Although the strut and tie approach is a rational and reasonable approach for the design of non-flexural members in concrete structures, the approach may lead to suboptimal design, as much of the material present in the member is neglected. Other difficulties, such as the amount of time consumed and the designer dependency of the solutions, have been encountered in its implementation. To avoid these problems, design may be undertaken using conventional linear elastic finite element analysis, which can yield more efficient designs with less material usage. However, the conventional linear elastic finite element method is also inefficient when the non-flexural members contain stress singularities, such as occur in a deep beam with square or rectangular web openings. These stress singularities lead to singular stress fields which always violate the yield criterion. This thesis proposes a modified linear elastic finite element method which can successfully remove the stress singularities by adjusting the elastic modulus in certain regions. This new approach involves stress redistribution in terms of both compressive stress and tensile stress. Three different types of beams, namely shallow beams, deep beams and deep beams with rectangular openings are used to demonstrate its efficiency. Additionally, both the conventional strut-and-tie method and the conventional LEFEA method are performed for comparison. Results show that the modified linear finite element approach to design (MLEFEA) is efficient, as it can overcome some of the inefficiencies involved in both conventional the strut-and-tie design approach and the conventional linear elastic finite element design approach. Furthermore, to verify its safety, the performance of the designs resulting from the new method is assessed through non-linear finite element analysis using ABAQUS, where the results indicate that MLEFEA is safe and can be used as a design approach.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2012|