GATE Exam Questions - Engineering

Q1:

A prestressed concrete rectangular beam of size 300 mm x 900 mm is prestressed with an initial prestressing force of 700 kN at an eccentricity of 350 mm at midspan. Stress at top of the beam due to prestress alone, in N/mm2 is

A 46 (tension)

B 2.59 (compression)

C zero

D 8.64 (compression)

ANS:A - 46 (tension)

8.64 (Compression).

Top Stress= - (P/A) - (Pey/I).

=-(700, 000 N /(300mm * 900mm)) - ((700,000 N * 350mm * 450mm * 12)/(300mm * 900 mm ^3)).