Shear Tab Design — Single Plate Connection Reference
The shear tab (single plate connection) is the most common steel connection in building construction. A rectangular plate is shop-welded to the supporting member (column flange or girder web) and field-bolted to the beam web. It transfers vertical shear from the beam to the support and is designed as a simple (pin) connection.
Anatomy of a shear tab
- Plate: Typically 1/4" to 1/2" thick A36 steel, width 3" to 4.5"
- Weld: Fillet weld on both sides of the plate to the support (shop weld)
- Bolts: Single vertical line of bolts through the beam web (field bolts)
- Standard configuration: 2 to 12 bolts, 3" spacing, 3/4" or 7/8" A325-N
Design checks per AISC Manual Part 10
Bolt shear
Each bolt in single shear: phiRn = 0.75 _ Fnv _ Ab. For 3/4" A325-N: phiRn = 17.9 kips. Total = n * 17.9 kips for n bolts.
Bolt bearing and tearout on plate and beam web
Check each bolt for bearing (phiRn = 0.752.4dtFu) and tearout (phiRn = 0.751.2LctFu) on both the plate and the beam web. The thinner element governs. End bolts have shorter Lc and lower tearout capacity.
Plate gross shear yielding
phiRn = 1.00 * 0.60 * Fy * Ag_plate = 1.00 * 0.60 * 36 * tp * Lp
Where tp = plate thickness, Lp = plate length (n bolts * 3" spacing + edge distances).
Plate net shear rupture
phiRn = 0.75 * 0.60 * Fu * Anv = 0.75 * 0.60 * 58 * (Lp - n*dh) * tp
Block shear on plate
phiRn = 0.75 * (0.60*Fu*Anv + Ubs*Fu*Ant)
Weld strength
The weld must resist the beam reaction. For a plate with weld on both sides:
phiRn = 2 * 0.75 * 0.60 * FEXX * 0.707 * w * Lw
Where w = weld leg size, Lw = weld length (= plate length). The weld also resists the eccentric moment from the bolt line to the weld line.
Plate flexural yielding (eccentricity)
The beam reaction acts at the bolt line, creating a moment about the weld line. Eccentricity e = distance from bolt line to weld. For conventional configurations per AISC Manual Part 10, the eccentricity may be taken as zero for the bolt check and applied to the weld check, or vice versa, depending on the configuration (extended or conventional).
Conventional configuration (AISC Manual): When the plate dimensions satisfy AISC Manual Part 10 criteria (a <= tp, n <= 12, standard holes, etc.), the eccentricity may be neglected for the bolt group check. The weld is designed for the eccentric moment.
AISC Manual Table 10-9a capacity (A325-N, 3/4" bolts, A36 plate)
| n bolts | Plate 1/4" (kips) | Plate 5/16" (kips) | Plate 3/8" (kips) |
|---|---|---|---|
| 2 | 25.1 | 31.4 | 35.8 |
| 3 | 44.2 | 55.2 | 65.4 |
| 4 | 59.5 | 74.4 | 89.2 |
| 5 | 74.5 | 93.1 | 111.7 |
| 6 | 89.3 | 111.7 | 134.0 |
Values are approximate and depend on specific geometry. Always verify with the actual AISC Manual table for your configuration.
Conventional vs. extended shear tabs
Conventional: Plate attached to a column flange or beam web with a distance from the weld to the bolt line approximately equal to the bolt gage (typically 2.5" to 3"). The eccentricity effect is small and handled per AISC Manual Part 10.
Extended: The plate extends significantly beyond the support face (e.g., when the beam frames to a column web and the plate must extend past the column flanges). Extended shear tabs require explicit eccentricity analysis for both the bolt group and the weld.
Design tips
- Plate thickness: Use tp <= (beam web thickness + 1/16") to ensure the plate is the weaker element (ductile failure in the plate rather than brittle failure in the beam web).
- Minimum weld size: Fillet weld size >= 5/8 * tp to ensure the weld is not the weakest link.
- Erection bolts: Standard practice is to install at least two bolts before releasing the crane. Minimum 2-bolt connection for erection stability.
- Bolt holes in beam web: Standard holes in both plate and beam web for conventional configurations. Short-slotted holes in the plate are sometimes used for erection tolerance.
Common mistakes
- Not checking the beam web for bearing/tearout. The beam web is often thinner than the plate and may govern.
- Ignoring eccentricity for extended shear tabs. Extended configurations require explicit bolt group eccentricity analysis.
- Plate too thick relative to beam web. If the plate is much thicker than the beam web, failure occurs in the beam web (less ductile). Keep tp <= tw_beam + 1/16".
- Undersized weld. The weld must resist both direct shear and the eccentric moment from the bolt line offset.
- Not checking block shear on the plate. Block shear can govern, especially for 2-bolt or 3-bolt configurations.
Frequently asked questions
What is a shear tab? A single plate welded to the support and bolted to the beam web. It transfers vertical shear only and is modeled as a pin connection.
How many bolts in a shear tab? Typically 2 to 12. The number depends on the beam reaction. Most common: 3-bolt (light beams) to 5-bolt (medium beams) configurations.
Can a shear tab transfer moment? No, by design intent. Shear tabs are simple connections that allow beam-end rotation. While some incidental moment develops, the connection is not designed for it.
Run this calculation
Related references
- Steel Connection Types
- Bolt Capacity Table
- Bolt Bearing and Tearout
- Coped Beam Design
- Minimum Weld Size
- How to Verify Calculations
Disclaimer
This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against AISC 360-22 and AISC Manual Part 10. The site operator disclaims liability for any loss arising from the use of this information.