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NGA Site Response Study

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  1. NGA Site Response Study Joseph Sun, Tom Shantz, Zhi-Liang Wang

  2. Project Objectives • Compare RVT based site response response calculation versus time history approach • Compare RVT based amp factors (RASCALS) with time history based (SHAKE) amp factors • Compare amp factor differences between equivalent-linear procedure (RASCALS and SHAKE) and non-linear procedures (D-MOD2 and SUMDES)

  3. Basis of Comparison: • Two shaking levels (Mw 6.5 @ 15 km and Mw 7.5@ 5 km) • Three profile depths (100, 300, and 500 ft) • 30 spectrum compatible ground motions were used for each shaking level. • Results from one RVT run from RASCALS is compared with the average of 30 SHAKE run • Non-linear analysis scope reduced to two Mw7.5 time histories analysis for two depths to demonstrate differences in difference non-linear programs

  4. Target Spectrum (A&S strike-slip, rock) Mw=7.5 r=5 km Mw=6.5 r=15 km

  5. Shear Wave Velocity ProfileLa Clenega Site – Simplified CJR Model

  6. Non-Linear Properties Clay • Based on SHAKE91 • Extend to 10% strain • 2 Curves only – simple • Decoupled modulus and damping • Non-linear models should base on matching modulus reduction curves. Damping may be different Sand Sand & Clay 0.0001 0.001 0.01 0.1

  7. Deep Profile – 500 ft M7.5 Ground Surface Response

  8. Deep Profile – 500 ftM6.5 Ground Surface Response

  9. Deep Profile – 500 ftGround Surface Response

  10. Med. Deep Profile – 300 ftGround Surface Response

  11. Shallow Profile – 100 ftGround Surface Response

  12. Deep Profile – 500 ftAverage Spectral Ratio

  13. Med. Deep Profile – 300 ftAverage Spectral Ratio

  14. Shallow Profile – 100 ftAverage Spectral Ratio