In the recent years Cross Laminated Timber (CLT) has become an indispensable engineered wood product, especially within Europe. Due to its shear-flexible transverse layers, the calculation method has to capture these effects. Most commonly used approximation methods in practice are the Timoshenko beam theory, the gamma-method and the shear analogy method. Each method has its advantages and shortcomings. A comprehensive study on uniformly loaded multispan beams using the mentioned methods was conducted. It was shown, that at the middle supports (local force introduction) the normal stresses (Timoshenko and gamma method) deviate from the reference solution (2D FE solution). The shear analogy method was able to capture these local effects better than the other employed methods, but with a higher modelling effort (two coupled beam elements). Higher beam theories are a possibility to reduce the modelling and discretization effort and reach a suitable approximation of normal stresses within CLT at middle support areas.
A research study was undertaken to investigate the mechanical performance of glulam beams reinforced by CFRP or bamboo. Local reinforcement is proposed in order to improve the flexural strength of glulam beams. The glulam beam is strengthened in tension and along its sides with the carbon fiber-reinforced polymer CFRP or bamboo. A series of CFRP reinforced glulam beams and bamboo reinforced glulam beams were tested to determine their load-deformation characteristics. Experimental work for evaluating the reinforcing technique is reported here. According to experiment results, the CFRP and bamboo reinforcements led to a higher glulam beam performance. By using CFRP and bamboo reinforcements several improvements in strength may be obtained.
The purpose of this paper is to demonstrate the properties of glued laminated beams made in diverse configurations of timber quality classes, reinforced using a new technique that is cheaper and easy to apply. The aim of the experimental investigations was to enhance reinforcement effectiveness and rigidity of glued laminated beams. The tests consisted of four-point bending of large-scale specimens reinforced with basalt fibres (BFRP). The tests were meant to obtain images of failure, the load–displacement relation and load carrying capacity of basalt fibres depending on the reinforcement ratio. The tests, which concerned low and average quality timber beams, were conducted in a few stages. The aim of the study was to popularize and increase the use of low-quality timber harvested from reafforested areas for structural applications. In the study, theoretical and numerical analysis was carried out for reinforced and unreinforced elements in various configurations of wood quality classes. The aim was to compare the results with the findings of experimental tests. Based on the tests, it was found that the load carrying capacity of beams reinforced with basalt fibre was higher by, respectively, 13% and 20% than that of reference beams, while their rigidity improved by, respectively, 9.99% and 17.13%. The experimental tests confirmed that basalt fibres are an effective structural reinforcement of structural timber with reduced mechanical properties.
IOP Conference Series: Materials Science and Engineering
Currently, FRP fiber composites are increasingly used in construction. They can be used in the form of: tapes, mats and bars. Composite rods are already widely used in reinforced concrete structures as replacements for steel rods. They are also used as elements for repairing various types of structures: reinforced concrete, timber, steel and masonry. It is much less popular to use composite rods as reinforcement elements for laminated timber beams at the production stage. The paper presents the results of experimental and numerical analysis of glued laminated timber beams, reinforced with BFRP basalt-epoxy rods to determine the effect of the distribution of composite reinforcement on the load-bearing capacity of reinforced joists. The tested elements were reinforced with bars of various diameters, arranged differently at the cross-section. The beams were made of GL24h wood, while basalt-epoxy bars with a diameter of 7 and 9 mm were used to strengthen the beams. During the experimental investigations, the deflection of beams, the value of the destructive force and the form of destruction, were investigated. Computer calculations based on the Finite Element Method (FEA) were also obtained, achieving good consistency of displacement results. In numerical studies, wood and composite rods have been modeled as an orthotropic material. The numerical analysis was carried out in the elastic range. In experimental studies, significant differences in the values of deflections and destructive forces in the scope of one research series were observed, which may be due to the inaccuracy of execution. Values of destructive forces in experimental studies were not directly related to the value of reinforcement percentage of different series of beams.
Preliminary results from an experimental program investigating the behaviour of retrofitted glulam beams subjected to static and dynamic loads are presented in this paper. The effect of glass fibre-reinforced-polymer (GFRP) laminates applied on the tension side was investigated under both static and dynamic loading as a potential retrofit on undamaged specimens. Furthermore, previously damaged beams were restored by applying GFRP confinement to the damaged region. The experimental results showed that the capacity of the retrofitted beams was improved significantly and the restored beams attained a significant level of their original dynamic capacity. Future work involves the development of a material predictive model that can account for the high-strain rate effects as well as investigating more retrofit options.
This paper presents preliminary results from an experimental program investigating the dynamic behaviour of glulam beams and columns subjected to simulated blast loads. A total of eight glulam beams and columns were tested destructively under static and dynamic loads. Based on the dynamic tests conducted on the beams, an increase in strength under dynamic loading, relative to that measured under the static loading, was observed. A material predictive model that accounts for high strain-rate effects is developed. The experimental displacement-time histories were reasonably well predicted through a single-degree-of-freedom approach which used the proposed resistance model as input.
Architectural Institute of Japan Structural System
Timber elements, which are different from other structural elements, have a characteristic problem in that the load bearing capacity decreases due to self-burning in the case of a fire, and this self-burning may continue after other fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase, but also the cooling phase. However, in examining the load bearing capacity of timber elements in a fire, few studies have considered the cooling phase. In the present paper, the fire performance of glued, laminated timber beams is discussed based on load-bearing fire tests that take the cooling phase into consideration.
This study investigates the bending and bonding performances of glued laminated timber beams manufactured using a combination of Malaysian lower and higher- grade timber species. Two types of beams were prepared which were mono-species and mixed-species glulam. Mono-species glulam with uniform layup were fabricated using Merpauh, Jelutong and Sesendok. Mixed-species glulam with balanced layup were fabricated whereby Merpauh was positioned equally at the outer layers and either Jelutong or Sesendok were positioned at the inner layers. Three replicates of ten-layered glulam beams measuring 100 mm in width, 300 mm in depth and 6200 mm in length were manufactured according to MS758 for each mono and mixed-species glulam. Bending, delamination and block shear tests were done on all the glulam beams. The results show that glulam manufactured from the combination of Sesendok and Merpauh obtained the highest bending properties and structural efficiency. In addition, the bonding performance at the interface between Sesendok-Merpauh lamellas proved to be excellent.
In der vorliegenden Arbeit wurden die Anwendungsmöglichkeiten von Biegeträgern aus Brettsperrholz bei Beanspruchung in Plattenebene untersucht. Mit Hilfe numerischer und analytischer Methoden wurden die für die Bemessung von Brettsperrholzträgern erforderlichen Ansätze für den Nachweis der Biege- und der Schubtragfähigkeit sowie zur Berechnung der Verformungen entwickelt und hergeleitet.
Journal of Engineering Science and Technology Review
The bridge deck slab and the rectangular beam of the glued-wood beam bridge are connected by bolts and studs; thus, the joint surface is prone to slippage, and the beams and plates experience difficulty in bearing loadings together. This difficulty results in problems, such as stress concentration and screw corrosion and loosening, and weakens structural bearing capacity, stiffness, and integrity. In this study, an experimental model of glued timber T-section beams formed by gluing between bridge decks and rectangular beams and a calculation method for T-beam shear stress were proposed to improve the bearing capacity, stiffness, and integrity of the structure for ensuring that the bridge deck and the rectangular beam jointly bear stress. Three sets of beams, namely orthogonal T-beams, parallel T-beams, and rectangular beams were made using Larix gmelinii larch boards and structural glue to perform static bending bearing capacity test for examining the strain, deflection, and ultimate bearing capacity of the members and observe the destruction pattern. During the test, the bending shear strength was calculated following the principle of equivalent stiffness and the shear strength formula proposed by Rammer. Furthermore, a finite element model of glulam beams based on elastoplastic theory was established using structural analysis software. The displacement, strain, and failure mechanism of the members under the test loads were simulated and analysed using the model to verify the test results. Results demonstrate that, when the three types of beams are bent, they are sheared along the grain near the central axis of the section. The bonding surface between the wing plate and rib of the T-beam is undamaged, and the bonding is reliable with strong structural integrity. Compared with those of rectangular beams, the bearing capacity (limit load), bending stiffness, and ductility coefficient of the parallel T-beams are increased by 71%, 189%, and 23%, respectively. Compared with those of rectangular beams, the bearing capacity, bending stiffness, and ductility coefficient of the orthogonal T-beams are increased by 33%, 28%, and 25%, respectively. Compared with those of rectangular beams, the bearing capacity, bending stiffness, and ductility coefficient of the glulam T-beams are greatly improved. By considering the principle of equivalent stiffness and using the Rammer formula, the shear strength test values of orthogonal T-beams and rectangular beams of glulam deviate from the calculated values by 8.0% and -5.6%, respectively, which indicates good agreement. However, the shear strength test value of the parallel T-beams deviates from the calculated value by 19.2%, which indicates slightly lower calculation accuracy. The finite element analysis is consistent with the results of the experiment. This study provides certain references for the engineering design of glulam T-beams.