Study On Similarity Theory Of Scale Model In Compartment Fire Test Of Cross-laminated Timber

As a building material,wood has the advantages of low density,high strength,easy processing,beautiful texture,good thermal insulation and seismic performance.It is an excellent renewable building resource.However,due to the combustibility of wood,people are generally skeptical about the fire resistance of wood structure buildings,resulting in the slow development of high-rise timber structures for a long time.The construction experience abroad shows that the cross laminated timber(CLT)structure has gradually become the main structural form of multi-story and high-rise timber structure due to its excellent mechanical performance,but its fire resistance is still generally concerned by designers.At present,there is no relevant standard for fire resistance design of CLT structures in China,so in order to promote CLT structures in China,it is necessary to improve the fire resistance design method of CLT structures.In view of the high cost and material resources of full-scale CLT room fire test,the research of domestic scholars on the fire resistance of CLT structure tends to the component level,so it is imperative to establish the similarity theory of natural fire test of CLT room,so as to carry out the natural fire test of scaled CLT room.In this paper,theoretical derivation,experimental research and numerical simulation are combined to study the similarity theory of natural fire test in CLT room protected by fire protection,and to analyze the dynamic effect of partial exposure of CLT in the room on fire.The main research contents are divided into the following parts:(1)Based on the research results of previous scholars,the similarity theory of CLT room fire test with fire protection is established.The parameters considered in the similarity theory include the type of fire protection materials in the room,the thickness of the fire protection layer,the thickness of the CLT wall plate,the fire power and the size of the vent.The numerical calculation of the example is carried out by the biregional model B-RISK simulation software and Abaqus finite element software to verify the correctness of the similarity theory.(2)The similarity theory was used to design the fire test of the CLT scaled room with full coverage of the fire protection layer.The scaling method of room boundary material with temperature variable was proposed to select the fire protection layer material of the scaled room and design the thickness of the fire protection layer.(3)Four scaled compartment fire tests with full protection of fireproof materials were conducted,in which the 1:3 scale test and the 1:4 scale test were conducted twice each.The test phenomena were recorded and analyzed to verify the similarity of key test phenomena,flame height and carbonization of CLT components after fire.The test data were analyzed and compared to verify the similarity of indoor temperature,internal temperature of fireproof materials and mass loss rate of combustibles.(4)The scaled compartment fire test of the ceiling partial CLT exposed room was carried out,and the scale ratio was 1:3.The compartment fire test results were compared with the corresponding full protection room of fire retardant materials,and the contribution of partial CLT to the fire of the scaled CLT room was obtained.(5)In FDS fire simulation software,the wood combustion heat release model suitable for ventilationcontrolled fire,the residual charcoal combustion model after wood stack combustion and the numerical simulation method of ventilation-controlled room fire with wood as fuel were established.This method was used to numerically simulate the five room fire tests and other fully protected room fire tests in this paper,and the accuracy of this method was verified.