Multi Scale Fire Resistance Test And Evaluation Of Integral Frame Based On Single Column Test Substructure

Test and numerical simulation are two important research methods to study the fire resistance performance of structure.Through the real fire test on the local components or the whole structure,the damage and internal force changes of structure under fire can be more truly reflected,but there are some shortcomings,such as high cost and complex boundary conditions.Only numerical simulation of structure can simulate the conventional structure with low cost However,it can not accurately reflect the real stress of special structure or key parts under fire.The hybrid test method can take into account the advantages of both physical test and numerical simulation.The component with strong local nonlinearity under fire is used as the test substructure for fire test,and the rest is used as the numerical substructure to establish the finite element model for numerical simulation.The boundary conditions of the two sections are interacted in real time to realize the complex test response of simple component Fire resistance of the whole structure.At the same time,in order to improve the real-time interaction efficiency of the test substructure and the numerical substructure and ensure the calculation accuracy,the numerical substructure adopts the multi-scale modeling method.In view of the above methods,this paper takes a four story four span reinforced concrete frame as the whole structure,studies the advantages of multi-scale modeling method and the feasibility and applicability of combining multi-scale modeling with mixed test method under the conditions of four sides fire of the ground floor central column and four sides fire of the ground floor central column after earthquake damage,and carries out mixed test under the fire conditions after earthquake damage The correctness of fire resistance mixing test is verified by real test analysis.The details are as follows:（1）Four models of reinforced concrete traditional single column,all solid element plane frame,multi-scale plane frame and hybrid simulation plane frame are established.The fire resistance performance of the whole structure based on the fire condition of the bottom middle column is compared and analyzed.The calculation efficiency of different modeling methods,the influence of constraints on the fire resistance,and the difference between hybrid simulation and conventional numerical simulation are studied.The results show that: in the case of fire,the constraints of the surrounding components have a great impact on the fire resistance of the components;the multi-scale modeling method can greatly improve the calculation efficiency and ensure the calculation accuracy;the multi-scale fire hybrid simulation method can better reflect the mechanical properties of the whole structure under fire.（2）Three models of full-body element frame,multi-scale frame and multi-scale hybrid simulation frame are established to analyze the dynamic response under earthquake action.Then the fire resistance performance of the frame after earthquake damage is analyzed,and compared with the undamaged fire structures in Chapter 3.Finally,the influence of damage on the fire resistance performance of the damaged frame is considered,and the difference between them and earthquake action is explored And evaluate its applicability in hybrid simulation.The results show that: under the fire condition after earthquake damage,the influence of mechanical damage and geometric damage on the fire resistance performance of the structure is quite different;the multiscale modeling method can ensure good calculation efficiency and accuracy under the fire condition after earthquake;the multi-scale fire resistance hybrid simulation method can better reflect the mechanical performance of the structure under fire.（3）Through the above hybrid simulation of fire resistance and post earthquake fire resistance of reinforced concrete frame,combined with the actual hybrid test method,the fire resistance hybrid test of the test substructure after earthquake damage is carried out,in which three specimens are analyzed by dynamic time history analysis and one specimen is analyzed by static time history analysis,and the high temperature fire resistance test of these four specimens is carried out to further explore the application in the real earthquake and fire conditions At last,the feasibility of the mixed test method is discussed.The test results show that when the multi-scale hybrid test method is used to study the fire resistance of earthquake damaged frame,the deformation of the whole structure can be approximately reflected by simple components,which provides a lowcost,high-efficiency and certain accuracy analysis method.