SELECTION AND SCALING OF GROUND MOTION RECORDS FOR SEISMIC ANALYSIS Dr Dr. H. R. MagarP garPatil atil Associate ociate Profess fessor or Struct uctura ral l En Engineering ineering De Depa partme rtment nt Maharash harashtra tra In Institute titute of Technol chnology ogy, , Pune ne - 38 38 1
Ground Motion : 2 Ground motion is the movement of earths surface from the location of earthquake or explosion. Earthquake are usually caused when rock underground the surface of earth suddenly breaks along the fault.
Selection of Recorded Ground Accelerations for Seismic Design 3 Record selection based on earthquake magnitude (M) and distance (R): Recorded earthquake can be divided as: Magnitude consideration Large magnitude event (6.1 ˂ M ≤ 6.9) Medium magnitude event (3.4 ˂ M ≤ 6.1) Minor magnitude event (M<3.4) Distance consideration Large radius event (40 km ˂ M ≤ 90 km) Small radius event (12 km ˂ M ≤ 40 km)
Develop elopment ment of f primary mary record ord sets ts 4 Large magnitude – near fault bin (LMNF; 6.1 < Mw ≤ 6.9, 12 km ≤ R); Large magnitude – short distance bin (LMSR; 6.1 < Mw ≤ 6.9, 12 km < R ≤ 40 km); Large magnitude – long distance bin (LMLR; 6.1 < Mw ≤ 6.9, 40 km < R ≤ 90 km); Small magnitude – short distance bin (SMSR; 5.4 < Mw ≤ 6.0, 12 km < R ≤ 40 km); and Small magnitude – long distance bin (SMLR; 5.4 < Mw ≤ 6.0, 40 km < R ≤ 90 km)
Re Record ord selection ection ba based ed on n Soil l profile ofile 5 It is complementing criteria to both earthquake magnitude and distance. Shear wave velocity is metric for site classification. Based on shear wave velocity soil can be classified as: A - Rock 760m/s ˂ Vs30m ≤ 1500m/s B - Stiff soil 360m/s ˂ Vs30m ≤ 760m/s C - Soft soil 180m/s ˂ Vs30m ≤ 360m/s D - Very soft soil Vs30m ˂ 180m/s
Re Record ord selection ection ba based ed on n Strong rong motion tion dur uratio ation 6 1.Significant duration: Time interval during which 90% of total energy recorded at the station.
Re Record ord sel select ection ion based sed on on sp spec ectral tral ma matchi tching ng 7 Scaling: spectral matching technique are based on scaling of selected time history in time domain. Multiplying the records with a constant factor to get close to target spectrum at a period(s) of interest. Spectral matching in frequency domain: modifying the frequency content to match the target spectrum. Spectral matching in time domain: adding the wavelets to match the target design spectrum
Seismic code provisions for selection of records 8 Seismic codes which prescribe general guidelines to select ground motions are: - Euro code – 8 (Europe) - ASCE – 7 (USA) - NZS – 1170:2004 (New-Zealand) - GB – 50011-2001 (China and Taiwan)
Gr Ground und motio tion n us use in Eur n Europe ope 9 EC-8 allows the use of any form of accelerograms for structural assessment, i.e. Real, artificial and simulated accelerograms. A minimum of 3 accelerograms. It allow to use 7 accelerograms average values of response quantities. The peak ground acceleration of individual time histories should be greater than codified peak ground acceleration
Th The spectral ctral shapes pes given en by by EC EC-8 10
Gr Grou ound nd mo motion ion use se in Un United ted States ates (A (ASCE CE 7) 11 ASCE-7 provides general guideline for selecting and scaling ground motions use in nonlinear response history analysis of structure. A minimum 3 records are required The matching of spectrum is performed over the period range of 0.2T 1 to 1.5T 1 For three dimensional analysis spectrum representing the average of SRSS spectra of all records does not fall below 1.3 times design spectrum
Design Response Spectrum 12
Grou round nd mo motion ion us use in New-Zeala ealand d (NZS S 1170-200 2004) 4) 13 New-Zealand standard allows to use only actual records for structural assessment. Currently NZS 1170-2004 recommended that selection of seven records instead of three. Design spectrum for horizontal loading C(T) is define as: C(T) = C h (T)ZRN(T,D) where, C h (T) = spectral shape factor. Z = hazard factor R = return period factor N = near fault factor
Gr Grou ound nd mo motion ion use se in Ch China na (G (GB5 B5001 0011-200 20011 11 ) an ) and d Taiwan(Code wan(Code 05) 14 As per GB50011-20011 minimum 3 records are require.(at least two real and one simulated ground motion records require for analysis) As per Taiwan standard minimum 3 records are require. Spectral acceleration of each gm should be greater than 0.9 times that of design response spectrum
gions Co Comparison parison of f seismic smic require quirement ments s in n different fferent world ld regions 15 Criteria Europe USA New China Taiwan Zealand Minor Earthquake 95 years 50 years 30 years Moderate 475 years 475 years 500 years 475 years 475 years Earthquake Major Earthquake 2475 years 2500 years 2000 years 2475 years (MCE) Seismic design 475 years DBE=2/3* 500 years 500 years 475 years basis spectrum MCE Minimum number 3 3 3 3 3 of ground motions Response of Average Average Maximum Average Maximum structure response response if response of response if response of if ≥ 7 ≥ 7 records 3 records ≥ 7 records 3 records records
16 Criteria Europe USA New China Taiwan Zealand Spectral matching Yes Yes Yes Yes Yes allowed Matching period 0.2T 1 -2T 1 0.2T 1 -1.5T 1 0.4T 1 -1.3T 1 0.2T 1 -1.5T 1 Matching Sa avg for Sa avg for all Minimum Sa for each Sa for component all gm > gm > target difference gm > each gm > 0.9*target between 0.9*target 0.9*target each gm and target Artificial records Yes Yes No Yes Yes allowed
Earthquake Excitations 17 Earthquake Records Year Earthquake record description Recording Direction / Peak ground Component acceleration PGA (g) Chi ‐ Chi, Taiwan 1999 CHY101 CHICHI/CHY101-W 0.353 Irpina, Italy ‐ 01 1980 IRPINIA EQ, STURNO ITALY/B-STU000 0.071 Imperial Valley, CA 1940 IMPVALL/I-ELC 180 0.313 IMPERIAL VALLEY, EL CENTRO ARRAY #9, 180 (USGS STATION 117) Kobe, Japan 1995 CUE 99999, NISHI AKASHI KOBE/NIS000 0.509 Landers, CA 1992 LANDERS, LUCERNE LANDERS/LCN000 0.785 Loma Prieta, CA 1989 LOMA PRIETA, BRAN (UCSC STATION 13) LOMAP/BRN000 0.453 Northridge 1994 NORTHRIDGE AFTERSHOCK, ANAVERDE VALLEY - NORTHR/ANA180 0.06 CITY RANCH
Spectral Mapping 18
Spectral Matching 19
Ground motion scaling 20
Earthquake Records 21
Spectral Mapping and Matching Design Spectrum 0.7 2.0 Original Response Spectrum Scaled Response Spectrum 0.6 Spectral Acceleration (g) 1.5 0.5 Design Response Spectra Bhuj 0.4 1.0 0.3 Sa/g 0.2 0.5 0.1 0 0.0 0 1 2 3 4 0 1 2 3 4 Period (sec) Period (sec) 5.5 1.6 5.0 Design Spectrum Design Spectrum Original Response Spectrum 4.5 1.4 Original Response Spectrum Spectral Acceleration (g) Scaled Response Spectrum Spectral Acceleration (g) 4.0 Scaled Response Spectrum 1.2 3.5 1.0 3.0 0.8 2.5 Chamoli 2.0 Chamba 0.6 1.5 0.4 1.0 0.2 0.5 0.0 0.0 0 1 2 3 4 0 1 2 3 4 22 Period (sec) Period (sec)
5 Design Spectrum Design Spectrum 2.0 Original Response Spectrum Original Response Spectrum Scaled Response Spectrum 4 Scaled Response Spectrum Spectral Acceleration (g) Spectral Acceleration (g) 1.5 Imperial Valley 3 India- Burma Border 1.0 2 0.5 1 0 0.0 0 1 2 3 4 0 1 2 3 4 5 Time (sec) Period (sec) 6 Design Spectrum Design Spectrum Original Response Spectrum Original Response Spectrum 4 Scaled Response Spectrum Scaled Response Spectrum 5 Spectral Acceleration (g) Spectral Acceleration (g) Uttarkashi 4 3 Northridge 3 2 2 1 1 0 0 0 1 2 3 4 0 1 2 3 4 23 Period (sec) Time (sec)
3.0 Design Spectrum Average Original Response Spectrum 2.5 Average Scaled Response Spectrum 2.0 Spectral Acceleration (g) 1.5 1.0 0.2 T 1 to 1.5 T 1 0.5 0.0 0 1 2 3 4 Time (sec) Comparison of average scaled response spectra of all ground motions with design spectrum 24
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26 Case Study of Incremental Dynamic Analysis
Modeling 6m × 5 = 30m 6m × 5 = 30m Frame Selected for the analysis PLAN 6m X 5 = 30m 3.5m × 9 = 31.5m Elevation 27 Plan and Elevation of SMRF
Structural frame(with masonry wall) (a) (b) (c) Structural frame with energy dissipating devices a) Energy Dissipating System in all bays (AO Case) b) Energy Dissipating System in inner - outer bays (IO Case) c) Energy Dissipating System in outer - outer bays (OO Case) 28
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