Seismic Force Exerted on Structures

Abstract

Effects of ground shaking on underground structures such as tunnels and basements are often analyzed by connecting structures with free field of ground (1D soil columns without effects of embedded structures) by means of (nonlinear) springs, see Fig. 13.1a. Springs are classified into those concerning normal earth pressure and those transmitting shear force. This method of analysis is called the method of seismic displacement, the method of subgrade reaction, or the method of Winkler foundation. The modulus of springs has long been studied in the fields of, for example, pile foundation (nonlinear subgrade reaction modulus). The horizontal response (time history of displacement) of a one-dimensional soil column is first calculated by using wave propagation theory in a level ground (Sect. 4.1 and Chap. 8). The calculated motion is then substituted at the support of springs, which generate dynamic response of the structure.