The behavior of reinforced concrete walls that exhibit the shear mode of failure is studied, through the results of an experimental program that included the test of 26 full-scale specimens subjected to cyclic horizontal displacements of increasing amplitude. Test parameters were the aspect ratio of the walls, the amount of vertical and horizontal distributed reinforcement, and the compressive strength of concrete. The results include the cracking shear strength, the maximum shear strength, the drifts associated to these loads and the drift associated to a collapse limit state for each of the specimens tested. Conclusions are drawn concerning the deformation capacity, the energy absorption, the dissipation characteristics and the strength deterioration after maximum strength shown by the walls and the influence of vertical distributed reinforcement on the seismic behavior of walls.

Most recent seismic codes include response modification factors in the definition of the equivalent lateral forces that are used for the design of earthquake resistant buildings. The response modification factors (R) are used to reduce the linear elastic design spectrum to account for the energy dissipation capacity of the structure. The evaluation of these response modification factors for various sets of earthquake records and ductility factors is presented herein. Special attention is given to the short period range where the reduction of linear elastic response spectra is smaller than the values for intermediate and long period structures. An idealized and simple variation of the response modification factor as a function of the period of vibration, suitable for seismic codes formulation, is also presented.

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