Dynamic torsional coupling and simplified prediction method for single-story wooden structure having flexible floor diaphragm

Abstract

Small detached wooden houses typically have eccentric arrangement of shear walls, which results in torsional vibration when subjected to earthquake. In addition, flexible floor diaphragm of wooden structures complicates the dynamic behavior. In this paper, index of torsion taking dynamic effect and flexibility of floor diaphragm into account is proposed based on dynamics model. The index is theoretically related to modal shape of 1st mode obtained by eigen value analysis. Prediction method of modal shape and natural circular frequency for 1 × 1-span model and 2×2-span model is also proposed. The tendency of the dynamic behavior is compared to eccentricity ratio, which is originally defined in Japanese Building Standard Law, and the key parameters to control torsional coupling is pointed out.