Shear Resistance of Concrete Beams under Decade of Sustained Loading

Subjected to either tensile or compressive loads, concrete is susceptible to the effect of sustained loading. To address this, common practice in building guidelines typically involves applying a sustained loading factor ranging from 0.6 to 0.85. Given that the shear capacity of structural members without shear reinforcement is linked to the concrete strength, one might question whether there is a comparable sustained loading impact on shear. To address this inquiry, a total of 18 reinforced concrete beams without shear reinforcement were subjected to prolonged sustained loading, with a load intensity factor (ratio of applied sustained shear load to shortterm shear resistance) ranging from 0.88 to 0.98. Several beams endured the sustained loading test for an extended period, close to a decade, before the test was terminated. Interestingly, in contrast to concrete subjected to direct compression or tension, it was observed that sustained loading did not affect the shear capacity. Some early results of this experimental study, where concrete beams were subjected to up to 4 years of sustained loading, have been previously published by Sarkhosh and Sarkhosh et al. This paper concludes the results of the testing campaign of up to a decade of sustained loading, with additional results and findings.