Shear and Serviceability Reliability of Recycled Aggregate Concrete Beams

Shear resistance models and span-depth (l/d) provisions, existing in major standards for natural aggregate concrete (NAC) beams, may not be directly applied to recycled aggregate concrete (RAC) beams on account of higher randomness associated with the recycled coarse aggregates. Standards like ACI, CEB model code, Indian standard (IS), and Eurocode (EC) were considered for limit state of shear. Monte-Carlo technique was used to simulate random variables. Reliability analysis was performed considering variabilities of parameters which influence shear resistance of reinforced concrete beams. Shear model factors calculated from the database of RAC beams showed equivalent mean values but higher coefficient of variation than NAC. Code-specified resistance factors (as per ACI: 0.75) and partial material safety factor (0.8 as per CEB, IS and EC) are recalibrated for RAC to achieve NAC-equivalent safety. The modified shear resistance factors were obtained respectively as 0.72, 0.77, 0.65, and 0.6 for RAC beams. Reliability of RAC beams under both static and time-dependent loads were evaluated for limit state of deflection provisions of Indian and Australian standards. Lower l/d or higher depth is suggested for limiting total deflection of RAC beam elements. This reliability study is essential to ensure safe structural applications of RAC.