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Atlas TubeAtlas TubeWhere you can use this: Atlas Tube HSS Connections Hub onlyStatus: Beta · Region: US · Design codes: AISC 360-22, AISC Design Guide 24 (2nd ed.)

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What this calculator does

Designs a plate welded longitudinally (in the plane of the chord axis) to a round HSS chord, in T, Y and Cross connections. Both LRFD and ASD. There was previously no calculator for this connection. Engineers either worked it by hand from Design Guide 24 Table 8-1, or reached for the transverse plate calculator, which covers a different set of limit states and does not account for the eccentricity. The hand calculation is the slow kind. The chord plastification equation carries the Qf chord-stress function, the end-distance rule quietly halves the capacity, and the Y-connection weld group needs Manual Table 8-4 with interpolation. Each step is easy to get wrong, and all of them have to be redone whenever the load, the load angle or the chord section changes.

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Inputting key properties

  1. Select the connection type: T, Y or Cross. A Cross connection has plates on both sides of the chord, handled together in one sheet.
  2. Select the round HSS chord section and grade.
  3. Enter the plate geometry and grade.
  4. Enter the fillet weld size.
  5. Enter the load angle (Y connections).
  6. Enter the plate demand and the concurrent chord stress, which feeds the Qf function.
On a Y connection it is the load that sits at an angle, not the plate. The plate is still welded longitudinally along the chord, so changing the load angle will not change the plate in the diagram. If you were expecting the geometry to rotate, it will not, and nothing is wrong.

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Reviewing the calculations

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Chord

The end-distance rule of Section K1.4 halves both the plastification and the punching shear capacity when the plate sits close to the end of the member. This is easy to miss by hand and it is applied automatically here.

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Plate

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Weld

The eccentric weld group runs on Y connections because the load component along the chord axis acts at an eccentricity to the weld. For the same reason, the axial, shear and flexural interaction check applies to Y connections only. T and Cross connections have no load component along the chord axis, so no interaction check is reported for them.

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Reading the results

Governing demand-to-capacity ratios per limit state, with the limits of applicability checked automatically rather than read off a table. Both plates of a Cross connection are reported.