University at Buffalo - Low Aspect Ratio Rectangular Reinforced Concrete Shear Wall - Specimen SW2

Although low aspect ratio shear walls are widely used in buildings and safety-related nuclear structures, their hysteretic behavior, including peak strength and effective elastic stiffness, has not been adequately characterized to enable robust performance and risk assessment. The US National Science Foundation funded a Network for Earthquake Engineering Simulation (NEES) research project on shear walls of conventional and composite construction to better understand the seismic behavior of these widely used structural elements. A total of 16 rectangular, low aspect ratio concrete shear walls (12 conventionally reinforced concrete and four composite) were built and tested at the University at Buffalo (UB).

The goals of the project include validation of simulation tools and updating of numerical modeling procedures to more accurately predict the behavior of low aspect ratio walls with rectangular cross sections. Physical and numerical simulation results will be used to generate and update predictive strength and new code design equations, load-displacement relationships and macro-level hysteretic models. Fragility functions and damage states for use with next generation tools for performance-based earthquake engineering will be updated. Educational tools will be developed to effectively and efficiently explain the resistance and failure mechanism of low aspect ratio reinforced concrete shear walls.

The test data confirmed that design equations in codes and standards are unable to predict peak shear strength and that the scatter in the predictions is significant. The hysteretic response of the test specimens degraded quickly at cycles to displacement greater than that associated with peak strength, questioning the behavior of nuclear structures that incorporate shear walls for earthquake shaking more intense than design basis. The effective stiffness of the test specimens were substantially lower than those calculated using the predictive equations of ASCE 43-05 and ASCE 41-06, which is problematic for dynamic analysis, generation of in-structure floor response spectra, and risk assessment.