Title:
SHEAR RESISTANCE OF CONCRETE MEMBERS WITHOUT SHEAR REINFORCEMENT UNDER SUSTAINED LOADING
Author(s):
Joost Walraven, Reza Sarkhosh
Publication:
Symposium Paper
Volume:
328
Issue:
Appears on pages(s):
14.1-14.18
Keywords:
experiments, reinforced concrete, shear, sustained loading
DOI:
10.14359/51711158
Date:
9/12/2018
Abstract:
Concrete loaded in tension and compression is prone to the effect of sustained loading. In order to deal with that, building recommendations generally use a sustained loading factor in the range 0.7-0.8. Because the shear capacity of members without shear reinforcement is a function of the concrete strength, it may be wondered whether there is also a sustained loading effect in shear. To answer this question 42 reinforced beams without shear reinforcement have been tested. Amongst them, 28 beams were loaded to failure in about 5 minutes for getting short term reference values for the subsequent sustained loading tests. The other 14 beams were subjected to long-term sustained loading, with a ratio between the applied shear load and the short-term shear resistance between 0,86 and 0,98. In the case that no shear failure occurred during the period of sustained loading, which ranged from three months to three years, the beams where loaded to failure. It was shown that, contrary to concrete loaded in direct compression or tension, the shear capacity is not influenced by a sustained loading effect. On the basis of physical modelling of the beam behaviour it could be demonstrated that the contribution of aggregate interlock in the lower part of the curved bending-shear cracks counteracts crack propagation at the top, so that the development of the crack pattern is arrested.
Related References:
1. fib Model Code for concrete Structures (2010), Ernst & Sohn, 2013
2. Gastebled, O.J., May, I.M. (2001), “Fracture Mechanics Model Applied to Shear Failure of Reinforced Concrete Beams without Stirrups”, ACI Structural Journal, Vol. 98, Issue 2, pp. 184-190
3. Sarkhosh, R. (2014) “Shear resistance of reinforced concrete beams without shear reinforcement under sustained loading”, PhD thesis, Delft University of Technology “, The Netherlands
4. Sarkhosh, R., Walraven, J.C., Den Uijl. J.A. (2017), “Shear critical reinforced concrete beams” – Part I Experiments” and Part II: Numerical study, to be published in Heron, 2017
5. Walraven, J.C. (1978) “The influence of effective depth on the shear strength of beams without shear reinforcement”, Stevin report 5-78-4, Delft University of Technology
6. Walraven, J.C. (1980) “Aggregate interlock: an experimental and theoretical analysis”, PhD Thesis, Delft University of Technology
7. Yang, Y. (2014), “Shear behaviour of reinforced concrete members without shear reinforcement: a new look at an old problem”, PhD thesis Delft University of Technology, The Netherlands
8. Zhou, F.P., Hillerborg, A. (1992), “Time dependant fracture of concrete: testing and modelling”, in Bazant, Z.P. (ed), “Fracture Mechanics of Reinforced Concrete Structures”, Elsevier Applied Science, The Netherlands, pp. 906-911.