Modular temporary and emergency bridges (Bailey, Acrow, Mabey)

How bridges get built · Heavy lift, moving and accelerated construction · Modular temporary and emergency bridges (Bailey, Acrow, Mabey)

Also called: Bailey bridge, panel bridge, modular steel bridge, emergency bridge, temporary detour bridge, Acrow bridge, Mabey bridge

How it is done

Choose the configuration from span and load class: number of trusses per side (single, double, triple) and storeys, deck width, and whether a launching nose or intermediate piers are needed; check bearing pressures at the bank seats.
Prepare bank seats or temporary abutments (timber or steel grillages, concrete sills or piled supports) on both sides, level and set out, and an assembly area on the near bank in line with the gap.
Assemble the bridge on rollers on the near bank (panels pinned into girders, transoms and bracing fitted) with a lighter launching nose at the front, adding tail load if needed to keep the balance.
Launch by pushing with a machine, winch or jacks across the gap on rollers until the nose reaches the far-bank rollers, keeping the centre of gravity behind the rear rollers at every stage.
Remove the launching nose, jack the bridge down onto its bearings or base plates, and fit the deck units, kerbs and approach ramps.
Load test or proof-run if specified, post load and speed limits, and open to traffic; inspect pins, bolts and bearings regularly while in service.
At the end of use, reverse the sequence (remove decking, launch back or lift out by crane) and return components for inspection and reuse.

Key numbers

Classic Bailey panel3.05 m long, about 1.45 m high, about 270 kg (carried by six men)
Single spanstypically 10–60 m; any length as multi-span bridges on piers
Deck widthsingle lane about 3–4.2 m; two-lane systems about 7–7.5 m
Installationan emergency single span in days once bank seats are ready (Skagit River temporary spans open within four weeks of the collapse)
Supply costabout USD 2,000–5,000 per m² of deck (indicative)

Where it fits

Emergency replacement after collapse, flood or earthquake; temporary detours during bridge replacement; construction access over rivers and haul roads; permanent bridges on rural and remote roads; military gap crossing; spans of about 10–60 m.

Where it does not

Permanent use on high-speed, high-volume routes; bank seats that cannot carry the concentrated end reactions; single spans beyond the system's tables; corrosive marine exposure without galvanised components and an inspection regime.

Choosing it

Choose a modular panel bridge over a permanent replacement when access must be restored in days or weeks (collapse, flood, earthquake), or for a construction detour that will later be removed.
Choose it as a permanent bridge in remote or developing regions where heavy plant and skilled labour are scarce; components are light enough for hand assembly and small cranes.
Prefer a conventional girder bridge for permanent use on busy routes: panel bridges have many pins and bolts to inspect, lower speed limits and noisier decks.
Hire for short temporary needs; buy when the bridge will stay for years or be reused on several sites.

Plant, pace and money

PlantPanel bridge kit (panels, transoms, bracing, pins, deck units), launching nose and rollers, small crane or telehandler, pushing machine or winch, jacks for lowering, grillage or sill bank seats.

ProductivityA small crew assembles and launches a 30–50 m single span in a few days; multi-span bridges at roughly 10–30 m per day once the piers are ready.

CostIndicative: supply about USD 2,000–5,000 per m² of deck; hire is cheaper for short temporary needs; erection and bank seats are extra.

Risks and controls

What goes wrong

Overturning or nose drop during launch if the balance is wrong, under-strength bank seats, missing or loose pins and bolts, wear and fatigue under sustained heavy traffic, impact from over-height loads on through-truss configurations, corrosion of reused components.

Quality assurance

Configuration checked against the manufacturer's load tables or an independent design, launch balance checked at each stage, inspection of components before reuse, pin and bolt checklists, load test or proof run where required, periodic inspection in service.

Origins

Donald Bailey designed the panel bridge for the British War Office in 1940–41, and the first units reached troops in December 1941; the 558 m Blackfriars Bailey bridge over the Rhine at Rees was built in about two days in March 1945. Post-war firms such as Mabey and Acrow developed heavier civilian systems (for example Mabey's Compact 200, 1988).

Examples

Wartime Bailey bridges in North Africa, Italy and across the Rhine (Blackfriars at Rees, 1945), the I-5 Skagit River temporary spans (2013), and large rural bridge programmes in Asia and Africa, such as the Philippines in the 2000s.

Case studies

Blackfriars Bailey Bridge, Rees (Rhine)Germany · 1945558 m Bailey bridge including ramps, on pontoons across the Rhine, built by the Royal Canadian Engineers in about two days in March 1945; the longest Bailey bridge built across the Rhine.

I-5 Skagit River Bridge temporary spansUSA · 2013After a span collapsed on 23 May, two modular steel spans of about 49 m (one per direction) were assembled and opened on 19 June, carrying traffic until the permanent span was slid in on 14–15 September.

President's Bridge ProgrammePhilippines · 2000sAbout 1,500 modular steel bridges supplied for rural roads.