Analysis of an arch in the Annunciation church at Ħal Millieri

Abstract

The arch analysed, that closest to the door at the west end, was assumed to be representative of the rest of the arches in the chapel, even though a glance at the interior shows that no two arches are exactly the same. Any conclusion applicable to this arch is assumed to apply also to the rest of the arches despite quite appreciable variations from this norm. The arch, the wall thicknesses, the heights, the ceiling and so on were measured to an accuracy compatible with the scope and precision of the exercise, and although the arch was found to be slightly asymmetrical about its vertical centre-line, this was ignored in the calculations as the error involved is minimal. In such masonry arches, where the discontinuity of the elements introduces highly variable friction, it is difficult to visualise any of the forces at the contact faces, whether inside the arch or between the arch and the buttress wall.