Superloads on Highway Bridges in Southern Africa

By the end of the century some highways in Southern Africa may be required to carry loads of over 1,000 tons. The transporters used to support these loads may have as many as 320 wheels and are therefore very long and wide. Although new bridges will have to be constructed for the heaviest loads, it is possible that many existing structures can support or be strengthened to carry loads of up to about 550 tons gross. Accurate analytical techniques are needed to assess the effects of these superloads on bridges so that every reserve of strength may be utilized. However, the multiplicity of structural configurations, construction materials, and original design specifications prevents development of simple generalized methods. Assessments, involving critical stress, may be made rapidly and precisely using a computerized influence surface technique. The Generate-Simulate-Compare (GSC) system, originally developed for abnormal load investigations, is being extended to assess the effects of future superloads on highway structures.