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Note

center, feet, beam and fibre

NOTE. Due attention in selecting the beam must be given to lateral and vertical deflection as previously noted, or to a proper reduction of the specified fibre stress to allow for these considerations.

1. Given a 15-inch 60-lb. beam on a span, center to center of bearings, of 22 feet 6 inches. Required the safe load uniformly distributed at a fibre stress of per square inch.

Solve (a) , by the methods given above ; (b), by use of coefficient of strength given in table of Properties by the formula M = g.

2. Find from the table of Safe Loads the total load which a 6-inch 12.25-lb. beam will carry on an effective span of 15 feet, without exceeding the limits of deflection for plastered ceiling ; allowable fibre strain 16,000 lbs. per square inch.

What would be the safe load in the above problem if the allowable fibre strain were 10,000 lbs. per square inch? In the following problems, solve, (a) by use of tables of Safe Loads, and (b) by formula M = f , and use of table of Properties.

3. Find the greatest safe load in pounds uniformly distrib uted that will be sustained by a 10-inch 35-lb. I beam having a clear span of 10 feet 3 inches and an effective span of 11 feet 3 inches, the allowed stress in extreme fibre being 12,500.

4. The moment of the forces in foot-pounds acting on a beam of un determined size is 108,000. What size

of beam will be required if a stress of 16,000 pounds per square inch is allowed in extreme fibre ? 5. What load uniformly dis tributed will a 15-inch 42-lb. I beam support per linear foot, if the span, cen ter to center of bearings, is 10 feet 4 inches, and the allowed stress in ex treme fibre is 14,500 pounds per square inch? 6. What weight of wall will a 12-inch 31.5-lb. I beam 18 feet long be tween center of bearings carry, no transverse support for wall ? Allow able fibre strain, 16,000 lbs. per square inch.

7. An office building has columns spaced 15 feet on center in both direc tions. Give in detail the estimates of dead load for the following constructions. Live load in each case 100 lbs. per square foot.

(a) Beams spaced 5 feet center to center, 8-inch terra cotta arch of end construction, 2-inch wood screeds and cinder concrete filling, 4-inch under floor, and ,',-inch maple top floor.

(b) Same conditions, except 8-inch terra cotta arch of side construction.

(c) Same spacing of beams, with expanded-metaI. arch, type 8.

(d) Same conditions as above, but expanded-metal arch, type 3, with suspended ceiling.

(e) Beams spaced 7 feet 6 inches center to center. Columbian system, type 2, stone concrete.