Proposal of a CLT Reinforcement of Old Timber Floors

Abstract

Despite the fact that, from the mechanical point of view, there is no ageing issues of timber elements when they are properly used, many old timber structures require important interventions because of changes in uses (which modifies the regulating rules for example), of material decay (misuse of timber) or possibly of a faulty design or construction. In particular, timber floors in old structures often present large deflections and most the time had been designed for a maximum load much lower than the one prescribed by contemporary rules. After an introduction about timber floors and a short review about the reinforcement technics that exist, the present paper presents a new proposal for their reinforcement. The solution developed in the present paper uses a Cross Laminated Timber (CLT) panel screwed over the existing floor, keeping a small gap between the panel and the existing joists. In this way, the new "composite" floor presents higher stiffness and the gap is used for horizontal line runs. For the design of such a "composite floor", modified Johanssen's equations (including the gap between the CLT panel and the joists) are proposed and their application on a case study is presented.

The CLT Panels in Structural Restoration: Characteristics and Technical Regulations

“…Willing to investigate the possible applications in the structural restoration field, was noted that these panels have often been used for the refurbishment and reinforcement of existing wooden floors and roofs [5,6,7,8,9,10,11,12,13].…”

“…These structural wood-based panels are to date widely used in the structural reinforce of the timber floors in order to increase their strength to the actions that operate in their own plan [5,6,7,8,9,10,11,12,13]. It is considered essential to better know the mechanical properties and laws that govern the behaviour of this material subjected to stress, in order to evaluate the possibility of extending its use to other field of application.…”

The Influence of the Geometrical Features on the Seismic Response of Historical Churches Reinforced by Different Cross Lam Roof-Solutions

“…Recently, the realization of dissipative wooden roof-diaphragm represents another valid option to avoid the out-ofplane mechanisms and to reduce the in-plane shear actions on the seismic resistant elements (Longarini et al, 2019), obtaining a controlled rocking behavior of the perimeter walls opportunely coupled with the dissipative roof-diaphragm. The diaphragm can be realized with wooden planks having different orientation with respect to the original one (Parisi and Piazza 2015) or by precast solution of Cross Laminated Timber (CLT) panels overlaying the original wooden trusses and planks and creating wood-to-wood composite sections (Gubana 2010;Gubana 2015, Roensmaens 2019). In several experimental tests and numerical analyses, the system composed by CLT panels with steel connections has provided adequate in-plane stiffness able to guarantee the floor diaphragm effect (Gubana and Melotto 2018; Longarini et al 2018).…”

Evaluation of the Seismic Behavior of Historical Churches Reinforced by Cross-Lam Roof-Structures

“…Several wooden based roofdiaphragm configurations can be realized [25,26,27]. One of these is based on the use of Cross Laminated Timber (CLT) panels characterized by an alternated sequence of glued timber layers [28,29,30]. This kind of panels have been initially adopted in new timber buildings [31][32][33][34] but, in several experimental tests and numerical analyses, they have shown enough in-plane stiffness able to guarantee the floor diaphragm effect especially if the panels are over-placed on the existing wooden beams or planks creating wood-to-wood composite sections [35,36,37].…”