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About this book

By presenting the work of the RILEM Technical Committee 245-RTE, the book provides an overview of the existing techniques for the reinforcement of timber elements, joints and structures. It consists of two parts: part I examines state-of-the-art information on reinforcement techniques, summarizes the current status of standardization, and covers STS, GiR, FRP and nanotechnology. In part II several applications of reinforcement are discussed: these include traditional structures, traditional timber frame walls, light-frame shear walls, roofs, floors, and carpentry joints.

The book will benefit academics, practitioners, industry and standardization committees interested in the reinforcement of existing timber elements, joints and structures.

Table of Contents


Reinforcement of Timber Elements in Existing Structures

Wood and engineered wood products, herein also referred to as timber, have been used as structural building material for centuries and countless examples demonstrate its longevity if properly designed, built, maintained and assessed [1, 2]. The more recent development of new engineered wood products, connector systems and growing awareness about sustainability in the construction sector have led to legislative changes in the building sector and as a consequence also a significant widening in the range of structural applications of timber [3, 4].
Thomas Tannert, Philipp Dietsch, Jorge Branco

Self-tapping Screws as Reinforcement for Structural Timber Elements

The use of self-tapping screws is a state-of-the-art practice in fastener and reinforcement technologies for timber structures. The high axial stiffness and load-carrying capacity of self-tapping screws, together with their easy handling, make them one of the most economical choices for applications in both fastener and reinforcement domains. This chapter focuses on mechanical models for timber members reinforced with self-tapping screws and the material properties of self-tapping screws and screwed-in threaded rods. Furthermore, the behaviour of reinforced timber members under shrinkage is discussed.
Philipp Dietsch, Andreas Ringhofer

Glued-in Rods as Reinforcement for Timber Structural Elements

Glued-in rods are important connecting and reinforcing elements in modern timber engineering used in new and existing timber structures. The complex stress distribution along the bondline between rod and wood depends on the type and properties of the adhesive and the type of load application. In this chapter, different models for the determination of the shear stress distribution along the bondline are discussed and their effects on the stress distribution and strength of the glued-in rod are evaluated. Important points on how to enhance the load-carrying capacity and reach best structural capacity, as well as the ductile failure behaviour, are discussed.
Robert Jockwer, Erik Serrano

Fiber-Reinforced Polymers as Reinforcement for Timber Structural Elements

This chapter provides a comprehensive summary of recent developments in the use of fiber-reinforced polymers (FRP) as reinforcement for timber elements and joints. The constituents of FRP composites are first introduced. Next, the typical applications of FRP in the reinforcement of wood elements and joints are discussed. The long-term performance of adhesively bonded FRP-reinforced wood structures under different environmental effects (i.e. moisture, temperature, coupled moisture and temperature, and fire) are reviewed and discussed. Furthermore, the in situ quality control for the bonding of FRP to wood substrate and the assessment of FRP-reinforced wood structures are described. Finally, perspectives on the application of such systems are given.
Bo Kasal, Libo Yan

Nanocomposites as Reinforcement for Timber Structural Elements

This chapter presents an overview of recent technological innovations in nanocomposite materials for protection and reinforcement of timber in construction. Starting from the definition of nanotechnologies applied in the field of construction and architectural heritage, the chapter briefly describes nano-materials available in the market. The role of different nano-coatings, their wood surface protection functions, and their compatibility with different wood species are reviewed. On-going experimental research projects for next-generation application fields are presented with a special focus on reinforcement of historic timber joints.
Clara Bertolini-Cestari, Tanja Marzi

Reinforcement of Timber Structures: Standardization Towards a New Section for EC 5

The reinforcement of timber structures has seen considerable research and development in recent years. New materials and methods for reinforcement have been developed and are now used in practice. Current design standards, however, lack specific guidance to design reinforcements for timber members and joints. To close this gap in the new generation of Eurocode 5, CEN/TC 250/SC 5, the standardization committee responsible for drafting the European Timber Design standard, has decided to establish a Working Group 7 “Reinforcement” on this item. This chapter presents the approach to this task, the work items, the work plan, the structure as well as the design approaches, and related background information for the proposed Eurocode 5 section.
Philipp Dietsch

Seismic Reinforcement of Traditional Timber Structures

Every year earthquakes cause damage and destroy a sizeable portion of the building stock across the globe. Among traditional constructions, those built with timber are considered the most effective earthquake-resistant structures, provided that the continuity in the load path is not compromised, the joints are intact, and moisture-induced problems are kept at bay. However, the high costs and difficulties involved in the execution of interventions that meet the safety requirements prescribed by current building codes act as a deterrent to the continued use and reuse of these structures. Therefore, it is important to identify the inherent seismic-resistant features, as well as the deficiencies, of traditional timber constructions and to review the various strengthening, retrofitting and upgrading measures that have been developed to enhance the safety of such structures. The effectiveness of different strengthening techniques has been proven on the basis of results from experimental tests carried out on components of timber structures, such as joints and beams, full-scale shear walls, roof trusses and floor slabs. The successes and failures of past interventions also play an instrumental role in identifying effective and economical strengthening solutions for traditional timber structures.
Chrysl A. Aranha, Jorge M. Branco

Reinforcement of Traditional Timber Frame Walls

Timber frame walls are common structural elements adopted in many countries for different purposes. They constitute an important cultural heritage of different parts of the world and the necessity often arises to intervene in such structures for their preservation. Different strengthening techniques have been adopted when retrofitting timber frame walls, some traditional and others more innovative. As the response of the walls, particularly to horizontal actions, is governed by their connections, retrofitting is usually concentrated at the joints, but interventions can also be carried out on timber members or on infill. In this chapter, an overview of possible retrofitting techniques is presented, focusing on their advantages and disadvantages and their effects on the overall behaviour of the wall. The presented solutions focus mainly on experimental and in situ interventions performed for seismic purposes.
Elisa Poletti, Graça Vasconcelos, Marco Jorge

Reinforcement of Light-Frame Wood Structures

Recent post-earthquake evaluations of the performance of light-frame wood buildings have pointed out a number of deficiencies that may make such buildings susceptible to high levels of damage and collapse in a seismic event. This chapter focuses, firstly, on defining the deficiencies that are common in light-frame wood structures, including weak first storey, weak roof or floor diaphragms, shear walls with insufficient strength, inadequate load path, geometric and mass eccentricities, and brittle components. Subsequently, the chapter describes conventional as well as state-of-the-art retrofit solutions that are available in specific codes and guidelines.
Marisa Mulder, Michael Fairhurst, Thomas Tannert

Reinforcement of Historic Timber Roofs

This chapter aims to present a comprehensive report on the reinforcement of historic timber roofs, focusing on their main characteristics, advantages and disadvantages, which would help professionals select and define the design of reinforcement solutions. Cultural heritage issues are taken into consideration. Reinforcement can be done via different methods—traditional and modern—using simple or sophisticated techniques. An overview of the main materials and the techniques used for selected case studies are presented, illustrating how various reinforcement methods are implemented in practice.
Eleftheria Tsakanika, Jorge M. Branco

Retrofitting of Traditional Timber Floors

Timber floors are a critical component of many historical and modern buildings. Due to incorrect design and construction, effects of deterioration, change in use, and/or functional requirements, these components frequently need to be retrofitted. This chapter reviews the need for retrofitting of existing timber floors and critically evaluates a range of methods to improve their strength and stiffness, both in-plane and out-of-plane. The review of the available literature shows that this is a very active area of research and, in spite of the enormous progress achieved in the last decades, suggests that new and better methods will be developed in the future.
Luis C. Neves, Ivan Giongo

Reinforcement of Traditional Carpentry Joints

This chapter focuses on the reinforcement of traditional timber carpentry joints according to different standards, recommendations, case studies, as well as analytical, numerical and experimental research works. The aim of the review is to present the state-of-the-art methodologies that can be at the disposal of carpenters, architects and engineers. In order to understand how traditional carpentry joints, work and their failure mechanisms, such as compressive crushing, shear and tensile cracks, six geometrical typologies of such joints are discussed. Finally, for the above typologies, several reinforcement strategies are presented by defining their objectives, methodologies, traditional and contemporary techniques, performance criteria and applicability areas. When assessing and reinforcing traditional carpentry joints, some challenges may come up, namely their design, based on the ratios of stiffness and load-bearing capacities. These challenges should thus be a focal point for further research in the near future.
Jorge M. Branco, Maxime Verbist, Eleftheria Tsakanika
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