Numerical evaluation of mortarless interlocking masonry walls under in-plane lateral loading

Abstract

Interlocking masonry systems have the potential to increase capacity while reducing construction time and cost, particularly in seismic applications. Salient among the challenges faced in advancing this technology is the selection and optimization of the block geometries and interlocking patterns. In this preliminary numerical study, masonry wallets comprised of interlocking units were loaded in-plane until failure using the distinct element program 3DEC. Twenty unique block geometries were used to create wallets of various aspect ratios, and the wallets were simulated under several overburden pressures. To study block splitting, some geometries were altered to include predefined splitting planes and were simulated using several masonry unit strengths. The failure mode and lateral load capacity of each simulation was compared to a control geometry with the same wall aspect ratio and overburden stress. The results (without block splitting) showed that interlocking can force different failure modes and substantially increase lateral load capacity, depending on the wall aspect ratio and the lock location, number and orientation. For slender walls with an aspect ratio of 2, little change versus the control was observed and the lateral load capacity was slightly reduced in most cases; this agrees with expectations as rocking failure governed in all cases including the control. For aspect ratios of 1 and 2/3, the controls and geometries with locks only on the head joints experienced sliding failure along the top course, while samples with locks on the bed joints showed stair-stepping shear failure along the joints which corresponded to a significant increase in lateral load capacity. Lateral load capacity was improved by as much as 130%. However, this substantial increase in lateral load capacity does not reflect block splitting. In the simulations which included predefined splitting planes, the prevalence of block splitting increased with increasing overburden stress and decreased with increasing masonry unit strength. In simulations where little to no splitting was observed (low overburden pressure or high masonry unit strength), results largely agreed with earlier conclusions. On the other hand, samples with low masonry unit strength simulated under high overburden pressure showed little improvement in lateral load capacity. Future investigations will include adding greater complexity to existing models, input parameter sensitivity studies, evaluation of additional interlocking geometries and load patterns, and experimental validation.