Cyclic behavior of metallic damper connected reinforced concrete beam-column joint with an opening in slab

Abstract

The study proposes a solution of constructing the inevitable rectangular opening in the reinforced concrete (RC) slab upon the metallic damper for the RC beam-column frame to alleviate the adverse effect of the slab for the system compared to the designed bare frame joint. To systematically understand the cyclic behavior of the system, a quasi-static test is conducted on two half-scale specimens, and a parametric study is carried out to explore the effects of the rectangular opening of the RC slab along with the top and bottom flanges of the damper on the hysteretic responses of the system. Test results show that the positive and negative bearing capacities of the system are asymmetric because the centroid shifts upward from the middle of the metallic damper and RC beam. Although the intervention of opening in RC slab for the dog-bone damper connected RC joint is hard to mitigate the additional stiffness and bearing capacity from the slab to the system, such application could restrain the out-of-plane instability of the dog-bone damper by about 21.74% and improve both loading capacity degradation and energy dissipation degradation of the system. Furthermore, numerical results confirm that the distance of opening from the RC slab significantly decreases the depth of the neutral axis of the RC beam with the slab so that the bearing capacity and initial stiffness of the system improve by about 26.47% and 27.88%, respectively, as the distance of the opening to the damper reduced from 0 mm to 60 mm. Moreover, benefitting from the significant influence on the depth of the neutral axis, the bottom flange of the dog-bone damper, especially the flange width and weakened depth of the damper, has a significant improvement on the hysteretic responses of the system.