EFFECTS OF SOIL LAYER CONSTRUCTION ON CHARACTERISTIC PERIODS OF RESPONSE SPECTRA

Transcription

1 13 th World onference on Earthquake Enineerin Vancouver,.., anada uut 1-6, 2004 Paper No EFFETS OF SOIL LYER ONSTRUTION ON HRTERISTI PERIODS OF RESPONSE SPETR O Jin-Shan 1, LI Xiu-Lin 2, LIU Hon-Shuai 3, WU Zhao-Yin 4, LIU De-Don 5 SUMMRY In thi paper, ome repreentative ite profile with enineerin inificance are elected and contructed, and round urface acceleration peak(gsp) and velocity peak(gsvp) of different ite profile under variou input round motion are calculated uin 1-D equivalent linearization wave method employed widely for eimic repone of ite. GSP and GSVP obtained are ued to calculate the repone pectra characteritic period ( T ) of different ite under variou input round motion. Effect of oil layer contruction on T of repone pectra are tudied, and ome valuable reult are obtained. INTRODUTION It i well known that characteritic period( T ) of repone pectra i one of the mot parameter of calibrated eimic dein repone pectra and alo an important parameter to tudy frequency pectrum of round motion produced by earthquake. When T of dein pectra were determined, the influence of ite cateorie and dein round motion roup were concerned, and yet the effect of oil layer contruction on T of dein pectra were not conidered[1] in hinee current ode of Seimic Dein of uildin. oth obervation of tron earthquake and enineerin practice indicate that there are inificant difference of T of acceleration repone pectra of the ite which are claified into the ame ite cateory and yet with different oil layer contruction, o it i quite important to tudy the effect of oil contruction on T of repone pectra for reaonably determinin eimic dein pectra. 1 Profeor, Intitute of Enineerin Mechanic, hina Earthquake dminitration. jinhan@mail.hl.cn 2 Graduate Student, Dalian Univerity of Technoloy, hina. lxl-138@ohu.com 3 Graduate Student, Intitute of Enineerin Mechanic, hina Earthquake dminitration. liu_h@ina.com 4 Graduate Student, Earthquake dminitration of Jilin Province, hina. wzy_iem@yahoo.com 5 Enineer, Intitute of Enineerin Mechanic, hina Earthquake dminitration. ldd-35@163.net

2 T of round urface acceleration repone pectra of variou oil layer contruction are calculated, and then the effect of variou oil layer thicknee, oft oil layer on T of urface acceleration repone pectra are tudied. The reult obtained in thi paper have a certain value on further tudyin ite claification and o on. SELETION OF OMPUTTIONL METHOD t preent, 1-D equivalent linearization wave method in frequency domain i uually ued to analyze eimic repone of round layered oil layer in enineerin practice [2, 3]. Thi method, recommended by hinee National Standard-ode for Seimic Safety Evaluation of Enineerin Site(G ), i employed to calculate round urface acceleration peak- max and velocity peak -Vmax of ite profile. Surface acceleration peak- max and velocity peak-v max of different ite profile under variou input round motion are computed; T of dein repone pectra are determined uin two-factor approach [4]; and the reult of calculation are analyzed to tudy effect of oil layer contruction on T of repone pectra. ONFIRMTION OF OMPUTTIONL PROFILES ND PRMETERS ccordin to the requirement of computational profile and parameter in 1-D equivalent linearization wave method of round layered oil, 21 baic ite profile for calculation, baed on hundred of bore of enineerin ite in hina, are elected and contructed. The thicknee of overlyin layer of thee profile ran from 3 to 100 m, hear wave velocitie and denitie of each layer oil, referred to meaured data in-itu, are iven with coniderin enineerin eoloical character of ite. Dynamic hear modulu ratio and dampin ratio of oil, recommended by Yuan (2001) [5], are mainly employed, and other are derived from experimental data. To avoid effect of frequency pectrum, while coniderin earthquake hakin, round motion acceleration time hitory with a peak of, a hown in fiure 1, i called (al) t() Fiure 1 acceleration input round motion( time hitory) time hitory. time hitory i caled to for ue a time hitory and to 0.1 for ue a time hitory. Soft oil layer in the paper i the oil layer whoe hear velocity i le than 140 m/, and i the leat. The baic profile elected and contructed in the paper are mainly from [6]. Effect of thicknee of overlyin layer on T NLYSIS OF OMPUTTIONL RESULTS

3 To tudy the effect of thicknee of overlyin layer on T, T of 21 ite profile, whoe thicknee of overlyin layer are 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, 80, 85, 90, 95 and 100m repectively, are calculated uin 1-D equivalent linearization wave method of round layer oil, and T of different ite profile under variou input round motion are preented in Fiure 2. In Fiure 2, abcia-h mean thickne of overlyin layer, whoe unit i meter, and ordinate-t mean characteritic T() H(m) Fiure 2 the effect of overlyin layer thicknee on period of repone pectra, whoe unit i econd. urve, and repreent the outcome of input round motion, and, repectively. Fiure 2 how that T of acceleration repone pectra increae with increain H, that to the ame H, T increae with increain intenity of input round motion, and that if H i no more than 15m, the variation of T i little. T Effect of oft urface layer on T Soft oil ha pecial enineerin character. Earthquake damae indicate that oft oil ha inificant effect on earthquake damae. to profile with oft oil on the top, two cae are tudied a follow: (1) the thickne of oft oil layer doen t chane, while the thickne of overlyin layer chane; and (2) the thickne of overlyin layer doen t chane, while the thickne of oft layer chane. to the firt cae, the urface layer of 21 elected and contructed ite profile without oft layer(called a normal profile ) are replaced with oft layer, whoe velocity and denity are 107 m/, 1.58 ton/m 3, and then new profile are formed. T of thee normal and new profile under variou input round motion are computed uin the above method in ection 2, and are compared, a hown in Fiure 3. In T() R Z R R H(m) Fiure 3 the effect of oft urface layer on T under different H Fiure 3, real line R, R and R repreent the outcome of profile with oft layer under input round motion, and, repectively, while dotted line Z, and repreent the outcome of normal

4 profile without oft urface layer under input round motion, and, repectively. The obtained reult how that on the whole T of profile with oft urface layer are bier than the value of normal profile and T increae with increain thickne of overlyin layer. ompared to normal profile, the three piece of learnin are ained: (1) If intenity of input round motion (peak i 0.1 or ) i mall, T of profile containin oft urface layer are bier than the value of normal profile when the thickne of overlyin layer i le than 70 meter, and T of profile containin oft urface layer are maller than the value of normal profile when the thickne of overlyin layer i more than 70 meter; (2) If peak of input round motion i, T of profile containin oft urface layer are maller than the value of normal profile; (3) If the thickne of overlyin layer-h i le than 15 m, the variation of T i maller under timehitory than that under and time-hitory. to the econd cae, three profile with the thicknee of 20m, 40m, 60m, repectively, are elected. For the profile whoe thickne of overlyin layer i 20 m, 7 new profile are formed by chanin the thickne of oft urface layer in profile, from 2 to 5 m; for the profile whoe thickne of overlyin layer i 40m, 9 new profile are formed by chanin the thickne of oft urface layer in profile, from 2 to 9 m; for the profile whoe thickne of overlyin layer i 60m, 12 new profile are formed by chanin the thickne of oft urface layer in profile, from 2 to 25m. T of repone pectra of thee new profile under different input round motion are calculated uin the method tated in ection 2, a hown in Fiure 4. In fiure 4, Hr mean thickne of oft urface layer. Fiure 4 indicate the relationhip between the thicknee of oft urface layer and T of different profile under variou input round motion. T() 20m T() 40m T() 60m Fiure 4 the effect of thicknee of oft urface layer on T Fiure 4 indicate that T increae with increain the thickne of oft urface layer. If oft urface layer thickne i maller, T increae with increain the intenity of round motion; while if the thickne of oft urface layer i bier, the relationhip between T and the intenity of round motion i complex. Effect of oft bottom layer on T Some profile ( thicknee of overlyin layer ranin from 5 to 70m) are elected, at the bottom of which oft layer are placed. T of thee new profile and normal profile under different input round motion are calculated, a hown in Fiure 5. RD, RD and RD in Fiure 5 repreent the outcome of the profile containin oft bottom layer under, and time hitory, repectively, while Z, and in

5 T() 2.2 RD Z RD RD H(m) Fiure 5 the effect of oft bottom layer on T Fiure 5 repreent the outcome of normal profile without oft bottom layer (normal profile) under, and time hitory, repectively. Fiure 5 indicate that T of profile with oft bottom layer are bi compare to the value of normal profile. In the cae of exitin oft bottom layer, if H i le than 20m, T increae with increain thickne of overlyin layer, and if H i more than 20m, T decreae on the whole with increain H. Effect of oft interlayer on T The effect of imbedded depth of oft interlayer and thicknee of oft interlayer at different depth on T are tudied. t Firt, to tudy the effect of imbedded depth of oft interlayer on T, two profile with the thicknee of overlyin layer of 50 and 70m, repectively, are elected, and everal new profile are formed by replacin layer at different depth with oft layer. T of the new profile are calculated uin the method tated in ection 2, a hown in Fiure 6. In Fiure 6, abcia-dr mean imbedded overlyin T() Dr(m) T() Dr(m) Fiure 6 the effect of imbedded depth of oft interlayer on depth of oft interlayer, whoe unit i meter, and 50, 50 and 50 repreent the outcome of profile, whoe thickne of overlyin layer i 50m under, and time-hitory, repectively, and other inal meanin are analoou. Fiure 6 indicate that a to profile calculated, oft interlayer imbedded depth have remarkable effect on T. If the imbedded depth of oft interlayer i le than 25 m, T increae with increain the imbedded depth of oft interlayer; and if the imbedded depth of oft interlayer i more T

6 than 25 m, T on the whole increae with increain the imbedded depth of oft interlayer. To the ame profile, the hiher i intenity of input round motion and the bier i T. Then, the effect of chane of thickne of oft interlayer at different depth on T are tudied. Firtly, the profile with the thickne of overlyin layer of 60 m, i elected, and 12 new profile are formed by replacin the top econd layer of the profile with oft layer, whoe thicknee ran from 0.1 to 18m. T of thee new profile and normal profile are calculated, a hown in Fiure 7(a). In Fiure 7, Hr repreent thickne of oft interlayer, dotted line repreent the outcome of normal profile and real line the outcome of profile containin oft layer. Secondly, by replacin the bottom layer of the profile with oft layer, whoe thicknee ran from 0.1 to 18 m, 12 new profile are formed. T of thee new profile and normal profile are calculated, a hown in Fiure 7(b). Fiure 7 indicate that compared to T() UR Z -UR -UR T() (a) (b) Fiure 7 ompariion between profile with oft interlayer at the top and bottom and normal profile DR Z -DR -DR T of the normal profile, if oft interlayer at the top and bottom of profile, T increae with increain the thickne of oft interlayer, and that T of profile with oft interlayer on the whole are bier than the value of normal profile and epecially T of profile with oft interlayer at the bottom are bier remarkably. ONLUSION The effect of oil layer contruction on characteritic period of repone pectra are tudied primarily in thi paper. Reearche indicate that the effect of oil layer contruction on characteritic period are remarkable. Under the ame input round motion, T increae with oft layer. It i deerved that T i affected by multiple factor. How T varie with the chane of oil layer contruction and input round motion i a complex problem. Neverthele, the obtained reult in thi paper have a certain value on further tudyin the field. T i one of the mot important parameter to pecify dein pectra in code of eimic dein, o it i neceary to continue to reearch the field. FUNDING KNOWLEDGEMENT The work reported on in thi paper wa undertaken with fundin provided by the tenth Five-Year Plan, hina Earthquake dminitration.

7 REFERENES 1. ode for eimic dein of buildin (G ). National Standard of the People Republic of hina, Liao Zhen-Pen, Li Xiao-Jun. Linearization Method for omputin Earthquake Repone of Ground Layered Soil. Seimic Microzonation-Theory and Practice. eijin: hina Earthquake Pre, 1989: Idri, I. M., et al. Seimic repone of horzitonal oil layer. SE. 1968; 94(SM4): Liao Zhen-pen, Li Da-hua. n Two-Parameter Method for Scalin Dein Earthquake Repone Spectra. Seimic Microzonation-Theory and Practice. eijin: hina Earthquake Pre, 1989: Yuan Xiao-min, Sun Rui, Sun Jin, et al. Laboratory experimental tudy on dynamic hear modulu ratio and dampin ratio of oil. Earthquake Enineerin and Enineerin Vibration. 2000; (4): Li Xiu-lin. Effect of oil layer contruction on urface round motion parameter of earthquake[d]. Harbin: Intitute of Enineerin Mechanic, hina Earthquake dminitration, 2003.