path: /blog/steel-beam-splice-design/ canonical: https://steelcalculator.app/blog/steel-beam-splice-design/ meta_title: 'Steel Beam Splice Design -- Bolted & Welded Splices per AISC 360 (2026)' meta_description: 'Steel beam splice design guide: bolted flange and web plate splices, welded end-plate splices. Complete AISC 360-22 worked example with bolt shear, bearing, block shear, and flange force transfer checks.' robots: 'index,follow' lastmod: '2026-05-20' schema_file: 'schema/blog_steel-beam-splice-design.json' FAQPage: '@type': 'FAQPage' mainEntity: - '@type': 'Question' 'name': 'When is a steel beam splice required?' 'acceptedAnswer': '@type': 'Answer' 'text': 'Steel beam splices are required when: (1) the beam length exceeds available transport limits (typically 12-15 metres for road transport), (2) construction sequencing requires the beam to be erected in segments, (3) a change in section size is needed along the beam length, or (4) an existing beam is being extended or repaired. Transport is the most common driver -- most beams longer than 12 metres must be spliced.' - '@type': 'Question' 'name': 'What checks are required for a bolted beam splice?' 'acceptedAnswer': '@type': 'Answer' 'text': 'A complete bolted beam splice per AISC 360-22 requires: flange plate design (net section tension, bolt shear, bolt bearing), web plate design (shear yielding, bolt shear, bolt bearing, block shear), and combined action verification. The flange splice plates must transfer the flange force (moment divided by beam depth), and the web splice plates must transfer the total shear force plus any portion of the moment assigned to the web.' - '@type': 'Question' 'name': 'What is the difference between a bearing splice and a slip-critical splice?' 'acceptedAnswer': '@type': 'Answer' 'text': 'A bearing splice transfers force through bolt bearing against the plate edge. It is the standard design for most static applications. A slip-critical splice is pre-tensioned to prevent slip at the faying surfaces and is required for: (1) connections subject to fatigue or load reversal, (2) oversized or slotted holes parallel to the load direction, (3) connections where slip would impair structural performance, and (4) most seismic applications per AISC 341. Slip-critical splices require faying surface preparation and bolt pre-tensioning per RCSC specifications.' - '@type': 'Question' 'name': 'Where should a beam splice be located along the span?' 'acceptedAnswer': '@type': 'Answer' 'text': 'Beam splices should be located away from points of maximum moment and maximum shear. Ideal splice locations are at approximately one-quarter to one-third of the span from the support, where both moment and shear are moderate. Avoid splicing at mid-span (maximum moment) and at supports (maximum shear). AISC does not mandate a specific location, but locating splices at quarter-points is standard practice and typically results in the most economical splice design.'

Steel Beam Splice Design -- Bolted & Welded Splices per AISC 360

Every steel beam longer than a truck bed needs a splice. Transport limits, construction staging, and section changes all drive splice requirements. A properly designed beam splice must transfer moment, shear, and axial force (if present) across the joint without creating a weak point in the structure. This guide covers bolted flange-plate splices, bolted web-plate splices, and welded end-plate splices with a complete worked example per AISC 360-22.

PRELIMINARY -- NOT FOR CONSTRUCTION. All examples are educational references only. Every structural design must be independently verified by a licensed Professional Engineer before use in any project.

Why beam splices exist

Steel beams are fabricated in mills and shipped to site. The practical limits are:

For a 24-metre beam, splicing at quarter-points creates three 8-metre segments -- well within transport limits and easily managed by a standard mobile crane.

Splice design philosophy -- transfer all forces

The fundamental rule of splice design: every internal force at the splice location must be transferred across the joint. For a beam in bending and shear, this means:

1. Flange force transfer: The tension and compression forces in the flanges (M/d, where d = beam depth between flange centroids) must be transferred through the flange splice plates and their bolts
2. Web shear transfer: The shear force V must be transferred through the web splice plates and their bolts
3. Moment in the web: The web resists a portion of the applied moment (approximately M * Aw/A_total for compact sections). This web moment must be transferred through the web splice plates as a force couple
4. Stiffness continuity: The splice plates and bolt group must provide stiffness comparable to the continuous beam to avoid a soft spot that attracts deformation

Bolted flange-plate splice -- the workhorse

The most common beam splice consists of:

• Two flange splice plates (one top, one bottom), each bolted to both beam segments
• Two web splice plates (one each side), each bolted to both beam segments
• Bolt groups sized to transfer flange force (flange plates) and shear force (web plates)

Step-by-step design procedure

Given: W610x125 beam (A992, Fy = 345 MPa), splice at quarter-span. M = 580 kN-m, V = 245 kN. No axial force. Splice plates: A36 steel (Fy = 250 MPa, Fu = 400 MPa). Bolts: M22 A325M (Fnv = 415 MPa for shear plane through threads).

Beam properties: d = 612 mm, bf = 229 mm, tf = 19.6 mm, tw = 11.9 mm. Flange centroid distance d_flange = d - tf = 612 - 19.6 = 592.4 mm.

Check 1: Flange force

Flange force = M / d_flange = 580,000 / 592.4 = 979 kN per flange.

Flange gross area Af = bf _ tf = 229 _ 19.6 = 4488 mm^2. Flange yield strength = phi _ Fy _ Af = 0.90 _ 345 _ 4488 / 1000 = 1393 kN >> 979 kN. Flange splice plates must develop at minimum this 979 kN.

Check 2: Flange splice plate design

Use two flange splice plates, each 220 mm wide x 16 mm thick (A36).

Gross area per plate: Ag = 220 * 16 = 3520 mm^2. Two plates: 7040 mm^2. Net area (2 bolt holes, dh = 24 mm): An = (220 - 2*24) _ 16 _ 2 = 172 _ 16 _ 2 = 5504 mm^2.

Tension yielding: phi _ Fy _ Ag = 0.90 _ 250 _ 7040 / 1000 = 1584 kN > 979 kN. OK. Tension rupture: phi _ Fu _ An = 0.75 _ 400 _ 5504 / 1000 = 1651 kN > 979 kN. OK.

Bolt shear: M22 A325M, single shear, threads in shear plane. Ab = pi _ 22^2 / 4 = 380 mm^2. Rn_per_bolt = Fnv _ Ab = 415 _ 380 / 1000 = 157.7 kN. phi _ Rn = 0.75 * 157.7 = 118.3 kN.

Number of bolts required per flange = 979 / 118.3 = 8.3. Use 10 bolts (2 rows of 5).

Bolt bearing (flange plate, t = 16 mm, Fu = 400 MPa): For edge bolts (Le = 40 mm): Lc = 40 - 24/2 = 28 mm. Rn*edge = 1.2 * Lc _ t _ Fu = 1.2 _ 28 _ 16 _ 400 / 1000 = 215 kN. phi _ Rn = 0.75 _ 215 = 161 kN > 97.9 kN per bolt (979/10). OK.

For interior bolts (s = 70 mm): Lc = 70 - 24 = 46 mm. Rn*int = 1.2 * 46 _ 16 _ 400 / 1000 = 353 kN, but limited to 2.4 _ d _ t _ Fu = 2.4 _ 22 _ 16 _ 400 / 1000 = 338 kN. phi _ Rn = 0.75 * 338 = 253 kN > 97.9 kN. OK.

Check 3: Web splice plate design

Web shear V = 245 kN must be transferred through the web splice plates.

Use two web splice plates, each 400 mm wide x 10 mm thick (A36). Height to match the flat portion of the web (d - 2tf - 2fillet_radius). Approximate available web height = 612 - 219.6 - 2*20 = 533 mm. Use plate height = 480 mm to clear the flange fillet.

Web splice plate shear area (two plates): Agv = 2 _ 480 _ 10 = 9600 mm^2. Shear yielding: phi _ 0.6 _ Fy _ Agv = 0.90 _ 0.6 _ 250 _ 9600 / 1000 = 1296 kN >> 245 kN. OK.

Bolt shear (web plates): Use M20 A325M bolts (Fnv = 415 MPa). Ab = pi _ 20^2 / 4 = 314 mm^2. Rn_per_bolt = 415 _ 314 / 1000 = 130.3 kN. phi _ Rn = 0.75 _ 130.3 = 97.7 kN.

Bolts in double shear (web plate each side): capacity per bolt = 2 * 97.7 = 195.4 kN. Number of bolts required = 245 / 195.4 = 1.3 per side. Minimum practical: 6 bolts (3 rows of 2, staggered).

But also check the eccentricity moment on the bolt group. The shear is applied at the splice centreline but the bolt group centroid may be offset. For a symmetric bolt group with the load through the centroid, the eccentricity moment is zero. With 6 bolts minimum, bolt utilisation is very low (245 / (6 * 195.4) = 0.21).

Block shear (web splice plate, edge distance 40 mm, pitch 80 mm, 3 rows of 2 bolts):

Agv = 2 _ (40 + 80 + 80) _ 10 = 2 _ 200 _ 10 = 4000 mm^2. Anv = 4000 - 2 _ 2.5 _ 22 _ 10 = 4000 - 1100 = 2900 mm^2. Ant = 2 _ (60 - 0.5*22) * 10 = 2 _ 49 _ 10 = 980 mm^2.

Rn = 0.6 _ Fu _ Anv + Ubs _ Fu _ Ant = 0.6 _ 400 _ 2900 / 1000 + 1.0 _ 400 _ 980 / 1000 = 696 + 392 = 1088 kN. Upper limit: 0.6 _ Fy _ Agv + Ubs _ Fu _ Ant = 0.6 _ 250 _ 4000 / 1000 + 392 = 600 + 392 = 992 kN. Rn = 992 kN. phi _ Rn = 0.75 _ 992 = 744 kN >> 245 kN. Block shear is not critical for web plates.

Welded beam splice

For shop-welded splices (fabricated before delivery) or site-welded splices with qualified procedures, a full-penetration groove weld (CJP) provides 100% of the base metal capacity. The design check reduces to:

• CJP weld: Develops the full strength of the connected part. No separate weld strength calculation is required per AISC 360 J2.1(a), provided matching weld metal is used and the weld is made in accordance with AWS D1.1.
• Partial-joint-penetration (PJP) weld: Requires calculation of effective throat per Table J2.1. May be used when the flange force is less than the full flange capacity.

For site work, bolted splices are strongly preferred over welded splices because:

• Bolting does not require pre-heating, welding equipment, or weather protection
• Bolt tension can be verified with a torque wrench; weld quality requires NDT (ultrasonic or radiographic)
• Bolted splices are faster to erect (no cooling time, no multi-pass welding)
• Site welding of full-penetration flange welds is expensive and difficult to inspect

End-plate splice -- an alternative

A beam end-plate splice uses a welded end plate on each beam segment, bolted together face-to-face. This is essentially a bolted moment end-plate connection where both sides are beams rather than a beam and a column.

Advantages:

• All fabrication is shop-welded (end plates to beams)
• Site work is bolting only (no field welding, no splice plates to align)
• More compact than flange + web plate splices

Disadvantages:

• Requires accurate fabrication (end plates must be square and flush)
• Bolt group design is more complex (prying action, combined tension and shear in bolts)
• More expensive in material (thick end plates) than plate splices

Design is per the AISC moment end-plate procedure (AISC Design Guide 16 or the equivalent EN 1993-1-8 component method), replacing the column side with a second beam.

Code comparison -- splice design across international standards

The flange force approach (M/d) is common across all codes. The EN 1993 component method provides a more refined distribution for joints where the moment is shared non-uniformly between flanges and web, but for standard beam splices away from moment connections, M/d is adequate.

Splice location optimisation

The optimal splice location balances:

1. Transport length: Keep segments under the maximum transportable length
2. Lifting weight: Keep each segment within crane capacity at the required radius
3. Moment and shear at splice: Lower forces mean smaller, cheaper splice plates and fewer bolts
4. Erection sequence: Splice should be accessible to ironworkers (not buried inside a wall or between closely spaced beams)
5. Stability during erection: Each segment must be stable when lifted individually (temporary bracing may be needed)

Rule of thumb: Splice at quarter-points. Moment at L/4 is approximately 75% of mid-span moment for a simply supported beam under uniform load, and shear is half the end reaction. These moderate forces typically result in plate thicknesses of 12-20 mm and bolt counts of 6-12 per flange -- practical and economical.

Column splice considerations

Column splices are similar to beam splices with two additional concerns:

1. Axial force dominant: Column splices primarily transfer axial compression. The splice must prevent the upper column from displacing laterally relative to the lower column (stability and alignment).
2. Moment continuity in moment frames: Spliced columns in moment frames must develop the full plastic moment of the smaller column section to maintain frame ductility under seismic loading per AISC 341.

For compression-dominant column splices, bearing of the milled column ends can transfer a large portion of the axial force directly (AISC 360 J1.4 permits bearing splices for compression). Flange and web splice plates then only need to transfer the tension component (from uplift or moment reversal) and provide lateral alignment.

Common design mistakes in beam splices

1. Using gross flange force without including the web moment share: If the web resists 15% of the total moment, the flange force is 15% less than M/d. Ignoring this is conservative for the flange splice but may underestimate the required web splice capacity.
2. Neglecting prying action in flange splice plates: Thin splice plates with bolts close to the flange edge are susceptible to prying, which increases bolt tension beyond the applied flange force.
3. Using bearing bolts for fatigue applications: Splices in crane runway beams, bridge girders, and dynamically loaded structures require slip-critical bolts or welded splices. Bearing bolts in these applications will loosen over time.
4. Insufficient edge distance in web splice plates: The standard minimum edge distance of 1.5d from the centre of a standard hole to the plate edge applies. In narrow web plates, 1.5d can be hard to achieve, especially with staggered bolt patterns.
5. Forgetting to check beam web bearing and block shear: The beam web at the splice bolts must also be checked for bearing and block shear -- the splice plates may be adequate but the beam web, which may be thinner than the splice plates, could govern.
6. Ignoring erection tolerances: Bolted splices require clearance for bolt insertion (typically 2 mm oversize holes). The detailing must allow for mill tolerances on beam straightness and splice plate flatness. Overly tight tolerances create field fit-up problems.

Frequently Asked Questions

Do I need to design for the full beam capacity at the splice or just the applied forces? Per AISC 360, splices should develop the greater of the applied factored forces and 50% of the section capacity (for flexural members in typical building applications). For seismic applications (AISC 341), splices may need to develop the full plastic moment capacity of the connected section.

Can I use one-sided splice plates instead of two-sided? One-sided splice plates introduce eccentricity that creates a moment in the bolt group. This reduces bolt capacity and should be accounted for. Two-sided (double) splice plates are standard practice because they eliminate eccentricity and provide symmetric load transfer.

What bolt grade should I use for beam splices? A325 (A325M) bolts are standard for building splices. A490 (A490M) bolts provide higher strength but are less ductile and may be restricted in seismic applications. For most building applications, A325M M20 or M22 bolts are adequate and economical.

How do I detail the splice for fire protection? The splice plates add thickness locally, which must be accounted for in the fireproofing thickness. Spray-applied fireproofing and intumescent coatings can bridge the splice plate transition zones. Board fireproofing may require a box-out detail at bolted splice locations.

Should the splice bolts be pre-tensioned? Bearing bolts in standard beam splices do not require pre-tensioning (snug-tight is sufficient). Pre-tensioned bolts (fully tensioned per RCSC) are required for: slip-critical connections, connections subject to direct tension, and connections in structures where bolt loosening would impair serviceability.

Run These Calculations

Bolted Connection Calculator -- Complete bolt group design: shear, bearing, tension, combined loading, and block shear per AISC 360, AS 4100, EN 1993, and CSA S16.

Welded Connection Calculator -- Fillet and groove weld capacity per AISC 360 J2.4 with directional strength enhancement and base metal checks.

Beam Capacity Calculator -- W-shape moment, shear, LTB, and deflection checks per AISC 360.

Column Capacity Calculator -- Axial compression and buckling per AISC 360 Chapter E.

Section Properties Database -- Browse 500+ W, HSS, C, L, and WT sections with dimensions, Ix, Sx, Zx, ry, J, Cw, and classification limits per AISC 360.

Further reading

• Steel Beam Design Example -- AISC 360-22 LRFD Worked Solution
• Steel Column Design Example -- AISC 360-22 LRFD Worked Solution
• Steel Connection Design Spreadsheet -- Free Online Alternative
• AISC 360 Design Examples -- Beam, Column & Connection Worked Solutions
• Moment of Inertia Calculator for Steel Sections -- Ix, Iy, J
• How to Read Steel Section Tables -- W, HSS, C, L Properties Decoded
• EN 1993 Steel Connections -- Eurocode 3 Design Guide
• AS 4100 Bolt Group Design -- M20 8.8 Worked Example
• AS 4100 Fillet Weld Design -- SP/GP Worked Example
• CSA S16 Base Plate Design -- Canadian Steel Standard
• Steel Fy and Fu Reference -- Yield and Tensile Strength by Grade
• AISC Bolted Shear Tab Example -- Verification Walkthrough
• AISC Connection Design Reference -- J3.6 and J3.10

Educational reference only. All splice designs must be independently verified by a licensed Professional Engineer. Verify all designs against the current edition of the governing design code. Results are PRELIMINARY -- NOT FOR CONSTRUCTION.