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Shear-critical reinforced concrete beams under sustained loading
Part II: Numerical study

R. Sarkhosh, J.C. Walraven, J.A. den Uijl

Delft University of Technology, Faculty of Civil Engineering and Geosciences, Group of Concrete Structures, the Netherlands

In part I of this paper, dedicated to the subject of shear resistance under sustained loading (Sarkhosh 2015), a series of tests on reinforced concrete beams without shear reinforcement was described, which were subjected to high sustained shear loads close to the short-term failure load. The goal of this research project was to investigate the behaviour of shear-critical concrete beams under sustained loading. The beams were subjected to the sustained load for periods ranging from three months to three years. Meanwhile, the deflection, crack growth and crack widths were measured. In part II of this paper, a numerical model is presented based on a modification of the inclined shear crack model of Gastebled & May (2001), in which the effect of time-dependent parameters on the shear resistance of the concrete beams is introduced. The model considers a bilinear inclined shear crack in the beam web that includes the effect of aggregate interlock according to the rough crack model of Walraven (1980) on the shear resistance of the beam. The validity of the modified model was verified for short term loading against 393 experiments on concrete beams. For long term loading it was verified against new tests (Part I of this paper). With this model it can be explained why the sustained loading effect in shear is much less significant than in tension and compression.