Civil Engineering November 2020 Review Innovations Concrete 4

ANALYSIS/INVESTIGATION OF RECTANGULAR BEAMS PROBLEM for PRACTICE

Problem 1
Problem 4 Problem 6
A reinforced concrete beam is 250 mm wide with an
A reinforced concrete beam is 300 mm wide with an Given Beam Data:
effective depth of 400 mm. Use f’c= 21 MPa and fy = 275
effective depth of 525 mm to centroid of reinforcement. Beam width, bw = 300mm
MPa. The section is reinforced with 4 – ϕ25mm bars. U =
Use f’c= 21 MPa and fy = 415 MPa. The section is reinforced Concrete strength , fc’ = 24 MPa
1.2D + 1.6L.
with 3 – ϕ28mm bars single layer. Steel yield strength, fy = 415 MPa
1. Compute for the nominal flexural strength. Use 2010/2015 NSCP.
2. Calculate the design flexural strength of the section. 1. Which of the following gives the classification of the 1. Determine the flexural strength of the section in kN-m if
section. beam is reinforced with 4 – ϕ25mm bars placed in a
3. Calculate the safe service live load moment if the
service moment from total dead load is 96 kN-m. A. Tension- controlled single layer under an effective depth of 550mm.
B. In transition but still in compliance with the NSCP. 2. Determine the actual stress (MPa) in the extreme
4. If the beam is 5m long with a moment from total dead
C. In transition and not in compliance with the NSCP. reinforcements if beam is reinforced with 6 – ϕ25mm
load of 96 kN-m, find the maximum moving
D. Compression-controlled bars placed equally in two layers having an effective
concentrated service live load that can be supported
by the beam. 2. Determine the stress in the tension reinforcements at depth of 520mm to centroid of the total tension steel
failure. and 550mm to the centroid of outer layer
reinforcements.
Problem 2 3. Determine the value of strength reduction factor 𝜙 for
flexure in accordance with the 2010/2015 NSCP. 3. Determine the flexural strength of the section in kN-m if
A reinforced concrete beam is 300 mm wide with an beam is reinforced with 6 – ϕ25mm bars placed
effective depth of 400 mm. Use f’c= 21 MPa and fy = 415 4. What is the design flexural strength of the section kN-m. equally in two layers having an effective depth of
MPa. The section is reinforced with 5– ϕ28mm bars. 520mm to centroid of total tension reinforcement and
1. Determine the stress in the tension steel. 550mm to the centroid of outer layer reinforcements.
Problem 5
2. Determine the total tensile force in the steel at
Given Beam Data:
nominal strength.
Beam width, bw = 300mm Problem 7
3. Calculate the nominal flexural strength of the section. Tension steel bars = 8 – ϕ25mm equally-placed A 6 m concrete beam is simply supported at the ends.
in 2 layers The beam has a width b = 300 mm and a total depth h =
Effective depth to centroid 450 mm. It is reinforced with 4 - 25mm ø at the tension side
Problem 3 of entire reinforcement, d = 512.5 mm and 2 - 25mm ø at the compression side with 70 mm cover
A 4m reinforced concrete cantilever beam has a width of Effective depth to centroid to centroid of reinforcements. fc’ = 35 MPa, fy = 415 MPa.
300 mm and a total depth of 560mm with an effective depth of of outer layer reinforcement, dt = 537.5 mm To simplify the solution, ignore compression steel when
490 mm. It is reinforced with 5 - φ28mm tension bars. f’c = Concrete strength, fc’ = 42 MPa steel ratio ρ < ρmax. At ultimate condition, U = 1.2D + 1.6L.
30 MPa and fy = 415 MPa. In addition to live load and its Steel yield strength, fy = 415 MPa
own weight, the beam carries a 150-mm-thick concrete slab 1. Determine the depth of the rectangular stress block.
(casted monolithically with the beam) with a tributary 1. Determine the location of the neutral axis of the section.
width of 4 m. The unit weight of concrete is 24 kN/m3 Use 2. Determine the nominal flexural strength, Mn.
2. Determine the value of strength reduction factor 𝜙 for
2010/2015 NSCP. 3. Determine the total factored uniform load including
flexure in accordance with the 2010 NSCP.
1. Determine the net tensile strain in the extreme tension the beam’s weight, the beam could safely support.
3. Determine the design flexural strength of the section in
steel. kN-m. 4. If the beam spacing is 3m, determine the safe service
2. Determine the value of neutral axis to depth dt ratio. floor live load (kPa) if the beam already carries 24.7
kN/m total factored dead load.
3. Determine the value of strength reduction factor for
determining the design flexural strength.
4. Calculate the design moment capacity of the beam, in kN-
m.

5. Find the maximum uniform service live load acting over
the entire span that can be supported by the beam.
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