Bolted Connection Design Example — AISC 360-22 LRFD Shear Tab
Complete step-by-step design of a bolted shear tab (single-plate) connection following AISC 360-22. This worked example covers bolt shear, bolt bearing on beam web and plate, tear-out, block shear rupture, shear yielding and shear rupture of the plate, and the fillet weld to the column. Every limit state is checked with explicit calculations.
Problem statement
Design a single-plate shear connection (shear tab) between a W21x44 beam and a W14x90 column flange.
Given:
- Beam: W21x44 (A992, Fy = 50 ksi, Fu = 65 ksi)
- Column: W14x90 (A992)
- Connection plate: ASTM A36 (Fy = 36 ksi, Fu = 58 ksi), 3/8 in. thick
- Bolts: 3/4 in. diameter ASTM A325-N (bearing type, threads included in shear plane)
- Factored beam reaction: R_u = 48 kips
- Connection type: Single-plate shear tab, welded to column, bolted to beam web
- Bolt configuration: 3 bolts in a single vertical line, 3 in. pitch
- Edge distance: 1.5 in. (from bolt center to bottom of plate)
- Hole type: Standard holes
Step 1 — Determine bolt layout
Beam web dimensions (W21x44)
| Property | Value |
|---|---|
| d | 20.7 in. |
| tw | 0.350 in. |
| k | 0.950 in. |
| T | 18.8 in. |
Bolt layout
3 bolts at 3 in. pitch:
- Top bolt center: 1.5 in. from top of plate
- Bottom bolt center: 1.5 in. + 2 x 3 in. = 7.5 in. from top of plate
- Plate height: 7.5 + 1.5 = 9 in.
- Plate width: 4 in. (provides 1.25 in. edge distance on each side of bolt)
Minimum edge distance check (Table J3.4M)
For 3/4 in. bolt in standard hole: minimum edge distance = 1.0 in. Actual edge distance = 1.25 in. > 1.0 in. — OK.
Minimum spacing check (J3.3)
Minimum spacing = 2.5 x d_b = 2.5 x 0.75 = 1.875 in. Actual pitch = 3 in. > 1.875 in. — OK.
Step 2 — Bolt shear capacity (AISC Section J3.6)
Single bolt shear strength
For A325-N, 3/4 in. diameter, threads in shear plane (N = bearing type, threads included):
F_nv = 54 ksi (AISC Table J3.2, Condition N)
A_b = pi x d_b^2 / 4 = pi x 0.75^2 / 4 = 0.442 in^2
phi x R_n (per bolt, single shear) = phi x F_nv x A_b
phi x R_n = 0.75 x 54 x 0.442 = 17.9 kips
Total bolt shear capacity (3 bolts, single shear)
phi x R_n (total) = 3 x 17.9 = 53.7 kips
Check: phi x R_n = 53.7 kips > R_u = 48 kips (OK). Utilization = 89%.
Step 3 — Bolt bearing on beam web (AISC Section J3.10)
Check bearing on the thinner element
Beam web tw = 0.350 in. (A992, Fu = 65 ksi). Plate tp = 0.375 in. (A36, Fu = 58 ksi). Since tw < tp and Fu(beam) > Fu(plate), the plate Fu governs for bearing on the plate side, and beam web Fu governs for bearing on the beam side. Check both.
Inner bolts (deformation is a design consideration)
For standard holes with deformation consideration: Clear distance: L_c = s - d_h = 3.0 - 13/16 = 2.19 in. (d_h = 13/16 in. for 3/4 in. bolt)
Bearing on beam web (per bolt):
R_n = 1.2 x L_c x t_w x F_u = 1.2 x 2.19 x 0.350 x 65 = 59.7 kips
Upper limit: 2.4 x d_b x t_w x F_u = 2.4 x 0.75 x 0.350 x 65 = 40.9 kips
R_n = min(59.7, 40.9) = 40.9 kips
phi x R_n = 0.75 x 40.9 = 30.7 kips per bolt
Edge bolt (bottom bolt)
Clear distance to edge: L_c = 1.5 - 13/16 / 2 = 1.09 in.
Bearing on beam web (per bolt):
R_n = 1.2 x L_c x t_w x F_u = 1.2 x 1.09 x 0.350 x 65 = 29.7 kips
Upper limit: 2.4 x d_b x t_w x F_u = 40.9 kips
R_n = min(29.7, 40.9) = 29.7 kips
phi x R_n = 0.75 x 29.7 = 22.3 kips
Total bearing capacity on beam web
phi x R_n = 2 x 30.7 + 22.3 = 83.7 kips
Check: phi x R_n = 83.7 kips > R_u = 48 kips (OK). Utilization = 57%.
Step 4 — Bolt bearing on plate (AISC Section J3.10)
Plate: A36, tp = 0.375 in., Fu = 58 ksi.
Inner bolts
R_n = 1.2 x L_c x t_p x F_u = 1.2 x 2.19 x 0.375 x 58 = 57.1 kips
Upper limit: 2.4 x d_b x t_p x F_u = 2.4 x 0.75 x 0.375 x 58 = 39.2 kips
R_n = min(57.1, 39.2) = 39.2 kips
phi x R_n = 0.75 x 39.2 = 29.4 kips per bolt
Edge bolt
R_n = 1.2 x 1.09 x 0.375 x 58 = 28.4 kips
Upper limit: 39.2 kips
R_n = 28.4 kips
phi x R_n = 0.75 x 28.4 = 21.3 kips
Total bearing capacity on plate
phi x R_n = 2 x 29.4 + 21.3 = 80.1 kips
Check: phi x R_n = 80.1 kips > R_u = 48 kips (OK). Utilization = 60%.
Step 5 — Block shear rupture (AISC Section J4.3)
On beam web
Block shear through the beam web with 3 bolts in a single line:
Shear area (along bolt line):
A_gv = t_w x (2 x 3 + 1.5) = 0.350 x 7.5 = 2.625 in^2
A_nv = A_gv - 2.5 x d_h x t_w x n_bolts_in_line
A_nv = 2.625 - 2.5 x (13/16) x 0.350 x 3 = 2.625 - 2.13 = 0.495 in^2
Wait, let me recalculate. For 3 bolts in a vertical line, the block shear failure is a single vertical tear-out along the bolt line:
A_gv = t_w x L_gv = 0.350 x (3 + 3 + 1.5) = 0.350 x 7.5 = 2.625 in^2
A_nv = A_gv - 3 x (13/16 + 1/16) x t_w (subtracting holes from gross shear area)
= 2.625 - 3 x 0.875 x 0.350 = 2.625 - 0.919 = 1.706 in^2
Tension area (horizontal tear at top bolt):
A_nt = t_w x (edge_distance - d_h/2) = 0.350 x (1.25 - 0.406) = 0.350 x 0.844 = 0.296 in^2
Block shear capacity:
R_n = 0.6 x F_u x A_nv + U_bs x F_u x A_nt (J4.3, tensile rupture controls)
= 0.6 x 65 x 1.706 + 1.0 x 65 x 0.296
= 66.5 + 19.2 = 85.7 kips
phi x R_n = 0.75 x 85.7 = 64.3 kips
Check: phi x R_n = 64.3 kips > R_u = 48 kips (OK). Utilization = 75%.
Step 6 — Shear yielding of plate (AISC Section J4.2)
A_gv = t_p x h_p = 0.375 x 9 = 3.375 in^2
R_n = 0.60 x F_y x A_gv = 0.60 x 36 x 3.375 = 72.9 kips
phi x R_n = 1.0 x 72.9 = 72.9 kips
Check: phi x R_n = 72.9 kips > R_u = 48 kips (OK). Utilization = 66%.
Step 7 — Shear rupture of plate (AISC Section J4.4)
Net area through bolt holes:
A_nv = A_gv - n x (d_h + 1/16) x t_p
= 3.375 - 3 x 0.875 x 0.375
= 3.375 - 0.984 = 2.391 in^2
R_n = 0.60 x F_u x A_nv = 0.60 x 58 x 2.391 = 83.2 kips
phi x R_n = 0.75 x 83.2 = 62.4 kips
Check: phi x R_n = 62.4 kips > R_u = 48 kips (OK). Utilization = 77%.
Step 8 — Fillet weld to column (AISC Section J2.4)
Weld configuration
Two vertical fillet welds, each 9 in. long (full plate height), one on each side of the plate at the column flange.
Weld size
Minimum weld size per Table J2.4: For 0.375 in. plate thickness, minimum fillet weld = 3/16 in.
Use w = 5/16 in. fillet weld (provides capacity margin).
Weld capacity
Electrode: E70XX. F_EW = 70 ksi.
For a linear fillet weld group:
phi x R_n = phi x 0.60 x F_EXX x (0.707 x w) x L_w x 2 (two welds)
phi x R_n = 0.75 x 0.60 x 70 x 0.707 x 5/16 x 9 x 2
phi x R_n = 0.75 x 0.60 x 70 x 0.221 x 18
phi x R_n = 0.75 x 167 = 125 kips
Check: phi x R_n = 125 kips > R_u = 48 kips (OK). Utilization = 38%.
Weld is over-designed. Reduce to 1/4 in. fillet:
phi x R_n = 0.75 x 0.60 x 70 x 0.707 x 0.25 x 18 = 100 kips > 48 kips (OK).
Even 3/16 in. weld works: phi x R_n = 75 kips > 48 kips. Use 3/16 in. fillet weld (minimum per Table J2.4).
Step 9 — Summary of all limit states
| Limit State | Demand (kips) | Capacity (kips) | phi | Utilization | Status |
|---|---|---|---|---|---|
| Bolt shear (3 x A325-N) | 48 | 53.7 | 0.75 | 89% | Governs |
| Bolt bearing on beam web | 48 | 83.7 | 0.75 | 57% | OK |
| Bolt bearing on plate | 48 | 80.1 | 0.75 | 60% | OK |
| Block shear (beam web) | 48 | 64.3 | 0.75 | 75% | OK |
| Shear yielding (plate) | 48 | 72.9 | 1.00 | 66% | OK |
| Shear rupture (plate) | 48 | 62.4 | 0.75 | 77% | OK |
| Fillet weld (3/16 in.) | 48 | 75.0 | 0.75 | 64% | OK |
Bolt shear governs at 89% utilization. All other limit states pass comfortably.
Connection detail summary
Plate: 3/8 in. x 4 in. x 9 in., ASTM A36
Bolts: (3) 3/4 in. diameter ASTM A325-N, standard holes
Pitch: 3 in. vertical spacing
Edge distance: 1.5 in. top and bottom, 1.25 in. each side
Weld: 3/16 in. fillet weld each side, 9 in. long, E70XX electrode
Capacity: phi*R_n = 48 kips (bolt shear governs)
Design comparison — alternative bolt configurations
| Configuration | phi*R_n (kips) | Governing Limit | Utilization |
|---|---|---|---|
| 3 bolts x A325-N | 53.7 | Bolt shear | 89% |
| 3 bolts x A325-SC | 66.9 | Shear rupture | 72% |
| 4 bolts x A325-N | 71.6 | Block shear | 67% |
| 3 bolts x A490-N | 74.4 | Shear rupture | 65% |
| 2 rows x 3 bolts A325-N | 107.4 | Block shear | 45% |
Switching from A325-N to A325-SC (slip-critical) increases bolt shear capacity by 25% but adds 30-50% cost. For gravity connections, bearing-type (N) is sufficient.
Cross-code comparison for bolted connections
| Check | AISC 360-22 | AS 4100:2020 | EN 1993-1-8 | CSA S16:19 |
|---|---|---|---|---|
| Bolt shear | J3.6 | Cl. 9.3.2 | Table 3.4 | Cl. 13.12.1 |
| Bearing | J3.10 | Cl. 9.3.2.4 | Table 3.4 | Cl. 13.12.2 |
| Block shear | J4.3 | AS 4100 Appendix | EN 1993-1-8 3.10.2 | Cl. 13.11 |
| Shear yielding | J4.2 | Cl. 9.3.1 | EN 1993-1-1 6.2.6 | Cl. 13.4 |
| phi (bolt shear) | 0.75 | 0.80 | gamma_M2 = 1.25 | 0.80 |
| phi (bearing) | 0.75 | 0.80 | gamma_M2 = 1.25 | 0.80 |
All four codes check the same fundamental limit states. The capacity values are similar. The main difference is in phi/gamma factors.
Common mistakes in bolted connection design
Using nominal bolt diameter for bearing calculations instead of hole diameter. Standard holes for 3/4 in. bolts are 13/16 in. diameter. Bearing and tear-out use the hole diameter, not the bolt diameter.
Forgetting to check block shear. Block shear is a combined tension-shear failure that can be more critical than bolt shear for short connections with closely-spaced bolts. It is often the governing limit state for single-plate connections.
Specifying slip-critical connections for gravity shear. Most gravity connections are bearing-type with snug-tight bolts. Slip-critical adds 30-50% cost for no benefit in non-reversing, non-fatigue applications.
Not accounting for bolt hole deformation. The bearing capacity depends on whether deformation at service load is a design consideration. For most building connections, use the "deformation is a design consideration" values (lower capacity, AISC J3.10(a)).
Ignoring eccentricity in the connection. Single-plate shear tabs have inherent eccentricity between the bolt group and the weld line. AISC Manual Part 10 provides tables that account for this eccentricity through the "instantaneous center of rotation" method.
Using wrong phi factors. Bolt shear uses phi = 0.75. Shear yielding uses phi = 1.0. Shear rupture uses phi = 0.75. Fillet weld uses phi = 0.75. Mixing these up changes results significantly.
Frequently asked questions
What is the difference between A325-N and A325-SC? A325-N is bearing-type with threads included in the shear plane. A325-SC is slip-critical (faying surfaces must be prepared, bolts pretensioned). SC has 25% higher nominal shear stress (68 ksi vs 54 ksi for 3/4 in. A325) but costs 30-50% more. Use N for gravity connections, SC for seismic, fatigue, or load-reversal applications.
How many bolts do I need for a 50 kip reaction? Three 3/4 in. A325-N bolts provide 53.7 kips capacity. Two bolts provide only 35.8 kips (insufficient). Four bolts provide 71.6 kips with margin.
Does bolt spacing affect capacity? Yes. Closer spacing reduces the clear distance between bolts (L_c), which reduces bearing capacity. The minimum spacing is 2.5d_b (1.875 in. for 3/4 in. bolts), but 3 in. is the practical minimum for wrench access.
When should I use A490 instead of A325? A490 bolts are 40% stronger in shear (F_nv = 75 ksi vs 54 ksi for N condition). Use A490 when bolt shear governs and you cannot fit more bolts. A490 costs about 50% more than A325 and cannot be galvanized (hydrogen embrittlement risk).
What is block shear and why does it matter? Block shear is a tearing-out failure where a block of material separates from the connected element. It involves simultaneous shear failure along one plane and tension failure on a perpendicular plane. For single-plate connections with 3 or fewer bolts, block shear often governs.
Do I need to check the weld if the bolts govern? Yes. Every limit state must be checked independently. The connection fails at the weakest link. Even if bolt shear is the lowest capacity, the weld, plate yielding, and block shear must all exceed the demand.
Run this calculation
Related references
- Steel Connection Design
- Bolt Capacity Table
- Bolt Grades
- Bolt Spacing
- Bolt Holes
- Shear Tab Connection
- Connection Ductility
- Fillet Weld Size Chart
- 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 the applicable standard and project specification before use. The site operator disclaims liability for any loss arising from this information.