Experimental vibration studies were conducted on two houses to determine some of the dynamic response characteristics, resulting from sonic boom. The primary objectives of the vibration tests were to identify the mode shapes associated with the various frequencies determined from the sonic boom response data, and to obtain some basic information about the vibration behavior of buildings in general. The results are presented of forced sinusoidal vibration studies of some components of the test structures. Included are acceleration response data on selected walls, wall surface modal patterns, and vibration induced noise measurements at various locations in the test structures

Carden, H. D.

Mayes, W. H.

English

NASA Technical Reports Server

N A S A  TECHNICAL 
MEMORANDUM 
(NASA-TR-X-72705) 5 X P E P I f l B U T A L  F O F C E D  N75-24748 
v, V I B P A T I O N  RESPONSES O F  TEST HOUSZS DUFIBG 
THE EDGJlRDS AIR P 9 R C F  BASE PHISE OF THE 
NATIONAL S O N I C  BOOPI TEST PSOGSAY (NASA) 
Uncl as 19 p HC $3.25 
CSCL 1313 63/07 Lo399 x 
4 
m 
e EXPERIMENTAL FORCED VIBRATION RESPONSES 
OF T W  
z TEST HOUSES USED DURING THE EMJARDS AIR FORCE BASE PHASE 
OF THE NATIONAL SONIC BOOn TEST PROGRAM 
by 
Huey D. Carden and W i l l i a m  H. Mayes 
June 1975 
This Intmal  documentation medium is used to provids accelsreted or 
special roleme of technical intDrrmtlm to selected users. The cot?tents 
~y not meet NASA formal edlting and publication standards, m y  be re- 
v l rd ,  or may bw incorporated in another publication. 
WATWAL AERONAUTICS AM SPACE AIMSIIIISIU'I)(NI 
U W  RESEARCH CENTER,.-, VlR6lM 23665 
https://ntrs.nasa.gov/search.jsp?R=19750016676 2020-03-22T21:58:50+00:00Z
TM X 72705 I 
4. rd Experimenta I t orcea v i ~ r a t i o n  uesponSes s. m o , m  
o f  Two Test Houses Used During the Edwards AFB Phase of June 1975 
the National Sonic Boan Test Program 6 . ~ 0 t ~ ~ u i a a ~  
! Huey D. Carden and W i  11 iam H. Mayes 
, 10. w d  Unit No. 
W-eDCliariorr)krnd#or 
NASA Langley Research Center S n 5 - R ? 3 2 e n G  
Hampton, VA 23665 i. b r a r c ~ C m N 0 .  
I 
'2. ~ l y l r y ( Y w m d A d b r r  
National Aeronautics and Space Administration 
Washington, D. C. 20546 
I This information was published i n  an informal document i n  1969. No attempt i s  made t o  update t h i s  material t o  r e f l e c t  the current state of the a r t .  i i 
- - - - 
16. -ae f I 
Experimental v ibra t ion studies were conducted oil two houses t o  determine some 
of the dynamic response characterist ics, resl l t ing from sonic boom. The primary 
objectives o f  the v ibra t ion tes ts  were t o  i den t i f y  the mode shapes associated I 
with the various frequencies determined from the sonic boom response data, 4 
and t o  obtain some basic information about the v ibrat ion behavior of buildings f 
i n  general. 
This paper presents the resul t s  o f  forced s i  nusoidal v ibra t ion studies of 
some components o f  the t es t  structures. Included are acceleration response 
data on selected walls, wal l  surface modal patterns, and v ibra t ion induced 
noise measurements a t  various locations i n  the t es t  structure5. 
17. Kw Wab (n bv k ( s ) )  (STAR ~npoly u-ind) 18. D ' i h n i  Soamm I 
Sonic boom, acoustics, st ructural  Unclassified - Unl i m i  ted 
I 
I 10. Scuitv 'f. (of cha p l C I  j 1 Unclassified I Uncl ass4 f i ed 17 1 
( T M  WItmrf Taftniul lntomwlm Suviu, SpinptuM. Vntinrr 22151 
*A".YO* from 1 
SflF mAS* Scirrlif'u md Techiiol Intamtion f r i l i ty .  P.O. Box 33. Colt##@ PrL. MD 20740 
By Huey D. Carden and W i l l i a m  H. Sayes 
Ik~rinf: the National Sonic Boan Ted. Program cmduct,.,+l a t  Mwarris 
ltir Force Haze, California, experh~t.d vibration s t u d k c  wem conducted 
to deternine some of the dynamic response characteristic:: ~ b f  the two 
houses used in the &rogram. The primary objectives or' ti:r vii;trztion 
t e s t s  were t o  identify the mode shapes a:;sociated with tht- vnrie~:: 
frequencies determined fran the sonic boom resportre doxa (reference; 1 
and 2), an.3 t o  obtain cone basic iit'omatiori about the vib.-ation iichavior 
of buildicgs fn general. 
This paper presents the results  of' forctd sinllisoidd tibratior, 
studies of sane components of the test str'rtctures. Includea .arc accefe- 
ration response data on se?_ected walls, wall surface m d a l  pa t t c rn~ ,  and 
vibratim induced noise meazurenents at  variaus 1ocat.iori. ' 1 3  ?fie t e A  
structcres . 
WARATUS liWD TEST PR@CEDURE 
T e s t  Structures 
The test structures were two precut residence type ha:ser; c ~ f  
conventional framt construction t ha t  wert: ercc tt-d :it thz Fduanl:: Air 
Force Base, California, by m Air Force contrsctor. The stnlctures, 
shown in figure 1, were in an area containing about ten other residences. 
Test structure 1Jo. 1 cm the lef't was a single-fjtorythree bedrwrn hmse 
whereas t e s t  structure Ho. 2 oa the rigttt vas a t v # ~ t o r y  fou~&edroom 
hmse. Both hauses e r e  finished insidi? and at, were appropriately 
furnished, and w e r e  instrumented with microphones, accelerometers, and 
strain ewes. I n  the vibration tes t s ,  only the accelerometers and 
microphones were used f m  the instruments available. 
Instrumentation 
A permanent nagnet shaker, capable of 2 maximum vector iuce or' 
2'5 pcunb, was used t o  excite the vibratory responses cf the test 
houses. The shaker was attached t o  either the walls or *loors of the 
stmctures with a vacuum plate attachment, The oscillator signd us& 
t o  drgve the shaker was also applied t o  the horizontal trace of an 
oscilloscope and t o  a freriuency-period counter. A crystal  accelermett-:r 
was attached t o  the wal ls  of the building and the outpst uas rippUed tc 
the vertical trace of the oscilloscope. The pattern rcferrvd t . 1  az 3. 
n Lissajausn figure that resulted on the oscilloscope was used t o  
determine a resonant condition. A hand-held velocity proLc was u.-ed t c l  
survey the structure t o  determine nodal locations for deftnine m c d e  
sh q e s  . 
For the forced vibration response phase of the vibration tests, 
existing instnunentation f o r  the sonic boom program i n  both houses was 
used for  recording structural responses. 
Test Procedure 
!Rxe same tes t  procedure was used for al;L the vibration survey t e s t  6 .  
Wall sectfans or floors of the test structures were excited with the 
permanent nagnet shaker to  determine the natural frequencies and mode 
shapes. Approximate frequencies determined f'rom available sonic boan 
records (references 1 and 2) were used t o  slarrav the frequency hand of 
interest in searcidng fol a resontint condition. A cryzit&. accelercmeter 
wac placed on the vaU or floor and the drixtng freq~ency varied untif 
the  resonant cmdition was established. The nodal lines *-?re then 
traced by moviw a hand-held velocity probe over the w d 1 s ,  cc ing, 
and floors throughout the Lest house. 
Aftzr campletion of the vibration modal sitrveys, t l t ~  t=esponsc of 
t.he building as measured by the various instruments 1 ocate.1 t;t?mu;:h:hcn:t 
the building was recorded on FM tape. In  these test:;, strri~+~ire No. 1 
and structure lio. 2 were excited at  sinusoidaf force Icvelz of 1t5, 12, 
and 8 pounds force peak t o  peak. 
RESULTS AND DISCUSSION 
Results o? on s i t e  experimental vibrat im studies of two sonit t)om, 
t e s t  houses a t  Mvards A i r  Force Base, California, are pre;cntcci in 
figures 2 t o  7. Included in the results are mdes, frequenc:ies, a d  
forced vibration responses of the t e s t  structures. 
Vibration Data for $tructum 80. 1 
Present& in figure 2 are typical weI.2 and floor sfceferatim 
responses ead the essacfated satnd pressure lwels (noise) i n  bedroota 
No. 1 of the ane-etory test &ntcture (see floor plan sketch). - The 
mults are for  B constant force excitation af the be- wa l l .  The 
data indicate that at l o w  frequencies, maid&T~oor motions contribute 
t o  the samd pre~sure  envlm~lent  *as the higher frequencies from 
the w a l l  motions contribute t o  the twaer frequency portion of t h e  sautd 
pressure spectrum in the roam. 
Rcperirrrentally detezmctned modes and frequencies of port ims of 
house No. 1 are presented in figure 3. Pmm si?usoidal excitnt' on of 
the east bedmat w a l l ,  the f i r s t  resonance occurred a t  16.6 112. Thc 
associated mode was a diaphragm mation with nodes at the edces of the 
w a l l .  Further velocity probe surveys of auacent w a l l s ,  floors, and 
ceilings, and adjoining roans revealed that a major porti.011 of the  north 
end of the structure was vibrating as i l l~ l s t r a t ed  by the sketches i n  
fitgure 3. Although the north beCrom w o r t  and floor had r e s c n a n t  frequen- 
cies of 21.4 Hz and 26.0 Hz, respectively, the mode shapes weye readily 
determined by exciting the east w a l l .  Conversely, by exciting the nort? 
wall or floor, one could determine the other modal patterns as w e U .  
Thus, t he  mcde surveys revealed that  what appeared t o  be a fundamental 
wall mcde of a room was actually part of the overall house or bu5-lding 
m d a l  behavior as  indicated i n  figure 3. 
hspanses of the bedroaa Ro. 1 floor and east woll as a resuft 
of s d c  boars excit&im (see reference 1) indicated thct the bedroan 
floor and east wPU r e ~ d e d  a t  about 21 HZ md 16 ~ z ,  respectively, 
wMch agrees wAJ. -th the frequencies deteneined by sinusoidal excita- 
Vibration Dato for Structure No. 2 
.. f , 
Ijtmcturcrf vibration data and associnttd sound pressure levels 
(noise) for thc twa-story house are presented in figure jk(u) ru~d 4(?3). 
I n  tilyre &(a), accelerztion recpuncc i n  C* of various lw~ticrns i r l  thy 
tuo-story hwsc are plotted as a function of the excitation force. The 
top curve i n  f ipre  4(a) is referenced t o  1g xms, t h e  P o t t a n  cl,fire t o  
.u>e nus. The excitation freqrlency i s  21.2 Hz, the rcr;c,n;irif, frequenes 
of the dining room w a l l .  The data s p b ~ l s  arc k e ~ e d  to the locat  ion or 
t hz  measurement in the building and arc show in the ,ketch of' the floor 
plan a t  the right of the figure. For iristmce, tht circlcti :PC ?or 3. 
Loc&t,ion on the eest dining room wall near t h e  icput  forcc, the squeres 
are for th2 north bedroom wall upstairs, the trianelcs at-o for tli.:: 
kitchen floor, and the diamonds are for  the loeat ion in t,hc center cf 
the dining room floor. 
The significance of the data ic that the ilccelerati~~nc far  a l l  01' 
t he  locations appear t o  be linear with input force level, at ;t-ri,t for 
the range of input forces used i n  the tes ts .  In adtiit;iu~i, : I , ;  d a t a  
indicate that l a w  force levels a t  a point arc capable Ir:iiucir.,- !,espcn~;cc; 
virtually throughcut the entire huildirti; i n  n linear ~.-c:;pt ~ I I  .. B-:~r i  - - :it 
levels colaparable t o  those resulting f ~ o a  sonic boom t:xci?,aii~rn (:c:t'. L). 
Figve 4(b) presents tho suund pressure level: (nols~f rcrst~ftbg 
from the excitafioc of the -8 rour~ east MiLl at 21.2 Ez. ;G In thc 
case vith tbe acceleration responses, the data appear t o  he Iltenr in 
the ran* cjf iriput forces used md range fran 9rJ t c t  Y2 elB nctw Lhc 
source t o  70 dB at t i l x ~ t  20 t o  25 feet away ~II the center of t ! ~ e  l'id2:il.y 
m m *  
It  say be n e e d  tnstt the levels in the upstairo ll:aitm tiipectxy 
<,-rer the dining area are carrgmchfe t o  those fn the dining w. a .  %%is 
rosult c= Se pa4ially explnin~ci with the &id of figure 3 uhit:ia pr.c;;~ti;.c 
the building response modes for only part. of the b ~ i l d i r , t < .  Tl:~.se :t,rxtttl 
patterns are s s l a r  t o  those presented in figure 3 far ~ I I X ~ S C  ii3. f,, 
indicated on figure 3 ,  t h e  north bedroan w a l l ,  tito bzdrom r.~nc>r {dini:~;: 
room ceiling), and the other wFiLls (no mdes shown) were v i b ~ a l i n y :  i n  the 
fundamental motion as a result of the excitation of the d in- i !~ , ,  rc~m wail - 
thus one would perhaps expect the noise levels to 'oc cclmparaillc i n  thu;e 
two roorns. 
Resonant frequencies c,P tilts varicrus areus of the tu~-st ; i~ry mLiding 
were 21.4 Ez for the north dining w d l ,  21.2 Hz for the cus t g a l l ,  
and 21 Hz for the floor. For the l iv ing r o a ,  the freqteneics wcre 
22.2 E! for the east w a l l ,  ma 26.9 Ez for the south wri l ; .  
Frar. analyses of the response data from the scnic hc,m studies 
(reference 1 and 2), it was noted that low rtmplit~de, 1iip)icrr f rcqticrlcy 
harmonic sign6tl~ were often superhnpos& on the lwer r rcqttcnzy :: f , f ~ k t t , i 3 ~ ' : i l  
rcqongcs. fXlrine the modal vihrati~.,n ;:!inv .: tert.;;, %he $:.;I.: ecrc fit' t i r .2  
higher frequency responses were f mnd t r t  h e  h i r.fi f rcqueni-y i t a ~ i r ? . I  :nuit- 6 
sitPilar t o  the panel mode at 405 Hz on the eas t  dining roan and bedroan 
wall shown in fiere 5. ! lWs  mode, for example, had a fill wave length 
between t h e  rell studs Li t h e  horizontal d i rec t ion and 5 nodes vertically 
fnra t he  floor of the dining r o w  t o  the cei l ing  of the  upsta i rs  bedroan. 
Structural Interaztion 
- . '  - 
Frun t h e  modal data  determined fo r  t h e  two test huuses, strong 
interact ions were faund i n  the dynamic response pat terns  of floor, w a l l ,  
and ce i l ing  components- These interact ions,  which may involve both tfie 
s t r u ~ t u r e  and t h e  trapped a i r  in t h e  :*oans, remlted i n  preferred medal 
patterns involving not only adjacent components, but also those located 
remotely from each other. F i , w e  7 illustrates t h i s  interactfng behavior 
for  both s t ructure  Ho. 1 and No. 2. The sketch on the  lef t  i l lustratec  
t h e  interact ion f o r  floor vibrations (also indicat ive of v d l s  and 
ceil ings)  in  the  on+story house. The sketch on t h e  riitfit i l l u s t r a t e s  
the  interact ion of t h e  vibrat ions between s to r i es  in the  %wc-story house. 
The resu l t s  frw the  sinusoidal vibrat ion tes ts  indicsted that tfic 
fundamental na tura l  frequencies (or first maximum rrespcmcec) of the  
various w a U  and floor sections were in a re la t ive ly  nni-row frequency 
band between 13 Hz and 30 Hz. Thus, &en a particular sectict~t war; vibrated 
a t  i t r  f u l l m e n t a l  or maximum response, strong vibrations of t he  various 
other h m ~ e  sections occurred because o f  the  cloceness of tht . lr  resonar&. 
frequencies t o  the  one being excited. I n  the lef't hand sketch .:f fikyre 'f 
mainly s t ructura l  interacticm is  responsible f o r  the ad<jacent family roam 
vibrations whereas in the  r ight  hand sketch both s tmctura l  and a i r  c a v i t y  
interact ions seem t o  be indicated. These results suggest same of the 
phertmenu invalved i n  the  dynamic rcsponcc ~ l f  a hast: %ype :ztructure, 
vhen excited a t  a single point. Pest reqmses me cinflar t o  those 
masurer2 during sonic born excitat ion (reference 2) for which the bpnt 
loading w a s  distr ibuted,  traneient i n  nature, and Impinged on rill &ernaL 
sur~'aces of t h e  hause. 
Farced excitation results for two different; house; indicated 
qc.nerd3.y siailar dynamic respunzm f t i ~ .  ghicn thcrs: WCL'L. .;tr13n~: i f i L c ~ -  
actions betwecn the f loor,  wall, and c e ~ f i n g  c m o n c n t s .  These 
interact ions which may involve both ttic. s t ructure  and t h e  trapped a i r  i n  
t h e  roans resulted i n  preferred modal pattex involving not  only 
adjacent ccmponents, but a l so  those locateil remotely f i*cxn eilch nther.  
The f a c t  that; the fundamental frequencies associated wi t l :  the framing of 
the  s t ructure  occur i n  a ra the r  narrow frequency range ( ~ j  t o  30 HZ) 
a*hences t h e  above interaction. 
The higher frequency responses 01' the  hauses wcre ascocinted with 
t h e  i n t e r i o r  sheathing panels and the  r a g e  of panel f r e q ~ c n c i c t ;  was about 
an order of magnitude hiaer than tlt.ose of' the frames. 
The measured responses were n&cd t o  be 1il;car for the rclnac of force 
inputs of these tests and the resu l t s  were generally cr?nsi:,tcnt with those 
previwsly obtained during aircraf% sonic boom and f lyover  rtoise studies.  
1. Ffndlsy, b n a l d  8.; Huckel, Vera; and Ifenderson, Herbert R.: 
VibmtOon Respoa8@s of Test 8tr~cture fOo. 1 Ihring the Eclw3XYie 
Alr Force Base Ptrase of the Hatianal Sonic b u n  propsi.  EASA 
TMx 72706, Junc 1ms- 
2. Fhdley ,  RmaU 6.; IIuckel, Vera; and Hubbard, Harvey H. : Vibration 
Respanses of Test Structure 80. 2 k i n g  the Edwardf: Air Force Bscc 
Phase of $he Bletional Sonic Boopi Program. aASA 2?4X 72704, June 1975. 

Vibration i n d d  noise 
Figure 2. - Rezporiir of tell. h ~ u c e  II,. 1 as 3 f i i n r t i o n  of eri:ta'.ion f re~denc) . .  
Constant i n p i t  force. 








Experimental forced vibration responses of test houses during the Edwards Air Force Base phase of the national sonic boom test program

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