Column Splice Design Worked Example — W12x65 Bearing-Type Bolts per AISC 360-22

Complete step-by-step column splice design for a W12x65 column in a 10-story braced frame. Bearing-type splice with bolted flange plates and web plates. All intermediate calculations shown with actual numbers and AISC 360-22 code references.

Problem Statement

PRELIMINARY — NOT FOR CONSTRUCTION. All results are for educational and reference use only. Must be independently verified by a licensed Professional Engineer (PE) or Structural Engineer (SE) before use in any project.

A W12x65 interior gravity column is spliced between the 4th and 5th floors of a 10-story office building with braced frames. The splice is located 4 ft above the 4th floor finished floor level. The column is ASTM A992 steel (Fy = 50 ksi, Fu = 65 ksi).

Section Properties — W12x65:

Design Forces at Splice (factored, LRFD):

• Factored axial compression: P_u = 420 kips
• Factored weak-axis moment: M_uy = 45 kip-ft
• Factored strong-axis moment: M_ux = 0 kip-ft (assumed zero for gravity column)
• Factored shear: V_u = 8.0 kips

Minimum Axial per AISC B3.6: The column available compressive strength is phi Pn = 719 kips (from column design). Minimum splice design force = 0.50 × 719 = 360 kips. Since P_u = 420 kips > 360 kips, the design is governed by the actual demand. Use P_u = 420 kips.

Step 1: Flange Force Calculation

For a column splice, the axial force plus moment-induced flange forces must be transferred. The flange force for each flange:

P_f = P_u / 2 + M_uy / (d_eff between flanges)

Where the effective lever arm between flange centroids is:

d_eff = d - tf = 12.1 - 0.605 = 11.50 in.

Moment contribution to flange force:

P_f_moment = M_uy × 12 / d_eff = 45 × 12 / 11.50 = 540 / 11.50 = 47.0 kips

Axial contribution per flange:

P_f_axial = P_u / 2 = 420 / 2 = 210 kips

Total flange force (compression side = additive, tension side = subtractive):

P_f_compression = 210 + 47.0 = 257.0 kips (governs for bearing splice — compression flange carries more)
P_f_tension = 210 - 47.0 = 163.0 kips

Since this is a bearing splice, the compression flange force is primarily transferred through mill-to-bear contact between column ends. The splice plates provide alignment and resist the tension flange force. For a non-bearing splice (conservative approach used here), design the flange plates for the full compression flange force P_f = 257 kips.

Step 2: Flange Splice Plate Sizing

Use flange splice plates on the outside faces of both flanges: PL 12 × 3/8 in., ASTM A572 Gr 50 (Fy = 50 ksi, Fu = 65 ksi).

Outer plate properties (per plate):

• Width: b_p = 12.0 in. (matches column flange width)
• Thickness: t_p = 0.375 in.
• Gross area: A_g = 12.0 × 0.375 = 4.500 in.²

Inner splice plates (between column flanges): 2 PL 12 × 3/8 in. (one on each side of web, designed similarly — omitted for brevity but included in the summary).

Step 3: Bolt Configuration

Bolt layout on each flange face: 2 vertical rows of 3 bolts (6 bolts per flange face, 12 total per flange pair including inner and outer plates). Bolts: 3/4 in. dia. ASTM A325N, standard holes (dh = 13/16 in.).

Bolt spacing: 3 in. center-to-center vertically, 4 in. gage between rows (matches W12 flange workable gage). Edge distance: 1.5 in. from plate edges.

Step 4: Flange Plate Tension Yielding (AISC J4.1)

Per outer plate:

R_n = Fy × A_g = 50 × 4.500 = 225.0 kips
phi R_n = 0.90 × 225.0 = 202.5 kips

For outer + inner plates on one flange (4 plates total, but force shared):

Total phi R_n = 2 × 202.5 = 405.0 kips > 257.0 kips. **Tension yielding OK.**

Step 5: Flange Plate Tension Rupture (AISC J4.2)

Hole deduction: dh_eff = 13/16 + 1/16 = 7/8 in. per bolt (AISC B4.3b).

Per outer plate (2 rows, 3 bolts per row across the width = 2 holes per critical section):

A_n = (12.0 - 2 × 7/8) × 0.375 = (12.0 - 1.75) × 0.375 = 10.25 × 0.375 = 3.844 in.²
A_e = U × A_n = 1.0 × 3.844 = 3.844 in.² (U = 1.0, all elements connected)

R_n = Fu × A_e = 65 × 3.844 = 249.9 kips
phi R_n = 0.75 × 249.9 = 187.4 kips per outer plate

For outer + inner plates:

Total phi R_n = 2 × 187.4 = 374.8 kips > 257.0 kips. **Tension rupture OK.**

Step 6: Flange Bolt Shear Check (AISC J3.6)

6 bolts per flange face (2 rows × 3 bolts), A325N single shear:

A_b = pi × 0.75² / 4 = 0.442 in.²
r_n = Fnv × A_b = 54 × 0.442 = 23.9 kips per bolt
phi r_n = 0.75 × 23.9 = 17.9 kips per bolt

6 bolts per face:

phi R_n = 6 × 17.9 = 107.4 kips per face

This is per outer plate. For both outer and inner plates with independent bolt groups:

Total phi R_n = 2 × 107.4 = 214.8 kips

Per AISC Section B3.6, the minimum splice strength must be at least 50% of column strength. This bolt group transfers flange force through the splice plates. However, 214.8 kips < 257.0 kips -- not adequate.

Increase to 7/8 in. diameter A325N bolts:

A_b = pi × 0.875² / 4 = 0.601 in.²
r_n = 54 × 0.601 = 32.5 kips
phi r_n = 0.75 × 32.5 = 24.4 kips per bolt
phi R_n = 6 × 24.4 = 146.4 kips per face
Total = 2 × 146.4 = 292.8 kips > 257.0 kips. **Bolt shear OK.**

Step 7: Flange Bolt Bearing Check (AISC J3.10)

Bearing on outer flange plate (tp = 0.375 in., Fu = 65 ksi):

For edge bolts (Le = 1.5 in.):

L_c = 1.5 - (15/16)/2 = 1.5 - 0.469 = 1.031 in. (dh_eff = 15/16 in. for 7/8 in. bolt)
r_n = 1.2 × L_c × t × Fu = 1.2 × 1.031 × 0.375 × 65 = 30.2 kips
≤ 2.4 × d × t × Fu = 2.4 × 0.875 × 0.375 × 65 = 51.2 kips

For interior bolts (s = 3.0 in.):

L_c = 3.0 - 15/16 = 3.0 - 0.938 = 2.063 in.
r_n = 2.4 × 0.875 × 0.375 × 65 = 51.2 kips (bearing governs over tearout for interior bolts)

Per outer plate with 4 edge bolts + 2 interior bolts:

R_n_total = 4 × 30.2 + 2 × 51.2 = 120.8 + 102.4 = 223.2 kips
phi R_n = 0.75 × 223.2 = 167.4 kips per outer plate

For outer + inner:

Total = 2 × 167.4 = 334.8 kips > 257.0 kips. **Bolt bearing OK.**

Bearing on column flange (tf = 0.605 in., Fu = 65 ksi):

R_n_col_flange even higher due to thicker flange. **Flange bearing OK.**

Step 8: Flange Block Shear (AISC J4.3)

Check outer flange plate. Shear path: 2 vertical lines, each with 3 bolts at 3 in. spacing.

L_gv = 2 × (2 × 3.0 + 1.5) = 2 × 7.5 = 15.0 in. (both sides)
A_gv = 15.0 × 0.375 = 5.625 in.²
A_nv = [15.0 - 2 × (2.5 × 15/16)] × 0.375 = [15.0 - 2 × 2.344] × 0.375
     = [15.0 - 4.688] × 0.375 = 10.312 × 0.375 = 3.867 in.²

Tension path across plate width between bolt rows:

L_gt = 4.0 in. (gage)
A_gt = 4.0 × 0.375 = 1.500 in.²
A_nt = (4.0 - 1 × 15/16) × 0.375 = 3.063 × 0.375 = 1.148 in.²

R_n = 0.60 × Fu × A_nv + U_bs × Fu × A_nt
    = 0.60 × 65 × 3.867 + 1.0 × 65 × 1.148
    = 150.8 + 74.6 = 225.4 kips

Upper bound: 0.60 × Fy × A_gv + U_bs × Fu × A_nt
    = 0.60 × 50 × 5.625 + 1.0 × 65 × 1.148
    = 168.8 + 74.6 = 243.4 kips

Governing R_n = 225.4 kips.

phi R_n = 0.75 × 225.4 = 169.1 kips per outer plate

For outer + inner:

Total = 2 × 169.1 = 338.1 kips > 257.0 kips. **Block shear OK.**

Step 9: Web Splice Design

The column web splice transfers V_u = 8.0 kips and provides alignment. Use 2 PL 8 × 1/4 in. web splice plates (one each side), ASTM A36 (Fy = 36 ksi, Fu = 58 ksi).

Bolt layout: 2 bolts per side, 3/4 in. A325N, single vertical row at 3 in. spacing.

Web Plate Shear Yielding:

A_gv = 8.0 × 0.25 = 2.000 in.² per plate
R_n = 0.60 × Fy × A_gv = 0.60 × 36 × 2.0 = 43.2 kips
phi R_n = 1.00 × 43.2 = 43.2 kips per plate
Total = 2 × 43.2 = 86.4 kips > 8.0 kips. **Shear OK.**

Web Bolt Shear (2 bolts):

phi R_n = 2 × 17.9 = 35.8 kips > 8.0 kips. **Bolt shear OK.**

Since V_u = 8.0 kips is small relative to even minimal capacities, web splice is adequate with significant reserve.

Step 10: Summary — Pass/Fail

All checks pass. The governing limit state is flange bolt shear at D/C = 0.878 (with 7/8 in. A325N bolts and 6 bolts per face). This is an efficient design.

Final Splice Details:

• Outer flange splice plates: 2 PL 12 × 3/8 in. × 16 in. long, ASTM A572 Gr 50
• Inner flange splice plates: 2 PL 8 × 3/8 in. × 16 in. long, ASTM A572 Gr 50
• Flange bolts: 7/8 in. dia. A325N, 2 rows × 3 bolts per face (total 24 flange bolts)
• Web splice plates: 2 PL 8 × 1/4 in. × 10 in. long, ASTM A36
• Web bolts: 2 bolts per side (total 4), 3/4 in. dia. A325N
• Column ends: mill-to-bear for compression transfer per AISC M2.5

Related Calculators

Verify column splices with the Splice Connection Calculator. Check the column's base capacity first using the Column Capacity Calculator. For bolted connection components, use the Bolted Connection Calculator.