Flexural Rotational Capacity of Spandrel Beams

This paper presents an investigation designed to study the effect of the presence of torsion of the flexural rotational capacity of spandrel beams. Test results from fourteen identical L-shaped beams and fourteen identical rectangular beams, of normal weight concrete, in which the ratio of moment to torque was varied, between pure moment and pure torque cases, show that the presence of torsion reduced the flexural rotational capacity. This reduction is significant even for torque/moment ratios as low as 6%. The flexural rotational capacity of beams subject to combined bending and torsion may be evaluated by multiplying the rotational capacity of an identical beam under pure bending by a reduction coefficient. The calculated results using this method compare very well with the experimental results. The same reduction coefficient should be used in the case of continuous spandrel beams to reduce the allowable percentage of moment to be adjusted according to ACI 318-71 Building Code.