Non-planar beam–wall joints in tall building structures

Abstract

Stress concentration and local deformation occur at both coplanar and non-planar beam–wall joints. However, over the years, only coplanar joints have been studied in detail. Very few studies on non-planar joints have been carried out and most designers still treat non-planar joints as hinges and neglect the possible coupling effect of beams connected to such joints. There is also no established method for detailed design of non-planar joints. Herein, a parametric study of the behaviour of non-planar beam–wall joints using finite-element analysis is described. On the basis of numerical results, a simple equivalent-frame model is developed. Examples are given to illustrate its applications and the results show that the coupling effect of beams connected to non-planar joints can be very substantial. Moreover, in order to avoid cracking at the joints, it is proposed that in the detailed design (a) the concentrated out-of-plane moment acting from the beam on the wall should be catered for by designing a vertical strip of the wall, having a width as determined in the present study, as a column to resist such a moment; and (b) the bending moment induced in the beam should be properly allowed for and the longitudinal reinforcement so provided adequately anchored into the wall.