Material database updates

The following updates are made to the Materials database for this new feature:

• Profiled Metal Decking:

  • A new property “Ends” is added to the Metal Profile form allowing user-specification of the type of ends for each decking type. Thus it is a general feature that can be extended to other decking types, either new or already existing in the database.

  • The new “Ends” dropdown has two possible values:

    • Open - is the default for newly created types and is applied to all existing metal decking types in the database prior to the addition of the Sigmat decks.

    • Closed - is applied only to the new Sigmat Sigdeck100 decking type for first release and is non-editable

      

  • The Sigmat Sigdeck100 range is added to the database, from data sourced from the datasheet available on the Sigmat website and also an additional datasheet provided by the manufacturer directly, with four gauges - 0.8 mm, 0.9 mm, 1.1 mm and 1.4 mm.

• Shear connectors:

  • Two new stud connector sizes have been added to the database: these are 19.0x150 mm and 22.0x150 mm.

Member data updates

The following updates are made to the Member properties for this new feature:

• Floor construction:

  • The Stud connector type option (that already existed for composite precast floor construction) is now included for a composite steel decking floor when the Ends type = Closed. For the first release of this feature there is only one type of shear connector “Stud” and one type of application “Shop welded” as shown in the picture below.

    

• Stud connector strength:

  • Stud diameter - the limits on the maximum allowable stud diameter for EC design have been relaxed for steel composite beams supporting closed ends decking with values above 19 mm sizes being allowed - with a note in design.

  • Stud strength - the design strength of the shear connectors in steel composite floor construction is generally reduced - via a reduction factor - to account for the influence of the deck geometry. The code of practice gives equations for this factor for standard decking. However for Sigmat decking - given its height and discontinuity over the supporting beams - it is not clear that the code equations apply. Hence - in the absence of other specific guidance - it is necessary to input user-defined reduction factor values when using closed ends decking.

    • To cater for this, for all steel composite beams a new "User defined stud reduction factors" control is added as shown in the picture below

      

    • This setting is automatically controlled by the supported decking type; enabled for Closed Ends decking and disabled for Open Ends decking. When enabled there are the following two mandatory entry boxes for the reduction factor values (range from 0+ to 1).

      • Stud reduction factor for parallel sheeting

      • Stud reduction factor for perpendicular sheeting

    • Additionally, the existing option to “Apply NCCI…” is disabled where studs are “Shop welded” for Closed Ends decking.

• Connector layout:

  • The use of closed ends decking results in discontinuous perpendicular layouts and a full depth concrete channel along the length of the supporting beam. Hence the positioning of the studs is no longer restricted by the decking ribs and the current layout options specific to deck rib direction - parallel, perpendicular or diagonal - do not directly apply.

  • Since the existing diagonal decking layout is the most flexible, closed ends decking uses auto and manual stud layout functionality similar to the diagonal case.

Steel composite beam design with closed ends

Composite beam design using closed ends decking (incl. Sigmat) is added in this release for the United Kingdom (Eurocode) Regional Code only. For all other Regional Codes the following note is issued in design details with a beyond scope status; “Decking is not compatible with currently selected Regional Code”. Some key aspects of the new design as distinct from that in previous releases 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 the user 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 the reduction factor discussed above accounting 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.

• 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 for this release 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:

  • There are no changes to drawings or reports for closed end decking in this release - 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).