Failure mechanism of Gothic Cross Vaults
In the structural system of Gothic churches, failure of vaults mostly occurs when the dynamic equilibrium created by the main elements (arches, vaults, slender piers, walls) is disturbed. This equilibrium is usually disturbed by failure of the supports or due to instability of the lateral elevation. The vault is said to have failed when enough hinges develop to transform the vault into a mechanism. Studies and laboratory testing indicate that the predominant source of failure is lateral instability which affects the vaults by spreading their supports. This can occur due to many reasons such as design errors or erroneous intervention. The failure pattern which arises under such circumstances tends to follow the following trend:
Longitudinal cracks forming a hinge line along the intrados followed by a transverse detachment at the wall edge and abutments.
This eventually forms a 3-hinge mechanism that leads to collapse.
It has been estimated from observed lateral displacements in churches that as long as the spread of the supports is less than 1/100 of the transverse span, the cross-vault tends not to collapse.
Longitudinal cracks forming a hinge line along the intrados followed by a transverse detachment at the wall edge and abutments.
This eventually forms a 3-hinge mechanism that leads to collapse.
It has been estimated from observed lateral displacements in churches that as long as the spread of the supports is less than 1/100 of the transverse span, the cross-vault tends not to collapse.
References
[1] Theodossopoulos D, Sinha BP, Usmani AS & Macdonald AJ. Assessment of the structural response of masonry cross vaults. Strain, Journal of the British Society for Strain Measurement 2002.
Theodossopoulos D, Sinha B. Structural safety and and failure modes in Gothic vaulting systems. 8th international seminar on structural masonry 2008.
Theodossopoulos D, Sinha B. Structural safety and and failure modes in Gothic vaulting systems. 8th international seminar on structural masonry 2008.