Continuous beams and slabs, and beams in frames - Composite Structures of Steel and Concrete - page 157

4.6 Example: continuous composite beam

4.6.1 Data

So that use can be made of previous work, the design problem is identical
with that of Chapter 3, except that the building (Fig. 3.1) now consists of
two bays each of span 9.5 m. The transverse beams at 4 m centres are
assumed to be continuous over a central longitudinal wall. They are attached
to columns in the outer walls, as before, by nominally-pinned joints located
0.2 m from the centres of the columns. No account is taken of the width
of the central wall. Thus, each beam is as shown in Fig. 4.11.
The use of continuity should offset the increase in span from 9 m to
9.5 m, so it is assumed initially that the designs of the slab and the mid-
span region of the beam are as before, with the same materials, loads, and
partial safety factors. The design loads per unit length of beam, repres-
ented by the general symbol w , and the corresponding values of the bend-
ing moment wL 2 /8 for a span of 9.3 m are as given in Table 4.4.

Table 4.4 Loads and bending moments for a span of 9.3 m

Characteristic loads Ultimate loads

Load wL 2 /8 Load wL 2 /8

(kN/m) (kN m) (kN/m) (kN m)

Permanent, on steel beam 12.4 134 16.7 181

Permanent, composite 5.2 56 7.0 76

Variable, composite 24.8 268 37.2 402

Total 42.4 458 60.9 659

Figure 4.11 Continuous beam with dead load, plus imposed load
on span AB only