FUNDAMENTAL STUDY OF Q-Δ RESONANCE CONSIDERING HIGHER-ORDER MODES BY SHAKING TABLE EXPERIMENTS AND FINITE ELEMENT ANALYSIS

Abstract

The Q–Δ effect is a phenomenon that a column with different lateral stiffness generates a restoring torsional moment owing to geometric nonlinearity when its top displaces in two horizontal directions simultaneously. The Q–Δ resonance that is resonance of a torsional mode induced by the periodic torsional moment due to the Q–Δ effect could cause considerable torsional vibration even in non-eccentric buildings. However, the Q–Δ resonance in higher-order modes has not been investigated well. We first constructed a model of a two-story non-eccentricity structure and derived the conditions of the Q–Δ resonance considering higher-order modes. Then, we conducted shaking table experiments and finite element analysis to reproduce the experiments. As a result, it was confirmed that the second mode in the torsional direction was excited as predicted by the derived Q–Δ resonance condition. Moreover, the finite element analysis could reproduce the experimental result with high accuracy.