jference

NBS

Publications

NAT'L INST. OF STAND & TECH K 82-2599

AlllOb Etl4ba istigation of Floor Vibrations

in the "D" Wing of the Main

Building of the Bureau of

Engraving and Printing

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Washington, DC 20234

October 1982

Issued December 1982

Prepared for Bureau of Engraving and Printing

4th and C Streets, S.W.

Washington, D.C. 20228

NATIONAL BUREAU OF STANDARDS

LIBRARY JAN 18 1983

NBSIR 82-2599

INVESTIGATION OF FLOOR VIBRATIONS

IN THE "D" WING OF THE MAIN

BUILDING OF THE BUREAU OF

ENGRAVING AND PRINTING

T. A. Reinhold

F. Y. Yokel

F. F. Rudder

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

Center for Building Technology

Washington, DC 20234

October 1 982

Issued December 1982

Prepared for Bureau of Engraving and Printing

14th and C Streets, S.W.

Washington, DC 20228

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

ABSTRACT

Floor vibrations induced in a Bureau of Engraving and Printing building

by a recently-installed perforator were investigated by measuring relative acceleration amplitudes and phase relationships between a reference

position and points on a grid laid out on the affected floor. From these

measurements, it was possible to determine mode shapes, resonant frequencies

and displacement amplitudes. On the basis of the displacement amplitudes,

anticipated cyclic stresses in the structural system were estimated. The

results of the measurements and analysis were compared with existing data

on vibration-induced structural damage and fatigue strength of steel and

reinforced concrete. Damping ratios were also determined in a separate

test, in order to ascertain at later dates whether any structural deterioration is taking place.

Key words: cyclic strength; fatigue; floor vibrations; machine foundations;

reinforced concrete; steel; structural engineering
, ' 71 * ' /»}
1. Background

Following the installation of two new coiling machine perforators on the first floor of "D" Wing of the Main Building of the Bureau of Engraving and Printing, floor vibrations were observed. In December 1981, the

Bureau of Engraving and Printing contacted the Center for Building Technology of the National Bureau of Standards and requested an evaluation of

the vibrations in order to determine whether potential structural damage

could result. One of the reasons for the concern was the age of the building, which was constructed in the early 1910's.

Following initial explorations by NBS personnel on November 23 and December

3, 1981, it was decided, on the basis of preliminary vibration measurements

conducted by the Bureau of Engraving and Printing (see Fig. la) and observations of machine operation, to pursue further the investigation and conduct

additional measurements. These additional measurements were deemed necessary

to determine natural frequencies and mode shapes of the floor vibrations in

order to more accurately estimate their potential effects on the structural

system, which consists of a concrete joist floor supported by concreteencased steel girders which, in turn, are supported by concrete-encased

steel columns (see Fig. 2). It was also decided to conduct non-destructive

tests in order to determine the concrete strength of the floor joists since

no data on the concrete mix used were available. The vibration measurements

were taken on December 17 and 18, 1981. Concrete impact tests with a Schmidt

Hammer were conducted on December 17, 1981.

This report contains a description of the measurements obtained and their

interpretation.

2. Vibration Tests

Vibration measurements were made on the floor at selected locations on a grid laid out by Bureau of Engraving and Printing personnel. The grid points

are shown in Fig. 3. Vibration tests were conducted on the floor systems under

both machines because each machine is located differently relative to the columns and girders of the floor system.

The machines operate at variable speeds. The machine speed is defined in terms

of the "web speed" (the speed at which the paper advances into the machine in

feet per minute, ' fpm') and is set by the operator. Floor vibrations are sen- sitive to the operating speed as shown in Figs, la and lb. Figure lb presents

the variation of vibration frequency with machine speed and the relative magnitude of floor vibration at two points for each floor studied as a function of

machine speed.

Vibrations were monitored by measuring vertical accelerations using two Kistlertype 303-T accelerometers which were set to a sensitivity of 10 volts per lg.

Measurements were taken by keeping one accelerometer at a reference position

adjacent to the perforator and moving the other accelerometer to selected points

on the grid. These measurements made it possible to determine relative amplitudes and phase relationships between the reference position and the other grid

1
points. These data could then be used to estimate mode shapes. Locations

at which acceleration measurements were obtained are shown in Figs. 4, 5,

6 and 7.

Vibration data were analyzed using a Hewlett-Packard spectrum analyzer to

obtain auto-spectra and cross-spectra.

With the accelerometers placed in two selected locations, machine speed

was varied between 100 fpm and 170 fpm. Subsequent measurements were made

at two selected machine speeds which subjectively caused maximum vibrations.

On the North machine (see Fig. 2), these speeds were 125 fpm and 155 fpm.

These two "critical" speeds on the North machine forced vibrations at two

different resonant frequencies of the floor system. Plots of the relative

peak accelerations for the two North floor locations are given in Fig. lb.

Square symbols show resonance peaks at about 120 and 155 fpm machine speeds.

The 117 fpm speed on the South machine also forced response at a resonance frequency of the floor system. The 160 fpm speed for the South machine was chosen to provide information on vibrations at a high operating speed. Unfortunately, this machine speed did not cause vibration at one of the floor's resonance frequencies. In retrospect, a choice of 165 fpm as the operating

speed would have produced higher accelerations (see Fig. lb). However, it was difficult for the operators to maintain the 160 fpm operating speed during

the tests and a 165 fpm speed would have been even more difficult to maintain.

Also, because the frequency of the peak response associated with the higher

machine speed is 44 percent higher than that associated with the lower machine

speed, the deflections related to the high machine speed vibrations, and hence

the stresses, would be only about half as large as these caused by the same

level of acceleration at the lower frequency of vibration.

In addition to these measurements, floor acceleration caused by an impulse

load (the jump of a person) was measured to determine structural damping.

3. Concrete Strength Tests

A memorandum on the Schmidt Hammer tests is in Appendix A to this report.

Even though the Schmidt Hammer does not provide very accurate information on the concrete strength, it can be deduced from the test that the concrete con- struction in the building is of high quality. The concrete compressive strength

(fc) can be conservatively assumed to exceed 2500 psi , and probably is above

3000 psi

.

4. Interpretation of Test Results

4.1. Analysis of Vibrations

The auto-spectra measurements obtained from the vibration analyzer

were used to determine rms (root-mean-square) acceleration, velocity and displacement at the primary frequency of forced vibration. Peak_values were also

estimated on the basis of assumed simple harmonic motion ( J2 x rms amplitude).

The equations used for converting the spectral values to rms values are given

below:

A

r = YS(n) 1.1719

V

r = A

r (32.2) (12) 61.50 A

r

2-rrf f

2
.1592 Y

V V r r

r

2 TT f f

2 where S(n) = spectral value from analyzer at frequency n in g /Hz

A,

Y

Vr

r

r rms acceleration in g's

rms velocity in in/sec

rms vertical displacement in inches

The factor, 1.1719, in the equation for Ar is related to the window function

used in the spectral analysis and was supplied by the manufacturer of the

spectral analyzer. The other equations result from assuming simple, harmonic

motion and knowing the acceleration. Typical plots of the auto-spectra at

two locations are shown in Fig. 8. Fig. 9 shows a log plot of one of the

spectra with the harmonics of the resonant frequency identified.

Mode shapes were estimated from relative vibration amplitudes and phase

angles. The phase angles, in turn, were obtained from the cross-spectra.

The mode shapes associated with the forced vibration at the two operating

speeds for each of the two floor systems are shown in Figs. 10, 11, 12 and

13. Note that the mode shapes indicate that the floor systems acted like

large plates.

Rms acceleration levels. A, and relative phase angles, <p, of the floor system

response are shown in Figs. 14, 15, 16 and 17. Velocities and displacements

are tabulated along with accelerations and phase angles in Tables 1, 2, 3 and

4. During analysis of vibration data from the tests of the South floor, with

a machine web speed of approximately 117 feet/minute, it was found that accelerations measured at the reference location varied significantly between different tests. These differences are attributable to either a degredation of

the connection between the reference accelerometer and the floor since later

tests produced lower accelerations than earlier tests, or to slightly different

operating speeds since the machine stopped several times and had to be restarted

during the course of testing all the locations. Results presented in Table 3a

correspond to actual measurements, while values in Table 3b are corrected to

reflect the possibility that different machine speeds caused the observed differences.

The phase angles shown in Figs. 14, 15, 16 and 17 indicate that the vibration

propagates out from the middle of the span on which the perforator is located.

This is an indication that at the measured frequency the forced vibration induced by the machine was not precisely in resonance with the floor. Therefore,

it may be possible to generate a somewhat larger response than that observed

in the NBS tests.

3
The following determinations were made:

1. Natural frequencies of floor systems:

North floor (distinct 2 modes): 14.07 Hz and 17.97 Hz

South floor: 13.28 Hz and 19.0 Hz

2. Damping ratio for the south floor: 6 percent of critical damping.

A trace of the impact test is shown in Fig. 18.

The maximum values of accelerations, velocities and displacements are given

in Table 5. Maximum acceleration levels were evaluated against empirical

criteria for structural vibrations presented in Ref. [1) and shown in Fig.

17. In Fig. 19, circles denote accelerations for south floor locations and

squares denote north floor locations. Note that all vibrations are below

the threshold for "minor damage," and that the south floor vibrations are above the line indicating "damage very improbable." All maximum vibrations,

however, are above the threshold for "highly annoying vibrations" for work

areas. This fact is also corroborated by the perception of workers in the

area.

It should be noted that the thresholds in the chart in Fig. 18 are approximate,

at best, and should only be used to estimate probable effects.

Since the maximum vibrations are slightly above the threshold for possible

(though not probable) structural damage (2.5 mm/s or 0.1 in/s), a more com- plete analysis of vibration-induced stresses was conducted.

4.2. Analysis of Structural Effects

The procedure used to arrive at approximate vibration-induced stresses

is outlined herein.

a) The mode shapes obtained from the vibration analysis indicate that

the floor responded as a plate.

b) The mode shapes also provided an estimate of the size of the plate

engaged in the vibration.

c) The stiffness of the plate engaged in the vibration was approximated

using an orthrotropic plate analysis.

d) Using the maximum estimated deflection at the center of the plate

and the equivalent orthrotropic plate stiffness, equivalent static loads were calculated which would produce the same deflection.

e) Stresses induced in the girder and the reinforced concrete floor

section were calculated for the static and dynamic load components.

4
The following maximum stresses were calculated:

1. Steel girders: (Assuming Simply Supported Ends)

Static Component

Bending Shear

North Floor 12,395 psi 1,309 psi

South Floor 11,476 psi 1,317 psi

2. Concrete beams: North machine

Dynamic Component

Bending Shear

± 251 psi ± 15 psi

± 561 psi ± 39 psi

Concrete Compression

Reinforcing steel tension

Concrete shear

Static Component

497 psi

1,242 psi

56 psi

Dynamic Component

± 19 psi

± 48 psi

± 2 psi

South Machine

Static Component Dynamic Component

Concrete compression 574 psi ± 68 psi

Reinforcing steel tension 1,434 psi ±170 psi

Concrete shear 55 psi ± 4 psi

NOTE : Stresses were calculated for the working conditions observed, without

consideration of potential extreme loads for which the system was designed.

The calculated stresses can be compared with data on structural performance

under cyclic loads, such as ACI Committee 215 report. Ref. [21. It is reasonable to assume, on the basis of the Schmidt Hammer tests, that the concrete

construction is of high quality and the concrete strength (f 1 ) is at least

2500 psi; f^ probably exceeds 3000 psi. Thus, calculated stresses caused

by the static and dynamic load components are substantially less than the

allowable working stresses for the steel and concrete in the slabs. Data on fatigue strength of reinforced concrete. Ref. [1], indicate that it is unlikely

that the prevailing stresses could cause any structural damage to the concrete

slab.

The allowable stress in the steel girders used in accordance with Ref. [3] is

16,000 psi for static loads and 12,500 psi for "moving" loads. Even though

the data available at the time Ref. [3] was written were probably limited,

these allowable stresses seem conservative. The calculated combined static

and dynamic stresses induced in the steel girder were 12,646 psi and 12,037

psi for critical girders in the north and south floors, respectively. It

should be emphasized that these calculated stresses are quite conservative

since the beams are at least partially fixed at the ends. Partially fixing

the ends could lead to reductions of 30 to 50 percent in the stresses. Also,

the effects of the concrete topping and concrete encasement of the girders were neglected. It is unlikely that the expected stresses could cause structural damage to the steel girders.

5
5. Conclusions

On the basis of the data and analysis presented herein, it is unlikely

that the vibrations induced by the two new coiling machine perforators could cause any structural damage to the floor system and steel girders. The vibration level is, however, high enough to cause significant discomfort to

people working in the area.

The possibility of structural damage, as well as the discomfort to personnel

could be substantially reduced by avoiding the following operating speeds:

North machine : speeds between 115 and 130 ft/min and above 150 ft/min.

South machine : speeds between 110 and 125 ft/min and above 150 ft/min.

6. Recommendations

1) To ascertain that no structural deterioration occurs, particularly

in the vicinity of the concrete floor connection to the girder, it is recom- mended that periodic vibration tests be conducted. These tests should check the

natural frequency and damping of the floor system by placing an accelerometer

at the center of the floor spans where the perforators are located and compare

the data with values reported herein. A reasonable interval between successive

measurements could be one year, or such time that operators notice a change in

the critical machine speed.

2) It is suggested that in future purchases of new machines, forced

vibrations in the frequency range between 10 and 25 Hz be avoided, or appropriate measures be taken to reduce floor vibrations. It may also be possible

to stipulate that induced floor vibrations should not exceed those defined by

the "workshop" threshold in Fig. 17.

6
7. Acknowledgment

The work was performed by the Geotechnical Engineering Group of the

Structures Division of the Center for Building Technology. Mr. Jim

Woodward from the Bureau of Engraving and Printing supplied all the

technical data on the building and machines, as well as vibration mea- surements performed by the Bureau of Engraving and Printing, and marked

the locations for vibration measurements and Schmidt Hammer testing.

Mr. Erik Anderson of the Structures Division of the Center for Building

Technology performed and interpreted the Schmidt Hammer tests. Mr. Beverly

F. Payne of Mechanical Production, Metrology Division, of the Center for

Manufacturing Engineering checked the vibration analyzer of the Bureau

of Engraving and Printing and calibrated the accelerometers used in the

NBS tests.

7
8. References

[1] Rudder, F. F. , "Engineering Guidelines for the Analysis of TrafficInduced Vibration," Federal Highway Administration Report FHWA-RD78-166, Washington, D.C., February, 1978.

[2] ACI Committee 215, Consideration for Design of Concrete Structures

Subjected to Fatigue Loading, Journal of the American Concrete

Institute , March, 1974.

[3] Blakeley, George H., "Dimensions, Weights and Properties of Special

and Standard Structural Steel Shapes Manufactured by Bethlehem Steel

Company," Dando Printing and Publishing Co., Philadelphia, PA, 1907.

8
Table 1: Measured Accelerations and Estimated Velocities and Displacements

for the North Floor (Fig. 3) Response at 14.07 Hertz with Machine

Web Speed of Approximately 125 feet/minute.

Grid Point Phase RMS RMS RMS

Location Shift * Acceleration Velocity Displacement

(Row, Column) (Degrees) (q's) (inches/sec) (inches)

4, 7 -19 .007 .029 .33 x 10" 3

5, 7 -10 .007 .031 .35 x 10" 3

6, 3 - 5 .009 .039 .44 x 10“ 3

6, 5 0 .014 .061 .69 x 10' 3

7, 7 3 .009 .040 .46 x 10" 3

8, 5 5 .012 .051 .58 x 10" 3

9, 2 0 .004 .018 .20 x 10" 3

9, 6 3 .007 .030 .34 x 10" 3

9, 7 3 .004 .019 .22 x 10" 3

10, 5 - 5 .005 .020 .23 x 10" 3

11, 6 -14 .003 .014 .16 x 10" 3

12, 5 -25 .002 .009 .11 x 10" 3

* Relative to reference accelerometer location 6, 5.

9
Table 2: Measured Accelerations and Estimated Velocities and Displacements

for the North Floor (Fig. 4) Response at 17.97 Hertz with Machine

Web Speed of Approximately 155 feet/minute.

Grid Point Phase RMS RMS RMS

Location Shift * Acceleration Velocity Displacement

(Row, Column) (Deqrees) (g's) (inches/sec) (inches)

6, 3 -15 .005 .018 .16 x 10' 3

6, 5 0 .007 .025 .22 x 10" 3

7, 5 2 .012 .041 .36 x 10" 3

8, 3 -20 .010 .033 .29 x 10~ 3

LO

at 00 -13 .014 .049 .43 x 10" 3

9, 2 -31 .009 .032 .28 x 10" 3

9, 5 -27 .016 .053 .47 x 10' 3

9, 6 -27 .013 .045 .40 x 10" 3

10, 3 -43 .013 .045 .40 x 10' 3

10, 5 -41 .018 .061 .54 x 10" 3

10, 6 -42 .015 .052 .46 x 10" 3

10, 7 -45 .010 .035 .31 x 10" 3

12, 3 -55 .010 .034 .30 x 10“ 3

12, 5 -55 .013 .045 .40 x 10" 3

13, 5 -69 .009 .030 .26 x 10~ 3

* Relative to reference accelerometer location 6, 5..

10
Table 3a: Measured Accelerations and Estimated Velocities and Displacements

for the South Floor (Fig. 4) Response at 13.28 Hertz with Machine

Speed of Approximately 117 feet/minute.

Grid Point Phase RMS ** RMS RMS

Location Shift * Acceleration Velocity Displacement

(Row, Column) (Degrees) (g's) (inches/sec) (inches)

2, 4 -31 .012 .056 .67 x 10’ 3

3, 4 -27 .016 .073 .87 x 10“ 3

4, 4 -17 .019 .088 1.06 x 10’ 3

5, 6 -12 .016 .073 .88 x 10’ 3

5, 2 - 6 .012 .056 .67 x 10" 3

7, 6 - 7 .021 .096 1.16 x 10" 3

7, 5 - 5 .028 .127 1.53 x 10" 3

7, 4 0 .033 .153 1.83 x 10" 3

7, 2 - 1 .016 .076 .91 x 10" 3

8, 4 - 5 .030 .138 1.65 x 10" 3

9, 7 -13 .011 .051 .61 x 10" 3

9, 5 -10 .021 .098 1.17 x

10" 3

9, 4 - 8 .024 .112 1.35 x 10‘ 3

9, 3 - 8 .018 .082 .98 x 10" 3

9, 2 - 8 .011 .051 .61 x 10" 3

10, 4 -13 .021 .098 1.18 x 10

-3

11, 6 -19 .015 .068 .82 x 10" 3

11, 5 -19 .019 .086 1.03 x 10" 3

11, 4 -18 .019 .088 1.06 x 10' 3

11, 3 -17 .015 .067 .80 x 10' 3

11, 2 -19 .008 .038 .46 x 10" 3

12, 4 -23 .014 .067 .80 x 10" 3

13, 6 -32 .009 .040 .48 x 10" 3

13, 4 -29 .011 .051 .62 x 10~ 3

* Relative to reference accelerometer location 7, 4. ** Significant differences were observed between accelerations measured at the

reference accelerometer - probably due to small changes in machine speed due

to frequent stops and restarts of machine - corrections are applied in Table

3b to maintain constant acceleration levels at the reference accelerometer.

11
Table 3b: Corrected Accelerations and Corrected Estimates of Velocities

and Displacements for the South Floor (Fig. 4) Response at

13.28 Hertz with Machine Speed of Approximately 117 feet/

minute.

Grid Point Phase RMS RMS RMS

Location Shift * Acceleration Velocity Di splacement

(Row, Column) (Degrees) (g's) (inches/sec) (inches)

2, 4 -31 .015 .071 .85 x 10" 3

3, 4 -27 .020 .093 1.11 x 10~ 3

4, 4 -17 .025 .114 1.36 x 10" 3

5 , 6 -12 .020 .094 1.13 x 10' 3

5, 2 - 6 .013 .062 .74 x 10' 3

7, 6 - 7 .025 .115 1.38 x 10“ 3

7, 5 - 5 .031 .141 1.69 x 10“ 3

7, 4 0 .033 .153 1.83 x 10” 3

7, 2 - 1 .018 .084 1.00 x 10" 3

8, 4 - 5 .031 .143 1.73 x 10” 3

9, 7 -13 .012 .058 .69 x 10' 3

9, 5 -10 .024 .109 1.31 x 10' 3

9, 4 - 8 .024 .112 1.35 x 10" 3

9, 3 - 8 .020 .094 1.12 x 10' 3

9, 2 - 8 .012 .057 .69 x 10" 3

10, 4 -13 .022 .102 1.22 x 10“ 3

11, 6 -19 .016 .075 .90 x 10" 3

11, 5 -19 .021 .095 1.11 x 10

-3

11, 4 -18 .020 .092 1.10 x 10" 3

11, 3 -17 .016 .075 .89 x 10" 3

11, 2 -19 .009 .043 .51 x 10“ 3

12, 4 -23 .015 .072 .86 x 10“ 3

13, 6 -32 .009 .042 .51 x 10“ 3

13, 4 -29 .012 .054 .65 x 10" 3

* Relative to reference accelerometer location 7, 4.

12
Table 4: Measured Accelerations and Estimated Velocities and Displacements

for the South Floor (Fig. 5) Response at 18.75 Hertz with Machine

Web Speed of Approximately 160 feet/minute.

Grid Point

Location

Phase

Shift * RMS

Acceleration

RMS

Veloci ty

RMS

Di splacement

(Row, Column) (Degrees) (q's) (inches/sec) (inches)

4, 4 -62 .004 .015 .12 x 10" 3

7, 4 0 .011 .037 .32 x 10" 3

9, 4 -35 .014 .046 .39 x 10" 3

11, 4 -78 j .013 .043 .36 x 10“ 3

13, 4 -156 .010 .034 .29 x 10" 3

* Relative to reference accelerometer location 7, 4.

Table 5: Maximum Values of Accelerations, Velocities and Displacements.

FLOOR

Machine

Web Speed

(Feet/Minute)

Natural Freq.

of Floor Vib.

(Hertz)

Maximum RMS

Acceleration

(g's)

Maximum RMS

Velocity

(Inches/Sec)

Maximum RMS

Displacement

(Inches)

North 125 14.07 .014 .061 .69 x 10' 3

North 155 17.97 .018 .061 .54 x 10“ 3

South 117 13.28 .033 .153 1.83 x 10" 3

South 160 18.75 .014 .046 .39 x 10" 3

13
CALCULATED

DlSPLA

CEMEMT

-

/NCHES

X

IO

FIG. la: Estimated Vertical Floor Displacements

of #1 Coiler/Perforator (North Machine)

Provided by Bureau of Engraving and

Printing Personnel

.

14
RATIO

OF

PEAK.

ACCELERATIONS

ZO

li. ° d si

2 , ulo0

w

oc

IS -

/(.

O - sooth machine

- NORTH MACHINE.

uh O i2 5

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« 0

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/ / / / /

/ / / / / /

/ /

/ /

& ^ - sooth Floor location 7.m i \ O - SOUTH FLOOR LOCATION II. H

1 \ - NORTH FLOOR LOCATION fc. S

j N - NORTH FLOOR LOCATION A.S ( O'

.-GX !

:Bv G

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/ GT * , 0

'

O L J_ JL _i_ /oo no 12.0 1 30 /NO /SO

MACHINE WEB SPEED - F PNA

/60 / 70 /SO

FIG. lb: Relative Peak Accelerations of Primary Frequency

of Floor Vibrations and Primary Frequency as a Function of Machine Web Speed.

15
FIG. 2: Schematic Drawing of Typical

Floor System Segment.

16
fcHID

COLUMN

NUMBERS

SOUTH

FIG. 3: Grid of Test Points (Dots indicate grid points).

17
SAID ROW

“unetRi

1

ORID COUUHtl KIUMBRRS

6 7

IZ3t57

A

A IzHi7

• GRID POINTS

A A ACCELCROMCTER

DATA LOCATIOMi

FIG. 4: Locations at which Vibration Data were

Taken on North Floor with Machine Web

Speed of 125 Feet/Minute.

18
&Rit> ROW j z

OR ID COLUHt)

3 H

NUM8CRS

5 t 7

WUH1UU

t /*wj_ •

•

• • • • • • IZH37

2 • • • •

3 « • •

/3z£7l • « • 1/3157

• &R\D POI*OTS

£ ACCELEROMETER

data LOCATIOMS

FIG. 5: Locations at which Vibration Data were

Taken on North Floor with Machine Web

Speed of 155 Feet/Minute.

19
/*?*/

GRID COLUMN NUMIER5

7 £ 5 V 3 2 1

• • I ZEE7

• • A7*/ X

• A I ZEE

A GRID POIWTS

A Accelerometer

data LOCATIONS

A

/3&o_y J

Column) WUH6ERS FROM STRUCTURAL

DRAWIMG£

/=6M/

J

A

m • A

A

A

A • I ZEE

X ZEE

FIG. 6: Locations at which Vibration Data were

Taken on South Floor with Machine Web

Speed of 117 Feet/Minute.

GRID ROW

NOMfcERi

1

z

3

S

b

7

6

9

10

II

12.

1 3

20
GRID COLUMN NUMBERS

7 6 S </ 3 2. 1 /*72./ J •• • • • **! /3 7 //

I

• frRio points

A ACCELEROMETER

data locations

COLUMN NUMBERS FROM STRUCTURAL

DRAWINGS

Zizy’

• ^/36 s/

FIG. 7: Locations at which Vibration Data were

Taken on South Floor with Machine Web

Speed of 160 Feet/Minute.

GRID ROW NUMBERS

1

z

3

H

5

6

7

6

9

10

II

12.

1 3

21
A SPEC l Rii 62 #A< 20

A SPEC 2 R#i 63 #Ai 20

FIG. 8: Typical Power Spectra at Two Points

Indicating Relative Magnitudes of

Accelerations.

22
Xi 13.281 Y* -30. 676 HARMONIC

A SPEC 1 R#i 62 #Ai 20

FIG. 9; Log-Plot of Typical Auto Spectrum with

Resonant Frequency and Harmonics Identified.

23
FIG. 10: Mode Shape of North Floor Vibration

at 14.07 Hertz with Machine Web

Speed of 125 Feet/Minute.

24

W

/

3

JT7

/3T37

ZH57
FIG. 11: Mode Shape of North Floor Vibration

at 17.97 Hertz with Machine Web

Speed of 155 Feet/Minute.

25
FIG. 12: Mode Shape of South Floor Vibration

at 13.28 Hertz with Machine Web

Speed of 117 Feet/Minute.

26
FIG. 13: Mode Shape of South Floor Vibration

at 18.75 Hertz with Machine Web

Speed of 160 Feet/Minute.

27
C*IO SOW

1

6*>D COLUMk) MU

6 7

i s i s

i IZS57

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sr

i

A $

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A » . ool

^

, (>: S°

A = . 0 i 2. <j A A

<t>= 3° 3"

A = .007^ A = . 004<j

A

A * . 005 ^

A = . 003 ^ A $ = - 2.s“ A = .002. ^

J /5Tt7

CW-OHkJ MVnecJlS

**»•« »T«.\iC-IU«At. PUlWNtl

FIG. 14: Acceleration Data and Phase Relationships for North Floor Vibrations with

Machine Web Speed of 125 Feet/Minute.

28
GRID ROW | Minuti

1 /J2&X

2

H

* A^I

t

7

a

’ AWj

/o

//

/t

GKID CO\_OM fc) NUHQIRR

* * •< 5 t 7

1^57

I/D57

$

= - ,s

° A <$?= 0

° A = .oos^ A = . 007 3

. A *

- A - . 0 1 2 <3 A A 4> * -13*

A = -OIO

3 A= . o»M

3 A 4> - - 3 ' ° A A 4> - -2-7» J/T777

A = . 009 3 27" A = 0,3 > /

A = . Olfe^

c~- columio uuiweO

$ = -W3° A 4>: -HI 0 A A

FROM ITVKIVMl

A 4

1 " OMun^i

A- .Ol 3 * A = . O 18 3 ^-H2° s

A = . O IS 3

A

A = .010

A 4>A =

= .013

- S5‘

3 / 3 A ct> - - 69 * A = ,001 3

FIG. 15: Acceleration Data and Phase Relationships for North Floor Vibrations with

Machine Web Speed of 155 Feet/Minute.

29
C-R.ID COLUMN NUMBERS

zhp7 ]

7 & 5 U 3 2. 1 6 *>o *°* NUMBERS

I ZH7 i

A $

= - 3.

° z A 6 . O l 5 ^ A 4> - -2i * 3

A - . 0 2.0 <j A 4 a - 17 ° H A * . OZS

^

ZIz±7 J A <t>= -i2° a J

/I777 *

ft ! .020 j ($>*-<,“

As .013

^ 6

4>s-7* A A A 4

>s o* A 4> = - 1 • 7

A - . 02 S'

^ A = , 033 g A - .0.8

; ft-.Oll

) A <4> = - s°

a * = .031 }

/3So/ jT A A AAA T /W 9 4 - -13° 4>= -io° 4> = - a* <t> - - a* 4>= - a* / A = .012} A = . 02 H

y As ,02H

j As ,020j A = • 0 )2 y COLUMN WUMBERJ FROM £TR UCTURAL ^ 4

-- -13° 10 DRAVUIM&&

<*-- -IV ^

A = .022 j

(

A AAA (*> -- -11° ii \ 4>= -n° $ = -.7° A = . 00°l y

) A = .02.1 J A s . OZOy A: .016 ^

/

- ^ 4> = - 23° IZ

/

A= . OlS j. J A <$, s - 32° A <t> * - A*!' X /^7 1 3 A = ,oo<l ^ A - .012^.

FIG. 16: Corrected Acceleration Data and Phase

Relationships for South Floor Vibrations

with Machine Web Speed of 117 Feet/Minute.

30
GRID COLUMN NUMBERS

zmp I

~7 6 S V 3 2 1

&*>«> NONIMRS

X ZEZT7 1

2

3

ZHE7 J

A <t> = -fe^° * A = . ooM ^ I /HE7 s

6

A <J> - 0° 7

8

/a*°S J A 4> = -3 S° ”|~ /371/ «» A-.o.S^ - -

COLUMN NUMBERS FROM STRUCTURAL

DRAWIN&S

“7

10

A « -78° u

*- -°' 3 J

li

/H37 J A <J> = -/St* T /38s/ /

3

A = .oio

^

FIG. 17: Acceleration Data and Phase Relationships for South Floor Vibrations with

Machine Web Speed of 160 Feet/Minute.

31
FIG. 18: Strip Chart Records of Acceleration

Traces From Impact Tests at Locations

7, 4.

32
- SOUTH MACHINE.

“ Worth machine

FIG. 19: Comparison of Maximum Measured Accelerations

Against Empirical Criteria for Structural

Vibrations Suggested in Reference 1.

33

APPENDIX A

MEMORANDUM FOR THE RECORDS OF THE INVESTIGATION OF MACHINE VIBRATIONS AT

THE BUREAU OF ENGRAVING AND PRINTING

From: Felix Y. Yokel and Erik Anderson

Geotechnical Engineering Group, 741.05

Subject: Investigation of Concrete Strength by Schmidt Rebound Hammer

General

The investigation was carried out on December 17, 1981. Tests were made

on the underside of the concrete joist of the first floor near the joist

supports. Test locations are shown in the attached sketch. The test locations are identified in the sketch by numbers 1 through 7. Column locations are identified by their reference numbers in the construction plans.

The concrete surfaces where tests were conducted were cleaned by the Bureau

of Engraving and Printing personnel with a wire brush in order to remove whitewash and dirt

.

Test Results:

369

I,

i

i i

I

365 7 6

370

i ^

i i i

i

371

I

I

i

372

i i i if i i t i i i

I I I I I I I I l I l l I I

i i i i i i

i 1

1

t

5

I

366

i i

I I

367

i i i

i i ' '

1 2 3

I

368

Note: Numbers denote column locations designated

in the building plans.

Test Location 1 2 3 4 5 6 7

39 47 36 38 39 45 53

39 40 25 38 42 45 48

Hammer

Readings 39 37 25 38 40 46 44

39 45 33 36 40 36 42

39 39 31 41 40 42 38

40 24 35 37 42 43

Avg. Reading 39 42 29 38 40 43 45

l
APPENDIX A

(Cont ’ d)

Approximate Concrete Strength, PSI

Test Location

1

2

3

4

5

6

7

Approximate Concrete Strength for

f' = 3,800

c

1 /

Approximately f^, psi

3,800 ± 4,200 ± 1,260 ± 3,300 ± 3,900 ± 4,500 ± 5,100 ±

Average of All 41 Readings :

1 / Strengths were calculated in accordance with calibration curves

of the manufacturer.

2 / Even though numerous investigations have shown that there is a correlation between compressive strength of concrete and rebound

readings, there is considerable disagreement on the accuracy of

prediction (refer to NBSIR 80-2163, "Nondestructive Evaluation

Methods for Quality Acceptance of Hardened Concrete in Structures,"

by James R. Clifton and Erik D. Anderson). Mitchel and Hoagland

(Highway Research Bulletin 305, 1961) found that the difference

between estimated strengths based on rebound readings and measured

concrete strengths averaged 18.8% under controlled conditions.

Hammer readings are affected by smoothness of surface, moisture

content of concrete, type of coarse aggregate, rigidity of specimen, and carbonation of the concrete surface.

2
NBS-114A (REV. 2 -ac) U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

1. PUBLICATION OR

REPORT NO.

2. Performing Organ. Report No. 3. Publication Date

SHEET (See instructions) NBSIR 82-2599 December 1982

4. TITLE AND SUBTITLE

Investigation of Floor Vibrations in the M D" Wing of the Main Building of the

Bureau of Engraving and Printing

5. AUTHOR(S)

T. A. Reinhold, F. Y. Yokel and F. F. Rudder

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8. Type of Report & Period Covered

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

Structures Division

Center for Building Technology

National Bureau of Standards

Washington, D.C. 20234

10.

SUPPLEMENTARY NOTES

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

11.

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

bibliography or literature survey, mention it here)

Floor vibrations induced in a Bureau of Engraving and Printing building by a recently-installed perforator were investigated by measuring relative acceleration amplitudes and phase relationships between a reference position and points

on a grid laid out on the affected floor. From these measurements, it was possible to determine mode shapes, resonant frequencies and displacement amplitudes.

On the basis of the displacement amplitudes, anticipated cyclic stresses in the

structural system were estimated. The results of the measurements and analysis were compared with existing data on vibration-induced structural damage and fatigue

strength of steel and reinforced concrete. Damping ratios were also determined

in a separate test, in order to ascertain at later dates whether any structural

deterioration is taking place.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s)

cyclic strength; fatigue; floor vibrations; machine foundations;

steel; structural engineering

13. AVAILABILITY

J^Cj Uni imited

reinforced concrete;

14. NO. OF

PRINTED PAGES

| | For Official Distribution. Do Not Release to NTIS

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

38

15. Price

[y~| Order From National Technical Information Service (NTIS), Springfield, VA. 22161 $7.50

USCOMM-DC 6043-P80