• | ------ | ------- | ------------ | ------------ | ----------------- | ------------------ | | W12x26 | 12.2 | 0.230 | 2.17 | 0.18 | 2-1/2" x 1/4" | 3.55 | | W16x40 | 16.0 | 0.305 | 2.33 | 0.19 | 2-1/2" x 1/4" | 4.33 | | W18x50 | 18.0 | 0.355 | 2.56 | 0.21 | 3" x 1/4" | 5.37 | | W21x62 | 21.0 | 0.400 | 2.58 | 0.22 | 3" x 1/4" | 5.80 | | W24x76 | 23.9 | 0.440 | 2.89 | 0.24 | 3" x 5/16" | 7.51 | | W24x131 | 25.4 | 0.605 | 2.86 | 0.24 | 3" x 5/16" | 10.2 | | W27x94 | 26.7 | 0.490 | 3.11 | 0.26 | 3-1/2" x 5/16" | 8.72 | | W30x90 | 29.5 | 0.470 | 3.43 | 0.28 | 3-1/2" x 5/16" | 8.58 | | W33x118 | 33.3 | 0.550 | 3.66 | 0.30 | 4" x 5/16" | 10.9 | | W36x135 | 35.6 | 0.600 | 3.73 | 0.31 | 4" x 3/8" | 13.9 |

bst >= bf/3 - tw/2. tst >= bst / (0.56 * sqrt(E/Fy)). For Fy = 36 ksi, tst >= bst/15.9. For Fy = 50 ksi, tst >= bst/13.5.

Bearing stiffener capacity table

All stiffeners very stocky (KL/r < 5), so phiPn is approximately 0.90 _ Fy _ A.

When stiffeners are required

Web checks that trigger bearing stiffeners (AISC J10)

When transverse stiffeners are needed for shear

For Fy = 50 ksi: 2.24*sqrt(E/Fy) = 53.9. Nearly all standard W-shapes have h/tw below this threshold.

Transverse stiffener requirements (AISC G2.2)

Minimum dimensions

bst >= d/3 - tw/2   (per side)
tst >= bst / (0.56 * sqrt(E/Fy))
bst/tst <= 0.56 * sqrt(E/Fy)

Spacing requirements

Where a = stiffener spacing, h = clear web depth. Closer spacing = higher shear capacity.

Stiffener moment of inertia requirement

Ist >= a * tw^3 * (2.5 / (a/h)^2 - 2) >= 0

This ensures the stiffener is stiff enough to act as a nodal line for the web buckling mode.

Worked example -- bearing stiffener at beam support

Beam: W24x62 (A992), d = 23.74 in, tw = 0.430 in, tf = 0.590 in, h/tw = 50.0. Support reaction Ru = 120 kips. Bearing length N = 3.5 in.

Web local yielding (J10-2, at support): phi*Rn = 1.0 x (2.5 x 1.34 + 3.5) x 50 x 0.430 = 147 kips > 120 kips. OK.

Web crippling (J10-4, at support): phi*Rn = 0.75 x 0.40 x 0.430^2 x [1 + 3(3.5/23.74)(0.430/0.590)^1.5] x sqrt(29000 x 50 x 0.590/0.430) = 0.75 x 0.0739 x 1.316 x 141.8 = 10.3 kips. Far less than 120 kips -- web crippling fails.

Bearing stiffeners required. Try 2 plates, 5" x 1/2" each side, A36.

Effective section: Stiffener area = 2 x 5.0 x 0.50 = 5.0 in^2. Web strip = 25 x 0.430 on each side = 9.25 in^2. Total A = 14.25 in^2.

KL/r = 0.75 x (23.74 - 1.18) / 5.32 = 3.2. Very stocky. phiPn = 0.90 x 36 x 14.25 = 462 kips >> 120 kips OK.

Worked example -- transverse stiffener for plate girder

Built-up plate girder: d = 72 in, tw = 3/8 in (0.375 in), h = 70 in, h/tw = 187. Stiffener spacing a = 42 in (a/h = 0.60).

Stiffener dimensions: bst >= 70/3 - 0.375/2 = 23.1 in... wait, that's for bearing stiffeners. For transverse: bst per G2.2, Ist >= a _ tw^3 _ (2.5/(a/h)^2 - 2) = 42 x 0.375^3 x (2.5/0.36 - 2) = 42 x 0.0527 x 4.94 = 10.95 in^4.

Try single-sided stiffener 4" x 3/8": Ist = 0.375 x 4.0^3 / 3 = 8.0 in^4. Insufficient. Try 5" x 3/8": Ist = 0.375 x 5.0^3 / 3 = 15.6 in^4 > 10.95. OK.

For double-sided stiffeners 3" x 5/16" each: Ist = 2 x (0.3125 x 3.0^3/3 + 0.3125 x 3.0 x (0.375/2 + 1.5)^2) = 2 x (2.81 + 2.43) = 10.48. Close but slightly insufficient. Use 3-1/2" x 5/16" each side.

Weld requirements for stiffeners

Minimum fillet weld size per AISC Table J2.4

Fatigue consideration

Welding transverse stiffeners to the tension flange creates a Category C fatigue detail (AISC Appendix 3, Table A-3.1). For crane girders and bridge beams, stop the stiffener 4tw to 6tw short of the tension flange to maintain Category B at the web-to-flange weld.

Multi-code comparison

Cross-code bearing stiffener capacity: W24x76 + 2x(3"x5/16")

Common mistakes

1. Welding transverse stiffeners to the tension flange in fatigue-sensitive locations. Creates a Category C fatigue detail. For crane girders and bridge beams, stop the stiffener 4tw to 6tw short of the tension flange.

2. Omitting the bearing check at interior point loads. Engineers often check supports for web crippling but forget that any column or beam bearing on the girder flange applies the same concentrated load. Every point load location needs the J10.2-J10.5 checks.

3. Using too-thin stiffener plates. Stiffener outstands must satisfy the compactness limit to prevent local buckling before the stiffener reaches its design load. The thickness limit is bst * sqrt(Fy/E) / 0.56 per AISC.

4. Not fitting bearing stiffeners to both flanges. Bearing stiffeners must be in contact with (or welded to) both flanges to transfer the full reaction. A stiffener welded to the web but not bearing on the flanges is a transverse stiffener, not a bearing stiffener.

5. Ignoring the web strip contribution. The effective column section includes a strip of web (25tw each side). Forgetting this overestimates the required stiffener area, but ignoring it entirely (designing the stiffener plate alone) is unconservative for the bearing check.

6. Using single-sided stiffeners for bearing. Bearing stiffeners should be placed on both sides of the web to avoid eccentricity. Single-sided stiffeners introduce bending in the effective column.

Frequently asked questions

When do I need bearing stiffeners? When the required reaction or concentrated load exceeds the web local yielding (J10.2) or web crippling (J10.3) capacity. For W18 and smaller sections with thin webs, stiffeners are often needed at end reactions.

What is the difference between bearing and transverse stiffeners? Bearing stiffeners are fitted to both flanges and resist concentrated loads. Transverse stiffeners are welded to the web only and increase shear capacity through tension field action. They serve different purposes and have different design requirements.

Do standard rolled W-shapes need transverse stiffeners? Almost never. The h/tw ratio for standard W-shapes is below 53.9 at Fy = 50 ksi, giving Cv1 = 1.0 and full shear capacity without stiffeners. Only plate girders and built-up sections typically need them.

What is tension field action? After a web panel buckles in shear, the diagonal buckles form a tension field that acts like diagonal bracing. The transverse stiffeners act as vertical members of this truss. This post-buckling strength is permitted by AISC G2.2 and significantly increases the design shear capacity.

Can I use partial-depth stiffeners? Partial-depth stiffeners are not permitted for bearing stiffeners (must be full depth). Transverse stiffeners may be partial depth in some codes, but AISC G2.2 requires full depth for tension field action.

How are stiffeners attached to the beam? Bearing stiffeners are fillet-welded to the web and either milled-to-bear or welded to both flanges. Transverse stiffeners are fillet-welded to the web, typically with a gap at the tension flange for fatigue.

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Related references

• Plate Girder Design
• Beam Web Design
• Coped Beam End Design
• Lateral-Torsional Buckling
• Steel Crane Girder
• Weld Capacity
• Connection Types
• Welded Connections Calculator
• How to Verify Calculations

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This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against the applicable standard and project specification before use. The site operator disclaims liability for any loss arising from the use of this information.