1. Design the gabled frame shown for a balanced snow load
shown in Figure P5–69 (typical of the Midwest) for an apartment building.
Select a wide flange section for the frame. Assume the allowable bending stress
not to exceed 140 MPa. Use ASTM A36 steel.
2.
Design a gantry crane that must be able to lift 10
tons as it must lift compressors, motors, heat exchangers, and controls. This
load should be placed at the center of one of the main 12-foot-long beams as
shown in Figure P5–70, by the hoisting device location. Note that this beam is
on one side of the crane. Assume you are using
ASTM A36 structural steel. The crane must be 12 feet long, 8
feet wide, and 15 feet high. The beams should all be the same size, the columns
all the same size, and the bracing all the same size. The corner bracing can be
wide flange sections or some other common shape. You must verify that the
structure is safe by checking the beam’s bending strength and allowable
deflection, the column’s buckling strength, and the bracing’s buckling
strength. Use a factor of safety against material yielding of the beams of 5.
Verify that the beam deflection is less than L/360, where L is the span of the
beam. Check Euler buckling of the long columns and the bracing. Use a factor of
safety against buckling of 5. Assume the column-to-beam joints to be rigid
while the bracing (a total of eight braces) is pinned to the column and beam at
each of the four corners. Also assume the gantry crane is on rollers with one
roller locked down to behave as a pin support as shown.
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