Study On Compression Perpendicular To The Grain Of Wood Member Reinforced With Steel Bar

The strength and elastic modulus of wood perpendicular to the grain is much weaker compared with those of wood parallel to the grain.Besides,as creep perpendicular to the grain is prominent,oversize deformation which does harm to the wood structure might be caused under long term load perpendicular to the grain.It is usually advised to avoid compression perpendicular to the grain of wood member when designing it.Still,there exists such condition as wood beam supporting area where compression perpendicular to the grain is unavoidable.In order to solve the problem of insufficient strength and stiffness of wood perpendicular to the grain,this paper uses the method of reinforcing wood member in the direction perpendicular to the grain with steel bar.The target of this paper is focused on the strength,stiffness and long term deformation perpendicular to the grain of wood member and steel bar reinforced wood member.54 wood specimens and reinforced wood specimens are tested on compression perpendicular to the grain.Their load-deformation curves are acquired.Since different countries have different standards to define bearing capacity,the differences of stiffness and load capacity got from these standards are compared.The improvements of stiffness and load capacity of reinforced members compared with unreinforced ones are calculated.The coefficients representing how much potential of the stiffness and load capacity of the steel bar is reached are calculated.This paper assume the wood material to be transversely isotropic elastic-perfect and the tested specimens are simulated through ABAQUS software.The simulation results matches well with the test results which verified the validity of the simulation.According to the FE simulation results,this paper elicited the equation calculating the stiffness of wood member based on the stress spreading model.Different sizes of wood member loaded perpendicular to the grain are set up,the stiffness of these members got from FE are compared with the stiffness calculated from the equation and they match quite well with each other.Different members reinforced with various area reinforcing ratio and steel bar length are set up.The equation to calculate the stiffness of reinforced members are fitted with the data from these reinforced members.Several groups of parameters are chosen to make parametric analysis.The influence of area reinforcing ratio,steel bar length,volume reinforcing ratio and the method of steel bar configuration are discussed and the proper method of reinforcing wood member perpendicular to the grain with steel bar is advised.Based on the Kelvin chain theory,the finite element analysis of wood member and steel bar reinforced wood member on long term deformation is discussed.The relative creep coefficient of various sizes of wood member are calculated.The influence of area reinforcing ratio,steel bar length,volume reinforcing ratio and the method of steel bar configuration on the creep are discussed.The redistribution of load between wood and steel bar under long term load is discussed.