Effect of vertical ground motions on horizontal response of structures

Single-degree-of-freedom (SDOF) elastic models are commonly used for gaining an understanding of the response of structures to earthquake ground motions. The standard SDOF model used does not account for the effect of gravity or the combined effect of horizontal and vertical excitations on horizontal response. The purpose of this paper is to review previous work on this topic and to investigate a series of SDOF models that do incorporate these effects and to compare their response to the response of the standard model using 186 strong-motion records of near-field earthquake ground motions. It is found that for most realistic SDOF models and most earthquake ground motions the effect of vertical excitation on horizontal response is small.