Seismic Performance Analysis And Optimized Design Of Primary-secondary Hybrid Structure With Buckling-restrained Braces

The high-rise primary-secondary hybrid structure is a new type of building structure system.The primary-secondary structure force transmission mode is clear,and it has a very high assembly rate.The primary structure is the main load-bearing and lateralresistant system.Due to the high floor height and large span,the simple frame structure can provide limited lateral rigidity.The buckling-restrained brace not only provides lateral stiffness but also has the advantages of shock absorption and energy consumption,and has been widely used in practical engineering projects.However,the application of buckling-restrained braces in high-rise primary-secondary hybrid structure still lacks theoretical research and design guidance.Based on this,this paper relies on the demonstration project of the subject to study seismic performance and optimization design of primary-secondary hybrid structure with buckling-restrained braces.The main contents and conclusions of this article are as follows:(1)The light steel secondary structural unit in the high-rise primary-secondary hybrid structure is designed,and the overall performance and economics of the structure under the two types of light steel secondary structural schemes of "half frame" and "full frame" are compared.The analysis results show that the light steel secondary structure in the form of “half-frame” can meet the overall structural performance requirements,and can greatly reduce the number of beams and columns arranged in the secondary structure and reduce the weight of the secondary structure unit compared with the “full-frame” form.Reduce the total cost of the structure,and the space utilization rate is also higher.(2)Compare the influence of different primary-secondary structure connection methods on the deformation of primary-secondary hybrid structures and the distribution of internal forces of components.The analysis results show that,because the lateral stiffness of the primary structure is much greater than that of the light steel secondary structure,different connection methods have little effect on the overall structure and the mechanical performance of the main structural frame.Using the primary-secondary structure connection method of horizontal articulation and vertical release of axial stiffness in this article can effectively reduce the internal force of the secondary structure beam and column,which is conducive to a more lightweight secondary structure modular design,and the connection method is also more convenient for assembly construction.(3)The anti-lateral force system of the primary-secondary hybrid structure of highrise is designed,and the primary-secondary hybrid structures of ordinary support and buckling-restrained braces are established respectively.Using pure frame structure as a reference,elastoplastic time history analysis under 7-degree rare,8-degree rare and extremely rare earthquakes was carried out.The structural dynamic response,energy dissipation and component performance status were compared.The results show that the primary-secondary hybrid structures with buckling-restrained braces are better than ordinary braces in terms of structural dynamic response and structural energy consumption.The buckling-restrained braced primary-secondary hybrid structures are basically not damaged during earthquakes.The buckling-restrained braces as the first line of defense can also protect the primary structural frame well.(4)On the basis of the equal stiffness replacement method,in order to improve the utilization rate of buckling-restrained brace,consider the mixed support arrangement scheme to optimize the structure.The elastoplastic analysis results of 8-degree rare earthquake and extremely rare earthquake were compared for the mixed support layout schemes with different replacement rates.Considering comprehensively the improvement of the seismic performance of the structure and the input benefit of the buckling-restrained brace,a reasonable replacement rate of 36.7%-56.7% was determined to provide a reference for the design.(5)Design multiple high-rise primary-secondary hybrid structure with different stiffness ratios,study the impact of stiffness ratio on its seismic performance,and determine the reasonable range of lateral stiffness ratio for this structure.The variable stiffness design is used to optimize the design with a fixed stiffness ratio of 2.The results show that the variable stiffness ratio design can improve the seismic performance of the structure on the premise of the same amount of support steel;on the premise of the same seismic performance,reduce the amount of steel used for buckling-restrained brace.