Steel Column Splice — Design Guide per AISC 360, EN 1993
Column splices transfer axial load, shear, and sometimes moment between stacked column sections. This guide covers bolted and welded splice design per AISC 360 and EN 1993-1-8.
Quick links: Column buckling → | Base plates → | Bolted connections →
Core calculations run via WebAssembly in your browser with step-by-step derivations across AISC 360, AS 4100, EN 1993, and CSA S16 design codes. Results are preliminary and must be verified by a licensed engineer.
Frequently Asked Questions
What is the difference between bearing and non-bearing splices? Bearing splices transfer axial load through direct contact between column ends — the ends must be milled to bear fully (AISC 360 J1.4). Bearing splices require only enough bolts/welds for stability during erection and to resist 50% of the moment. Non-bearing splices transfer all loads through the splice plates and bolts/welds, requiring the splice to develop the full column strength. Per AISC J1.4, ends of bearing splices must be finished to bear and the splice designed for 50% of the moment from the connected member.
Where are column splices typically located? Column splices are typically located 4 ft (1.2 m) above the floor level — high enough for convenient access for bolting/welding, low enough that the crane can handle the column piece. Splices should be located where the moment is low (near inflection points in moment frames). Per AISC Code of Standard Practice Section 6.4.2, standard column shipping lengths are limited to 60-70 ft (18-21 m) due to trucking constraints.
How are bolted column splices designed? A bolted column splice design procedure: (1) Determine forces — axial load, shear, and moment at the splice location from the structural analysis. (2) Check bearing — if ends are milled, 100% of axial compression can transfer through bearing; otherwise the splice must carry 100% of the load. (3) Design bolts for combined shear and axial tension per AISC 360 J3-7 or J3-3a. (4) Check filler plates per J5.5 when beam flanges differ by more than 1/8 inch. (5) Design splice plates for full member strength per J1.2.
How are welded column splices designed? Welded column splices are commonly used when bolting access is restricted or when full moment continuity is required. Per AWS D1.1 Clause 7 and AISC 360 Chapter J: (1) Complete joint penetration (CJP) groove welds at the column flanges — required for moment frame columns where the splice must develop the full flexural strength of the member. The weld is sized equal to the flange thickness (typically 1/2 to 1-1/2 inches for W14 columns). (2) Minimum weld access hole per AWS D1.1 Figure 7.2 — required when welding the lower column to the upper column, with 2 inch minimum length × 1 inch depth typical for rolled sections. (3) Web weld — shear transfer through the web typically uses fillet welds on both sides of the web plate. For a W14×90 column (Fy = 50 ksi): shear capacity from web φVn = 0.9 × 0.6 × 50 × (14 × 0.44) = 166 kips. Fillet weld required: D = V/(1.392 × Lw × 0.707) = 166,000/(1.392 × 14 × 2) = 4,260 — approximately 5/16 inch fillet weld each side. (4) Backing bars — ceramic or steel backing bars for CJP welds per AWS D1.1 Clause 7.9. Steel backing bars must match the base metal strength and be left in place or removed per the contract documents. (5) Welding sequence — to minimize distortion, weld the flanges alternately, completing the first flange weld before starting the second. Preheat per AWS D1.1 Table 5.3: minimum 50°F for 1/2 inch thickness at 50°F ambient, increasing to 150°F for 2 inch thickness.
Splice Plate Design with Worked Example
A fully detailed design example illustrates the complete procedure for a bolted column splice.
Problem statement. Design a bolted bearing-type splice for a W14×90 column (A992, Fy = 50 ksi, Fu = 65 ksi) below to a W12×65 column above. The splice must resist Pu = 400 kips compression (factored), Vu = 25 kips shear, and Mu = 100 kip-ft moment from second-order analysis. Column shipping length: 40 ft pieces each side of the splice.
Step 1 — Determine load distribution. Per AISC 360 J1.4, since the column ends are not milled for full bearing (field splice), the splice must resist 100% of the loads. AISC also requires minimum 50% of the moment to be resisted by the splice even for bearing-type splices. Therefore: M_design = max(100, 0.5 × Mu_adjacent) = max(100, 0.5 × 180) = 100 kip-ft.
Step 2 — Calculate flange forces from moment. For the W14×90 (d = 14.0 in, bf = 14.5 in, tf = 0.71 in): T_flange = M/d_eff = (100 × 12)/13.3 = 90.2 kips tension in one flange, compression in the other. The smaller W12×65 above (d = 12.1 in) gives: T_flange = (100 × 12)/11.5 = 104.3 kips (controls).
Step 3 — Design flange splice plates. Use 1/2 inch thick plates (Fy = 36 ksi) on each side of flange. Required plate width: b_pl = (14.5 - 1)/2 = 6.75 inches (allow 0.5 inch gap between plates for bolting access). Check tension yield: φRn = 0.9 × 36 × 6.75 × 0.5 × 2 plates = 218.7 kips > 104.3 kips — OK. Check tension rupture: φRn = 0.75 × 58 × 6.75 × 0.5 × 2 = 293.6 kips — OK.
Step 4 — Design bolts. Use 7/8 inch A325-N bolts in standard holes (φRn_bolt = 21.6 kips/bolt in single shear, 43.2 kips in double shear). For flange connection: n = 104.3/21.6 = 4.8 → use 6 bolts (3 rows × 2 columns) per flange plate. Spacing: 3 inches between bolts (min 2-2/3d = 2.33 inches per J3.3), edge distance 1.5 inches (min 1.25 inches per Table J3.4). Check bolt bearing on 1/2 inch plate: φRn = 0.75 × 1.5 × 1.0 × 58 × 0.5 × 3 = 97.9 kips > 21.6 kips — OK.
Step 5 — Design web splice. Shear per web: Vu = 25 kips. Use 3/4 inch A325-N bolts (φRn = 15.9 kips/bolt in single shear). n = 25/15.9 = 1.6 → use 2 bolts (single row each side of splice). Web splice plates: 1/4 inch × 4 inch each side (A36). Check shear yield: φRn = 0.9 × 0.6 × 36 × 0.25 × 4 × 2 = 38.9 kips > 25 kips — OK.
Step 6 — Check block shear on flange plate. For 6 bolts in pattern (3 rows × 2 columns): Agv = 2 × (3 × 3 + 1.5) × 0.5 = 10.5 in², Anv = 10.5 - 6 × 1.0 × 0.5 = 7.5 in² (1.0 inch = 7/8 + 1/8 for damage zone). Ant = 2 × (1.5 - 0.5 × 1.0) × 0.5 = 1.0 in². φRn = 0.75 × (0.6 × 58 × 7.5 + 0.6 × 58 × 1.0) = 0.75 × (261 + 34.8) = 221.9 kips > 104.3 kips — OK.
Step 7 — Check filler plates. The W14×90 flange thickness (0.71 in) differs from the W12×65 flange thickness (0.61 in) by 0.10 in < 1/8 in — no filler plate required per J5.5.
Erection Stability and Temporary Conditions
During steel erection, column splices are subjected to temporary loads before the permanent structure is complete. Per AISC COSP Section 7.13 and OSHA 1926.755: (1) Minimum 4 bolts must be installed and tightened at each column splice before releasing the crane. The bolts should be tensioned to at least 50% of pretension (snug-tight) for bearing connections. (2) Plumbness tolerance: L/500 or 2 inches max deviation from vertical. For a 60 ft column, this means maximum 1.44 inches out of plumb. (3) Wind loading during erection: per ASCE 37-14, a minimum construction wind load of 10 psf is applied to the projected area of the frame. For a 60 ft × 60 ft bay at 10 psf: total lateral load = 36 kips, which must be resisted by temporary guys or permanent bracing. (4) Temporary guys: 1/2 inch diameter cable (minimum breaking strength 14.5 kips per ASTM A603) at 45° angle, connected to deadman anchors or adjacent permanent structure.
Use the column buckling calculator to verify column stability for the 40 ft unbraced length during erection, and refer to the connection checklist for field verification of splice bolt installation.
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Disclaimer (educational use only)
This page is provided for general technical information and educational use only. It does not constitute professional engineering advice. All results must be independently verified by a licensed Professional Engineer.