Large-scale bare and partially rubber-filled mechanical couplers subjected to biaxial effects

In this study, large-scale bare and partially rubber-filled mechanical couplers were developed especially for use in a high-performance hybrid post-tensioned precast rocking wall system. This system has a self-centering property and is resistant to seismic effects using a rocking mechanism and supplemental energy dissipation elements. Despite these advantages, there are also deficiencies that impair the performance of the system, such as low energy dissipation capability, sliding of walls, crushing of wall toe regions, and higher mode effects. Couplers were developed in this study to overcome these deficiencies. Couplers are made of low-cost mild steel and ordinary natural rubber, which can be externally connected to adjacent elements with bolts, thus ensuring ease of assembly and the possibility of replacement if necessary. Extensive experimental investigation was conducted on the couplers to verify their efficiency under biaxial effects. Besides cyclic shear plus constant axial tension/compression loads (typical loading condition in base isolator elements), cyclic axial plus fixed shear displacement was considered to simulate actual loading conditions. The investigation parameters were the loading type and magnitude, plate thickness for bare couplers, and the density of steel sheet layers in rubber blocks for filled couplers. Additionally, valid finite element models of the couplers were established, and modeling techniques were explained in detail. The results demonstrated the efficiency of bare couplers as additional energy dissipation elements and the suitability of filled couplers for use at the edges of rocking walls due to their high shear and bearing strengths combined with their energy dissipation capabilities.