Nonlinear response-history analysis in design practice

1. Nonlinear response-history analysis in design practice November 2007 Joe Maffei RUTHERFORD & CHEKENE

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4. Why do NLRH? • The code makes us. (Base isolation or supplemental damping) • Substantiation of non-prescriptive (“alternative”) designs. • We want to know what happens. What is the value of NLRH?

5. Outline • Example projects • Unique value of NLRH • Findings from NLRH of tall buildings • Dispersion of NLRH results • Ground motion input • Conclusions • [Modeling uncertainty]

6. Example projects that used NLRH

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9. Education Tower

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11. Buildings with supplemental damping RUTHERFORD & CHEKENE

12. Waterfront pier structures

13. Exploratorium – Piers 15 and 17 RUTHERFORD & CHEKENE

14. Non-prescriptive seismic design

15. ROOF 13th BASE

16. What is the unique value of NLRH? …

17. To determine what happens, not how much. Desired mechanism Undesirable mechanism RUTHERFORD & CHEKENE

18. Findings from NLRH analyses of high-rise buildings

19. Runs scaled from 0.1x MCE to 4x MCE

20. Runs scaled from 0.1 x MCE to 4 x MCE

21. Core wall moment versus shear amplification

22. Moment to shear ratio • 110’ at 0.6x MCE • 90’ at MCE • 57’ at 2x MCE • 230’ • 175’

23. Use NLRH to determine what happens, more than how much. RUTHERFORD & CHEKENE

24. Coupled wall Plastic hinge locations RUTHERFORD & CHEKENE

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27. Dispersion of results among 7 or 14 ground motion records

28. 14 NLRH RUNS ROOF 13th BASE

29. Coupling beam rotation

30. Considering dispersion • “Demands for ductile actions shall be taken not less than the mean value obtained from the NLRH. Demands for low-ductility actions (e.g., axial and shear response of columns and shear response of walls) shall consider the dispersion of the values obtained from the NLRH.”

31. NLRH ground motion input

32. NLRH INPUT • 7 horizontal ground motion pairs • 14 response-history runs GRN 180 GRN 270 GRN 180 GRN 270 RUTHERFORD & CHEKENE

33. NLRH analysis at MCE • “When the ground motion components [statistically] represent site-specific fault-normal ground motions and fault-parallel ground motions, the components shall be applied to the three-dimensional mathematical analysis model according to the orientation of the fault with respect to the building. When the ground motion components represent random orientations, the components shall be applied to the model at orientation angles that are selected randomly; individual ground motion pairs need not be applied in multiple orientations. .”

34. NLRH analysis at MCE • “Where applicable, an appropriate number of the ground motion time series shall include near fault and directivity effects such as velocity pulses producing relatively large spectral ordinates at relatively long periods.”

35. Conclusions

36. The most important value of NLRH is that it tells you what the nonlinear mechanism is, and what the overstrength forces are on elements that you want to remain elastic. RUTHERFORD & CHEKENE

38. Modeling uncertainty

40. Olivian

41. Comparison of SAP model by KPFF vs Perform model by R&C

42. EQ4: Test EQ4PGA = 0.93g

43. EQ4:

44. Experimental results EQ3: Essentially linear EQ4: Non-linear

45. Measured

46. 111 Almaden Ave San Jose

47. Beam connection behavior

48. Beam fiber model

49. Analysis model versus test results