A111D3 TBTTbS

NBSIR 82-2465 (A)

Investigation of the Kansas City

Hyatt Regency Walkways Collapse

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, DC 20234

Feburary 1 982

100

.056

82-2465A

1982

C.2

)EPARTMENT OF COMMERCE

nIAL bureau of STANDARDS

NBSIR 82-2465 (A)

INVESTIGATION OF THE KANSAS CITY

HYATT REGENCY WALKWAYS COLLAPSE

A

R. D. Marshall

E. 0. Pfrang

E. V. Leyendecker

K. A. Woodward

Center for Building Technology

National Engineering Laboratory

R. P. Reed

M. B. Kasen

T. R. Shives

Center for Materials Science

National Measurement Laboratory

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Washington, DC 20234

February 1 982

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director
1
ABSTRACT

An investigation into the collapse of two suspended walkways within the atrium

area of the Hyatt Regency Hotel in Kansas City, Mo., is presented in this

report. The investigation included on-site inspections, laboratory tests and

analytical studies.

Three suspended walkways spanned the atrium at the second, third, and fourth

floor levels. The second floor walkway was suspended from the fourth floor

walkway which was directly above it. In turn, this fourth floor walkway was suspended from the atrium roof framing by a set of six hanger rods. The third

floor walkway was offset from the other two and was independently suspended

from the roof framing by another set of hanger rods. In the collapse, the

second and fourth floor walkways fell to the atrium floor with the fourth

floor walkway coming to rest on top of the lower walkway.

Based on the results of this investigation, it is concluded that the most

probable cause of failure was Insufficient load capacity of the box beam-hanger

rod connections. Observed distortions of structural components strongly suggest

that the failure of the walkway system initiated in the box beam-hanger rod

connection on the east end of the fourth floor walkway’s middle box beam.

Two factors contributed to the collapse: inadequacy of the original design for

the box beam-hanger rod connection which was identical for all three walkways,

and a change in hanger rod arrangement during construction that essentially

doubled the load on the box beam-hanger rod connections at the fourth floor

walkway. As originally approved for construction, the contract drawings called

for a set of continuous hanger rods which would attach to the roof framing and

pass through the fourth floor box beams and on through the second floor box

beams. As actually constructed, two sets of hanger rods were used, one set

extending from the fourth floor box beams to the roof framing and another set

from the second floor box beams to the fourth floor box beams.

Based on measured weights of damaged walkway spans and on a videotape showing

occupancy of the second floor walkway just before the collapse, it is concluded

that the maximum load on a fourth floor box beam-hanger rod connection at the

time of collapse was only 31 percent of the ultimate capacity expected of a connection designed under the Kansas City Building Code. It is also concluded

that had the original hanger rod arrangement not been changed, the ultimate

capacity would have been approximately 60 percent of that expected under the

Kansas City Building Code. With this change in hanger rod arrangement, the

ultimate capacity of the walkways was so significantly reduced that, from the

day of construction, they had only minimal capacity to resist their own weight

and had virtually no capacity to resist additional loads Imposed by people.

Supplementary material is contained in an appendix to this report and

published as NBSIR 82-2465A.

Key Words: building; collapse; connection; construction; failure; steel;

walkway

iii
IV

Sections A6.10 - A6.11
Figure A6.10-1 In-plane load vs displacement curves for specimens A1 and A2

Figure A6.10-2 In-plane load vs displacement curve for specimens B1
Figure A6.10-3 In-plane load vs displacement curve for specimens B2

Figure A6.10-4 In-plane load vs displacement curve for specimens B3

A-4
Figure A6.10 5 In plane load vs displacement curves for specimens Cl and C3

Figure A6.10 6 In plane load vs displacement curves for specimens C2 and C4
SPECIMEN D1

Figure A6.10-7 In-plane load vs displacement curve for specimens Dl

.

SPECIMENS El AND £2

Figure A6.10-8 In-plane load vs displacement curves for specimens El and E2
Figure A6.10-9 In-plane load vs displacement curves for specimens FI and F2

Figure A6. 10-10 In-plane load vs displacement curves for specimens G1 and G2
Figure A6. 10-11 In-plane load vs displacement curve for specimens HI.

Figure A6. 10-12 In-plane load vs displacement curves for specimens II and 12.

A-8
Figure A6. 10-13 In-plane load vs displacement curves for specimens J1 and J2.

Figure A6. 10-14 In-plane load vs displacement curves for specimens K1 and K2

AFigure A6.10-15 In-plane load vs displacement curves for specimens K3 and K6.

Figure A6. 10-16 In-plane load vs displacement curves for specimens K4 and K5.

A-10
Figure A6. 10-17 In-plane load vs displacement curves for specimens LSI and LS2

In plane load vs displacement curves for specimens Ml and M2.

A-11

Figure A6. 10-18
SPECiriENS N1 AND N3

Figure A6.10-19 In-plane load vs displacement curves for specimens N1 and N2

Figure A6. 10-20 In-plane load vs displacement curves for specimens N3,

and N5. A-12

N4,
Figure A6. 10-21 In-plane load vs displacement curve for specimens N6.

Figure A6. 10-22 In-plane load vs displacement curves for specimens 01 and 02.

A-13
SPECIflENS PI AND PE

Figure A6. 10-23 In-plane load vs displacement curves for specimens PI and P2.

Figure A6.10 24 In-plane load vs displacement curves for specimens Rl and R2

.

A-14
Figure A6. 10-25 In-plane load vs displacement curves for specimens SI, S2, S3,

and S4.

Figure A6. 10-26 In-plane load vs displacement curves for specimens T1 , T2

and T3.

A-15
Figure A6. 10-27 In-plane load vs displacement curves for specimens U1 and U2

Figure A6. 10-28 In-plane load vs displacement curves for specimens VI and V2

A-16
Figure A6. 10-29 In-plane load vs displacement curves for specimens W1 , W2

and W3.

Figure A6.10 30 In plane load vs displacement curves for specimens XI and X2

A-17
Figure A6.11 1 In-plane load vs deflection curves for specimens LI and L2

.

Figure A6.11 2 In plane load vs deflection curves for specimens L3, L4 , L5

L6, and L7 „
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A-19
A7. NBS MATERIALS TESTING PROGRAM

A7.2 INITIAL INSPECTION

PJ .li.2 Radiography

Radiographs of portions of box beam 9M used in the analysis described in

section 7 of the report are produced in figure A7.2.2-1.

A7.3 MECHANICAL PROPERTIES OF STRUCTURAL STEEL AND WELDMENTS

A7.3.1 NBS Channel Specimens

Load-strain plots for tensile tests performed on NBS channel specimens are given in figures A7.3.1-1 to A7.3.1-3.

A7.3.2 Walkway Box Beams

Locations from which base metal tensile specimens were removed from box beams

9U, 8L and 9M are illustrated in figures A7.3.2-1 through A7.3.2-3. Loadstrain plots for the tensile tests performed on walkway box beam specimens

appear in figures A7.3.2-4 through A7.3.2-9.

A7.3.3 Walkway Hanger Rods

Locations from which tensile specimens were removed from hanger rods NBS 5A and

5B are illustrated in figure A7.3.3-1. Load-strain plots for the walkway hanger

rod tests appear in figure A7.3.3-2.

A7.3.4 Walkway Box Beam Longitudinal Welds

Locations from which tensile specimens were removed from box beams 9U, 8L and

9M are illustrated in figures A7.3.2-1 through A7.3.2-3.

A7.4 METALLOGRAPHY AND HARDNESS MEASUREMENTS

A7.4.1 Box Beam Weldments

A "U" shaped transverse section through NBS weldment IC was examined for

microstructure and hardness. Weldment IC was welded by the GMAW process using

a mild steel electrode. The section examined, shown at low magnification in

figure A7.4.1-1, Included the welded flange region and part of the web region

of each box beam channel. The section was metallographically polished and

chemically etched to reveal the microstructure. The region of this section

containing the weld is shown at higher magnification in figure A7.4.1-2. In

this figure, the light region in the center represents weld metal; the darker

regions on either side of the weld are the heat affected zones associated with

the weld. The light regions at both sides of the figure, adjacent to the heat

affected zones, are flange base metal.

A-20
Knoop dlcrohardness measurements at a load of 500 grams force (HK500 ) were made

across the weld metal, across one of the heat affected zones, and into the base

material on this same transverse section through NBS weldment IC. The indentations produced by the microhardness tests appear as a line of small, dark,

elongated marks in figure A7.4.1-2. Approximately equivalent Rockwell B (HRB)

hardness values, converted in accordance with ASTM E140-79 (Standard Hardness

Conversion Tables for Metals) [7.1], are reported along with the HK500 values.

A representative region of the weld metal appears in figure A7.4.1-3. The

microstructure consists primarily of bainite. Microhardness values based on

17 measurements average 205 HK500 (90.9 HRB) and range from 195 to 228 HK500

(88.5 to 95.5 HRB).

The transition region between the weld metal and the heat affected zone is

shown in figure A7.4.1-4. Nothing unusual was observed at the transition. The

microstructure within the heat affected zone is shown in figure A7.4.1-5. The

microstructure consists of ferrite, primarily as a network in prior austenite

grain boundaries, bainite, partially spheroidized carbides, and tempered martensite. Average hardness of the heat affected zone based on five measurements

is 202 HK500 (90.2 HRB) with a range of 196 to 206 HK500 (89 to 91 HRB).

Figure A7.4.1-6 shows the transition from the heat affected zone to the base

material of the box beam. Hardness in this region averages 173 HK5 Q 0 (83 HRB)

and the hardness range is 167 to 177 HK500 (81 to 84 HRB).

A region representative of the base material away from the heat affected zone

is shown in figure A7.4.1-7. The microstructure is relatively fine grained and

consists primarily of ferrite (light) and pearllte (dark) in a normalized condition. Within the base material, the average hardness is 152 HK5 QQ (75.4 HRB)

and the range is 139 to 161 HK500 (70 to 70.9 HRB).

Two transverse sections similar to that described in the previous section on the

NBS weldment were examined from each of the two box beam segments (9U and 8L)

and the full length box beam (9M) obtained from the walkway debris. The locations of these sections in the box beams are indicated in figures A7.3.2-1

through A7.3.2-3. Each "U" shaped transverse section included the bottom of

the beam (channel flanges and weld region) and parts of the web region of each

box beam channel. To facilitate handling during metallographic preparation,

parts of the channel web regions were removed from each section. The metallographic examination was concentrated in the remaining shorter "U” shaped sections, but hardness measurements were made both in the shortened sections and

in the pieces that had been removed. The sections were polished metallographically and chemically etched to reveal microstructure. Knoop microhardness

measurements at a load of 500 grams force (HK500 ) were taken in the weld, heat

affected zones, and adjacent base channel material of these sections. Rockwell

B (HRB) hardness measurements were taken in the flange and web regions of each

channel piece. Summaries of the hardness test results appear in tables A7.4.1-1

through A7.4.1-3 for sections from box beams 9U, 8L and 9M, respectively.

Approximately equivalent Rockwell B (HRB) hardness values, converted in

accordance with ASTM Standard E140-79, are reported along with the HK500 values.

A-21
The sections from box beam 9U (NBS 1), designated IBMl and 1BM2, are shown in

figures A7.4.1-8 and A7.4.1-10, respectively. These two sections were separated

by about 7 in (180 mm) as measured along the length of the beam. The weld

regions of sections IBMl and 1BM2 are shown at higher magnification in figures

A7.4.1-9 and A7.4.1-11, respectively. The depth of weld penetration is greater

in section 1BM2 than in section IBMl and there is some misalignment of the

channel flanges at the weld.

Representative regions of the weld metal from sections IBMl and 1BM2 are shown

in figures A7.4.1-12 and A7.4.1-13, respectively. In both cases, the microstructure appears to consist of bainite. A number of inclusions are evident in

section IBMl. The average hardness of the weld in section IBMl (95 HRB) is

slightly higher than in the weld of section 1BM2 (91 HRB) and the hardness

range in the weld of section IBMl is greater.

There were some patches of hard material at the transition region from the

weld material to the heat affected zone at both the north and south channels in

section IBMl. One such patch can be seen in figure A7.4.1-14. A similar region

is shown at higher magnification in figure A7.4.1-15. The microstructure in

this region appears to be fine-grained tempered martensite. Maximum hardness

measured in these patches was 336 HK 500 which is approximately equivalent to a Rockwell C hardness of 33. This value compares to a hardness of 241 HK5QQ

(98 HRB) in an adjacent location of the transition region.

Hard patches were not observed in the transition region from weld to heat

affected zone in section 1BM2. An area representative of this region in

section 1BM2 is shown in figure A7.4.1-16.

Regions representative of the heat affected zones (HAZ) of sections IBMl and

1BM2 are shown in figures A7.4.1-17 and A7.4.1-18, respectively. In both cases,

the microstructure appears to consist of ferrite, both as a network in prior

austenite grain boundaries and as needles, bainite, partially spheroidized

carbides, and tempered martensite. Hardness of the heat affected zones in

section IBMl is somewhat greater at the south channel than at the north. At

both heat affected zones, hardness decreased with distance from the weld.

Hardness values in the heat affected zones of section 1BM2 were similar for

both zones.

The transition regions from the heat affected zone to the base channel material

appeared similar for both sections. A region representative of the transition

zone in section 1BM2 is shown in figure A7.4.1-19.

Base material from both channel pieces appeared similar. A region representative

of section IBMl is shown in figure A7.4.1-20. The microstructure consists

primarily of ferrite (light) and pearllte (dark) in a normalized condition.

Rockwell B hardness measurements made on both sections indicated no significant

differences in hardness between the two channel pieces used to fabricate the

box beam. Regions of the channel adjacent to the heat affected zones and in

the web region about 0.6 to 1 in (15 to 25 mm) from the bottom of the beam were harder than elsewhere with HRB hardness averaging 81.5. The hardness of the

A-22
channel material elsewhere in the sections averaged 74.4 HRB for section IBMl

and 74.3 HRB for section 1BM2.

The transverse sections examined from box beam 8L (NBS 2), designated 2BM1 and

2BM2, are shown in figures A7.4.1-21 and A7.4.1-23, respectively. These sections were separated by about 7 1/2 in (190 mm) as measured along the length of

the beam. The regions of sections 2BM1 and 2BM2 containing the weld are shown

at higher magnification in figures A7.4.1-22 and A7.4.1-24, respectively. There

appears to be minor undercutting at the weld in section 2BM2 and the heat

affected zone is somewhat narrower than in section 2BM1 . In section 2BM1 there

is a void at the base of the weldment adjacent to the gap between the channel

flanges

Regions representative of the weld metal in sections 2BM1 and 2BM2 are shown in

figures A7.4.1-25 and A7.4.1-26, respectively. Overall, the microstructure in

both cases appeared similar and consisted primarily of bainite. Inclusions

are evident in both sections. The average hardness values for weld metal in

the two sections do not differ significantly.

The transition from weld to the heat affected zone for section 2BM1 is shown

in figure A7.4.1-27. There are no unusual features.

As was the case in section IBMl from box beam 9U, there were some hard spots at

the transition from weld to the heat affected zone in section 2BM2 on the south

side. The transition in section 2BM2 is shown in figure A7.4.1-28 at 200 magnifications. One of the hard regions is shown at much higher magnification (X1200)

in figure A7.4.1-29. The microstructure of this region appears to be tempered

martensite. The highest hardness value obtained in this region was 298 HK5 QQ

which is approximately equivalent to 28 Rockwell C. Away from the hard regions,

hardness averaged 247 HK5 QQ (99 HRB).

In the heat affected zones, the microstructure was similar in both sections

2BM1 and 2BM2. A representative region from section 2BM1 is shown in figure

A7.4.1-30. The microstructure appears to consist of ferrite, both as a network

in prior austenite grain boundaries and as needles, bainite, partially

spheroidized carbides and tempered martensite. Hardness was 5 to 6 HRB points

lower for the heat affected zones in section 2BM2 than in the weld metal. In

section 2 BM1 , hardness was similar for both weld metal and the heat affected

zone

The transition regions from the heat affected zones to base channel material

appeared similar for both sections. A region representative of this transition

in section 2BM1 is shown in figure A7.4.1-31. A region representative of the

base channel material in both sections is shown for section 2BM1 in figure

A7.4.1-32. The microstructure of the channel material consists primarily of

ferrite and pearlite in a normalized condition.

There were no significant differences in hardness between the two channel

sections. As in the case of the section from box beam 9U, the channel material

was somewhat harder adjacent to the heat affected zones and in the web about

0.6 to 1 in (15 to 25 mm) from the flange base than elsewhere.

A-23
The sections examined for microstructure and hardness from box beam 9M (NBS 3) are designated 3BM1 and 3BM2 and are shown in figures A7.4.1-33 and A7.4.1-35,

respectively. These two sections were separated by about 7 1/2 in (190 mm) as measured along the length of the beam. The weld regions of sections 3BM1 and

3BM2 are shown at higher magnification in figures A7.4.1-34 and A7.4.1-36,

respectively. The weld configuration differs considerably between the two

sections. In section 3BM1 , the heat affected zones penetrate to a point

slightly greater than half the flange thickness, whereas the heat affected

zones in section 3BM2 penetrate all the way through the flange.

Representative regions of the weld from sections 3BM1 and 3BM2 are shown in

figures A7.4.1-37 and A7.4.1-38, respectively. In both cases, the microstructure appears to consist primarily of bainite. More inclusions are evident in

section 3BM1 than in section 3BM2. The average hardness of the weld was essentially the same for both sections, being somewhat lower than that of the welds

at the sections from the other two walkway box beams.

Nothing unusual was observed at the transition from the weld to the heat

affected zones in either section. None of the harder regions found in the

transition regions of sections IBMl and 2BM2 were in evidence. A region representative of these transition regions in section 3BM2 is shown in figure

A7.4.1-39.

The microstructure and hardness of the heat affected zones in both section 3BM1

and 3BM2 were similar. In both cases, the microstructure consists of ferrite

both as a network in prior austenite grain boundaries and as needles, bainite,

partially spheroidized carbides and some tempered martensite. Hardness in the

heat affected zones was similar to that of the weld. A region representative

of the heat affected zone in section 3BM1 is shown in figure A7.4.1-40.

The transition from the heat affected zone to the base channel material appeared

similar in both sections. A region representative of the transition zone in

section 3BM2 is shown in figure A7.4.1-41.

The base material of both channel pieces of the box beam appeared similar in

microstructure in both sections 3BM1 and 3BM2. In both cases, the microstructure consists of ferrite and pearlite in a normalized condition. A region

representative of the channel material is shown in figure A7.4.1-42. Hardness

of both channels was also similar.

In summary, the walkway and NBS box beam structural steel weldment microstructure

and hardness are comparable and normal.

A7.4.2 Walkway Hanger Rods

Transverse and longitudinal sections from each of the walkway hanger rod

segments obtained from the debris (NBS 5A and 5B) were examined metallographically. The locations of these sections in the hanger rods are shown in

figure A7.3.3-1. A representative region showing the etched microstructure of

the transverse section from hanger rod NBS 5A is shown in figure A7.4.2-1. The

A-24
microstructure consists of ferrite (light) and pearlite (dark) in a reasonably

fine grained (ASTM grain size 9) normalized structure.

The representative microstructure of the transverse section from hanger rod

NBS 5B is shown in figure A7.4.2-2. The microstructure again consists of

ferrite (light) and pearlite (dark) in the normalized condition. This microstructure is coarser (ASTM grain size 7-1/2 to 8) than that of hanger rod NBS

5A, and there appears to be more pearlite present than in hanger rod NBS 5A.

Longitudinal sections through each hanger rod segment revealed the material of

both to be fully normalized with equiaxed grains. Regions representative of

the longitudinal microstructures are shown in figure A7.4.2-3 for rod segment

NBS 5A and in figure A7.4.2-4 for rod segment NBS 5B.

Rockwell B (HRB) hardness measurements were made on each of the transverse

sections examined for microstructure. Twelve measurements were made on each

section. The average hardness value for the finer grained hanger rod NBS 5A

material was HRB 74.5 with a range of HRB 72-76. The average hardness value

for hanger rod NBS 5B material was HRB 68.5 with a range of HRB 66 to 71.5.

In the section from hanger rod NBS 5B, there was a slight hardness gradient

with hardness decreasing from the outside toward the center.

A7.4.3 Washers

Hardness measurements were made on NBS washers and on washers obtained from

the walkway debris. A metallographic examination was performed on sections

through a hanger rod washer obtained from the walkway debris at location 9MW

and through one of the NBS hardened washers.

Rockwell C (HRC) hardness measurements were made on the surfaces of four washers

obtained from the walkway debris. The results of these measurements are given

in table A7.4.3-1. It is apparent from these results that the washers obtained

from the walkway were hardened washers.

Rockwell C hardness measurements were made on the surface of one NBS hard

washer, and Rockwell B (HRB) hardness measurements were made on the surface of one unplated regular grade washer. The results of these measurements are also

given in table A7.4.3-1.

Knoop microhardness measurements at a load of 500 grams force (HK500 ) were made

on a cross section through a washer from the walkway debris at location 9MW

after it had been used in an NBS full length test on box beam 9M. During the

test, the washer fractured into five pieces. A microhardness traverse was made

through the thickness of the washer on the section examined. The washer thickness was approximately 0.075 in (1.80 mm). Average hardness from 16 measurements across the section was 459 HK500 which is approximately equivalent to

44.3 HRC and the hardness range was 422 to 514 HK5 QQ (41.5 to 48.5 HRC). The

highest values were near the center of the section and the lowest values were

near the surface of the washer. The microstructure of the washer from location

9MW is shown in figure A7.4.3-1. There is a very small apparent decarburized

A-25
layer at the surface (light area at the top in the figure). Tempered martensite

is the primary constituent of the microstructure.

A similar microhardness traverse on a section through one of the NBS hard

washers was made. Hardness values in this section, excluding the decarburized

layer at the surface, averaged 431 HK500 (42.5 HRC) and ranged from 401 to

422 HK500 (^0 to 43.5 HRC). Measured hardness in the decarburized layer was

as low as 247 HK500 (99 HRB). The microstructure of the NBS hard washer is

shown in figure A7.4.3-2. The decarburized layer at the surface appears light

in the figure. Tempered martensite is the primary constituent in the

microstructure.

A7.5 CHEMICAL ANALYSIS

Five specimens from the walkway box beam longitudinal welds (four exterior

welds and one interior tack weld) and weld specimens from four NBS box beam

replicas were analyzed for chemical composition by emission spectrometry. Also

analyzed for chemical composition were two samples of hanger rod material

removed from the walkway debris.

A 3/4 mm vacuum spectrometer with an adjustable waveform excitation source was

used for the analysis. The instrumental analytical curves were constructed

using NBS SRMs 1261, 1262, 1263, 1264 and 1265 plus other selected reference

materials. All specimens were surfaced using 50 grit AI 2O 3 sanding disks. In

order to confine the analytical discharge to the weld area, a boron nitride

disk with a 0.157 in (4 mm) opening was used in the excitation stand.

The specimen identification numbers and origins are listed in table A7.5-1.

Actual locations of specimens within the walkway box beam and hanger rod segments are described in figures A7.3.2-1 through A7.3.2-3 and in figure A7.3.3-1.

Normal laboratory routines used for SRM homogeneity testing were used in the

analysis. Program outputs included averages, standard deviations and a pictorial presentation (box plots) of the individual values for those elements

normally considered the most important in ferrous analysis. Each value reported

in the tables of this section is an average of four exposures.

A7.5.1 Box Beam Longitudinal Welds

Results of the analysis of longitudinal weld specimens obtained from segments

of the walkway box beams are listed in table A7.5.1-1. In table A7.5.1-2, the

results obtained from the four weld specimens removed from NBS box beam replicas

are presented. In each case the tables include analytical values for the base

metal in the flange on either side of the longitudinal weld seam.

It is concluded that of the four NBS weld specimens analysed, specimen M2 (flux

cored electrode) most closely corresponds to the weld material in the walkway

box beam longitudinal welds. This is based primarily on the comparable values

for manganese, silicon and titanium. While this comparison does not rule out

the possibility of other types of electrodes being used in the fabrication of

the walkway box beams, it is in agreement with information provided by the

A-26
fabricator's legal counsel regarding welding procedure as noted in chapter 6 of

this report.

A7.5.2 Walkway Box Beam Interior Tack Weld

Results of the analysis of the interior tack weld specimen removed from box beam

8L (NBS 2) are listed in table A7.5.2-1. The analysis of this weld is comparable to the four walkway box beam welds discussed in section A7.5.1, and it is

concluded that exterior and interior welds were made using the same type of

electrode.

A7.5.3 Walkway Hanger Rod Specimens

The chemical analysis of two hanger rod specimens (one specimen from each of two

segments designated NBS 5A and NBS 5B) is presented in table A7.5.3-1. The

analysis clearly shows that the two hanger rod segments are from different

heats since nine elements have significantly different concentrations. In

addition, the sulfur value in specimen 5AC (NBS 5A) shows this element at or

just above the limit specified for ASTM Grade A36 steel. Further analysis of

this material by a gasometric method showed the sulfur value to be within

specification with levels of 0.046 + 0.001 for rod 5A and 0.033 + 0.001 for

rod 5B as reported in table A7.5.3-1.

A-27
500

(HRB)

Hardness

Numbers o o Cl \0

c^1 ON ON 1 1 00 00 1 o 1 1 o>> <S

a^ 00 00 00 00 >_ s-x 'w' Cl ui

(D fsj >0* o <f s£> 00 • 00 rg o o 00 1 o> 1 c CNi C>J »—• f—

m LO

CO 1 1 1 1 • ! • a^ CO f—

Cl o O 00 c^ \0 r>. 00

CNJ

CO 4^

CQ CsJ q; CNI in <T

oo • • • • • S—^ CO CO 00 o^ CM -vf u a^ 00 00 00 00 <r o 0) s_^ V-X S—'' N—*' V—-' • • • c > 00 X a^ CM 00 CM m Cl o < O 0> O' 00 B •H CvJ i*^

COu

D o

CQ <D CO X (A o U-i 4J CO o cu X s

oo <D <u Cl Cl CN* <r

m <r r—

3 X u CM CM o e 3 D CA X 2 CO H (U 2 wco

CO

CO Cl 00 o CO

ON cn ON1 ON1 001 CO1 Q) o ON 1 o 1 in 1 Cl 1 Cl

00 ON CM On 00 00 00 C h—-« Sw/*

m

cO

XX 1-^X •

cti <r Cl <r o <J^ Cl

X CM1 Cl CM CM 00i 1 1 o X 1 o 1 a^ 1 cn 1 cn 1 o 1 CM 1 CM o o o 00

CM Cl CM

W

0)

pt'w

<v H

0)c

T3

CO X

(DW)

COUt

0)><

CA

U-l 4^ O C

o;

u 6

0> 0) X u B 3 3 CA 2 CO

m

m o^

00

CM Cl

Cl CSJ

ro 0000

'W' Nw*' 0^ Cl 1^

CN f-l

m Cl

00 00

<t Cl

00 <

0)

0) c no 4-)

w

X

r—

C <v •H

O .u • M-4

X o CJ CO

a

d o O

cC •H 3 CO 3 o H U 4.J X o s 4J

u 3 3 O 0) 4-» 3 4J 3 3 3 00

QJX 3 V-i iJ

O 3 d

CO o 3 <U 3 c XX 3

<D CO 2 c 3 3 3 rH

U-i c 3 3 O

B 4-4

O o ««

u S O 3 3 X

O

CM tM

O

O 3 S •3 3 M

d c CL U •3 3 3 M-4 •H o c cn CM 3 X 3

•H CQ o < X

X 3 d 3

00 4^ •H 3 >> iJ 4J s 3 d •H 3 U

a; q;

u

U 3 X x:

X 3 i-i OO 3 00 3

cc! s •H *3 3 3 4J 4J 3 O o d

d

X

CA

X -3 3 k4C

M cn 2 3 3 M 3 3

*3 C! 3 O o C < 3 1—

< O

X 3 X CO 2 M C/D 2 cfl M 2 u <4^ W

Q)

U < -C •H rH 3 H 2 u o X ^ x:

01 J-l 4-1 3 3 Wi o o a w z c

rt

A- 28

(^)

Values

in

brackets

are

HRC

hardness

numbers
Table

A7.4.1-2

Hardness

Test

Results

from

Transverse

Sections

Through

Box

Beam

8L

(NBS

2) • O /**y o in o 00

m

C7^ c?>1 CTn1 001 001 t CM 00 1 a^ 1 o^ 1 00

o^ cn 00 00

'w'' '— ' s— s-x <7b <0N

0) CO o 00

oo CO in CM o a\ 00 1 1 1 c CM CM CM CM tP m m m

CO 1 1 1 1 1 1 • • • Pi ip »—

00 o CO CO

<r 00 vO in 00

CM CM fp fp

CO CM CU CO N ' in in S 00 • 1—

• • 03 CO 00 a^ CT' 00 CM O

CMu C7^ CM o> 00 00 00 00 CJ^ CO in

0) ' l_—1 SwX 'w' S—' '

• • • d > CO 00 00 <f f-H vD t—l in m o < CM O On vo 00 r-- •H CM CM CM CM 1—

fP

u

(U

C/J cn

U-l

u

O

C

0)

u

B

<U 0) Xi u B 3 D < W

(U S

00 f-C CSJ CO fsj

m CM

CM CM

ww

a;e32w

CO

(UcU

CO

v£>

CT'I m

<D00c

CO

oti

o>

00

Nw' o

CO

CMI ON

<7\

CM CMOs I I I—

CT^ 00

m

00

r*- I 00 in 1 • CO

00 CO CM 00

O

I—I r-l 00 00

CM CM i-H ,-1 I i II m CO vo O m

CM r~< r—< T—

m

CM00I m

ON

vO

o^ I mI CO o r-.

Oo CM 00 00 00 00 fp

cO • • • • • c u r—i 1—

00 »p o o ON CJN 00 00 00 »P CO CM

•H > Nw/ s— Sw«' • • • P < o C3N vO 00 fp m

CJ 1—

O o> 00

(U CM CM iP iP

CO

M-l -P o c

a;

p s

0) Q) ^ p e 3 3 CO :s CO

<u S

CM <tm

m 00 CO .—I CM CM c T3 p CO c •P o p • p o (U CO o- d o o

•H 5 co CU o P p o e p

p CU CU

O CU

p TOp CU 3 CO oo

CU CO 3 u

upO CO

d

CO

O CO

p 3 d

X

X CO

CU CO re

d CO <u CO

p Ip c CU CO o B p o o A p B o CU CO X o

tM ^a o o CO S •r-) (U

u

d c G- u •r-> -o s p •p o p d 5c CO p T3 CO CO •H CO o <J x: X d CU

X

X

X

00 P •p 'd to

pp S <u

d •p CU

p (U

p

p

0) 0)

p

p .CO x: P 3 u 00 CO 00 CU s 3 p

Pi s •p 'O CO

pp CU

O o pd

d

XO o w p X < 3 u d CM CO CU CO CM CO s T3 CO T3 d CU O o CU p < o p . CU d P CO IS CM CO z CO u SC p p CO CO

CUu x: •p

p

:s

Hu

Q ixi

A-29 I

(^)

Values

in

brackets

are

HRC

hardness

numbers
• o o CO

o^I ON1 00 1 sO 1 CM 00

00

s-/ o m CO

00 o o CM sD a CM CM 00

CO 1 1 1 1 cd CO O' ON O

lT» tn r*^

f—r—

CO CM OJ s: X 00

ca CO cn w

s: <u O' C > o < B •H

CO iJ

<DU

CQ (V to X (0 O M-l 4^ CO o c

0>

iJ

a

oc 0) <D o J=l t-l o E d u h a CO x: z CO H 0) s

COCo

•H CO u u U 0)

(V -O

to Ea

(U z

CO Q) u CO 00 o CO d > a; CO

CO c c 'O

CO

u

w CO H X E /-s o CO u

U-l s

s_^

CO

X 4-) o CQ 0)

i-H o CO 00 D ID CO

CO c u

0) o OJ oi •H >

iJ < J-t o

CO 0)

(U CO H

CO

CO CO

0) CM 4^ c o d

no 0) Vj u E

CO cu 0)u E d d CO CO z CO 1 0) X

00o

ON

a^I o^I fsl v£>

00

00

O

o^I 00O<^4I <r

\o

00

ON

SO

00vO

00

00I OSO

00I CMvO

CM

00 o O

00

CM

00I 00

CO

ro

CMCM

r*^I cn

<r

CM

CM

-Q

CO H

u o o e 4J 4J 0) o 4J u y d CO

(U 4J o CO CO 4J 4J 3 c X XI d e 0) 0> CO CM a> lU to u E o o y y CO X5 O

CO

X

m

X s •r-) q;

d .r-) 4J •1-1 4J •o 4^ o fH •o 3 pa CO •H CO j= x: < o <: o X T3 d

oo 4J

u

M z w

X 0)

d •H 0>

c; 0)

u

d f-H 00 CO 00

5: o o (1) ^ <JJ

A

u

d 1—t d z to d M C N y CO M CO T) d < = ^ y rH < O fH

rH tsj CO

X (Q

Xy u*X 4J 4-1 0) < X X •H 5 X X o u O

A-30

Elsewhere

in

flange
Table A7.4.4-1 Results of Washer Hardness Tests

Hardness

Washer Number of HRC HRB

Identification Measurements Average Range Average Range

SUE Top 8 40.2 39.0-41.0

8LW Top 8 43.0 40.0-45.0

9ME Top 8 37.5 34.5-40.5

9MW Top 8 44.0 42.5-45.0

NBS Hardened 5 39.6 38.5-41.9

NBS Regular Grade 5 60.7 58.9-61.3
Table A7.5-1 Origin of Specimens Analyzed for Chemical Composition

Specimen Identification Origin

1BX4 Bottom flange of walkway box beam 9U (NBS 1)

2BX1 Bottom flange of walkway box beam 8L (NBS 2)

3BX1 Bottom flange of walkway box beam 9M (NBS 3)

2TFX4 Top flange of walkway box beam 9M (NBS 3)

B2 NBS box beam replica B2. E7018 electrode

C3 NBS box beam replica C3. E7014 electrode

M2 ,1I NBS box beam replica M2. Flux cored electrode

N6 NBS box beam replica N6. Mild steel electrode

2C Interior tack weld, bottom flange, walkway box

beam 8L (NBS 2)

5 AC Fourth floor to ceiling walkway hanger rod 8E

(NBS 5A)

5AB Second to fourth floor walkway hanger rod (NBS 5B)

A- 32
Table

A7.5.1-1

Chemical

Analysis

of

Walkway

Box

Beam

Longitudinal

Welds

(UBOZ

c

o

COO

c

(UaH

o

(Ua

C/D

A-33
Analytical

Values —

Percent

by

Weight eD

s:o

CMI <

d) Xi

to H

1-1 <U XiB32Co

•r^ U

tooc

<D T3Ce

•HO

tucto

A-34
Table A7.5.2-1 Chemical Analysis of Walkway Box Beam Interior Tack Weld

Analytical Values—Percent by Weight

Specimen Identification Number

Element 2C

base weld base

Carbon .184 .091 .184

L ' V-T .184 .095 .181

V*'-' *

V

Phosphorus .017 .012 .016

.018 .013 .017

Sulfur .016 .018 .015

r .017 .018 .015

Manganese .711 1.096 .719

.722 1.086 .722

Silicon .193 .452 .198

.195 .442 .197

Nickel .011 .010 .010

.011 .009 .010

Chromium .018 .023 .018

.018 .021 .018

V anadium .002 .006 .002

.002 .006 .002

Titanium .001 .014 .001

.001 .014 .001

Molybdenum .005 .004 .005

.005 .004 .005

Copper .012 .016 .012

.012 .016 .013

Cobalt .005 .004 .005

.005 .005 .005

Aluminum .001 .001 .001

.001 .001 .001

Niobium .001 .003 .001

.001 .003 .001

Zirconium .001 .002 .001

.001 .001 .001

A-35
Table A7.5.3-1 Chemical Analysis of Walkway Hanger Rod Specimens

Analytical Values —Percent by Weight

Specimen Identification Number

Element

SAC 5BC 5AX1* 5BX*

Carbon .168 .200 .159 .200

.168 .197

Phosphorus .037 .010

.038 .009

Sulfur .050 .035 .046 .033

.052 .035

Manganese .510 .672

.527 .696

Silicon .187 .038

.185 .039

Nickel .094 .053

.098 .055

Chromium .106 .115

.110 .117

V anadium .001 .001

.001 .001

Titanium .001 .002

.001 .002

Molybdenum .009 .009

.009 .009

Copper .330 .112

.338 .114

Cobalt .008 .007

.008 .007

Aluminum .001 .003

.001 .005

Niobium .001 .001

.002 .001

Zirconium .001 .001

.002 .001

* Gasometric method

A-36
TOP

EAST H

O)w

H

a

O

H H

C/3 O <ri PQ W

O

H H

H CD O W

PQ S

A-37
0009

1

o

o

o

in

ind

<

QC

I

CO

o

o

o

o

o

o

CO

o

o

o

<N

O O

O

spunod ‘QV01

A-38

Figure

A7.3.1-1

Load-strain

plots

for

I-IBS

channel

specimens

BLl

,

BL2

,

BL3,

BTl,

BT2.
0009

spunod ‘avOl

A-39

Figure

A7.3.1-2

Load-strain

plots

for

NBS

channel

specimens

BT3,

BFl

,

BF2

,

YLl,

YL2.
0009

lOd

Z

<

QC

h—

CO

A-40

Figure

A7.3.1-3

Load-strain

plots

for

NBS

channel

specimens

YTl,

YT2,

YFl

,

YF2
a. North face of box beam segment 9U (NBS 1).

Figure A7.3.2-1 Location of test specimens from box beam segment 9U obtained

from the walkway debris.

a. North face:

Longitudinal web tensile test specimens 1-LNl , 1-LN2

Transverse web tensile test specimens 1-TNl, 1-TN2

Parts of metallographic specimens 1-BMl , 1-BM2

b. Bottom:

Parts of metallographic specimens 1-BMl , 1-BM2

Transverse tensile test specimens across the

weld 1-BX3W2, 1-BX3W4

Chemical analysis specimen 1-BX4

c. South face:

Longitudinal web tensile test specimens 1-LSl, 1-LS2

Transverse web tensile test specimens 1-TSl, 1-TS2

Parts of metallographic specimens 1-BMl, 1-BM2

d. Top:

Longitudinal flange tensile test specimens 1-TFN, 1-TFS

A-41
b. Bottom of box beam segment 9U (NBS 1)

c. South face of box beam segment 9U (NBS 1).

d . Top of box beam segment 9U (NBS 1).

Figure A7.3.2-1

A-42

III
1

’O

0) CM c s

•H

cO

g

4-1 CM

H

X 1 o •> CM CM

r-4 S X a •> P4 00 X r—

1 1 a CM

4-1 CM

H

a 1 • CO CO CM 0 c s

CM 60 CO CO pq

(0 0 C 1 cn CO •H <0 o B

CM 0 <0 *H CO '—

cO OO 3

CO CO CO CO iJ X a. 0

00 4J CO •H X CO <J

4-1 o CO 4-1 (0 C X 4J CO a.

0) CO CD 0 0 (0 4-1 60 o rH O

(U )-l •H (0 •H

CO <4-1 CO i-H

X

C -H a, 0 CO (0 CO CO

CO ti 4J

C V4

cu <0 • (0 60 XI 6 CO X X o

•H *H <0 rH O J-i S X !—C o CO X (0 CO X a CO X S X

CO T3 cO CO

<4-1

C CO 0 o 4-1 •H CO CO CO • • t3 P4 <x

(U <0 s <0 3 CO

O o 4-1 X o X >

CO iH CO •H CO CD

<4-1 <4-1 cO <4-1 60

C

X • • O S C CO X 0 X X O Vj CO O

4-1

C (0 4-1X

H (X

X

)-l

OX P4

X o •H 4J o o s 4.4 !S «

CO 0 o o • O V4 • •

CtJ

X >4-1 ct3

X

CMXX CM 1 X

CM

H1 CM 1 CM CM S S

pq CO

X

X 1 X X I-H 1 CM X 1 X CM

CM

H

CO 1 •* 1-M CO 3 CM r-4 s o 3 s

pqX 3 3 X 1 o 0 3 1 CM 3 •H 3 CM O 0

CO CO 3 •H 3 3 3 f—4 O, O 3

CO 0)

X 3 3 3 0 0 X 3- 0

•H •H 1 X 3 •H O o CM 3 O

CO CO 3 X 3

CX X. 3 X 3 3-

CO CO 3 3 3

Ml- 0 3 X o X a •H I—

CJ •H CO CO O •H 3 •H X <0 X 3 3 X X X X O. 3 •H 3-

cd 1 3 3 3 3 u CO CM X 3

60

X 3 3 60 o •H X X X O

tH CO CM 3 3 1—1 iH 3 a X s X rH

Cd <0 CO

X 3 3

4J

X

X 3 rH & X

d)

X 3 3 3 B <0 1 3 3 3 0

CO CM •H 3

M-l

X I—

• • 33 P4

X

O (0 03 3 3 3 3 O > iH O O X >

CO CD 3 •H 3 •H 3 3

4-1 3 & 0 <x 60 3 X u 3 3 3 3 S-i cd X X X O 3 3 H CJ) X X H X • • 3 a O o X H• o T3

CMI CM• CO<

0)3

60

•H

O

PQ

0)

A-43

Longitudinal

flange

tensile

test

specimens

2-TFN,

2-TFS

Metallographic

specimen

2-TFXl

Chemical

analysis

specimen

2-TFX4
South

face

of

box

beam

segment

8L

(NBS

2)
A-45

Bottom

interior

of

box

beam

segment

8L

(NBS

2).
Figure A7.3.2-3 Location of test specimens from box beam segment NBS 3-5

from box beam 9M obtained from the walkway debris.

a. North face:

Longitudinal web tensile test specimens 3-LNl, 3-LN2

Transverse web tensile test specimens 3-TNl , 3-TN2

Parts of metallographic specimens 3-BMl , 3-BM2

b. Bottom:

b.l: Parts of metallographic specimens 3-BMl , 3-BM2

Transverse tensile test specimens across

the weld 3-BWl , 3-BW4

Chemical analysis specimen 3-BXl

Fractographic analysis specimen 3-DBB-2

b.2: Fractographic analysis specimen 3-DBB-l

c. South face:

Longitudinal web tensile test specimens 3-LSl , 3-LS2

Transverse web tensile test specimens 3-TSl, 3-TS2

Parts of metallographic specimens 3-BMl, 3-BM2

d. Top:

Longitudinal flange tensile test specimens 3-TFN, 3-TFS

A-46
A-47

North

face

of

box

beam

segment

9M

(NBS

3-5).

Figure

A7.

3.2-3
Bottom

of

box

beam

segment

9M

(NBS

3-5).

Figure

A7.3.2-3
LnI CO2

CTnC

0)e

bO

0)

CO

COI CNCO< a

cc) 0) XiXo

x>

0)d

(30 •H

fa

CMO

CuoH

A-49
0009

L

spunod ‘avon

A-50

Figure

A7.3.2-4

Load-strain

plots

for

walkway

box

beam

specimens

1-LSl,

1-LS2

,

1-LNl,

1-LN2,

1-TSl.
spunod ‘avon

I

A-51

Figure

A7.3.2-5

Load-strain

plots

for

walkway

box

beam

specimens

1-TS2,

1-TNl

,

1-TN2,

1-TFS,

1-TFN.
0009

A-52

Figure

A7.3.2-6

Load-strain

plots

for

walkway

box

beam

specimens

2-LSl,

2-LS2,

2-LNl,

2-LN2,

2-TSl.
0009

A-53

Figure

A7.3.2-7

Load-strain

plots

for

walkway

box

beam

specimens

2-TS2,

2-TNl

,

2-TN2,

2-TFS,

2-TFN.
0009 o

o

o

in

o

o

o

o

o

o

CO

o

o

o

CM

O

spunod ‘avon

A- 54

Figure

A7.3.2-8

Load-strain

plots

for

walkway

box

beam

specimens

3-LSl,

3-LS2

3-LNl,

3-LN2,

3-TSl.
0009

I

o

o

o

U)

spunod ‘avon

A-55

Figure

A7.3.2

9

Load

strain

plots

for

walkway

box

beam

specimens

3—

TS2

3~TN1

3—

TN2

3-TFS,

3-TFN.

’

’

’
NBS

5BM

pqm

X}e

(0 <inC

OJs

60

<U

CO T)O

>-i 0)60c

ccJ e

CO

•r4 o u p Xi

<4-1 (U T)

CO

(3 >>

(U cO a

•H ^ O iH

(U CC5 O. ^

CO

0)

*-> Xi

CO 4J

(U •p

ao

4-1

p

O CH C T3 O (U •H C U «H

CO CO O 4-1 O Xi

hJ o I fO

cn

<0

(Up3

60

•H

Pl4

A-56

Longitudinal

tensile

test

specimens

5AT1,

5AT2,

5BT1,

5BT2

Metallographic

specimens

5AM,

5BM

Chemical

analysis

specimens

SAC,

SBC,

5AX1,

NBS

5BX
10,000

1

o

o

o o

o oo

o

o W

oo O W

CO ^

Km/ OJ spunod ‘avon

A-57

1

Figure

A7.3.3-2

Load-strain

plots

for

walkway

hanger

rod

specimens

5AT1

5AT2

5BT1,

5BT2.

’
r-l / 9 9

Figure A7.4.1-1 Transverse section through NBS weldment IC welded by the GMAW

process using mild steel welding rod. The weld is in the

center connecting flange parts of the two channel segments.

Parts of the web regions of each channel are also included in

the section. Etchant: two percent nital ~X1

Figure A7.4.1-2. Part of the transverse section shown above, but a higher

magnification. The light region in the center is weld metal.

The dark regions adjacent to the weld metal are the heat

affected zones. The light regions to the left and right in

the photograph represent base flange regions of the channel

segments. The line of small dark, elongated marks is the

result of microhardness measurements. Etchant: two percent

nital. X8.5

A-58
Figure A7.4.1-4 Transition region from weld metal (right) to heat affected

zone (left) in transverse section through NBS weldment IC

.

Etchant: two percent nital. X200

Figure A7.4.1-3 Microstructure representative of the weld metal in transverse

section through NBS weldment IC. The microstructure appears

to consist primarily of bainite. Etchant: two percent nital.

X200

A-59
Figure A7.4.1-5 Representative microstructure of the heat affected zone in

transverse section through NBS weldment IC . The microstructure consists of ferrite, primarily as a network in

prior austenite grain boundaries, bainite, partially

spheroidized carbides, and tempered martensite.

Etchant: two percent nital. X200

Figure A7.4.1-6 Microstructure representative of the transition region from

the heat affected zone (right) to base channel material (left)

in NBS weldment IC. Etchant: two percent nital. X200

A-60
>

.f^^-^*.*^%'i v'-.v5? -,: V -V 1

;.: .1- :^.. i i /V

.

iv. -i-i' •'=

^•^4;a''-x-' .I'^'i'*^ '-»»--& -

*', ' '"'/**,- ^ - 'i^'T ^ «4 »’^j V

f-*:

, ' * V'r^- ^ " a

^ ' •V>;* ^

te *» *“ * ^Zt"\^

^ /V^f' \ k ^ ' -A ?v>7* **- ^ . A,' '’•> w»'‘ w 3 -I'j '*^ * ^ m,» II

X % <*<'3^- : , # «v j^>' * s'

» <*;% w

-.»ir .10

>y-ri^'0‘*o'

't 1* ^*1

* v:<<,'r^.“ T-"; '

<v <s*

' Y

,y^'- \ ’.A ‘'^'Y' '.» ^ ,

-rC ’t A

X I

J " u.^ A >»*» *L *^ /

it-

' -«<•

‘ 4 At |> 4'

0f ^ ^ *4 'v - , . -7^* ' ^ Wr'

^ :.j^^

:l, On

4'J A^^ 4

* » -3 *S

'»

V

47'

4 A^V'^:r

7' f

Figure A7.4.1-7 Microstructure representative of the base channel material

from NBS weldment IC. The microstructure consists of relatively fine grained ferrite (light) and pearlite (dark) in a normalized condition. Etchant: two percent nital. X200

A- 61
I

Figure A7.4.1-8 Transverse section IBMl through the bottom of walkway box

beam 9U (NBS 1). The north channel of the box beam is to

the left and the south channel is to the right. The weld

connecting the flanges of the two channels used to fabricate

the box beam is in the center. Parts of the web regions of

each channel had been removed before this photograph was

taken. The indentations appearing on the surface of the

section are the result of hardness measurements.

Etchant; two percent nital. ~X1

Figure A7.4.1-9 Part of the transverse section shown in figure A7.4.1-8, but

at higher magnification. The region at the bottom center is

weld metal. The dark gray regions on either side of the weld

metal are the heat affected zones associated with the weld.

The lighter regions at either side of the figure beyond the

heat affected zone are base channel material.

Etchant: two percent nital. X8.5

A-62
Figure A7.4.1-10 Transverse section 1BM2 through the bottom of walkway box beam

9U (NBS 1). The north channel of the box beam is to the left

and the south channel is to the right. The weld connecting

the flanges of the two channels used to fabricate the box beam

is in the center. Parts of the web regions of each channel

had been removed before this photograph was taken. The indentations appearing on the surface of the section are the result

of hardness measurements. Etchant: two percent nital. ~X1

Figure A7.4.1-11 Part of the transverse section shown in figure A7.4.1-10, but

at higher magnification. The region at the bottom center is

weld metal. The dark gray regions on either side of the weld

metal are the heat affected zones associated with the weld.

The lighter regions on either side of the photomacrograph are base channel material. Etchant: two percent nital. X8.5

A-63

i .
Figure A7.4.1-12

Figure A7.4.1-13

'M:

\

’1, yv 4 *'/

' s>- if'i f

•

Representative microstructure of the weld metal in transverse

section IBMl through box beam 9U (NBS 1). The microstructure

consists primarily of bainite. Some inclusions are evident.

Etchant: two percent nital. X200

Representative microstructure of the weld metal in transverse

section 1BM2 through box beam 9U (NBS 1)

consists primarily of bainite. Etchant:

X200

The microstructure

two percent nital.

A-64
Figure A7.4.1-15 Hard area similar to that shovm above, but at higher

magnification. The hard area is in the center running from

side to side. The microstructure appears to consist of fine

grained tempered martensite. Parts of two hardness impressions can be seen at either side of the figure.

Etchant: two percent nital. X800

Patch of hard material (dark streak) at the transition from

weld metal (top right) to the heat affected zone (bottom

left) in section IBMl. The elongated dark areas are hardness

impressions. Etchant: two percent nital. XlOO

Figure A7.4.1-14

A-65
Figure A7.4.1-17 E.egion representative of the heat affected zone in

section IBMl. The microstructure appears to consist of

ferrite, both as a network in prior austenite grains and

as needles, bainite, partially sheroidized carbides, and

tempered martensite. Etchant: two percent nital. X200

Figure 7.4.1-16 Transition zone from weld metal (right) to heat affected

zone (left) in section 1BM2. Some inclusions can be seen. Etchant; two percent nital. X200

A-66
;l

i

Figure 7 .4

r'

.1-18 Region representative of the heat affected zone in

section 1BM2. The microstructure appears to consist of

ferrite, both as a network in prior austenite grains and

as needles, bainite, partially spheroldized carbides, and

tempered martensite. Etchant: two percent nltal. X200

(

I

1

-

i Figure A7.4.1-19 Transition from heat affected zone (right) to base channel

material (left) in section 1BM2. Etchant: two percent

nital. X200

A-67
,1

(I

]'

I

Figure A7.4.1-20 Region representative of base channel material in

section IBMl. The microstructure consists primarily

of ferrite (light) and pearlite (dark) in the normalized

condition. Etchant: two percent nital. X200

I

A-68
Figure A7.4.1-21 Transverse section 2BM1 through bottom of walkway box beam

8L (NBS 2). The north channel of the box beam is to the

left and the south channel is to the right. The weld

connecting the flanges of the two channels used to fabricate

the box beam is in the center. Parts of the web regions of

each channel had been removed before this photograph was

taken. The indentations appearing on the surface of the

section are the result of hardness measurements.

Etchant: two percent nital. ~X1

Figure A7.4.1-22 Part of the transverse section shown in figure A7.4.1-21, but

at higher magnification. The region at the bottom center is

weld metal. The dark gray regions on either side of the

weld metal are the heat affected zones associated with the

weld. The lighter regions on either side of the figure

beyond the heat affected zones are base channel material.

Etchant: two percent nital. X8.5

A-69
Figure A7.4.1-23 Transverse section 2BM2 through bottom of walkway box

beam 8L (NBS 2). The north channel of the box beam is

to the left and the south channel is to the right. The

weld connecting the flanges of the two channels used to

fabricate the box beam is in the center. Parts of the

web regions of each channel had been removed before this

photograph was taken. The indentations appearing on the

surface of the section are the result of hardness

measurements. Etchant: two percent nital. XI

Figure A7.4.1-24 Part of the transverse section shown in figure A7.4.1-23, but

at higher magnification. The region at the bottom center

is weld metal. The gray regions on either side of the

weld metal are the heat affected zones associated with the

weld. The lighter regions on either side of the figure

beyond the heat affected zones are base channel material.

Etchant: two percent nital. X8.5

A-70
Figure A7.4.1-25 Representative microstructure of the weld metal in transverse

section 2BM1 through box beam 8L (NBS 2). The microstructure

appears to consist primarily of bainite. Some inclusions are evident. Etchant: two percent nital. X200

Figure A7.4.1-26 Representative microstructure of the weld metal in transverse

section 2BM2 through box beam 8L (NBS 2). The microstructure

appears to consist primarily of bainite. Some inclusions are evident. Etchant: two percent nital. X200

A-71

il
[

Figure A7.4.1-28 Transition zone from weld metal (right) to heat affected

zone (left) in section 2BM2. Etchant: two percent nital.

X200

Figure A7 .4.1-27 Transition zone from weld metal (right) to heat affected

zone (left) in section 2BM1. Etchant: two percent nital.

X200

A-72
Figure A7.4.1-29 Region of the transition zone from weld metal to the heat

affected zone in section 2BM2. This region is one of the

hard areas. The microstructure appears to consist of

tempered martensite. Part of a hardness test impression can

be seen at the left center. Etchant: two percent nital.

X1200

Figure A7.4.1-30 Representative microstructure of the heat affected zone in

section 2BM1. The microstructure appears to consist of

ferrite, both as a network in prior austenite grain

boundaries and as needles, bainite, partially spheroidized

carbides, and tempered martensite. Etchant: two percent

nital. X200

i

A-73
Figure A7.4.1-31 Transition region from heat affected zone (right) to base

channel material (left) in section 2BM1.

Etchant: two percent nital. X200

Figure A7.4.1-32 Region of section 2BM1 representative of the base channel

material in both sections through box beam 8L. The microstructure consists primarily of ferrite (light) and pearllte

(dark) in the normalized condition. Etchant: two percent

nital. X200

A- 74
Figure A7.4.1-34 Part of the transverse section shown in figure A7.4.1-33, but

at higher magnification. The region at the bottom center

is weld metal. The gray regions on either side of the

weld metal are the heat affected zones associated with the

weld. The lighter regions at either side of the figure

beyond the heat affected zone are base channel material.

Etchant: two percent nital. X8.5

Figure A7.4.1-33 Transverse section 3BM1 through the bottom of walkway box

beam 9M (NBS 3). The south channel of the box beam is to

the left and the north channel is to the right. The weld

connecting the flanges of the two channels used to fabricate

the box beam is in the center. Parts of the web regions of

each channel had been removed before this photograph was

taken. The indentations appearing on the surface of the

section are the result of hardness measurements.

Etchant: two percent nital. ~X1

A-75
Figure A7.4.1-35 Transverse section 3BM2 through the bottom of walkway box

beam 9M (NBS 3). The south channel of the box beam Is

to the left and the north channel Is to the right. The

weld connecting the flanges of the two channels used to

fabricate the box beam Is In the center. Parts of the

web regions of each channel had been removed before this

photograph was taken. The Indentations appearing on the

surface of the section are the result of hardness

measurements. Etchant; two percent nltal. ~X1

Figure A7.4.1-36 Part of the transverse section shown In figure A7.4.1-35, but i at higher magnification. The region at the bottom center Is ! weld metal. The gray regions on either side of the weld

metal are the heat affected zones associated with the weld.

The lighter regions at either side of the figure beyond the

heat affected zones are base channel material. ’ Etchant: two percent nltal. X8.5 i

A-76
Figure A7.4.1-37

I

Figure A7 .4.1-38 Representative microstructure of the weld metal in transverse

section 3BM2 through box beam 9M (NBS 3). The microstructure

consists primarily of bainite. Etchant: two percent nital.

X200

Representative microstructure of the weld metal in transverse

section 3BM1 through box beam 9M (NBS 3). The microstructure

consists primarily of bainite. Several inclusions are evident.

Etchant: two percent nital. X200

\ : i

A-77
Figure A7.4.1-39 Transition zone from weld metal (right) to heat affected

zone (left) in section 3BM2. Some inclusions can be seen primarily in the weld metal. Etchant: two percent nital.

X200

Figure A7.4.1-40 Region representative of the heat affected zone in

section 3BM1 . The microstructure appears to consist of

ferrite both as a network in prior austenite grain boundaries and as needles, balnite, partially spheroldized

carbides, and tempered martensite. Etchant: two percent

nital. X200

A-78
Figure A7.4.1-41 Transition zone from heat affected zone (right) to base

channel material (left) in section 3BM2.

Etchant; two percent nltal. X200

Figure A7.4.1-42 Representative region of base channel material in

section 3BM1 . The microstructure consists of ferrite

(light) and pearlite (dark) in the normalized condition.

Etchant; two percent nltal. X200

*

, -

«

A-79
%

'aI -.

X

•-4#

- s> . 4 Jt ^

" / /'

’^c ^ ,

- , ^X's *

'

’ ’> r «S|

.- -j-* ^

K

* *

s

•

,

“ ;

’ * ^ Jk * H. ” - - '^ ^ *\ % * *K »» ^

. V

, >p

. -X ''

. ’ '/

"^

' ^ .j5

» '^

'if ' T*

' •s«3~

'ife

f'

* ^

.

", ' lx , w » > - ii

r^'^4

>' : . . . TM.- . 4

?" ^ J.

4

y

'

y. 4/w rsT

' 4< < * ^"

'

X r« V •« ^''

> jA r

Mtjr

Vx

^..r • W,-A- , <:>

V ki>

Xt ;* ,,

^ f1

’'j'v i*-'"*^ 4W‘-

"« s"?:

I'*

I.

. V’ S, ,

KJ

f'K X

t

* > iU ^ ^ y "/V i ) , ^ ^ J K

, * Vx . * v,*> i *

'^•J f' " - 1.^ ^ ^ - i" >5 >-' *

>f-\*'j- X'

?

'

' , 'V '.

>*4

'

'C , V

‘ 'C • ‘X

VX*. « . >- V

* .*

'

' * 4T <d V*in ^ y a

y - fc * Figure A7.4.2-1 Transverse section through hanger rod NBS 5A showing the

representative microstructure. The microstructure consists

of relatively fine grained ferrite (light) and pearlite

(dark) in a normalized condition.

Etchant: two percent nital. XlOO

Figure A7.4.2-2 Transverse section through hanger rod NBS 5B showing the

representative microstructure. The microstructure consists

of ferrite (light) and pearlite (dark) in a normalized

condition. Etchant: two percent nital. XlOO

A-80
it - » <Ur* ' > <

i * “ * *.' '* 'r^ ' ^' CW, >' t*:* ,^. <^ » , A

’--, ''^' M ‘ A ” . ,A .. *’ •( ' •*''> ' j(A > *

»* V <*•>

'* -jQ *. f <aAa * li

' '^* ' A*

» - « » « '1C.,. <•--’# *:' ' » ‘i « » 7 I,

* ft A.

' \ ‘ 4T Tir~ r-w>" •

•

^ * <CV* ^

,

.^

• ,j,

•M! v-^- <J . / i f

.

' f>- ,' -- - -

' c.

'• </“ '

-J » V 1.1^ ^. •' "' r -

_ ^ - • N.-S.- -w •*> •.*2

*' x' ’** w ' • ’

"'t*,- V *

-' :-'-4- -* :

‘

y ^ IT'TM

*, * ... ^ ^ ^ V'f * i<,c«*r

t.-..

.• •> ' '-'• . ...

'^. -. »» '^ '4

' S. *

*« i.

' _ ^ SlA • r^:-. *i« s. ’•5." . <np - . * '»T”%'" ^ tT,

' -*' y 'A, 1,. .»i‘'^ . » f

' ...m 1^l „ . ,«*-7#- .f -A »«.•'

«

*

t. 'f ^ / ;i&' - '^:> ^

I .^.

. A

, «i,^ - « ^ . ,r • c'- *% • * ... . ^ ^

'^' a

”’ -i*'

.

. * • At *«* / ^

A.' -7. .'^r^ •

;’ * "

., i’ ,- 7 .A. * 4 - ^ V'V ,. , , ,^ *"*• ,4- ^

" ^ ^ '4 * A,--* ^

1<- % V \ V-, * „ «,’. r-

*"' 'V *»«A.> !t I i .* 4 ^ ,X f

4,..

-^v.

Figure A7.4.2-3 Longitudinal section through hanger rod NBS 5A showing the

normalized microstructure consisting of ferrite and pearlite.

Etchant: two percent nltal. XlOO

Figure A7.4.2-4 Longitudinal section through hanger rod NBS 5B showing the

normalized microstructure consisting of ferrite and pearlite.

Etchant: two percent nital. XlOO

A-81
V

Figure A7.4.3-1 Microstructure of washer from location 9MW in the walkway

debris. The thin, light layer at the surface (horizontal

near the top in the figure) is the decarburized layer at the

washer surface. The microstructure consists primarily of

tempered martensite. Etchant: Picral. X200

Figure A7.4.3-2 Microstructure of NBS hard washer. The light layer at

the surface (horizontal near the top in the figure) is

decarburized. The microstructure consists primarily of

tempered martensite. Etchant: Picral. X200

A-82
E.,.J. .U)

Section A7.6 —

' i>

!*' a

# r* » •

r. I • -!

^v.-r

M S

;£0j5f

' ^ t/vt/

:53 f"

*

‘ ;^> 3 :r • |i 3 ,tc/. ' t.'iVl'

. ‘ «- I r!; ca.r f x.ist (1 o.t)iL

I . - ;

' 3 .

' oe. f joo.’i,;; i;:i:d.

f < ' \ \ ^

I? i

( a..,

''n. '

>

'

sa.i

rif:,'

1 : --

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t

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i*Urr

4 ''

.

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j( tvte" ";:

1 .. » -•1 n

: r,tHr ;

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i

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.... --^.f #;.

i

, } »

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it .0£i

- '• • '-f ^'.,dTr- '^.c^£ ,

•

;.fU£ eibi£ u im

•rov. , -:u 'x4^; j'<{ ,a2 »?•#(

‘

• ?.,:/'< b'')’?)'."?;:;;) :• ii ” 0

i''i L»ofe'n&«r.7( t ;Jr4i.t^'V » <’

i'^»'•:^UA^^^>^..4if'll'J^;l bt_. .>-!r'i:iBa - 3

• tlz‘
Table A7.6-1 Bulk Specific Gravity of Drilled Concrete Cores

Core

Number

Weight (grams)

A B

(b)

A B C D E C-D

C-D C-D

4-02 215.4 206.2 222.8 105.1 222.7 117.7 1.83 1.75

03 238.3 227.4 245.5 114.3 245.5 131.2 1.82 1.73

04 282.3 269.4 291.3 137.5 291.3 153.8 1.84 1.75

06 299.2 286.4 310.1 147.0 310.0 163.1 1.83 1.76

08 307,8 292.7 318.1 155.9 318.1 162.2 1.90 1.80

09 287.7 273.7 297.1 140.6 297.1 156.5 1.84 1.75

11 277.5 264.9 290.9 134.7 290.7 156.2 1.78 1.70

14 268.7 256.4 280.8 127.6 281.4 153.3 1.75 1.67

15 265.5 253.6 276.5 130.3 276.4 146.2 1.82 1.73

17 323.9 308.9 336.2 157.0 336.2 179.2 1.81 1.72

Notes: A = original weight

B = 24 hr oven dry weight

C = saturated surface-dry weight

D = weight immersed in water

E = saturated surface-dry weight after immersion

Bulk specific gravity, air-dry

(b) Bulk specific gravity, oven-dry

1 lb = 0.4536 kg

A-84
Table A7.6-2 Bulk Specific Gravity of Topping Material

Core

Number

Weight (grams)

A

(a) B (b)

A B C D E C-D

C-D C-D

4-02 58.7 57.6 62.7 34.2 62.7 28.5 2.06 2.02

03 51.7 51.0 55.7 30.5 55.5 25.2 2.05 2.02

04 41.5 41.1 49.9 24.5 49.9 25.4 1.63 1.62

06 49.9 47.7 52.8 28.6 52.8 24.2 2.06 1.97

11 38.6 38.2 41.2 23.4 41.2 17.8 2.17 2.15

14 46.3 44.5 51.7 23.9 51.7 27.8 1.67 1.60

15 58.3 55.8 64.3 29.1 64.3 35.2 1.66 1.59

17 58.7 56.3 65.6 31.0 65.6 34.6 1.70 1.63

Notes: A = original weight

B = 24 hr oven dry weight

C = saturated surface-dry weight

D = weight immersed in water

E = saturated surface-dry weight after immersion

Bulk specific gravity, air-dry

Bulk specific gravity, oven-dry

1 lb = 0.4536 kg

A-85
Table

A7.6-3

Compressive

Strength

of

Drilled

Concrete

Cores

<D

'T3 >

<u •H U CO J-J 00 ON nD

m cn cn CM ON

u

M bO ^ cn o cn 00

m CM 00

0) (U

C -H CTn 1-^ 1—-1 r'> <r in in CM

Vj Vj 0) tn CX cx

mm

mm in o B 4J w u o CO

CJ

cnm

m 00 00 00 ON

to ON 00 00 f" 00 00 NO 00 00

cyv CJN ON ON CJN ON ON ON ON • • • • • • • • • u o o o o o o o o o

<u T3 > /=

(U •H 4-1

4-> tn bO

to cn c ^ m I'' CM cn 00 On 00

i~l (U <U -H 00 CM 00 in vD ON o 00 -«d* 3 j-j !-i CO o rH CM 00 <r f’' in cn O a u cx A •

i—H e CO

W

mmm

m Ndm in

CO o u u

tu

V-I o in

mmm o o mm

T3 3 ^ m f" f'' f'' in o CM CM

to rH CO ONm ON o 00

m cn

m o to •H

hJ CC rH vO

m in vD

m cn <a- NO

v_^ 1-^ 1—4 rH f—4

1—1 rH

to 1 c CM m o cO ON o 00 00 o 00 00 o CJN w •H CU C o ^-1 o o ^4 o o rH O o U 5-1 *H o <! s_x ro cn cn cn cn cn cn cn cn u o

CO o m vD o NO o rH

m

Q CO o cn cn 1-H NO c^ NO n*

ON 00 00 00 00

m 00 00

tJ •

1“^ f—41—1

1—1

iH iH S

cu (U CO bO u cu n£) o o NO rH CM NO

m

cd 01 00 00 00 00 00 00 00 00 00

V-I

B o o ON ON ON ON ON ON CJN ON ON

(U to c • > •H •H I-^ 1—i

1-^ iH 1—1 r-t fH iH iH < o Nw/

<Ua

cx 4J CO ON in

m 00 NO o in CM

03

X cu CM 00 cn CM o ON

m ON CM

u bC

x 00

m <r NO NO rH NO

•H o • (U CJ CO cn cn cn cn cn cn cn cn

bOB •H > >- <

S-i (U (U

m r'' o CM cn NO 00 CJN o o o ^4 iH iH iH iH H o s 1 u 3 <r

IS

bOc

•Hc

•H

to 4J O

TOoU

0) X

ns

Vj

to •O

c:to

4-t in

tu

0)

•>

M

r». r>.I CM

U

'O’ U M-lo sH w

in S

<! to

0)

M PQ

C/J X no < cu

CU to

0) CO

CO

'Oc • to o CO

4-1 (U o )-l to o

IM o c TJ o cu •H !—1

4J iH o •H

cu V4

g la;

M o B

00

O bO O 3 • 'O’ •H m • 4= 4-1 CM

4J CO bO tu II II 3 H

CU

a 43

Vt T3 •H iH

4-1 3

CO 3 rH rH

tu ijoa

A-86

1000

psi =

6.9

MPa
Figure A7.6-1. Stress-strain plot for concrete core 4-01

o

Figure A7.6-2. Stress-strain plot for concrete core 4-05

A-87
Figure A7.6-4. Stress-strain plot for concrete core 4-10,

A-88
*-tW)*D

2i-«

cntnmx)—

iCD

TM

>~>fX)~a

z*-*

cncnm^—

jtn

A7.6-5. Stress-strain plot for concrete core 4-12.

o

Figure A7.6-6. Stress-strain plot for concrete core 4-13.

A-89
o

Figure A.7 .6-7

,

Stress-strain plot for concrete core 4-16

o

Figure A7.6-8. Stress-strain plot for concrete core 4-18

A-90
HtftT)

zt-i

o

Figure A7.6-9. Stress-strain plot for concrete core 4-19.

i

A-91

Table A9.2.1-1 Unit Weights of Walkway Materials

Item Unit Weight

Structural Steel Per AISC Manual of Steel Construction

1 1/2" X 20 Ga. Formed Steel Deck 2.20 lbs/ft2

5/8" Type "X" Gyp. Bd. & Framing

(a) 5/8" Gyp. Bd. 2.56 lbs/ft2

(b) 24 Ga. Steel Studs 0.39 Ibs/ft

(c) 24 Ga. Steel Runners 0.31 Ibs/ft

Wood Handrail & Brass Extrusion 5.30 Ibs/ft

Top Glass Grip 1.78 Ibs/ft

1/2" Tempered Plate Glass 6.54 lbs/ft2

Bottom Glass Grip 5.19 Ibs/ft

Steel Support Angle (4 x 3 x 3/8) 8.50 Ibs/ft

Footlights 2.26 lbs each

Footlight Base Plate & Cap 1.33 Ibs/ft

Carpet 0.60 lbs/ft2

Padding 0.25 lbs/ft2

Sprinkler Pipes and Fittings Per AISC Manual of Steel Construction

Aluminum Slats 70.4 Ibs/span

A-93
Table A9.2.1-2 Weight Analysis of Damaged Walkway Spans

Item Weight/Span (lbs)

U7-8 U8-9 U9-10 UlO-11 L7-8 L8-9 L9-10 LlO-11

Cross Beams & Stringers 2191.7 2057.1 2057.1 2174.5 2191.7 2057.1 2174.5

Box Beams ~ 343.8 184.6 — — 184.6 —

Clip Angles 12.7 — — 12.7 12.7 ~ 12.7

1 1/4" (J) Hanger Rods ~ 110.0 — — — — ~

1 1/2" X 20 Ga. Formed Steel Deck 498.9 493.4 493.4 498.9 498.9 493.4 498.9

Gyp. Bd . Attached to Span 1369.2 976.5 968.6 836.8 985.9 932.7 850.1

24 Ga . Steel Framing for Gyp. Bd

.

67.6 67.6 67.6 67.6 67.6 67.6 67.6

Gyp. Bd. Scattered on Deck — 52.0 39.0 41.6 26.0 7.8 —

Handrail Assembly 79.5 297 .4 106.2 — 63.6

Xioo

•H 155.0 —

Top Glass Grip 102.5 — — — 52.1

s

XJO ~ —

1/2” Tempered Plate Glass Panels 416.5 520.6 — — 208.2

c

o^ ~ —

Broken Plate Glass Panels 52.1 156.2 — 13.1 52.1

00X

c — —

Bottom Glass Grip & Support Angle 795.8 790.0 790.0 800.4 795.8 a

CO 790.0 800.4

Footlights & Baseplate 95.9 89.3 45.8 24.4 69.0 26.7 33.0

Carpet & Padding 187.3 187.3 — — 187.3 — —

Sprinkler Pipes — — 97.1 64.4 43.7 86.9 58.0

Miscellaneous Metal Work — 100.0 ~ — 100.0 — —

Miscellaneous Debris 100.0 — — — — — 20.0

Timber Cribbing 156.2 — — — — — 59.4

Embedded Steel Plate — — — — 10.2 — —

Broken Granite Panels — — — — 262.5 ~ —

Total 6125.9 6241.2 4849.4 4534.4 5627.3 4801.8 4574.6

A- 94
Table A9.2.1-3 Weights of Undamaged Walkway Span

Excluding Concrete Deck and Topping

Weight/Span (lbs)

Component

Description U7-8

L7-8

U8-9

L8-9

U9-10

L9-10

UlO-11

LlO-11

W16 X 26 Stringers & 1/4 x 6 Bent Plate 1847.0 1798.6 1798.6 1829.8

W8 X 10 Cross Beams & Clip Angles 344.7 258.5 258.5 344.7

MC8 X 8.5 Box Beams & Clp Angles 92.3 184.6 184.6 92.3

1 1/4" (J) Hanger Rods (Fourth Floor)

(Second Floor)

130.5 261.0 261.0 130.5

1 1/2" X 20 Ga. Formed Steel Deck 498.9 493.4 493.4 498.9

5/8" Type "X" Gyp. Bd. & Framing 2309.4 2309.4 2309.4 2309.4

Handrail Assy & Top Glass Grip 408.3 408.3 408.3 408.3

1/2" Tempered Plate Glass 1249.4 1249.4 1249.4 1249.4

Bottom Glass Grip & Support Angle 795.8 790.0 790.0 800.4

Footlights & Baseplate 104.8 104.8 104.8 104.8

Carpet & Padding 187.3 187.3 187.3 187.3

Sprinkler Pipes 51.1 88.2 97.1 91.8

Aluminum Slats 70.4 70.4 70.4 70.4

Total for Fourth Floor Spans 8089.9 8203.9 8212.8 8118.0

Total for Second Floor Spans 7959.4 7942.9 7951.8 7987.5

NBS-n4A (REV. 2 *8 C) U.S. DEPT. OF COMM.

I

i

I

BIBLIOGRAPHIC DATA

SHEET (See instructions)

4. TITLE AND SUBTITLE

1. PUBLICATION OR 2 REPORT NO.

NBSIR 82-2465

. Performing Organ. Report No. 3. PubI ication Date

February 1982 1

I Investigation of the Kansas City Hyatt Regency Walkways Collapse

5. AUTHOR(S)[^

D. Marshall, E.O. Pfrang, E.V. Leyendecker, K.A. Woodward,

R.P. Reed, M.B. Kasen, and T. R. Shives

6. PERFORMING ORGANIZATION (If joint or other than N BS. see instructions) 7. Contract/Grant No. national bureau of STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street. City. State. ZIP)

10. SUPPLEMENTARY NOTES

j Document describes a computer program; SF-185, FIPS Software Summary, is attached.

j 11. ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

j bibliography or literature survey, mention it here)

I

' An investigation into the collapse of two suspended walkways within the atrium area

Ij of the Hyatt Regency Hotel in Kansas City, Mo., is presented in this report. The

; investigation included on-site inspections, laboratory tests and analytical studies.

j Three suspended walkways spanned the atrium at the second, third, and fourth floor

levels. The second floor walkway was suspended from the fourth floor walkway which

was directly above it. In turn, this fourth floor walkway was suspended from the

'I atrium roof framing by a set of six hanger rods. The third floor walkway was offset

f from the other two and was independently suspended from the roof framing by another

I set of hanger rods. In the collapse, the second and fourth floor walkways fell to

r| the atrium floor with the fourth floor walkway coming to rest on top of the lower

J walkway.

^ Based on the results of this investigation, it is concluded that the most probable

f cause of failure was insufficient load capacity of the box beam-hanger rod connections.

Observed distortions of structural components strongly suggest that the failure of the

walkway system initiated in the box beam-hanger rod connection on the east end of the

fourth floor walkway's middle box beam.

(continued on attached) ^ li. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

building; collapse; connection; construction; failure, steel; walkway.

13. AVAILABILITY

Uni imited

( I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

15. Price

USCOMM-DC 6043-P80
"Investigation of the Kansas City Hyatt Regency Walkways Collapse

ABSTRACT - (continued)

Two factors contributed to the collapse: inadequacy of the original design for the

box beam-hanger rod connection which was identical for all three walkways, and a change

in hanger rod arrangement during construction that essentially doubled the load on the

box beam-hanger rod connections at the fourth floor walkway. As originally approved

for construction, the contract drawings called for a set of continuous hanger rods which

would attach to the roof framing and pass through the fourth floor box beams and on through the second floor box beams. As actually constructed, two sets of hanger rods were used, one set extending from the fourth floor box beams to the roof framing and

another set from the second floor box beams to the fourth floor box beams.

Based on measured weights of damaged walkway spans and on a videotape showing occupancy

of the second floor walkway just before the collapse, it is concluded that the maximum

load on a fourth floor box beam-hanger rod connection at the time of collapse was only

31 percent of the ultimate capacity expected of a connection designed under the Kansas

City Building Code. It is also concluded that had the original hanger rod arrangement

not been changed, the connection capacity would have been approximately 60 percent of

that expected under the Kansas City Building Code. With this change in hanger rod

arrangement, the ultimate capacity of the walkways was so significantly reduced that,

from the day of construction, they had only minimal capacity to resist their own weight

and had virturally no capacity to resist additional loads imposed by people.

Supplementary material is contained in an appendix to this report and published as NBSIR 82-2465A.
NATIONAL BUREAU

OF

STANDARDS

UNITED STATES DEPARTMENT OF COMMERCE

TM W W = WASHINGTON, D.C. 20234

HOLD FOR RELEASE

9:30 a.m., February 25, 1982

Mat Heyman

301/921-3181

TN-5345

CONNECTIONS IN COLLAPSED WALKWAYS AT KANSAS

CITY HOTEL FAR FROM ADEQUATE, NBS REPORTS

Critical connections in two Kansas City Hyatt Regency Hotel walkways

which collapsed July 17, 1981, were capable of supporting less than onethird of the load expected to be carried by a connection designed under

the Kansas City, Mo., building code. That was one of the major conclusions

in a report issued today by the Commerce Department's National Bureau of

Standards (NBS).

Dr. Edward 0. Pfrang, who headed up an NBS investigation of the

nation's worst building collapse, today identified the two factors

related to those box beam-hanger rod connections which were critical in

causing the walkways' failure.

First, Pfrang said, the "connections as initially detailed and

approved for construction provided a capacity far below the capacity

that would have been required to satisfy the Kansas City Building Code."

Second, a change in the supporting hanger rod arrangement "essentially

doubled the load to be transferred" by the connections, "thus further

aggravating an already critical situation."

more
- 2 -

Shortly after the accident which killed 113 people and injured 186

others, Kansas City Mayor Richard L. Berkley asked NBS to investigate

the failure. The mayor's request was endorsed by members of the Missouri

congressional delegation. NBS, a federal science and engineering research

laboratory which traditionally has served in a third party role to

resolve technical controversies, agreed to determine the most probable

cause of the collapse.

The NBS investigation included a review of various constructionrelated documents, on-site and laboratory structural and materials

investigations--including testing of selected parts of the walkways'

debris and NBS replicas of important walkway components--and extensive

engineering analyses.

The bureau's findings are given in a 349-page report submitted

today to Mayor Berkley in Kansas City and reviewed by Pfrang, Chief of

the NBS Structures Division, at a news conference in Gaithersburg, Md.

Walkway's Structure

Three suspended walkways spanned the Hyatt Regency atrium, which

connected a high-rise section and a lower "function block." The second

floor walkway was suspended from the fourth floor walkway directly above

it by six steel hanger rods. In turn, this fourth floor walkway was suspended from the atrium roof framing by another six hanger rods.

The third floor walkway, which was not involved in the collapse,

was offset from the other two walkways and was independently suspended

from the roof framing by another set of hanger rods.

The hanger rods from the roof and from the second floor walkway

passed through the ends of the fourth floor walkway box beams. These

box beams were made up of pairs of 8- inch steel channels which were welded together. The hanger rods were secured by washers and nuts after

passing through the box beams. Linder this arrangement, the fourth floor

box beam-hanger rod connections transmitted the loads of both the second

and fourth floor walkways.

In the collapse, the second and fourth floor walkways fell to the

atrium floor after the fourth floor to ceiling hanger rods pulled through

at the walkway box beam connections.

The NBS Investigation

To meet requirements of the Kansas City Building Code, Pfrang said,

the fourth floor connections between the walkways' box beams and supporting

hanger rods each should have been designed to handle 40,700 pounds--

including the weight of the walkways and a specified design live load of

people. However, the Kansas City code also incorporates a margin of

safety for steel components. Walkway connections designed according to

the code to have a capacity of 40,700 pounds would actually be expected

to have an ultimate capacity of at least 68,000 pounds.

more
- 3

-

After weighing the damaged walkway spans and estimating the number

of people on the walkways at the time of the collapse, NBS researchers

concluded that the maximum load on any of the six connections at the

time of the collapse was 21,400 pounds. Thus, the load on the walkways

was far below that required to be handled under the Kansas City Building

Code.

After conducting extensive structural and materials tests on selected

parts of the walkways and NBS-fabricated replicas, bureau researchers

determined that the average ultimate capacity of each fourth floor

hanger rod-box beam connection was just 18,600 pounds compared to the

expected ultimate capacity of 68,000 for code-complying connections.

Thus, the connections were capable of supporting only 27 percent of the

load expected to be supported by connections designed under the Kansas

City Building Code.

Since the loads on the connections from the weight of the walkways

and people on the walkways at the time of the collapse were so near to or in excess of the estimated ultimate capacity of the actual connections,

failure could have begun at any of the fourth floor box beam-hanger rod

connections, NBS researchers determined. Progressive failure of the

other connections and the walkways' collapse was assured after any one

of the connections failed and the load from that connection was distributed

to the other connections. Based on studies of the walkways debris, NBS

researchers were able to pinpoint a connection at the middle fourth

floor box-beam as the most likely to have failed first.

A key factor contributing to the collapse, the NBS report noted,

was that the walkways were not constructed in accordance with the contract

drawings. As originally approved for construction by the Kansas City

Codes Administration Office, the plan for the walkways called for a single set of hanger rods (attached to the roof framing) which would

pass through the fourth floor beams and on through the second floor

beams. Under this arrangement, each box beam would transfer its own load directly into the hanger rods.

However, during construction the hanger rod arrangement was changed

to an "interrupted" hanger rod scheme so that the fourth floor box beam

connections were required to transfer the load of both the fourth and

the second floor walkways.

This change essentially doubled the load on those fourth floor con- nections. While NBS researchers concluded that this original hanger

rod-box beam connection detail still would not have satisfied the Kansas

City Building Code, they also determined that the original connections

as shown on the contract drawings would have had the capacity to resist

the loads estimated to have been acting on them at the time of the

collapse.

Based on a variety of materials tests of walkway components--

including the welds, nuts and washers, steel channels, and hanger rods

NBS researchers determined that "Neither the quality of workmanship nor

the materials used in the walkway system played a significant role in

initiating the collapse."

more
- 4 -

The bureau's report also notes that in addition to the box beamhanger rod connections, the fourth floor to ceiling hanger rods and the

third floor walkway hanger rods violated the design provisions of the

Kansas City Building Code. According to NBS investigators, though, the

hanger rod code violations were not a factor in the collapse.

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