The Research On The Application Of Buckling Restrained Brace Made Of Magnesium Alloy

Recently, energy dissipation bracing system has been widely used in structure seismic design and strengthening design of existing structure and buckling-restrained brace(BRB) is one of the most common forms.BRB is a special axial force component with steel core which can reach and retain full section yielding under compression and tension. Magnesium alloy is a kind of high performance material with low weight, high strength and large deformation capability, so it has been applied in military, aviation, automobile. But as far, there is no application in civil engineer. In this paper, magnesium alloy is used to replace steel as the core of BRB in part or whole, and the feasibility and the advantage of this work are researched by theoretical analysis and numerical simulation, which can provide essential theoretical basis for producing magnesium alloy buckling-restrained brace(MABRB).The main contents of this paper are follow:1. Though analyzing the basic composition of BRB, the calculating formulas of some quantities such as equivalent section area, equivalent stiffness and strength are derived; Based on stability condition, the precondition for BRB and the stiffness threshold of constraint element also are derived.2.Taking the example of two concrete frame structures arranged by steel buckling-restrained brace(SBRB) and MABRB respectively, the displacement, story drift, shear force and axial force of structures are compared under frequent and rare earthquake actions. Result shows that MABRB performs better than SBRB in reducing displacement and residual deformation of structures.3.By taking the example of a steel frame structure of the main building of thermal power plant which doesn't satisfy seismic demand, three kinds of BRB including MABRB,SBRB and hybrid buckling-restrained brace combining steel and magnesium alloy(HBRB) are used to improve seismic performance of this structure.(HBRB is designed by making stiffness equal and fully playing the material deformation capacity and material strength).After comparing the effects of these BRB, it has been found that MABRB is better than SBRB in self-centering function, and combining the main advantage of SBRB and MABRB,HBRB has higher bearing, deformation and restoration capacities.In this paper, the feasibility and the potential advantage of MABRB are discovered by theoretical analysis and numerical validation, which further broaden applying scope of magnesium alloy and provide a basis for developing the new dissipation brace.The innovative points of this paper can be summarized as follows:1. Considering the high performance of magnesium alloy, the idea of MABRB is proposed and the feasibility and the advantage have been validated.2. Two composition scheme of core material for BRB are proposed, i.e., pure magnesium alloy and a hybrid of magnesium and steel.3. The general rule for design of HBRB is proposed and its efficiency is verified by comparing the improvement in seismic performance and economy.