Construction methods · Steel erection

Truss assembly and erection

Trusses are assembled from chords, diagonals and verticals joined at panel points with gusset plates. They can be built on falsework, cantilevered out panel by panel, assembled whole on the bank and floated or slid in, or lifted in sections. The geometry must close: trusses are unforgiving of accumulated error.

How bridges get built · Steel erection · Truss assembly and erection

Also called: truss erection, panel-point erection, truss bridge construction

Truss assembly and erection — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Shop-fabricate members with drilled connections from a matched assembly; trial-assemble in the shop for long spans.
Erect on temporary towers (short spans), by cantilever with a derrick (long spans), or fully assembled on shore.
Bolt panel points progressively; install the deck system and bracing to stabilise the trusses.
Survey camber and alignment continuously; adjust with temperature in mind.

Where it fits

Rail bridges, long-span river crossings, sites where the deck must be shallow for clearance, floating or sliding in complete trusses.

Where it does not

Sites without room for assembly or without lifting capacity; highly repetitive short spans where girders are cheaper.

Plant, pace and money

PlantCranes, derricks, temporary towers, bolting crews.

ProductivityOne panel per day on towers; slower by cantilever.

CostSteel USD 4,000-8,000 per tonne fabricated and erected.

Risks and controls

What goes wrong

Gusset plate deficiencies (I-35W), member buckling during erection, misfit at closure.

Quality assurance

Shop trial assembly, gusset design check, bolting inspection, survey.

Examples

Ikitsuki (400 m continuous truss), Japanese and Chinese rail-road trusses, US Mississippi trusses.