In this study, an incremental-iterative finite element program is developed to predict the behaviour and failure mechanism of the system under compression. The nonlinear progressive contact behaviour of dry joints that takes into account the geometric imperfection of the block bed interfaces is based on experiment testing. The contact relations developed for the dry joints are within specified bounds and can be used for any mortarless masonry system efficiently with less computational effort.

Furthermore, the best fit equation for the experimental test data is used in the program to describe the stress-strain behaviour of the masonry block unit under compression for the uniaxial and biaxial stress states. Material nonlinearity in the compressive stress field is considered for the masonry block in the orthogonal directions and the effect of microcracking confinement and softening on the stress-strain relationship under biaxial stresses are included employing the equivalent uniaxial strain concept. The program allows for the progressive local failure of the masonry block (crushing and cracking). After cracking, a smeared crack model is adopted and the compressive strength reduction in the cracked block is considered.

A plane stress 2D continuum is adopted in this study. Eight-node isoparametric elements are used to model block unit and three-node isoparametric interface elements of zero thickness located between two material elements are employed to model the interface characteristics of the dry joint.

In order to validate the finite element program, compression tests results [1] of interlocking mortarless hollow prisms are compared with the developed program results. The material stress-strain relationship of the masonry block has been incorporated successfully into the model to include the biaxial state of stress using the equivalent uniaxial strain concept. The developed finite element analysis program is capable of prediction accurately the deformation of the interlocking mortarless block prism under compression. The dry joint influences the prism deformation predominantly at the lower and middle load levels. The comparison with test results shows a good agreement with the predicted strength and the predicted cracking pattern.

1

Jaafar M.S., Alwathaf A.H., Thanoon W.A.M., Noorzaei J. and Abdulkadir M.R., "Characteristic of Interlocking Mortarless Block Masonry under Compression", Submitted for publication to the Proceedings of ICE, Structures and Buildings, UK, 2005.

2

Oh, K., "Development and Investigation of Failure Mechanism of Interlocking Mortarless Block Masonry System", PhD Thesis, Department of Civil and Architectural Engineering, Drexel University, Philadelphia, 1994.

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