Site Response to Vertical Earthquake Motion

Evaluation of ground response is one of the fundamental problems in earthquake geotechnical engineering. Current practice has tended to focus on horizontal earthquake motion and ignore the effect of vertical motion. Because of strong vertical ground motions recorded in recent earthquakes, great concern has arisen over the behavior of vertical motion and its effect on engineering structures. This paper presents a practical procedure for the analysis of site response to vertical earthquake motion. The procedure involves the use of dynamic stiffness matrix method and is built in the modern MATLAB environment to take full advantages of the matrix operations in MATLAB. The nonlinear soil behavior is accounted for through the well-accepted equivalent linear approach. Comparisons of the predictions from the procedure against downhole array records show reasonably good agreement.