Experimental Investigation of Frictional Behavior of Mortarless Surface in Semi-Interlocking Masonry under Cyclic Displacement

Abstract

An innovative masonry building system, the semi-interlocking masonry (SIM) building system, is being developed in the Centre for Infrastructure Performance and Reliability at The University of Newcastle, Australia. The major motivation in developing the system was to improve the seismic performance of masonry infill panels in framed construction. In seismic areas, SIM can be used as framed mortarless engineered panels, which have significant energy dissipation capacity due to friction on sliding bed joints between units induced during an earthquake. The mortarless joints of SIM can be laid dry or, to improve thermal insulation and water resistance of SIM panels, can have some nonadhesive joint filler. This study focuses on the frictional behavior of three different mortarless SIM bed joint surfaces (dry surface, surface with linseed oil–based putty, and surface with rubber foam tape) for two different types of SIM units (topological and mechanical SIM units). The investigation aims to replicate realistic boundary conditions and loading regime using a modified couplet shear test setup. The constant precompression potentially induced in a masonry infill panel was applied by the static gravity load. Tests were designed to simulate relative sliding of SIM units during earthquakes over the service life of a panel: 160 sliding cycles of ±1.0-mm relative displacement applied dynamically (100 mm/min). In addition, one cycle of ±10.0-mm displacement was also applied statically (10 mm/min) for comparison to dynamic frictional behavior. The load-displacement history was recorded. The paper expands significantly from the previously published conference paper and reports the results of this testing program in terms of the friction coefficient (based on Mohr-Coulomb failure criterion) and the energy dissipation characteristics for each type of joint (only for topological SIM unit).