| Due to the lack of wood and the accumulation of industrial and agricultural wastes in China,considering that magnesium oxychloride cement has the characteristics of light weight,high strength,low alkalinity and high affinity for plant fibers,scholars at home and abroad have conducted a lot of research on magnesium oxychloride cement filled with various plant fibers to make magnesium oxychloride cement composite materials,but the current research of composite materials has low strength,so it is limited to packaging materials and non-load-bearing materials.The imitation wood material studied in this paper is a new green material made of magnesium oxychloride cement as cementitious material,wood chips as filling material,and modifier,which has low tensile strength and slightly higher compressive strength.In order to promote the application range of imitation wood materials,this paper makes imitation wood materials into beam members in building structures,and in order to improve the bending performance of imitation wood beams,in vitro prestress is applied to them.In this paper,the bending bearing capacity of in vitro prestressed imitation wood beams is studied in detail,and the specific research contents and results are as follows:1.A new woody material prism specimen was made using a self-locking mold,and axial compression tests were conducted on the new woody material;The axial compressive strength,elastic modulus,and Poisson’s ratio of the new wood-like material were tested,and the axial compressive stress-strain curve of the new woodlike material was tested and fitted using a constitutive model.The results indicate that the failure process of the new wood-like material is divided into four stages and three failure modes,with high compressive strength and good deformation performance.2.Cut the old imitation wood material provided by Guizhou Science and Technology Environmental Protection New Material Research Co.,Ltd.into prism standard specimens for axial compression testing,observe its compression behavior,and measure its compressive strength and elastic modulus.The results indicate that the failure process of the old imitation wood material is similar to that of the new imitation wood material,and the compressive strength is lower than that of the new imitation wood material.3.Two simulated wood beams and six externally prestressed simulated wood beams were tested using reinforcement,tension control stress,and steering block height as experimental parameters.The experimental results show that the stress increment of prestressed reinforcement is related to the height of the turning block,and is not related to the tension control stress;The failure form of externally prestressed wooden beams is similar to that of sparsely reinforced beams;The bearing capacity of the external prestressed wooden beam has been improved under different parameter levels.4.Using the force method to derive the stress increment of prestressed tendons in externally prestressed wooden beams,equivalent load method and section stress analysis method to calculate the cracking load and deflection formulas.The results show that compared with the experimental values,the calculated values of stress increment are larger,the calculated values of cracking load have higher accuracy,and the calculated values of deflection are smaller.5.The stress increment,load-deflection,cracking load and span tension stress of in vitro prestressed imitation wood beams were calculated and analyzed by finite element software,and compared with the test results and theoretical analysis results,and the model was modified according to the test results. |
