Cyclic loading test for lightly reinforced exterior wall with openings

Abstract

Recently, slender and lightly reinforced exterior walls with large openings have been frequently used in high-rise residential buildings for economical construction. Although the exterior walls can be severely damaged by moderate earthquakes, minimum reinforcement is used, and the seismic details are not used in the current design practice because it is assumed that the seismic performance of the exterior walls is not significant in the entire structure. To investigate the strength and damage mode of the exterior walls, four exterior wall specimens with openings were tested under cyclic lateral loading. The main test parameters were the type of the openings (i.e., small, horizontal slot, vertical slot), and the reinforcement ratio in the horizontal components (horizontally 0.42-1.29%, and vertically 0.28-0.89%). The test results indicated that the peak strengths of the exterior walls with large depth of the horizontal components reached the nominal flexural strengths calculated by assuming solid walls and neglecting the opening effect. However, due to the premature tensile fracture of the vertical rebars, the lateral stiffness was significantly degraded, and the energy dissipation was limited. Further, the maximum crack width was affected by opening type and reinforcement ratio. A parametric study was conducted using a finite element (FE) model to investigate the effects of the design parameters. Based on the test and analysis results, a design recommendation for exterior walls with openings was provided. The exterior walls can be designed as solid walls under the following limited conditions: the total opening areas are less than 10% of the wall area in elevation, the relative flexural stiffness of the horizontal components is greater than the lateral stiffness of the walls, and the axial load ratio is less than 10%. Further, the allowable lateral drift ratio for permissible crack damage was suggested to be 0.10%.