Slender reinforced concrete structural walls are efficient lateral force resisting systems. However, many existing walls designed based on pre-modern seismic code provisions are expected to fail in a brittle manner, due to inadequate amount of shear reinforcement, poorly confined boundary elements, or poor detailing. A new method for retrofitting seismic code-deficient walls, which combines selective weakening and self-centering to prevent brittle failures and provide resiliency, is investigated using analytical modeling. The method involves partially cutting base of the wall and utilizing post-tensioning tendons to ensure rocking, self-centering, low damage and ductile response of retrofitted walls.
At the component level, two code-deficient slender walls failed in undesirable modes, including brittle shear, were analyzed using finite element modeling under cyclic lateral loading. Results of analytical models, particularly load-displacement curves, were validated using test data from the literature. Acceptable agreement was observed between test data and numerical model. Validated models were used to implement the retrofit strategy on code-deficient walls. Comparisons of benchmark and retrofitted walls were used to document the effect of proposed retrofit method on global behavior of walls in terms of stiffness, strength, residual displacements and energy dissipation capacity.
At the building system level, the effect of the proposed retrofit strategy on the dynamic behavior of buildings equipped with retrofitted walls is being investigated. Benchmark and retrofitted building responses are being compared in terms of acceleration demand, displacement demands, available strength and displacement capacities.