GB GB DGJ CECS GB JTG /TB PEER ~ Hz g 10 20

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1 Journal of Building Structures Vol. 32 No. 9 Sep s TU A Study on spectra and spectral damping reduction factors in Chinese seismic design codes CAO Jialiang 1 SHI Weixing 1 WANG Yang 2 JIANG Xiangmin 3 1. College of Civil EngineeringTongji UniversityShanghai China 2. Shanghai University of Electric PowerShanghai China 3. CNGC China Wuzhou Engineering Co. LtdBeijing China AbstractThe determination of the damping reduction factors of acceleration spectra that match the statistical characteristics of strong ground motionsbased on the normalized acceleration spectra specified in the seismic codes is a practical method to construct the design response spectra for long-period structures with damping ratios higher than Statistical characteristics of earthquake response spectra were summarized first. Then qualitative investigations on the rationality of the seismic design spectra and spectral damping reduction factors in various Chinese seismic design codes including the codes for buildingsspecial structuresnuclear power plantshighway bridges and electrical facilities in industrial plants were performed. In addition rationality of the improved seismic code spectra and spectral damping reduction factors was also discussed. The results show that values of both relative displacement spectra and relative velocity spectra will decrease along with the increase of the damping ratio. Values of absolute acceleration spectra will either decrease or increase along with the increase of the damping ratio. There are still no appropriate evaluation expressions for the damping reduction factors in the Chinese seismic design codes. The pseudo relative displacement spectra obtained from converting acceleration spectra in Chinese seismic design codes or modified acceleration spectra proposed by some researchers are only suitable for the seismic design of short-period structures with lower damping ratios. Keywordsseismic design codeacceleration response spectradamping reduction factors DRF damping ratio displacement response spectradisplacement-based design CB jialiang292@ 163. com swxtgk@ 126. com

2 GB GB DGJ CECS GB JTG /TB PEER ~ Hz g s Fig. 1 Trilinear modeling of displacement spectra Lin Yuyuan Chang Kuochung k 1 > k 2 > k 3 k i 0 T D T > T D k i < 0 T k i 0 Bommer Mendis 18 PGD peak ground displacement 21 1 Wanda 19 Eurocode 8EN A 2 M s 5. 5 A ~ E ζ = Eurocode 8 T = 10 s PGD ~ 0 ~ 10 s ~ s 35

3 2 η = αt ζ/ αt 0. 05= Tη T 0. 1 s T η s T T g η 2 T g /T γ T g T 5T g 2 Eurocode 8 η γ - η 1 T - 5T g Fig. 2 Displacement spectra defined in Eurocode T - 5T g 5T g T 6 s 2 η 1 η 2 γ GB η T ζ T g 3 Fig. 3 Relative displacement spectra and relative velocity spectra corresponding to average conditions of different site classes 4 MZH000 Kobe-Japan 1995 Fig. 4 Response spectra MZH000 Kobe-Japan sη T η T T g = s T > 3. 5 s 0 ~ 10 s 2 η ζ 1 η 0. 1 s T T g ζ T ζ η ζ > Kobe η T > T g MZH000 NGA 1109 η 3 T < T g η T g GB T > T g η T g ζ < T g < s ζ < η cu + ku = - mü + ü g GB GB GB GB η 1 η 2 γ 36 5 GB Fig. 5 Damping reduction factors of acceleration spectra defined in code GB ζ > η T 3 0 T 0. 1 s η T 0. 1 s T T g η T g T T η T T > T g

4 T g =0. 25 s T ζ Table 1 Comparison of damping reduction factors of T g acceleration spectra defined in code GB η 2001 /η 2010 η 2001 /η 2010 T g =0. 25 s % % % 1 T = 6. 0 s % % % % % % T = 6. 0 s % % % % 2. 3 DGJ DGJ GB Fig. 6 Damping reduction factors of acceleration spectra defined in code GB η 1 η 2 γ DGJ η T ζ T g T ζ T g ζ < η ζ > η = αt ζ/ αt 0. 05= η 1 ζ < T > T 10Tη g 0 T 0. 1 s η T ζ < T η T ζ > η s T T g η T η 2 T g /T γ T g T 5T g η γ - η 1 T - 5T g T - 5T g 5T g T 10 s 10 s η 0 < T < 5T g ζ = GB η ζ = 0. 4 η Fig. 7 Pseudo relative displacement spectra in code GB % T T > 8 DGJ Fig. 8 Damping reduction factors of acceleration spectra defined in code DGJ η η ζ < T < T g η 2010 η ζ > T > T g η T ζ > T > 5T g η T η 37

5 5T g ζ = 0. 4 η ζ = % Fig. 9 DGJ Pseudo relative displacement spectra in code DGJ CECS Fig. 10 Damping reduction factors of acceleration spectra CECS and pseudo relative displacement spectra in eq. 4 3 defined in code CECS ~ 6 4 ~ 6 η T g 4 GB GB GB η = αt ζ/αt 0. 05= 1 T = s 12. 5T T 槡 ζ e s T 0. 1 s T 1 / 槡 ζ e T 0. 1 s 4 η = ζ/ ζ 5 αt ζ η = αt = 1 0 T T g { T g /T ζ ζ T g T 10 s 6 10 ~ 12 3 η T ζ T g T η η T ζ ζ < T < η η s η T ζ < T > s η T ζ > T < s η T ζ > T > s η Fig. 11 Damping reduction factors of acceleration spectra and pseudo relative displacement spectra in eq. 5 defined in code CECS T

6 Fig. 12 Damping reduction factors of acceleration spectra and pseudo relative displacement spectra in eq. 6 defined in code CECS η ζ η 2. 6 GB η η GB T η T ζ T g T > T g ζ T ζ η η ζ 8 η η = αt ζ/ αt 0. 05= 2. 5 JTG /TB Tη T 0. 1 s T JTG /TB η s T 8. 0T g T - 8T g 8. 0T g 7. 0 s η = αt ζ ζ = 1 + αt ζ Fig JTG /T B Damping reduction factors of acceleration spectra and pseudo relative displacement spectra in code JTG /TB η 1 = ζη 2 = ζ/ η 1 T - 8T g 0 T 10 s 7 T 7 η ζ 14a η T 13a T ζ 13b 3 0 T 0. 1s ζ η ζ < Ⅱ A η T ζ > η T g E T 8. 0T g ζ η η T 13 η ζ T 8. 0T g T 7. 0s ζ η η η η T ζ T > T g T η

7 14b ~ 14c 14b ~ 14c T > 8. 0T g T > T g T η T ζ > η T 14 GB T T g η T Fig. 14 Spectra and spectral damping reduction factors defined in code GB T g T 10 sη T T η η 1 ζ b ~ 15c 9 C 10T 0 T < 0. 1 s { αt ζ η = αt = C 0. 1 s T < T g 0 T T g C T g /T T g T 9 C = ζ/ ζ 15a 24 η T ζ T g Fig Spectra and spectral damping reduction factors suggested in ref a η T T 0. 1 sζ < T g η 1 15b ~ 15c

8 F h η = αt ζ/αt 0. 05= / 槡 16. 6ζ /T ζ ζ 11 η = αt ζ/ αt 0. 05= 11 η { Tη T 0 T 0. 1 s T ζ T g 17a η T ζ η s T 6. 0 s 17b ~ 17c ~ η 2 = 1. 5 / ζ s T 6 s η ζ 16a η T ζ 16b ~ 16c η 16 η T T g η 0 T 0. 1 s ζ T T T g T k 3 k 2 Fig. 16 Spectral damping reduction factors and adjusted spectra suggested in ref Fig. 17 Spectral damping reduction factors and adjusted spectra suggested in ref ηζ T 4. 5 s ζ ~

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