Experimental investigation of semi-interlocking mortarless masonry-infilled frames

Masonry-infilled frames (MIFs) are a common construction form in many parts of the world. The presence of mortared masonry makes structural frames relatively stiff resulting in limited displacement capacity and unintended torsional forces that have been responsible for catastrophic destruction of buildings during several past seismic events. An alternative infill material solution is using semi-interlocking (mortarless) masonry (SIM), which is associated with controlled in-plane sliding. Five small-dimensioned specimens, including one bare frame and four SIM-infilled concrete frames were constructed and subjected to cyclic displacements. The variable parameters included specimen aspect ratio, vertical load on frame members, and grouting of masonry. A detailed description of the construction procedure and the testing of material properties used in the experiments are presented. The damage patterns associated to each of the specimens are explained to investigate their deformation modes and to identify the drift thresholds corresponding to the damage in the MIFs. A modified idealisation model is proposed that is suitable for SIM-infilled reinforced concrete MIFs. Critical structural properties of MIFs that include the yield strength, energy dissipation capacity, initial stiffness and ductility are obtained from the idealisation model and the force-displacement relationship. These properties are compared and contrasted against the specimens and also to the traditional MIFs with the relevant data extracted from literature. From the observed damage and the force-displacement relationship, Performance Levels of the MIFs are established. Compared to traditional MIFs, the SIM-infilled MIFs are shown to have significantly smaller initial stiffness and larger performance level drift thresholds.