Bailey Bridge is also known as a prefabricated road steel bridge. It was invented by British Engineer Donald Coleman Bailey in 1938.
These bridges use high-strength steel as a material and are manufactured into a lightweight standardized bridge unit construction, including beams, longitudinal beams, bridge decks, bridge seats, and connectors.
Bailey Bridge is a modular prefabricated steel bridge. It is connected by steel Bailey panels through bolts and other fasteners. Its simple structure makes it especially suitable for situations requiring rapid bridge construction.
The concept behind the Bailey Bridge was to offer a temporary bridge that could rapidly and manually be created in emergencies.
Baily bridges can be quickly assembled at sites, for various spans and loads with only dedicated installation equipment. The Bailey bridge was originally used in the military bridge field. However, it has been widely used in the civilian field since the 1960s.
Components of Bailey bridge
The basic Bailey bridge is made up of three main parts, the floor, the stringers, and the side panels. The floor of the bridge is made up of several 19-foot-wide transoms (5.8 m) that run across the bridge. Across the bottom of these, forming a square, are 10-foot-long stringers (3.0 m).
It can stand to a maximum free span length of 51 meters (167.30 feet), with a deck net width of 4 meters (13.10 feet). The bridge panels are composed of welded high-grade structural steel elements. The girders are lightweight composite panels connected by strong steel pins.
The larger spans of such bridges can be as long as 69 meters, and the width of the lanes can reach about 3.7 meters. When wheeled vehicles are running on it, the allowable maximum speed is 30 kilometers per hour, and the allowable speed of tracked armored vehicles is 5 kilometers per hour.
How long does it take to build a Bailey bridge?
It may vary with the number of men used on construction, with the size and span, etc. But forty men can construct a complete bridge. In ideal conditions, a short and single-tier bridge can be assembled in three to four hours.
The longest Bailey bridge was built in October 1975. This 788-meters (2,585 ft), two-lane bridge crossed the Derwent River at Hobart, Australia. It was opened around a year after the Tasman Bridge disaster destroyed the only river crossing, dividing the city in two.
A typical Bailey bridge construction process
The main steps of Bailey Bridge construction include measuring and positioning the position of the bridge, pier pouring, assembly of Bailey bridge, installation of Bailey bridge, landing and correcting the position of the main body of the bridge on the other bank, laying of the bridge deck and laying of connecting roads on both sides of the bridge deck, etc.
1. Determination Of The Bailey Bridge Location
According to the requirements of the Bailey Bridge design drawings, the site is measured to determine the positions of the piers on both sides of the Bailey Bridge. A hydraulic backhoe is needed to clean the roadbed. The excavation size for bridge pier construction is approximately 5m×3m.
2. How To Pour The Piers Of Bailey Bridge
At the position of processed bridge piers, a 1.5m×1m M7.5 mortar masonry foundation is first made, and then C30 concrete is used for pouring. When the concrete reaches 80% of the design strength, the Bailey bridge can be erected.
3. Start To Assemble The Bailey Bridge
Deliver various parts from the Bailey Bridge parts list to the construction site. After the pier pouring is completed, the assembly of the components of the Bailey Bridge can be started.
The longitudinal beams and cross beams of the Bailey bridge are composed of 7 standard double-row reinforced Bailey panels, assembled in a single layer, as the main load-bearing members of the bridge body. The main Bailey beams of each group are assembled by 2 rows of standard truss pieces, arranged with a spacing of 0.75m, and are staggered with 0.75m×1.5m support frames. The main Bailey frame beams of each group are connected by a standard support frame between the spans. The main Bailey beam is also connected by a standard support frame in the vertical direction between the spans. A support frame is used for horizontal connection between groups.
4. How To Install Bailey Bridge？
When the bridge construction site has a suitable site for assembling Bailey pieces, or there is no other special bad terrain, the cantilever push-out method can be used for the installation of the Bailey bridge. When installing the Bailey bridge in a narrow site or a special terrain, the wire rope sling method can be considered to install it or design an appropriate installation method according to the actual situation.
When adopting the cantilever push-out method, firstly, rollers are installed on both banks of the river, and the bridge trusses and connecting beams are installed on the rollers pushed out of the bank. Then use the loader located on the other side of the river for towing. Each time a group of Bailey panels is installed, it advances a certain distance. Until the entire bridge body is pushed to the opposite bank.
After the bridge body reaches the opposite bank, hydraulic jacks are used to place the Bailey structure at the bridgehead into the bridge seat. After the angle adjustment of the measuring instrument, it finally falls into a precise position.
5. Laying Of Bridge Deck
The deck structure of Bailey Bridge is laid with standard parts of cross beams and longitudinal beams. Wooden or steel bridge decks can be selected.
6. Construction Of Roads At Both Ends Of The Bridge
Backfilling the road connecting the original construction road and the bridge with gravel has to be done for the completion of the construction.