Elastic behaviour of a masonry wall under biaxial loading

Abstract

Although masonry structures have been widely used for centuries, its fundamental behaviour is still not fully understood. Almost all masonry walls such as shear walls and infill panels in frame construction are subjected to in-plane loads. In recent years, more emphasis has been placed on the ultimate behaviour of brickwork with less attention to its deformation characteristics. For a realistic analysis of masonry structures, knowledge of both the ultimate strength and the deformation properties of the masonry is required. This study presents the results of an experimental investigation to establish the value for the elastic modulus of a globigerina limestone wall. 472 x 472mm panels were built using one-third scale stone blocks. The panels were manufactured with varying angles of the bedjoint to the vertical. The walls were loaded in a biaxial compression state of stress at various stress ratios. Research in this field of study has never been carried out for any local building material. Thus, isotropic behaviour was assumed to enable the author to obtain values from each individual wall panel. In the absence of any data provided from local research, the test values determined were compared to those presented in literature from abroad. Analysis of the test results showed that the modulus of elasticity of a globigerina limestone wall may be taken as 7.32 kN/mm2. The difference between the average En and Ep values indicates that local masonry exhibits orthotropic behaviour, the directions of orthotropy assumed to be normal and parallel to the bedjoints. Much of the observed variability appears to result from non-uniform deformation, possibly due to the variable elasticity of the individual blocks, that is, the variability is due to effects within a panel rather than difference between panels. Finally, this work attempts to relate the values of the elastic modulus to those obtained for the compressive strength.