Record Processing Considerations for Analysis of Buildings

1. Record Processing Considerations forAnalysis of Buildings Moh Huang California Strong Motion Instrumentation Program California Geological Survey Department of Conservation Sacramento, California COSMOS Workshop on Strong-Motion Record May 26-27, 2004

2. California Strong Motion Instrumentation Program at California Geological Survey • CSMIP has extensively instrumented over 180 buildings in California. • CSMIP has processed more than 500 building records from significant earthquakes in California. • Processed data (Vol. 2 & 3) from recent and some historic earthquakes are available at the CISN Engineering Strong Motion Data Center (www.cisn-edc.org).

4. CISN Engineering Data Center (www.cisn-edc.org)

5. CSMIP Building Instrumentation • Sensors are installed at key structural members and distributed throughout the building. • Each sensor is cabled to one or multiple central recorders located in the base of the building. • - Locations are based on the lateral force resisting system so important mode of vibration will be recorded.

6. Hayward City Hall (isolated by FPS) Free-Field

7. Utilization of Building Records • Verify and improve analytical procedures - improve computer model - improve design practice - verify nonlinear static procedures • Improve seismic provisions in the building codes • Post-earthquake evaluation of buildings

8. Analyses of Building Records • Time history analyses – take recorded base motion as the input to the model, then compare predicted response with measured response (acceleration, velocity or displacement). • Derive dynamic characteristic of the building (periods, damping, mode shapes, participation factors, etc.) and compute key response parameters (maximum inter-story drifts, base shear, etc.) from the records.

9. CSMIP Processing of Building Records • All channels in the building are processed with a wide open bandwidth. • Identify building periods from records (time histories or response spectra). • Use one usable data bandwidth for all channels (horizontal channels control the final filter). • Free-field record is processed using the same bandwidth as the building record as part of the building system. However, it is processed with a wider bandwidth as a stand alone ground motion record.

10. Flexible Building

12. Sa plot for the 44th Floor record T

14. 44th Floor B Level

17. 1994 Northridge Earthquake

18. Roof, NS

19. Roof, EW

20. EW NS

21. Stiff Building

22. North Wing of a 1-story Hospital Buildingin Templeton, California

23. Acceleration records from the 2003 San Simeon Earthquake

24. Absolute Displacements

25. Relative Displacements (long-period filter corner at 5 seconds)

26. Relative Displacements (long-period filter corner at 10 seconds)

27. Base-Isolated Buildings

28. Los Angeles – University Hospital (base-isolated)

29. Rubber Isolator

30. Acceleration records Above Isolator Below Isolator

31. Isolator Deformation

35. Summary • It is essential to identify the building periods from the record. • For flexible buildings, it can not filter out fundamental mode (with a long period) motions. • For stiff buildings, it is not a problem to filter out more long-period motions. • Permanent deformations of structural members cannot be obtained from acceleration records by routine processing using filters. • Relative displacement sensors can be installed to provide direct measurement of the movement if it is expected to occur.