Conference paper

Static and fatigue strength of RC slabs under concentrated loads near linear supports

RC slabs without shear reinforcement subjected to c oncentrated loads near lin ear supports are typical cases of deck slabs of bridges, transfer slabs or pile caps. Such elements are often designed or as­ sessed in shear with code provisions calibrated on the basis of tests on one-way slabs or beams with rectangular cross section, even t hough these tests are not representative of the actual behavior of two­ way slabs (non-parallel direction of shear forces and potential shear redistributions). Also the pres­ ence of prestressing ducts and slab inserts may infl uence the shear strength. In addition, the concen­ trated loads of the deck slabs are applied a number of cycles during the service life of the structure and may potentially lead to fatigue problems. In this investigation, two experi mental campaigns are presented. The first one consists of 12 static tests on 6 full-scale slabs subjected to a concentrat ed load with a central line support that allows evaluating the linear reaction. Parameters such as the location of the concentrated loads (3 locations) and presence of ducts (4 types) were varied. Th e second campaign has a sim ilar test setup and con­ sists of 4 static tests on 2 full-scale slabs (reference tests, failure load Q static ) and fatigue testing on 8 other slabs, varying the maximum applied load and the load location (2 locations). So far two slabs failed in shear ( Q max =90% and 80% Q static ) and two others due to bar fracture (fatigue in bending, Q max =70% and 60% Q static ) that ultimately led to shear failures. All slabs that statically failed in shear showed significant shear redist ributions prior to failure. This research aims to study the observed phenome na within the framework of the Critical Shear Crack Theory (CSCT) and to provide more data to the poor existing datasets . Comparisons with the fib- Model Code 2010 are presented. The ultimate goals of the research are to reduce the number of existing structures that need to be strengthened and to provide consistent design methods for new structures and assessment of existing ones.

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