| Laminated bamboo lumber(LBL)is an important engineering bamboo and a new building material.LBL is a flammable building material,and the relevant research on the basic mechanical properties at high temperature is very lacking,which seriously hinders the development of LBL material structure.Based on the above background,this paper passed the compressive and tensile resistance tests of the standard specimens of LBL material in the three directions of smooth grain,horizontal grain radial and horizontal chord,and the bending and shear resistance tests in the two directions of smooth grain,horizontal grain radial and horizontal chord,and bending and shear resistance tests in the two directions of smooth grain radial chord,and 0 °C,20 °C,60 °C,100 °C,130 °C,175 °C,185 °C,200 °C)in different temperature(-60 °C,-40 °C,-20 °C,-200 °C,-40 °C,-20 °C,-20 °C,130 °C,175 °C,185 °C,200 °C).The comparative analysis came to the following conclusions:(1)At different temperatures,the compressive performance of 186 specimens in 31 groups in three texture directions of LBL material was studied.The typical failure mode of LBL material compression specimens under different groups is different,and the failure form is basically divided into two types.On the whole,the compressive strength of LBL material decreases with the increase of temperature,and based on the experimental results,the mathematical relationship between the reduction coefficient of compressive strength of LBL material and the temperature and the constitutive model of LBL material at different temperatures are proposed.(2)The tensile properties of 33 groups of 284 specimens in three texture directions of LBL material were explored at different temperatures.The typical failure modes of LBL material tensile specimens are mainly divided into two types.On the whole,the tensile strength of LBL material decreases with increasing temperature.The change law of mechanical properties such as tensile strength of LBL material under the influence of different temperatures was fitted,and the mathematical relationship between the corresponding strength reduction coefficient and temperature was obtained,and the constitutive model of LBL material tensile resistance at different temperatures was fitted.(3)At different temperatures,the bending resistance of 132 specimens in 22 groups of LBL materials in the radial and chordal directions was tested.The typical failure modes of LBL bending specimens are mainly divided into two types,namely,the failure gap of the specimen is torn along the grain and the glued surface is damaged.The load-displacement curves of LBL material at different temperatures are basically linear until failure,and the failure of the specimen shows obvious brittle characteristics.As the temperature continues to rise,the ultimate load and elastic modulus of the specimen show a downward trend.The test values of flexural strength and elastic modulus reduction coefficient of LBL material at different temperatures were proposed.(4)At different temperatures,the shear resistance of 132 specimens in 22 groups of LBL materials in the radial and chordal directions was tested.There is only one typical failure mode of LBL material shear resistant specimens,that is,pure shear failure.The shear strength changes of the shear specimens in the two force directions are relatively close.In the test temperature range,the shear strength of the chord and radial specimens of the composite material decreases with the increase of temperature.The shear reduction coefficient of LBL material specimens was fitted,and the expression of shear strength reduction coefficient of LBL material along the chord and radial directions was proposed. |
