Civil Engineering Reference
In-Depth Information
ultimate tensile strength of at least 450 N/mm
2
and an elongation of at
least 15%. The advantages of stud connectors are that the welding process
is rapid, they provide little obstruction to reinforcement in the concrete
slab, and they are equally strong and stiff in shear in all directions normal
to the axis of the stud.
There are two factors that influence the diameter of studs. One is the
welding process, which becomes increasingly difficult and expensive at
diameters exceeding 20 mm, and the other is the thickness,
t
(Fig. 2.6), of
the plate or flange to which the stud is welded. A study made in the USA
[23] found that the full static strength of the stud can be developed if
d
/
t
is less than about 2.7, and a limit of 2.5 is given in EN 1994-1-1. Tests
using repeated loading have led to the rule that where the flange plate is
subjected to fluctuating tensile stress,
d
/
t
may not exceed 1.5. These rules
prevent the use of welded studs as shear connection in composite slabs.
The maximum shear force that can be resisted by a 25-mm stud is
relatively low, about 130 kN. Other types of connector with higher strength
have been developed, primarily for use in bridges. These are bars with
hoops (Fig. 2.7(a)), tees with hoops, horseshoes and channels (Fig. 2.7(b)).
Figure 2.7
Other types of shear connector
