Experimental study of shear strength in continuous reinforced concrete beams with and without shear reinforcement

Abstract

[EN] Shear strength of reinforced concrete beams has been extensively studied by many experimental campaigns conducted on simply supported beams. This situation has led to implement empirical design formulations in codes that cannot be representative of other real structures, such as continuous beams. These structures are characterised by the potential development of plastic hinges in areas of maximum shear and by the existence of an inflection point in the shear span. However, very few experimental studies on them have been conducted. In this paper, the shear strength of cantilever and continuous beams with different shear reinforcement ratios is analysed based on the test results of an experimental programme involving 15 beams.

Nine beams of 9.00 m and six of 7.00 m with rectangular cross-sections were tested under different load and support conditions, which gave rise to 30 different shear tests (two tests per beam). Three different series were considered according to the shear reinforcement ratio (0%, 0.13% and 0.20%). Apart from traditional instrumentation, such as strain gauges and displacement transducers, Digital Image Correlation was employed to provide accurate displacement measurements.

The results showed that the shear strength provided by concrete (different shear-transfer actions from shear reinforcement) decreased as bending rotation increased within both the elastic and plastic ranges of rotations developed in continuous beams. Moreover, this shear strength component was reduced for increasing shear reinforcement ratios. Shear slenderness was redefined for continuous beams that failed in shear after yielding of the tensile reinforcement and redistributing internal forces. The code formulation provided by ACI 318-19, Eurocode 2 and Model Code 2010 was checked against the experimental results, which showed that the iterative formulation that contemplates the M-V interaction considerably improved shear strength predictions from simple formulations.