Axially-Loaded Column under Earthquake Loading

Abstract

The fundamental vibration frequency of columns decreases with increasing axial compressive load. 1. This paper carries out the free vibration analysis of a beam using the finite element method. The frequencies and mode shapes are determined. The vibration behavior of the beam under axial load is investigated analytically and using the finite element method. The results show that the square of the frequency reduces linearly with an increase in axial load. At the critical buckling load, this frequency goes to zero. Experimental work to determine the buckling load of a column can be carried out indirectly from an axial load versus frequency plot. 2. The effect of axial load on the dynamic response of columns under earthquake ground motion is analyzed. Using Euler-Bernoulli beam theory, we derive the governing differential equation. We model the column using the 4-degree-of-freedom beam element. We calculate the displacement-time response numerically using Newmark's method. 3. We introduce Rayleigh damping in the analysis and examine the deformation response spectrum for different earthquake ground motions with and without axial load.