An aluminium bridge, whether a footbridge, a portable military bridge or a floating pontoon crossing, is built from a family of extruded sections: girders, chords and cross-beams that carry load, and deck planks, edge closures and handrails that complete it. This guide walks through 36 typical sections, what each does and which alloy and temper it is normally extruded in.
Aluminium weighs about a third as much as steel, does not rust, and can be extruded into hollow multi-cell shapes that put material exactly where it is needed. For bridges, that means light spans that can be lifted in one piece, quick to install and close to maintenance-free.
The extrusion process lets designers combine several functions in one section: a girder with integral bolt channels, a deck plank with interlocking edges and an anti-slip top, or a pontoon wall with built-in stiffeners. Fewer parts and fewer welds reduce fabrication cost and fatigue risk. The sections below fall into two groups: primary members that carry the bridge loads, and secondary members that form the walking surface, parapets and finishes.
Load-bearing structure
Sections 1 – 17: main load-bearing members
These members are designed to EN 1999 (Eurocode 9) or the Aluminum Design Manual and AASHTO LRFD, and are extruded in structural 6xxx alloys in T6 temper. Multi-cell closed sections dominate because they resist torsion and local buckling far better than open shapes of the same weight.
No.
Section
Function
Typical alloy / temper
1
Floor beam / bracket section
Floor beams, pressed-on brackets, pontoon end connectors and clip grooves
6061-T6, 6082-T6
2
Grooved chord
Top and bottom chords of trusses; grooves take bolts or connectors
6082-T6, 6005A-T6
3
Grooved main beam
Primary longitudinal girders with fixing channels
6082-T6, 6061-T6
4
Channel guide
Guide rails for launching, sliding or folding sections
6061-T6
5
Multi-purpose beam
Beams, crossbars, bracing, uprights and handrail posts
6005A-T6, 6061-T6
6
Three-cell beam
Closed hollow beam with internal webs for torsional stiffness
6005A-T6
7
Three-cell asymmetric lower beam
Lower beam where the deck or a pontoon sits on one side
6005A-T6, 6082-T6
8
Three-cell main girder
Heavier closed girder for longer spans
6082-T6, 7020-T6
9
Four-cell rectangular cross-beam
Upper cross-beams carrying deck loads across the width
6005A-T6
10
Five-cell cross-beam
Wider upper cross-beam with more bearing area
6005A-T6
11
Six-cell cross-beam
Deep cross-beam for heavy axle loads
6082-T6
12
Six-cell symmetric frame
Frame member loaded equally from both sides
6082-T6
13
Six-cell asymmetric frame
Edge frame member with connection on one side
6082-T6
14
Internal longitudinal beam
Stringers between main girders
6061-T6, 6005A-T6
15
Main pontoon section
Buoyancy hull section for floating bridges
5083 / 6082-T6 (marine)
16
Support bracket
Bearing and support brackets, often machined
6082-T6
17
Expansion joint section
Deck expansion joints that accommodate thermal movement
6061-T6, 6082-T6
Deck and finishes
Sections 18 – 36: decks, parapets and trims
Secondary sections still carry pedestrian or vehicle loads locally (deck planks and treads in particular), but many are architectural. 6063 is preferred for trims and handrails because it extrudes thin walls with a fine surface that anodises or powder-coats well.
No.
Section
Function
Typical alloy / temper
18
Angle
Bracing, edge stiffeners and fixings
6063-T6, 6061-T6
19 – 23
One- to five-cell deck panel
Hollow deck planks; more cells mean wider planks and longer spans
6005A-T6, 6082-T6
24 – 25
Three- and four-cell interlocking stair tread
Treads that interlock without separate fixings
6005A-T6
26
Three-cell interlocking deck panel
Deck planks that clip together, often friction-stir welded
6005A-T6
27
Parapet section
Pedestrian parapet rails and posts
6063-T6, 6061-T6
28 – 29
Left and right edge closures
Close the deck edges and hide the structure
6063-T5/T6
30
Deck cover
Cover strips over joints and cable runs
6063-T5
31
Girder trim cover
Cosmetic cladding over main girders
6063-T5
32 – 33
Decorative and handrail panel connectors
Join infill and handrail cover panels
6063-T5/T6
34
Handrail cover panel
Infill panels below the handrail
6063-T5
35
Deck connecting panel
Transition planks between deck modules
6005A-T6
36
Stair handrail
Hand-grip profile for stairs and ramps
6063-T6
Alloy selection
Which alloys are used and why
Alloy and temper
Typical minimum yield (EN 755-2, thin walls)
Strengths
Typical use
6005A-T6
about 215 – 225 MPa
Extrudes complex hollow shapes; good strength
Deck planks, multi-cell beams
6082-T6
about 250 – 260 MPa
Highest strength common 6xxx alloy in Europe
Main girders, chords, frames
6061-T6
about 240 MPa
Widely available; good toughness
Beams, brackets, posts (Americas, Asia)
6063-T5 / T6
about 110 – 170 MPa
Best surface finish, thin walls
Handrails, trims, closures
7020-T6 / 7005
about 280 – 290 MPa
Weldable with natural re-ageing
Military and portable bridges
5083-H111 / H321
about 125 – 215 MPa
Seawater resistance, weldable
Pontoon plating and hulls
Values are indicative minimums for typical section thicknesses; the governing values are those of EN 755-2 or ASTM B221 for the actual wall thickness. Welding reduces 6xxx T6 strength in the heat-affected zone, which Eurocode 9 accounts for with reduction factors.
Engineering
Design and fabrication considerations
Stiffness, not strength, often governs: aluminium's modulus (about 70 GPa) is a third of steel's, so deflection and vibration limits on footbridges usually set section depth
Fatigue: traffic and pedestrian-induced loading make weld details critical; EN 1999-1-3 gives detail categories, and bolted or friction-stir-welded joints often perform better
Friction stir welding: multi-cell deck planks are commonly joined edge to edge by FSW into wide, flat panels with low distortion
Thermal movement: about 23 mm per 10 m per 10 °C range; expansion joints (section 17) and sliding bearings accommodate it
Galvanic isolation: separate aluminium from steel bearings and concrete abutments with isolating pads
Execution: fabrication follows EN 1090-3 execution classes in Europe; welders and procedures are qualified to ISO 9606-2 and ISO 15614-2
Quality
Tolerances, finish and inspection
Typical requirements
Dimensional tolerances
EN 755-9 for profiles (EN 12020-2 for precision 6060/6063 sections); ANSI H35.2 for ASTM B221 orders
Straightness and twist
Per the same standards; tighter limits agreed for long girders
Lengths
Commonly 6 – 12 m; longer lengths limited by extrusion and transport
Surface finish
Mill, anodised (EN 12373 / AAMA), or powder coated; anti-slip grooves or grit coating on decks
Certification
EN 10204 3.1 certificates with chemistry and mechanical results per lot
Applications
Where these sections are used
Pedestrian and cycle bridges
Prefabricated truss or girder spans lifted in one piece over roads, rail and rivers.
Bridge deck replacement
Light aluminium decks on existing steel structures, raising load rating by cutting dead weight.
Floating and pontoon bridges
Modular pontoons with aluminium decks for marinas, temporary crossings and emergency use.
Military and portable bridges
Rapidly deployed gap-crossing bridges in high-strength weldable 7xxx and 6xxx alloys.
Access bridges and gangways
Ship-to-shore, offshore and industrial access gangways.
Stairs and ramps
Interlocking treads and handrails for bridge approaches and platforms.
6082-T6 in Europe and 6061-T6 elsewhere are the usual choices for main girders; 6005A-T6 is preferred for complex multi-cell sections such as deck planks. 7020 is used where higher weldable strength is needed.
How long can aluminium bridge extrusions be?
Commonly 6 – 12 m per piece, limited by the extrusion press, ageing ovens and transport. Longer members are spliced by bolting or welding.
Why are bridge deck sections multi-cell?
Closed cells resist local buckling and torsion, carry wheel loads between webs and let wide planks be friction-stir welded into flat panels.
Do aluminium bridges need painting?
Usually not. Most are left mill finish or anodised; coatings are used for colour or appearance.
What design code applies to aluminium bridges?
EN 1999 (Eurocode 9) in Europe and many other regions, and AASHTO LRFD with the Aluminum Design Manual in North America.
Can you supply profiles to our own drawings?
Yes. Send the section drawings with alloy, temper, length and finish, and we will confirm die and supply options.
Building an aluminium bridge?
Send section drawings, alloys, tempers and quantities. We will confirm supply, certification and delivery to site.
