Influence of Shear on Deformations of Coupling Beams: Fid-Bau Portal

Influence of Shear on Deformations of Coupling Beams

Fisher, Andrew W. / Collins, Michael P. / Bentz, Evan C.

Abstract In the design of tall towers in Canada, the use of coupled shear walls is common where two or more tall walls are tied together by a series of relatively small, heavily loaded and short coupling beams. The stiffness of these coupling beams is important in determination of the distribution of forces throughout the structure and thus deserves study. This paper presents the results from a recent experiment on a coupling beam at the University of Toronto and describes the measured deformations in terms of components of the deformation. The results show that a flexure-only analysis would account for only 53% of the total predicted deformation. Addition of the effect of curvature resulting from shear (but not shear strain) increases the predicted percentage to 57% while, finally, inclusion of shear strains increases the percentage to 100%. This demonstrates that a flexure-only analysis will grossly underestimate the flexibility of such a member at service and ultimate limit state loads and shear strains must be included for accurate prediction of deformations. For a longer member that is more flexurally dominant, the respective contributions are 78% from flexure only, 85% from an analysis including curvature from flexure and shear (but not shear strain) and 100% from the combination of all three. Thus the contribution of shear-induced curvature can be more important for longer members than shorter ones.