Ricky W.K. Chan

Buckling-Restrained-Lug Connection for Energy Dissipation

Under extreme loading conditions such as an earthquake event considerable amount of energy is imparted to a structure. To protect the structure and to minimize damages, a method is to divert a portion of the input energy into designated energy dissipating devices. A new energy dissipation device is presented in this paper. The device is referred to as Buckling-Restrained-Lug (BRL) which can be incorporated in structural joints. The device is composed of a short segment of a steel strut embedded inside a mortar filled jacket which makes the BRLs capacity governed by the squash load under axial tension or compression. The BRL dissipates energy through axial yielding of the steel strut. Analytical, finite element modeling and experimental results of the proposed BRL are presented and compared. Implementation of the BRL in a beam-to-column connection that results in a dissipative partial-moment-resisting joint is proposed. Based on the obtained results, the paper advocates the consideration of the BRL as a viable, compact and low-cost passive energy dissipation device.

Mitigation of Seismic Risks to Soft-Storey Structures Using Toggle-Brace-Damper Systems

Soft-storey mechanism is characterized by a sudden reduction of lateral stiffness in one or more levels of a structure. Soft-storey is often observed in the ground level due to the absence of wall or cladding. With recent develop of energy dissipation systems, soft-storey mechanism can be corrected by addition of a damper-brace assembly. In particular, this paper investigates the effect of toggle-damper-brace systems on such situations. Governing equations including the magnification factor and lateral stiffness contributed by a toggle-damper-brace are formulated. It was found that a toggle-damper-brace system, if proportioned correctly, will significantly increase the travel in the damper and overall stiffness of structure can be enhanced. An illustrative example is presented using nonlinear time history analysis implemented on MATLAB.