When existing buildings need to be inspected and assessed, the structural engineer is often presented with the challenge of needing X-ray eyes. Lacking such a gift, and despite what clients may assume, the engineer draws instead on knowledge and experience to make value judgements in many situations, with appropriate margins of safety and consideration of appropriate risk incorporated along the way. Codes of practice and British Standards are not to be ignored, but are a useful tool to assist with this process.
This article aims to discuss some of the issues, challenges, tools and techniques available to the practising structural engineer when assessing existing structures. While the article focuses principally on floor structures, the techniques can be used on a range of applications to provide an understanding of how existing structures are actually behaving, rather than how we might think they are working.