Experimental Study On The Fire Resistance Of CLT Floor Exposed To Different Fire Curves

With the continuous progress of the society and the continuous improvement of people's quality of life,the consumption concept of advocating green environmental protection is more and more popular,and green buildings and wooden structures are also widely concerned by people.As a renewable resource,wood is an ideal green building material CLT is widely used in of middle and high wood structures,in case of fire,the fire hazard is more serious than the low-rise wood structure.However,the research on the fire resistance of CLT in China is still in the initial stage.Although some scholars have carried out relevant tests and theoretical studies under the standard fire,CLT,as a burnable material,will increase the fire load density and increase the fire.However,the standard heating curve cannot reflect these characteristics.If only the standard fire heating curve is used to study the fire resistance of the combustible CLT floors,there may be some hidden dangers.In view of the above,it is of great significance to study the structural response of CLT floor under different fire heating curves.This article took the domestic CLT floor as the research object,the mechanical properties of air temperature test and the fire resistance test of CLT exposed to different fire heating curves have been carried out,what's more,the finite element simulation of the mechanical properties of CLT floor and the finite element simulation of the fire resistance of CLT floor based on the finite element platform ABAQUS were carried out.The main content can be divided into the following parts:(1)The flexural strength,rolling shear strength,compressive strength along the grain,interlaminar shear strength and adhesive strength of CLT were tested respectively at air temperature to understand the mechanical properties of CLT.(2)Based on the platform of finite element software ABAQUS,finite element simulation was carried out on the mechanical performance test of CLT,the validity of the finite element modeling method is proved,which lays a foundation for the calculation of the fire resistance of CLT floor.(3)Taking CLT floor as the test object,six groups of fire resistance tests of CLT floor were conducted to investigate the influence of different heating curves,different load holding ratios,different laminate composition.The results show that the initial carbonization rate of non-standard fire heating curve is very fast,and the fire resistance of the specimen exposed to the non-standard fire heating curve is smaller.Therefore,it is a hidden danger to directly apply the study on the fire resistance of CLT floor under the standard fire heating curve to the actual fire.The reduction of load holding ratio is one of the effective ways to increase the fire resistance of CTL floor.When the charring layer of CLT floor made of PUR adhesive is charring to the rubber layer,the charring layer may partially fall off,increasing the charring rate of the CLT.From the test results,it can be seen that the CLT floor made of the three floors did not fall off,while the CLT floor made of the five floors all fall off,and the falling time of the CLT floor of the five floors has a certain randomness.(4)With the finite element software ABAQUS as the platform,the sequential coupling analysis method of temperature field-structure field was adopted.The Model change function of ABAQUS was adopted to realize the impact of delamination on the temperature field.The validity of the finite element method is verified by comparing the experimental results with the finite element calculation results,which provides a scientific and effective method for the finite element calculation of complex models in the future.(5)Combined with foreign wood structure design codes,suggestions are proposed for the fire protection design of CLT members,and the calculation methods of the charring speed of CLT floor considering the delamination in non-standard fire is derived.Combined with the residual section method,the calculation method of the fire resistance of CLT floor exposed to non-standard fire is obtained.It provides reference for future engineering designers to carry out CLT floor fire resistance design.