| The steel structure are widely used in conventional building in high seismic regions of China with features of high-strength,good plasticity and toughness,light weight and good seismic performance.However,the steel moment resisting frames(SMRF)may cause layer failure mechanism and allow the formation of soft stories due to their lower lateral stiffness,which may lead to serious consequences under strong earthquake.The strength and stiffness degradation of structural component is the main reason for the collapse and damage of building structure under a strong earthquake.In order to limit the structural lateral displacement in the specification limits,the common design of SMRF is improved the structural stiffness by increasing section size or adding component.But this method of designing is obviously waste of resources,costly,and not comply with the ductility design criterion of steel structure.For this reason,The application of SMRF is limited by many restrictions in high-rise building.Thus,a new lateral force resisting structure system is presented to improve the seismic performance of SMRF.The buckling restrained brace frames systems(BRBFs)is an improvement as a kind of high-performance energy-dissipated structure system compared with SMRFs,which is used extensively for resisting lateral forces in high seismic regions of China.By adding vertical brace component between the main frames,the brace component will bear partial horizontal shear,so that the overall lateral stiffness of the BRBF will be improved.The steel structure with buckling restrained brace can effectively protect the main frame and control the horizontal lateral displacement through the brace to absorb most of the seismic energy under the action of earthquake,which can avoid the defect of SMRFs with smaller lateral stiffness.According to the strength of the frame index of the first-floor shear-weight ratio(CB),the present thesis designed 6 sets of 20 moment-resisting steel frame and buckling restrained braced steel frame models based on the current seismic design code.In high-rise steel frame,the P-delta effect is usually remarkable.Under such consideration,with or without considering the P-delta effect as one of the seismic design parameters to evaluate the impact of seismic behavior for building structures during strong earthquake.The models are studied to investigate the difference of seismic behavior under the same conditions by static pushover analysis and incremental dynamic analysis,respectively.The static pushover analysis(SPA)of each model is carried out by using CLAP software,which is a combined non-linear analysis for plane frame software.Therefore,the influence of different CB value and with or withoutthe P-delta effect on the seismic behavior of the two kinds of frame system is investigated.Further,the Incremental Dynamic Analysis(IDA)of each model is carried out under frequent earthquakes,fortified earthquakes,and rare earthquakes.The calculation results of the distribution of shear force,inter-storey displacement and elastic-plastic energy of two kinds of lateral force resisting structural systems are compared respectively.Based on the code-specified elastoplastic inter-storey drift ratio limit,this thesis analyzed the story shear,the inter-storey drift ratio,the maximum inter-storey drift ratio of collapse limit state,the elastic-plastic energy distribution,and the hysteretic curve of BRB.In addition,it tries to evaluate the effect of the support arrangement scheme on improving the seismic behavior utilized for rehabilitation of steel frames.The energy dissipation must be taken into account in the thesis of energy-based seismic design,so that the dynamic response demands,the damage mechanism of high-rise steel frame storey and its members on such structures are estimated properly.Furthermore,based on the previous research results of multi-particle system,the reliability of the previous multi-particle system conclusion and the evaluation formula of the influence of P-delta effect on high-rise steel frame structure is compared and analyzed.In conclusion,based on these advised vertical location arrangements,two lateral-force-resisting structure system are compared under minor,design and severe earthquake in this thesis.The results show that the CB value is increased,the lateral stiffness of the structure is increased in such system,and the deformation concentration is reduced.The structure can also obviously improve the concentration trend of the damage and reduce the formation of the soft stories.On the contrary,the significant differences were found in BRBF,where the deformation concentration is significantly improved by adding brace.The buckling restrained braced steel frames help to reduce inter-storey drifts ratio,decreasing the probability of failure against ordinary ground motions.The maximum inter-storey drift ratio is also lower than SMRF at same condition,especially the upper storey of structure.In addition,the seismic behavior of SMRF is apparent difference by P-delta effects under rare earthquake,ignoring the P-delta effect may overestimate the lateral stiffness of SMRF,resulting in unsafe design.The stiffness degradation of BRBF caused by P-delta effect can be neglected and undesired collapse mechanisms may not be developed.Therefore,the seismic behavior of BRBF has been greatly improved and has good economic benefits in practical engineering. |
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