Cyclic tests on two novel welded flange plate connections in precast concrete moment resisting frames

Abstract

Precast concrete moment resistant beam-to-column connections, usually designed in form of semi-monolithic connections which require in-situ concrete casting leading to a complicated assembling process. Additionally, using concrete with different ages in a connection causes cold joints and shrinkage problems. To overcome these issues, in this study, two steel beam-to-column connections (SBCs) were proposed and designed for precast concrete moment resisting frames. Compared to the semi-monolithic connections, proposed connections exclude protruding bars, resulting in a facile and rapid installation. Regarding the inverse T shape, these connections provide a better condition for installing the precast slabs and consequently reduce structural floor thickness. To evaluate the connections, two precast and one in-situ specimens were made and tested on a 2/3 scale and a cyclic load pattern was used to evaluate their performance. Test results indicate that the proposed SBCs have a maximum resistance and ductility until 1.5 and 0.9 times the in-situ concrete beam-to-column connection (ICBC), respectively. ACI374.1-05 criteria including strength and stiffness degradation ratio as well as energy dissipation ratio at drift 4% were employed to evaluate the qualification of the proposed connections. One of the proposed connections met all seismic requirements of ACI374.1-05. The plastic hinge locations were estimated by measuring the strains of rebars and steel parts of the connections. Results revealed that on the contrary to ICBC, the plastic hinge formation in proposed SBCs developed out of the beam-column joint which coincides with the strong-column and weak-beam principle in precast frames and postpones the total fracture mechanism of structure.