Refinement of plasticity based truss model for bending and torsion using database of experimental research and novel strain-based truss model

In this paper, a plasticity based space truss model developed to predict the ultimate strength of heavily reinforced and prestressed solid concrete members under combined bending and torsional loading is used to analyze 97 beams found in the literature in order to verify the model and extend it’s range of applicability. The results of the model are analyzed by studying the structural behavior of the chosen beams in more detail with another model that considers the effects of cross-sectional deformations on the strain state of the reinforcement and concrete and is able to generate accurate load-deformation relationships and ultimate resistances for the test specimens in the selected database. A complicated but stable solution algorithm is devised to solve the problem that require repeated iterative calculations in order to solve the equilibrium equations of the cross-section while also keeping the local deformations compatible with the global deformations. The novel strain based model is verified against the selected database and proves to be accurate tool for analysis as it can accurately predict the failure loads. By analysis of the calculation results it is found that by adjusting the shear panel thickness and the softening factor of concrete under shear of the plasticity based model, a better agreement between the model and the test results is achieved which encourages further development and extension of the models capabilities.