Construction methods · Cable-supported and arch bridges

Network tied arch construction

A network tied arch (inclined hangers crossing twice or more) is light enough to be built whole on falsework or on the bank and moved in, because the arch and tie are slender. The hangers are installed and tensioned in a strict sequence so that none goes slack during the deck pour.

How bridges get built · Cable-supported and arch bridges · Network tied arch construction

Also called: network arch erection, crossing hanger arch

Network tied arch construction — concept diagram — Concept diagram (TheBridgeEng)

How it is done

Assemble the arch ribs and the steel tie on temporary supports or on shore; install the hangers in the design sequence.
Cast the concrete tie or deck slab in stages that keep every hanger in tension, or erect the whole steel structure then cast the deck with temporary hanger adjustment.
Move the span by float-in, slide or SPMT, or strike the falsework.

Where it fits

Single spans of 80-260 m over rivers, canals and railways; replacement spans that must go in during a short closure.

Where it does not

Sites where the assembly area does not exist; designs without a hanger sequence analysis.

Plant, pace and money

PlantFalsework or assembly yard, cranes, hanger stressing equipment, movers.

ProductivityAssembly in months; installation in a day.

CostSteel USD 5,000-8,000 per tonne erected.

Risks and controls

What goes wrong

Slack hangers during deck casting, arch buckling before the deck stiffens the system.

Quality assurance

Hanger force records at each stage, arch geometry survey.

Examples

Brandanger (Norway), Providence River, Blennerhassett, many Norwegian and German road bridges; the game's network tied arch type.