete block (see fig. 60).

Acoustical and vibrational disturbances are shown in figures 61 and 62,

respectively.

After 120 blows with the sledgehammer, the 26-pound bar was used

for 80 blows to develop an opening of approximately 20" X 10" in which

the cement had all been spalled clear of the reinforcing materials.

This required 4.52 minutes of working time. Then the No. 14 bolt

cutters were used to cut the chain-link fencing and the expanded metal

reinforcing. The outer layer of chain-link fabric required 31 cuts

which were made in 1.25 minutes. The expanded metal took 59 cuts made

in 3.33 minutes and the inner layer of chain-link fabric took only 16

cuts made in 1.23 minutes as this layer could then be folded back

leaving a clear opening of 8" X 15" as shown in figure 63. Samples of

the acoustical and vibrational disturbances are shown in figures 64 and

65, respectively. The total working time for this test was 10.33 minutes and the elapsed time was 12.66 minutes.

5.8. 2 Test 8A3

Because the abrasive wheel saw had shown good performance in

cutting the ferro-cement reinforcing in Test 7A, it was decided to make

a second test on Panel 8 and use it here. A 24" X 32" target was laid

out and the front face and webs of the concrete block were broken out

with the 10-pound sledgehammer in 119 blows and 2.63 minutes working

time. SPL readings of 84 to 88 dBC were observed at a distance of 12'

during this activity. This oversize opening, as shown in figure 66, was necessary to provide room for the hub of the abrasive wheel saw. The

14" abrasive wheel was used to cut the interior face of the concrete

block and the ferro-cement liner. At the end of 9.83 minutes working

time and 12.70 minutes elapsed time, an opening 14" X 16" had been

produced as shown in figure 67. Samples of the acoustical and

60
vibrational disturbances produced by the abrasive wheel saw are shown

in figures 68 and 69, respectively. SPL readings of 99 dBC were

observed at a distance of 12'.

dB

134

114

34

74

54- 25

Frequency kHz

50

Figure 68. Acoustical Disturbances Produced

by Abrasive Wheel Saw; Test 8A3

1.0

0.1 —

.01

.001 -

.0001

Figure 69,

25

Frequency kHz

Vibrational Disturbances Produced by Abrasive Wheel Saw; Test 8A3

61

50
INTERIOR EXTERIOR

BEVEL SIDING WITH

MIN. I-I/2"LAP JOINTS

I- LAYER I5#FELT PAPER

1x6 SHEATHING DIAGONALLY LAID

2x4 STUD U6"o.c.) PARTITION

3/8" GYPSUM WALLBOARD

3/4" PLYWOOD

1/16" SHEET STEEL

{Anchor t using 10 ring (am

nails sp<

Anchor to studs

lOd annular

ichorfast ) loced 4"o.c.

PANEL 9

Figure 70. Construction of Panel 9

62
-i, L

Figure 71. Panel 9. Hubless Saw Attack;

Test 9M

dB

134

114

94

74 mmmwmiiwmm

l ' II MMMUMM~ 54- 25

Frequency kHz

50

Figure 72. Acoustical Disturbances

Produced by Saw; Test 9M

63
Frequency kHz

Figure 73. Vibrational Disturbances

Produced by Saw; Test 9M

Figure 74. Test 9M. Completed Opening

64
25

Frequency kHz

50

Figure 75. Acoustical Disturbances Produced

by Abrasive Wheel Saw ; Test 9M

Frequency kHz

Figure 76. Vibrational Disturbances Produced

by Abrasive Wheel Saw ; Test 9M

65
5.9 Panel 9 Figure 70 shows the construction of Panel 9. It represents one of

the four alternate methods which were used to increase the penetration

resistance of a typical wooden wall.

5.9.1 Test 9M

Despite the fact that the gasoline-powered hubless saw blade had

been damaged in an earlier test when many of the carbide tooth points

had been knocked off, it was used on this test to make an oversized cut

through the bevel siding and planking on the outside of the panel.

Figure 71 shows the operator preparing to begin the attack.

Acoustical and vibrational disturbances produced by the saw are shown in

figures 72 and 73, respectively. SPL readings were 102 dBC at a distance

of 12 feet. The wooden face of the panel was opened up in 2.07 minutes

and then a 10-pound sledgehammer was used to break out the exposed

2" X 4" stud in 0.34 minute to provide clear access to the inner

reinforcing layers of the panel. Then the rectangular 9" X 11" opening

shown in figure 74 was cut with the 12" abrasive wheel saw. This produced acoustical and vibrational disturbances of the type shown in

figures 75 and 76, respectively. The opening was completed in 7.46 minutes

working time and 8.03 minutes elapsed time.

Because the abrasive wheel saw had seemed to be a little less

effective than had been expected, three additional test cuts were made,

each for a nominal length of 12 inches. One used the concrete cutting

disk and required 0.89 minute; the other two were made using a metal

cutting disk and took 0.96 and 0.85 minutes, respectively. This gave an average cutting rate of 4.66 seconds per inch. Based on these data, it was concluded that the interior reinforcing layers could have been cut in

3.6 minutes which would have given a total working time for Test 9M of

only 6.01 minutes.

5.9.2 Test 9N

An electric saw equipped with a 7-1/4" carbide-tipped blade was

used to make an oversize opening through the bevel siding and planking

on the outside of the panel. This saw was not powerful enough for a very fast attack, but was used here because of its widespread availability.

66
134 ~P

114

25

Frequency kHz

Figure 77. Acoustical Disturbances

Produced by Saw; Test 9N

50

O.I-:

.ooio

Figure 7i

25

Frequency kHz

Vibrational Disturbances

Produced by Saw; Test 9N

67

50
Figure 79. Test 9N in Pro cess

Figure 80. Test 9N. Completed Opening

68
INTERIOR EXTERIOR

BEVEL SIDING WITH

MIN. 1-1/2" LAP JOINTS

l-LAYER I5#FELT PAPER

1x6 SHEATHING DIAGONALLY LAID

2x4 STUD(l6"o.c.) PARTITION

3/8" GYPSUM WALLBOARD

3/4" PLYWOOD

3/4" No.9 EXPANDED METAL

3/4" PLYWOOD

PANEL 10

Figure 81. Construction of Panel 10

69
It produced SPL readings of only 82 dBC at 12' and acoustical and vibrational disturbances as shown in figures 77 and 78, respectively. Sawing

occupied 2.62 minutes working time and then 3.10 minutes were spent with

crowbar and sledgehammer clearing the sheathing away, knocking out a

2" X 4" stud and flattening the annular ring nails with which the inner

reinforcing layers had been attached to it. A 1/2" electric drill with

3/4" bit was employed for 0.75 minute in an unsuccessful attempt to make

a hole through the inner plasterboard, plywood and steel reinforcing so that a saber saw attack could be started. The attempt was unsuccessful

because the bit was too large. A small pilot hole would have been

necessary but no smaller drill bits were conveniently at hand so the

attack switched back to the electric handsaw. It was adjusted for a depth of cut equal to the thickness of the plasterboard and plywood and

a rectangular outline was cut as shown in figure 79. The bent over nails

prevented a constant depth of cut from being attained and the plywood

plug could not be pried out of the opening.

Since these rather ineffective attack methods had now consumed

7.98 minutes working time, they were not pursued further. The 12"

abrasive wheel cutoff saw was brought into play and in another 1.96

minutes the penetration shown in figure 80 was completed. The total

working time during this rather inefficient attack was 9.94 minutes and

the elapsed time was 12.10 minutes.

5.10 Panel 10

The construction of Panel 10 is shown in figure 81. It is quite

similar to Panel 9, differing mainly in the details of the inner

reinforcing layers where 3/4" No. 9 gage expanded metal is sandwiched

between two layers of 3/4" plywood.

5.10.1 Test ION

With two operators handling the 50-pound battering ram, the outer

planking and siding was smashed through by 33 blows delivered in 0.75

minute with vibrational disturbances as shown in figure 82 and with SPL

readings of 97 dBC at 12'. The 10-pound sledge was then used to break

out the 2" X 4" stud that was exposed by the ram. This required 20

blows and 0.55 minute. The 6-pound cutting maul was then used for 25

blows and 0.66 minute to clear away some of the shattered remnants of

70
to —

1

I

0.1

.01

.001

rim!

,'uTI

• l^UHPBPMmii i —1

25

Frequency kHz

50

Figure 82. Vibration Disturbances Produced

by Battering Ram Attacks;

Test ION

Figure 83. Test ION. Completed Opening

71
the exterior planking to provide access for the battering ram to be used

against the inner reinforcing liner. Then the attack with the battering

ram was resumed. The inner liner was somewhat resilient however and

appeared to bounce the ram back into the operators without sustaining

more than modest damage. After 10 blows and 0.18 minute working time,

the ram attack was abandoned and replaced by the 6-pound cutting maul.

The initial breakthrough occurred after 57 blows with total accumulated

working time of 3.65 minutes. An additional 114 blows cut through the

plywood and expanded metal, (see fig. 83) producing an opening

14-1/2" X 9". Typical SPL readings of 96 dBC were observed during this

portion of the attack which also developed vibrational disturbances as shown in figure 84.

25

Frequency kHz

Figure 84. Vibrational Disturbances

Produced by Cutting Maul;

Test ION

72
EXTERIOR INTERIOR

BEVEL SIDING WITH

MIN. I- 1/2 " LAP JOINTS

I- LAYER 15 # FELT PAPER

1x6 SHEATHING DIAGONALLY LAID

2x4 STUD 1 16" o.c.) PARTITION

3/8" GYPSUM WALLBOARD

6 LAYERS OF 2x4 No. II Go.

WELDED WIRE FENCING.

STAGGER STRANDS VERTICALLY

8 HORIZONTALLY 8 NAIL

IN PLACE

FERRO CEMENT APPLICATION

PANEL II

Figure 85. Construction of Panel 11

73
Frequency kHz

Figure 86. Acoustical Disturbances

Produced by Cutting Maul;

Test 11U

.01

.00 i jkWws&Mwwm

25

Frequency kHz

"I50

Figure 87. Vibrational Disturbances

Produced by Cutting Maul;

Test 11U

74
0.1-

HI

L'flB E.LI urn

.001 as Frequency kHz

Figure 88. Vibrational Disturbances

Produced by Sledgehammer*

Test 11U

50

Figure 89. Test 11U. Ferro-cement Reinforcing

Wire Exposed

75
1.0 -1

0.!

.0!

.001

.0001-

mpr

4j

f T.W .HIAim

L'V'V'i'iimiiiiwi

Mm1h».io,

mvv.r mmi't mm

2 b

Frequency kHz

50

Figure 90. Multiple Sweep Recording

of Vibrational Disturbances

Resulting from Bolt Cutter

Attacks- Test 11U

76
EXTERIOR /

' INTERIOR

BEVEL SIDING WITH

MIN. 1-1/2" LAP JOINTS

I- LAYER 15 # FELT PAPER

1x6 SHEATHING DIAGONALLY LAID

2x4 STUD (l6"o.c.) PARTITION

3/8" GYPSUM WALLBOARD — 2x6* STACKED SIDE BY SIDE 8

NAILED TO EACH OTHER 8 TO

THE FRAMING

PANEL 12

Figure 91. Construction of Panel 12

77
This penetration required a total of 6.73 minutes working time

and 8.0 minutes elapsed time.

5.11 Panel 11

The constructon of Panel 11 is shown in figure 85. it, too, is

similar to Panel 9 except for the inner reinforcing which was ferrocement in this experiment.

5.11.1 Test 11U

In this test, the 6-pound cutting maul was used to break through

the exterior siding and planking with 43 blows. Acoustical and

vibrational disturbance samples are shown in figures 86 and 87, re- spectively. Then the 10-pound sledgehammer was used to break off the

exposed 2" X 4" wooden stud and to attack the ferro-cement liner. After

113 blows which produced vibrational disturbances as shown in figure 88,

the concrete was spalled clear of the reinforcing wire. This produced

SPL readings of 94 to 98 dBC at a distance of 12'. At this point a total working time of 4.71 minutes had been used and the opening was as shown in figure 89 where the ferro-cement reinforcing wires are about to

be cut with 3/8" bolt cutters. This took an additional 2.12 minutes and

produced vibrational disturbances as shown in the multiple-sweep recording

in figure 90. The acoustical disturbances from the bolt cutters were only

slightly above ambient levels. The final opening was an oval-shaped

aperture with dimensions of approximately 12" X 15". It required 6.83

minutes working time and 7.05 minutes elapsed time to complete.

5.12 Panel 12

The construction of Panel 12 is shown in figure 91. It, too, was

similar to Panel 9 except for the interior reinforcing which consisted

of stacked 2" X 6" timbers nailed to each other during stacking.

5.12.1 Test 12U

Since the cutting maul appeared to be reasonably effective in

penetrating the exterior siding and sheathing in some of the preceding

tests, it was employed here for 40 blows, followed by 28 blows from the

10-pound sledge to break out the exposed 2" X 4" stud. This exposed the

interior liner in 1.96 minutes working time. The acoustical and

vibrational disturbances were similar to those produced in penetrating

the exterior of Panels 9, 10 and 11.

78
134

114

dB

Frequency kHz

Figure 92. Multiple Sweep Trace of Acoustical

Disturbances from Electric Drill;

Test 12U

134

Frequency kHz

Figure 93. Typical Acoustical Disturbances

Produced by the Saber Saw; Test 12U

79
m *V%n

Figure 94. Test 12U, Final Opening

80
Next, a 1/2" electric drill with a 5/8" drill bit was used to

make two holes through the 2" X 6" reinforcing timbers at diagonally

opposite corners of an 8" X 12" target rectangle. This required 1.39

minutes and produced SPL readings of 74 to 78 dB as observed at a distance of 12'. A multiple-sweep trace of the spectrum is shown in

figure 92. These two holes were used as the starting points for two

horizontal cuts which were made with a saber saw equipped with a 6" long

blade having 5 teeth per inch. Each cut was approximately 9-1/2" long

and the working time for both was 4.58 minutes. The average cutting rate

through the 5-5/8" actual thickness of the stacked 2" X 6" timbers was

14.46 seconds per lineal inch. Typical acoustical disturbances produced by the saber saw are shown in figure 93.

Then, the sledgehammer, crowbar and 26-pound bar were used for

3.58 minutes to clear the plug out of the opening in which it was held

by the nails driven into it from the adjoining 2" X 6" timbers. The

final opening shown in figure 94 measured only 9-1/2" X 10" and lacked

having the requisite area by one square inch. It took 12.13 minutes

working time and 17.19 minutes elapsed time. A part of the elapsed time was used in replacing two broken blades in the saber saw which was

really too small for this attack. Therefore, another penetration was made in Panel 12 using more sophisticated attack tooling. Because of its

impromptu nature, it was identified simply as Test 12.

81
134

114

dB

94

74

54-

) 25

Frequency kHz

Figure 95. Multiple Sweep Traces of

Acoustical Disturbances

Produced by Hubless Saw;

Test 12

50

25

Frequency kHz

50

Figure 96. Multiple Sweep Traces of

Vibrational Disturbances

Produced by Hubless Saw;

Test 12

82
Figure 97. Panel 12, Siding

and Sheathing Cut;

Test 12

25

Frequency kHz

Figure 98. Acoustical Disturbances Produced

by Attacks from 14" Hubbed Power Saw

Test 12

83
Figure 99.

25

Frequency kHz

Vibrational Disturbances Produced

by Attacks from 14" Hubbed Power Saw;

Test 12

134

dB

Figure 100.

Frequency kHz

Acoustical Disturbances Produced

by Attacks from 14" Hubbed Power Saw

j

Test 12

84
10

0.1-

.01 -

.001 25

Frequency kHz

50

Figure 101, Vibrational Disturbances Produced

by Attacks from 14" Center-Hubbed Saw;

Test 12

Figure 102. Cutting with Hubless Saw

Test 12

85
5.12.2 Test 12

The 14" gasoline-powered hubless saw had been intended for use against Panel 12 because it could be used for making cuts to depths of

at least 10". The blade of this saw had been damaged in an earlier test

when all but five of the carbide tips of the teeth had been broken off.

In this damaged condition, it could not be expected to cut with normal

speed and efficiency; nevertheless, a test cut was made. The cut was

29" long and 10" deep and, since it was made from the outside of the

panel, approximately 3-5/8" of the depth of the cut was through the air

space formed by the thickness of the 2" X 4" studs supporting the outer

sheathing of the panel. The time required for this test cut was 3.66

minutes, giving an average cutting rate of 5.52 seconds per lineal inch.

Multiple sweep traces of the acoustical and vibrational disturbances

produced during this test cut are shown in figures 95 and 96, respectiveiy.

Because of the uncertainty as to the extent that the performance

of this saw was degraded by the blade damage, it was decided to use a different 14" center-hubbed, gasoline-powered saw to cut through the

outer sheathing making an oversize hole and then to make two parallel

horizontal cuts in the stacked 2" X 6" timbers to the depth permitted by

hub clearance. Then the depth of these latter two cuts would be

extended through the 2" X 6" timbers using the damaged hubless saw. It was hoped that this strategem would minimize the influence of the

damaged blade on the total cutting time.

The outer siding and sheathing was cut off and removed in 1.44

minutes as shown in figure 97. It produced the acoustical and

vibrational disturbances shown in figures 98 and 99, respectively. Then

two horizontal cuts approximately 13" long were made, one above the other

and 18" apart, to a depth of about 4" into the 2" X 6" timbers. These

required 1.73 minutes working time and produced the acoustical and

vibrational disturbances shown in figures 100 and 101, respectively.

The hubless saw was then used for 2.51 minutes to extend the

depth of the two horizontal cuts completely through the panel reinforcing

as shown in figure 102.

86
The nailed timbers in the remaining plug were driven out with

the 10-pound sledgehammer in 46 blows delivered in 1.11 minutes. The

resulting opening shown in figure 103 measured 13" X 18" and was produced in 6.79 minutes working time and 9.70 minutes elapsed time. It is

estimated that both of these times could have been reduced at least a minute if a replacement blade for the hubless saw had been available.

Figure 103. Completed Opening

Test 12

5.12.3 Test 12Q

A single hole was drilled through the 5-5/8" thickness of one of

the 2" X 6" reinforcing timbers using a 1/2" electric drill and a 1-1/2"

flat blade, wood bit. The time required was 1.16 minutes giving an average drilling rate of 12.3 seconds per inch. The acoustical and

vibrational disturbances which were produced are shown in figures 104 and

105, respectively.

87
Figure 104. Acoustical Disturbances Produced

by Drill and Wood Bit; Test 12Q

1.0

.01

.001

.000!

Frequency kHz

Figure 105. Vibrational Disturbances Produced

by Drill and Wood Bit

; Test 120

88
INTERIOR

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EXTERIOR

8" THICK CONCRETE WALL

(LIGHT WEIGHT AGGREGATE)

No. 5 REINF. BARS 6"o.c

BOTH WAYS

PANEL 13

Figure 106. Construction of Panel 13

89
I4B ^s

';'-- 1214

Figure 107. Test 13B. Rotohammer Drilling

134

114

94

74

54-

I

25

Frequency kHz

50

Figure 108. Acoustical Disturbances Produced

by Rotohammer and Drill; Test 13B

90
to

I —

O.I

.01

.001 T~

25

Frequency KHz

n

50

Figure 109. Vibrational Disturbances Produced

by Rotohammer and Drill ; Test 13B

Figure 110. Spalling Activity in Progress.

Test 13B

91
25

Frequency kHz

Figure 111.

SO

Vibrational Disturbances

Produced by Spalling Activity;

Test 13B

Figure 112. Enlarged Center Breakthrough;

Test 13B

92
5.13 Panel 13

The construction of Panel 13 is shown in figure 106. The concrete

used in constructing this panel was formulated with a lightweight

aggregate and weighed approximately 120 pounds per cubic foot as con- trasted to the nominal 144 pounds for regular concrete.

5.13.1 Test 13E

As shown in figure 107, the rotohammer and 3/4" drill was used

to drill five holes to a depth of 5" at equally spaced positions around

the circumference of a 12" diameter target circle. A sixth hole was drilled to the same depth at the center of the circle. Then five more

holes were drilled to a depth of 3" along the circumference at points

midway between the 5" deep holes. Finally, three more holes were

drilled 3" deep at 120-degree intervals around a smaller concentric

5-1/2" diameter circle. The 54 linear inches of drilling required 2.16

minutes of working time for an average rate of 2.4 seconds per inch.

Samples of the acoustical and vibrational disturbances which were produced are shown in figures 108 and 109, respectively.

Next, using a 3/4" bull point punch and 10-pound sledgehammer,

the concrete was spalled from the bottoms of the drilled holes. It was intended that the 5" deep holes be spalled first, followed by the 3"

deep holes; however, due to a mix-up, this procedure was not followed

and the holes were spalled out sequentially without regard to their

depth. In spite of this, the operation proceeded rapidly and was completed in 2.74 minutes working time and 104 sledgehammer blows.

Figure 110 shows the spalling activity in progress. Typical vibrational

disturbances are shown in figure 111. SPL readings of 92 dBC were observed at a distance of 12'.

Then, the center of the target area was attacked with the 10-

pound sledgehammer. The initial penetration occurred after 35 blows and

then, as shown in figure 112, another 23 blows were used to enlarge the

central hole to a diameter of about 6". These 58 blows were delivered

in 1.43 minutes working time.

93
^^L>-''

Figure 113. Test 13B Using Taper Punch

to Spall from Edge of Holes

into Central Opening

114

Frequency kHz

Figure 114. Acoustical Disturbances

Produced by Burning Bar

;

Test 13B

94
Figure 115. Test 13B, Completed Opening

Figure 116, Test 13D. Beginning of

Burning Bar Attack

95
Figure 117. Testi3D . Continuation of Attack

Figure 118. Test 13D. Close-up of Hole

Melted through the Concrete

96
13-

114

dB

94

74 —

54- MBBSSSSBBSSm

n — __ j 25 50

Frequency kHz

Figure 119. Test 13D. Acoustical Disturbances

Produced by Burning Bar

o.i —

.01

.001

.000!- -J

Frequency kHz

Figure 120. Test 13D. Vibrational Disturbances

Produced by Burning Bar

97
Next, as shown in figure 113, a 1-1/4" diameter taper punch was driven into each of the circumferential holes spalling concrete into

the central threakthrough area. This required 86 blows and 2.38 minutes

working time. On one of the holes, spalling of the taper punch was inhibited by a reinforcing bar; this and a few other projecting knobs

of concrete were knocked clear with 13 blows of the sledgehammer in 0.28

minutes.

The burning bar was then used to cut the four sections of re- inforcing bar remaining in the opening. Using 75 p.s.i. oxygen pressure

and 18" of bar, the eight cuts were made in 0.53 minute. The acoustical

disturbances produced by the burning bar are shown in figure 114. The

completed penetration is shown in figure 115. It required 9.52 minutes

working time and 16.15 minutes elapsed time.

Three cuts were made through the 5/8" reinforcing rod using the

oxyacetylene torch so as to estimate the time which would have been

required for this penetration if the torch had been used instead of the

burning bar. The average time per cut was 0.31 minute, so the use of

the torch would have added an estimated 1.95 minutes to the working time.

Further time tests were made using alternative drill sizes in

the rotohammer. A 7/8" diameter drill penetrated the lightweight con- crete at a rate of 2.88 seconds per inch and a 1" diameter at a rate

of 3.52 seconds per inch.

5.13.2 Test 13D

The burning bar was used to make a single hole through Panel 13, as shown in figures 116, 117, and 118. At 160 p.s.i. oxygen pressure,

it consumed 38" of bar and required 0.78 minute working time and 1.08

minutes elapsed time. Samples of the acoustical and vibrational

disturbances produced are shown in figures 119 and 120, respectively.

5.13.3 Test 13K

Using the A-frame suspension shown in figure 121, the 50-pound

battering ram was used in an attack against Panel 13. For 100 blows,

the ram was swung back on its suspension harness until the center of

gravity had been lifted approximately 2'. Then it was released to swing,

pendulum fashion, against the panel. This produced surface spalling

98
wmammmmsmmmmmmmmmmmmmm

Figure 121. Test 13K, Battering Ram

10

O.l —

.01

.001 HMHMtf

L

r* .'ViMr''W»""»i "HUH

25

Frequency kHz

50

Figure 122. Test 13K. Multiple Sweep Trace of

Vibrational Disturbances Resulting

from Ram Attacks

99
Figure 123. Test 13K. Two-man Operation

of Suspended Battering Ram

• *I3K

- t m

w

Figure 124. Spalling Produced by

301 Blows from Battering

Ram ; Test 13K

100
over an area of about 6" X 7" to a maximum centel depth of 1-1/4". A

multiple sweep trace of the resulting vibrational disturbances is shown

in figure 122. SPL readings of 104 dBC were observed at 12'.

Then, for another 201 blows, the two-man operation shown in

figure 123 was employed. Here the suspension carried the weight of the ram and the operators accelerated it to the maximum velocity they could

attain and released it just before impact so as to avoid the shocks

which were transmitted back through its handles. The 301 total blows

produced the surface spalling shown in figure 124 which had attained a maximum depth of only 2-1/2 inches. The test was terminated at this

point as 10.41 minutes of working time had already been expended and

this was obviously not an effective attack technique on the reinforced

concrete of this panel.

101
INTERIOR

t£>

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EXTERIOR

2 MATTS OF No. 2 REINF.

BARS SPACED 6"o.c. BOTH

WAYS WITH 2" CLEAR EACH

FACE OF WALL

8" THICK CONCRETE WALL

(LIGHT WEIGHT AGGREGATE)

PANEL 14

Figure 125. Construction of Panel 14

102
IK —

1

94

dB

7 4 —

IT'

54 — an

34 I

EH ._

1 25

Frequency kHz

-J50

Figure 126 Test 14B. Acoustical Disturbances

Produced by Rotohammer and Drill

1.0 -i

0.1

.01 —

.001 -

.ooot 25

Frequency kHz

50

Figure 127 Vibrational Disturbances Produced

by Rotohammer and Drill ; Test 14B

103
134

114

dB

94'

74 -

54- n

inii

25

Frequency kHz

1

SO

Figure 128, Multiple Sweep Traces of

Acoustical Disturbances Resulting

from Spalling; Test 14B

10

O.I —

.0! ninmunni PWHBUMHaWI

.001 -\ —

J— 25

"150

Frequency kHz

Figure 129. Multiple Sweep Traces of

Vibrational Disturbances Resulting

from Spalling ; Test 14B

104
Figure 130. Cutting Reinforcing Rod

with Bolt Cutters ; Test 14B

105
5.14 Panel 14

The construction of Panel 14 is shown in figure 125 and is

identical to Panel 13 except that two layers of No. 2 reinforcing bars

on 6" centers both ways were used instead of the single layer of

No. 5 bars.

5.14.1 Test 14B

The attack techniques used in this test were identical to those

used in test 13B with the exception that the smaller reinforcing bars

could be cut with bolt cutters instead of requiring a burning bar or oxyacetylene torch.

The hole pattern described in test 13B was completed in 2.80

minutes for an average drilling rate of 3.11 seconds per linear inch.

Acoustical and vibrational disturbance samples are shown in figures 126

and 127, respectively.

Spalling the bottoms of the 14 drilled holes was accomplished

in the planned sequence (5" deep holes first) and required 122 blows

from the sledgehammer and 3.56 minutes working time. This represents

an average of 8.7 blows and 15.25 seconds per hole. Multiple sweep

traces of the acoustical and vibrational disturbances are shown in

figures 128 and 129, respectively.

Breakout of the center of the target area required 40 sledgehammer blows and 0.98 minute working time. Spalling from the ten

peripheral holes into the broken-out central area with the tapered

punch took 1.67 minutes and 64 sledgehammer blows for an average of

10.02 seconds and 6.4 blows per hole.

Finally, as shown in figure 130, the reinforcing rod was cut

with 3/8" bolt cutters in 0.74 minute. The 16 cuts required an average

time of 2.74 seconds each. The total working time on this test was 9.75

minutes and the elapsed time was 12.24 minutes.

106
INTERIOR EXTERIOR

3/8" GYPSUM WALLBOARD

2x4 STUD(l6"o.c.) PARTITION

3/8" GYPSUM WALLBOARD

3 5/8" No. 16 Go. SOLID WEB

STEEL STUDS SPACED l6"o.c.

FASTEN TO WOOD STUDS WITH

ANNULAR RING MONEL NAILS

S> 3"o.c.

1/4" SHEET METAL ft IN 16"

STRIPS CONTINUOUSLY WELDED

TO METAL STUDS ONE HALF OF

SURFACE SPOT WELDED OTHER

HALF OF SURFACE.

PANEL 15

Figure 131. Construction of Panel 15

107
EXTERIOR INTERIOR

3/8" GYPSUM WALLBOARD

2x4 STU Dl 1 6"o.c.) PARTITION

3/8" GYPSUM WALLBOARD

3 5/8" No. 16 Go. SOUD WEB

STEEL STUDS SPACED l6"o.c.

FASTEN TO WOOD STUDS WITH

ANNULAR RING MONEL NAILS

o> 3"o.c.

1/8" SHEET METAL £ IN 16"

STRIPS CONTINUOUSLY WELDED

TO METAL STUDS. ONE HALF OF

SURFACE SPOT WELDED.

PANEL 16

Figure 132. Construction of Panel 16

108
10 —

I

t -

0.1 —

.01 -

.001 25

Frequency kHz

Figure 133. Vibrational Disturbances

Resulting from Knocking

Out Portions of Wall with

Boot Kicks ; Test 15A

w

«m

t-M.0#"**',.

Figure 134. Test 15A. Cutting Steel Plate

109
114

Frequency kHz

Figure 135. Acoustical Disturbances

Produced by Torch Cutting;

Test 15A

10 T

o.i

.01

.001 -!

,0001-f

I

'Mi j|m|||| mil m • i||n

Figure 136.

25 50

Frequency kHz

Vibrational Disturbances

Produced by Torch Cutting ; Test 15A

110
Figure 137. Test 15A • Completed Opening

.001-

O 25

Frequency kHz

Figure 138. Multiple Sweep Recording of

Vibrational Disturbances

Produced by Sledge; Test 15A

111
5.15 Panels 15 and 16

The construction of panels 15 and 16 is shown in figures 131 and

132. Both were 2" .X 4" studded walls covered by plasterboard and

reinforced with an interior lining of mild steel which was 1/4" thick on Panel 15 and 1/8" thick on Panel 16. The steel reinforcing was cut into

16" wide strips and welded to steel studs which were fastened to the

interior side of the wooden studs. Over half the interior of each panel,

the steel reinforcing strips were continuously seam-welded to the steel

studs. On the other half of each panel, the welding was intermittent

1" long spots on 12" centers.

5.15.1 Test 15A

This test was made in the spot-welded portion of the panel. With

several boot kicks, the plasterboard was knocked out on both sides of the

wooden studded portions of the wall and the larger broken pieces were

cleared out of the way by hand. The working time was 0.64 minute and a sample of the vibrational disturbance is shown in figure 133. Then, as shown in figure 134, the oxyacetylene torch was used to make two

horizontal cuts through the steel reinforcing for the full width of the

16" strip. The cuts were separated vertically by a distance of about

16" and were intended to permit this section of the reinforcing to be

broken out by sledgehammer by tearing out the spot-welds. The 32 linear

inches of torch cutting required 6.86 minutes working time and produced

acoustical and vibrational disturbances as shown in figures 135 and 136,

respectively. SPL readings of 71 dBC were observed at 12'. The average

cutting rate was 12.86 seconds per inch.

When the cuts were complete, 25 blows from the 10-pound sledge

fractured the spot-welds and produced the clear opening shown in figure

137. These required 0.76 minute working time and produced the vibrational disturbances shown in the multiple sweep recording of figure 138.

SPL readings of 108 dBC were observed at 12' distance during the sledgehammer attack. The total working time was 8.26 minutes and the elapsed

time was 8.37 minutes. A savings in elapsed time was realized by lighting off the torch while the plasterboard was being kicked out.

112
Figure 139. Test 15U. Kicking Out Plasterboard

Figure 140. Test 15U. Opening Produced by

Kicking Out Plasterboard

113
Figure 141. Test 15U. Preparing to

Ignite Burner

I5U

Figure 142. Test 15U. Cutting with

Burning Bar

114
m

Figure 143. Test 15U, Final Size of Opening

10

0.1 —

.01 ~

.001 -

.0001 25

Frequency kHz

Figure 144. Test 15U. Vibrational

Disturbances Produced

During Burning

115
5.15.2 Test 15U

This test was conducted at a location where the steel reinforciig was continuously welded so the entire perimeter of the opening was cut

out using the burning bar.

As shown in figures 139 and 140, the plasterboard was kicked and

cleared out of the target area in 0.24 minute. Then, figure 141, the

burning bar was ignited with the oxyacetylene torch and the steel lining

was cut out, figure 142, leaving an opening with dimensions of approximately 12"X 14" as shown in figure 143.

The burning bar was operated at 75 p.s.i. oxygen pressure and

consumed 59" of bar in the 1.99 minutes it took to make the opening.

The average cutting rate was 2.3 seconds per linear inch. A sample of

the vibrational disturbances produced during the burn is shown in figure

144. Acoustical disturbances observed with the microphone at a distance

of 20' are shown in figure 145. SPL readings of 82 dBC were observed

at a distance of 12'. The total working time was 2.23 minutes and the

elapsed time was 3.52 minutes.

Figure 145. Test 15U. Acoustical Disturbances

Observed with Microphone from 20'

116
114 —

Figure 146. Test 16A. Acoustical Disturbances

Produced by Torch

10

0.1

.01

.00!

.000!- lums^mmmn

25

Frequency kHz

50

Figure 147. Test 16A. Vibrational Disturbances

Produced by Torch

117
Frequency kHz

Figure 148. Test 16A. Vibrational Disturbances

Produced by Sledgehammer

^,

Figure 149. Test 16A. Final Opening

118
5.15.3 Test 16A

Test 16A was conducted on the spot-welded portion of Panel 16.

The sledgehammer was used to break out the plasterboard with

four blows and 0.38 minute working time. Then the two horizontal cuts were made with the oxyacetylene torch. The time required for this was

quite long; 5.51 minutes which represents an average cutting rate of

10.33 seconds per inch. Samples of the acoustical and vibrational

disturbances produced by the torch are shown in figures 146 and 147,

respectively.

The spot-welds were broken out with seven blows from the 10-

pound sledgehammer in 0.26 minute working time. A multiple sweep

recording of the vibrational disturbances produced by the sledgehammering

is shown in figure 148.

The final opening is shown in figure 149. It took 6.15 minutes

working time and 7.63 minutes elapsed time to complete.

The torch operator felt that there had been improper flow

settings on the cutting torch, so, after readjusting torch controls, but

not gas pressures, two similar cuts were made in an adjacent section of

the reinforcing. These were completed in 2.14 minutes working time with

an average cutting rate of 4.48 seconds per inch, more than twice as fast as the first cuts. Three blows from the sledgehammer completed the

opening in 2.39 minutes working time. Allowing 0.38 minute (the value

measured on the first attempt) to clear out the plasterboard, the second

penetration was completed in an estimated working time of 2.77 minutes.

5.15.4 Test 16U

This test was conducted on the continuously-welded portion of

Panel 16.

The plasterboard was kicked out of the target area in 0.46

minute. Then a two section (20') long burning bar was used (see fig. 150)

to cut through the steel reinforcing. It was operated at 75 p.s.i.

oxygen pressure and consumed 52" of bar in the 1.45 minutes working time

required to make the approximately 9" X 12" opening shown in figure 151.

Acoustical and vibrational disturbances are shown in figures 152 and

153, respectively. SPL readings at 12' were 86 dBC. Total working time was 1.91 minutes and elapsed time 2.70 minutes.

119
Figure 150. Burning Bar Cutting Through

Steel Reinforcing; Test 16U

*"?

Figure 151. Hole Produced by

Burning Bar; Test 16U

120
134

114 -

dB

94-^

74 -J

10

Frequency kHz

Figure 152. Acoustical Disturbances

Produced by Burning Bar

:

Test 16U

0.1—! H I mi'.T-l

.01 •

.00! m

-!HUUVHMM — i

' 25 50

Frequency kHz

Figure 153. Vibrational Disturbances

Produced by Burning BarTest 16U

121
Because the length of the bar in this test was such as to make

it unwieldy and difficult to handle, a second penetration was made with

a shorter bar. This time a 10" X 13-1/2" opening was made in 1.06

minutes, consuming only 39" of bar. This represented an average cutting

rate of 1.35 seconds per linear inch. Allowing the same time for

clearing the plasterboard as in the first penetration (0.46 minute) this

test could have been completed in an estimated total working time of

1.52 minutes. A single sample of the vibrational disturbances during

the second burn is shown in figure 154.

.0001-

25

Frequency kHz

50

Figure 154. Single Sample of Vibrational

Disturbances Produced by

Second Burning; Test 16U

122
6. DISCUSSION OF BARRIER PANEL TEST RESULTS

The time required to penetrate a given structural barrier is

dependent upon a number of factors in addition to the materials and

techniques used in the construction of the barrier itself. The power

and sophistication of the tooling used to make a penetration is important but often the selection of the best tooling may have less influence

on the penetration time than will skill and expertise in exploiting the

capabilities of that tooling through utilization of optimum attack

techniques. Test 16A illustrates this point. In a second attempt on this test, the working time was more than halved using the same tooling

as in the first penetration.

The skill, strength and numbers of the intruders are significant

factors in most penetrations. The ubiquitous sledgehammer was a necessary tool in most of the tests, but it's effectiveness is dependent

upon the power and accuracy with which it's blows can be delivered.

Even a powerful man appears to find it difficult to sustain a vigorous

sledgehammer attack for more than a minute or two without rest, and a five- or six-man team would probably be required to maintain a continuous sledgehammer attack for as much as 30 minutes.

Foreknowledge of barrier construction is a significant factor as without this it is possible to damage or destroy tooling which may

encounter unexpected materials. This will always delay, and, at times,

may even frustrate an attempted penetration.

Available working space will certainly influence the time required

to make a penetration. This test series did not attempt to investigate

this factor but its influence has been observed occasionally on prior

tests.

Inadequate ventilation at a target area can increase the time re- quired for a penetration as several of the more useful tools produced

copious amounts of dust, fumes, heat or smoke which may quickly render

an enclosed and poorly ventilated area uninhabitable. Gasoline-powered

tools, and especially the abrasive wheel cutoff saw, are particularly

liable with respect to fumes and dust, and the burning bar with respect

to sparks, heat and smoke.

123
The accessibility of the target area to vehicular traffic is another

important but unmeasured consideration. Some of the attack tooling or support facilities,, such as oxygen tanks or portable electric power

generation equipment, are not easily transported for long distances

without vehicular assistance.

The experience reflected in the planning and execution of a penetration can have a large influence in the efficiency of the effort and the

minimization of the time that is required.

Motivitation is probably a more significant factor in a test series

such as this than it is in a penetration made to further some nefarious

objective. In the latter instance, the motivation must be great enough

to offset the risk of detection and apprehension. In a test series,

this real sense of pressure is missing and some sort of substitute, such

as a sense of competition, must be utilized.

It is believed that the best of most of these factors were present

in this test series. The power and sophistication of the tooling available reflected the state-of-the-art of reasonably portable tooling,

excepting only explosives which were ruled out by choice. One or more

operators were experienced in the use of virtually all items of tooling.

The attack team had members of outstanding strength and stamina and,

in all but a couple of tests, were sufficiently numerous so that

individual operator fatigue was not a major factor. There was foreknowledge of the construction of each barrier panel, ample working space

and the unrestricted ventilation afforded by an outdoor test site freely

accessible to vehicular transportation. Test participants included

members of the security community with many years of collective ex- perience in planning and conducting barrier penetrations. This

experience has resulted in the evolution of techniques which have

reduced the time necessary to penetrate eight-inch thick concrete by a significant factor in the course of four test series which have been

conducted during the past two years. For these reasons it is believed

unlikely that the shortest working times recorded for any one of these

tests would be significantly bettered by an actual intruder attacking a like barrier with comparable tools.

124
Table 2 is a summary listing of the test results showing the tooling,

in abbreviated form, and the measured or calculated time to make each

penetration.

Test

1A

1A

IK

2A

2B

3MA

3A

4A

4AM

4B

5A

5K

6B

6K

7A

7A

7A

8A

8A3

9N

9M

9M

ION

11U

12U

12

13B

14B

15A

15U

16A

16A

16U

16U

Table 2. Summary of Test Results

Tooling Employed

W

(Working time,min.)

Sledge, torch

Calculated based on repeat of torch cut

Rotohammer, punch, ram, sledge, torch

Sledge, cutting maul

Rotohammer, punch, sledge, bar

Abrasive wheel, pry bar, sledge

Cutting maul, ram, sledge

Abrasive wheel, sledge, bar

Abrasive wheel (shallow cut) , bar

Cutting maul, sledge

Sledge

Ram, sledge

Rotohammer, punch, sledge, torch, bar

Bar, bolt cutters

Sledge, cutting maul, bar, bolt cutters

Calculated, using abrasive wheel instead of

cutters

Calculated, using torch instead of cutters

Sledge, bar, bolt cutters

Sledge, abrasive wheel

Electric saw, sledge, pry bar, drill, abrasive

wheel

Hubless saw, sledge, abrasive wheel

Calculated, based on repeat of abrasive wheel

cut

Ram, sledge, cutting maul

Cutting maul, sledge, bolt cutters

Cutting maul, sledge, drill, saber saw, sledge

Gasoline saw, hubless saw, sledge

Rotohammer, punch, sledge, taper punch, burning

bar

Rotohammer, punch, sledge, taper punch, bolt

cutters

Kick, torch, sledge

Kick, burning bar

Sledge, torch, sledge

Calculated, based on repeat of torch cut

Kick, burning bar

Calculated, based on repeat with shorter bar

Average working time required to make a penetration for this group of barrier panels

3.84

3.06

10.22

25.56

26.55

9.17

3.84

7.87

2.64

1.90

4.42

7.53

10.87

4.91

10.70

6.30

9.82

10.33

9.83

9.94

7.46

6.01

6.73

6.83

12.13

6.79

9.52

9.75

8.26

2.23

6.15

2.77

1.91

1.52

7.85 min.

125
In table 3 the 16 barrier test panels have been ranked In order of

decreasing time required to make the fastest penetration observed during

the test series, W. In addition, estimates are given for X, the

penetration resistance of unreinforced barriers; W-X, the added resistance imparted by the reinforcing (zero for initial construction

panels 1, 13 and 14); C, normalized cost (total cost for panels 1, 13

and 14, cost of reinforcing for all others) and R, relative costeffectiveness.

Table 3

Panel W X W-X

24.81

Cr or C*

3.72

Rr or R*

2 25.56 .75 6.67

8 9.83 .75 9.08 3.87 2.35

14 9.75 9.75 5.27* 1.85*

13 9.52 9.52 5.15* 1.84*

11 6.83 1.5 5.53 3.11 1.71

12 6.79 1.5 5.29 3.09 1.71

10 6.73 1.5 5.23 1.00 5.23

7 6.30 .75 5.55 3.96 1.40

9 6.01 1.5 4.86 1.71 2.84

6 4.91 .75 4.16 1.65 2.52

5 4.42 1.63 2.79 1.65 1.69

3 3.84 .75 3.09 5.64 0.55

1 3.06 3.06 1.85* 1.65*

15 2.23 .25 1.98 4.30 0.46

4 1.90 .75 1.15 6.17 0.19

16 1.52 .25 1.27 3.94 0.32

126
6 .1 Conclusions

Table 3 displays a number of unexpected results. Foremost of these

is the surprisingly high penetration resistance of Panel 2. In earlier

tests mortar-filled cinder block with brick veneer had been penetrated in

2.1 minutes— and four-inch thick fibrous concrete with steel reinforcing

2/ had only held up against a sledgehammer attack for 9.43 minutes— . While

Panel 2 was concrete rather than cinder block and the cores were well

filled with a void-free mortar, it lacked the brick veneer and its

fibrous concrete liner was only three inches thick and did not contain

reinforcing bars. Nevertheless it demonstrated a penetration resistance

time against two different attack techniques which was more than double

the sum of the times previously observed on presumably comparable individual components. It was also more than double the penetration time re- quired for either of the eight-inch thick, reinforced, lightweight

concrete panels (Panels 13 and 14)

Of the alternative methods for reinforcing hollow eight-inch con- crete blocks which were tested, the ferro-cement liner used on Panel 8 was best by a considerable margin.

In the case of the 2" X 4" studded barriers, none of the experimental

reinforcing techniques developed as much as seven minutes penetration

resistance, however, Panels 10, 11 and 12 were all above 6.5 minutes.

Of these, Panel 10 exhibits the higher cost-effectiveness and would

appear to be the preferred choice.

1/ NBSIR 73-223, Penetration Tests on JSIIDS Barriers, June 4, 1973,

R. T. Moore.

2/ NBSIR 73-101, Penetration Resistance Tests of Reinforced Concrete

Barriers, December 1972, R. T. Moore.

127
Most of the remaining experimental panels exhibit values of penetration resistance, frequently coupled with low-cost-effectiveness, that

would appear to argue against their application in situations where

security requirements were more than minimal.

The performance of several of the reinforcing materials and the

observed limitations in tooling capabilities suggest several intriguing

new barrier design concepts:

(1) Add to the interior of Panel 2 a 3/16"-thick steel

plate which is bonded to the fibrous concrete by means of 1-1/2"

annular ring nails on 6" centers both ways. The nails are inserted in pre-drilled holes in the steel plate prior to casting

the fibrous concrete. Such a liner would be expected to further

impede the spalling of the fibrous concrete and force the

ultimate use of flame cutting.

(2) Increase the thickness of the ferro-cement liner used

in Panel 8. The Panel 8 liner was only about 2" thick

and was quite effective for such a small thickness section.

Thickness might be increased by additional layers of chain link

fencing tied in place prior to mortoring or alternatively by

making up two liners similar to that in Panel 8 with a 1-1/2"

thick sandwich of plywood between them.

(3) Add a fibrous concrete liner to the interior of

Panel 12. This would be expected to defeat the straightforward

"two-cut and sledgehammer" attack used in test 12 and would be likely

to ruin the hubless saw blade in the process. Such a barrier

would be considerably lighter in weight than Panel 2 but might

have comparable penetration resistance.

The barrier test results reported here and prior test series (1, 2)

results indicate a potential need for a research and development effort,

supported by appropriate test and evaluation, with the objective of producing designs for cost-effective physical security barriers capable of

resisting penetration for specified working time intervals. In a given

security application, the necessary penetration resistance time must be

based on the maximum amount of time between the initial detection of a

128
penetration attempt and the response generated by that alarm. All of

the penetration tests produced acoustic, ultrasonic or vibrational, or

both, disturbances which should be readily detectable by appropriate

intrusion alarm equipments. Assuming that such equipments are employed,

it would be desirable to select a physical barrier having penetration

resistance commensurate with alarm response time.

7. FENCE TESTS

The fence tests were conducted on an enclosure 100' long and 20'

wide equipped with two double-hung gates. One-half of the enclosure

and one set of gates was constructed from American made materials. The

remainder was constructed from metric gauge materials which were

obtained from a major European manufacturer of fencing. Two U.S. gauge

and five metric gauge fencing fabrics were used.

The U. S. gauge fabric was 7' high and in accordance with Federal

Specification RR-F-00191/1. Corner posts were 2.875" outside

diameter zinc-coated steel, weighing at least 5.79 pounds per lineal

foot, and intermediate posts were 2.375" outside diameter, weighing

3.65 pounds per lineal foot. Corners were braced with 1.625" diameter

horizontal braces and 0.375" diagonal truss rods with turnbuckles. A

tension wire was erected near the top of the fence and a 0.375" diameter

tension messenger cable was erected 4" from the bottom of the fence.

The fabric was attached to these tension members by wire ties at

intervals of about 16". Outward sloping outriggers were mounted on the

posts and vertical outriggers were mounted on the gate and these carried

three strands of barbed wire.

The metric gauge fence fabric was 2 meters high. Poles were steel

tubing coated with green vinyl. Corner poles were 60 mm outside

diameter and were braced by two diagonal 40 mm outside diameter poles.

Intermediate poles were 50 mm outside diameter 1.8 mm wall thickness.

Five tension wires were strung at 40 cm intervals from top to bottom of

the fencing and were attached to the poles by plastic fasteners which

plugged into pre-drilled holes in the poles. The fabric was tied to the

tension wires with wire wraps at intervals of about 40 cm. No outriggers or barbed wires were mounted on the metric gauge portion of the

129
Figure 155- Fencing Using American Fittings

To Attach Tensions Bars to Poles

Figure 156 . Overview of Site Configuration

of Fences during Tests

130
enclosure, but a short three-coil pyramid of concertina wire was set up

on the inside of one of the metric fence sections and held in place with

wire ties to garden type steel fence posts. The metric portion of the

fence was constructed by following to the greatest extent possible the

rather limited instructions which were supplied by the manufacturer.

Where these were found lacking, improvisation was necessary. In

particular, American-made fittings were used to attach the tension bars

to the poles, as shown in figure 155.

All poles in both halves of the enclosure were set in concretefilled holes 3' deep. An overview of the site configuration during the

tests is shown in figure 156.

7.1 Test Instrumentation

The test instrumentation arrangements were the same as used on the

barrier panel tests with certain exceptions. Most of the fence tests

produced relatively low levels of acoustical disturbances. These

generally were below the ambient noise level produced by some heavy

construction equipment that was operating nearby so little meaningful

acoustical data could be collected. The vibrational disturbance data were obtained from transducers which were mounted on a wire of the fence

fabric at various (reported) distances from the attack location. After

the first few tests, it was obvious that very little high frequency

vibrational components were being produced so the bandwidth of the

spectrum analyzer was reduced to 100 Hz and the sweep rate reduced to

300 Hz per centimeter to provide increased resolution in the resulting

3 kHz bandwidth.

7.2 Attack Techniques

A generally similar series of attacks was used on all seven of the

sections of fencing. These included climbing the fence using one or more variations in technique or equipment; lifting the bottom of the

fence up using a 10' length of 2" X 4" timber as a lever and holding it

up while a man crawled under; and cutting the mesh with a variety of

tools. In the latter attack, a series of mesh wires would be cut along

a diagonal beginning at the bottom of the fence and continuing until a vertical height of 14" above the bottom tension wire (or messenger)

131
w**w &wm%%%< r$mVf,

tira

Figure 157. Fence Lifted 12" Using 2" X 4"

Timber as Lever; Test Fl

••%.«

Figure 158. Climb Over Fence Using Tarpaulin

as Protection against Barbed Wire;

Test Fl

132
Figure 159. Climb Over Fence

Using Wire Ladder

Test Fl

.001

.0001-

TM

25

Frequency kHz

50

Figure 160, Vibrational Disturbances Observed

15' Away During Placing of Wire

Ladder and Climb Over ; Test Fl

133
JNMfc "381

Figure 161. Climb Over Fence Using

Linesman's Pliers to

Make Steps ; Test Fl

w ~M fl Fl 5®W5Kj^

•V »-»-><,-.;'.

Figure 162. Opening Produced by

Cutting 13 Wires with

No. 14 Bolt Cutters; Test Fl

134
to

I —

0.1 —

.01 —

.001

T

50

Frequency kHz

Figure 163. Vibrational Disturbances

Observed with Transducer

10' from Attack Point;

Test Fl

Figure l6h . Cuts Being Made with Combination

Fencing Tool; Test Fl

135
had been reached. This would produce a flap which would freely hinge

back to provide a clear 96 square inch (or larger) opening. Successive

cuts using alternative tools would be made cutting the same number of

wires one mesh interval away from the original cut. In a few instances

other attacks which will be described were made.

7.2.1 Fl. Fence section Fl was No. 9 gauge, 2" mesh, galvanized wire.

Despite the 3/8" messenger cable at the bottom of the fence, it

could be lifted 12" using the 2" X 4" timber as a lever as shown in

figure 157. It took 0.10 minute to lift and one man to crawl under.

A climb over the top was made in 0.15 minute using a folded

tarpaulin for protection against the barbed wire as shown in figure 158.

That time included throwing the tarpaulin in place.

As shown in figure 159, another climb over the top was made using

a wire ladder. The ladder was thrown over the top of the fence and the

inside end was attached to the fence fabric using a pair of carabiners.

The time required to place the wire ladder and climb over was 0.46

minute. Vibrational disturbances as observed with a transducer approximately 15' away are shown in figure 160.

Another climb was made as shown in figure 161 using linesman's

pliers to make steps. One handle of the pliers is inserted through the

mesh of the fabric and the downward pointing jaws of the pliers are inserted in the next lower mesh opening. This wedges the pliers in

place with the remaining handle hanging outward for use as a handhold or

step. This tends to be somewhat slow and awkward and 1.13 minutes were

used on this climb.

Using the No. 14 bolt cutters, it took 0.32 minute to cut 13

wires and produce the opening shown in figure 162. With the transducer

10' from the attack point, the vibrational disturbances were as shown

in figure 163.

Cuts were attempted with a pair of vise grip cutters and with 8"

linesman's pliers, but neither were heavy enough to cope with the No. 9

gauge wire. The cutting slots of a combination fencing tool were

adequate however, and, as shown in figure 164, the 13 cuts were made in

0.76 minute producing the vibrational disturbances shown in figure 165.

136
Frequency kHz

Figure 165. Vibrational Disturbances Produced

During 13 Cuts with Combination

Fencing Tool ; Test Fl

Figure 166. Abrasive Wheel Saw in Use;

Test Fl

137
to

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ISw* j*"BL«s

25

~i50

Frequency kHz

Figure 167 Vibrational Disturbances Produced

by Abrasive Wheel Saw; Test Fl

Figure 168. Cutting Wires which Attach

Outriggers to Tops of Foles ; Test Fl

138
Figure 169. Outriggers, Still Attached to Barbed Wire,

Cut, Pulled Down and Used as Hand and

Foothold to Climb Over Fence; Test Fl

Figure 170. Abrasive Wheel Saw Used to Cut

Nearly Full Height of Fabric and

also to Cut Off One Intermediate Post;

Test Fl

139
Figure 171. Gloved Hand Climb Over

at Gate where Barbed Wire

Outriggers Were Vertical;

Test Fl

Figure 172. Gloved Hand Climb Over Started

from Inside of Fence; Test Fl

140
3ft * V W ' P

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Figure 173. Placing 2 X 4 in Position;

Test F2

:

Figure 174. First Man Crawling under F2;

Test F2

141
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Figure 175. First Man Inside the Enclosure;

Test F2

Figure 176. Beginning to Crawl under Fl;

Test F2

142
Figure 177. Both Men 50' Behind Second Fence;

Test F2

10 "1

0.1

001

1,500

Frequency Hz

3,000

Figure 178, Vibrational Disturbances Produced

by Diagonal Cutters at 6'; Test F2

143
The abrasive wheel saw was then used, as shown in figure 166, to

make two cuts and form a triangular opening 17"wide and 15" high. This

required 0.17 minute working time and 0.48 minute elapsed time and produced vibrational disturbances, as shown in figure 167. The transducer

was approximately 12' from the attack location.

Then, as shown in figure 168, the wire ties attaching the outriggers to the tops of the poles were cut. Two of the outriggers were

removed and, with the barbed wire still attached, it was pulled down

and used as a hand and foothold to climb over the fence, as shown in

figure 169. Leather gloves were used for hand protection during the

climb over. This was a rather slow technique and required 1.12 minutes.

Later, the abrasive wheel saw was used to make a cut for nearly

the full height of the fabric in 0.26 minute and to cut off one of the

intermediate posts in 0.34 minute, as shown in figure 170.

Two more gloved hand climb overs were made. One was at the gate

where the barbed wire outriggers were vertical rather than sloping. As

shown in figure 171, this required 0.06 minute. The other, as shown in

figure 172, was started from the inside of the fence and took 0.08

minute.

7.2.2 J_2 Fence section F2 was No. 11 gauge, 2" mesh, vinyl-coated

wire and was otherwise identical to Fl and for this reason no climbs

were made over the top.

Using the 2" X 4" timber, the bottom of the fence was lifted and

a man crawled under in 0.14 minute. Then, a more dramatic test was

set up. Two men started from a point 30' away from F2 and, using the

2" X 4" timber to lift the bottom of the fence, one crawled under and

then pulled the 2" X 4" inside and lifted the fence for the second man. With both men inside the enclosure, they ran the 20' to Fl and repeated

the process. Then they ran to a point 50' beyond Fl. The total time

for the two men to run 100' and crawl under the two fences was 0.95

minute. The sequence of events is shown in figures 173, 174, 175, 176,

and 177.

144
YAV

F2 -71

Figure 179. Opening Produced by

Abrasive Wheel Saw; Test F2

10 -i

0.1

.01

001

I

Bib, » JUB 81 ^^^ *^^r. » "^^"^ "^

1,500

Frequency Hz

I 3,000

Figure 180. Multiple Sweeps of Vibrational

Disturbances Produced by

Abrasive Wheel Saw; Test F2

145
As in the case of Fl , it required cutting 13 wires to make the

necessary opening size in the fence fabric. With the No. 14 bolt

cutters, this took 0.27 minute. It took 0.79 minute with the vise grip

cutters, 0.39 minute with the linesman's pliers, and 0.59 minute using

a pair of 6" diagonal cutters. Vibrational disturbances from the

diagonal cutters at a distance of 6' are shown in figure 178.

The abrasive wheel saw was used to make a 21" long diagonal cut

and a 22" horizontal cut and produce the opening shown in figure 179.

in 0.44 minute. Multiple sweeps of the vibrational disturbances are shown in figure 180. These data were obtained with the transducer only

two to three feet from the attack location.

146
V v \\ \ \ \WW

S3?

Figure 181. 25" High Opening Produced

in Lighter Gauge Material;

Test F3

W

Figure 182. Appearance of Fabric after Dropping ; Test F3

147
Figure 183. Climbing Fence Bare-handed;

Test F3

*$$* „<i&i^

i & '*/A

Figure 184. Pulling Down Fabric from

Top Tension Wire in

Preparation for Climb-over.

Test F3

148
10 "I

0.1 -

.01 -

001

Figure 185.

$.500

Frequency Hz

Vibrational Disturbances

Produced by Vise Grip Cutters;

Test F3

.00 t

.000 !-|

iHH

Figure 186.

1,500

Frequency Hz

Vibrational Disturbances

Produced by 6" Diagonal

Cutters; Test F3

1

• 3,000

149
3 V

$

«*K~is«„, ]

Figure 187. Completed Opening;

Test F3

150
7.2.3 F3 F3 was 40 mm mesh with 1 . 8 mm wire, vinyl-coated.

Here, because of the lighter gauge material, it was possible to

grasp the fabric and tear it clear of the wire ties fastening it to the

bottom tension wire and make the 25" high opening shown in figure 181.

It took 0.12 minute to make this opening and for one man to crawl

through. Note in figure 182 that when the fabric is released afterwards

the damage is not highly obvious and could easily be missed by a casual

inspection of the fencing.

As shown in figure 183, climbing the fence was accomplished barehanded in 0.07 minute.

As shown in figure 184, the fabric could be readily pulled down

from the top tension wire and this with crawl-over took only 0.10

minute.

Because the bottom tension wire was close to the ground, only 12

wires had to be cut to make the required opening size in this fabric.

This required 0.32 minute using the No. 14 bolt cutters and 0.39 minute

using the vise grip cutters. The vibrational disturbances from this were barely above the background with the transducer 9' from the

attack point; see figure 185.

Using the lineman's pliers, the 12 cuts took 0.33 minute, and

using the 6" diagonal cutters, it took 0.21 minute. Vibrational

disturbances are shown in figure 186 with increased gain.

As a final test on this fabric, one of the wires was cut near

the bottom of the fence. Then the cut end was gripped with pliers and

pulled. The wire which is pulled visibly straightens for about half

the height of the fence. It was cut again at the highest point where

it can be readily identified and then was readily stripped clear out of

the fabric. The process was repeated on the top half of the fence

and produces a full opening, as shown in figure 187. This procedure

took 0.58 minute. It is more easily accomplished with vinyl-coated

wire than galvanized as the vinyl coating reduces friction making it

possible to remove the wire in longer sections.

151
10

0.1 -

.01

001

£«

T

1,500

Frequency Hz

I 3,000

Figure 188, Vibrational Disturbances from 10'

Resulting from Fence Lifting and

Man Crawling Under; Test F4

Figure 189. Climb Over Top of Fence;

Test F4

152
• 1

001

I li

hk ' #WM

1,500

Frequency Hz

Figure 190. Vibrational Disturbances

Resulting from Bolt Cutter

Attacks; Test F4

1 3,000

001

1,500

Frequency Hz

3,000

Figure 191. Vibrational Disturbances

Resulting from Vise Grip

Cutter Attacks; Test F4

153
10

0.1

.01

001

1,500 3,000

Frequency Hz

Figure 192. Vibrational Disturbances

Resulting from Linesman's

Pliers Attacks; Test F4

•^

?-

4 •»

Figure 193. Metric Fence Pole Broken Off

by Two-man Attack; Test F4

154
1

Figure 194. Details, Metric Fabric

Attachment to Gate Frame;

Test F4

Figure 195. Pulling Metal Fabric

Away from Frame; Test F4

155
7.2. 4 F4_ This section of fabric was made from 2.65 mm wires, vinylcoated, 50 mm mesh.

With the 2" X 4" timber, the bottom of the fence was easily

lifted a foot above ground, and this, together with a man crawing under,

took 0.08 minute. Vibrational disturbances as observed at a distance

of 10' are shown in figure 188.

Climbing over the top of the fence, figure 189, took only 0.07

minute, and, like F3, the fabric could be pulled away from the top

tension wire making an opening to crawl over in only 0.12 minute.

Only 11 wires had to be cut on this mesh to make an opening of

the required minimum size. Using the No. 14 bolt cutters, this took

0.40 minute; with the vise grip cutters, it took 0.47 minute; with the

linesman's pliers, it took only 0.28 minute, and the 6" diagonal pliers

could not cope with the wire size. Vibrational disturbances from the

bolt cutters are shown in figure 190, from the vise grip cutters in

figure 191, and the linesman's pliers in figure 192. All were observed

with the transducer mounted 4' from the attack location.

Because the metric gauge poles were obviously less rigid than the

heavy wall pipe used for fence sections Fl and F2, it was decided to see whether they could withstand a two-man attack. The tension wires

were cut at an intermediate post as were the tie wires fastening the

fabric to the post. Then two men pushed hard and the pole broke just

above the surface of the concrete in which it was embedded. The result

is shown in figure 193. The total time required was 0.71 minute.

The metric gate was constructed with the F4 fabric which was attached to the gate frame by rather light tie wires which can be seen

in figure 194. These were cut in five places and the fabric was pulled

away from the frame as shown in figure 195 producing a half-oval opening that measured 12" X 29" in 0.34 minute.

156
Figure 196. Timber Lift and Crawl Under;

Test F5

Figure 197. Climb Over Top; Test F5

157
7.2.5 F5 This section of fencing was constructed of 2.0 mm wire, 40 mm mesh, galvanized wire. The fabric had a rather soft, spongy feel

when one pushed against it by hand and vibration disturbances were not

observed above the ambient background from any of the cutting operations

with the transducer located only 4' from the attack area. The 2" X 4" timber lift and crawl under, figure 196, took 0.12

minute and a climb over the top took 0.05 minute, figure 197.

Thirteen mesh wires had to be cut to make the necessary opening

size. These took 0.27 minute using the No. 14 bolt cutters, 0.25

minute using the vise grip cutters, 0.18 minute using the linesman's

pliers and 0.29 minute using 4" diagonal pliers.

Cutting and pulling out a wire to unweave the fence fabric was

done in a manner similar to that on F3, Because of increased friction,

it was necessary to cut the wire in five places and pull it out in

shorter sections. This attack required 1.08 minutes, but produced a complete separation in the fabric.

Finally, another intermediate pole was broken off using a repetition of the attack technique employed on F4. The time required

was 0.57 minute and failure was at the same location as on the earlier

test.

158
Figure 198. Lift Bottom Tension Wire

and Crawl Through; Test F6

0.1 -

.01 -

001 T

1,500

Frequency Hz

1

3,000

Figure 199. Vibrational Disturbances Produced

by Lifting Wire and Crawling ThroughTest F6

159
10

0.1

.01

001

r : :

:"

I II 11 I "" "" ViTCEr; I;

1,500

Frequency Hz

3,000

Figure 200. Vibrational Disturbances Produced

by Bolt Cutter Attacks ; Test F6

001

««

1,500

Frequency Hz

3,000

Figure 201. Vibrational Disturbances Produced

by Vise Grip Cutter Attacks; Test F6

160
7.2.6 F6_ The fabric in section F6 was 2.26 mm galvanized wire, 50 mm

mesh, and the three coil pyramid of concertina wire was located just

inside the middle of this section of fencing.

In order to clear the concertina wire, the location selected for

the lift and crawl under attack was between the bottom of a diagonal

corner bracing pole and the nearby intermediate pole. Despite this

short span, it was still possible to lift the bottom tension wire and

fabric enough for a man to crawl through as shown in figure 198. The

time required was 0.19 minute and vibrational disturbances produced by

the activity are shown in figure 199. Here, the transducer was at a distance of approximately 14'.

Climbing over the fence required 0.04 minute.

Cutting the fence to make a man-passable opening required

cutting 12 wires. This took 0.20 minute using the No. 14 bolt cutters

and, as observed at a distance of 12', the vibrational disturbances

were as shown in figure 200. The vise grip cutters took 0.22 minute

and produced slightly less disturbance, as shown in figure 201.

Linesman's cutters took 0.17 minute and produced comparable disturbances

as shown in figure 202, The 6" diagonal pliers took 0.22 minute and

produced similar vibrational disturbances.

JO Hh

I —

0.1

.01

001

:.... %iX m h

4 1' -

1,500

, 3,000

Frequency Hz

Figure 202. Vibrational Disturbances Produced

by Linesman's Cutters Attacks; Test F6

161
50 1

1 -

0.1

.0!

001 T

1,500

Frequency Hz —

1

3,000

Figure 203, Multiple Sweep Trace of

Vibrational Disturbances

Produced by Wire Cutting . Test F6

Figure 204. Concertina Wire Spread Apart,

Hooked to Other Strands Resulting

in Crawl Through Space; Test F6

162
Figure 205. Climb to Throw Heavy

Tarpaulin over Concertina

Wire • Test F6

Figure 206 On Top of Fence

Getting Ready

to Jump ; Test F6

163
Figure 207. Leap Clearing Concertina Wire

Using Tarpaulin as Safety Factor;

Test F6

to -

1

1 —jMSVW

TM i «^ WJM

o.t — iTI

.01 -

l-f-'

7" 7$fi ri

001 -

i 1,500

Frequency Hz

3,000

Figure 208. Vibrational Disturbances Produced

During Climb with Transducer 4' Away;

Test F6

164
Next, a penetration was made through the fence and through the

concertina wire immediately behind the fence. First, fabric wires were

cut, using linesman's pliers along a diagonal from the ground to a point about 42" high. This provided an opening large enough to manipulate the concertina wire. The three lower tension wires were also cut

and the ends pulled aside. A multiple sweep trace of some of the

vibrational disturbances produced by the wire cutting is shown in figure

203. Then the strands of concertina wire were spread apart and hooked to

other strands so as to provide an open area through the bottom two coils

which was large enough for a man to crawl through, as shown in figure

204. The hooks which were used were made from three- inch lengths of

No. 9 gauge wire which had short reverse bends at each end. After the

concertina wire had been hooked apart, two men crawled through the

opening.

The total time required for this penetration was 4.14 minutes;

however, neither operator had any prior experience with this particular

technique so they had been specifically instructed to proceed cautiously.

Although it was not done in this test, the hooks could have been

removed and the concertina wire would have sprung back into its original

position leaving no evidence that it had been traversed. Cutting the

concertina wire would provide much more rapid passage but would leave

clear evidence of the passage.

Figures 205, 206, and 207 demonstrate yet another technique

which permits a two-man team to get one man inside the fence and

concertina wire in 0.53 minute. One man provides support for the second

who climbs up and throws a heavy folded tarpaulin across the top of the

concertina wire. He then climbs to the top of the fence and leaps

across the concertina. In this instance, the tarpaulin simply provided

a safety factor as the leap cleared the concertina wire entirely.

Figure 208 shows vibrational disturbances during the climbing with tfc transducer at a distance of about four feet.

165
10

I -

o.t

.01 -

001

1,500

Frequency Hz

Figure 209. Vibrational Disturbances

from Bolt Cutters on F7

;

Test F7

_~J.

Figure 210. Cutting Metric Intermediate Post near Ground with Abrasive Wheel Saw;

Test F7

166
o n

I -

0.1

.01 -

001

kisssb

1,500

Frequency Hz —

1

3,000

Figure 211. Vibrational Disturbances Produced

by Abrasive Wheel Saw Attacks;

Test F7

Figure 212. Comparison of U.S. and Metric Posts;

Test F7

167
7.2.7 _F7 This section of fence was constructed of fabric made of 2.65 mm galvanized wire with 60 mm mesh.

The lift and crawl test was not performed on this section because

the tension wires had been cut in the adjacent section, F6.

Cutting a man-passable opening required severing 12 wires on

this mesh. The vibration transducer was located approximately 8' from

the attack point and disturbances produced by the 0.20 minute work with

the No. 14 bolt cutters are shown in figure 209. The vise grip cutters

took 0.19 minute, the lineman's pliers 0.20 minute, and the 6" diagonal

pliers 0.14 minute. The vibrational disturbances which they produced

were not significantly different than those shown for the bolt cutters.

The gasoline-powered abrasive wheel saw was used to cut off one

of the metric intermediate posts near the ground, as shown in figure

210. This took 0.16 minute and produced vibrational disturbances,

as shown in figure 211, with the transducer at a distance of 10' from

the post. Figure 212 shows the comparative cross sections of the two

types of intermediate fence posts used.

The abrasive wheel saw was also used to cut the full height of

the fabric, as shown in figure 213. This required 0.11 minutes.

Figure 213. Cutting Full Height of Fabric

with Abrasive Wheel Saw; Test F7

168
7. 3 Discussion of Fence Test Results

The test results indicate that climbing over an unelectrified

fence is probably the most effective method of penetration by a single

man, and the same technique* or lifting up and crawling under the fence

can be used by a two- or more-man team. The lift and crawl penetration

permits the intruders to maintain a lower profile and reduces the

chance of visible detection. Both methods leave little or no residual

evidence that a penetration has occurred.

Penetration can be made quickly by a single intruder by cutting

from 11 to 14 wires using a variety of tools, but this leaves an opening that is obvious in even a cursory inspection.

Table 4 summarizes the times in minutes observed on the various

fence types for these modes of attack.

Table 4. Summary of Selected Penetration Times

Attack Fl F2 F3 F4 F5 F6 F7

1

J. . Lift and crawl under 0.10 0.14 0.12 .08 0.12 0.19 —

2. Climb, with tarp 0.15

with gloves .06, .08 — 0.07 0.07 0.05 .04 —

3. Cut with:

bolt cutters 0.32 0.27 0.32 0.40 0.27 0.20 0.20

fence tool 0.76

vise grips No 0.79 0.39 0.47 0.25 0.22 0.19

linesman'

s

pliers No 0.39 0.33 0.28 0.18 0.17 0.20

6" diagonal

pliers No 0.59 0.21 No 0.22 0.14

4" diagonal

pliers No — — 0.29 — —

abrasive wheel

saw

- .

.17, .26

. . i

0.44 .13, 0.1

-

In the table, a "No" indicates that the tool could not be used; a

" —

indicates that test was not made.

In the lift and crawl under- tests, the time variations do not

appear to be strongly influenced by fence type. The span length over which the tension wire or tension messenger may be stretched is

probably a more significant factor and Was certainly responsible for

the high value observed for F6.

169
In the climb over tests, the 0.06 and 0.08 minute climbs were made as the last two climbs in the series. There is some reason to believe

that the sequentially decreasing times for F3 through F6 reflect

improvements gained through experience. If this is true, then the

presence of the barbed wire outrigger adds a few hundredths of a minute

to the climbing resistance.

Small, No. 14 bolt cutters or a combination fencing tool are adequate to handle No. 9 gauge wire or smaller. Eight inch linesman's

pliers are adequate for No. 11 gauge wire and are a little faster for < the smaller gauges.

7. 4 Conclusions

The test results indicate that the deterrent influence of unelectrified fencing of the types tested is largely psychological rather

than physical. Thus, it would appear appropriate to select materials

on the basis of avoiding the outward appearance of flimsiness and at

the same time having enough real strength and durability to promise an adequate service life.

Meshes of the size used in F3, F5 and F6 have the visible

appearance of flimsiness which should detract from their psychological

deterrent value. F2 and F4 give the visual impression that they are more sturdy than they are in fact because the vinyl coating adds

considerably more thickness to the wire than galvanizing. Another

advantage to the green vinyl coating is the improved visibility which

it provides by eliminating the glare and reflection which galvanized

mesh produces under some lighting conditions.

Outriggers carrying barbed wire are considered quite cost

effective. Their incremental cost per lineal foot is relatively small

but they make a fence appear much more formidable. The outward

sloping configuration is preferred.

The thin-walled, vinyl-coated tubing used in the metric fence posts

gives a visual appearance of strength, but this is immediately dispelled

if the post is shaken near the top. The standard pipe sizes used in the

construction of Fl and F2 are probably a better choice purely on the

grounds of better service life expectancy.

170
In summary, it is believed that an unelectrif ied fence can be

penetrated so quickly by such a variety of means that the material

selection will be most cost effective if based on service life

considerations and an outward appearance of integrity. Vinyl-coated

wire of 2.65 mm (No. 11 gauge) or larger and galvanzed wire of No. 9

gauge or larger creates this appearance in a mesh fabric. Mesh size

in the ranges tested does not greatly influence the number of wires

which have to be cut to make a minimum-sized, man-passable opening;

however, mesh sizes greater than about 50 mm or two inches begin to

look more open and should probably be avoided on this basis.

171
APPENDIX

During the course of this and three prior barrier penetration test

series, sufficient, data has been collected to permit certain general

comments to be expressed regarding the capabilities and limitations of some of the tools which have been used and the observed range of their

performance in selected materials.

The sledgehammer is the most important single tool in forcible

barrier penetration. It is used alone or as an adjunct to other

tooling in attacks on a great majority of materials. In fact, when

the detailed structural composition of a barrier is unknown, it is

usually worthwhile to initiate the attack for a minute or so with a sledgehammer. In the frequent cases where major damage results from

the first minute of sledgehammering, continuation of that attack will

usually result in a faster penetration than could be made using other

tooling. The most effective size sledgehammer appears to be in the

6- to 12—pound range with the 10-pound size being preferred

by most operators in good physical condition and weighing in the

vicinity of 200 pounds. A smaller operator may be more effective with

the 6- or 8-pound sledgehammer. The most effective situation

occurs when the product of the mass of the hammer and its velocity

squared is maximized. Most operators do not appear to be able to

accelerate a 16- or 20-pound hammer to velocities high enough to make

2 a major difference in the MV product. Such increase as may be attained

is offset by increased operator fatigue causing more rest requirements

and a slower stroke rate. In sustained, multi-operator attacks using a 16-pound sledge, an average time of 1.68 seconds per blow has been

observed compared to 1.58 seconds per blow for a 10-pound sledgehammer.

For attacks involving only a short period of effort, times as short

as 1.2 seconds per blow have been observed using the 10-pound hammer.

For attacks which require working times on the order of 10 to 15

minutes, fresh operators will usually require about 90 seconds rest for

each 30-second stint of hammering and four operators can usually maintain an excellent ratio of working to elapsed time. For attacks of

longer duration, five or more operators may have to be employed to

maintain this ratio.

172
Other useful impact tools are the cutting maul and the bar. The

cutting maul is simply a sledgehammer with one side of the head formed

into a wedge shape with a cutting edge. The bar is generally pointed

at one end and equipped with a weighted wedge-shaped cutting edge at

the other end. It is very useful in working in deeper openings which

are not readily accessible to the sledgehammer. The 26-pound size

appears to be a good selection and can be used at a speed of about

1.4 seconds per blow.

At the low end of the utility spectrum for impactive tools is the

battering ram, at least in the 50-pound size commonly sold to fire and rescue units and designed for two-man, handheld operation. The

transverse steel bar handles transmit intense impact shocks back to

the hands of the operators when it is used against materials such as concrete, and it is less effective than a sledgehammer when used against even relatively fragile materials such as hollow concrete blocks.

The abrasive wheel saw can be used to cut virtually any of the

materials likely to be encountered in structural barriers including

concrete, masonry, steel, wood and plastic. Its depth of cut is

limited by wheel size and is normally in the range of 2 to 5 inches.

Cutting rates in concrete are on the order of 7 to 14 seconds per

lineal inch for a 3-inch depth of cut. Because of the depth of cut

limitations, it is usually most effective against relatively thin

sections, particularly when these involve several different types of

laminated materials such as, for example, a wood, steel, wood sandwich. It is very fast and effective against discontinuous metal

materials of modest gauge, such as expanded metal, chain link fencing, or ferro-cement reinforcing wires, provided these are accessible to the

working edge of the wheel. Where access is limited, or where continuous

and thicker metals are encountered, one of the several types of flame

cutting tools will usually be faster.

The rotohammer is indispensable, along with the sledgehammer

and suitable punches, for making rapid, explosive free penetrations

in reinforced concrete. This is accomplished by drilling a suitable

pattern of holes partially through the concrete and spalling off the

173
interior using punches driven by the sledgehammer. This technique

exploits the lower tensile strength of concrete as compared to its

compressive strength. After one or more iterations of this process

using successively shallower holes, the thickness of the barrier is

reduced to the point that a small central area can be broken completely

through with the sledgehammer .Then, a tapered punch driven into each

of the peripheral holes in turn will spall material into this central

breakthrough area and enlarge the opening. The fastest penetration

results from a judicious choice of hole pattern, including size of

holes and depth (s), so as to minimize the total time required for both

drilling and spalling. The optimum pattern depends somewhat upon the

characteristics of the concrete. It is difficult to spall out the

bottom of a hole in fibrous concrete having a remaining thickness

greater than about 2 or 2-1/2 inches. Ordinary concrete, with its

lower tensile strength, can be spalled when the thickness is on the

order of an inch greater. An empirical rule-of-thumb is to strive for

a hole depth such that the residual thickness can be spalled out with

an average of about 10 to 15 blows from the sledgehammer. If the

bottom spalls out of the holes after only two or three blows, it is an indication that they are too deep and that more material could have

been spalled out using a shallower hole. If an average of more than

about 20 blows are required, the holes should probably be drilled a little deeper. Drilling rates in concrete are a function of drill

size and material. In a given material, the drilling rate has been

observed to be inversely proportional to the volume of material

removed for drill sizes of one inch or less in diameter. Thus, it

only takes about 56 percent as much time to drill a 3/4-inch hole as

it does for a one-inch hole. Drilling times for one-inch holes have

been observed over the range from 3.5 to 10.7 seconds per inch of

depth depending upon the type of concrete. Lightweight concretes are

at the lower end of the range, typically 3.5 to 5 seconds per inch.

Regular concretes span the range from about 6 to over 10 seconds per

inch. Usually the specimens in the 6-second region have been mixed

with small size aggregate, 3/8- to 3/4-inch, and those at the upper

end have large and very hard aggregate. The fibrous concretes which

174
have been tested employed 3/8-inch or less aggregate but showed drilling times of about 7 seconds per inch.

Using one-inch diameter holes and punches to make a penetration,

the punches are seldom bent during the spalling operation, but an excessive amount of time is required for drilling. Faster penetrations

can be made, but with a high punch mortality rate, using a 3/4-inch

hole size. This does not add significantly to the logistics problem

since punches are usually driven through the hole when the spall occurs

and would not be recoverable after a single use until the penetration

was completed.

The burning bar can be used to melt through concrete, but, since

it does not afford a ready means of ascertaining hole depth, it is not

easily substituted for the rotohammer in a drill and spall type of

attack. Melting rates appear to be fairly well clustered in the range

of about 5 to 8 seconds per inch and do not seem to be affected much by

the type of concrete. There is fairly constant bar consumption in

concrete at rates of about 1.0 to 1.25 seconds per inch using oxygen

pressures of 160 to 200 p.s.i.. The burning bar is most useful in

cutting steel. Typical average cutting times per lineal inch are 2.3

seconds for 1/4-inch thickness, 1.3 seconds for 1/8-inch thickness,

and 2.28 seconds for 3/16-inch thick expanded steel. Here operation

is at lower oxygen pressure, typically 75 to 100 p.s.i. and bar

consumption is on the order of 2 seconds per inch.

Three other types of cutting torches appear to be quite comparable

in cutting times as measured on 1/4-inch thick mild steel plate. These

are the oxygen acetylene torch with No. 5 tip, the oxygen-fed electric

arc, and the portable rocket cutting torch. All showed times of between.

12 and 13 seconds per lineal inch.

175
Hand-operated cutting tools ranging in size from 3/8-inch

bolt cutters down to 4-inch diagonal cutters can be operated at an average time of from 3.0 to 0.70 seconds per cut. The smaller tools

designed for single-handed operation were generally operated in the

range of 1.0 to 1.5 seconds per cut. Not unexpectedly, the fastest

operation occurs when using the smallest tool which can comfortably

make the necessary cut. For cutting steel fence fabric wire of No.

11 gauge or smaller, 8- inch linesman's pliers are most effective. For

No. 9 gauge, the small No. 14 bolt cutters are preferable. These are quite effective on rods up to about 1/4-inch in diameter. For larger

rod sizes, correspondingly larger sizes of bolt cutters will be more

effective.

176
ACKNOWLEDGMENT

The assistance and active participation of many individuals in

several organizations is acknowledged. Their advice, counsel and

timely support were vital to the successful completion of the project.

Mr. Frank C. Veirs and Spc. P. Schmidt of the U. S. Army

Intelligence Materiel Development Office provided most of the attack

tooling and key elements of the data instrumentation equipment and

assisted both in making penetrations and in data collection. Tom Noe

offered helpful suggestions regarding the design of some of the

experimental panels and assisted in data collection during the tests.

R. Blackmon, Headquarters, Naval Security Group, made arrangements for

the essential support of Cpl. R. C. White and Lance Cpl. W. J. Moore,

U.S.M.C., who accomplished most of the actual penetrations.

Vibrational disturbance data acquisition was handled by R. Koyanagi

and R. C. Meadors of the National Bureau of Standards Vibration

Section. They also provided key assistance in test timing and data

recording. Motion picture footage of the test series was provided by

J. Sonnichsen and J. D. Watkins of the N.B.S. Photographic Laboratory,

The tests were sponsored by Defense Nuclear Agency under the

direction of Marvin C. Beasley. His many helpful suggestions and

active personal involvement in all phases of the activities are gratefully acknowledged.

177
SI Conversion Units

In view of the present accepted practice in this country for building

technology, common US units of measurement have been used throughout

this paper. In recognition of the position of the United States as a signatory to the General Conference on Weights and Measures, which gave

official status to the metric SI system of units in 1960, assistance is

given to the reader interested in making use of the coherent system of

SI units by giving conversion factors applicable to US units used in

this paper.

Length

1 in = 0.0254 meter (exactly)

1 ft = 0.3048 meter (exactly)

Force

1 lb (lbf) = 4.448 Newton (N)

1 kip = 4448 Newton

Pressure

2 1 psi = 6895 N/m

1 ksi = 6.895 x 10 N/m

Mass

1 lb = 0.453 592 37 kilogram (kg)

178
NBS-U4A (REV. 7-73I

U.S. OEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. PI B] H A I [ON OR Kl- POR r NO. NBS TN-837

2. Gov 't Access ion No.

3. Recipient s Accession Nc

4. riTLE AND SUBTI I I I

BARRIER PENETRATION TESTS

5. Publication Date June 1974

6. Performing Organization ' ode 650.01

7. ai rnoRisi R. T. Moore8. Performing Organ. Report No.

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. Project 6509419

11. Contract/Grant No. IACRO DNA EO 72-201,

73-406, 74-408

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

Defense Nuclear Agency (DNA)

Washington, D. C. 20305

13. Type of Report & Period Covered ^

Tech Nofce

14. Sponsoring Agency Code DNA

15. SUPPLEMENTARY NOTES

Library of Congress Card No. 74-600107

16. ABSTRACT (A 200-word or less (actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.) Sixteen structural barrier panels were tested to determine their resistance to

forcible penetration through the use of readily available tooling. Thirteen of these

represented experimental techniques to reinforce an existing structural barrier of low

penetration resistance; the other three were designs which would be most appropriate

to consider as replacement barriers. Minimum man-passable sized openings were made in

the barriers in working times which averaged 7.85 minutes and ranged from 1.52 to 25.56

minutes. One of the replacement and two of the reinforcing designs showed superior

cost-effectiveness

Seven woven, wire-mesh security fence specimens were also tested for their

intrusion deterrence capability. The test results indicate that the deterrent

influence of unelectrified fences of the type tested is largely psychological rather

than physical. All of the specimens could be penetrated in 0.14 minutes or less.

Samples of the acoustical and vibrational data produced during the penetration

tests add to the growing body of data which are expected to be useful in the design and

selection of electronic intrusion alarm equipments.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Barrier penetration; intrusion detection; intrusion resistance; physical security

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