Bolted & Riveted Connections Notes

Last reviewed 16 Sept 2026 · 6 min read

Connections in steelwork

Steel members are joined by rivets, bolts or welds. Rivets have largely given way to high-strength bolts and welding, but riveted joints still exist in older bridges and are covered in exams.

Types of bolts

Bolt	Designation	Behaviour
Black (unfinished) bolts	Property class 4.6 ( $f_{u b}$ = 400 N/mm²)	Bearing type; used in light structures
Turned and fitted bolts	Close-tolerance holes	Bearing type, less slip
High-strength bolts	Classes 8.8 ( $f_{u b}$ = 800), 10.9 ( $f_{u b}$ = 1000)	Bearing type or friction type
High-strength friction-grip (HSFG) bolts	Pre-tensioned 8.8/10.9 bolts	Load carried by friction between plates; no slip at service load

Class 4.6 means $f_{u b}$ = 4 × 100 = 400 N/mm² and $f_{y b}$ = 0.6 × 400 = 240 N/mm².

Types of joints

Lap joint — plates overlap; bolts in single shear; eccentricity causes bending.
Butt joint — plates butt with cover plates on one side (single shear) or both sides (double shear).

Modes of failure

Shear failure of the bolt (across the shank or threads).
Bearing failure — crushing of the plate (or bolt) at the hole.
Tearing (rupture) of the plate across the net section.
Shear-out / splitting of the plate at the end (insufficient end distance).
Tension failure of the bolt (in tension connections).
Block shear of the connected part.

Detailing rules (IS 800:2007)

Code ProvisionIS 800 — holes, spacing and edge distance

Hole clearance over bolt diameter: 1 mm for bolts up to 14 mm; 2 mm for 16–24 mm; 3 mm for bolts over 24 mm.
Minimum pitch: $2.5 d$ ( $d$ = nominal bolt diameter).
Maximum pitch: $32 t$ or 300 mm, whichever is less ( $t$ = thinner connected plate). In tension members: $16 t$ or 200 mm; in compression: $12 t$ or 200 mm.
Minimum edge and end distance: $1.7 \times$ hole diameter for sheared or hand-flame-cut edges; $1.5 \times$ hole diameter for rolled, machine-flame-cut, sawn or planed edges.
Maximum edge distance: $12 tε$ ( $ε = 250/ f_{y}$ ), 40 mm + 4t for exposed edges.
Tacking fasteners in built-up members at a maximum spacing of about 32t or 300 mm.

Bearing-type bolts in shear

FormulaDesign strength of one bolt

Shear capacity:

V_{d s b} = \frac{V _{n s b}}{γ _{mb}} = \frac{f _{u b}}{3 γ _{mb}} (n_{n} A_{nb} + n_{s} A_{s b})

$n_{n}$ , $n_{s}$ = number of shear planes through threads and through the shank; $A_{nb}$ = net tensile area of bolt (≈ $0.78 \times π d^{2} /4$ ); $A_{s b}$ = shank area; $γ_{mb}$ = 1.25.

Bearing capacity:

V_{d p b} = \frac{2.5 k _{b} d t f _{u}}{γ _{mb}}, k_{b} = least of (\frac{e}{3 d _{0}}, \frac{p}{3 d _{0}} - 0.25, \frac{f _{u b}}{f _{u}}, 1.0)

$t$ = total thickness of connected plates experiencing bearing in one direction; $d_{0}$ = hole diameter; $e$ = end distance; $p$ = pitch.

Bolt value = the smaller of $V_{d s b}$ and $V_{d p b}$ .

Reduction factors

Long joints: if the joint length $l_{j}$ exceeds $15 d$ , multiply shear capacity by $β_{l j} = 1.075 - \frac{l _{j}}{200 d}$ , with $0.75 \leq β_{l j} \leq 1.0$ .
Large grip: if total grip $l_{g}$ exceeds $5 d$ , $β_{l g} = \frac{8 d}{3 d + l _{g}} \leq β_{l j}$ (grip not to exceed $8 d$ ).
Packing plates thicker than 6 mm: $β_{p k} = 1 - 0.0125 t_{p k}$ .

Strength of the plate and efficiency

Plate rupture across the net section: $T_{d n} = \frac{0.9 A _{n} f _{u}}{γ _{m 1}}$ ; yielding of gross section $T_{d g} = \frac{A _{g} f _{y}}{γ _{m 0}}$ .

Efficiency of joint = \frac{design strength of joint}{design strength of the solid plate} \times 100%

For a staggered bolt line, the net area uses $A_{n} = [b - n d_{0} + \sum \frac{p _{s}^{2}}{4 g}] t$ ( $p_{s}$ = staggered pitch, $g$ = gauge).

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Bolted & Riveted Connections