San Lorenzo Cathedral, Perugia, Italy

The San Lorenzo Cathedral was built between the 14th and 15th century. Already in 1633-1641, important consolidation works had been carried out, since the columns and the walls had diverged due to the weight of the roof. Seismic movements in 1983 caused further damage, thus endangering the stability of the monument. A new consolidation and restoration project was decided after a thorough historical survey of the original and subsequent static behavior of the structure. The twenty-three timber roof trusses were reinforced by strengthening the joints with steel plates and bolts and by prestressing both the lower tie beam and the central king post with two twin Ø36 mm DYWIDAG Bars (THREADBAR ^® ) each.

The column capitals showed displacements of up to 26 cm. A new system of transverse and longitudinal ties made of DYWIDAG Bars (THREADBAR ^®) was introduced into the columns and walls to prevent any side displacements. The transverse tie members were prestressed and tied back to the lateral walls in order to apply to the whole structure a system of acting forces capable of counteracting the thrusts of the vaults.