Handbook of Civil Engineering Calculations

0.40 in

2

(2.58 cm

2

). For negative reinforcement, supplement the two trussed bars over the

support with one straight no. 5 bar to obtain A 5 = 0.71 in^2 (4.58 cm^2 ).

To locate the bend points of the trussed bars and to investigate the bond stress, follow

the method given in Sec. 1.

DESIGN OFA STAIR SLAB

The concrete stair shown in elevation in Fig. 62<z, which has been proportioned in con-
formity with the requirements of the local building code, is to carry a live load of 100
lb/ft^2 (4.79 kPa). The slab will be poured independently of the supporting members. De-

(b) Determinotion of average

vertical depth

FIGURE 62. (a) Stairway slab; (b) determination of average vertical depth; (c) loads on stair-
way slab.

(c) Loads on stairway slab

Section of

zero shear

(a) Stairway slab

9 treads