Deployment of Instrumentation for In-Service Monitoring

Structural Adequacy and Self-Certification Graeme Orr has written from Edinburgh, responding to Stan Lawrence (21 March): Self-certification has been the practice in Scotland for some years now: the local authority Building Control may accept for a building project either sufficient calculations and drawings or just the drawings backed by an engineer’s Design Certificate (a standard form 4A for new buildings, 4B for alterations/extensions, issued by each local authority). At present the ‘Approved Person’ signing these certificates need only be a chartered civil or structural engineer. In fairness to the Building Control Officers, most authorities require proof of current membership, and until they are familiar with the signator or his design engineer, they will raise queries on building warrant submissions to ascertain whether the signator is indeed competent to approve the design. However, no other checks are made, to my knowledge, as to whether the signator has professional indemnity or whether he is (say) a geotechnical engineer.

This paper describes the progressive longitudinal distortion of certain Georgian and Victorian straight terraces (known as the ‘bookend’ effect) caused by cyclical expansion and contraction of their continuous facades. Four specific case-studies are given, covering the range of purpose-built and converted terraces at risk from the bookend effect. The results of 2 years’ continuous movement monitoring of a long terrace with electrolevels is given, revealing complex diurnal and seasonal movement, estimated to range from 1428mm. The operational difficulties of electrolevels and the validation of their output is described. A poor prognosis for the future life of old terraces is ventured. Remedies and palliatives are suggested, without which such end-of-terrace properties will inevitably collapse, like failed bookends. C. Richardson and A.G. Messenger

DERA, the Defence, Evaluation & Research Agency is increasingly providing test and evaluation services to commercial customers.