Experimental tests and analytical modeling of UHPC beams subjected to torsion

摘要

TwelveUHPCbeams with different combinations of steel fibers, longitudinal and transverse reinforcementrnwere investigated experimentally under pure torsion. Steel fibers having 17mm length and 0.15mmrndiameter with volumetric ratios of 0.5%and 0.9%were used. The average compressive strength of the referencernUHPC standard cylinderswas about 205MPa.The UHPC beams with steel fibers only showed a ductile behavior.rnIt was found that the addition of either longitudinal or transverse reinforcement to the steel-fiber UHPC beamsrnadded much to the ductility and very little to the ultimate capacity. The steel fibers having a volumetric ratiornof 0.9 % together with the longitudinal or transverse reinforcement accomplished an effective load carryingrnmechanism after cracking. Only the case of both longitudinal and transverse reinforcement in addition to steelrnfibers provided a very high increase both in ultimate torsion capacity and ductility. An analytical model basedrnon the well known ”thin-walled tube” analogy was developed. The comparison between the experimental andrnanalytical results shows very good agreement.