Three-dimensional finite element modeling of time-dependent behavior of wood-concrete composite beams.

摘要

The wood-concrete composite beam structure with notched shear keys has some advantages such as high composite efficiency and ease of construction with low labor cost compared to other wood-concrete composite beam structures. Made up from two rheological materials, wood and concrete, the time-dependent behavior of the wood-concrete composite beam is not only affected by the long-term load but also driven by the variation of the environmental conditions such as temperature and relative humidity. To consider the effects of the environmental conditions, the modeling process must include the moisture diffusion analysis for the wood layer, the heat transfer analysis and the stress/displacement analysis where the first two analyses provide input parameters for the third analysis. This research focused on modeling the time-dependent behavior of the layered wood-concrete composite with notched shear keys by using 3D finite element method. The main goals of the research are to expand available constitutive models of wood and concrete so that they can be used in the 3D FEM. The 3D constitutive models of wood and concrete were then implemented in the commercial software ABAQUS by using the subroutine UMAT for the stress/displacement analysis. To provide data to validate the theoretical model, a long-term creep test on two specimens has been performed. The results of the verification analysis on one test specimen captured closely the time-dependent behavior of the test specimen for the first 123 days of the test. The verification analysis revealed that the heat transfer analysis is not necessary in long-term analysis. The application of the 3D model with solid elements not only predicts the long-term behavior of the wood-concrete composite beam structures better than ID models do, but it can be also applied for wood-concrete composite structures with complex geometry where the 1D model cannot be applied. In addition, the application of the 3D model with solid element can be used to perform parametric studies to address remaining questions about time-dependent of the wood-concrete composites structures.