This document discusses the flexural analysis and design of reinforced concrete beams. It provides an example of calculating the nominal flexural strength (ΦbMn) for a doubly reinforced concrete beam section under two cases with different concrete compressive strengths (fc'). It also provides a design example for a simply supported rectangular beam with given span, load, depth limitation, width, concrete strength, and steel yield strength. The design is to be done for two cases where steel ratio (ρ) is minimized and balanced steel ratio criteria is satisfied.
2. Plain & Reinforced Concrete-1
Example:
A doubly reinforced section has the following sectional
properties:
As’ = 570 mm2 As = 3042 mm2
d’ = 60 mm b = 300 mm
fy = 300 MPa
Calculate ΦbMn for the following two cases:
fc’ = 20 MPa d = 525 mm
fc’ = 35 MPa d = 225 mm
3. Plain & Reinforced Concrete-1
Example:
Design a simply supported rectangular beam having a span of
6m, subjected to a total factored load (including self weight) of
70 kN/m. The depth of beam is not to exceed span/12 and
width is 300m.
fc’ = 20 MPa, fy = 420 MPa
Design for following two cases:
• As’ is to be as small as possible
• . b
y
s
0.5ρ
f
'f
ρ'ρ
_
