structural behavior of reinforced concrete rectangular beame with different hight to with ratios

Abstract

ABSTRACT This research work studied the behavior of structural strength of reinforcement concrete rectangular beams with different hight to width ratio (h/b) with normal concrete strength (NCS), high strength concrete (HSC), and ultra-high strength (UHSC). Twelve reinforced concrete beams with the dimensions of (150*416.6) (200*312.5) (250*250) (312.5*200) mm were investigated. The variables studied in this work were the concrete compressive strength (27-62-90 MPa), the (h/b) ratio (from 0.36 to 0.64, 1 and 1.56) It is worth to mention that self-compacted concrete used to produce the normal strength concrete, the high strength concrete (HSC), and ultra-high strength (UHSC). The experimental results showed that, the increase in the (h/b) ratio (from 0.36 to 0.64, 1 and 1.56) is much increasing the cracking load, yielding load, ultimate load and the ductility index. The increase in the (h/b) ratio leads to curvature and concrete compressive strain. The increase in the compressive strength of the concrete with increase in the (h/b) reduces the high defamation that caused by the plastic deformation of the steel reinforcement. The increase in the compressive strength of the concrete with increase in the (h/b) causes (74% -122%), (66.67% -116.67%) and (57.14% - 128.6%), respectively increase in cracking load, increase yielding load in the ranges of ( (41.2%- II 70.6%), (30%-60%) and (76.3% - 96.6%), respectively, increase the ultimate load in the range of (41.67% to 115%), while reduce the ductility index in the range of (1.2% - 31.1%) as compared with control beams (BN1, BH1 and BU1). The variation of the concrete compressive strength with constant (h/b) shows conflict in the improvement of cracking load, yielding load, ultimate load and the ductility index. The maximum crack width decreases gradually with gradual increase in the (h/b) ratio (from 0.36 to 0.64, 1 and 1.56) for constant (27 MPa or 62 MPa or 90 MPa) compressive strength of concrete in the range of (11.11% - 25.9%), (5.3% and 21%) and (13.33% - 33.33%) respectively, as compared with control beams (BN1, BH1 and BU1). The gradual increase in the compressive strength of concrete from (27 MPa to 62 and 90 MPa) with constant (0.36 or 0.64 or 1 or 1.56) (h/b) ratio leads to increase the first crack load with range of (5.3%- 33.33%), increase yielding load in the range of (17.65% -70.8%), increase the ultimate load in the range of (4.35%-71.88%), while reduce the ductility index in the range of (1.16% and 18.8%) as compared with control beams (BN1, BH1 and BU1). The maximum crack width decreases gradually with gradual increase in the compressive strength of concrete from (27 MPa to 62 and 90 MPa) with constant (0.36 or 0.64 or 1 or 1.56) (h/b) ratios in the range of (25% - 50%) as compared with control beams (BN1, BH1 and BU1).