Weld Calculations Made Simple: Checking HSS Welds Using STI’s Effective Weld Length Calculator

By Brady Golinski, PE
FORSE Consulting, Technical Consultant to the Steel Tube Institute
July, 2025

Download PDF of Examples

The Steel Tube Institute offers a convenient online tool to assist in determining the effective weld lengths for elements connected to HSS members. The effective weld length can then be multiplied by the weld size to quickly determine weld capacity. The tool is especially helpful for connection types where calculations can otherwise become complex and time-consuming. Let’s look at a few examples to demonstrate the Effective Weld Length Calculator capabilities. 

Connection Type 1: Transverse Plate to Rectangular HSS

  • HSS material: ASTM A500 Gr. C (Fy = 50 ksi, Fu = 62 ksi)
  • Column: HSS12x8x1/2
  • Plate Material: ASTM A572 (Fy = 50 ksi, Fu = 65 ksi)
  • Plate: PL 3/8 x 6 1/2 in
  • Plate is attached to narrow face of HSS
Figure 1.1: STI Effective Length Calculator Input Echo for Transverse Plate-to-HSS Connection
Figure 1.1: STI Effective Length Calculator Input Echo for Transverse Plate-to-HSS Connection

We will calculate the effective weld length for the transverse plate per AISC 360-22 Specification Chapter K, Table K5.1:

AISC 360-22 Spec Eq. (K1-1)

le = 2Be = 2 X 4.68 in = 9.37 in AISC 360-22 Spec Eq. (K5-4)

Compare these values with the output from the STI Effective Weld Length Calculator shown below:

Figure 1.2: STI Effective Length Calculator Program Output for Transverse Plate-to-HSS Connection
Figure 1.2: STI Effective Length Calculator Program Output for Transverse Plate-to-HSS Connection

Connection Type 2: Rectangular HSS-to-Rectangular HSS, Y-Connection, Under Branch Axial Load or Bending

  • HSS material: ASTM A500 Gr. C (Fy = 50 ksi, Fu = 62 ksi)
  • HSS chord shape: HSS12x8x1/2
  • HSS branch shape: HSS6x6x3/8
  • HSS branch angle: θ = 45°
  • Branch is attached to narrow face of chord
  • Check a 1/4″ weld throat thickness
Figure 2.1: STI Effective Length Calculator Input Echo for Rectangular HSS-to-HSS, Y-Connection
Figure 2.1: STI Effective Length Calculator Input Echo for Rectangular HSS-to-HSS, Y-Connection

Calculate the effective weld length and moments of inertia for the weld group per AISC 360-22 Specification Chapter K, Table K5.1, Equations (K5-5) through (K5-7):

AISC 360-22 Specification Chapter K, Table K5.1, Equations (K5-5) through (K5-7)

Again, these values can be compared to output from the STI Effective Weld Length Calculator:

Figure 2.2: STI Effective Length Calculator Program Output for Rectangular HSS-to-HSS, Y-Connection
Figure 2.2: STI Effective Length Calculator Program Output for Rectangular HSS-to-HSS, Y-Connection
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