Energy Dissipation Performance Of Outriggers In Super-tall Buildings With Outrigger Systems

The concept design of outrigger truss strengthening system of super-tall buildings has experienced from the rigid strengthened storey to the"limited stiffness"'strengthened storey,but the essence has not changed that the strengthened storey leading to mutation of structural stiffness and member force.It has always been a key research topic that how to improve the seismic design of strengthened storey to make a ductility yield mechanism under rare earthquake.With the development of construction technology,the design trend of outrigger is more efficient and reasonable.In addition to conventional outriggers,buckling-restraint-brace outriggers,damped outrigger,and other forms of new type of outriggers are coming into the sight of engineering design.Comparing to the outer frame,the outriggeris are less restricted by architectural layout.Through the study on its energy dissipation mechanism and setting method,the obtained results are more universal.At the same time,the improvement of outrigger can both reduce the stiffness mutation of strengthened storey and strengthen the energy dissipation of outrigger truss,which will broad the application prospects.Based on the frame-core tube-outrigger system,a common lateral force resisting system of the super-tall building,two engineering projects who have single-outrigger storey and multi?outrigger storeies are chosen.The mechanical properties and energy dissipation performance of super-tall buildings with conventional outriggers,BRB outriggers and damped outriggers are studied by experimental study,numerical simulation and theoretical deduction.The following summarises the main achievements made throughout this research.(1)The seismic performance objectives of outriggers and the whole building and the energy dissipation mechanism are summarized by surveying the tall buildings under construction or completedat home and abroad.The corresponding advantages and disadvantages of tall buildings outrigger design are pointed out.(2)For conventional outriggers,BRB outriggers and damped outriggers,the reliability of the numerical model is studied by comparing the numerical prediction results with the components tests.Numerical simulation method is determined for the former three types of outrigger in super-tall building.(3)Taking the single outrigger super-tall building as the research object.the seismic performances of super-tall buildings are studied about the three types of outrigger system,including the storey drift ratio,period,displacement ratio,stiffness ratio,stiffness mutation and internal force mutation at outriggers,and performance goal of structructure,etc.So the engineering design principles are identified for the three types of outrigger,which will provide basic models for the following study.(4)The energy dissipation performance of super-tall building with single outrgigger is studied on the three types of out riggersystem.Using energy dissipation and structural damage as indicators,the energy dissipation performance ofwhole structure and the energy contribution of outrigger,as well as the degree of plasticity of overall structure and key components under rare earthquake,are comprehensively evaluated.The results show that the BRB outrigger and damped outrigger have better seismic performance under rare earthquake.Damped outrigger system shows a better performance on controlling the core tube damage,while BRB outrigger system performs better on displacement response control.(5)Taking multi-outrigger super-tall buildings as the research object,the BRB outrigger super-tall building was studied systematically.Using energy dissipation and structural damage as indaicators,sensitivity analysis was carried out on the set position and number of BRB outriggers along the building height.Results show that buildings with BRB outriggers located in the middle height has best performance and efficiency.Sensitivity analysis provides valuable reference conclusion for the design of multi-outrigger tall buildings.