Short and Long Term Capacities of Slender Concrete Block Walls

Ayman Aboel-Fetoh Abdel-Maksoud, McMaster University


Short and long term capacities of slender concrete block masonry walls subject to eccentric axial loads were investigated. A finite element model was developed to include both the geometric and the material nonlinearities. To analyze large members, a combined macro-micro finite element model for the masonry assemblage was also developed by which the advantages of the micro material analysis, using the theory of plasticity, as well as the interaction among the different constituent materials were accounted for within the macro finite element model. Utilizing the finite element model, parametric studies were conducted to cover wide ranges of the parameters which affect behaviour. The geometric, loading, and the material parameters as well as their interactions were involved in this study. Three simplified methods were developed to provide some rational design approaches. The first method, called "Lumped Area Method", provides a closed form solution for the wall capacity. In the second method, Moment Magnifier Method, a rational method for determining the modulus of rigidity was empirically developed to be used in the calculation of the moment magnification factor. In the third method, Deflection method, the theory of structural mechanics was used to determine the secondary moments using a secant modulus of rigidity which was numerically developed. Experimental creep tests were carried out on ungrouted and grouted masonry prisms built with normal weight blocks, and ungrouted prisms built with light weight blocks. Creep data were collected for almost 400 days under two levels of sustained stresses. Creep functions were statistically developed and were incorporated in the finite element-creep analysis. Another set of parametric studies was conducted to investigate the long term capacities of masonry walls. Also, the Lumped Area Method was extended to account for the creep effect in predicting the long term capacity.