Strength tests on slender plain block masonry walls with veneer wythes

Abstract

An experimental program was undertaken on single wythe and cavity concrete block masonry walls to evaluate the effect of the veneer on the vertical load-carrying capacity of the wall. Twelve unreinforced, ungrouted, and relatively slender single wythe and cavity walls were tested to failure under quasi-static, monotonic, axial loading. Three values of equal end load eccentricity were used in the test program. A review of published test data associated with the behavior of single and double wythe concrete block masonry walls indicates a scarcity of data regarding the magnitude and type of effect of the veneer on the stiffness, strength, and stability of such walls. To examine the performance of axially loaded slender masonry walls, and to isolate any effect of the veneer in modifying that performance, the plain masonry walls of the present program were chosen to be quite slender (height-to-thickness ratio of 30) and relatively thin (thickness = 140 mm). This study used a microcomputer spreadsheet program to evaluate the theoretical capacity of the walls and to generate load –moment interaction diagrams. The program is based on a moment–area analysis and incorporates the effects of finite deflections, nonlinear constitutive laws, and cracked section behavior. The walls exhibited material failure in the case of centrally loaded walls, whereas stability failure governed for eccentrically loaded specimens. The contribution of the veneer to the lateral stiffness of the cavity wall system was found to vary with the eccentricity of the applied end load. The contribution to strength seemed to be negligible for central loading, but was quite significant for the case of the eccentrically loaded walls. More tests covering different loadings, slenderness values, and end conditions are needed to quantify the behavior. Key words: masonry, slenderness, stiffness, stability, capacity, veneer, cavity wall, ties, eccentric loading.