USEFUL DATA 



The table on page 63 for slabs continuous over supports and based on the specified 

 unit stresses shows that a Gj^inch slab reinforced with ^^ round bars, 7)^ inches on 

 centers, will carry 178 pounds per square foot. 



Concrete Ribbed Slabs— Clay Tile Fillers: Given a floor of 22'-^' span, non- 

 continuous. This floor is to carry a live load of 70 pounds per square foot, a wood 

 floor on cinder concrete fill and a plastered ceiling; the finish and plaster weighing 

 together 27 pounds per square foot, thus giving a total superimposed load of 97 pounds 

 per squartf'foot. Steel stress 16,000 pounds per square inch and concrete 650 pounds 

 per square inch. 



The table on page 67 for non-continuous slabs shows that a lO'+SJ^" slab with 

 1.15 square inches of steel in each rib will carry 106 pounds per square foot and a 

 12"-f-2" slab with 1.04 square inches of steel will carry 112 pounds per square foot. 

 If the 10" +23^" slab is selected the area of steel called for in the table may be reduced 

 in the ratio of actual total load per square foot to the total carrying capacity per 



square foot or, 



(97_j_g7\ 



This area may be secured by using V/i" rounds and 1^* rounds in alternate ribs 

 or 2-^/i" squares in each rib. If the 12"+2" slab is used the table area of 1.04 square 

 inches may be similarly reduced to 0.96 square inch and a XY^ round bar placed in 

 each rib. 



Concrete Ribbed Slabs — Steel or Wood Forms. Consider a floor slab of 2r-0' 

 span continuous on one end only. The floor is to carry a live load of 80 pounds per 

 square foot, a wood floor on cinder concrete fill weighing 18 pounds per square foot 

 and a ceiling of plaster on metal lath weighing 10 pounds per square foot, giving a 

 total superimposed load of 108 pounds per square foot. 



The table on page 74 gives for a 12" +3" slab reinforced with 1.30 square inches df 

 steel in each rib a carrying capacity of 122 pounds per square foot. As this is in excess 

 of the requirements the table area of steel may be reduced as in the previous example 

 and an area of 1.20 square inches used. This area is secured by using 2- J^' round bars 

 in each rib. 



Tee-Beams, — Continuous over supports. Determine size and reinforcement of 

 a beam in a floor construction assuming the span to be 22 feet, the superimposed load 

 200 pounds per square foot, the floor slab 4^" thick and the distance center to center 

 of beams as 7'-0". The beam is continuous over supports and the unit stresses employed 

 are to be as follows: /s, 16,000; /c, 650; and v, 120. Haunches are not to be used at the 

 ends of the beams. This represents the type of beam usually encountered in building 

 construction commonly referred to as a T-beam, but due to the continuity at supports 

 its capacity must necessarily be rated on the section of the web of the beam rather 

 than upon the T-section at center of span. 



From the data given the total load per square foot of floor, including the 

 weight of the slab, is found to be 256 pounds per square foot, or 1,792 pounds 

 per linear foot of beam. By referring to the table on page 98 it will be found that 

 a 10" X 26" beam reinforced with 4-1" round bars will carry, exclusive of the 

 weight of beam, 1,927 pounds, which from a practical standpoint fulfills the conditions 

 of the problem. 



59 



