Upgrading of reinforced concrete beam-column joints and columns by passive dampers

Abstract

This thesis mainly focuses on development and application of an innovative damping system "Hydraulic Displacement Amplification Damping System (HDADS)". This system can be easily installed at the exterior of beam-column joints to improve seismic performance of structures. This upgrading system is less invasive, and can be readily available to engineers. It also allows amplification of deformation to improve performances of viscous fluid dampers. To understand the dynamic performance of HDADS, investigation was carried out experimentally. Firstly, the hysteretic properties of HDADS were derived via cyclic loading tests. Following, a series of shaking table tests were carried out to assess the performance of HDADS using a 1/3 scale 2-storey prototype steel frame. Allied with this, two identical 1/2 scale reinforced concrete beam-column joint specimens, with non-seismic detailing, were constructed and tested to assess the effects of HDADS on the response of reversed cyclic displacement excitations. In addition, a simple mathematical model representing the HDADS has been developed so as to facilitate numerical analysis of the damping system. Through the shaking table tests, seismic behavior of a 2-storey building is experimentally investigated under four simulated historical earthquakes. The experimental results have demonstrated that HDADS can reduce inter storey drifts of the steel frame by 10 to 25% for moderate seismic earthquakes. Besides, a numerical model of HDADS has been used to carry out numerical simulations of the shaking table tests. The numerical simulations results are in good comparison with those obtained from the shaking table experiments. The beam-column joint tests show that performance of the reinforced concrete beam-column joint during repeated cycles of displacements was improved by installing HDADS. The loads versus displacement responses have shown that installation of HDADS can improve the energy dissipating capacity of the beam-column joint. The improvement is obvious especially when the applied displacement is sufficient large, and the energy dissipating capacity has been increased by up to 150 to 200%. The HDADS is demonstrated to be capable of improving seismic performance of reinforced beam-column joints with non-seismic detailing.