Flexural capacity and ductility of lightweight concrete T-beams

摘要

The present study aims to estimate the flexural capacity and ductility of lightweight concrete T-beams prepared using the expanded bottom ash and dredged soil granules (LWAC-BS beams). Eight full-scale beams were prepared under the main parameters including the unit weight and compressive strength of concrete and amount of longitudinal tensile reinforcement. The moment capacities and displacement ductility ratios measured for the present specimens were compared with those compiled from normal-weight concrete (NWC) beams and lightweight concrete beams made using the expanded clay and fly ash granules (LWAC-CF beams) with respect to the longitudinal reinforcement index (omega(s)). The coefficients for the equivalent rectangular stress block to assess the ultimate moment capacity of LWAC beams were formulated from the actual stress-strain curve of the concrete. The test results showed that the effect of the type of artificially expanded lightweight granules on the normalized cracking and ultimate moment capacities of LWAC beams was insignificant, whereas LWAC-BS beams exhibited lower displacement ductility ratios than LWAC-CF beams at the same omega(s) value. The maximum amount of longitudinal tensile reinforcement specified in ACI 318-14 provision for preventing brittle failure of the beam needs to be lowered for LWAC beams. When determining the coefficients of the equivalent stress block for LWAC members, the concrete unit weight deserves consideration as a primary factor together with the compressive strength of the concrete.