Repair and Strengthening of Traditional Timber Roof and Floor Structures

Abstract

In many countries, traditional buildings comprise timber roof and floor structures. Most of these structures are degraded from different causes and need to be repaired or strengthened to ensure current and/or to fulfil the requirements of a new use of the building. Current knowledge assumes the need to preserve and to protect existing timber structural systems as a cultural value, with important advantages to the overall behaviour of the building. This growing sensibility towards the preservation and maintenance of heritage buildings has led researchers to study different repair and strengthening solutions. In the case of timber roof structures, this strengthening in many cases involves the connections between the roof structural members. Joint strengthening can be done with different methods, traditional or modern ones, using well-chosen materials, simple techniques or more sophisticated ones: from simple replacement or addition of new fasteners, to the use of timber or metal elements, glued composites, or even full injection with fluid adhesives. Each solution has advantages and disadvantages concerning conservation philosophy, architecture, aesthetics, construction issues and moreover unique consequences in engineering terms for the joint final strength, stiffness and ductility. All the above have to be evaluated in order the proper intervention to be chosen for each case. The main problem of existing timber floors is their low stiffness, which results in high bending deformations and vibrations under service loads. Permanent deflection due to creep can also reach critical values. Moreover, in earthquake prone areas, if seismic resistance has to be assured in existing masonry buildings, both roof and floor diaphragm behaviour must be achieved. This chapter aims to present a state-of-the-art review mainly on strengthening solutions for timber roof and floor structures, focusing on the most promising techniques taken into account the level of intrusion and reversibility. “Dry” interventions, based on timber or timber based elements will be highlighted.