Question

A beam ABC with an overhang from B to C is constructed of a C 10 x 30 channel section (see figure). The beam supports its own weight (30 lb/ft) plus a uniform load of intensity q acting on the overhang. The allowable stresses in tension and compression are 18 ksi and 12 ksi, respectively. Determine the allowable uniform load qallow (lb/ft) if the distance L equals 3.0 ft. The moment of inertia, I = 3.94 in4.

Answer 1

C 10 × 30 channel section 2.384 in. c 、 0.649 in 1 = 3.94 in,4 (from Table E-3) a0- weight of beam ABC 30 lb/ft 2.5 lb/in ALLOWABLE STRESSES MAXIMUM BENDING MOMENT Mmax occurs at support B. Mmax Tension on top; compression on bottom ALLOWABLE BENDING MOMENT BASED UPON TENSION o, l (18 ksi) (3.94m)-29,750 lb-in _ 2.384 in ALLOWABLE BENDING MOMENT BASED UPON COMPRESSION (12 ksi ) ( 3.94 in.*) 0.649 in Ơc I 72,850 lb-in ALLOWABLE BENDING MOMENT Tension governs. M ALLOWABLE UNIFORM LOAD q allow = 29,750 lb-in (q + o)L2 2Mallow allow 2(29,750 lb-in.) allowllow 40 2.5 lb/in (36 in.)2 43.41 lb/in. 45.91-2.5 a (43.41)(12) 521 lb/ft allow