Simply-supported composite slabs and beams - Composite Structures of Steel and Concrete - page 83

Figure 3.16 Design methods for partial shear connection

Use of partial shear connection in design
The curve ABC in Fig. 3.16 shows a typical relationship between M Rd /
M pl,Rd and degree of shear connection

η , found by using the preceding

equations for assumed values of η . When N c is taken as zero, then

M Rd = M pl,a,Rd

where M pl,a,Rd is the resistance of the steel section alone.
The curve is not valid for very low degrees of shear connection, for
reasons explained in Section 3.6.2. Where it is valid, it is evident that a
substantial saving in the cost of shear connectors can be obtained (e.g., by
using 0.7) when the required bending resistance M Ed is only slightly

below M pl,Rd .
Where profiled sheeting is used, there is sometimes too little space in
the troughs for n f connectors to be provided within a shear span, and then
partial-connection design becomes essential.
Unfortunately, curve ABC in Fig. 3.16 cannot be represented by a simple
algebraic expression. In practice, it is therefore sometimes replaced (con-
servatively) by the line AC, given by

η =

N c = N c,f ( M Rd − M pl,a,Rd )/( M pl,Rd − M pl,a,Rd ) (3.67)

In design, M Rd is replaced by the known value M Ed , and M pl,Rd , M pl,a,Rd
and N c,f are easily calculated, so this equation gives directly the design
force N c , and hence the number of connectors required in each shear span:

n f N c / N c,f = N c / P Rd

n = (3.68)

where P Rd is the design resistance of one connector.
The design of shear connection is further discussed in Section 3.6.