Wood-based solutions to improve quality and safety against seismic events in conservation of historical buildings

Historical buildings can be highly vulnerable to earthquakes if In-Plane strength and stiffness of floors and roofs are not sufficient to limit Out-Of-Plane deformation of walls and to transmit the seismic forces among walls efficiently. In fact, floors and roofs in existing masonry buildings are normally realized with timber beams, purlins and a single layer of timber boards, and their In-Plane stiffness can be limited when subjected to shear forces. Various retrofitting techniques are available, whose effectiveness can be very different and not easily predictable theoretically. In this paper, the behavior of different strengthening criteria for historical buildings, involving the use of wood and wood based products, is illustrated and critically discussed. Code provisions, design rules and calculation methods for strengthening interventions are described. In-Plane behavior of floor and roof structures and their interaction and connection to the seismic resistant wall systems are considered. Finally, a case study of restoration intervention on a historic barn is presented, which was damaged during the 2012 earthquake in Emilia. The illustration is focused on the improvement of the whole safety of the construction by means of specifically designed interventions on the wooden roof.