Second-order torsion effects in concrete buildings

Efeitos de torção de segunda-ordem em edifícios de concreto

ABSTRACT:

The internal forces due to torsion in global analysis of buildings, and its second-order effects, usually are not properly considered in structural design or even in design code’s prescriptions. Although the γ_Z coefficient, which is used to the evaluation of global second-order effects, has a wide, useful and consolidated application, it is true that specific torsional aspects are not well considered by it. This paper discusses the little-known γ_θ coefficient, an analogous proposition to the γ_Z coefficient, but focused specifically on the consideration of torsional effects. After the discussion on the concepts and the design methodology, several buildings are evaluated and their displacements and the coefficients γ_Z and γ_θ are calculated. Comparing these parameters, and also the results obtained by the P–Δ method, it is demonstrated the importance and the reliability of the γ_θ coefficient.

Keywords:
torsion; second-order effect; global analysis