Question

For designing a composite beam with two symetrically placed point loads, a uniform distributed load, and a simple span, how do you calculate the number of required shear stud connectors and their location?

Answer 1

Composite beams are generally 'I' sections made of steel acting with a conrete deck slab which is attached to top flange of 'I' section by means of shear connectors.

For most of the composite beams, shear connectors with 19 mm diameter and 100-125 mm long welded studs are preferred.

According to BS EN 1994-1 and BS EN 5950-3,

According to practical cases, shear studs are recommended to position in favourable location for the deck with cetreal stiffner in trough since it is difficult to position centrally and for a simply supported beam with symmetric loading, there will changeover of position of stud at mid-span.

When a composite beam is subjected to uniformly distributed load along its span:-

The max. bending moment will be at mid span, it is necessary to check the moment of resistance at point and calculate the number of shear connectors required to transfer the load. These connectors should be distributed equally between mid span and supports of beam.

For beams subjected to point loads, moment of resistance at intermediate points are required to be checked.

According to Eurocode 4 (EN 1994)

Design resistance of shear stud connector is given by:

Minimum value among the following two equations

(or)

where, - Ultimate tensile strength of shear stud

d- diameter of shank of stud connector

   - Characteristic cylinder strength of concrete

   - secant elastic modulus of concrete

Degree of shear connection, = Rq/ Rc (or) Rs (Min. value among Rc and Rs)

Rq- Total shear force transferred by shear conncetors

Rc - Compressive force of concrete

Rs - Tensile force due to yielding of steel.