2021 SP2: Steel column base plate design - enhanced scope for USA head code

Tekla Structural Designer
2021
Tekla Structural Designer

2021 SP2: Steel column base plate design - enhanced scope for USA head code

[TSD-9295] - The scope of Steel Column Base Plate Design checks is further enhanced in this release for the USA Head Code to cover a wider range of loading conditions. The base tension (uplift) condition is now checked for the following loading conditions and associated checks:
 
Applied Load New / Enhanced Checks
Negative vertical load (Uplift)

Base Plate:

  • Base plate bending strength.

Rods and Anchorage:

  • Rods (in tension)

  • Concrete breakout (in tension)

  • Concrete pull out (in tension)

Weld:

  • Weld tension strength

Negative vertical (uplift) + (major) shear load

Base Plate:

  • Base plate bending strength.

Rods and Anchorage:

  • Rods (in tension)

  • Concrete breakout (in tension)

  • Concrete pull out (in tension)

  • Rods (in tension + shear)

  • Concrete (in tension + shear)

Weld:

  • Weld tension strength

  • Weld strength with combined shear and tension

The picture below shows the extent of the new/ updated checks as they appear in the Base Plate connections design details dialog.
Below are briefly listed some notable aspects of the new and enhanced checks. For fuller details of the checks, please see the updated Help Topic Column base plate design to AISC 360.
  • Base Plate - Bending Strength - this is a new check performed under negative vertical load (i.e. axial tension / uplift either with or without shear), with the bending strength determined according to LRFD or ASD, as appropriate.

    • The plate bending model assumes a 45 degree dispersion, the particulars of this depending on the column section shape; either I section (W, M, S & HP shapes) or HSS and pipe section. For I sections the method places restrictions on the location of rods and a warning is issued where this is not complied with. An example of the new design check details is shown below.
  • Shear - The checks undertaken depend on the Horizontal Shear Transfer option selected from; Friction Alone; Shear on Rods Alone; Friction and Shear on Rods. Shear checks are not changed in this release, however you should ensure that the “Friction Alone” option is not used for uplift cases.

  • Rods and Anchorage - this group of checks is completely new for this release.

    • The checks are divided into the following five separate parts and, where combined with shear, consider the full (major) shear force:

      • Rods in tension

      • Concrete breakout (in tension)

      • Concrete pull out (in tension)

      • Rods (in tension + shear)

      • Concrete (in tension + shear)

    • The anchor rod strength checks are calculated in accordance with AISC 360 and AISC Design Guide 1 for both LRFD and ASD load combinations. The concrete strength checks are calculated in accordance with ACI 318. Since ACI 318 only takes account of LRFD requirements then these checks are not performed for ASD load combinations.

    • In the current release, no reinforcement is assumed in the concrete foundation

    • Rods in Tension - this check is performed whenever negative vertical load (i.e. axial tension / uplift) is present. An example of the new design check details is shown below.

      • Anchor rod tension strength is calculated using the provisions of AISC 360 Section J3.
    • Concrete Breakout (in Tension) - this check is performed whenever negative vertical load (i.e. axial tension / uplift) is present. An example of the new design check details is shown below.

      • This check is carried out in accordance with the provisions of ACI 318-08 and -11 Appendix D and Chapter 17 of ACI 318-14 and -19.
    • Concrete Pull Out (in Tension) - this check is performed whenever negative vertical load (i.e. axial tension / uplift) is present. An example of the new design check details is shown below.

      • This check is carried out in accordance with the provisions of ACI 318-08 and -11 Appendix D and Chapter 17 of ACI 318-14 and -19.
    • Rods (in Tension + Shear) - this check is only performed under negative vertical load (i.e. axial tension / uplift) with (major) shear, and also only when the shear transfer option selected is either Shear on Rods Alone or Friction and Shear on Rods. An example of the new design check details is shown below.

      • Anchor rod strength in combined shear and tension is calculated using the provisions of AISC 360 Section J3.7

      • As in the Shear Strength of Rods check, only 2 of the anchor rods are assumed to be resisting the shear and the nominal shear strength, Fnv is determined as noted above.
    • Concrete (in Tension + Shear) - this check is only performed under negative vertical load (i.e. axial tension / uplift) with (major) shear, and also only when the shear transfer option selected is either Shear on Rods Alone or Friction and Shear on Rods. An example of the new design check details is shown below.

      • This check is carried out in accordance with the provisions of ACI 318-08 and -11 Appendix D and Chapter 17 of ACI 318-14 and -19.
  • Welds - the weld strengths are calculated in accordance with AISC 360 for both LRFD and ASD load combinations. The welds are now checked for the following design conditions: shear; tension; combined shear and tension.

    • Weld Tension Strength - This check is performed whenever negative vertical load (i.e. axial tension / uplift) is present. An example of the new design check details is shown below.

      • Weld tension strength is calculated using the provisions of AISC 360 Section J2. The tension forces are derived as for the Base Plate Bending Strength check.
    • Weld Strength with Combined Shear and Tension - this check is only performed under negative vertical load (i.e. axial tension / uplift) with (major) shear. An example of the new design check details is shown below.

      • Weld tension strength is calculated using the provisions of AISC 360 Section J2. The tension forces are derived as for the Base Plate Bending Strength check.

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