Seismic behavior of steel coupling beam with different buckling constraint materials

With constrained plates on both sides of steel coupling beam web, the continuous strengthening can be achieved in steel coupling beam subject to cyclic shear loading with web shear yielding failure. Compared to traditional steel coupling beam which sets stiffeners on the web, the local buckling of the new type of steel coupling beam with shear yielding will not occur, before the steel web reaches its ultimate shear strain, resulting in excellent energy dissipation capacity. Eight quasi-static tests on buckling constraint steel coupling beams with shear yielding had been carried out to study the impact of various constraint manners on seismic behavior of this type of steel coupling beam. Tests results showed that all the test specimens realized shear yielding and strengthening of bearing capacity, and major failure mode included weld joint fracture between flange and endplate and failure of constrained plate. Average over strength factor of the test specimens was 1.38, above 1.1, the minimum requirement of Code for Seismic Design of Building Structures. Among them, the over strength factor of test specimens which used 50 mm-thick reinforced concrete constrained plates and 25 mm-thick wooden constrained plates exceeded 1.5. Test specimens with different constraint methods showed similar yield shear strain. While test specimens without constrained plates showed the minimum ultimate shear strain, test specimens with 25 mm-thick wooden constrained plates showed the maximum, approaching the ultimate shear strain of the web's steel in material property test.