The masonry arch on spreading supports

This paper seeks to determine the horizontal support movements necessary to cause collapse for a rigid-block arch. For masonry arches in historical buildings, small movements of the supports can destabilise the arch and can lead to collapse over time. As the supports move apart, the geometry of the arch adapts, causing the crown of the arch to descend, which increases the value of horizontal thrust. A rigorous application of thrust line analysis illustrates that various hinge locations are possible for extreme geometry changes. New computer programs are used to track the changing equilibrium conditions as the supports move and the results are verified experimentally. The analysis is extended to consider an arch supported on leaning buttresses and is illustrated by a case study.

John A. Ochsendorf, BSc, MSc, PhD
Assistant Professor of Building Technology, Massachusetts Institute of Technology, Cambridge, MA 02139 USA