Old Structures in Relation to Soil Conditions

Abstract

This Paper analyses the long-term behaviour of old structures, their settlements, instantaneous rotations and their response to superimposed loads. In the context of additional loads, it is shown how little reliance can be placed in ‘reserve resistance’; especially, for structures with a very small factor of safety, very small superimposed loads applied in a continuous direction over a long period of time may cause significant deformations. At the same time, a study is made of the instantaneous centre of rotation of a building in danger. In discussing famous churches, rotations due to the long-term effects of eccentric loads and of differential settlements created by an unequal loading distribution over a given surface are described. A long-term progressive creep of a fill in Stockholm over six centuries is also discussed. In the second part of the Paper, the vulnerability of old buildings to settlements caused by open excavations and tunnelling is studied; the notion of surface radii of curvature is proposed. Finally, the subject of the long-term stability of old tunnel linings is examined. © 1975, Thomas Telford Ltd. All rights reserved.