Study On The Mechanical Behavior Of Frame-Core Tube Structure With Strengthened Story

In high-rise and super high-rise building,the displacement of the frame-core tube under lateral loads often exceed the national standard limit because of the lack of the overall lateral stiffness.In order to solve this problem,structure engineers usually arrange strengthened stories in the building structure to enhance the lateral stiffness.This will cause the sudden change of internal force and deformation near the strengthened stories due to the uneven vertical stiffness,which makes it difficult to form a good yield mechanism.In this paper,based on the summary of the research on the frame—core tube with strengthened stories at home and abroad,a 40 layer frame-core tube model is established by finite element analysis software ETABS,which mainly studies the influence of different quantity,different stiffness and different types of strengthened stories on the performance of the structure under wind load and earthquake.The main conclusions are as follows:1)The setting of the strengthened story can significantly reduce the lateral displacement of the structure,and the greater the number of stiffness is,the less the lateral displacement of the structure will be.2)The setting of the strengthened story will make the internal force of several structural members near the strengthened story occur mutation 2 to 8 times,and with the increase of stiffness the mutation will be more violent,which leads to forming weak layers that are not conducive to seismic resistance.However,once the strengthened story increased,the number of internal forces of mutation will decrease,which is propitious to the earthquake resistance.3)Compared with the rigid strengthened story,the finite stiffness strengthened story can reduce the structural mutation degree by 20%?40%,and it will reduce the axial force of the frame column 1/3 by setting the ribbon truss.4)Elastic time history method reveals the local seismic response characteristics of the structure.Its analysis results are generally less than the modal response spectrum method,but there are still individual exceptions in which the time history method and response spectrum method should be chosen for the most unfavorable situation of envelope design.5)In Pushover analysis,when the displacement of the target is thrust to after setting 1?2 to strengthened story,the ductility of the structure is the best,and when the strengthened story is not set or set three layers,the structure will suffer napped damage.It is indicated that the existence of strengthened story delay the structural damage,but the quantity is not the more the better.6)The model can find the performance point under rare earthquake,with the increase number of strengthened stories,the acceleration spectrum at the performance point increases gradually,and the displacement spectrum decreases gradually;meanwhile,the structure of base shear increases,but vertex displacement decreases gradually.7)There will be a column hinge near the reinforcement layer with strengthened story.That not meets the requirement of the structure of "strong column and weak beam".strengthened story of plastic hinge arm is carried out early than the shear wall of plastic hinge,in accordance with the requirement of "Strong cylinder,weak arms ".