Study On Fire Resistance Of Beam-column Joints Of New Fabricated Composite Structure

With the acceleration of urbanization,China’s construction industry is actively advancing the industrialization of new types of construction,focusing on the development of prefabricated buildings.However,as far as China’s current prefabricated structure is promoted,traditional prefabricated concrete structures,steel structures,and wooden structures each have different advantages and disadvantages.In the process of large-scale and rapid development,bottlenecks gradually appear.The prefabricated combined structure can combine the advantages of different building materials and structures,overcome their respective shortcomings,and achieve rapid and efficient development goals with cost control.Under the action of fire,no matter what kind of structure is,structural damage will occur due to material degradation,which will lead to structural damage or even collapse.The resulting safety accident has a severe impact,and it is also very easy to cause serious casualties and property damage.The test of the temperature structure under fire and the seismic performance after the fire on the new structural system are helpful to study its fire resistance and fire resistance,and it is conducive to the popularization of the new structural system.This thesis summarizes the shortcomings of existing beam-column joints of prefabricated concrete frame structures.Based on a new type of prefabricated prestressed steel-concrete composite frame structures proposed by the research group,investigating its mechanical properties under fire and after the fire.The new node makes up for the lack of economics and construction efficiency in the production of prefabricated concrete components of existing assembled concrete frame structures,solves the problem of excessive costs caused by pure steel structures,and combines the advantages of fabricated steel structures and concrete structures.achieve an overall improvement in performance such as durability and fire resistance of the combined structure,Has a good prospect of promotion and application.In this thesis,the fire resistance,fire resistance and post-fire seismic performance of this new node were explored by carrying out a fire test,low-cycle repeated load tests after the fire and numerical simulation analysis.The main work and results of the thesis are as follows:(1)This article introduces in detail the construction of the beam-column connection node of the new prefabricated prestressed steel-concrete composite frame structure and the manufacturing method of the components.(2)Three full-scale joint test specimens are produced in this paper to conduct fire tests and low-cycle repeated load tests after a fire,including ordinary joints,weakened joints with dog bones at the beam end flanges and weakened joints with openings at the beam end webs.After observing and recording the test phenomenon and analyzing and summarizing the test data,the typical cross-section temperature measurement point temperature curves of each test piece were obtained.So do the key seismic performance indicators under the low-cycle repeated tests(destruction mode,hysteresis curve,skeleton curve,yield strength,Ductility,stiffness degradation,energy consumption,etc.).The research shows that the temperature field of the beam-column connection node of the new prefabricated prestressed steel-concrete composite frame structure under fire is in accordance with the basic principles of thermodynamics.The temperature gradient of the concrete decreases rapidly with depth,but the decline gradually decreases.The beam-column connection node of the new prefabricated prestressed steelconcrete composite frame structure can refer to the control method for the plastic hinge outward movement of the beam end of the steel structure frame node.The plastic hinge can be accurately controlled by setting the weakening position and degree of weakening of the beam flange.Energy consumption is achieved by using good ductility and general strength steel.Excluding the design errors of the fire test itself and the abnormal bond-slip of the strands,the hysteresis curve of the node will have a full shuttle shape,with stable bearing capacity and strong energy dissipation capacity,which can effectively improve the seismic performance of the composite frame structure and achieve the purpose of ductile design.The mechanical properties of the weakened form of the beam web opening are not significantly different from ordinary joints,and the ductility and energy consumption are poor.After 60 minutes of fire,the performance of the test specimens declined,but the decline was not significant.(3)Through the finite element analysis platform ABAQUS,the temperature field of the specimen was analyzed under fire;the finite element software Open Sees was used to conduct the modeling analysis under low-cycle repeated load after the fire.The simulation results are compared with the test results to verify the rationality of the modeling method.The ultimate bearing capacity is not less than 95% at room temperature,and the stiffness and ductility are not less than 90% at room temperature.Combined with the test conclusion at room temperature and excluding the abnormal bond slip of the steel strand,the energy consumption capacity does not decrease significantly.Based on the above research work,this article has carried out a comprehensive analysis of the fabrication of the components of the beam-column connection nodes of the new prefabricated composite frame structure,the temperature field under fire,and the seismic performance after the fire.It provides some experimental data and theoretical basis for the further improvement and application of this new node.