---------------- | :--------------------------------------------- | :------------------------------- | :-------------: | | Unstiffened — 4 bolt | 2 rows of 2 | Light moment, beams up to W530 | Up to 200 kN·m | | Stiffened — 8 bolt | 4 rows of 2 | Moderate moment, beams W410-W690 | 200-600 kN·m | | Extended — 8 bolt | 2 rows inside + 2 rows outside flange | Moderate moment, deeper beams | 300-800 kN·m | | Extended — 12 bolt | 3 rows inside + 2 rows outside + 1 row outside | Heavy moment, large beams | 500-1200 kN·m |

Bolt Prying Action

Per CSA S16 Clause 13.12.4, bolts in end plate connections are subject to prying action — additional tension from plate flexure:

Prying Force Equation

Q = (M_plate / (p - t_w/2)) / 2

Where:

• Q = prying force per bolt row (kN)
• M_plate = moment in end plate at bolt line per unit width
• p = bolt pitch (distance between tension bolt rows)
• t_w = beam web thickness

Prying Factor Alpha

alpha = (ln(bf/2) / ln(p)) × (tp^2 × Fy × Bp) / (6 × Tf × p)

Where:

• bf = beam flange width
• tp = end plate thickness
• Bp = effective plate width per bolt
• Tf = factored tension force per bolt

Simplified Prying Check

If tp ≥ (0.5 × Tf × bf / (0.90 × Fy × p))^0.5, prying effects are negligible.

For typical connections with tp ≥ 20 mm, prying action increases bolt tension by 20-40%.

End Plate Thickness Design

Per CSA S16 Clause 13.5 (plate bending):

Mr_plate = phi × Z_plate × Fy per unit width of plate

The factored moment in the plate at the bolt line:

Mf_plate = (Tf_per_bolt × p) / (2 × b_eff)

Required plate thickness per unit width for plastic moment:

tp_req = sqrt(4 × Mf_plate / (phi × Fy))

Minimum End Plate Thickness

Weld Design

Flange Welds

Per CSA S16 Clause 13.13, flange welds must develop the flange force:

Ff = Mf / d_beam (flange force from moment)

Web Welds

Per CSA S16, web welds must transfer the factored shear:

Vr_web = 0.67 × phi_w × Xu × 0.707 × D × L_weld

For a W410x60 beam with Vf = 200 kN, using E48XX electrodes: Required D per side (two web welds) = Vf / (2 × 0.67 × phi_w × Xu × 0.707 × L_web) = 200 × 1000 / (2 × 0.67 × 0.67 × 480 × 0.707 × 350) = 1.9 mm → use 6 mm minimum weld.

Worked Example — 4-Bolt Unstiffened End Plate

Given: W410×60 beam (350W) to column W360×216 flange. Moment Mf = 150 kN·m, shear Vf = 120 kN. Four A325M M24 bolts outside the beam tension flange. Plate 350W.

Step 1 — Bolt Design: Flange force: Ff = 150 × 10^6 / (407 - 16.3) = 150 × 10^6 / 390.7 = 384 kN Tension per bolt: Tf = Ff / 4 = 96 kN (assuming equal sharing, no prying — check later) Bolt tension capacity: Tr = 0.75 × phi_b × Ab × Fu = 0.75 × 0.80 × 452 × 830 / 1000 = 240.4 kN 96 ≤ 240.4 kN. OK.

Step 2 — Prying Check: For M24 bolts, p = 100 mm (vertical), bf = 178 mm (beam flange) Conservative Tf_adjusted = 1.25 × 96 = 120 kN (including ~25% prying effect) Check: 120 ≤ 240.4 kN. OK.

Step 3 — End Plate Thickness: Assuming Mf_plate governs at bolt line: tp_req = sqrt(4 × (120,000 × 50) / (0.90 × 350 × 178/2)) = sqrt(24,000,000 / 28,035) = sqrt(856) = 29.3 mm Try 32 mm plate.

Step 4 — Weld Design: Flange welds: Ff = 384 kN, use 10 mm fillet each side. Vr_flange_weld = 2 × (0.67 × 0.67 × 480 × 0.707 × 10) × 178 / 1000 = 543 kN ≥ 384 kN. OK.

Web welds: Vf = 120 kN, use 6 mm fillet each side per CSA W59 minimum. Vr_web = 2 × 0.67 × 0.67 × 480 × 0.707 × 6 × 350 / 1000 = 548 kN ≥ 120 kN. OK.

Step 5 — Column Flange Check: Column flange: W360×216, tf = 25.9 mm. Need to check local flange bending per CSA S16 Clause 14.3. p = 100 mm > tf + k = 25.9 + 32 = 57.9 mm. Stiffener not required if: Tf ≤ 0.60 × phi × tf^2 × Fy_col × (12 × B_flex / (4 × p^2 - t_w_col^2))^0.5 = 0.60 × 0.90 × 25.9^2 × 350 × (12 × / (4 × 100^2 - 12.3^2))^0.5 ≈ 1124 kN ≥ 120 kN. OK (no column stiffeners required).

Result: 4-M24 A325M bolts, 32 mm end plate, 10 mm flange fillet welds, 6 mm web fillet welds. No column stiffeners required.

Column Stiffener Requirements

Per CSA S16 Clause 14.3.2, column stiffeners are required when:

1. Flange local bending: Tf > available capacity from column flange bending formula
2. Web local yielding: Ff > capacity of column web (t_w_col × (tf_col + 5k_col) × Fy_col)
3. Web crippling: Ff > Br capacity per Clause 14.3.2

For W360×216 column: tw = 12.3 mm, tf = 25.9 mm, k = 32 mm.

When stiffeners are required, use full-depth stiffeners (doublers) welded to column web and flanges.

Frequently Asked Questions

What is prying action in end plate connections? Prying action is the additional tensile force in bolts caused by flexural deformation of the end plate. As the plate bends under load, it bears against the bolt head/nut at the outer edges, creating a lever action that amplifies the bolt tension. For unstiffened 4-bolt connections, prying can increase bolt tension by 20-40%. Per CSA S16 Clause 13.12.4, the prying effect must be considered in bolt design.

When are column stiffeners required in Canadian end plate connections? Column stiffeners are required when the column flange or web lacks sufficient capacity to resist the concentrated flange forces from the beam. Per CSA S16 Clause 14.3, check: flange local bending (Tf from bolts), web local yielding (Ff from beam flange compression), and web crippling. For heavy moment connections with W360 or smaller columns, stiffeners are commonly needed. W460+ columns typically resist these forces without stiffeners for moderate moments.

What is the difference between 4-bolt and 8-bolt end plate connections? A 4-bolt unstiffened end plate has two rows of bolts entirely outside the beam tension flange. It is limited by end plate thickness (prying action increases with plate flexibility). An 8-bolt extended connection has additional bolts inside the flange, distributing the tension force more evenly and reducing prying. 8-bolt connections can resist 2-3× the moment of 4-bolt connections with the same plate thickness.

Do end plate welds require full joint penetration groove welds? For flange forces below approximately 1000 kN, fillet welds each side of the flange are adequate per CSA S16. For forces exceeding 1500 kN, complete joint penetration (CJP) groove welds are typically specified. The transition depends on weld size availability: the maximum practical fillet weld is 12 mm (16 mm in heavy fabrication), providing approximately 1.83 kN/mm with E48XX. If Ff/bf > 1.83 kN/mm, a CJP groove weld is needed.

Related Pages

• CSA S16 Shear Tab Connection
• CSA S16 Weld Capacity — Fillet Weld Table
• CSA S16 Bolt Bearing & Tearout
• CSA S16 Bolt Spacing & Edge Distance
• CSA S16 Gusset Plate Design
• CSA S16 Brace Connection
• Welded Connection Calculator
• All Canadian References

This page is for educational reference. End plate connection per CSA S16:24 Clauses 13.12-13.14. Verify column stiffener requirements per Clause 14.3. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

Design Resources

Calculator tools

• Bolted Connection Calculator
• Weld Capacity Calculator
• End Plate Moment Connection Calculator
• Fin Plate Shear Connection Calculator
• Gusset Plate Calculator

Design guides

• Bolted Connection Worked Example
• Bolted Connection Checklist
• Steel Connection Calculator Guide
• Weld Design Checklist
• EN 1993-1-8 Bolted Connection Worked Example

Reference pages

• CA Shear Tab
• UK Moment Connection