Axial force in columns of buildings under vertical nearfault strong ground motion

In this paper the maximum axial force in the first-storey columns of multi-storey buildings has been investigated. For this purpose some multi-storey buildings, designed by buildingcode, have been simulated by a simple dynamic model. By assumption of linear behavior of material and ignoring of the buckling of columns, the equation of motion of the model has been solved by the fourth-order Runge-Kutta method under vertical fault-paralleldisplacement and fault-normal pulse with different magnitudes. The maximum axial force in the first-storey columns has been normalized by the total mass of the building and the peak acceleration of the fault motion. The results indicate that under synchronous vertical nearfaultground motion the maximum normalized axial force of the first-storey columns is independent of the number of stories and magnitude of earthquake and equal to 0.33. The differential motion effect can amplify or diminish the maximum normalized axial force respect to the synchronous ground motion.

Keywords:

Axial force in column , Building , Vertical ground motion , near-fault earthquake Forward directivity , Fling-step