Verification of details of existing structures with the elastic-plastic stress field method

摘要

The verification of critical details of existing structures is generally performed with strut-and-tie models. An alternative widely used in some countries, such as Switzerland or Denmark, is the rigid-plastic stress fields (RPSF) method (based on the lower bound theorem of plasticity) which allows for the consistent and systematic analysis of a variety of structural elements and details. It however requires a certain level of experience to be applied to a wider range of cases and in order to consider the various load-carrying actions. Therefore, the verification of existing structures requires a more systematic method. The elastic-plastic stress field method (FPSF) was developed at EPFL in order to overcome the limitations of the rigid-plastic stress field method. It takes into account the resistance of the concrete as a function of the deformations and has proven to give good estimates of the strength of reinforced concrete members. In the framework of this project it is intended to study the applicability of the EPSF and the RPSF for the assessment of certain complicated details specific for concrete bridges. In order to do that, a large amount of performed tests available in the literature will be analysed with the two methods. Some of the details that are studied are zones of introduction of concentrated forces, cantilevers with dapped ends, diaphragms, and the extreme ends of beams with poor anchorage of the reinforcement which can simulate the behaviour of prefabricated beams. The results will then be used to develop guidelines for the choice of the coefficient accounting for the reduction of the compressive strength of the concrete due to transversal strains and the angle of the inclination of the compressive struts.