CELE Past Board Exam Problem
Situation 24: To construct the deck of a bridge over a deep ravine, steel beams placed at S = 2.1 m on centers and simply supported on a span of L = 20 m are used to support the construction loads which include temporary formwork and construction loads equivalent to 4200 Pa. At this stage, only the steel beams carry the dead loads. After the slab has hardened, sufficient shear connectors welded to the beam flange provide full composite action of the steel beam with t = 0.15 m thick cast in placed concrete slab.
Given: Concrete fc’ = 20.7 MPa,
Concrete unit weight = 24 kN/m3
Steel Fy = 345 MPa
Modular ratio n = 9
For composite action, use b = 1800 mm effective flange width.
Section W 685mm x 152 kg/m
A = 19355 mm2 tf = 21 mm
d = 688 mm Ix = 15 x 108 mm4
tw = 13 mm Iy = 0.58 x 108 mm4
bf = 250 mm
1. Determine the maximum bending stress (MPa) in the beam due to dead load which include beam weight, slab and wearing surface of 600 Pa and construction loads.
2. Determine the maximum stress (MPa) in the beam if a standard truck load (H load) consisting of PS = 17.8 kN front wheel load and PL = 71.2 kN rear wheel load. Distance between loads is dw = 4.27 m. Include 20% impact live load.
3. Determine the total stress (MPa) of steel after concrete hardens.


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