Laurent Van Parys

Development of a Specific Finite Element for Timber Joint Modeling

Widely used for light frame structures or for heavy laminated wood structures, dowel-type fasteners are the most commonly used kind of connectors in timber construction. The purpose of this work is to develop a tool for the semi-rigid analysis and design of such joints. Firstly, interests and approaches described in literature for the semi-rigid modeling of timber plane frames are summarized. Secondly, for a better understanding of the problem, the main characteristics of wood used as a structural material are presented. Finally, a method for an efficient study of joints built with dowel-type fasteners is proposed and developed. This method consists of the introduction of a specific finite element called “Finite Semi-Rigid Element (FSRE)” between the ends of the jointed members. This joint element consists of two nodes, each with three degrees of freedom. These nodes will be tied with common beamelements during the FE analysis. The stiffness of the FSRE is computed from the geometry of the joints and embedding stiffness of all fasteners, along and perpendicular to the grain. The embedding characteristics of fasteners are defined with help of their experimental load-slip curves (fitted with Foschis models) leading finally to the resolution of a FE non-linear problem.

Refurbishment of existing timber floors with screwed CLT panels

ABSTRACT A well-known, light, and almost reversiblere furbishment solution for existing timber floors is the use of a top timber flange connected to the joists to build up a “new” composite. This article proposes an improvement of that technique by using a cross-laminated timber (CLT) flange connected to the joists with inclined self-tapping screws. The use of an additional gap between the CLT and the existing joists contributes to increase the bending stiffness too. The inner gap is fixed by timber blocks resistant in compression but non-efficient in bending. These blocks act with the inclined screws to behave as a Pratt truss. An analytical model of the refurbishment is presented and a design example is discussed. Different configurations are finally introduced and compared to highlight pros and cons of the technique.

Engineering and Patrimonial Buildings: Rewarding Interdisciplinary Work

The Our Lady Cathedral of Tournai in Belgium has been recognized in 2000 by UNESCO as a World Heritage site. However, today several parts of the Cathedral exhibit signs of weaknesses and interventions are needed. This article deals with the interdisciplinary approach followed for the study of the frameworks of the Cathedral. According to the historical study, the roof has exhibited different roofing materials throughout the ages. To make the contemporary architectural choices for the restoration, preliminary studies were initiated. Indeed, for the 800-year old frameworks of the transept, specific attention is needed to ensure that the substitution of the slate roofing by thick lead slates will not cause additional damages or pathologies. Through the study led by historians, archaeologists and engineers, this article gives a global overview of the preliminary studies performed by specialists in what could be considered as a good example of a rewarding interdisciplinary work. A special focus is made here on the work provided by engineers to understand all the specific problems of such a building and to propose respectful, efficient, and consistent solutions. The structural study of the Cathedral frameworks is mainly developed here coupled with on-site investigations and information led by historians and archaeologists to enlighten the structural behavior of the building.

Proposal of a CLT Reinforcement of Old Timber Floors

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.