Experimental and Analytical Study of new Proposed Semirigid Concrete BamtoColumn Connection

A new semirigid concrete beamcolumn connection is proposed and its performance is investigated through experimental and analytical studies. In this connection, the beam dose not directly connect to column but it is connected with torsional link member. This scissor mechanism allows the beam to make rotation with respect to column. Moreover, the strengthened connections are also suggested to support higher levels of lateral deformations for structures located in high risk seismic areas. The connections behavior under cyclic loads has been studied experimentally using three types of specimens; i) basic specimen, ii) strengthened specimen with Carbon Fiber Reinforced Polymer (CFRP) wrapping, iii) strengthened specimen with steel core reinforcing. The results showed that for low levels of deformations, the basic connection exhibited acceptable performance but for higher levels of rotation, the strengthened specimens had significant merits in ductility and nonlinear characteristics. Beside the experimental tests, the numerical model of connection was constructed using ABAQUS program. The accuracy of modeling was verified through experimental results. To investigate the effect of using proposed semirigid connection in seismic demands of concrete structures, two rigid and semirigid threestory frames were modeled in OpenSees. Several nonlinear dynamic analyses were carried on models and the different global and local demands were compared. The results showed that in lowrise or nonsway buildings in which the lateral displacements are not very considerable, semirigid connections can lead to smaller seismic loads and consequently the economical and optimal design.