--------------------- | :----------------------- | :---------------------------- | :------- | | End bearing (milled) | Contact + nominal bolts | Compression columns, W-shapes | Low | | Full bolted flange plates | Bolts in shear/bearing | Tension or moment columns | Moderate | | Full welded (CJP) | Weld matching base metal | Heavy columns, seismic | High | | Partial bearing + plates | Combined bearing + bolts | Variable compression/tension | Moderate |

End Bearing Requirement

Per CSA S16 Clause 13.3.2, where columns are finished to bear at splices (milled ends), the splice must:

1. Transmit not less than 50% of the design compressive force through bearing contact
2. Have sufficient bolts or welds to hold connected parts in place (erection loads)
3. Maintain alignment during and after construction

End Bearing Column Splice

The most common column splice for multi-storey buildings. The column ends are milled flat so that compressive force transfers directly through bearing contact. Bolting is nominal — primarily to resist erection loads and incidental tension.

Milled Bearing Surface Requirements

Nominal Bolting for End Bearing Splices

Per CSA S16 Clause 13.3.3, the nominal bolting must resist:

1. Erection loads: Not less than 2% of the column compressive capacity as a lateral force
2. Wind during erection: Consider temporary bracing requirements per CSA S16 Clause 29
3. Accidental eccentricity: 25 mm eccentricity applied at splice location

Minimum bolts: 4 bolts in each flange (2 each side of joint) and 2 bolts in the web.

Splice Plate Sizing for End Bearing

Plate length includes bolt edge distances. Plates are typically shop-attached to the upper column and field-bolted to the lower column.

Full Bolted Column Splice

When the column is subject to tension or significant moment, full bolted flange splices are required. The design follows the same principle as beam flange splices.

Design Forces

Bolted Flange Plate Check

Tr_plate = 0.90 × Ag × Fy ≥ Pf (flange force)

Pf = Cf/2 + Mf/(d - tf) (for combined axial + bending)

For W310×158 column with Cf = 4,000 kN and negligible moment: Pf per flange = 4,000 / 2 = 2,000 kN Tr required: Ag ≥ 2,000 × 1000 / (0.90 × 350) = 6,349 mm^2 With 260 mm wide plate: t ≥ 6,349 / 260 = 24.4 mm → use 25 mm plate.

Alignment and Erection Tolerances

Per CSA S16 Clause 29.3 and CSA A23.1 (concrete tolerance coordination):

Erection Aids

Per good practice:

• Drift pins: Used to align bolt holes during erection — maximum drift 2 mm
• Temporary bolts: 25% of holes filled with snug-tight bolts before lifting crane load
• Levelling nuts: Used under base plates, NOT at column splices (milled bearing makes levelling nuts unnecessary at splices)

Worked Example — W310×158 Column Splice, 6-Storey Building

Given: W310×158 column (350W). Storey height = 3.8 m. Factored axial load at splice: Cf = 4,000 kN (compression only). Splice at mid-storey (ease of access). End bearing specified.

Step 1 — Check Bearing Stress: Column area A = 20,100 mm^2 (W310×158) Bearing stress: fb = 4,000 × 1000 / 20,100 = 199 MPa 0.75 × Fy = 0.75 × 350 = 262.5 MPa > 199 MPa. Bearing OK.

Step 2 — Nominal Flange Plates: Flange width = 310 mm, flange thickness = 25.0 mm Use 260 mm wide × 20 mm splice plates (2 per flange, one each side). Flange force (2% erection) = 0.02 × 4,000 = 80 kN per flange Tr_plate = 0.90 × 260 × 20 × 350 / 1000 = 1,638 kN >> 80 kN. OK for erection.

Step 3 — Bolts (nominal): 4 M20 A325M bolts per flange (2 each side). Vr per bolt (single shear, bearing type) = 0.60 × 0.70 × 825 × 314 / 1000 = 108.8 kN Bolt group capacity = 4 × 108.8 = 435 kN > 80 kN. OK.

Step 4 — Web Plate: 140 mm wide × 10 mm plate. 2 M20 bolts in web. Web shear (2% erection lateral) = 0.02 × 4,000 = 80 kN Tr_web = 0.90 × 0.66 × 350 × 140 × 10 / 1000 = 291 kN > 80 kN. OK.

Step 5 — Alignment Check: Storey height 3.8 m → plumb tolerance = 3800/500 = 7.6 mm Cumulative over 6 storeys (22.8 m) → 22800/500 = 45.6 mm < 50 mm limit. OK.

Result: W310×158 end bearing splice with 260×20 flange plates and 140×10 web plate. 8-M20 A325M bolts. All erection and alignment checks satisfied per CSA S16:24.

Frequently Asked Questions

When can I use a simple end bearing column splice? End bearing splices are appropriate when the column is in pure compression and the column ends can be milled flat in the shop. They are the most economical splice type for multi-storey buildings where columns are sized to resist compression only and moments are negligible at the splice location. Per CSA S16 Clause 13.3.2, the milled surfaces must be in full contact and the splice must transfer at least 50% of the compressive force through bearing.

What is the minimum number of bolts in a column splice? Per CSA S16 Clause 13.3.3 and common industry practice, the minimum is 4 bolts per flange (2 on each side of the joint) and 2 bolts in the web — totalling at least 10 bolts per column splice. These bolts resist erection loads (minimum 2% of column capacity laterally) and any accidental eccentricity during construction. For tension or moment splices, the number of bolts is determined by strength calculations, which typically requires significantly more bolts.

How are column splices handled in seismic force-resisting systems? For columns in SFRS (seismic force-resisting systems), per CSA S16 Clause 27, column splices must develop the full capacity of the smaller column section or the seismic force with overstrength, whichever is larger. Slip-critical bolts are required if the connection is subject to load reversal. The splice should be located outside of the plastic hinge zone — typically at mid-storey height or further. For MD and LD frames, capacity design principles apply, meaning the splice must develop 1.25× the column factored resistance.

What is the difference between milled-to-bear and non-machined column ends? Milled-to-bear column ends are machined flat in the fabrication shop to ensure full contact across the cross-section. This permits direct transfer of compressive force through bearing, requiring only nominal bolting for erection loads. Non-machined ends rely entirely on splice plates and bolts to transfer forces, requiring full-strength connections. The cost difference: milled bearing splices use approximately 60-70% fewer bolts than non-machined splices for the same compressive load.

Related Pages

• CSA S16 Column Design Guide
• CSA S16 Column K-Factor Reference
• CSA S16 Bolt Design Guide
• CSA S16 Base Plate Design
• CSA S16 Beam Splice Guide
• Column Capacity Calculator
• All Canadian References

This page is for educational reference. Column splice design per CSA S16:24 Clause 13.3 and CSA W59 welding requirements. Verify end bearing contact, alignment tolerances, and seismic splice requirements with project structural engineer. Results are PRELIMINARY — NOT FOR CONSTRUCTION without independent PE/SE verification.

Design Resources

Calculator tools

• Column Capacity Calculator
• Base Plate Design Calculator
• Bolted Connection Calculator
• Weld Capacity Calculator
• Beam Capacity Calculator

Design guides

• Bolted Connection Worked Example
• Bolted Connection Checklist
• How to Verify Calculations
• Steel Connection Calculator Guide
• Weld Design Checklist

Reference pages

• CA Base Plate Worked Example
• CA Column Capacity Guide
• CA Seismic Design Guide