Novel Precast Erection Method of Interlocking Mechanical Joints Using Couplers

Despite many advantages of precast concrete members, the conventional precast members lack in the treatment of construction waste, require concrete pour forms at joints, and their structural discontinuity leads to low redundancy in the load paths. This study aims to provide novel solutions to these problems by developing interlocking mechanical joints with fully restrained moments for the connections of both steel-concrete composite precast and reinforced concrete precast columns. In the proposed connections, a pair of steel plates was provided; each plate was installed at the bottom of the upper columns and on top of the lower columns, which were then connected monolithically via vertical column rebars passing through the metal plates, providing flexural capacity similar to that of conventional monolithic column connections. The column rebars were spliced by couplers that were manufactured to be fastened by the weight of the upper column, which was heavy enough to push the vertical rebars into the couplers in the area prepared at the lower part of the upper column, providing a monolithic joint for the connected precast columns. Throughout the erection test, it was found that conventional monolithic cast-in-place joints for assembling precast concrete frames can be replaced by the interlocking mechanical joints, offering rapid erection compared with traditional practices. The columns with proposed joints were also proved to demonstrate sufficient structural capacity. Stresses and strains were found within allowable limits on the basis of finite-element analysis considering concrete plasticity during the assembly of heavy precast frames. The erection test showed sufficient verticality ensuring rebars to be connected via couplers when the upper columns were released down to the lower columns. This novel frame did not require concrete cast at the joint, eliminating the use of concrete pour forms adopted in conventional construction methods over the last years. Effortless erection with structural efficiency was demonstrated by using the proposed assembly method, with a significant reduction in the time required to assemble precast frames, similar to that of steel frames. The novel frames proposed in this study are expected to replace the conventional concrete frames including cast-in-place frames and precast frames with traditional joints. These novel frames contribute to the concrete industry by providing rapid and dependable construction of both precast and cast-in place frames.