Connection Design Workflow — Engineering Reference

AISC 360 steel connection design workflow: load path, bolt shear/bearing, block shear, weld sizing, plate checks, and interactive bolt capacity calculator.

Overview

Designing a steel connection is a multi-step process that starts with identifying the forces to be transferred, selecting a connection type, sizing the fasteners and plates, and then verifying all applicable limit states. A systematic workflow prevents missed checks — a common source of connection failures. The AISC Manual Part 9 (Design of Connecting Elements) and Part 10 (Design of Simple Shear Connections) provide the framework used by most practicing engineers in North America.

The workflow differs depending on whether the connection is a simple shear connection (transferring only vertical reaction), a moment connection (transferring shear plus moment), or a bracing connection (transferring axial force). Each type has a different set of governing limit states, but the overall approach follows the same logical sequence.

Connection type selection guide

Use this table to narrow down the appropriate connection type early in design. Selection depends on the forces to be transferred, the required capacity, and the relative fabrication and erection cost.

Cost ratings: 1 = most economical (simplest fabrication), 5 = most expensive (complex fabrication and fit-up). Actual cost varies with project market conditions, lot size, and connection geometry.

Step-by-step workflow for a bolted shear connection

Step 1: Determine design forces

Identify the factored beam end reaction R_u from the structural analysis. Include gravity, wind, and seismic load combinations. For connections that also serve as collectors or drag struts, include the axial force from the lateral analysis.

Step 2: Select connection type

Choose from shear tab, double angle, single angle, or seated connection based on reaction magnitude, beam depth, column orientation, and erection requirements. Use the AISC Manual selection tables as a starting point.

Step 3: Size bolts for shear

Determine the number of bolts required: n >= R_u / (phi x r_n), where phi x r_n is the single-bolt design shear strength. For 3/4 in. A325-N in single shear: phi x r_n = 0.75 x 54 x 0.4418 = 17.9 kip.

Step 4: Check bolt bearing and tearout

For each bolt, check bearing on both the connected plate and the beam web. The bearing strength is: phi x R_n = 0.75 x 1.2 x L_c x t x F_u (per bolt), capped at 0.75 x 1.5 x d x t x F_u. L_c is the clear distance to the next hole or to the edge.

Step 5: Check block shear rupture

Block shear (AISC J4.3) checks the combined failure of a tension rupture plane and a shear yielding/rupture plane: R_n = 0.6 x F_u x A_nv + U_bs x F_u x A_nt, capped at 0.6 x F_y x A_gv + U_bs x F_u x A_nt. This check applies to the beam web, the connection plate, and the gusset plate if applicable.

Step 6: Check plate yielding and rupture

• Gross section yielding: phi x R_n = 1.00 x F_y x A_g (for shear: 0.60 x F_y x A_g)
• Net section rupture: phi x R_n = 0.75 x F_u x A_n (for shear: 0.60 x F_u x A_n)
• Plate flexure (if eccentric): check plate bending at the bolt line

Step 7: Size weld (if welded to support)

For a shear tab welded to a column flange: weld length = plate length, fillet weld size per AISC Table J2.4 minimum. Weld strength: phi x R_n = 0.75 x 0.60 x F_EXX x t_e x L, where t_e = 0.707 x weld leg size.

Step 8: Check supporting member

Verify the column web or flange can resist the concentrated beam reaction — check web yielding (J10.2), web crippling (J10.3), and web sidesway buckling (J10.4).

Bolt capacity quick reference

All values shown are design strength (phi x R_n) with phi = 0.75. Shear values assume threads included in the shear plane (N condition). X condition excludes threads from the shear plane and yields higher values. Bolt hole assumed standard (d + 1/16 in.).

Bearing values above assume 1.5 in. edge distance and 3 in. spacing with F_u = 58 ksi (A36 plate). Bearing capacity changes with plate material strength, edge distance, and bolt spacing — always verify for your specific geometry. Shear values use F_nv = 54 ksi (A325-N), 68 ksi (A325-X), 68 ksi (A490-N), 84 ksi (A490-X) per AISC Table J3.2.

Limit state priority by connection type

Understanding which limit states typically govern for each connection type helps focus the design effort. The table below shows primary (frequently controls), secondary (often checks out but must be verified), and rarely (usually adequate but verify for unusual geometry) classifications.

These classifications are based on typical geometry and loading. Unusual configurations — such as very thin plates, short edge distances, or heavy reactions on light members — can shift which limit state governs. Always check every applicable limit state regardless of the expected priority.

Limit state checklist

Prying action check summary

Prying action occurs in T-connection geometries where a flexible plate (such as an angle leg or flange plate) is pulled away from the support by a bolt. The plate deforms, generating additional prying force Q in the bolts. Prying action is most common in moment connection flange plates, angle connections, and hanger-type connections.

When prying action applies

Prying must be checked whenever bolts are loaded in tension through a flexible connecting element. Typical cases include:

• End-plate moment connections (both flush and extended)
• Angle connections loaded in tension (bracing connections)
• Hanger connections (single angles or T-sections supporting tension)
• Base plates with overturning moment (anchor rods in tension)

Prying force formula (AISC Manual Part 9)

The prying force Q is determined using the method in AISC Manual Part 9 (Prying Action). For a T-stub or end-plate connection:

Required bolt strength including prying:

T_u,req = T + Q

Where:

• T = applied tension per bolt (kip)
• Q = prying force per bolt (kip)

The prying force Q depends on the flexural stiffness of the plate relative to the bolt elongation. Using the AISC Manual approach (Tables 7-5 through 7-15 or the analytical method):

Case 1 — Thick plate (no prying): If the plate is sufficiently thick, Q = 0 and the full bolt tensile strength is available. This occurs when:

t >= 1.11 x sqrt(T x b' / (p x F_y))

Case 2 — Thin plate (with prying): If the plate is thinner, prying develops and the required bolt strength increases. The prying force is:

Q = (1 / alpha) x (B / T - 1) x [(b' / a') x (t^3 x p x F_y / (25.6 x B x a'^2))]

Where:

• B = available bolt tensile strength per bolt (phi x r_n) (kip)
• a' = a + 0.5d_b, where a is the distance from bolt centerline to plate edge (max a = 1.25b)
• b' = b - 0.5d_b, where b is the distance from bolt centerline to the plate contact point
• p = tributary width per bolt (in.)
• alpha = flexibility coefficient (typically 1.0 for equilibrium method)
• d_b = bolt diameter (in.)

How to reduce prying

Worked prying calculation

Given: W18x50 beam to column flange end-plate moment connection. Flange tension force T_u = 120 kip (total), 2 bolts per flange (4 bolts total in tension on tension flange). End plate: 3/4 in. thick A572 Gr. 50 (F_y = 50 ksi). 7/8 in. A325-N bolts.

Bolt available tensile strength: phi x r_n = 0.75 x 113 x 0.6013 = 51.0 kip per bolt.

Applied tension per bolt: T = 120 / 4 = 30.0 kip per bolt.

Geometry: b = 2.0 in. (bolt center to contact point), a = 1.5 in. (bolt center to plate edge), d_b = 7/8 in. = 0.875 in.

b' = 2.0 - 0.5(0.875) = 1.563 in. a' = 1.5 + 0.5(0.875) = 1.938 in. (check: a' <= 1.25 x b' = 1.953 in. -- OK) p = 4.0 in. (bolt spacing tributary width per bolt on the flange)

Check if thick plate condition applies:

t_req = 1.11 x sqrt(T x b' / (p x F_y)) = 1.11 x sqrt(30.0 x 1.563 / (4.0 x 50)) = 1.11 x sqrt(0.234) = 1.11 x 0.484 = 0.538 in.

Since t = 0.75 in. > 0.538 in., the plate is sufficiently thick, Q = 0. No prying force.

Required bolt capacity = T = 30.0 kip. Available = 51.0 kip per bolt. 30.0 < 51.0 -- OK.

If the plate had been 1/2 in. thick instead, the thick plate check would fail (0.50 < 0.538), and the prying calculation would apply. The Q value would be computed and added to T to get the total required bolt strength.

Weld sizing quick reference

Fillet weld capacity per inch (E70XX electrode)

Weld design strength per inch of length: phi x R_n = 0.75 x 0.60 x 70 x (0.707 x w) = 22.25 x w kip/in., where w is the weld leg size in inches.

Minimum fillet weld size per AISC Table J2.4

The minimum weld size is determined by the thinner of the two parts being joined. These minimums ensure adequate heat input for proper fusion.

Note: The maximum effective fillet weld size along the edge of a part less than 1/4 in. thick equals the material thickness. For parts 1/4 in. and thicker, the maximum along an edge is the material thickness minus 1/16 in. (AISC Section J2.2b).

Connection design checklist

Use this checklist for every connection design. Mark each item as you complete it to ensure no limit state is missed.

1. Determine design forces -- Obtain factored reactions (R_u) from the structural model. Include all applicable load combinations (LRFD). For moment connections, identify both the shear and the moment. For bracing connections, identify the axial force and any eccentricity.

2. Select connection type -- Choose the connection configuration based on force magnitude, member orientation, erection sequence, and access. Refer to the Connection Type Selection Guide above.

3. Lay out bolt group -- Determine the number of bolts, bolt diameter, grade, and pattern (vertical column spacing, horizontal gage, edge distances). Verify minimum spacing (2.67d_b per J3.3) and minimum edge distance (J3.4).

4. Check bolt shear -- Calculate phi x r_n per bolt from AISC Table J3.2. Multiply by number of bolts and by 2 for double shear. Check: phi x R_n >= R_u. If eccentricity is present, use the elastic or instantaneous center method.

5. Check bolt bearing and tearout -- For each connected element, compute the bearing strength at each bolt. Edge bolts use the clear distance to the edge; interior bolts use the clear distance to the adjacent hole. Check both tearout (deformation is a design consideration) and bearing. Use the lower of the two.

6. Check block shear rupture -- Identify all potential block shear failure paths through the bolt group on the beam web, connection plate, and gusset. Compute A_gv, A_nv, A_nt. Check both equations: 0.6F_uA_nv + U_bsF_uA_nt and 0.6F_yA_gv + U_bsF_uA_nt.

7. Check plate (yielding and rupture) -- Check gross section shear yielding and net section shear rupture on the connection plate. For eccentric connections, check plate flexural yielding.

8. Size welds -- Determine the required fillet weld size based on the applied force, weld length, and weld strength. Verify the weld size meets minimum per Table J2.4. For single-plate shear tabs, check both sides of the weld line.

9. Check supporting member -- For beam-to-column connections, check column web local yielding (J10.2), web local crippling (J10.3), and web sidesway buckling (J10.4). For columns with concentrated forces on the flange, check flange local bending (J10.1).

10. Review detailing -- Verify that the connection is constructible: bolt access, wrench clearance, welding access, and erection tolerances. Check that beam-to-column connections account for cope requirements where the beam flange intersects the column flange.

Worked example — shear tab limit state summary

Given: W21x44 beam, R_u = 60 kip, 3/8 in. x 9 in. shear tab plate (A36, F_y = 36 ksi, F_u = 58 ksi), three 3/4 in. A325-N bolts at 3 in. spacing, 1.5 in. edge distance, 5/16 in. fillet weld to W14 column.

1. Bolt shear: 3 bolts x 17.9 kip = 53.7 kip. 53.7 < 60 — need 4 bolts.** Revise to 4 bolts at 3 in. spacing (plate becomes 12 in. long). 4 x 17.9 = **71.6 kip > 60. OK.
2. Bearing on plate (t = 3/8 in.): L_c at edge bolt = 1.5 - 13/32 = 1.094 in. R_n = 0.75 x 1.2 x 1.094 x 0.375 x 58 = 21.4 kip. Interior bolts: L_c = 3.0 - 13/16 = 2.188 in. R_n = 0.75 x min(1.2 x 2.188 x 0.375 x 58, 1.5 x 0.75 x 0.375 x 58) = 0.75 x min(57.1, 24.5) = 18.4 kip. Total = 21.4 + 3 x 18.4 = 76.6 kip > 60. OK.
3. Block shear on plate: A_gv = 2 x (10.5 x 0.375) = 7.875 in^2. A_nv = 7.875 - 2 x 3.5 x (13/16+1/16) x 0.375 = 5.578 in^2. A_nt = (1.5 x 0.375) - 0.5 x (13/16+1/16) x 0.375 = 0.398 in^2. R_n = 0.75 x (0.6 x 58 x 5.578 + 1.0 x 58 x 0.398) = 0.75 x (194.1 + 23.1) = 162.9 kip > 60. OK.
4. Weld: 5/16 in. fillet, two lines x 12 in. = 24 in. total. phi x R_n = 0.75 x 0.6 x 70 x 0.707 x 5/16 x 24 = 0.75 x 0.6 x 70 x 0.221 x 24 = 167 kip > 60. OK.

Worked example — double angle connection

Given: W18x46 beam to W14x90 column flange. Factored reaction R_u = 85 kip. Connection: Two L4x4x3/8 angles (A36, F_y = 36 ksi, F_u = 58 ksi). Four 3/4 in. A325-N bolts in a single vertical column at 3 in. spacing, 1.5 in. edge distance. Beam web: A992 (F_y = 50 ksi, F_u = 65 ksi), t_w = 0.335 in.

Bolt shear

A325-N, 3/4 in., single shear per bolt = 17.9 kip.

Bolts to beam web (single shear through web + 2 angles): each bolt has 2 shear planes (one per angle leg). phi x R_n per bolt = 2 x 17.9 = 35.8 kip (double shear through the two angles, but single shear through the beam web).

For the beam web (single shear plane): 4 bolts x 17.9 = 71.6 kip. For the angles to column (single shear per angle): 4 bolts x 17.9 = 71.6 kip per angle, 2 angles = 143.2 kip.

Beam web governs: 71.6 kip < 85 kip. NOT OK.

Revise: use 5 bolts at 3 in. spacing. 5 x 17.9 = 89.5 kip. 89.5 > 85. OK.

Bolt bearing on beam web

Beam web t_w = 0.335 in., F_u = 65 ksi. Bolt hole = 3/4 + 1/16 = 13/16 in.

Edge bolt: L_c = 1.5 - 13/32 = 1.094 in. phi x R_n = 0.75 x min(1.2 x 1.094 x 0.335 x 65, 1.5 x 0.75 x 0.335 x 65) = 0.75 x min(28.5, 24.5) = 0.75 x 24.5 = 18.4 kip.

Interior bolts (4 bolts): L_c = 3.0 - 13/16 = 2.188 in. phi x R_n = 0.75 x min(1.2 x 2.188 x 0.335 x 65, 1.5 x 0.75 x 0.335 x 65) = 0.75 x min(57.0, 24.5) = 18.4 kip.

Total bearing on beam web: 18.4 + 4 x 18.4 = 92.0 kip > 85. OK.

Bolt bearing on angles

Angle t = 0.375 in., F_u = 58 ksi.

Edge bolt: L_c = 1.5 - 13/32 = 1.094 in. phi x R_n = 0.75 x 1.2 x 1.094 x 0.375 x 58 = 21.4 kip.

Interior bolts: L_c = 2.188 in. (bearing deformation governs). phi x R_n = 0.75 x 1.5 x 0.75 x 0.375 x 58 = 18.4 kip.

Total per angle: 21.4 + 4 x 18.4 = 95.0 kip per angle. Two angles = 190.0 kip. 190.0 kip > 85. OK.

Block shear on beam web

Failure path: vertical shear line along bolt column + horizontal tension line to the cope.

A_gv = (4 x 3.0 + 1.5) x 0.335 = 13.5 x 0.335 = 4.523 in^2. A_nv = 4.523 - 4.5 x (13/16 + 1/16) x 0.335 = 4.523 - 4.5 x 0.875 x 0.335 = 4.523 - 1.320 = 3.203 in^2. A_nt = 1.5 x 0.335 - 0.5 x 0.875 x 0.335 = 0.503 - 0.147 = 0.356 in^2.

R_n = 0.75 x min(0.6 x 65 x 3.203 + 1.0 x 65 x 0.356, 0.6 x 50 x 4.523 + 1.0 x 65 x 0.356) = 0.75 x min(124.9 + 23.1, 135.7 + 23.1) = 0.75 x min(148.0, 158.8) = 0.75 x 148.0 = 111.0 kip > 85. OK.

Block shear on angles

Failure path along bolt column on the outstanding leg.

A_gv = (4 x 3.0 + 1.5) x 0.375 = 13.5 x 0.375 = 5.063 in^2. A_nv = 5.063 - 4.5 x 0.875 x 0.375 = 5.063 - 1.477 = 3.586 in^2. A_nt = 1.5 x 0.375 - 0.5 x 0.875 x 0.375 = 0.563 - 0.164 = 0.399 in^2.

R_n per angle = 0.75 x min(0.6 x 58 x 3.586 + 1.0 x 58 x 0.399, 0.6 x 36 x 5.063 + 1.0 x 58 x 0.399) = 0.75 x min(124.8 + 23.1, 109.4 + 23.1) = 0.75 x min(147.9, 132.5) = 0.75 x 132.5 = 99.4 kip per angle. Two angles = 198.8 kip.

198.8 kip > 85. OK.

Summary

All limit states pass with 5 bolts. The governing limit state is bolt shear through the beam web at 89.5 kip (gives a utilization ratio of 85/89.5 = 0.95). This is a tight design — consider using 7/8 in. A325-N bolts for additional reserve if the beam reaction may increase.

Common mistakes to avoid

• Skipping the bearing/tearout check — many engineers check bolt shear but forget to verify bearing on the connected plates. For thin plates or short edge distances, bearing/tearout often governs and can reduce the bolt group capacity by 30-50%.
• Not checking block shear on the beam web — block shear at coped beams is frequently the controlling limit state. The failure plane runs along the bolt line vertically and horizontally along the cope cut. Omitting this check can lead to a brittle tearing failure.
• Using the wrong F_u for bearing — bearing strength depends on F_u of the connected material, not the bolt. If the plate is A36 (F_u = 58 ksi) but the beam web is A992 (F_u = 65 ksi), use the lower value at each interface.
• Ignoring eccentricity on single-plate connections — standard shear tabs have an eccentricity between the bolt line and the weld line. For conventional configurations (AISC Manual Table 10-10 limits), this eccentricity can be neglected. Outside those limits, the eccentricity must be included.
• Not verifying column web capacity — the column web at beam connections must resist the concentrated beam reaction. For deep beams with heavy reactions framing into light column webs, stiffeners or doubler plates may be required.
• Forgetting prying action on tension connections — any bolt loaded in tension through a flexible plate can develop prying forces that increase the bolt demand by 20-50%. Always check prying for moment connections, bracing connections, and hanger connections.
• Mixing up single and double shear — a bolt through a single-plate shear tab is in single shear. A bolt through a double-angle connection engages two shear planes (one per angle). Using double-shear capacity for a single-shear condition overestimates the connection strength by a factor of two.

Cost optimization tips

Connection design involves trade-offs between material cost, fabrication labor, and erection time. The following tips can reduce cost without compromising safety.

Frequently asked questions

What order should I check limit states?

Check limit states in order of how commonly they govern. For simple shear connections: (1) bolt shear, (2) bolt bearing and tearout, (3) block shear rupture, (4) plate yielding and rupture, (5) weld shear, (6) supporting member checks. This order lets you discover capacity shortfalls early, before investing time in less likely checks. If bolt shear fails, you know immediately that you need more bolts or larger bolts — no need to proceed with bearing or block shear until the bolt count is revised.

When does block shear govern?

Block shear typically governs when the connected element is thin (web of a light beam, thin gusset plate) and the bolt pattern is tight (small edge distance, close spacing). Coped beam ends are especially susceptible because the cope removes material from the failure path. Block shear also governs in gusset plates with many bolts in a compact pattern, where the shear rupture area is limited. For thicker elements (1/2 in. plate and heavier), bolt shear or bearing usually governs instead.

How do I size a shear tab?

Start by determining R_u from the beam end reaction. Select 3/4 in. A325-N bolts as a first trial (17.9 kip per bolt in single shear). Calculate the number of bolts: n = ceil(R_u / 17.9). Set the bolt spacing at 3 in. (standard) and the edge distance at 1.5 in. The plate length is (n-1) x 3 + 2 x 1.5. Use a plate thickness of 3/8 in. for reactions up to about 50 kip, or 1/2 in. for reactions up to about 100 kip. Size the fillet weld to match the plate capacity. Then verify all limit states per the checklist above. If any check fails, increase bolt count, plate thickness, or weld size as needed.

What is prying action?

Prying action is an additional force developed in bolts when a flexible connecting element (plate, angle leg) deforms under tension. As the plate bends, the edges contact the support surface and push against it, creating a lever effect that adds extra tension to the bolts beyond the applied force. Prying is most significant in moment connections (flange plates in tension), angle hangers, and end-plate connections. It is mitigated by using thicker plates, placing bolts closer to the support point, or using stiffer connection elements.

When do I need stiffeners?

Stiffeners are required when the concentrated force from a beam connection exceeds the available strength of the column web. Check web local yielding (J10.2), web local crippling (J10.3), and web sidesway buckling (J10.4). Transverse stiffeners or doubler plates are needed if any of these checks fail. Stiffeners are also required for moment connections when the beam flange force causes excessive flange local bending on the column (J10.1). As a rule of thumb, expect stiffeners when a heavy beam frames into a relatively light column — for example, a W24 beam framing into a W12 column.

How many bolts do I need for a 50 kip reaction?

For a simple shear connection using 3/4 in. A325-N bolts: each bolt provides 17.9 kip in single shear. Number of bolts = ceil(50 / 17.9) = 3 bolts. However, you must also check bearing, tearout, and block shear. For a 3/8 in. plate with 1.5 in. edge distance and 3 in. spacing, bearing typically provides about 18-21 kip per bolt, so 3 bolts in bearing gives 54-63 kip. Block shear on the beam web may govern for thinner webs. In most standard configurations, 3 bolts are adequate for a 50 kip reaction, but always verify all limit states.

Run this calculation

• Section Properties Database
• Beam Calculator

Related references

• Steel Connection Design
• Bolt Capacity Table
• Bolt Bearing and Tearout
• Connection Types
• Eccentric Connections
• Steel Fasteners
• AISC Bolt Hole Sizes
• Welded Connections
• Column Base Plate
• How to Verify Calculations
• Connection Limit State Checks
• steel connection capacity calculator
• weld capacity for connection design
• Bolted Connections
• Fastener Reference

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 the use of this information.

Design Resources

Calculator tools

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• Fin Plate Shear Connection Calculator
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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

• Shear Tab