Some Puzzle Analysis In The Design Of A Large Span Cantilever Structure

Large-scale commercial complex buildings generally have the characteristics that the structural unit size is extremely long,the internal atrium setting leads to the large opening of the floor,the partial indoor space with a large span such as a shadow hall,and the large cantilever structure with a localized position and a prominent external wall.Taking the Easy-home's Sanya Living Square shopping mall project as an example.In addition to special research and discussion on a number of regular seismic countermeasures existing in this project,the span on the top floor of the building is large and internal The spatially complex local external picking structure,special research on its solution selection,structural static and dynamic characteristics analysis,component and node design,cantilever structure floor comfort analysis,continuous collapse analysis,construction simulation analysis,etc..The main research work:1)The whole structure simulation analysis uses YJK,MIDAS Gen and other spatial finite element analysis software to analyze the overall structure and the force characteristics of the large-span cantilever structure,and comb the several difficult problems and countermeasures of structural design;2)In order to reduce the outer diameter of the cantilever structure,the cantilever root support frame column adopts the oblique column scheme,in order to reduce the torsional effect of the main structure,the main structure adopts a small wall frame structure system;3)the overall structure adopts performance In order to reduce the weight of the cantilever structure,the space steel truss scheme and the plane steel frame scheme are selected,and multiple schemes are compared to optimize the structural design;4)Elastic dynamic time history analysis uses YJK software to automatically screen seismic waves and MIDAS Gen software for large earthquakes.Static and dynamic elastoplastic analysis under the action,further analysis and review of the bearing capacity of key components;5)Deep analysis of key nodes of the cantilever structure roots using MIDAS FEA finite element software;6)Installation sequence of cantilever steel structure construction It will directly affect the stress state and design reliability of the components,and simulate the structure using MIDAS Gen software.Analysis to study internal force,the influence of the displacement of each step of the construction of the main member;7)Simplified method of sub-cantilevered structure and the floor Comfort checking progressive collapse resistance analysis.Through research,some methods for designing and optimizing the cantilever structure are selected.The design of the cantilever structure must first determine the layout of the main truss,the deformation of the steel,the deformation of the substructure,the internal force of the main components,and the difficulty of construction.The degree of easiness and other aspects are compared in multiple schemes;if there is no condition for the main truss to set constraints on the internodes to ensure the stability of the out-of-plane nodes,the double-layer planar truss can be optimized into a single-layer planar truss system to avoid the formation of internodes;Generally,the stress ratio of the main truss members is not more than 0.85,and the stress ratio of other steel members is controlled within 1.0.Under the premise of ensuring sufficient stress ratio of the members,the simplification of the members and the optimization of the cross-section;the damage degree of the components during static elastoplastic analysis Lighter,most of the dynamic beam-plastic analysis yields,the frame beam cracks,a few walls crack and yield,the frame column basically maintains elasticity,the structure conforms to the conceptual design principle of the strong column weak beam;the key nodes are limited by finite element software Yuan deep analysis,analysis of floor comfort,construction simulation analysis and continuous anti-collapse analysis,further verifying key nodes Safety,ensuring the comfort of the cantilever structure and the reliability of the structure.