Seismic Retrofit Design Of A Frame Building Using Braces With Hysteretic-type Energy Dissipation Properties

Building codes generally use strength as the main design criterion as thebase of the earthquake resistant design and use ductile energy dissipationmechanism induced by the servere damages of structural members to meetseismic requirements.For example, the seismic resistance capacity of framestructures is at the cost of its beam and column damages. The application ofbraces in frame structure has improved this situation. However, ordinary braceswill be out of action prematurely due to bucklling under pressure. Therefor, thisstudy seeks to use buckling restrained braces (BRB) as replacable reinforcingdevices to add to frame structures additional fortification lines and energydissipation capacity, so that the primary structure could avoid being damaged forlarge deformation. In addition, this study proposed a direct displacement-baseddesign method to quantify the seismic demand and and determine the designparameters of the BRBs. The device and method are applied to the strengtheningpractice of a gallery-type frame structure. The analysis resaults show that, due tothe lateral confinement around the core steel, the BRBs take the lead in yieldingto consume energy without losing stability in the seismic cyclic loading. Thebrace show a good hysteretic performance, and thus achieve the ideal seismicmitigation effects. The specific work contents are as follows:1. Summarize the damage characteristics of RC frame buildings and thedevelopment evolution of BRB design.2. Describe the method and procedures of earthquake performanceestimation using pushover analysis and displacement-based methods (DBM) todetermine the parameters of retrofitting BRBs.3. Analyze the energy dissipation principle of the BRBs, and elaborate thesimulation and layout principles in the frame structure. Design and construct agroup of BRB member, and check the capacities of bearing plates and bolts.4. Model, simulate and analyze the structure using the finite elementanalysis software SAP2000. Apply the Pushover and DBM methods to a buildingof Xuankou Middle School which had been severely damaged in the WenchuanEarthquake, and compare the pre-amd post-retrotting performance of thebuilding.5. In the nonlinear static analysis, analyze the development mechanism ofthe plastic hinges, allocate the required stiffness and BRBs by target displacementdemands, and thus quantify the retrofitting design. Then the efficiency of thestrategy is validated using time history analysis with earthquake record inputs.