Strength of composite beams with shear connectors - I3.2 (Composite beams: AISC 360)
Section classification
For section classification purposes the true section is used. Tekla Structural Designer classifies the section in accordance with Section I3.2a. Only the web of the section is classified - the bottom flange is in tension and so cannot buckle locally and it is assumed that the top flange is sufficiently braced by the composite slab.
The classification of the web must be compact so that plastic stress blocks can be used.
Flexure
Checks are performed at the point of maximum moment and the position of application of each point load as well as all other points of interest along the beam. Flexure is calculated in accordance with Section I3.2. Since the flexural strength at all point loads is checked then this will inherently satisfy Section I3.2d (6) (360-05) or Section I8.2c (360-10, 360-16 and 360-22). Since the flexural strength at all point loads is checked then this will inherently satisfy Section I3.2d (6) (360-05) or Section I8.2c (360-10) which require that “the number of shear connectors placed between any concentrated load and the nearest point of zero moment shall be sufficient to develop the maximum required flexural strength at the concentrated load point”.
During the selection process, in auto design mode point loads are taken to be “significant” if they provide more than 10% of the total shear on the beam. For the final configuration and for check mode all point loads are checked for flexure.