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  3. a square wood platform 8 ft x 8 ft in...

Question: a square wood platform 8 ft x 8 ft in...

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A square wood platform, 8 ft x 8 ft in area, rests on masonry walls (see figure). The deck of the platform is constructed of 6 in x 2 in nominal dimensions tongue-and-groove planks (see appendix) supported on two 8- in. nominal dimensions (actual dimensions 3.5 in x 5.5 supported on a 6 in. masonry walls. The blanks are designed to support uniformly distributed load w (lb/ft3) acting over the entire top surface of the platform. The allowable bending stress for the planks and beams is 2400 psi and the allowable shear stress is 100 psi. When analysing the blanks disregard their own weight and assume that their reactions are uniformly distributed over the top surface of the supporting beams. Determine the allowable platform load w lb/ft) based upon the given allowable stresses (Hints: Use care in constructing the loading diagram for the planks, noting especially that the reactions are distributed loads instead of concentrated loads. Also, note that the maximum shear stress forces occur at the inside faces of the supporting beams.) 8 ft 8 ft 8

Scenario 1: Each girder of the lift bridge shown is 60m long and simply supported at the ends. The allowable bending stress for each girder is 200 MPa. The girders are fabricated by welding three steel plates to form an I-shape cross section as shown in the figure. Design the girder (i.e. determine the required dimensions) so as its bending stresses are equal or less than allowable stresses. Scenario 2: A beam ABC with overhang from B to C is constructed of a C 10 x 30 channel section made of A36 structural steel as shown in the figure. The beam supports its own weight (30 lb/ft) plus uniform load intensity q acting on the overhang. The factors of safety in tension and compression are 2.0 and 3, respectively. Determine the allowable uniform load qallowable if the distance L equals 3.0 ft. 3.033 in. ,2.384 in 0.649 in. 10.0 in.

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