11
h
In e na ional Con e ence on Vib a ion P oblems
Z. Dimi o o á e al. (eds.)
Lisbon, Po ugal, 9-12 Sep embe 2013
SEISMIC TESTING OF LARGE SCALE STRUCTURES WITH
DISSIPATOR DEVICES
Bea iz Zapico*
1
, José L. Zapico
2
, F ancisco J. Molina
3
1
ARUP B.V. Ams e dam, The Ne he lands
Bea iz.za[email p o ec ed]
2
Depa men o Cons uc ion and Manu ac u ing Enginee ing, Uni e si y o O iedo, Gijon, Spain
jza[email p o ec ed]
3
ELSA Lab, JRC, Eu opean Commission, Isp a, I aly
ancisc[email p o ec ed].eu opa.eu
Keywo ds: seismic es ing, pseudo-dynamic me hod, dissipa i e de ices, ull scale models,
s ain a e e ec , Neu al Ne wo ks
Abs ac . Seismic es ing o la ge-size models is nowadays possible hanks o he pseudo-
dynamic (PsD) me hod, which esembles a quasi-s a ic me hod wi h he applica ion o slowly
a ying o ces o he es s uc u e. Low es ing eloci y may change he beha iou o he ma-
e ials wi h espec o hei beha iou a eal eloci y due o s ain a e e ec (SRE). The SRE
du ing a PsD es is no ele an o he classical cons uc ion ma e ials. Howe e , i can be
e y impo an o some new ma e ials, such as ubbe o silicon, mos ly used in isola o s o
ene gy dissipa i e de ices. Silicone luid iscous dampe s a e an example o hese dissipa i e
de ices, and hey will be he subjec o his pape . I is possible o ex end he PsD me hod
ange o applica ion o s uc u es equipped wi h dissipa i e de ices by in oducing a co ec-
ion echnique (CT) de eloped by he Eu opean Labo a o y o S uc u al Assessmen (Eu o-
pean Commission) in Isp a, I aly. This echnique consis s o an on-line linea modi ica ion o
he es o ing measu ed o ces. In his pape , wo new p ocedu es o CT a e p oposed. The
i s p ocedu e consis s o a linea il e whe e he ou pu is he co ec ed o ce and he inpu s
a e he measu ed o ces and displacemen s. The second p ocedu e is based on neu al ne -
wo ks, using he same inpu bu adding he es eloci y a e. Fi s , he mos app op ia e
scheme o he algo i hms was selec ed and calib a ed. This is based on expe imen al da a ob-
ained by dynamically es ing he dissipa ion de ices wi h a displacemen pa e n, which was
speci ically designed o his pu pose, a di e en equencies and es eloci ies. Then, he
capabili y o he ob ained il e /ne is es ed using expe imen al da a. Addi ionally, he mos
app op ia e equency o he aining es s was s udied. Ou comes we e success ul. Bo h al-
go i hms ou pe o m he p e ious linea CT, he ne -based one being he mos accu a e and
e sa ile. I was ound ha he i s na u al equency o he unp o ec ed s uc u e is an ade-
qua e e e ence o he aining es s.
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
2
1 INTRODUCTION
Seismic design is a ela i ely new concep in he his o y o enginee ing. I consis s in di -
e en s a egies o designing ea hquake esis ing buildings o ensu e he heal h, sa e y and
secu i y o he building occupan s and asse s. Some o hose s a egies can be g ouped unde
he name o s uc u al p o ec ion, measu es aken o enhance he esponse o a building unde
a seismic load. S uc u al p o ec ion can be planed du ing he design o he building, o a e i
– o example in his o ical buildings. I can be di ided in o h ee main g oups: base isola ion,
passi e sys ems, and ac i e sys ems. This pape is ocused on he passi e p o ec ion sys ems,
in pa icula on luid iscous silicon based de ices (FVD). They ha e he ad an age o being
easily implemen ed in an exis en s uc u e and no needing an ex e nal powe supply.
No ma i e ega ding seismic design and hence s uc u al p o ec ion has expe ienced a as
e olu ion in he las cen u y. Wi h each new ea hquake new codes ha e been implemen ed
and new philosophies ha e been de eloped, om he addi ion o an equi alen la e al load in
he s a ic s udy o he pe o mance based design. Acco ding o he la e endency, he e-
sponse o he buildings unde an ea hquake canno be assumed bu needs o be obse ed, and
es s ge a i s line posi ion in he c ea ion o new codes o he alida ion o new cons uc i e
me hods.
A well-known me hod o seismic es ing o s uc u es is he shaking able, mainly used o
he es ing o small-scale models which dimensions a e imposed by he inhe en limi a ions o
he able in e ms o maximum es able model mass and size. Seismic es ing o la ge-size
models is nowadays mo e a o dable hanks o he pseudo-dynamic (PsD) me hod in la ge e-
ac ion-wall acili ies, such as he Eu opean Labo a o y o S uc u al Assessmen (ELSA) o
he Join Resea ch Cen e o he Eu opean Commission. In ac , he al e na i e o using la ge
shaking ables, when a ailable, o hea y and all specimens, may also ha e se ious limi a-
ions o accu acy in he applica ion o he inpu and he ep oduc ion o he cha ac e is ics o
he es ed s uc u es. This is mainly due o he dynamic in e ac ion e ec s be ween specimens
and shaking ables [1]. Mo eo e , when p o ec ion sys ems a e applied o he s uc u e, he
scaling o he sys em wi h he equi ed accu acy becomes i ually impossible.
On he o he hand, he PsD es ing me hod has o be ca ied ou a a low eloci y a e, in
o de o ensu e minimum con ol e o s and powe o he ac ua o s. This low es ing eloci y
may change he specimen ma e ials beha iou wi h espec o hei beha iou a eal eloci y.
This al e a ion is called s ain a e e ec (SRE) and may appea whene e he ime scale ac-
o is di e en om one. In ac , i may also appea , in he opposi e sense, in he dynamic es
on he shaking able wi h scaled-down specimens; in his case, due o he dynamic simila i y,
he ime scale ac o can be smalle han one.
In a PsD es , he ime scale is usually be ween 10 and 1000, which means ha ing a es ing
speed om 10 o 1000 imes smalle han he ac ual one. Luckily, his speed a ia ion does
no in oduce a ele an SRE o he classical cons uc ion ma e ials, such as s eel o conc e e.
Howe e , he SRE can be e y impo an o some new ma e ials, such as ubbe o silicon,
mos ly used in isola o s o ene gy dissipa i e de ices, as he be o e men ioned FVD. In spi e
o he inc emen o he es ing eloci y allowed by he implemen a ion o he con inuous PsD
me hod, he SRE on hese ma e ials canno be comple ely neglec ed, as hei appa en s i -
ness can be modi ied in a 10 o a 20%, i no mo e (see Figu e 1).
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
3
Figu e 1: SR E ec : o ce-displacemen cycle a eal speed (black) and o a speed 100 imes smalle (g ey)
I is possible o ex end he PsD ange o applica ion o cases wi h SRE by in oducing a
co ec ion echnique. In he case o buildings p o ec ed by means o FVD, his echnique is
based on he obse a ion o he de ices beha iou in ela ion wi h he s ain a e change. The
p incipal al e a ion consis s o an a enua ion o he measu ed o ce ampli ude, while he
shape o he o ce-de o ma ion cycle emains mos ly in a iable. Consequen ly, he simples
e sion o he co ec ion consis s o a Simple Linea Me hod (SLM), an on-line modi ica ion
o he es o ing measu ed o ces. The co ec ed o ce is ob ained by simply mul iplying he
measu ed o ce by a coe icien , which is a unc ion o he eloci y a e [2].
In he p esen pape , wo new me hods a e p oposed, bo h consis ing in a co ec ion o he
es o ing o ces ca ied ou nume ically in he analy ical pa o he PsD me hod, a e he
measu ing o he o ces and be o e he calcula ion o he nex s ep displacemen .
The i s new me hod is an imp o ed e sion o he SLM, called Fil e Me hod and i con-
sis s in a linea il e whe e he ou pu is he co ec ed o ce and he inpu s a e o be de e -
mined. The second me hod ep esen s a comple ely di e en app oach, based on a i icial
in elligence, using he same inpu a iables as he i s me hod and adding he eloci y a e λ,
enhancing he me hod wi h he possibili y o changing he eloci y a e du ing he es . This
app oach will be e e ed o as Neu al Ne wo k-based Me hod. Bo h me hods will be u he
desc ibed la e .
2 EXPERIMENTAL PART
2.1 Specimen
The specimen used o he es desc ibed in his pape is a 1-s o ey bol ed s eel s uc u e o
one deg ee o eedom wi h o e all dimensions o 3x3x3 me e s. The op o he s uc u e is
o med by a ein o ced conc e e slab. The s uc u e is complemen ed by wo in e ed V b ac-
es, which a e used as a suppo o he FVD (see igu es 1 and 2). This s uc u e has a double
unc ion in his s udy. On he one hand, i was used as cha ac e iza ion bench when de e min-
ing he de ices beha iou . On he o he hand, i was used as es ing specimen du ing he PsD
es s.
The displacemen s o he s uc u e we e measu ed om a no loaded e e ence ame on he
op angles o he s uc u e, using digi al encode s Heidenhain. The ela i e displacemen s o
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
4
he de ices we e measu ed ia ou po en iome ic ansduce s Ge an. Fo ces we e measu ed
using piezoelec ic load cells, one on each pis on (In e ace) and one on each dissipa ion de-
ice (Laumas).
Figu e 2: Specimen layou .
Figu e 3: Seismic p o ec ion sys em FVD.
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
5
Figu e 4: Specimen ins umen a ion.
2.2 Expe imen al cha ac e iza ion
Fi s o all, he cha ac e iza ion es s we e ca ied ou . The inpu o hese expe imen s was
a displacemen his o y, composed o a se ies o semi cycles o sinusoidal shape and di e en
ampli udes, connec ed in such a way ha he discon inui ies in he slope we e a oided. The
design o he inpu signal was based on wo aspec s: he simplici y, because i should be easily
pe o med on di e en ypes o de ices; and uni e sali y, meaning ha he esponse o he
de ices o he inpu should be as comple e as possible, bo h in displacemen s and eloci ies.
The cha ac e iza ion es s we e ca ied ou unde displacemen con ol and a di e en e-
loci y a es (λ=1, 75, 100, 250 and 500) wi h espec i e di e en equencies o he inpu sig-
nal (2, 2.5, 3, 3.5, 4, 4.5 and 5 Hz). The signals ob ained we e p e-p ocessed in o de o
emo e disco dances in bo h ampli ude and phase.
The na u al equency o he s uc u e was a ound 2.5 Hz.
Figu e 5: Cha ac e iza ion displacemen his o y, 2.5Hz.
The esul s o hese expe imen s, measu ed o ces and displacemen s, o med he expe i-
men al da abase. The da a measu ed du ing he es a eal speed (λ=1) ep esen he se o ob-
jec i e alues.

Bea iz Zapico, José L. Zapico, F ancisco J. Molina
6
3 CORRECTION METHODS
PsD es s a e ca ied ou s ep by s ep. A each s ep, he es o ing o ces a e measu ed on
he es ed s uc u e. The cu en alue o hese o ces, along wi h he accele a ion his o y, a e
used o p edic he displacemen o be applied o he s uc u e in he nex s ep. Due o he
p esence o FVD in he s uc u e, SRE will appea , and he measu ed o ces will be di e en
om he o ces measu ed on a eal speed es . The p oposed co ec ion akes place a he ana-
ly ical pa o he PsD me hod, i.e., when he displacemen s o he new s ep a e calcula ed.
The base o bo h co ec ion me hods is he same: he compa ison be ween wo di e en
signals, ob ained om wo es s ca ied ou in he same s uc u e wi h iden ical inpu da a bu
di e en de o ma ion a es. The co ec ion me hods a e uned in o de o minimise he di e -
ence be ween he measu ed and he p edic ed alues o he es o ing o ce.
The p ocess ollowed wi h bo h me hods is e y simila . Fi s , a da abase o expe imen al
da a is gene a ed (cha ac e iza ion es s). The objec i e alues ha e o be p esen in his da a-
base. A e wa ds, a p elimina y s uc u e is selec ed o he algo i hms (inpu s and o de s o
he il e , inpu s and numbe o neu ons o he neu al ne wo k) and hen he algo i hms a e
ained. This s ep is epea ed wi h se e al possible con igu a ions, un il he op imal s uc u e
is eached. Then, he esul an il e /ne is e i ied, using new da a as inpu and checking he
e o (
Mean Squa e E o
o MSE) o he ob ained co ec ion.
3.1 Fil e me hod
The i s new me hod is called he
Fil e Me hod
. I is a linea il e whe e he ou pu is he
co ec ed o ce and he inpu s a e o be de e mined. To do his, he il e has o be ained wi h
expe imen al da a and di e en inpu s and o de s. The analysis o hese es s e eals ha he
op imal esul s o he il e me hod a e eached when using as inpu he measu ed o ces and
displacemen s and hei i s de i a i es in ime, which co esponds wi h o de ze o o he
ou pu a iable and o de one o he inpu a iables o he il e . This solu ion cons i u es a
ade-o be ween accu acy o he p edic ions and ime o p ocessing. I akes o he ollowing
ma hema ical o m:
݂
መ
ሺଵሻ
ሺݐሻ = ܾ
ଵ
ሺఒሻ
∙ ݂
ሺఒሻ
ሺݐሻ+ ܾ
ଶ
ሺఒሻ
∙ ݂
ሺఒሻ
ሺݐ − 1ሻ+ ܾ
ଷ
ሺఒሻ
∙ ݀
ሺఒሻ
ሺݐሻ+ ܾ
ସ
ሺఒሻ
∙ ݀
ሺఒሻ
ሺݐ − 1ሻ
(1)
whe e
݂
መ
ሺଵሻ
ሺݐሻ
is he p edic ed o ce and λ is he speed o he es . Thus, wha needs o be
de ined a e he ou coe icien s ha mul iply he measu ed o ce
and displacemen
d
a he
ime ins an s
and
-1
.
3.2 Neu al Ne wo k-based Me hod
The second me hod is based on a i icial in elligence, using he same inpu a iables as he
i s me hod and adding he eloci y a e λ, enhancing he me hod wi h he possibili y o
changing he eloci y a e du ing he es . Neu al ne wo ks need o be ained wi h expe i-
men al da a also, so ha hei pa ame e s can be adjus ed. This p ocess is ca ied ou in wo
phases. Fi s , he de i a i es o he e o unc ion (di e ence be ween he objec i e alues and
he gene a ed alues) a e ob ained. In a second phase he ne pa ame e s a e op imized, mini-
mizing he e o . Fo hese phases, he
Back-P opaga ion
algo i hm and he
Scaled Conjuga e
G adien
me hod a e used.
Using he cha ac e iza ion es da a as inpu , i was s a ed ha he app op ia e numbe s o
neu ons we e 5 inpu neu ons, 1 in e nal laye o 4 neu ons and 1 ou pu neu on.
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
7
3.3 Applica ion
La e on, a di e en se o da a was used in o de o check he me hods. I consis ed o he
displacemen s and o ces ga he ed du ing a g oup o quasi-s a ic es s, un wi h a seismic dis-
placemen his o y as inpu signal. This se is called
Seismic Applica ion
in his s udy, as i is
he use o he al eady ained algo i hms on seismic da a. The new me hods, applied o he
seismic signals, p o ided good esul s in e ms o NMS e o (3.16% and 2.74% esp.), he
second one being he mos accu a e and e sa ile. Bo h algo i hms ou pe o m he Simple
Linea Me hod in all he analyzed cases, which p esen ed a NMSE o 6.36%.
Figu e 6: Seismic eal speed es measu ed displacemen .
Figu e 7: Fo ce-displacemen cycle, il e me hod. In black, da a om eal speed es s (λ=1), in g ey, da a om
PsD es wi h λ=100, in ed he co ec ed da a o ha es using he il e me hod
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
8
Figu e 8: Fo ce-displacemen cycle, neu al ne wo ks me hod. In black, da a om eal speed es s (λ=1), in g ey,
da a om PsD es wi h λ=100, in ed he co ec ed da a o ha es using he me hod based in neu al ne wo ks.
4 COMPLEMENTARY STUDIES
4.1 Neu al ne wo k based on seismic da a
Using he seismic da a desc ibed in he p e ious pa ag aph, a u he e i ica ion was ol-
lowed on he Neu al Ne wo k-based Me hod. A new ne was ained using he i s hal o
hese da a, while he second pa o he da a was used in he applica ion phase. I is impo an
o ema k ha his p ocedu e is possible only as an academic s udy and no in a eal case, be-
cause i includes he ealiza ion o dynamic seismic es ing on he s udied s uc u e, which is
exac ly wha is ying o be a oid. The applica ion e o ob ained wi h his ne (1.3% app ox.)
is, as expec ed, lowe han he e o p o ided by he p e ious ne . Ne e heless, he di e -
ences a e no high, demons a ing ha he cha ac e iza ion da a base is enough o a p ope
aining and ha he selec ed pa e n p o ides a good cha ac e iza ion o he sys em.
4.2 Selec ion o he cha ac e iza ion inpu da a equency
As has been seen be o e, he e we e 7 di e en cha ac e iza ion inpu signals, iden ical in
shape bu wi h di e en equency. Looking a he esul s o he Seismic Applica ion, i was
ound ha he i s na u al equency 2.5 Hz o he co esponding unp o ec ed (wi hou luid
iscous dampe s) s uc u e cons i u es an app op ia e equency o he p oposed ime-his o y
displacemen pa e n o es he dampe s. This alue can be easily es ima ed in he design
s age h ough nume ical models o ob ained by modal es ing o he ac ual unp o ec ed s uc-
u e.
5 CONCLUSIONS
A me hodology in ended o make PsD es s applicable o s uc u es seismically p o ec ed
by means o luid- iscous dampe s has been de eloped in his pape . I consis s o he on-line
co ec ion o he measu ed es o ing o ces as a unc ion o he o ces and displacemen s ex-
pe imen ed by he dampe s and he speed o he es .
Fo his pu pose, wo di e en p ocedu es ha e been de eloped. The i s one is o mula -
ed as a linea il e algo i hm in which he ou pu s a e he co ec ed o ces, while he meas-
u ed o ces and displacemen s a he dampe s ac as inpu s. The second one uses he same
inpu s and ou pu s, bu adding he es eloci y ac o as a new inpu a iable. In his case,
hese a iables a e unc ionally in e pola ed by means o a neu al ne wo k.
Bea iz Zapico, José L. Zapico, F ancisco J. Molina
9
These algo i hms a e calib a ed on he basis o da a ob ained ia an expe imen al p oce-
du e. This p ocedu e consis s o he dynamical applica ion o a ime-s o y pa e n o dis-
placemen , designed ad hoc o he cha ac e iza ion o he dampe s, and i s cyclic
ep oduc ion a ou di e en eloci y a es.
The pe o mance o he p oposed p ocedu es has been e alua ed h ough cyclic es s ca -
ied ou wi h di e en eloci y ac o s. The inpu employed o hese es s was he displace-
men ime-his o y measu ed du ing a seismic e en .
The analysis o he esul s allows he ollowing conclusions o be d awn:
•
Remo ing sys ema ic e o s om he expe imen al da a is essen ial o ob ain an accu a e
calib a ion o he co ec ion algo i hms.
•
The i s na u al equency o he co esponding unp o ec ed (wi hou luid iscous
dampe s) s uc u e cons i u es an app op ia e equency o he p oposed ime-his o y
displacemen pa e n o es he dampe s. I s alue can be easily es ima ed in he design
s age h ough nume ical models o ob ained by modal es ing on he ac ual unp o ec ed
s uc u e.
•
I is shown ha o de ze o o he ou pu a iable and o de one o he inpu a iables is
he app op ia e con igu a ion o he il e algo i hm. This solu ion cons i u es a ade-o
be ween accu acy o he p edic ions and ime o p ocessing. Conce ning he algo i hm
based on neu al ne wo ks, he app op ia e numbe o neu ons o he hidden laye is ound
o be ou .
•
The applica ion o he ained algo i hms o seismic expe imen al da a e eals ha bo h
he p oposed algo i hms ou pe o m he simple linea homologa ion in all he analysed
cases. The bes i ing is always achie ed wi h he neu al ne wo k algo i hm. Mo eo e ,
as his algo i hm includes he eloci y ac o as an inpu , i can be used o any es ing e-
loci y wi hin he aining ange, and i e en allows he change o his pa ame e du ing
he es .
REFERENCES
[1]
J. Donea, G. Magone e, P. Neg o, A. Pin o, G. Ve zele i, Pseudodynamic Capabili ies
o he ELSA Labo a o y o Ea hquake Tes ing o La ge S uc u es. Ea hquake Spec-
a (1996) 163-180.
[2]
F. J. Molina, G. Magone e, Pseudodynamic Simula ion o Base Isola ion on a Rein-
o ced Conc e e Building by Means o Subs uc u ing, P oceedings o he Fi s Eu ope-
an Con e ence on S uc u al Con ol, 1996.