Stress Reduction Coefficient and Amplification Factor for Seismic Response of Ground

Abstract

Incorporating the increase of shear modulus with depth (z) by using a depth exponent p , the response of linear visco-elastic ground under steady state harmonic vibration was examined. The soil mass lying above the rigid base was discretized into a large number of horizontal layers. For a given vertical thickness ( Hr ) of the upper ground material in the first mode of resonance, it was noted that the resonant frequency ( fr ) as well as the values of amplification factor ( Mf ) and the stress reduction coefficient ( Cd ) at a given z∕ Hr can be computed as a function of p and D , where D is the damping ratio of the material. An increase in D leads to (1) an increase in Cd ; (2) a very little increase in fr ; and (3) a decrease in Mf . On the other hand, an increase in p causes: (1) an increase in fr ; (2) a marginal increase in Mf ; and (3) a decrease in Cd . It was evident that the values of Mf and Cd at a given depth will be affected significantly by changes in the chosen thickness of the soil deposit ...