Experimental Research On Properties Of Laminated Bamboo At High Temperature

Bamboo is a rapidly renewable sustainable material that is globally available and productive.Laminated bamboo made of raw bamboo has excellent processing performance and mechanical properties.Laminated bamboo is becoming an increasingly attractive structural material in construction engineering.However,bamboo scrimber is a combustible material similar to timber.The shortcoming in understanding of fire behavior of laminated bamboo may become a barrier for modern structural design.Therefore,in order to promote the engineering application of laminated bamboo,the fundamental performances of laminated bamboo material in elevated temperature are studied in this paper.The main contents and results can be concluded as follows.(1)Thermal physical performance tests are carried out.The specific heat capacity of laminated bamboo material from 20? to 400? was measured by TGA-DSC.The thermal conductivity and diffusivity at high temperatures of laminated bamboo were measured by HotDisk.(2)Studies on uniaxial compression,tension and shear of the laminated bamboo at three material axes are carried out respectively under normal temperature and high temperatures using electronic universal testing machine.The stress-strain curves and failure modes of each stress state under various temperature conditions are obtained.The correlations between the main mechanical properties(including elastic modulus,ultimate strength,ultimate strain etc.)and the target temperature are investigated.(3)According to the requirements of ISO 834,four groups of 20 laminated bamboo panels exposed to one-side fire are tested to study the charring performance of laminated bamboo.The results show that the charring rate is influenced by the exposure time and the ring orientation.As the temperature increases,the charring rate of laminated bamboo exposed to one-side fire decreases.The charring rate perpendicular to grain(radial direction)is normally larger than that perpendicular to grain(tangential direction),and the ratio is between 1.5?1.6.The model describing the rate of char development is proposed,which is a function of exposure time and the ring orientation.(4)According to the requirements of ISO 834,six groups of 6 laminated bamboo beams exposed to three-side fire and 6 laminated bamboo beams exposed to four-side fire are tested to study the charring performance of laminated bamboo.The results show that under three/four-side fire exposure,the corner of the rectangular section becomes circular arc due to the bi-directional heat transfer.The charring depth(charring rate)of the non-conor area is basically the same as that of the one-side fire exposure,and the charring depth(charring rate)of the conor area is significantly larger.Modifying the one-dimensional charring model,the charring model under multi-side fire is obtained.By considering the comer roundings,the equivalent cross-section of the multi-faceted fire is rectangular,and the notional charring model is given.(5)Laminated bamboo exposed to one-side fire and multi-side fire are simulated to achieve the temperature distribution for different exposure time using ABAQUS software.The results show the temperature of 270? can be defined as a criterion for the base of the char layer of laminated bamboo.When the effective remaining cross-sections of laminated bamboo exposed to multi-side fire are calculated,the thickness of pyrolysis layer are proposed to be 13.1 mm in radial direction perpendicular to grain and 19.7 mm in tangential direction perpendicular to grain,respectively.