Catenary arch of finite thickness as the optimal arch shape

Based on the analogy with the load path of a homogeneous hanging chain, catenary has been for over three centuries considered to be an ideal masonry arch's shape. In the present research, after the thrust line theory, complete insight into the equilibrium analysis of catenary arch of finite thickness under its own weight is provided. It is concluded that, in accordance with the common criterion-the existence of only normal (axial) forces-the ideality has previously been unjustifiably attached to such an arch, since there are shear forces present as well. However, with respect to so-called Couplet-Heyman's assumptions (unilateral rigid no-tension material), it is shown that any catenary arch is stable under its own weight.