Structural behavior of RC membranes having inclined steel bars

In seismic design, special care is needed when the shear force governs the response of a reinforced concrete (RC) element because this element undergoes stiffness degradation, strength deterioration and reduction in the energy dissipation capacity, as the cyclic loading increases beyond the yielding level. Experimental and analytical research has shown that this undesirable response can be controlled and even eliminated in the hysteretic load-deformation curves of a shear-dominant element if the steel orientation within the element is aligned in the direction of the applied principal stresses. However, in practice. it is quite difficult to orient the steel bars parallel to the principal stress directions due to geometric and construction limitations. In this study, the effectiveness of the steel reinforcement orientation on the structural response of RC shear membrane elements was investigated by analyzing the test results of four panels previously reported in the technical literature. The test results were also analyzed by using a compatibility-aided truss model. The experimental and analytical results indicated that the ductility and energy dissipation capacity of RC panels strongly depended on the reinforcement orientation. The results also showed that the hysteretic response of an RC panel did not vary linearly with the steel grid's orientation within the panel and there was a boundary where the deformability and energy dissipation of the RC panel increased rapidly. (C) 2012 Elsevier Ltd. All rights reserved.