Assessment of Global Torsional Sensitivity of Common RC Structural Walls Layout Types

Abstract

The objective is to validate the conclusions of a study about the nonlinear behaviour of the asymmetrical RC structural wall systems that was based on the one storey equivalent model time history response. The main instrument of verification is the time history nonlinear response of the full 3D multistorey model. The time history analysis was conducted using Perform 3D software. Three structural types are selected for this study: type I (strong torsionally restrained, Ω_θ = 1.4) corresponding to the most common structural wall type structure in Romania; type VI – the central core structure with perimeter frames along one main direction; and type III the central core structure without perimeter frames (Ω_θ = 0.3). The parameters which were varied during the study are: (a) stiffness to mass center eccentricity, and (b) q –behavior factor. Nine spectrum compatible accelerograms were used. The seismic characteristics were the ones corresponding to Bucharest. The results were judged in function of two response parameters: (1) R – safety factor, the minimum capacity to demand displacement corresponding to a vertical element and (2) R₁ – the drift amplification of the floor extremities due to torsion relative to pure translation. The main conclusions to be validated are:

• 1. If the substantial decrease of the q behaviour factor accounted for torsionally flexible structures has a significant beneficial effect on the safety factor.

• 2. If the perimeter frames have a beneficial effect for the behaviour of the central core structure and for the suitability of this type of structure for seismic areas.