Condition and future use of early age steel bridges in a historic city

Due to its location at the confluent of rivers Scheldt and Lys and the many canals and ditches, built to overcome flooding, the historic city of Ghent has many bridges. Their number decreased after covering many waterways. Presently, of the 124 left, the oldest are vaulted arches and in good condition. In addition, every 30 year period large refurbishments have been made and even total replacement according to original structures has occurred for 5 bridges. The condition of 2 early-age steel portal frame bridges, used by buses and tramways is the most critical. Possible design loading schemes, used at the time of their construction, are considerable lighter and do not comply with present codes. Careful numerical analysis and the use of realistic loading schemes, supplemented by detailed inspection, has allowed to establish a clear view on the remaining load carrying capacity. In spite of some heavy corrosion, reducing the dead load on the walkways may very well be sufficient to obtain sufficient load carrying capacity, without changes of the appearance and function of bridge parts, thus extending the life of these bridges.