Utilization of tie-beams for strengthening stone masonry arches in Nabataean construction

This paper attempts to demonstrate the use of timber ties in the construction of stone masonry arches in Jordan from the late first century BC onwards. It investigates the techniques used and relates them to present-day structural design. In Nabataean architecture, tie-beams were used for strengthening of masonry structures and, in particular, to strengthen masonry arches and vaults against their most critical failure mechanism. The tie-beams introduce tension resistance. This fact has two important consequences: the capacity of the arch itself is increased, and the lateral thrust transmitted to the piers is reduced, thereby increasing the strength of the arch-pier system. Collapse of an arch typically occurs when no tie-rods or tie-beams are used and the piers are unable to bear the thrust of the arch. While the first effect has been stressed by the existing research, less attention has been paid to the second effect, which nevertheless is very important for practical applications. In this paper, the main methods are critical analysis of archaeological information enriched by structural evaluation of the strength of such systems. From such an approach, reliable hypotheses can be made concerning the design and construction process. The effect of bonding a tie-beam to the intrados of a semi-circular arch on the lateral thrust is evaluated analytically using the non-linear finite element package ABAQUS software (HKS, version 6.5). The results are analysed based on the determination of the thrust line. This study concludes some recommendations for the conservation of historical buildings in seismic regions, based on a thorough understanding of their structure, construction features and materials, which may help to prevent earthquake-induced damage to buildings taking into account traditional and modern materials and techniques.