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There may be a need to assess the strength of the reinforcement in an existing structure, perhaps to determine its ability to carry additional loads or following modification. In general this can be estimated from the age of the structure; the strengths specified in British Standards for reinforcement have gradually increased over the years, see separate entry Reinforcement design strengths (historic). If there is any doubt, suitable lengths of reinforcement should be removed from the structure and tested. The measured strength, or that assumed from the Standard in force at the time, can then be used to calculate the strength of the structure (see Assessment of existing structural strength).
If details of the Standards to which the structure was designed and constructed are available, these can obviously be used to obtain an indication of the expected steel strength. Further information on the development of specified steel strengths over the years is given in Concrete Society Technical Report 70, Historical approaches to the design of concrete buildings and structures.
Acknowledgement: The Concrete Society
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