Shear Strength of Reinforced Concrete Walls for Seismic Design of Low-Rise Housing

In the last decade, the construction of low-rise housing made of reinforced concrete (RC) walls and slabs in Latin America has increased considerably. These box-type structures commonly have large lateral stiffness and strength, thus exhibiting low lateral displacements and shear forces demands. The low level of seismic response has prompted designers to use concrete strengths of 15 to 20 MPa (2175 to 2900 psi), as well as of 100 mm (4 in.) thick walls with web steel reinforcement ratios smaller than the minimum prescribed by most design codes. Considering these particular wall characteristics, design requirements in current codes are not directly applicable. Moreover, a blind application of current requirements may lead to an unjustifiable excessive cost of a housing unit, especially because of the web steel ratio required. To improve design methods for this type of construction, a behavioral model and equations capable of estimating the peak shear strength of walls for low-rise housing were developed and calibrated from test results. The experimental program included quasi-static and shake-table tests of walls with different height-to-length ratios (h(w)/l(w)) and walls with openings. Variables studied were the type of concrete, web steel ratio, and type of web reinforcement. Statistical analysis of the ratios between predicted and measured shear forces demonstrated that the proposed model is a suitable design tool that may be adopted for design and evaluation guidelines and codes.