What is a Vierendeel bridge?
A Vierendeel bridge is a bridge whose load-bearing main girders are built as Vierendeel trusses. In Dutch it is called a vierendeelbrug. Such a girder has a top and bottom chord connected by vertical posts, without diagonals in between. The connections are moment-resisting, so the whole acts as a rigid frame. The system is named after the Belgian engineer Arthur Vierendeel.
Recognising it
You can recognise a Vierendeel bridge by its side walls with rectangular openings, like a ladder on its side. The top chord is often curved, so that the girders are deeper in the middle than at the supports. The corners between posts and chords are usually rounded or widened, because that is where the greatest forces occur. A truss bridge, by contrast, has diagonals that form triangles.
Where are they found?
Vierendeel bridges were built mainly in Belgium, including over the Albert Canal and other canals. Examples can also be found outside Belgium, as railway, road or footbridges. Many older examples have since been replaced or protected as industrial heritage.
Advantages and disadvantages
- Advantage: an open, uncluttered appearance without crossing diagonals, which designers experience as calm and elegant.
- Disadvantage: more steel is needed than for a truss bridge with the same span, because the members work in bending.
- Point of attention: the rigid joints are sensitive to fatigue and corrosion. A well-known example is the welded Vierendeel bridge at Hasselt over the Albert Canal, which collapsed in 1938 due to brittle fracture at the welds. Inspection therefore focuses mainly on the corner connections.
Tips for investigation or restoration
- Consult the original drawings and calculations in the owner’s archive before working on a historic Vierendeel bridge.
- Treat corrosion in the joints as a priority: that is where loss of material is most critical.
Related terms
- Vierendeel truss
- Bridge
- Truss bridge
- Arch bridge
- Girder
- Abutment
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