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F192028 Pages:2

Briefly explain the use and design of ring beam in dome structure.

A circular slab is 6 m diameter and is simply supported at the edges. It is loaded
with a live load of 4 kN/m?. Design the reinforcement for the slab and sketch the
details. Assume M 20 concrete and Fe 415 steel.
PART C
Answer any two full questions, each carries20 marks.

Design and detail a circular tank with fixed base for a capacity of 6 lakh litres.
The depth of water is to be 5m including freeboard of 250mm. The tank is
supported on ground. Design using M20 concrete and 415 grade steel.
Differentiate between pre-tensioning and post-tensioning.

Determine the extreme fibre stresses developed at the mid span section of a
simply supported prestressed concrete beam of rectangular section 250 mm x 600
mm prestressed using high tensile steel of cross sectional area 1000 mm’ stressed
to 1500 N/mm”. The center of gravity of the steel is 150 mm above the soffit of
the beam. The superimposed load is 16kN/m . Span of the beam is 12 m .Draw
the stress diagram at mid span.

Explain the various losses of prestress.

A prestressed concrete beam 250mm wide and 350 mm deep is prestressed by 12
wires of 6mm diameter located at an eccentricity of 40 mm and carrying a initial
stress of 1500 N/mm?. The span of the beam is 8m. Calculate the percentage of

losses in wires if it is pretensioned Es =210 KPa and Ec = 35 Kpa, relaxation of

steel stress = 5% of the initial stress, total shrinkage strain is 200 x10°.
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