Study on wooden constitutive model considering long-term effects of environment and loads

Given that the deformation of the timber is susceptible to the change of ambient temperature and the humidity, a timber constitutive model that can accurately describe the interaction with load and long-term ambient environment was proposed. Firstly, based on the Tsai-Wu yield criterion, the Drucker postulation and the consistency rule, a timber constitute model considering the normal creep and the mechanical absorption creep was proposed. Then, the deduced constitutive model was compiled into the UMAT subroutine and was embedded in the ABAQUS software by using the Fortran language, which realized the simulation analysis of the timber characteristics under the combined action of load and ambient environment. Finally, uniaxial material tests and mechanical absorption creep tests were conducted on old timber to verify the validity of the proposed constitutive model. Besides, the Hankinson theorem formula was also employed to verify the validity of the constitutive model when the timber was under the stress in perpendicular-to-wood-grain direction. The results show that the errors of the prediction of the yield stress when the timber is subjected to longitudinal, radial and chordwise compressions are 19. 5%, 4. 6% and 8.7%, respectively, which indicates that the deduced constitutive model and the user subroutine (UMAT) are effective to simulate mechanical properties of timber under the uniaxial and the perpendicular-to-wood-grain direction loading. Moreover, the results from the mechanical absorption creep experiments are in good agreement with the simulation results, which means that the deduced constitutive model can better predict the timber mechanical behavior under the combined action of load and ambient environment. © 2021, Editorial Office of Journal of Building Structures. All right reserved.