Flexural capacity of singly reinforced beam with 150 MPa ultra high-strength concrete

414-426In this paper, we have studied the 150 MPa ultra-high-strength concrete (UHSC). RC beam is reinforced by SD400 and SD500 bars to evaluate on range of maximum tensile steel ratio which have reasonable ductility capacities and flexural behaviors of UHSC through the flexural test. The reinforced ultra-high-strength-concrete beam subjected to flexural moment behaves more brittleness than the reinforced moderate strength concrete beam with equal reinforcement ratio (ρ/ρb, ρb=balanced steel ratio). In this study, 10 singly reinforced rectangular beam specimens using 150 MPa concrete compressive strength are tested to evaluate on flexural behavior. The ductility capacity of UHSC flexural member without compression reinforcements significantly decrease. Displacement ductility index indicates about 1.3~2.56 on 150 MPa UHSC. To obtain the minimum ductility ratio with above 3.0 for double reinforced beam and above 2.0 for singly reinforced beam, limit strain shall be set so that the net tensile strain of outermost tensile steel may be above 0.006 in excess of 0.005 and the tensile steel ratio is required to be 0.55 ρb or less