DAVID M. LILLEY University of Newcastle, England

A section of the vaulted masonry roof of Durham Cathedral has been analyzed to determine values of deflection and stress produced by its self-weight and also by loose slate debris held within voids on its upper surface. A photogratnmetric survey of the vaults and a computer generated surface profile were used to create a finite element model of the roof which indicated that it comprises masonry weighing about 855kN, and that it supports a further 1100kN of slate debris. The maximum vertical deflection on completion of construction was predicted to be about 0.6mm; tensile stresses were generally less than 0.45 N/mm2. Imposed load from the slate debris increased the maximum vertical deflection to about 1.5mm and the maximum tensile stress to 0.8N/mm2. Further analysis has shown the behaviour of the vaulted structure to be susceptible to horizontal movement at its supports.