Research On Seismic Performance Of High-rise Diagrid System With Load-bearing Buckling Restrained Braces

With the rapid development of the world economy,the structural system of high-rise buildings has become more and more popular.The diagrid structure of high-rise buildings has better spatial properties and higher shear stiffness.So far,limited research has mainly focused on the elastic characteristics of this structural system and the oblique column joints.Research on the performance of this structure under earthquake action is relatively scarce.The ductility of the traditional oblique structure is very limited.Under the action of a large earthquake,the structure is prone to brittle failure,resulting in huge repair costs.The main functions of Buckling Restrianed Brace（BRB）applied to construction engineering structures include providing additional damping and providing lateral stiffness to a certain extent.The energy-dissipating buckling restraint bracing corresponding to the former has been widely used in building reinforcement and renovation.The corresponding load-bearing BRB with high-strength core material and high load-bearing capacity has relatively few applications.This type of BRB can meet certain consumption requirements.At the same time,it has the characteristics of high load-bearing properties and relatively small cross-sectional dimensions of components under the same load-bearing conditions.It has significant application advantages for the diagrid structure of oblique columns to bear the axial force.Based on the existing research,this paper uses finite element software to perform non-linear static（Pushover）analysis and dynamic time history analysis on the numerical model,so as to study the improvement of the energy dissipation capacity of the load-bearing BRB on the oblique structure.as follows:（1）Design a traditional diagrid structure model of 24 floors with a plane size of36m×36m and a storey height of 4.5m.Based on the principle of equal material usage,calculate the dimensions of each component of the corresponding oblique structure,and design a plane with the same dimensions 36m×36m,a 24-story high-rise diagrid structure model with a height of 4.5m,combined with the specifications of the specifications,the two models are subjected to modal analysis,mechanical performance analysis under vertical load,horizontal load,and response spectrum analysis comparison.（2）Based on the existing research and the model designed in the previous article,the parameters of the BRB components required in this paper are calculated by the equivalent stiffness method,and the normal oblique angles of 45°,63° and 72° are established using SAP2000 finite element software.The numerical model of the diagrid structure,referring to the optimal layout mode of ordinary BRB in the middle half of the diagrid structure given by the existing research,and proposes a new layout mode of the BRB in the oblique structure based on the magnitude of the axial force.That is,symmetrically replace the half of the oblique column with the larger axial force with the load-bearing BRB member on each layer,and conduct a study on the mechanical properties of the structure.（3）Non-linear static force（Pushover）analysis is performed on the established ordinary diagrid structure model and the skew structure model with load-bearing BRB,and the static pushover curve and overall lateral stiffness curve of the model are obtained,and passed The ductility coefficient examines the ductility of the structure,and uses the internationally accepted FEMA P695 method for seismic performance evaluation.Through the study of the seismic performance of the oblique structure with two different BRB layout modes under different oblique column inclination angles,it is found that the oblique structure of the BRB layout mode arranged according to the magnitude of the axial force is better than the BRB layout in the middle of the facade in terms of ductility and overall stiffness.（4）Based on the results of Pushover analysis,the newly proposed load-bearing BRB structure model and the ordinary diagrid structure model are subjected to dynamic time history analysis under three rare seismic waves.The results show that under the condition that the original diagonal column size is not changed,the diagrid structure with load-bearing BRB has better seismic performance than ordinary diagrid structures,and the diagrid structure with load-bearing BRB is also suitable for the optimal oblique structure with fixed aspect ratio.The condition of the column inclination angle is that when the optimal inclined column inclination angle range is satisfied,the lateral stiffness and ductility of the column are higher than the other angles.