Behaviour of interlocking mortarless block masonry

Abstract

Various types of interlocking mortarless (dry-stacked) block masonry system have been developed worldwide. However, the characteristics of dry joints under compressive load, and their effect on the overall behaviour of the interlocking mortarless system, are still not well understood. This paper presents an experimental investigation into the dry-joint contact behaviour of masonry and the behaviour of interlocking mortarless hollow blocks for grouted and ungrouted prisms under compression. Two experimental test set-ups are proposed to evaluate the contact behaviour of dry joints, considering the geometric imperfections in the contacting faces. The results show that the contact behaviour of a dry joint is highly affected by geometric imperfections in the block bed. Different patterns of deformation are distinguished in mortarless hollow (ungrouted) and grouted prisms. Dry joints predominantly affected the hollow prism deformation until the compressive load reaches 0·57 of the maximum load. However, this behaviour is not common in grouted prisms, because noticeable deformation commences after 0$38 of the maximum load. Furthermore, the variations of strength and deformation in grouted specimens are diminished compared with those in ungrouted specimens.

A generalised damage model for masonry under compression

“…Dry surface-interfaces of the dry-stack masonry show more pronounced nonlinear progressive stiffening until a larger threshold strain in comparison to conventional mortarinterface (Andreev et al, 2012;Jaafar et al, 2006). The reason for this prolonged progressive stiffening is attributed to the crushing of interstices, closing of voids and gaps in the dry interfaces.…”

“…The initial gap between the units decreases progressively until the complete joint closure under compressive load. Some researchers have studied experimentally the relationship between stress and strains in the proximity of dry interfaces within a narrow gauge length under compressive loads (Andreev et al, 2012;Jaafar et al, 2006). The progressive stiffening model which was developed in this study for combined mortar and unit-mortar interfaces was used to simulate the non-linear progressive stiffening behaviour of dry joints by setting the thickness of dry joints a small value (0.2 mm).…”

Finite-element analysis of an alternative masonry wall system

“…The characteristics of the mortarless (dry) joint were investigated experimentally (Alwathaf, 2006;Alwathaf et al, 2005;Jaafar et al, 2006) and load-deformations relations that are required for the FE modelling were formulated based on the experimental results. The non-linear behaviour of the mortarless bed joint under compressive load was simulated taking into consideration the block bed imperfection.…”

“…The behaviour of this system is significantly affected by the behaviour of the mortarless joint in all stages of loading (Alwathaf, 2006). The geometric imperfection of the block bed, which can be considered as the main disadvantage of the system, influences the structural behaviour of the mortarless masonry system (Alwathaf, 2006;Alwathaf et al, 2005;Jaafar et al, 2006;Lourenco et al, 2005). Hence, modelling of mortarless joints plays a significant role in the overall simulation of the system.…”

“…In this study, the behaviour of both joint and material in the mortarless block masonry systems is described and proposed based on comprehensive experimental tests carried out by the authors and published elsewhere (Alwathaf, 2006;Alwathaf et al, 2005Alwathaf et al, , 2012Jaafar et al, 2006). Moreover, an FE model is proposed and an incremental-iterative program is developed to predict the behaviour and failure mechanism of the interlocking mortarless walls under concentric and eccentric compressive loading.…”