Structural Concrete - Hassoun

18.2 Types of Stairs 703
Figure 18.7
Steps projecting from one or two sides of the supporting wall.
iii. Total flight height h:Ifh is increased from 10 to 16 ft, the shearing force at the top edge
increases by about 150%. Moments increase by about 50 to 100%.
iv. Flight slab thickness t: This parameter has the least effect on forces and moments. For
example, if t is increased from 6 to 10 in., the moments increase by about 25% and the
shearing force by about 20%.
v. For practical design, the parameters may be chosen as follows: flight width between 4
and 6 ft, horizontal span L between 9 and 12 ft, total flight height between 10 and 15 ft,
and slab thickness between 6 and 10 in.
The preceding information is a guide to help the designer to choose the right parameters
for an economical design.
7. Run-riser stairs: Run-riser stairs are stepped underside stairs that consist of a number of runs
and risers rigidly connected without the provision of the normal waist slab (Fig. 18.14a). This
type of stairs has an elegant appearance and is sometimes favored by architects. The structural
analysis of run-riser stairs can be simplified by assuming that the effect of axial forces is
negligible and that the load on each run is concentrated at the end of the run (Fig. 18.14b).