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).
