Static analysis of the Turris Lybisonis Roman multispan stone arch bridge

It is not easy to determine whether a stone bridge is in danger of collapsing. At present, there is no accepted procedure for determining the load-carrying capacity of a masonry arch bridge. In this paper the multispan stone arch bridge in Portotorres (Sardinia, Italy) named Turns Lybisonis is examined. The bridge, built in the 1st century A.D., was still in service into the 20th century. Using the upper-bound theory of plasticity in conjunction with geometrical compatibility criteria to obtain the solutions, three types of failure are considered: hinging, in which a space opens between two stones in the arch, sliding, in which a stone slips out of place, and a combination of hinging and sliding. The numerical results obtained by application of the recent Ring software are described. The effects of various parameters, such as material crushing, applied loading according to Italian law .... etc. on the collapse mechanism are investigated.