The Structural Engineer > Archive > Volume 82 (2004) > Issues > Issue 1 > Are structures being repaired unnecessarily?
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Are structures being repaired unnecessarily?

Structural engineers are increasingly finding themselves assessing existing structures rather than designing new ones. These need to be checked because loads have changed or the materials have deteriorated, or simply because the owner (or an insurance company) wants reassurance that the structure is adequate. Many of these structures are failing the checks, which results in work for the engineer but expense for the client and a feeling amongst the general public that we are surrounded by bridges and buildings that are inadequate. But is this really the case? Very few structures actually collapse because a slightly increased load overcomes a slightly reduced load capacity caused by corrosion. Gross errors do happen – a 20t truck driven over a bridge with a 2t weight limit is not something the engineer can be blamed for, but corrosion of critical structural elements, such as prestressing tendons, is something for which engineers should check. The problem to which this paper is addressed is the structure which has apparently been giving good service for many years which suddenly appears to be inadequate because of a reanalysis. The relationships are considered between elastic theory and plastic theory, design methods and analysis methods, and the upper and lower bound theorems. These raise various conflicts for engineers that can have important consequences. Chris Burgoyne, MA, MSc, PhD, CEng, MIStructE, MICE Dept of Engineering, University of Cambridge

Author(s): Burgoyne, Chris

Keywords: structures;appraising;rectangular slabs;design;analysis;loads;checking