Bolted vs Welded Connections

Quick pick (TL;DR)

Field connections → bolted (A325/A490) — fast, weatherproof, easy to inspect.
Shop connections & stiff moment joints → welded.
Vibration/fatigue or no-slip → slip-critical bolts or welds.
Default simple-shear beams to bolted double-angle/shear-tab; moment frames often shop-welded, field-bolted.

Step 1 — Bolted vs welded

	Bolted	Welded
Best location	Field	Shop
Speed / QC	Fast, easy QC	Needs NDE
Stiffness	Some slip	Rigid
Fatigue	Slip-critical	Good if smooth
Modify	Easy	Hard

Step 2 — Bolt capacity

Simple shear connection

Given Shear V = 200 kN M20 A325, threads included (N), single shear Fnv = 372 MPa , φ = 0.75 , Ab = 314 mm² Step 1 — φRn per bolt φRn = φ · Fnv · Ab φRn = 0.75 × 372 × 314 φRn = 87,606 N = 87.6 kN/bolt Step 2 — Number of bolts n = V / φRn = 200 / 87.6 = 2.3 → use 4 bolts (min rows + eccentricity) Step 3 — Also check bearing/tear-out at holes; plate & weld of cleat

Step 3 — Welds

Fillet welds; size to load & thinner part.
CJP welds for moment joints (UT/RT).
Match electrode; qualify WPS (AWS D1.1).

Bolt group calculator (shear)

Bolt shear capacity & number

φRn = φ·Fnv·Ab; n = V / φRn.

Shear V (kN)

Fnv (MPa)

Ab (mm²)

Shear planes

Bolt shear only — also check bearing, tear-out, block shear & plates.

Common mistakes

Field welding instead of bolting.
Bearing bolts on fatigue joints.
Checking bolt shear only.

Requisition & datasheet

Type & forces; bolts or weld + NDE.
Plate & grade; slip-critical; code.

Frequently asked questions

What should I know about Bolted vs Welded Connections?

Field connections → bolted (A325/A490) — fast, weatherproof, easy to inspect. Shop connections & stiff moment joints → welded. Vibration/fatigue or no-slip → slip-critical bolts or welds. Default simple-shear beams to bolted double-angle/shear-tab; moment frames often shop-welded, field-bolted.

Which standards or codes apply?

AISC 360 (connection design), RCSC (bolting); AWS D1.1 (welding); ASTM F3125 (A325/A490 bolts); Eurocode 3 Part 1-8.

Standards — AISC 360; RCSC; AWS D1.1; ASTM F3125.