Research On Design Method Of Staggered Truss Steel Frame Structure RC Floor System Under Horizontal Earthquake

The American code refers to the floor system that bears and transmits horizontal loads as transverse partitions,which are usually composed of floor slabs,tension and compression chords,shear "collector" members,and connections between floor slabs and vertical members.In the staggered truss steel frame structure,the floor as an important part,not only directly bears and transmits the vertical load,but also redistributes the horizontal load to each truss position,and transmits it from the upper truss to the lower through the floor slab Adjacent truss.The floor system under the horizontal load is like a deep beam under the lateral load.Therefore,the design of the floor cover in the staggered truss steel frame structure is particularly important.However,in the design of the existing staggered truss structure floor system,the internal force of the floor slab under the vertical load is first calculated and reinforced,and then the shear bearing capacity in the plane of the floor slab is checked.This process ignores the internal tension of the floor system.Design of chord and shear "collector" components.This paper takes the staggered truss structure floor system as the research object to study its design method under horizontal earthquake action and its mechanical performance under monotonic horizontal load.The main research contents and results are as follows:(1)Investigated the anti-seismic design methods of cast-in-place reinforced concrete floors,precast concrete floors,and composite floors abroad,and summarized the antiseismic design methods and procedures of the floor system.Combining the calculation method of the shear force of each layer of the staggered truss structure under the horizontal load and the simplified beam model for calculating the internal force of the floor system,the above design method is applied to the floor system of the staggered truss structure,and the staggered truss structure building is given.The detailed process of cover design.(2)An 8-story staggered truss steel frame structure test specimen was designed according to the standard method,and then the floor cover of the test specimen was designed using the obtained floor system design method,and the tension and compression chord and "collector" were obtained by hand Detailed design information of components and connections between floor and vertical components.Using ABAQUS finite element software to carry out finite element modeling of the specimen,extract the shear force of each layer and each truss under the design lateral force of the specimen,and compare with the results obtained by hand calculation.The results show that the finite element The calculation results are in good agreement with the hand calculation results,and the error is within 10%,which proves that the proposed floor design method is feasible.The parameter analysis of the structure is carried out,the influence of the seismic fortification intensity level,the number of floors and the number of open webs on the shear forces of each floor and each truss is analyzed,and the corresponding design suggestions are put forward.(3)Established a refined model of a test specimen in the literature.Its performance under cyclic loading is analyzed,and the hysteresis curve and skeleton curve obtained from the analysis are in good agreement with the test results,which verifies the feasibility of the modeling method.Then monotonically load the model to analyze its mechanical properties and failure modes.Later,the local design conditions of the structure were changed,and the failure modes and mechanical properties of the structure under different conditions were studied.The results showed that increasing the strength and stiffness of the upper chord would make the upper oblique web members yield first,and then the concrete slab would enter plasticity;At the same time,increasing the stiffness and strength of the upper chord and web will make the concrete slab enter the plastic stage first.(4)Carry out refined modeling on the bottom two layers of the designed 8-layer test piece.Two models were established respectively,one of which ignores the effect of slip between the floor and the truss and does not set studs;and the other considers the effect of slip.Research on the failure mode and bearing capacity of the structure under monotonic horizontal loads,the results show: whether to consider the slip between the floor and the truss has a greater impact on the bearing capacity of the structure,the bearing capacity of the structure without the slip is better than the considered 9.6% larger;the final bearing capacity of the two models is 46% and 33% larger than the design load,respectively,verifying the feasibility of the proposed design method.