Some useful civil engineering problems & their solutions on Doubly Reinforced Beam

Example 01: Determine the Number of 32-mm Steel Bars for Doubly-Reinforced Concrete Propped Beam.

Problem: There is a propped beam with length 8 m to withstand a total load of 28.8 kN/m. It is required to determine the steel reinforcement at the most vital section in bending.

The dimension of the cross section of the concrete beam is 400 mm x 600 mm containing an effective cover of 60 mm for the reinforcements. f’c = 21 MPa, fs = 140 MPa, n = 9. Find out the desired number of 32 mm ø tension bars and the number of 32 mm ø compression bars.

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Example 02: Stress of Tension Steel, Stress of Compression Steel, and Stress of Concrete in Doubly Reinforced Beam.

Problem: A reinforced concrete beam section with dimension 300 mm × 600 m is reinforced with 4 - 28-mm-diameter tension steel at d = 536 mm and 2 - 28-mm-diameter compression steel at d' = 64 mm. The section has to undergo a bending moment of 150 kN•m. Utilize n = 9.

1. Determine the maximum stress in concrete.
2. Work out the stress in the compression steel.
3. Work out the stress in the tension steel.

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Also Read: How to design a double reinforced concrete beam

Example 03: Design of Steel Reinforcement of Concrete Beams with WSD Method

Detail guidelines for determining the desired steel reinforcements of beam with known M_max and other beam properties with Working Stress Design method.

The calculation is done based on the following data :-

Width or breadth = b
Effective depth = d
Allowable stress for concrete = f_c
Allowable stress for steel = f_s
Modular ratio = n
Maximum moment carried by the beam = M_max

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