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Vaulted structures in history and modern structural solutions
Published in Pere Roca, Paulo B. Lourenço, Angelo Gaetani, Historic Construction and Conservation, 2019
Pere Roca, Paulo B. Lourenço, Angelo Gaetani
Although the origin of masonry vaulted structures is lost in the mists of time, being practically impossible to date it, to many, the first example was the so-called corbel (or false) arch. This is an arch-like construction that uses the technique of corbeling (placing stones progressively cantilevering) to span a space or void in a structure (Figure 4.1). The corbel arch is thus constructed by offsetting from each supporting side successive courses of stone so that they project towards the symmetry axis, until the courses meet at the apex of the archway (often capped with flat stones).
Experimental and Theoretical Studies to Characterize Structural Behavior of Dry-Stone Corbelled Arches under Support Disturbances
Published in International Journal of Architectural Heritage, 2022
In another study by Croci (1998), a basic understanding on the structural behaviour of corbel arch was presented comparing it with the true arch. The structural behaviour of a corbel arch is different from that of a true arch, where two conditions need to be satisfied, namely the safety against overturning due to overhanging block weights giving rise to overturning moment that has to be less than or equal to the resisting moment, and secondly the safety against sliding failure along the joints such that the lateral thrust at each block level does not exceed the shear resistance of the joint. The sliding condition was explained with the concept of friction cone (see Figure 2f). A limiting friction cone is an imaginary inverted right circular cone obtained by revolution of the resultant with respect to the normal reaction making an angle, α with the normal in limiting friction condition (Figure 2e). As long as the resultant force lies within this limiting cone at a certain joint level, the block above is safe against sliding along this joint. The inherent advantage of true arches over corbelled arches was highlighted where the possibility of resultant force being contained within the friction cone is much higher in the case of true arches due to the contact planes being radial. Thus, it was explained why the corbelled arches are more sensitive to support disturbances as compared to true arches and may lose their stability under lateral actions more easily. The study was based on the observation of actual distress in corbelled vaults of Ta Prohm, Cambodia under support rotations caused due to tree root penetration (see Figure 3). FEM based numerical studies carried out by Chandra, Prasad and Menon (2006) on these vaults, with plane stress assumption and non-linear interface elements in the non-linear analysis framework, reinforced the understanding of vulnerability of these systems to support disturbances. Recently, some studies on influence of support settlement problems on dry masonry structures have been carried out by Tralli et al. (2020) where the authors have proposed analytical formulations to model crack pattern and associated failure mechanism in masonry structures. An experimental study on a tilting table test carried out by Grillanda et al. (2021) also throws some light on the influence of settlements on ultimate shear capacity of dry masonry structures in general.