@article {1872, title = { A Calculation Method for Interconnected Timber Elements Using Wood-Wood Connections }, journal = {BUILDINGS}, volume = {10}, year = {2020}, abstract = {

Wood-wood connections, widely used in the past, have been progressively replaced by steel fasteners in timber constructions. Currently, they can be manufactured and implemented more efficiently thanks to digital fabrication techniques. In addition, with the emergence of new timber plate engineered products, digitally produced wood-wood connections have been developed with a strong focus on complex free-form geometries. The gained knowledge through research and building implementations have pushed the development of more standardized structural elements. As a result, this work presents a new concept of building components using through tenon connections based on the idea of transportable flat-packs directly delivered and assembled on site. The main objective of this research is to develop a convenient calculation model for practice that can capture the semi-rigid behavior of the connections and predict the effective bending stiffness of such structural elements. A case study is used as a reference with three large-scale slabs of a 8.1 m span. Bending and vibration tests are performed to study the mechanical behavior and assess the proposed calculation method. The results show the high influence of the semi-rigid behavior of connections on the bending properties and, therefore, on the serviceability limit state. The model is in good agreement with the test results, and further improvements can be made regarding the local behavior of the connection. This study demonstrates the feasibility of the proposed construction system and the applicability of the developed calculation model to design practice.

}, author = {J. GAMERRO and J.F. BOCQUET and Y. WEINAND} } @article {1849, title = { Experimental investigations on the load-carrying capacity of digitally produced wood-wood connections }, journal = { ENGINEERING STRUCTURES }, volume = {213}, year = {2020}, abstract = {

The rise of digital fabrication has increased the use of wood-wood connections inspired by traditional carpentry in modern timber constructions. With recent developments on standard construction systems, the mechanical behavior of such joints for in-plane loading configurations is an essential parameter for the structural design. However, only few design guidelines exist on this topic in building codes such as Eurocode 5 and research has been mainly focused on the rotational behavior, which is important for free-form structures. Therefore, this work presents an experimental campaign on the load-carrying capacity of digitally produced through tenon connections for commonly available engineered timber products such as oriented strand board, laminated veneer lumber, and multiply solid wood panels. Shear and compression failure modes were studied and two test setups were developed. The scope of the study was limited to five different materials, a grain orientation parallel to the joint, and three different tenon lengths. The test results showed significant differences between the product specifications given by manufacturers and real performances observed for oriented strand board and cross laminated timber, while laminated veneer lumber had more accurate specifications. Nonetheless, a spreading of the compression strength was highlighted only for the OSB material and was also observed for the shear strength of laminated veneer lumber specimens. The existing Eurocode 5 guidelines generally underestimated the load-carrying capacity of the connections by 25\% and only the capacity of oriented strand board connections was overestimated. Finally, the study demonstrates that different design approaches can be defined according to the material employed in through tenon connections. Design diagrams based on tests are preferred for materials with a high variability between product specifications and real performances while design criteria from building codes can be applied for the others.

}, author = {J. GAMERRO and J.F. BOCQUET and Y. WEINAND} } @article {1671, title = { Mechanical behaviour of pre-stressed spruce timber-timber 2.5-mm-step grooved connections under shearing tests }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {75}, year = {2017}, pages = {719-727}, abstract = {

A smart shear connection system was tested in order to be used in manufactured elements of a lattice of wooden slats and a cross offset. This type of floor element can present advantages both in terms of weight and suitable insulating filler (Adalberth et al. 2001; Kawasaki and Kawai 2006; Kermani and Hairstans 2006; Dodoo et al. 2014). This connection is made to provide a substitute for a glue connection. The shear connection proposed is made by double-sided grooving timber interfaces to form a cross section. A specifically designed test assembly was constructed to measure and guarantee homogeneous contact pressure in interface test specimens. Shear test results are presented and compared in terms of capacity and stiffness with glue connections. The principal conclusions are as follows: the allowable shearing resistance of the grooved timber-timber joints can approximately reach the resistance of glued connections. The stiffness of the joints is improved by increasing the pre-stress applied for holding contact in the assembly. The grooved timber-to-timber joints exhibit non-linear behaviour which dominates the behaviour of the whole system. Therefore, the behaviour of a unit connection must be determined to obtain the mean load-carrying capacity and stiffness of a system with grooved connections.

}, url = {https://hal.univ-lorraine.fr/LERMAB-UL/hal-02176944}, author = {S. GIRARDON and J.F. BOCQUET} } @article {1676, title = { Modelling mechanical properties of spruce and Douglas fir timber by means of X-ray and grain angle measurements for strength grading purpose }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {75}, year = {2017}, pages = {527-541}, abstract = {

This study proposes a model using data from a scanner (X-ray and grain angle measurements) to perform strength grading. The research also includes global measurements of modulus of elasticity (obtained by vibrations and ultrasound methods), static bending stiffness and bending strength of 805 boards of Douglas fir and 437 boards of spruce. This model can be used in an industrial context since it requires low computational time. The results of this study show that the developed model gives better results than the global non-destructive measurements of the elastic modulus commonly used in the industry. It also shows that this improvement is particularly higher in the case of Douglas fir than for spruce. The comparison has been made on both the quality of the mechanical properties assessment and on the improvement of the grading process according to the European standards by using different index.

}, url = {https://hal.univ-lorraine.fr/LERMAB-UL/hal-01530963}, author = {J. VIGUIER and D. BOURREAU and J.F. BOCQUET and G. POT and L. BL{\'E}RON and J.D. LANVIN} } @article {1668, title = { Predicting the beech wood decay and strength loss in-ground }, journal = { INTERNATIONAL BIODETERIORATION \& BIODEGRADATION }, volume = {123}, year = {2017}, pages = {96-105}, abstract = {

In the context of reduction of CO2 emissions and costs in the construction industry, substitution of concrete by wood for foundation piles seems to be a promising alternative. To promote the use of local wood in pile foundation, diagnostic and prediction methodology of wood decay in soil need to be improved. Outdoor mesocosm decay experiments were performed to evaluate the potential use of beech wood as foundation piles. The stochastic occurrence of soil fungal inoculum in contact with mini-stakes and water gradient in wood explained the observed patchy wood decay pattern. Various patterns of wood rotting fungi were identified. The correlation between measured strength loss and mass loss was weak. Multivariate analyses using biochemical and physico-chemical data as inputs allowed section categorizations and prediction of wood strength. Accuracy of the prediction was validated by experimental measurement of the compression parallel to the grain (f(c),(o)).The categorization of unknown sections was computed by PLS-DA and provided clues inferring their service life. The described procedure has the potential to be transferred to on-site measurements to predict the f(c,o) of wood foundation pile or any potentially damaged timber structure.

}, author = {Q. KLEINDIENST and A. BESSERER and M.L. ANTOINE and C. PERRIN and J.F. BOCQUET and L. BL{\'E}RON} } @article {1547, title = {Reinforcement of dowel type connections}, journal = {CONSTRUCTION AND BUILDING MATERIALS}, volume = {97}, year = {2015}, pages = {48-54}, abstract = {

A good design of dowel type fastener connections is essential to ensure safe designs for the whole structure and cost effective solutions. With reinforced connections, engineers can achieve better capacity of the connection and safer designs by increasing the ductility of the connection (so-called \"capacity design\" with a ductile connection to be the weak point). This paper presents an overview of the reinforcement of dowel type connections. Most of the failures encountered in dowel type connections occur because of an excess of shear stresses or tensile stresses perpendicular to the grain in the connection area. Because of the large amount of situations and reinforcement techniques, this report mainly focuses on the reinforcement of dowel-type connections when the dowels are mainly loaded parallel to the grain. For such connections, modes of failure of un-reinforced and reinforced connections, updated design models and the effect of the reinforcement on the ductility of the connection will be presented. Among the various types of reinforcement techniques available, nowadays, self-tapping screws have found a wide field of application and they will be the main focus of this report.

}, author = {D. LATHUILLIERE and L. BL{\'E}RON and T. DESCAMPS and J.F. BOCQUET} } @article {1564, title = { Spreading of transverse compressive stresses in glued laminated timber }, journal = { EUROPEAN JOURNAL OF WOOD AND WOOD PRODUCTS }, volume = {73}, year = {2015}, pages = {475-484}, abstract = {

This paper presents a new approach for understanding localized compressive behavior perpendicular to the grain based on beams subjected to three-point bending. It was intended to take into account the coupling between compressive stresses perpendicular to the grain due to support reactions and shear stresses. To validate this, model, results of compression tests have been examined. The digital image correlation (DIC) method has been applied in order to analyze the deformation fields in support areas. The tests allow confirming the presence of spreading effect in the vicinity of support areas according to the DIC method. An analytical formulation has therefore been proposed to quantify distribution versus increasing compressive strength perpendicular to the grain, including shear effects. A scale effect and support conditions have also been highlighted using three different geometries and two types of tests.

}, url = {https://hal.univ-lorraine.fr/LERMAB-UL/hal-01599802}, author = {D. LATHUILLIERE and O. POP and L. BL{\'E}RON and F. DUBOIS and F. FOUCHAL and J.F. BOCQUET} }