Conservation compendium. Part 5: Inspection and repair of cantilever stone staircases

Strut-and-tie modelling is a simple method of modelling complex stress patterns in reinforced concrete as triangulated models. It is based on the same truss analogy as the design for shear in Eurocode 2 and can be applied to many elements. It is particularly useful where normal beam theory does not apply, i.e. where plane sections do not remain plane, e.g. in deep beams, corbels and pile caps. EC2 provides information about the use of strut-and-tie modelling and this article is an introduction for engineers who want to take advantage of this useful analysis method.

Historic buildings and structures, like any other, move to some degree, whether due to thermal effects, changes in moisture levels in the structural fabric, influences on the founding subsoil, or environmental forces. The key question for the conservation engineer is to determine whether the movement is progressive and presents a risk to the structure. This article introduces engineers to the various techniques available to monitor movement in historic structures, from simple manual techniques which are less commonly used today, to sophisticated electronic systems. The form of monitoring will depend on the nature of the assumed movement, the funds available, and the possible consequences if the movement is progressive.

This article focuses on the phenomenon of 'bond timbers', which were commonly built into masonry walls from the late 17th to the early 19th century. Guidance is offered to engineers who may encounter these when working on an existing building.