In this article semi rigid joints of timber structures are analysed which are applied in beam to beam connections. The main design principles of semi rigid timber joints’ are discussed. New type of joint construction for glued laminated timber elements’ is proposed and laboratory experimentally tested. Beam to beam joint is installed using welded steel details which are anchored into timber elements. Steel detail's back T shape part is used for anchoring into timber element. Beam to beam joint is symmetric along the longitudinal element's axis; it has two steel details in tension and compression zones which enable this joint to take axial, shear forces and bending moment. To avoid initial free rotation of the joint; filler is used to ensure contact between glued laminated timber element and steel detail. Cement based filler with polymer fibres is used for this purpose. Three joints with the same geometrical and physical parameters are experimentally tested in four point bending; analyzed connection is in the middle of simply supported beam. Purpose of laboratory experiments is to determine the rotational bearing capacity of the new type joint and to compare these results with theoretical values calculated according to Eurocode 5.
This PhD research provides a detailed procedure for designing and investigating the short term static behaviour of a proposed long span timber floor system for non-residential applications that meets serviceability and ultimate limit design criteria, with the use of timber as the only structural load bearing part of the system. In this study the behaviour of two types of LVL are investigated through a number of experimental and analytical tests. As a result of the tension and compression tests, a suitable constitutive law is developed which can accurately capture the stress-strain relationship and the failure behaviour of LVL, and it can also be incorporated into FE analysis of any LVL beam with similar structural features to the tested specimens. Further, the results of the full scale four point bending tests on LVL sections are used to identify the behaviour of LVL up to the failure point and to develop a finite element model to capture the behaviour and failure of LVL. Moreover, after investigating the long span timber floors, one system is proposed to be fabricated for the extensive experimental and numerical investigation. The results of the full scale experimental tests together with the numerical investigation provide a robust model for predicting the performance of any timber beams with similar structural features to the proposed system while the dimensions and spans can be varied according to special requirements such as dynamic performance or fire resistance requirements.
Moment resisting joint with lagscrewbolts shows good mechanical performance and aesthetic. However, beam and column joints rarely showed a brittle shear failure in a panel zone of a column in previous studies. Therefore, a joint system reinforced by long screws was developed to prevent from the failure in this research. The maximum shear strength of the joint increased with increasing the number of long screws. However, the average of six screws specimens was lower than that of four screws, because the glulam and some of the screws were damaged due to the narrow space between the screws during an inserting process of the screws.
Wood as building material is gaining more and more attention in the 21st century due to its positive attributes such as light weight, renewability, low carbon footprint and fast construction period. Cross-laminated timber (CLT), as one of the new engineered wood products, requires more research emphasis since its mechanical performance can allow CLT to be utilized in massive timber structures. This thesis focuses on revealing one of the key failure mechanisms of CLT, which is usually referred to as the rolling shear failure. The scientific research conducted in this thesis combined both analytical modelling and experimental material testing. The stresses in CLT cross-layers obtained from a finite-element model were analyzed to differentiate various failure modes possible. Tension perpendicular to grain stress was found to cause cross-layer failure in combined with the rolling shear stress. Experimentally, specimens prepared from 5-layer CLT panels were tested under center-point bending condition. Detailed failure mechanism of CLT cross-layers were recorded with high speed camera to capture the instant when initial failure happened. It is evident that some of the specimens failed in tension perpendicular to grain which verified the modelling results. Variables such as the rate of loading and the manufacturing clamping pressure were designed in experiments to compare their influence to the failure of CLT specimens. In this research, the failure of CLT cross-layer was updated to a combined consequence of both rolling shear stress and tension perpendicular to grain stress. Future research topics and product improvement potentials were given by the end of this thesis.
In the last 15 years timber-concrete composite (TCC) systems have gained market share around the world. To facilitate acceptance of this construction method and to set basis for building TCC bridges in the Province of Quebec, the authors conducted a test program on TCC beams with continuous shear connectors. It included push-out...
Since the development of Cross Laminated Timber (CLT), there has been a surge in interest in massive timber buildings. Furthermore, recent conceptual and feasibility designs of massive timber towers of 30 or more stories indicate that performance of mass timber structural elements can compete with other building materials in the commercial industry (MGB Architecture and Design et al.). However, in order for massive timber to penetrate the commercial market even further, a solution is needed for long-span massive timber floor systems. Unfortunately, CLT falls short in this area and is unable to span long distances. The hollow massive timber (HMT) panel presented in this thesis offers one potential long-span solution.
A feasibility study of glulam was carried out in French Guiana using local wood species. The aim was to determine gluing parameters affording satisfactory behaviour to manufactured glulam in a tropical climate. Three abundant wood species, with special properties, were selected for the study and Resorcinol-Phenol-Formaldehyde resin was used for bonding. Three industrial parameters were considered: adhesive spread rate, closed assembly time and gluing pressure. Delamination and shearing tests were carried outin accordance with European Standards. The tests revealed the influence of wood properties and manufacturing parameters on joint resistance. In fact, the results showed that specific gravity and the shrinkage coefficientgreatly influenced the gluing step. Indeed, wood with a medium specific gravity needed more adhesive and more pressure than wood with a high specific gravity. In addition, planning and lamella thicknesswere found to affect glue joint resistance.
The introduction of Cross-laminated Timber (CLT) as an engineered timber product has played a significant role in the considerable progress of timber construction in recent years. Extensive research has been conducted in Europe and more recently in Canada to evaluate the fastening capacity of different types of fasteners in CLT. While ductile capacities calculated using the yield limit equations are quite reliable for fastener resistance in connections, however, they do not take into account the possible brittle failure modes of the connection which could be the governing failure mode in multi-fastener joints. Therefore, a stiffness-based design approach which has already been developed by the authors and verified in LVL, glulam and lumber has been adapted to determine the block-tear out resistance of connections in CLT by considering the effect of perpendicular layers. The comparison between the test results on riveted connections conducted at the University of Auckland (UoA) and at the Karlsruhe Institute of Technology (KIT) and the predictions using the new model and the one developed for uniformly layered timber products show that the proposed model provides higher predictive accuracy and can be used as a design provision to control the brittle failure of wood in CLT connections.
In this thesis the reliability of the design of unreinforced notched beams is evaluated and recommendations for the design of reinforced notched beams are given. The review of design approaches for reinforced notched beams shows, that so far the reinforcement is designed only with regard to the perpendicular to grain force acting in the notch corner. The evaluation of test results from literature shows that a stiff reinforcement has the best reinforcing effect but initial cracking cannot be prevented. The failure behaviour of the reinforced notch is studied in more detail by means of experiments and a FE model. Initial cracking of the reinforced notch comes along with crack opening, whereas ultimate failure with excessive crack growth is accompanied by shearing of the crack. An analytical model is presented for the description of the structural behaviour of reinforced notched beams. The parallel and perpendicular to the grain stiffness of the reinforcement is accounted for in the model. A high stiffness of the reinforcement parallel to the grain is required in order to reduce the mode 1 loading of the notch corner and to prevent initial cracking. The mode 2 loading of the crack increases with increasing crack length. In order to achieve higher load-carrying capacities for notched beams with longer cracks, reinforcement with high stiffness parallel to the grain is required. Recommendations are given for the required reinforcement of notched beams in order to restore the shear capacity of the reduced cross-section.