Groove Weld Design Guide — CJP and PJP Weld Capacity per AISC 360, AS 4100, EN 1993

This guide covers the design of complete joint penetration (CJP) and partial joint penetration (PJP) groove welds in structural steel connections. It is written as an educational reference, not as a design procedure. All real-world designs must be verified by a qualified structural engineer.

For general weld QA patterns (fillet weld checks, minimum sizes, documentation), see the Weld Design Checklist.

Before You Start

Collect these inputs before checking any groove weld:

• Base metal properties: Yield strength (Fy) and tensile strength (Fu) of both connected parts. For CJP welds matching the base metal, the weaker of the two parts governs. For PJP welds, the weld metal strength (typically from the electrode classification) and the base metal strength are both checked.
• Groove preparation type: Single-V, double-V, single-bevel, double-bevel, single-J, double-J, single-U, or square groove. The preparation determines the effective throat and the required joint geometry per AWS D1.1 prequalified details.
• CJP or PJP classification: Is the weld intended to develop the full base metal strength (CJP) or a reduced strength (PJP)? This is a design decision that affects cost, inspection, and procedure qualification.
• Loading direction: Tension or compression normal to the effective area, or shear parallel to the weld axis. CJP welds in tension normal to the effective area must match the base metal strength. PJP welds in tension are subject to higher strength reduction factors in some codes.
• Electrode / filler metal classification: For matching electrodes (same strength as base metal), the weld metal strength is not separately checked for CJP. For undermatching electrodes used with PJP, the electrode strength governs.
• Weld access and backing: Is a backing bar required? Can the root be backgouged and backwelded? Weld access holes may be needed for CJP beam flange-to-column flange welds when the beam web interferes with the weld.
• Inspection category: Per AWS D1.1, CJP welds in tension applications typically require volumetric NDT (ultrasonic or radiographic testing). PJP welds may require only visual and magnetic particle inspection depending on the application and governing specification.

Step-by-Step Design Process

Step 1 — Determine weld type (CJP vs PJP). Evaluate the demand: if the connection must develop the full tensile strength of the base metal, specify CJP. For shear, compression, stiffeners, and connections where demand is less than the base metal capacity, PJP may be adequate and more economical.

Step 2 — Determine effective throat. For CJP, the effective throat equals the thickness of the thinner part joined. For PJP, the effective throat is specified in the welding procedure and depends on the groove angle, root face, and root opening per the prequalified joint detail (AWS D1.1 Table 2.1).

Step 3 — Compute base metal capacity. For CJP welds in tension or compression normal to the weld axis, the design strength equals the base metal strength: phi Rn = phi x Fy x A_base (AISC 360 J2.1). For CJP in shear: phi Rn = phi x 0.6 x Fy x A_base. No separate weld metal check is required when matching electrodes are used.

Step 4 — Compute PJP weld metal capacity. For PJP welds, check the weld metal strength: phi Rn = phi x 0.6 x FEXX x A_effective (AISC 360 J2.4), where A_effective = effective throat x effective length. Also check the base metal adjacent to the weld for shear rupture.

Step 5 — Apply code-specific reduction factors. AISC 360: phi = 0.75 for weld metal, phi = 0.90 for base metal yielding. AS 4100: phi = 0.80 (SP), 0.60 (GP). EN 1993-1-8: gamma_M2 = 1.25 for welds. CSA S16: phi = 0.67 for weld metal. For PJP in tension normal to the axis, some codes reduce the base metal strength check.

Step 6 — Specify weld access holes and procedure requirements. For CJP beam flange-to-column flange welds, check that weld access holes meet AWS D1.1 geometry requirements. Verify that the WPS is qualified (PQR available) for the groove preparation, position, and thickness range. Specify NDT requirements per the governing code and project specification.

Problem Statement

Connection: CJP groove weld between a W21x62 beam flange (tf = 0.615 in, bf = 8.24 in) and a W14x90 column flange. A992 steel (Fy = 50 ksi, Fu = 65 ksi). Matching E70XX electrode (FEXX = 70 ksi).

Loading: Factored tension normal to the weld axis: Tu = 180 kips (from moment at the beam end, resolved to flange force). Factored shear from the beam web is transferred separately through a bolted shear tab.

Design task: Verify the CJP groove weld capacity for the flange force. Determine effective throat. Check base metal strength. If PJP were used, what penetration depth would be required?

Step 1 — Determine Weld Type (CJP vs PJP)

CJP groove weld: The weld deposit penetrates the full thickness of the joint. With matching electrodes, the connection develops the full strength of the base metal. No separate weld strength calculation is required for tension or compression normal to the effective area per AISC 360-22 J2.1. The design strength equals the base metal strength.

For CJP tension normal to weld axis (AISC 360-22 J2.1):
✓ phi Rn = phi x Fy x A_base
  phi = 0.90 (base metal yielding, AISC D2)
  A_base = bf x tf = 8.24 x 0.615 = 5.07 in^2
  phi Rn = 0.90 x 50 x 5.07 = 228 kips

  Utilization: Tu / phi Rn = 180 / 228 = 0.79  ✓ PASS

PJP groove weld: Only a portion of the joint thickness is welded. The effective throat is less than the base metal thickness. Strength depends on the groove depth and electrode classification. PJP welds in tension normal to the axis have a reduced capacity — the base metal at the root of the joint acts as a notch and creates a stress concentration.

For PJP tension normal to weld axis (AISC 360-22 J2.1a):
The base metal tension strength must be checked at the reduced section.
phi Rn_base = phi x Fy x A_net

If the PJP penetration is 60% of tf:
  E_throat = 0.60 x 0.615 = 0.369 in
  A_net = bf x (tf - E_throat) = 8.24 x (0.615 - 0.369) = 2.03 in^2
  phi Rn_base = 0.90 x 50 x 2.03 = 91.4 kips  ✗ FAIL (91.4 < 180)

If the PJP penetration is 85% of tf:
  E_throat = 0.85 x 0.615 = 0.523 in
  A_net = 8.24 x 0.092 = 0.758 in^2
  phi Rn_base = 0.90 x 50 x 0.758 = 34.1 kips  ✗ FAIL (net section governs)

For this demand, PJP with E70XX is NOT adequate at any penetration depth
under AISC 360 because the net base metal section always governs.
CJP is required for this flange tension connection.

Step 2 — Effective Throat Calculation

For CJP groove welds, the effective throat equals the thickness of the thinner part joined. No reduction is applied for groove angle because the full cross-section melts and fuses.

CJP effective throat (AISC 360-22 J2.1):
  E_throat = min(tf_beam, tf_column)
  = min(0.615, 0.710) = 0.615 in

  Effective area A_weld = E_throat x bf = 0.615 x 8.24 = 5.07 in^2

For PJP groove welds, the effective throat is the shortest distance
from the root to the weld face (AWS D1.1 Table 2.1):

Single-bevel PJP (45 degree groove, no root face, 0.615 in thick):
  S = bevel depth minus root face contribution
  E_throat = S for groove angles >= 45 degrees per AWS D1.1

  If S = 0.375 in (typical single-bevel for 5/8 in plate):
  E_throat = 0.375 in
  A_weld = 0.375 x 8.24 = 3.09 in^2

Step 3 — Weld Capacity per Code

AISC 360-22 Method

CJP groove welds with matching electrodes: the design strength equals the base metal strength in tension and compression. Shear strength on the effective area uses 0.6 x Fy. No separate weld metal check is required.

AISC 360-22 — CJP tension normal to axis (J2.1):
  phi Rn = phi x Fy x A_base
  phi = 0.90
  phi Rn = 0.90 x 50 x 5.07 = 228 kips

AISC 360-22 — CJP shear on effective area (J2.1):
  phi Rn = phi x 0.6 x Fy x A_base
  phi = 0.90
  phi Rn = 0.90 x 0.6 x 50 x 5.07 = 137 kips

AISC 360-22 — PJP tension normal (J2.1a):
  phi Rn = phi x 0.6 x FEXX x A_weld  (weld metal check)
  phi = 0.75
  phi Rn_weld = 0.75 x 0.6 x 70 x 3.09 = 97.3 kips

  AND check base metal at the root (reduced section):
  phi Rn_base = phi x Fy x (bf x (tf - E_throat))
  phi = 0.90
  phi Rn_base = 0.90 x 50 x (8.24 x (0.615 - 0.375))
             = 0.90 x 50 x 1.98 = 89.1 kips

  Governing: min(97.3, 89.1) = 89.1 kips (base metal at root)

Utilization for demand Tu = 180 kips:
  CJP: 180 / 228 = 0.79  ✓
  PJP: 180 / 89.1 = 2.02  ✗ FAIL

AS 4100-2020 Method

AS 4100 uses the concept of weld categories: SP (structural purpose, phi = 0.80) and GP (general purpose, phi = 0.60). For CJP butt welds in tension, the design capacity is based on the base metal strength.

AS 4100-2020 — CJP butt weld in tension (Cl. 9.7.2.7):
  Nt = phi x fy x Ag
  phi = 0.90 (base metal yielding)
  fy = 355 MPa (Grade 350, comparable to A992)
  Ag = 209 x 15.6 = 3,260 mm^2

  phi Nt = 0.90 x 355 x 3,260 = 1,042,000 N = 1,042 kN

AS 4100-2020 — PJP butt weld (SP category, Cl. 9.7.3):
  Vw = phi x 0.6 x fuw x tw x Lw
  phi = 0.80 (SP)
  fuw = 480 MPa (E48XX electrode)
  tw = 9.5 mm (PJP effective throat, ~0.375 in)
  Lw = 209 mm (flange width)

  Vw_per_weld = 0.80 x 0.6 x 480 x 9.5 = 2,189 N/mm = 2.19 kN/mm
  Total Vw = 2.19 x 209 = 457 kN

  AND check base metal at reduced section:
  phi Nt_base = 0.90 x 355 x (209 x (15.6 - 9.5))
              = 0.90 x 355 x (209 x 6.1)
              = 0.90 x 355 x 1,275 = 407 kN

  Governing: 407 kN (base metal at root)

Utilization for demand Tu = 180 kips = 801 kN:
  CJP: 801 / 1,042 = 0.77  ✓
  PJP: 801 / 407 = 1.97  ✗ FAIL

EN 1993-1-8 Method

EN 1993-1-8 distinguishes between full-penetration butt welds (treated as equivalent to the base metal) and partial-penetration butt welds (treated like deep fillet welds).

EN 1993-1-8 — Full penetration butt weld (Cl. 4.7.1):
  The design resistance equals the design resistance of the weaker
  of the parts connected. No separate weld check is needed.

  Nt,Rd = min(Npl,Rd_beam_flange, Npl,Rd_column_flange)
  = fy_beam x bf x tf / gamma_M0
  = 355 x (209 x 15.6) / 1.00
  = 355 x 3,260 / 1.00
  = 1,157,300 N = 1,157 kN

EN 1993-1-8 — Partial penetration butt weld (Cl. 4.7.2):
  Fw,Rd = fvw,d x a_eff x Lw
  fvw,d = fu / (sqrt(3) x beta_w x gamma_M2)

  For S355 + E42 electrode: fu = 470 MPa, beta_w = 0.90, gamma_M2 = 1.25
  fvw,d = 470 / (1.732 x 0.90 x 1.25) = 241 MPa

  For PJP throat a_eff = 9.5 mm:
  Fw,Rd = 241 x 9.5 x 209 = 478,656 N = 479 kN

  AND check base metal (reduced section):
  Nt,Rd_base = fy x A_net / gamma_M0
  = 355 x (209 x 6.1) / 1.00
  = 355 x 1,275 = 452 kN

  Governing: 452 kN

Utilization for demand 801 kN:
  CJP: 801 / 1,157 = 0.69  ✓
  PJP: 801 / 452 = 1.77  ✗ FAIL

CSA S16:24 Method

CSA S16 treats groove welds similarly to AISC 360, with matching electrode assumptions for CJP.

CSA S16:24 — CJP groove weld (Cl. 13.13.4):
  Tr = phi x Ag x Fy
  phi = 0.90
  Tr = 0.90 x 3,260 x 350 = 1,027 x 10^3 N = 1,027 kN

CSA S16:24 — PJP groove weld (Cl. 13.13.5):
  Vr = phi x 0.67 x Aw x Xu
  phi = 0.67
  Xu = 490 MPa (E49XX electrode)
  Aw = 9.5 x 209 = 1,986 mm^2

  Vr_weld = 0.67 x 0.67 x 1,986 x 490 = 436,690 N = 437 kN

  AND base metal check at root:
  Tr_base = 0.90 x (209 x 6.1) x 350 = 401 kN

  Governing: 401 kN

Utilization: 801 / 401 = 2.00  ✗ FAIL

Summary

For the W21x62 beam flange tension connection (Tu = 180 kips / 801 kN) with CJP groove welds, all four codes produce adequate designs with utilization ratios between 0.69 and 0.79. PJP groove welds are not adequate at any practical penetration depth because the net base metal section at the root governs.

Conclusion: CJP groove welds with E70XX / E48XX matching electrodes are required for this flange tension connection. PJP welds are not adequate because the net base metal section at the root of the joint always governs at practical penetration depths. For seismic moment frame connections (SMF), CJP is required by AISC 341 regardless of demand, and weld access holes must meet prequalified geometry.

Code Comparison

Common Pitfalls

1. Specifying CJP without confirming procedure qualification. CJP welds require a qualified WPS backed by a PQR for the specific groove preparation, position, thickness range, and electrode classification. Specifying CJP when the fabricator does not have a qualified procedure for the joint geometry can cause delays and non-conformance. Verify the WPS exists before finalizing the specification.

2. Assuming PJP can substitute for CJP in tension applications. PJP groove welds in tension normal to the effective area have significantly lower strength than CJP because the net base metal section at the root governs. A PJP with 60% penetration on a flange may only provide 40-50% of the base metal tensile capacity. For most moment connection flanges in tension, PJP is not adequate.

3. Neglecting weld access holes for CJP beam-to-column flange welds. When the beam web interferes with the flange weld, a weld access hole (rat hole) must be cut in the beam web per AWS D1.1 Cl. 5.17. The access hole must extend to the beam web centerline, have adequate length (min 1.5x tf or 1.5 in), and include a re-entrant radius. Undersized access holes prevent the welder from achieving proper fusion at the root.

4. Mismatching electrode and base metal strengths. For CJP welds, the filler metal must match or overmatch the base metal tensile strength per AWS D1.1 Table 3.1. Using E70XX with A992 (Fu = 65 ksi) is acceptable (70 > 65). Using E60XX (60 ksi) with A992 is not acceptable for CJP. For PJP, undermatching may be acceptable if the reduced capacity is accounted for in the design.

5. Ignoring backing bar requirements and removal. CJP groove welds in beam flanges typically require a backing bar at the bottom of the joint. In seismic moment frame connections per AISC 341, the backing bar must be removed after welding, the root pass must be backgouged to sound metal, and a reinforcing fillet weld must be applied. Leaving the backing bar in place creates a crack initiation point at the backing bar-to-column interface.

6. Confusing the effective throat with the bevel depth. For PJP groove welds, the effective throat is NOT the bevel depth — it is the perpendicular distance from the root to the weld face. In a single-bevel PJP with a root face, the effective throat equals the bevel depth MINUS the root face. In a single-V PJP with a groove angle less than 45 degrees, the effective throat is further reduced per AWS D1.1 Table 2.1. Always verify the throat dimension against the qualified WPS.

Frequently Asked Questions

When is CJP required instead of PJP?

CJP is required when: (1) the connection must develop the full tensile strength of the base metal (e.g., moment frame beam flanges), (2) the connection is subject to fatigue or seismic loading per AISC 341, (3) tension is normal to the effective area and the demand exceeds the PJP capacity at practical penetration depths, or (4) the governing specification expressly requires CJP for the connection type. PJP is adequate for compression, shear, stiffeners, and low-demand tension where the reduced throat meets the factored demand.

How does the groove angle affect the effective throat?

For CJP, the groove angle does not affect strength (it affects weldability and procedure qualification). For PJP, the groove angle affects the effective throat per AWS D1.1 prequalified joint details. For SMAW, groove angles below 45 degrees are generally not prequalified. For SAW and GMAW, smaller angles are acceptable. Narrow groove angles reduce weld volume and distortion but require more precise fit-up and qualified procedures.

What NDT is required for CJP groove welds?

Per AWS D1.1, CJP groove welds in tension applications typically require ultrasonic testing (UT) or radiographic testing (RT). The acceptance criteria depend on the loading condition: statically loaded connections use AWS D1.1 Table 6.2 (UT) or Table 6.1 (RT). Cyclically loaded (seismic) connections use more stringent criteria per AISC 341. Visual inspection is required for all welds regardless of NDT.

What is the minimum preheat for groove welds?

Preheat requirements depend on the base metal category (per AWS D1.1 Table 3.2), the thicker part joined, and the welding process. For A992 steel (Category B), with a thickness of 3/4 in, the minimum preheat is 50°F for SMAW with low-hydrogen electrodes. For thickness over 1-1/2 in, preheat increases to 150°F. For ASTM A913 Grade 65 (Category C), preheat for 3/4 in is 50°F, rising to 225°F for 2-1/2 in and thicker sections.

Can PJP groove welds be used in seismic moment frames?

AISC 341-22 requires CJP groove welds for beam flange-to-column flange welds in special moment frames (SMF) and intermediate moment frames (IMF). PJP welds are not permitted for these connections when they are part of the seismic load resisting system. For ordinary moment frames (OMF), PJP may be acceptable if the design demand at the required penetration depth is satisfied and the connection passes the prequalified testing requirements.

What is the difference between a groove weld and a fillet weld in capacity calculation?

Groove weld capacity (CJP) matches the base metal strength — the formula uses Fy or 0.6 x Fy times the base metal area. Fillet weld capacity uses 0.6 x FEXX (electrode tensile strength) times the effective throat area. The result is that a CJP weld on a 1/2-in plate develops 50% more tensile capacity than the equivalent double-sided fillet weld with matching leg size, because the CJP engages the full plate thickness in the load path.

How does AS 4100 weld category (SP vs GP) affect groove weld capacity?

For CJP groove welds, the weld category (SP or GP) does not apply because the design capacity is based on the base metal strength (phi = 0.90), not the weld metal strength. For PJP groove welds, the SP category (phi = 0.80) provides 33% more capacity than the GP category (phi = 0.60). SP category requires NDT inspection per AS/NZS 1554.1 and qualified welding procedures. GP is for general-purpose welds with visual inspection only.

Run This Calculation

→ Welded Connection Calculator — fillet and groove weld capacity per AISC 360, AS 4100, EN 1993, and CSA S16 with SP/GP category selection and weld type configuration.

→ Bolted Connections Calculator — bolt group design with shear, bearing, and block shear checks. Compare bolted vs welded connection alternatives side by side.

→ Weld Symbol Generator — create AWS A2.4 weld symbols for drawings with correct groove weld notation, tail notes, and joint configuration.

→ Beam Capacity Calculator — check the member capacity that the groove weld is designed to match. Verify that the connected member passes its own strength checks.

Related pages

• Guides and checklists
• Welded connections calculator
• Weld design checklist — fillet & groove weld QA per AWS D1.1
• Weld symbol generator
• Fillet weld size chart — capacity per unit length, E70XX
• Minimum fillet weld size — AISC J2.4 & AS 4100 table
• Weld electrode reference — E60XX, E70XX, E80XX classifications
• Weld symbol chart — AWS A2.4 reference
• Connection design methods compared — bolted, welded & base plate
• Bolted connection worked example — shear per AISC 360
• Steel Fy & Fu reference — yield and tensile strength by grade
• Steel grades reference
• Beam span reference — span-to-depth ratios by load case
• How to verify calculator results
• Disclaimer (educational use only)

Disclaimer (educational use only)

This page is provided for general technical information and educational use only. It does not constitute professional engineering advice, a design service, or a substitute for an independent review by a qualified structural engineer. Any calculations, outputs, examples, and workflows discussed here are simplified descriptions intended to support understanding and preliminary estimation.

All real-world structural design depends on project-specific factors (loads, combinations, stability, detailing, fabrication, erection, tolerances, site conditions, and the governing standard and project specification). You are responsible for verifying inputs, validating results with an independent method, checking constructability and code compliance, and obtaining professional sign-off where required.

The site operator provides the content "as is" and "as available" without warranties of any kind. To the maximum extent permitted by law, the operator disclaims liability for any loss or damage arising from the use of, or reliance on, this page or any linked tools.

Quick-Start Checklist

1. Confirm CJP or PJP. If tension normal to the weld axis is present and demand approaches the base metal strength, specify CJP. PJP is adequate for shear, compression, and stiffeners where Tu <= phi x Fy x A_net.

2. Check base metal strength (CJP). phi Rn = phi x Fy x A_base for tension/compression normal to axis. phi Rn = phi x 0.6 x Fy x A_base for shear. No separate weld metal check with matching electrodes.

3. Check weld metal strength (PJP). phi Rn_weld = phi x 0.6 x FEXX x E_throat x L_weld per AISC J2.4. Verify FEXX >= Fu_base for matching. For undermatching electrodes, the lower strength governs.

4. Check base metal at PJP root. phi Rn_base = phi x Fy x (t_plate - E_throat) x L_weld. This check almost always governs for PJP in tension. If it fails, increase penetration depth or switch to CJP.

5. Verify groove preparation geometry. Per AWS D1.1 Table 2.1: groove angle, root face, root opening, and backing bar details must match a prequalified joint detail. Non-prequalified details require procedure qualification by testing.

6. Specify weld access holes (if required). Per AWS D1.1 Cl. 5.17: for CJP beam flange-to-column flange welds where the web interferes. Minimum length = max(1.5 x tf, 1.5 in). Re-entrant radius >= 3/8 in. Surface roughness <= 500 microinch for seismic per AISC 341.

7. Document WPS and NDT requirements. Record WPS number, electrode classification, preheat/interpass temperatures, and NDT method (UT, RT, MT, PT) with acceptance criteria per the governing specification.

8. Apply code-specific phi/gamma factors. AISC: phi = 0.75 (weld metal), 0.90 (base metal). AS 4100: phi = 0.80 (SP), 0.60 (GP). EN 1993: gamma_M2 = 1.25 (welds), gamma_M0 = 1.00 (base metal). CSA S16: phi = 0.67 (weld metal), 0.90 (base metal). Never mix phi factors across codes.