Optimization Design Of Buckling-Restrained Braces In High-Rise Steel Structure's Energy-Dissipation

As a novel energy-dissipation member, buckling-restrained brace (BRB) shows the same load deformation behavior in both tension and compression, and dissipates dynamic energy through stable hysteretic behavior and is gradually used to resisting earthquake in structures. It makes the overall cost of the structure with BRBs increasing significantly that the price per BRB is much expensive due to yield part's core member of BRB requiring special steel and BRB needing special measures in details and the needs of expertise in making and assembling BRB, and the optimal design methods about BRB structure are immature. Taking into account high cost of BRB's yield part, this paper will optimize the BRBs in high-rise steel frame structure with the length and cross-section area of BRB's yield part as the design variables in order to reduce the amount of BRB and lower overall cost of structure to promote the application of BRB. The main contents of dissertation are as follows.(1) According to the characteristics of BRB's mechanical behavior, the paper will study the modeling method of BRB in structure from its composition, deduce the necessity of modeling BRB with three-part and present the three-part method based on the Abaqus software. Through exploring the principle of selecting structure analysis method in optimum design of large-scale structures and comparing several modified modal pushover analysis (MMPA) methods, a synthetical MMPA method will be presented as a suitable structure analysis method for this paper's optimization problem.(2) Based on current several effective structure optimization methods, optimality criteria method as the suitable method for this paper's optimization problem will be proven. Then, this paper will deduce the formulas to compute the length and cross-section area of BRB's yield part. Through study the full-stressed method and full- displacement method, this paper will also find a better optimality criterion, the full-drift-angle criterion, for this paper's optimization problem, demonstrate its feasibility and give the formulas to optimize the length and cross-section area of BRB's yield part.(3) Starting from the energy balance concept and combining with the function of BRBs in structure, energy criterion will be given as other suitable criterion for this paper's optimization problem, its feasibility will be proven, and the formulas to compute earthquake input energy, BRB's hysteretic energy and the optimization formulas will be presented, too.(4) Based on the Abaqus/CAE module, the three-part modeling method of BRB, the synthetical MMPA method, the full-drift-angle method and the energy method will be programmed in Python in order to apply and popularize these methods more easily. And the effect of the optimization methods in this paper will be demonstrated by the results of an example comparing the full-drift-angle method and the energy method with the non- optimal general method of designing BRB structure using the programs.