Seismic rehabilitation of cathedral towers in Peru

On June 23, 2001, an earthquake of magnitude 8.3 occurred at 1100 Kms south of Lima and about 250 Kms to the west of Arequipa. The four hundred year-old city of Arequipa, whose historical downtown was declared World Cultural Heritage by UNESCO, is known as the "White City" because most of the city is built with a volcanic stone called "sillar". This kind of stone exhibits a mostly white-gray color. Churches, monasteries and houses are built completely with this stone, which gives the city its characteristic appearance. The cathedral of Arequipa, located in the city's main square, is the most important neo-classical monument of Peru. It has a 100 m-long façade and two towers at the top of the building having a height of 28 m. Due to the effects of the earthquake of 2001, both towers suffered extensive damage. As a consequence, the left tower partially collapsed, whereas, the right tower remained standing but in an unstable equilibrium condition. This paper describes the emergency work performed to stabilize the right tower with an internal steel structure and the process of strengthening and rebuilding of both towers. The left tower was rebuilt with internal reinforced concrete members. The right tower was strengthened with Carbon Fiber Reinforced Polymer (CFRP) laminates, which were used to provide tensile strength and confinement to the central stone core of the tower. After completing the CFRP installation, carved stones were placed on top of the laminates to keep the original appearance.