Analytical modelling of masonry prisms.

Abstract

Current codes governing the design and analysis of masonry structures offer two methods of determining the ultimate compressive strength of a masonry prism, (i) code tables; and , (ii) laboratory prism testing. The first method is empirical and conservative; and , the second one is costly and time consuming. An analytical model is formulated here to determine the ultimate compressive strength of a concentrically loaded brick or concrete block masonry prism. This model takes into account the major variables affecting the performance of a masonry assemblage. These variables include the geometrical and strength properties of the masonry unit, the mortar joint, and the grout fill. By observing the existing experimental data on the behavior of the individual elements making up the masonry prism, and taking note of how they interact as a unit, analytical formulas are derived. Special attention is given to triaxial states of stresses in masonry unit and mortar. The results of this analytical model, on the average, are about 89% of the actual test results. This is a much better accuracy than the results obtained from the code tables for the same data. Code table results, on the average, were about 75% of the actual test results. Also, the deviation of the results for the code table method, was much greater than for the analytical model, which indicates the consistency of the proposed model. This analytical approach is a better alternative to the prism testing method and will be proposed to the code writing committees as a substitute for the existing code tables.