Out-of-plane behavior of unreinforced hollow clay tile masonry infilled wall panels

The structural integrity of existing unreinforced masonry infilled walls under earthquake generated forces is of primary importance in seismically active zones. One of the seismic excitations is in the out-of-plane direction of the wall panel. The inertial out-of-plane forces due to the mass of the panel are investigated and may be simulated by a uniformly distributed lateral load normal to the wall surface. Two in- situ wall panels designated for testing will be analyzed in this study. The testing will be done by inflating an air bag positioned between the wall panel and a reaction frame consisting of metal reinforced plywood board.

Analytical models and techniques were developed to predict the initial crack load and the ultimate strength. The first cracking analysis is based on linear elastic finite element stress analysis. With the estimated material properties and appropriate failure criteria, the analytical model is verified with experimental results from published literature. A parametric study was performed on several parameters suspected to influence the initial cracking strength of the wall panel. These parameters include modulus of elasticity, Poisson's ratio, modulus of rupture, and boundary conditions.

The ultimate strength prediction is based on yield line analysis with arching action of the infill confined in a steel frame. It also includes the infill strength and stiffness orthotropics in the analysis. The technique is used to examine various parameters thought to affect the ultimate load capacity of the wall panel. The parameters investigated include compressive strength, modulus of elasticity, face shell thickness and frame rigidity.

The boundary interfaces of the panel, modeled with various support conditions, were investigated. The boundary condition is a major factor in determining the initial cracking and ultimate loads. The effect of the air bag size was also examined for the strength in two limit states. It does not affect the capacity of the wall panel significantly.