Civil Engineering Reference
In-Depth Information
Figure 9.37 continued…
Whenever truss analogy is used in this way, the dimensioning of the reinforcement
should be checked against bending theory, and the shear stress in the diaphragm
calculated by bending theory should be kept to the threshold defi ned by the code of
practice.
The diaphragm may be prestressed using an alternative truss as shown in
Figure 9.37 (e) and (f). The prestress may be dimensioned to control the bending
stresses at the SLS (as described in Chapters 5 and 6). The effective cross section of
the prestressed diaphragm for calculation of the stresses should include widths of top
and bottom slab equal to one tenth of
b
in Figure 9.37 (e) either side of the diaphragm
web, although the prestress compression will spread at an angle of 35º into the top
and bottom slabs, beyond the effective section, Figure 9.37 (g). The inclined tendons
may be dimensioned to carry the ULS shear in the diaphragm, allowing a narrower
