Reinforced Concrete Design

Reinforced Concrete Design CECor3 – Design and Construction Civil Engineering Department

Ultimate Strength Design •

Singly Reinforced Beam

1.

2.

3. •

What is the maximum moment at ultimate condition? Find the number of 16mm bars required if the design moment at ultimate load is 200 kN/m. If the beam carries an ultimate load of 50 kN at midspan, how many 16mm bars are required? Doubly Reinforced Beams

Problem No. 3

A simply supported beam is reinforced with 428mm at the bottom and 2-28mm at top of the beam. Steel covering to centroid of reinforcement is 70mm at the top and bottom of the beam. The beam has a total depth of 400mm and a width of 300mm. fc’ = 30 MPa, fy = 415 MPa. Balanced steel ratio, pb = 0.021. Assume that the steel yields in simplification. 1. 2.

3. •

Determine the depth of compression block. Determine the design strength using 0.90 as reduction factor. Determine the live load at the midspan in addition to a DL = 20kN/m including the weight of the beam if it has a span of 6m. T – Beams

Problem No. 4

Problem No. 1

Given a beam 300mm by 500mm with an effective cover of 75 mm and reinforced with 4-25mm dia. deformed bars at the bottom. Use fc’ = 21 MPa, fy = 345 MPa. 1. 2.

3.

Determine the depth of compression block. Determine the distance of the outer compression fiber from the neutral axis. Determine the ultimate moment capacity of the beam.

Problem No. 2

Beam Section is b = 300mm, h = 450mm. Effective depth is 380mm. Compressive strength of concrete fc’ = 30MPa, steel strength fy = 415 MPa. The beam is simply supported on a span of 5m. and carries the following loads. Superimposed dead load = 16 kN/m, live load = 14 kN/m.

A reinforced concrete T-beam is to be designed for tension reinforcement only. The beam width is 250mm and the effective depth is 400mm. The flange thickness is 100mm and its effective flange width is 900mm. The applied moment is 300 kN-m. The area of tension reinforcement required is : Use fc’ = MPa and fy = 414 MPa.

Problem No. 5

Calculate the required steel area tension steel area of a T-beam for a floor system for which bw = 300mm, d = 450mm and floor thickness t = 100mm, to carry a dead load moment of 68 kN-m (including its own weight) and a live load moment of 135 kN-m. The beam is on a simple span of 6m. with center to center spacing of 3m between adjacent beams. Use fy = 345 MPa and fc’ = 27.6 MPa.

Reinforced Concrete Design CECor3 – Design and Construction Civil Engineering Department

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Slab

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Columns

3. Minimum Number of Bars

Minimum number of longitudinal bars in compression members shall be four (4) for bars within a rectangular or circular tie. 4. Tie Reinforcements for compression members shall conform to the following. a. All non prestressed bars shall be enclosed by lateral ties at least 10mm diameter in size for longitudinal bars 32mm in diameter.

b. 12mm diameter in size for 36 diameter bars and bundled longitudinal bars.

Problem No. 6 slab.

1. 2. 3.

From the figure shows a cross section of a one way

Compute the minimum thickness of Slab S-1. Compute the minimum thickness of Slab S-2. Compute the minimum thickness of Slab S-3.

Problem No. 7

If the concrete section of a solid one-way slab shown in Problem No. 6 has a unit weight of 2000 kg/m³. the reinforcing steel used has a strength of fy = 400 MPa. Compute the thickness of S-1, S-2 and S-3. Problem No. 8

A one-way slab has a thickness of 175mm. it is reinforced with 12mm bars spaced at 140mm on centers. Assuming a steel covering of 26mm and using fc’ = 21 MPa and fy = 276 MPa, 1. 2. 3.

Compute the effective depth of the slab. Compute the steel ratio of the slab. Compute the ultimate moment capacity of the slab.

5. Spacing of ties

Vertical spacing of ties shall not exceed: a. b. c.

16 longitudinal bar diameter 48 tie bar Least dimension of the column

a. b. c.

40mm Diameter of vertical bars 4/3 x maximum size of coarse aggregate

6. Minimum clear cover of ties

Reinforced Concrete Design CECor3 – Design and Construction Civil Engineering Department

Problem No. 9

A reinforced concrete tied column carries a dead axial load of 600 kN and a live load axial load of 750 kN. Fc’ = 28 MPa, fy = 400 MPa. 1. 2.

3.

What is the final factored load? NSCP 2010 Using super position method, what gives the smallest dimension of the column section if the steel ratio is 2%? What gives the number of 20mm diameter bars?

Problem No. 10

A 450mm square column is to be constructed above the ground. The vertical reinforcement consists of 828mm bars. Maximum size of aggregates is 25mm. fc’ = 20.7 MPa, fy = 276.5 MPa. 1. 2. 3.

What is the spacing required for the ties? What is the cover required over the ties? What gives the ratio of the center to center reinforcement distance to the length of side of column?