You may define the profiled metal decking to span at any angle between 0° (parallel) and 90° (perpendicular) to the direction of span of the steel beam. You can also specify the attachment of the decking for parallel, perpendicular and angled conditions.

Where you specify that the direction of span of the profiled metal decking to that of the steel beam is ≥ 45°, then Tekla Structural Designer assumes it is not necessary to check the beam for lateral torsional buckling during construction stage.

Where you specify that the direction of span of the profiled metal decking to that of the steel beam is < 45°, then you are given the opportunity to check the steel beam for lateral torsional buckling at the construction stage.

Where you specify that the direction of span of the profiled metal decking and that of the steel beam are parallel, you again have the same opportunity to either check the steel beam for lateral torsional buckling at the construction stage, or to set it as continuously restrained.

Closed ends decking

Composite beam design using closed ends decking (incl. Sigmat) is permitted. Some key aspects of the design as distinct from that for open ended decking are:

Construction Stage:

• LTB - since closed ends decking, such as the Sigmat Sigdeck100, will have crushed ends and be discontinuous at the supporting beams (studs not welded through deck), the beam is considered as laterally unrestrained for perpendicular spanning deck by default (can be overridden by the user).

Composite Stage:

• Shear Connector Resistance - when using stud diameters larger than the maximum allowed for typical decking you will be prompted with an Engineering tip note stating "The diameter of the selected studs is larger than the diameter typical for standard decking."

• The calculation of the design shear resistance, P_Rd, of a headed stud in concrete includes two reduction factors:

  • k_mod is taken from NCCI PN001 to allow the reinforcement to be placed above the head of the stud - this is unchanged,

  • RF is a reduction factor to account for the influence of deck geometry - for closed end decking the user-defined factor values are used directly in calculations rather than the equations of BS EN 1994-1-1:2004.

    See: Stud connector strength (Composite beams: EC4 Eurocode)

Longitudinal Shear:

• BS EN 1994-1-1:2004 Figure 6.16 identifies a series of potential critical sections for considering longitudinal shear strength. However, only the critical section "a-a" in the Figure has been implemented in Tekla Structural Designer’s composite design, following the exclusion criteria of subsequent code clauses.

  • Given the different geometry of the Sigmat Sigdeck100 - and closed ends decking in general - it is not immediately clear if these code exclusion criteria would still apply. Hence - in the absence of further specific guidance - a note is included in the Longitudinal shear check design details stating: “Critical sections other than a-a from BS EN 1994-1-1 Figure 6.16 have not been checked”.

• Any potential contribution of longitudinal shear strength from the decking or studs is ignored, given the limited research evidence currently available for the design of closed end deckings.

Output:

It is worth noting the following:

• Graphics and Drawings - the decking continues to be drawn as continuous (open ended) with the accepted side effect of the studs potentially clashing with the decking ribs.

• Material List - there will be a small inaccuracy in terms of material quantities; for the decking due to its crushed ends and for the concrete due to the omission of the continuous full depth concrete along the length of supporting beam (for perpendicular case).