Experimental Reasearch On Fire Resistance Of Laminated Veneer Bamboo Columns Under Eccentric Compression

Bamboo is a kind of natural and biodegradable composite material,with the characteristics of fast growth and environment friendly.Modern engineering bamboo materials represented by LVB(laminated veneer bamboo)are also increasingly favored by people.As the most important part of the bamboo structure system,column components are mainly faced with the following two important issues: First,in practical engineering applications,eccentricity or additional bending moments occur due to design or construction process deviations,accidental lateral loads,etc.The second is that bamboo is used as a green biomass material.In order to obtain a good appearance,it often does not take any fire prevention measures.In addition to the flammability of the material itself,it is also crucial to grasp the behavioral response and stress performance under fire conditions.Based on the above background,this paper conducts experimental research and theoretical derivation of normal-temperature and fire-resisting under eccentrically compressed glulam columns,and reveals the mechanical behavior and failure mechanism of eccentrically compressed glulam columns under room temperature and fire conditions,and derive the bearing capacity and the fire limit calculation method.First of all,in order to study the influence of eccentricity on the compressive performance of glulam,taking into account of five different eccentricities and two different cross-sectional dimensions.The test results show that under the action of different eccentricities,the final damage is caused by the lateral displacement of the bamboo columns under compression,which leads to the fracture of the fiber on the tension side,similar to the bending failure.During the entire deformation process,each section of the specimen is always kept flat,which conforms to the flat section assumption.The deformation curve of the specimen conforms to the quadratic function curve.Then,ABAQUS was used to simulate finite element analysis of each group of biased glulam bamboo column members.Based on the test results and the finite element method,the bearing capacity of the eccentrically pressed bamboo columns is theoretically analyzed and deduced.In the process of derivation,the tensile constitutive model of bonded bamboo was first given according to the wood property test.Based on this constitutive model,with reference to different modulus elasticity theory,the deflection curve equations were given when the glulam was subjected to eccentric compression failure.Then,using the flat section assumption,the equilibrium conditions of the force and moment were established,and the ultimate bearing capacity of the biased glulam was deduced.The comparison between the experimental values and the theoretical results shows that the two are in good agreement.Finally,a parametric analysis was carried out to give a simplified calculation formula for the ultimate bearing capacity.Secondly,in order to study the performance and mechanical properties of bamboo fires,four-sided fire tests were carried out on short columns of glued bamboo and long columns with eccentric compression.The results of the short column test show that the first two kinds of fire conditions have little effect on radial and tangential carbonization in 40 minutes.The eccentrically compressed gluing bamboo column fire test mainly considers the influence of eccentricity on its fire resistance.The results show that the eccentricity has a great influence on the fire resistance of the compressed glulam columns.When the specimens are near to failure,the deformation rate is large,and the failure is caused by the fibers on the tension side being broken and losing the bearing capacity.Based on the test results,heat transfer analysis and fire resistance performance analysis were performed using finite element software ABAQUS.Then,on the basis of the experimental results and the finite element method,two directions carbonization models were given.Afterwards,referring to the fire resistance design of wood structure in European Standard EC5,the cross-section method was used to simplify the calculation of the section,and the calculation model of the residual section bearing capacity of the gluing post-fired pillar was given.Finally,the above comprehensive analysis is given to calculate the fire limit of eccentrically compressed glulam columns.