René Steiger

Empa - Swiss Federal Laboratories for Materials Science and Technology | Empa · Department of Structural Engineering

Bonded-in profiled rods are among the most efficient fasteners in modern timber construction. Especially under axial loading, they are characterised by high load-carrying capacity and high stiffness. In addition, connections with steel rods can be designed to exhibit ductile failure, so that the brittle failure modes of wood in connections and rein...

Image-based local fibre direction data, generated based on the analysis of the medullary spindle pattern, were used to improve the prediction of the tensile strength parallel to the grain of European beech (Fagus sylvatica L.) boards. An approach to characterise the local fibre orientations in a board using a single numerical grading parameter was...

Das Holz der Rotbuche (Fagus sylvatica L.) wird gegenwärtig nur in sehr geringem Maße für die Produktion von Brettschichtholz (BSH) verwendet. Obwohl diese in Mitteleuropa am weitesten verbreitete Laubholzart ein sehr hohes Potenzial hinsichtlich Festigkeit und Steifigkeit besitzt, wurde sie, neben dem Einsatz im Bahnbau (Schwellen), bisher überwie...

Sheathed timber frame shear walls (STFSW) with strong anchorage have recently been studied to be used as the main lateral force resisting system in timber buildings. The first part of this research project highlighted the enhancement of the shear stiffness and strength of the STFSWs with strong anchorage in comparison with the established configura...

This paper presents the results of extensive investigations on the lamination strength grading, the production and the mechanical properties of European beech (Fagus sylvatica L.) glued laminated timber (GLT). Based on the analysis of potential influencing parameters on strength and stiffness as well as subsequent tension tests parallel to the grai...

This article presents experimental and numerical investigations on the buckling behaviour of glulam columns made of European beech (Fagus sylvatica L.) timber and a design proposal. First, the compressive strength parallel to the grain (f_c,0) and the modulus of elasticity parallel to the grain (E_c,0) were experimentally determined in tests on sto...

Significant developments in structural health monitoring (SHM) and in non-destructive testing (NDT) and damage identification techniques for structural timber elements have led to an increasing interest in the application of these technologies. However, specific aspects of timber structures (anisotropy, moisture dependency, high variability), the w...

Content of the paper: • Overview of robustness-related provisions in the Eurocodes and other relevant standards • Discussion of the requirements and design methods to design for robustness • Presentation of the proposed approach for robustness for the 2nd-generation EN 1995-1-1 Eurocode 5

The paper reports and discusses full-scale test results of beech GLT timber columns of various slenderness ratios and strength classes and checks the validity of the formulae currently implemented in Eurocode 5. Firstly, the compression strength and the modulus of elasticity parallel to the grain of short beech GLT columns was determined according...

Amounting to an 18% share of the timber stock, European beech (Fagus sylvatica L.) is the dominant hardwood species in Swiss forests, followed by ash (4%) and maple (3%). Since the construction sector has been identified as an interesting field of application for beech wood, in 2015 the Swiss Federal Office for the Environment launched a research p...

One of the common lateral load resisting systems in multi-story timber buildings in Central Europe are reinforced concrete shear walls. The RC shear walls are not optimal for timber buildings for several reasons such as: (i) the difference in tolerance between concrete and timber construction procedures, (ii) elevated construction time caused by ne...

A newly developed non-contact method to identify and quantify the fibre orientation in European beech wood (Fagus sylvatica L.) was used to estimate the tensile strength of timber boards. The developed approach is based on an automated visual analysis of the spindle pattern formed by the medullary rays, also called wood rays. Each spindle is identi...

In this paper, the results of extensive experimental and numerical studies on the bending behaviour of glued laminated timber beams made from European beech wood (Fagus sylvatica L.) are reported and discussed. A total number of 5740 European beech timber boards from four Swiss sawmills were strength graded, systematically examined and documented,...

This paper introduces a non-contact method for the identification, quantification, and documentation of fibre direction of European beech wood (Fagus sylvatica L.). The developed approach is based on an automated visual analysis of the spindle pattern formed by the medullary rays, also termed wood rays. Each spindle is identified by means of image...

The paper presents experimental investigations of friction properties (a) between adjacent sheathing panels made of Oriented Strand Board (OSB) and (b) between OSB panels and glued laminated timber (GLT) frame members as they occur, for example, between parts of light-frame timber shear walls. The friction stresses are evaluated for different level...

This paper presents an analytical model of timber-concrete composite slabs made of laminated veneer lumber (LVL) with notched connection. Timber-concrete composite slabs could be used as alternative to timber slabs or conventional reinforced concrete slabs and represent an interesting solution due to ecologic, economic and structural advantages. Th...

In timber–concrete composite members with notched connections, the notches act as the shear connections between the timber and the concrete part, and have to carry the shear flow necessary for composite action. The shear transfer through the notches generates shear and tensile stresses in both parts of the composite member, which may lead to brittl...

A 3-storey residential building with OSB-sheathed light-frame timber walls and timber-concrete composite slabs was subjected to dynamic excitation in two different stages of construction. The experiments consisted of measurements of the accelerations resulting from forced horizontal vibrations which were excited by means of a hydraulic actuator sha...

Abstract This paper describes experimental investigations on timber-concrete composite members made of beech laminated veneer lumber (LVL) with notched connection. Timber-concrete composite slabs represent interesting building solutions, and can substitute conventional reinforced concrete slabs and timber slabs. LVL based materials have controllabl...

Fracture propagating along the grain of timber is one of the most relevant failure mechanisms due to the wood’s low strength and its brittle failure behaviour when subjected to excessive shear and tensile stresses perpendicular to the grain. According to the current procedures, the fracture energy of wood is determined on small clear specimens. How...

Norway spruce glulam beams with artificial horizontal slits of different length and depth were reinforced using self-tapping screws and threaded steel rods in order to restore their load-carrying capacity and stiffness. The study aimed at evaluating the effects of strength and stiffness of the applied reinforcing elements on the load-carrying capac...

A 3-storey residential building with OSB-sheathed light-frame timber walls and timber-concrete composite slabs was subjected to dynamic excitation in two different stages of construction. The experiments consisted of measurements of the accelerations resulting from forced horizontal vibrations which were excited by means of a hydraulic actuator. Th...

In the present paper, several visual and physical strength and stiffness related indicators are investigated concerning their influence on the tensile strength and stiffness of European beech timber boards. Besides well-known visual characteristics, such as knots and bark inclusions, further ones are analysed. Destructive tensile tests on 150 timbe...

This paper presents an experimental and analytical investigation on the application of laminated veneer lumber (LVL) made of European beech wood (fagus sylvatica L.) in timber truss structures. Particular focus is laid on developing improved design approaches for dowel-type connections and on promoting ductile failure behaviour, as the connections...

A 3-storey residential building with OSB-sheathed light-frame timber walls and timber-concrete composite slabs was subjected to dynamic excitation in two different stages of construction. The experiments consisted of measurements of the accelerations resulting from forced horizontal vibrations which were excited by means of a hydraulic actuator. Th...

Like in several other countries in Central Europe, the share of European beech (Fagus sylvatica L.) in the Swiss forests is very high and steadily growing due to forest policy and the progressing climate change. This timber species is nowadays primarily used in furniture and for heating, but its use in the construction industry is very promising. T...

Full-scale on-site dynamic experiments on timber buildings have not been carried out often so far. In Switzerland, recently the unique opportunity arose to investigate the dynamic properties of a 3-storey residential light-frame timber building (LFTB). The building is covered by a rafter roof with clay tiles and supported by a structure consisting...

Impressive large span constructions are more often realized in timber or engineered wood products over the past years. For example, glulam beams provide the possibility for the use of timber in halls, bridges and multi storey buildings. The limitation in span of solid timber members was lifted due to glulam production. But the environmental conditi...

In post-tensioned timber frames beams and columns are connected by means of a tendon. The tendon presses the beams against the columns which leads to a stress situation where beams are loaded parallel to the grain and columns are loaded perpendicular to the grain. These kind of wood to wood connections are semi-rigid and can therefore resist bendin...

The structural behaviour and failure mechanisms of unreinforced and reinforced notched glulam beams were studied in a test series. It could be shown that shear failure of the reinforced notched beam is an important failure mechanism and that adequate reinforcement in tension perpendicular to grain and shear is required in order to regain the load-c...

In this paper different design approaches for connections loaded perpendicular to the grain are evaluated with regard to their reliability. The structural behaviour of connections loaded perpendicular to the grain is described based on existing experimental and theoretical studies. The detailed failure behaviour of dowel connections loaded perpendi...

The impact of knots and grain deviations on the perpendicular to grain strength of wood was studied by computational models and test results from literature. It was found that knots in general seem to have a positive influence on the perpendicular to grain fracture strength. A strongest link model for strength analysis relating to failure due crack...

The structural behaviour of timber members subjected to axial compression or combined axial compression and bending is characterised by a non-linear increase of the deformations due to geometric and physical non-linearity. The geometric non-linear behaviour results from an increasing eccentricity of the axial load (P-delta effect). The physical non...

The research and development of connecting and strengthening timber structural elements with glued-in rods (GiR) has been ongoing since the 1980s. Despite many successful applications in practice, agreement regarding design criteria has not been reached. This state-of-the-art review summarises results from both research and practical applications r...

Glued-in rods (GiR) have been successfully used for both constructing new and strengthening existing timber structures. The research and development of connecting and strengthening timber structural elements with GiR has been going on since the 1980s. However, agreement regarding design criteria for these applications has not been reached. Today, s...

Des mesures effectuées durant la construction d’un immeuble à ossature en bois laissent supposer que la rigidité admise lors du dimensionnement de ce type de bâtiment est parfois sous-estimée, ce qui peut avoir des conséquences importantes pour leur résistance aux efforts horizontaux.

In factory production control (FPC) of gluedlaminated timber the integrity of glue lines according to product standards has to be checked by carrying out either delamination or block shear tests. The chosen test method should provide reliable and reproducible results, and from a practical point of view should be as cheap and easy to perform as poss...

Designers regularly are involved in the assessment and retrofitting of existing structures. This task, compared to the design of new structures, is completely different and, in order to find suitable and economic solutions should follow a specific format. Decisions on maintenance interventions have to be taken based on all the available information...

The behaviour of timber members subjected to axial compression or combined axial compression and bending is characterised by the non-linear increase of the deformation due to the increasing eccentricity of the axial load and due to the non-linear material behaviour. The paper presents a strain-based model taking into account these effects.Design ap...

In order to benefit from the advantages of fully threaded self-tapping screws as reinforcing elements, it is essential to have detailed knowledge about the strength and stiffness of screws with different shank to grain angles subjected to combined axial and lateral loading. In this paper a design model is proposed for the calculation of the load-ca...

Despite its higher strength and stiffness properties as compared to most softwood species, beech wood is today almost entirely used for energetic purposes or non-structural applications. Benefitting from elevated mechanical properties and a reliable high degree of homogeneity, Laminated Veneer Lumber (LVL) made of beech has a great potential for ap...

The paper describes tests carried out on structural glued laminated timber (glulam) beams and finger-jointed boards made out of thermally modified hardwood (beech, fagus sylvatica) in the following named as TMTB. The finger joints were bonded with a two-component PRF adhesive and the lamellas were edge-bonded using a two-component MUF adhesive. The...

Notches are details that significantly reduce the load-carrying capacity of beams made of timber. The amount of reduction was the subject of investigation in numerous studies from an experimental or theoretical point of view. The singular stress distribution around the notch corner can be described by equations based on linear elastic fracture mech...

p>The present paper describes collapses and failures of three large-span roof structures in Switzerland: In February 2009 the steel roof of a three years old gym in eastern Switzerland collapsed. Based on visual findings and on a detailed investigation it could be found that the cause of the collapse was a deficient detailing in each of the seven...

Für höher beanspruchte Verbindungen im Holzbau reichen die neu entwickelten langen, aber relativ dünnen Vollgewindeschrauben nicht aus. Seit drei Jahrzehnten ist es jedoch möglich, mit profilierten Stahlstäben oder Gewindestangen grosse Kräfte in Holzbauteile, insbesondere aus Brettschichtholz, zu übertragen. Bis heute ist die Verbindungstechnik mi...

The use of thermally modified timber for structural purposes is of increasing interest. In order to guarantee sufficient reliability in terms of load bearing capacity and fitness for use the strength and stiffness properties of this modified wood have to be assessed. Industrially produced, thermally modified structural timber members made of beech...

The load carrying capacity of glued laminated timber beams is reduced considerably by notches at the support on the tension side of the beam. Stress concentrations at the notch corner together with low shear and perpendicular to the grain tensile strength may lead to brittle failure. For the prediction of the load carrying capacity of notched beams...

The design of cross-laminated solid timber (CLT) as load-bearing plates is mainly governed by serviceability criterions like maximal deflection and susceptibility to vibration. Hence, predicting the respective behavior of such plates requires accurate information about their elastic properties. According to product standards, the bending stiffness...

Timber bridges with decks made of laminated solid timber panels are usually protected against mechanical abrasion and humidity with a mastic asphalt pavement. Recent laboratory tests suggested that the pavement may have a significant effect on the stiffness and damping of a footbridge. Currently, however, in the design of footbridges, this asphalt...

Structures are planned and designed to fulfill certain requirements in regard to the safety of the users and in regard to the reliability of the fulfillment of the purpose of the structures over the prospected service life. The fulfillment of these requirements is often understood as the performance of the structure. Usually the design follows the...

Adhesive joints have been known and applied for timber structures for decades. Hybrid joints with glued-in rods are nowadays successfully used for both constructing new and strengthening existing timber structures. Since the 1980s the research and development of timber joints with bonded-in rods have been going on, however agreement regarding desig...

The bending and shear stiffness of cross-laminated timber (CLT) made from softwood depend on the moisture content of the panel. In principle, the stiffness properties drop with increasing moisture content within the hygroscopic range. However, swelling provokes closing of open gaps of the middle layers and leads to an apparent increase of stiffness...

Since timber bridges are light-weight structures with a high life-load to death-load ratio, they are susceptible to vibration and thus satisfying vibration serviceability is a governing design criterion. A good knowledge of the damping properties of timber bridges is therefore a key aspect for guaranteeing a sufficient serviceability. Since observa...

In quality control of glulam, shear testing of bondlines is required. However, in relevant standards the method of applying shear stress to the bondline is only exemplified by a principle schematic. Based on this schematic a considerable variety of test equipments is in use nowadays. Depending on the respective construction of the test equipment as...