Torsion-shear behaviour at the interfaces of rigid interlocking blocks in masonry assemblages: experimental investigation and analytical approaches

Abstract

Increasing interest has recently been devoted to interlocking blocks/interfaces capable to enhance the sliding resistance of masonry joints to external forces. In this framework, this paper deals with the assessment of the torsion-shear capacity of the contact interface between the lock and the main body of an interlocking block, assumed to have a cohesive behaviour. The interlocking block is a rigid unit which, on its faces, have square cuboidal locks keeping the adjacent/overlapped blocks together and preventing blocks from sliding. Two numerical approaches and a novel ad hoc experimental investigation are proposed to simulate the torsion-shear behaviour by applying eccentrical shear forces to the lock. First, concave, convex and corrected concave formulations provided by the literature for assemblages of rigid blocks with conventional planar joints are extended to model the interlocking block behaviour. Then, according to a second approach based on the discrete element method, the concave-shaped interlocking block is modelled by convex polyhedrons representing the lock and the main body of the block, considered as individual rigid units stacked over each other with a cohesive contact in between. A novel experimental investigation on the limiting pure shear and torsion-shear combinations at the lock interface made of cohesive material is also presented. Two different mortars were chosen to make the specimens, which were casted using 3D printed moulds, and different test configurations were set up to simulate shear and torsion-shear failures. The analytical and numerical results are compared with each other and against the experimental ones, with interesting remarks on the application of the different approaches.

Interlocking Joints with Multiple Locks: Torsion-Shear Failure Analysis Using Discrete Element and Equilibrium-Based SiDMACIB Models

“…For the sake of consistency with the experimental torsion-shear tests carried out by the authors with others [27,28], the dimensions shown in Figure 2 are defined for stacked blocks with an interlocking joint. Two samples are presented in this figure, one with three and one with five locks.…”

“…The results obtained using the novel SiDMACIB model are then compared to the results obtained using the well-established DE analysis (3DEC 7.0, free version [30]), and some proposals to adjust or better calibrate the former formulation are finally presented. 3DEC has been chosen as a reliable candidate to carry out this validation because the experimental tests for single locks presented in [27,28] showed strong agreement with the results obtained by 3DEC.…”

“…Table 1 shows the material properties of the blocks and the inner and dry faces, already used to model the mentioned experimental tests [27,28]. Note that the properties of the inner interfaces, including their shear and tensile strengths, correspond to the block material properties.…”

“…This is equal to the lateral force Vy and torque My = Vy • ex applied to the face centroid. To model such a distributed force, 3DEC needs the value of the distributed force at the face centroid V dy,h and the slope of the distributed force K y , which are [27,28]:…”

“…On the other hand, if interlocking blocks are composed of a number of projections (herein called locks), one of the main challenging issues is the assessment of the torsionshear capacity of the corrugated interfaces. Based on the concavity formulations adopted for conventional planar block interfaces [26], the torsion-shear capacity of a single lock with a rectangular cross-section was recently validated through a series of experimental tests and analytical investigations using limit analysis and distinct element (DE) methods [27,28], the latter via 3DEC numerical modelling software, version 5.0 [29]. This paper aims to extend the analytical exploration to assess the torsion-shear capacity of rectangular interlocking interfaces with multiple locks shared between two stacked blocks, assuming that all the locks of the interface are involved in the overall planar capacity.…”