Response of Buildings with Inclined First-Story Columns to Near-Fault Ground Motion

In this paper a simple model of a three story building with inclined first-story columns has presented. The stories are supposed to be rigid and are connected to axially rigid mass less columns by elasto-plastic rotational springs and linear rotational dampers. The considered model is subjected to horizontal component of fault normal pulse with different magnitudes and the governed nonlinear differential equations of motion have been solved by the forth order Runge-Kutta method. Results indicate that the inclination of the first-story columns stiffens the system. However, the change of the frequency of the first mode is small. The deformation of the first story with inclined columns is such that it forces the building in a pendulum-like motion. So it would be possible to reduce the relative building response. Results indicate that an optimum value of inclination angle of the first-story columns is . Under this condition the first-story drift decreases while upper-story drift increases, respect to the common building with . For larger inclination angles the gravity effect leads to increase the first-story drift as well. This solution would be useful in earthquake resistant design of buildings with architectural limitations at the first story.