| In the process of rapid economic development and the acceleration of urbanization,the problem of rapid population growth in the central city and the contradiction of limited land resources have brought a lot of inconvenience to people’s lives and production,and this problem needs to be urgently solved.In order to maximize the use of land resources,domestic architects adopt the method of continuously increasing the height of structural buildings.In the development of the last ten years,China has built some well-known 200 m ～ 400 m super high-rise buildings,the structure of which is mostly in the form of steel frame-core tube.In order to reduce the performance difference between the steel frame and the core tube due to the effect of shrinkage and creep of the material,the floor beams are made of I-shaped steel beams,and the outer frame is made of steel reinforced concrete or steel tube concrete columns to form a hybrid frame-reinforced concrete core Mixed structure of the barrel.The choice of hybrid frame-reinforced concrete core tube(hybrid)structure has many obvious advantages.For example,the cost of concrete is relatively low,the technology of steel structure is relatively mature,and the labor cost is relatively low compared to foreign construction.Therefore,choosing this structure can create better comprehensive benefits,and it is currently one of the most suitable high-rise building structure forms in line with the basic national conditions of China’s basic construction.Research and development of this hybrid system has great practical engineering significance.Because the super high-rise buildings are greatly affected by wind loads,it is necessary to study how to improve the overall lateral stiffness of the structure through the structural system and structural measures to ensure the structure of the "double lateral force system".Previous studies have found that the arrangement of the reinforcement layer can effectively make the surrounding frame columns function to enhance the lateral stiffness of the entire structure.However,the setting of the strengthening layer under the action of earthquake will cause the structural stiffness and internal force to change suddenly,and it is easy to form a weak layer.The damage mechanism of the structure is difficult to show the ductile yield mechanism of "strong column and weak beam" and "strong shear and weak bending".In the preliminary research of the research group,we found that the use of box-shapedsteel beams as given in the "Steel Structure Design Standard" GB50017-2017 as the main beam of the floor may be one of the effective methods to solve the adverse effects of the reinforcement layer.Because the main beam of the floor is rigidly connected with the outer frame column and the hinge of the concrete core tube,the outer frame can allocate the most floor shear force and overturning bending moment,which has better economy and higher structural redundancy.Therefore,the box girder main beam should be rigidly connected to the surrounding rectangular steel tube concrete frame column and hinged to the concrete core tube.Based on the actual project,this paper studies the box girder to replace the main girder of the I-shaped floor,in order to provide a new way of thinking for the design of super high-rise buildings when the reinforced layer method is not used to meet the requirements of the current code,so that the structure does not appear weak.The structure maintains good lateral displacement resistance and seismic performance,while avoiding sudden changes in stiffness and internal force at the reinforcement layer.Based on some practical projects,this paper studies the structural analysis indexes of the hybrid frame-core tube super high-rise structural system with box beams instead of I-shaped floor main beams.The main research contents are as follows:(1)Based on the Hainan Building project,the stress and deformation characteristics of the mixed frame-core tube super high-rise structure with reinforced layers under horizontal load are investigated,and the box beam is used to replace the main beam of the I-shaped floor.Strengthen the structure of the layer,combined with the structural control indicators such as the displacement angle between the layers of the structure,the shear weight ratio and the frame to bear the shear force to discuss and analyze the two,and give structural design suggestions.(2)The hybrid frame-core tube super high-rise structure with seismic intensity of 8degrees,7 degrees and 6 degrees respectively is analyzed by using box beams as the main beams of the structure.When the index requires,the frame height of the frame-core tube structure buildings with different fortification intensity areas uses box beams instead of I-shaped floor main beams.(3)In order to ensure a reliable connection between the box-shaped steel beam and thebox-shaped column,and to promote the engineering application of the box-shaped steel beam,a new box-beam-square steel tube concrete column joint bolted and welded cover plate reinforced connection is proposed.After demonstrating the precise certainty of the finite element simulation,the finite element software ABAQUS was used to analyze the parameters of the new connection node to clarify the impact of the changes of each parameter on the seismic performance of the node model,and the design recommendations of the connection were given.Through the analysis of the overall structure,the main conclusions obtained: the use of box-shaped beams as the main beam of the floor in the frame-core tube,whether under earthquake action or wind load,the use of the box-shaped main beam scheme structure The floor displacement and floor displacement angle are better than the structure of the I-shaped beam scheme;using the box beam as the main beam of the structural floor can effectively solve the weak layer and the structural rigidity and internal force mutation caused by the original structure with the reinforcement layer;box shape The beam is more advantageous in reducing the floor height and improving the economics of the structure.When the eight-degree fortification Hainan Building project uses box-shaped beams instead of structural I-shaped main beams,up to two more floors can be added,the height is increased by 7.6m,and the height limit of the building is 197.05m;When the number of structural floors is 52,the height increases by 60.2m,and the building height limit is 231.25 m.At this time,all structural control indicators can meet: the six-degree fortification intensity of Nanchang Huahao Center mixed frame-core tube structure floor can increase by one The height of the building is increased by 3.9m,and the height limit of the building is 255 m.Through the analysis of the mechanical properties of the reinforced connection nodes of the cover plate,the main conclusions are obtained: it is recommended that the upper cover plate be rectangular cover plate,the cover plate length is(0.4-0.8)hb,hb represents the beam height;the same. |
