Subject: Reinforced Concrete Structures Design &Drawing (RCSDD) Home work problems (July)

Note : Show solutions of these problems on or before 11-08-2015

Working Stress method:

Singly reinforced beam:

1. Design a reinforced concrete beam subjected to a bending moment of 20 kN-m . Use M15 concrete and mild steel reinforcement. Keep the width of the beam equal to half the effective depth. Draw the section neatly.

2. Redesign the above problem by using M20 concrete and Fe415 Steel?

3. A reinforced concrete beam 200 mm 400 mm effective depth is used over an effective span of 5m. It is subjected to a uniformly distributed load of 5 kN/m inclusive of its own weight. Find the necessary steel reinforcement at the center of the span. Take allowable stresses in steel and concrete as 130 MPa and 4MPa respectively, and m=16.

Doubly reinforced beam:

1. A doubly reinforced beam is 400 mm wide and 600 mm deep to the centre of tensile reinforcement. The compression reinforcement consists of 4 bars of 16 mm diameter, and is placed with its centre at a depth of 40 mm from the top. The section is subjected to a bending moment of 100 kN-m. Determine the stresses in concrete and steel. Take m=16.

2. A beam 250 mm X 500 mm in section is reinforced with 3 bars of 14 mm diameter at top and 5 bars of 20 mm diameter at the bottom, each at an effective cover of 40mm . Determine the moment of resistance of the beam section. Take permissible stresses in steel and concrete as 126 MPa and 5.2 MPa respectively , m=18.

Limit state Method:

1. A RC beam of rectangular section 250 mm wide and 600 mm deep is reinforced on tension side by 4 bars of 20 mm diameter. The beam is subjected to mild exposure conditions. The characteristic strengths of concrete and steel used are 25 N/mm2 and 415 N/mm2.

a) Calculate the ultimate moment of resistance of the section

b) Determine the maximum uniformly distributed load a simply supported beam of its section can carry over a span of 6m

2. A R.C beam has to resist an ultimate moment of 90 kN-m. design the section by considering width 'b'= 3 times effective depth 'd'. Use M20 concrete and Fe 415 steel. Draw the section neatly.

3. Determine the ultimate moment of resistance of the doubly reinforced beam section for the following data. Adopt M20 and Fe 415

Width of beam 'b'= 230 mm

Effective depth of the beam 'd'=370 mm

Area of Tension reinforcement (Ast) = 4 nos of 20 mm dia

Area of Compression reinforcement (Asc) = 3 nos of 12 mm dia

Effective cover = 30 mm