Zohreh Zahiri - MA Student in architectural conservation, Art University of Isfahan
Dariush Heydari Beni - Department of architectural conservation, Art University of Isfahan
Akbar Haj Ebrahim Zargar - Faculty of architecture and urban planning. Shahid Beheshti University

Opening spaces (konoo) in the both sides of main arches play an important role in structural stability of masonry arch bridges. However they are not always visible in the façade and are sometimes hidden in the interior fill spaces. This paper represents the approach of detecting these hidden openings by structural survey carried out on Khan Bridge in south Iran as a case study. The large spaces behind the arches in Khan Bridge seem to be filled with massive masonry of mortared stones. Whereas analyzing the bridge with Arco software showed that arches would surely crack or break down under this heavy amount of load. Finally by analyzing of the bridge, it was found that the fill spaces of the arches may contain hidden openings to reduce the amount of load applying to the arches.

masonry arch bridges, hidden opening (konoo), arch analyzing