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Glulam members strengthened by carbon fibre reinforcement
Abstract
Glulam members often become large in cross section where heavy loads should be carried. In some applications this may cause
problems if limitations on height are posed. A possible solution is to reinforce the member by e.g. bonding fibre reinforced
polymer (FRP) on the beams or between the glulam lamellas. The aim of this paper is to investigate the possibility of strengthening
glulam beams by the use of pultruded rectangular carbon fibre rods and to establish the anchoring length for this system.
Tests were performed in three different series completed by a reference series, 10 specimens altogether. All tests were performed
as short-term experiments in four-point bending. The experimental results were compared to analytical models in several aspects.
The overall capacity of the beam was established using an analogy with concrete beams. Special attention was made to establishing
the anchoring length of the reinforcement bar, since this is governing to avoid premature failures. The anchorage length was
tested and an analytical model established. The agreement between the analytical critical anchoring length and the test result
was satisfactory. The proposed reinforcement method increased the short-term flexural load-carrying capacity by 49–63% on
average.
... Studies [16] were conducted on glued-laminated beams (3000×90×225 mm) to compare options for CFRP reinforcement with lamellas and rods. At the same time, variants with different locations of reinforcement were tested: along the lower face and at some distance from the lower face. ...
... Studies [6][7][8][9][10][11][12][13][14][15][16][17][18] show that the reinforcement with CFRP materials, in general, increases the strength and stiffness of timber beams. However, in the above studies, the strengthening of medium-sized timber elements made of solid wood reinforced with plates and rods is not fully disclosed, so conducting such a study is expedient. ...
... To achieve the goal, the following tasks should be solved: -to determine the "deflection-load" dependences for the studied samples; 16 -to investigate the stress distribution along the height of the cross-section of the beams and the failure patterns of the samples; ...
This study reports the results of experiments comparing the effect of structural reinforcement for timber beams strengthened with different carbon composite materials. Samples of one series were strengthened by gluing a carbon fiber plate from the outside to the face of the beam. The samples of the other series were strengthened by laterally gluing two carbon fiber rods inside the beam. According to the bending research program, the ultimate loads and deflections were determined for both series. As a result of the analysis of the results and comparison with unreinforced samples from the control series, the effect of beam reinforcement and the model of their destruction were determined. Studies have shown that the effect of external reinforcement with a plate was 86.7 % according to the criterion of full failure load, 20.5 % according to the criterion of ultimate load, 13.4 % according to the criterion of ultimate deflection. The effect of rod reinforcement was 48.6 %, 18.6 %, and 4.1 %, respectively. The theoretical analysis of the results showed a convergence of up to 8.2 % with the experimental results. External reinforcement with a plate compared to lateral gluing of rods showed better results due to the placement of the plate in the zone of maximum tensile stresses. This arrangement more effectively limited the spread of ultimate stresses and the development of cracks. The reinforcement parameters of the samples (materials, placement, percentage of reinforcement) were selected under the condition of the same theoretically predicted bearing capacity after reinforcement. However, comparative experimental studies have revealed differences in the processes of deformation and destruction of reinforced beams. The results will contribute to making rational project decisions and for choosing a relevant technique of strengthening timber beams with carbon composite materials
... As a result, glulam products are stiffer and more rigid than typical lumber products, as shown in Figure 1. As can be observed, glulam has a greater average strength (f m ); in addition, the characteristic strength (f k ) increases and the variance decreases [4,5]. ...
... Johnsson et al. investigated glulam timber members reinforced by carbon fiber-reinforced polymer (CFRP) rods between the glulam lamellas. They indicated that NSM reinforcing technique enhanced the ultimate moment capacity by about 49-63% [5]. ...
... The linear elastic stage and plastic stage of cross-section analysis of the RG beam with reinforcement in tension and compressive zones are presented in Figure 13. By introducing an initial small value of strain in the outermost fiber in compressive zone ε ci , the neutral axis is achieved according to the load stage using strain compatibility and force equilibrium equations (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19). a) Within the linear elastic stage: strain compatibility includes ...
Reinforcing the wooden structural members is considered as a challenging matter to overcome the drawbacks of using wood in the construction field. The current investigation, therefore, presents an attempt to evaluate the effectiveness of utilizing steel bars as reinforcements in glulam timber beams using the near-surface-mounted (NSM) technique in conjunction with carbon fiber-reinforced polymer (CFRP) sheet wraps. A series of flexural testing was carried out until failure for both reinforced and unreinforced glulam members in a simple support system. Eleven specimens were examined in two groups to compare them with the control beam. Five reinforced glulam (RG) beams of the first group were reinforced with different schemes at tension and compression zones using the same bar size. The other five specimens of the second group were reinforced with shear reinforcement using fully wrapped strips made of CFRP sheet in addition to the same flexural reinforcement schemes as the first group. Each glulam beam has a span of 1.35 m and a rectangular section sized 85 mm × 175 mm. Based on experimental outcomes, theoretic modeling was provided to estimate the ultimate load capacity and bending rigidity of reinforcing glulam members. Though several theoretical predictions of flexural capacity were overstated when compared to experimental predictions, these disparities were frequently about 10%, confirming that the proposed theoretical model was accurate, and the mean of ultimate loading capacity and deflection between experimental and theoretical results were 1.01 and 1.09, respectively. Experimental results presented show that the RG beams performed much better than the unreinforced reference beams in terms of structural behavior, with improvements in ultimate load capacity ranging from 16 to 49%. On the other hand, the shear reinforcement for RG members slightly improved flexural performance, and the ultimate load capacity increased by 2–7%. Therefore, it was concluded that the NSM techniques using ordinary steel bars were effective ways in strengthening the glulam members in terms of flexural stiffness with increasing ultimate load capacity.
... [345] and timber e.g. [340,346] Selected examples of single-shear test (EBR and NSM) are shown in Figure 35. ...
... A typical test setup consists of FRP bonded to the fixed substrate; however, in some cases, a set of two substrate elements is used. [346] In the single-lap shear test, the effective bond length can be assessed; however, it must be ensured that the test set-up prevents the joint from transverse displacement which may introduce additional bending moments and cause premature failure. In the typical tests, a displacement is imposed directly to the FRP or via a secondary substrate member. ...
... In the typical tests, a displacement is imposed directly to the FRP or via a secondary substrate member. [346] In the reviewed studies, different methods to collect experimental data are used. Typically, a load cell for measuring the applied force and a set of linear variable differential transformers (LVDTs) to measure the relative displacement between the FRP and the substrate (slip) are used, while load and free ends' slip are registered. ...
The development of new adhesives has allowed to expand the application of bonding into the most diverse industrial fields. This review article presents the commonly used experimental methods for the investigation of mechanical performance of adhesively bonded joints in the aerospace, wind energy, automotive and civil engineering sectors. In these sectors, due to their excellent intrinsic properties, composite materials are often used along with conventional materials such as steel, concrete and aluminium. In this context, and due to the limitations that the traditional joining techniques present, adhesive joints are an excellent alternative. However, standardized experimental procedures are not always applicable for testing representative adhesive joints in these industries. Lack of relevant regulations across the different fields is often overcome by the academia and companies’ own regulations and standards. Additional costs are thus mitigated to the industrial sectors in relation with the certification process which effectively can deprive even the biggest companies from promoting adhesive bonding. To ensure continuous growth of the adhesive bonding field the new international standards, focusing on actual adhesive joints’ performance rather than on specific application of adhesive joints are necessary.
... NSM technique in strengthening timber structures was introduced recently and therefore its application is mainly based on the literature [13]. Research studies on the use of NSM FRP reinforcement demonstrated increased flexural strength and stiffness of the timber beams [14][15][16][17]. Long-term research on the flexural strength has also shown the potential of the NSM technique [18]. ...
... Epoxy adhesives are commonly used as the filler for the NSM structures [14], as they exhibit excellent bond quality at the interfacial regions resulting in higher capacities [19,50] and were therefore applied in this study. Epoxy adhesives have been reported to have higher and better gap-filling capacities compared to conventional adhesives [50]. ...
... It is noted that each beam configuration was replicated 3 -5 times. Similar replicates have been used by previous researchers such as [14], [18], [20]. Figure 3 shows the fabrication process of the NSM FRP specimens. ...
Near Surface Mounted (NSM) fibre reinforced polymer (FRP) bars is an effective technique of improving the performance of timber beams. Despite the potential of NSM technique, literature remains limited, whilst there is not any standard method for the prediction of the NSM FRP timber flexural capacity. Extending the pool of experimental data and thus the understanding of FRP strengthened timber structures, the present paper reports an experimental study of timber beams reinforced with glass and basalt FRP bars. Moreover, the paper presents a general theoretical model in order to estimate the moment resistance of the NSM FRP timber beams. The experimental study examined white spruce timber specimens in two reinforcement configurations; one with reinforcement bars only on the tension zone and one with reinforcement bars both on the tension and the compression zone. Control specimens were also included for comparison purposes. All beams had a rectangular cross-section of 70 × 215 mm and were loaded under four-point bending configuration with a 2.3 m span. A total of 20 specimens were tested under displacement control quasi-static monotonic loading. The main failure mechanism observed for both NSM FRP reinforced and unreinforced specimens was brittle tensile failure of the timber at the tensile zone. The load–deflection curves, the strain distribution profiles and the failure modes were discussed. It was observed that a significant increase on the ultimate load (33–69%) and the flexural stiffness (22–33%) of the timber beams can be achieved due to the NSM reinforcement. The proposed theoretical model for the ultimate strength of NSM FRP strengthened timber beams is assessed on the basis of the test results and collated data, showing a good comparison between the experimental and theoretical results.
... Many studies consider the use of reinforcing FRP pultruded rods. [18][19][20] Borri et al. 18 compared the use of externally adhered CFRP pultruded laminates on the tension zone located at the corners of the drawer bottom of the wooden beams. More precisely, they used one or two rods put into slits in the tension zone. ...
... The use of one or two pultruded rods introduced in slots made from the outside, within the tension area, was proposed by Johnsson et al. 19 for glulam beams. The increase in load capacity was obtained between 44% and 63%. ...
... In the literature, the test elements' length is generally between 1.5 and 4 m. 11,13,[15][16][17][18][19]22,24,27,29,33 The length of the wooden beams was chosen as 1710 mm considering the experiment setup. Glulam layers are used while preparing these beams. ...
In the last 20 years, the use of wooden structures and their dimensions have gradually increased. The wood application has increased in different structures such as multistory buildings, sports, industrial facilities, road and railway bridges, power transmission lines, and towers. The widespread use and size of wood structures have increased the research on developing special types of wood products supported by composite materials. Laminated wood elements are the leading composite wood materials. Laminated wooden beams allow making much larger openings than standard solid wood structural elements. The development of the sizes and usage areas of wooden structures has increased the capacity of glulam structural elements and reveals the need to improve their performance. Carbon fiber reinforced polymers (CFRPs) are the most suitable options for increasing the bearing capacity values of glulam beams and improving general load–displacement behaviors. In this study, the use of CFRP strips in different layouts to increase glulam wooden beams and the application of CFRP fan-type anchors in the CFRP strip endpoints are the studied variables. Anchored and non-anchored glulam wooden beams reinforced with CFRP strips with different layouts were tested using a three-point bending test. The ultimate load capacity, initial stiffness, displacement ductility ratio, energy dissipation capacity, failure mechanisms, and general load–displacement behavior of wooden beam test specimens were obtained and interpreted as a result of the experiments.
... Many studies consider the use of reinforcing FRP pultruded rods. [18][19][20] Borri et al. 18 compared the use of externally adhered CFRP pultruded laminates on the tension zone located at the corners of the drawer bottom of the wooden beams. More precisely, they used one or two rods put into slits in the tension zone. ...
... The use of one or two pultruded rods introduced in slots made from the outside, within the tension area, was proposed by Johnsson et al. 19 for glulam beams. The increase in load capacity was obtained between 44% and 63%. ...
... In the literature, the test elements' length is generally between 1.5 and 4 m. 11,13,[15][16][17][18][19]22,24,27,29,33 The length of the wooden beams was chosen as 1710 mm considering the experiment setup. Glulam layers are used while preparing these beams. ...
... Unfortunately, the linear orthotropic model is only useful in the linear range. Non-linear stress-strain relationships are needed beyond that, particularly in the compression region where numerous other variants, such as completely plastic, have been utilized (e.g., [38,66]), bilinear (e.g., [11,54,100]), higher-order (e.g., [101]). Ref. [102] presented a tri-linear stress-strain diagram to analyze the failure behaviour of wood under compression parallel to the grain, see Figure 2. Furthermore, a bilinear anisotropic stress-strain relationship was proposed by Hill that may be used to predict the orthotropic linear elastic-quasi-rigid behaviour in tension and orthotropic linear elastic-perfectly plastic or bilinear behaviour in compression [103][104][105][106]. (a) linearity in tension and nonlinearity in compression, e.g., at [46], (b) multilinearity in compression, e.g., at [30,37], (c) compression parallel to grain as suggested by [104], (d) elastic and perfectly plastic in compression, e.g., at [107]. ...
... The influence of externally bonded CFRP lamellas on the stiffness and capacity increase of timber beams was introduced in another study; the stiffness increase was not recognized, and a comparison of the theoretical to the experimental wood-to-CFRP modulus of elasticity ratio revealed a significant variability [47]. A 10% increase in stiffness was reported, as well as a 44-60% increase in capacity [100]. The results demonstrate that introducing bidirectional carbon fabric to timber beams resulted in a considerable improvement in bending shear capacity and a minimal increase in beam stiffness. ...
The application of fibre-reinforced polymers (FRP) for strengthening timber structures has proven its efficiency in enhancing load-bearing capacity and, in some cases, the stiffness of structural elements, thus providing cost-effective and competitive alternatives both in new design and retrofitting existing historical buildings. Over the last few decades, several reinforcing materials and techniques evolved, and considerable progress was made in numerical modelling, especially using the finite element method. As this field of research has become extensive and diversified, as well as numerous contradicting results have emerged, a thorough review is necessary. This manuscript covers the topics of historical preliminaries, reinforcing with carbon and glass fibre composites, bond characteristics, main reinforcing techniques, modelling of knots, and the effects of the fibre waviness on the composite behaviour. A detailed overview is given on the experimental and numerical investigation of mechanics of strengthened beams. A one-of-a-kind table is presented that compares the stiffness improvement observed in several studies with analytical estimates. Attention is drawn to a number of challenges that have arisen, e.g., the moderate stiffness enhancement, composite-to-wood interface, modelling of knots, and strengthening of defected timber members. This paper can be used as a starting point for future research and engineering projects.
... Johnsson w swojej pracy [53] zbadał trzy sposoby rozmieszczenia prętów zbrojeniowych typu CFRP. Wszystkie montowane były w najniższej lameli drewna klejonego poprzez wklejanie we wcześniej przygotowane bruzdy. ...
... Rys. 2.18. Układy analizowane przez autorów Johnssona [53] i Rafterego [54,55] Rys. 2.19. ...
Nowadays, various industries use composites. Combining materials with unique properties allows to optimise the elements and adjust their strength to the expected loads. Literature describes diverse materials compositions. In this study, the analyses include connecting wood with a carbon fibre reinforced polymer using a polyurethane glue.
The literature review focuses on the methods of wood modelling, glued joint behaviour in composites containing wood, and the possibilities of strengthening or reinforcing elements using fibre composites in a polymer matrix. Contrary to this work, other scientists test composites bonded with glue other than polyure-thane. Individual studies, describing the modelling methods do not take into account many important properties. A detailed approach to the above topic may allow predicting the actual behaviour of a construction element.
The major aim of this dissertation is to develop solutions enabling creating advanced computational models of full-section girders made of wood-CFRP composite. Implementing laboratory tests on many samples, produced under the technological regime by a certified manufacturer of glued laminated timber, and various measurement techniques, allows to get reliable results. Three stages verify the computer models and analyses, based on the Finite Element Method (FEM).
The first step is creating and validating the model of a wooden lamella. Tested objects are small and structural size bent samples. The second stage is developing a numerical model of a double-lap connection, with a theoretical solution and individual laboratory tests. In most of the found publications, re-searchers ignore phenomena taking place in the joints. Determining the cohesive stiffness and the possibility of delamination enables to include them. Wood-CFRP joint has shown near two times less stiffness and strength than the wood-wood joint. It affects the effectiveness of the reinforcement and determines its location. Considering the connections between the elements as a perfect may lead to a significant increase in the stiffness of the structural element. The last step is developing the non-linear numerical model of large-scale girders with a full cross-section. It bases on the data collected from the earlier stages and laboratory tests carried out on glued structural-sized beams. Exploitation of the FEM model includes determining the linear-elastic stiffness of the designed girders, predicting the destructive force and analysing composites in systems other than those presented in this paper. The only condition is a full cross-section of the girders.
Added feature is developing a simplified model by modifying the solution based on the equivalent cross-sectional area. Adjusting the calculation formulas to laboratory tests and the FEM model makes it possible to do calculations and present recommendations for the design of structures made of wood-CFRP composites.
The conducted laboratory tests and computer analyses are a valuable source of knowledge about the major phenomena occurring in fibre-reinforced wood-polymer composites. They allow to predict the actual behaviour of structural elements during bending.
... Numerous studies have been conducted based on a wide range of different reinforcement concepts. In these studies, a variety of reinforced materials and positions in the beam have been used such as steel strands (Bohannan 1964), fiberreinforced plastic (Plevris and Triantafillou 1992), glass fibers (Fiorelli and Dias 2006), steel tendons (Mcconnell et al. 2014), steel plates (Usman and Sugiri 2015), CFRP plates (Glišović et al. 2015) and FRP bars (Johnsson et al. 2006, Yang et al. 2016. Both reinforcements with no pretensioning (here denoted passive reinforcements) and pretensioned reinforcements (here denoted active reinforcements) have been tried. ...
... The reinforcement of the tension side affected and changed the failure mode of the passively reinforced beams compared to the reference beams (Johnsson et al. 2006). The passively reinforced beams showed a linear elastic behavior up to a specific load (initial yield load) where the behavior shifted into a non-linear and ductile behavior, see Figure 6. ...
When glued-laminated timber are subjected to bending moment, they usually fail in a brittle way in the tension zone before the compressive zone reaches the compressive strength of wood. This means that the compression strength of wood is not fully exploited. By reinforcing the tension zone, the failure mode of glued-laminated timber can be changed from tensile to compressive. As a result, by utilizing the higher compressive strength, reinforced glued-laminated timber become stronger and the failure mode becomes compressive and ductile. This paper presents experimental results of the effect of steel reinforcements in the tension zone of glued-laminated timber. Four passively reinforced beams, four actively reinforced beams, and seven unreinforced beams were tested to failure in four-point bending tests. The experimental results confirmed the brittle tension failure in the unreinforced beams as well as the ductile and compressive failure in the reinforced beams. Furthermore, the experiments revealed the increase of the passively and the actively reinforced glued-laminated timber relative to the reference beams for strengths (26% and 39%) and stiffnesses (30% and 11%). Ductilities were increased from 7.7% for the reference beams to 90% and 75% for the passively and the actively reinforced glued-laminated timber, respectively.
... The use of three layers of carbon fiber gave an increase in bending strength of 60.3% compared to unreinforced beams. In addition, FRP composite material in the form of CFRP bars [11] was also used as a near-surface reinforcement (NSMR). The NSMR method does not increase the cross-sectional height, and protects the reinforcement from external damage. ...
... 11 22where: After determining the neutral axis of the strengthened element cross-section, the moment of inertia z I of the equivalent cross-section using the Steiner theorem can be calculated using the formula: where: ...
This article presents experimental results from the bending of technical-scale models of beams reinforced in the tension zone with CFRP (Carbon Fiber Reinforced Polymers) materials, with a focus on the benefits resulting from the increased ductility in the tension zone of these beams. In experimental tests, the mechanical properties of reinforced beams were compared with unreinforced beams in terms of the maximum load, deflection, images of damage, stiffness, and distribution of deformation. The results showed that the proposed reinforcement solution was advantageous due to its strength and stiffness, and the safety of the structure. Based on this analysis, it was concluded that the reinforcement of wood with CFRP materials has a positive effect on the behavior and safety of structures. Also, a method of analytical checking of strengthened beams with small cross-sections was presented in the article.
... Although extensive research has been done on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited number of studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Reinforcement with fiber reinforced polymers (FRP) is among the methods commonly used to repair existing wooden structures or to create high-performance structures in newly constructed wooden structures [21] . ...
... Although extensive researches have been made on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . In addition, regional reinforcement studies have been carried out to increase shear strength perpendicular to the fibers [23,39,40] and perpendicular to the fibers [41] . ...
Wood material can be demolished over time due to different environmental factors. Structural elements may need to be strengthened over time as a result of possible natural disasters or during use. Beams are elements under load in the direction perpendicular to their axes. Therefore, they are basically under the effect of bending. When the studies on the behavior of beams against bending test are examined, it is known that the bottom surface of the material generally breaks. For this reason, fiber reinforced polymers (FRP) materials have been used in recent years to reinforce beam members. It is a scientific fact that it is necessary to prefer FRPs for the solution of this problem, as well as their properties such as lightness, corrosion and flexibility, their application without disrupting the appearance of wood. In this study, it was aimed to investigate the effect of reinforcing wooden beams with fiber reinforced polymer materials with different properties on different bending behaviors such as load bearing capacity, ductility, mod-ulus of elasticity. It was observed that the ductility and bearing capacity of wooden beams reinforced with fiber reinforced polymer materials increased significantly compared to non-reinforced beams.
... Although extensive research has been done on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited number of studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Reinforcement with fiber reinforced polymers (FRP) is among the methods commonly used to repair existing wooden structures or to create high-performance structures in newly constructed wooden structures [21] . ...
... Although extensive researches have been made on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . In addition, regional reinforcement studies have been carried out to increase shear strength perpendicular to the fibers [23,39,40] and perpendicular to the fibers [41] . ...
Wood material can be demolished over time due to different environmental factors. Structural elements may need to be strengthened over time as a result of possible natural disasters or during use. Beams are elements under load in the direction perpendicular to their axes. Therefore, they are basically under the effect of bending. When the studies on the behavior of beams against bending test are examined, it is known that the bottom surface of the material generally breaks. For this reason, fiber reinforced polymers (FRP) materials have been used in recent years to reinforce beam members. It is a scientific fact that it is necessary to prefer FRPs for the solution of this problem, as well as their properties such as lightness, corrosion and flexibility, their application without disrupting the appearance of wood.
In this study, it was aimed to investigate the effect of reinforcing wooden beams with fiber reinforced polymer materials with different properties on different bending behaviors such as load bearing capacity, ductility, modulus of elasticity. It was observed that the ductility and bearing capacity of wooden beams reinforced with fiber reinforced polymer materials increased significantly compared to non-reinforced beams.
... Although extensive research has been done on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited number of studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . Reinforcement with fiber reinforced polymers (FRP) is among the methods commonly used to repair existing wooden structures or to create high-performance structures in newly constructed wooden structures [21] . ...
... Although extensive researches have been made on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry structural elements, there are limited studies on their application in wooden structures. The majority of current studies are focused on strengthening against bending [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] . In addition, regional reinforcement studies have been carried out to increase shear strength perpendicular to the fibers [23,39,40] and perpendicular to the fibers [41] . ...
Wood material can be demolished over time due to different environmental factors. Structural elements may need to be strengthened over time as a result of possible natural disasters or during use. Beams are elements under load in the direction perpendicular to their axes. Therefore, they are basically under the effect of bending. When the studies on the behavior of beams against bending test are examined, it is known that the bottom surface of the material generally breaks. For this reason, fiber reinforced polymers (FRP) materials have been used in recent years to reinforce beam members. It is a scientific fact that it is necessary to prefer FRPs for the solution of this problem, as well as their properties such as lightness, corrosion and flexibility, their application without disrupting the appearance of wood. In this study, it was aimed to investigate the effect of reinforcing wooden beams with fiber reinforced polymer materials with different properties on different bending behaviors such as load bearing capacity, ductility, mod-ulus of elasticity. It was observed that the ductility and bearing capacity of wooden beams reinforced with fiber reinforced polymer materials increased significantly compared to non-reinforced beams.
... By comparison with concrete, steel and masonry, the application of FRP to timber structures has been limited although there is a growing collection of literature of an experimental nature on the subject (e.g. [4][5][6][7][8][9][10][11][12][13][14] ). There is clearly, however, a distinct lack of numerical investigations of FRP-strengthened timber structures. ...
... A selection of numerical studies related to strengthening of timber is provided in references [15][16][17][18][19][20] . It is significant to note that the majority of existing literature on the application of FRP to timber materials is limited to timber beams [4][5][6][7][8][9][10][11][12][13] although there are limited applications to other types of structural components [14] . It is also significant to note from previous studies that the timber beams are strengthened in a virgin undamaged state and tested under monotonic loading. ...
The integrity of moment-resisting timber framed structures can be compromised in a seismic event due to damage of the joint region. Externally bonded carbon fibre-reinforced polymer (CFRP) composites offers an effective retrofit strategy for such joints and the concept has been proven in a limited number of experimental studies to date. There is a, however, a distinct lack of numerical modelling studies of the system. This paper therefore reports the numerical modelling of the hysteresis behaviour of FRP-strengthened moment-resisting timber joints utilising the finite element method. Three types of joints are investigated, namely (1) plain unstrengthened joints, (2) FRP-strengthened joints that do not experience degradation in strength, and (3) FRP-strengthened joints with strength degradation. The joints are subjected to a displacement controlled cyclic load and the moment-rotation responses are extracted from the finite element results. In addition, the dissipated energy of each joint relative to the joint rotation is also provided. The modelling procedure is shown to be effective upon comparison with test results when the joint rotation is within an acceptable range of seismic activity.
... The capacity of the CFRP-jointed glulam beams was found almost the same as that of the monolithic glulam beams. Johnsson et al. [41] tested the bending performance of glulam beams reinforced by pultruded CFRP rods, and proposed an approach for estimating the critical anchoring length (i.e., the minimum anchoring length for attaining the maximum force transfer in a reinforcement system) of the rods. Alam et al. [42] tested the flexural properties of spruce beams reinforced by CFRP or GFRP rods. ...
... Based on such an ultimate limit scheme, Borri et al. [57] conducted an analytical investigation on the bending behavior of CFRP reinforced old wood beams; furthermore, a non-linear analytical method for predicting their flexural stiffness or strength was developed, whereby both horizontal and rotational equilibriums were maintained for the cross sections. Using this non-linear analytical method, Johnsson et al. [41] investigated the flexural stiffness or strength of glulam reinforced by CFRP rods. In Johnsson's analysis, a fictive glulam cross section was studied (i.e., transformed section analysis), which was transformed by locally enlarging the width nearby the reinforcement using the CFRP-to-wood stiffness ratio. ...
Both wood and bamboo are renewable anisotropic materials with a long application history in human society. Engineered wood or bamboo aiming to mitigate the variability of the natural material can provide better material properties and structural performance, compared to original sawn lumber or raw bamboo. In this paper, a state-of-the-art review was conducted on three types of novel engineered wood composites, namely fiber reinforced polymer (FRP) reinforced glulam, cross-laminated timber (CLT), and wood scrimber, as well as three types of novel engineered bamboo composites, namely laminated bamboo lumber (LBL), glued-laminated bamboo (glubam), and bamboo scrimber, with particular attentions to their manufacturing technologies, modeling approaches, and mechanical properties. Then, for these novel engineered wood/bamboo composites, a comprehensive comparison was conducted on their mechanical properties and on their densities. Finally, several cases of structural applications were respectively illustrated, in which these aforementioned engineered wood/bamboo composites were adopted as main building materials. Potentials of applying these engineered wood/bamboo composites for structures were confirmed, and their possible existing drawbacks were also discussed.
... The five-layer hybrid-reinforced wooden arch specimen (5FF) exhibited a similar load-carrying capacity; however, it increased the displacement by 61% by demonstrating high ductility and toughness. FRP reinforcement is important for enhancing these properties (Johnsson et al., 2007;Lopez-Anido and Xu, 2002). The placement. ...
... Separating of the section in longitudinal direction between cracks may cause the shear failure in the structure for this case. Johnsson et al. (2007) have exhibited NSM method to enhance flexural strength of glulam using CFRP. Flexural capacity of the beams was analyzed by using a transformed cross section of concrete beams' analogy based on model developed by Borri et al. (2005) and Gilfillan et al. (2003). ...
Fiber-reinforced polymer (FRP) composites have been used over few decades for structural repair and strengthening schemes for structural element but only optimized the applications recently. This paper presents a concise state-of-art review of the extensive research on reinforcing techniques using FRP for construction applications in civil engineering for last two decades. This review was focusing in flexural strengthening techniques applied for concrete, metal and timber structures by experimental and numerical analytical programs. The experimental specimens used by researchers vary from the existing elements structure and new invention for laboratory program only. Data and information collected in this review were gathered from the previous researches all over the world with some of them are applied to the real applications at construction sites. The review hoped to be a good reference and guidelines for all engineers and researches in fields of composites material especially fiber-reinforced polymer to enhance the application of FRP for new construction or rehabilitation of existing structure.
... As a result of this study, it was determined that the flexural properties of the ash beam reinforced with basalt-based fiber-reinforced polymer composites were better than the reference samples. Johnsson et al. (2007) evaluated a total of ten specimens under four-point flexural from three different series of glulam beams reinforced with rectangular pultruded CFRP bars. The experimental results were compared with analytical models in several aspects. ...
Heat treatment is one of the environmentally friendly methods applied to improve the structural properties of wooden materials. While heat treatment improves some properties of wood material, it also negatively affects its mechanical properties depending on the heat treatment conditions applied. The decrease in mechanical properties due to heat treatment limits the use of wood material in various applications requiring mechanical strength. For this purpose, various fiber-reinforced polymers have been used in recent years. In this study, it was aimed to experimentally and numerically examine the flexural properties of unheat-treated and heat-treated black pine ( Pinus nigra Arnold.) wood reinforced 1, 2 and 3 times with carbon, glass and aramid. Following the experimental flexural tests, the samples were modeled and analyzed in the finite element software program. The average flexural strength of the heat-treated sample is 11.72% lower, and the elasticity modulus is 1.23% lower than the unheat-treated sample.It has been determined that carbon-based polymer fabrics, among fiber-reinforced polymer fabrics, have the best reinforcement effect. The flexural strength of the UHT-C-3 sample is 6.1% and the elasticity modulus is 3.52% higher than the UHT-C-1 coded sample. Compared to the sample without reinforcement, flexural strength increased by 30% and elasticity modulus increased by 7%. It is seen that as the number of fiber reinforced polymer layers increases, the flexural properties also increase. When the experimental and numerical analysis results were examined, the flexural strength and modulus of elasticity values gave similar results at the R ² : 0.88–0.99 level. In addition to technologies using kinds of reinforcement evaluated in conservation applications, it may be utilized for numerical analysis in the field of repairing or reinforcing different grades, patterns, and types of reinforcement in already-existing wooden structures.
... They used the joint test results as the basis for a local bond-slip model. A total of 10 specimens from three distinct series of glulam beams reinforced with rectangular pultruded CFRP bars were tested by Johnsson et al. (2006) under four-point bending. In a number of ways, the experimental findings were contrasted with analytical models. ...
Recent applications demonstrated how fiber-reinforced polymer (FRP) composites can improve the structural capabilities of glulam beams, particularly regarding their flexural and shear strength. With the development of precise numerical models, such systems can be optimized. There is currently a dearth of information in the literature on numerical models that can accurately anticipate the nonlinear behavior of low-grade glued laminated timber beams reinforced with FRP. In this study, larch beams were reinforced with carbon fiber reinforced polymer fabric 1, 2 and 3 layers. The effect of the number of floors on the flexural properties of the beams in reinforcement was investigated experimentally and numerically. As a result of the study, the best flexural properties were achieved with 3-layer reinforcement. It was observed that 1- and 2-layer reinforcement compared to the reference beam were also significantly effective. Numerical analyzes gave close values with experimental test results. As a result of comparing the results obtained from the numerical model with the experimental findings, it was concluded that the FRP fabric managed to significantly increase the performance of larch timber. The model is a useful tool for examining the effect of reinforcement coefficient and will be used for optimization of the larch beam
... They used the joint test results as the basis for a local bond-slip model. Johnsson et al. (2006) [32] evaluated a total of ten specimens under four-point bending from three different series of glulam beams reinforced with rectangular pultruded CFRP bars. The experimental results were compared with analytical models in several aspects. ...
... Due to inherent flaws leading to early fragile failure in the tension area, along with their comparatively lower bending stiffness relative to steel or reinforced concrete beams of similar cross-sections, wooden beams are not frequently utilized [1][2][3]. Different composite materials can be used to enhance the material properties of wood materials, as composite materials are especially used as carrier elements in wooden structures, such as glued laminated timber (glulam) [4][5][6][7][8]. ...
... Further, its versatility in terms of shape and size is noteworthy. The structural integrity and strength of glulam beams often surpass those of their individual laminations [33]. ...
... Na literatura são encontradas poucas publicações relacionadas às aplicações de PRF com a técnica NSM em estruturas de madeira, como por exemplo, (BORRI et al., 2005;JOHNSSON et al., 2007e AHMAD, 2010. Os resultados apontados nestes trabalhos revelam um bom desempenho da técnica NSM para aumento tanto da capacidade de resistência, quanto da rigidez. ...
A madeira por ser um material natural, originário de fontes renováveis e, portanto, de consciência ecológica e sustentável oferece uma alternativa viável para o seu uso em edificações. Devido às suas propriedades mecânicas é possível uma ampla aplicabilidade na construção civil. Por outro lado, é possível obter resistência e rigidez maiores para a madeira com a inclusão de reforços estruturais. Uma dessas técnicas utiliza elementos em Polímero Reforçado com Fibras (PRF). Neste artigo, vigas de madeira, são reforçadas com barras de PRFV (Polímero Reforçado com Fibras de Vidro) e PRFC (Polímero Reforçado com Fibras de Carbono). É desenvolvida a análise teórica do comportamento mecânico da viga, analisando sua rigidez e momento resistente último. Ao final do trabalho é desenvolvido um exemplo numérico de uma viga de madeira sem reforço e também com a inclusão desses reforços. Os resultados mostraram um acréscimo tanto na resistência ao momento fletor, quanto rigidez à flexão da viga de madeira com reforço, em relação a viga sem reforços.
... Over the years, to improve of technological properties of LVL as a construction material, reinforcement of LVL, wood and adhesive type and methods have been carried out by many researchers [22][23][24][25][26][27][28][29][30][31][32][33] . When previous studies are analyzed, many of the researchers have been focused effect of reinforcement material on tension of glulam or timber in bending, modulus of rupture (MOR), and modulus of elasticity (MOE), however reinforcing LVL has not been commonly reported. ...
... Researches that combine near-surface mounted FRP composites with timber structures strengthening are significantly less than researches that applied NSM techniques to concrete strengthening [41], the NSM technique has been proven effective on increasing load-carrying capacity and stiffness [42,43]. ...
A review on damages and messes of trees caused by typhoon and other natural disturbances indicates that innovative methods are required to strengthen the trees in urban area. One such approach involves the use of fibre reinforced polymer (FRP) composites. This method strengthens trees through inserting FRP plates into the trunk and finally increases the ultimate strength as well as the stiffness of trees. This research aims to quantify the strengthening effect of the implanted FRP plate on trees by investigating the behaviour of FRP-to-timber bonded interface. One of the most important issues about the FRP-to-timber bond is the FRP plate debonding which provides insight into the mechanism of bonded interface. The debonding between timber and FRP may happen at different locations of the joint as follows: (1) timber-adhesive interface in the wood substrate (2) timber-adhesive interface (3) adhesive-FRP interface (4) within adhesive. There are different factors affecting the debonding failure mode including surface preparation, material properties (timber, FRP and adhesive) and curing conditions such as temperature, humidity etc. As the properties of FRP composites are usually available from the manufacturer or can be easily obtained by conducting the standard test e.g. ASTM 3039, emphasis have been put on wood mechanical properties which varied significantly under different environmental conditions and were affected greatly by natural imperfections including knots and splits. Timber was observed to fail brittlely when subjected to tension, whereas it exhibited some ductility under compression. Timber specimens cut from different layers of the section inclined to have different strengths with Heartwood (close to the core) being weaker and the Sapwood (close to the bark) being stiffer. Influences of moisture content also differentiated among layers, and Heartwood was more likely to be affected by changes of moisture content than Sapwood. With the present of natural defects, wood mechanical properties decrease remarkably, but the influences of the imperfections were yet quantified. Four tests of single-lap bonded joints were conducted to explore the bond relationship between FRP and wood substrate. Two types of epoxy adhesives, namely 3M Scotch-Weld 2216 and Six 10, were tested for comparison on the suitability of bonding timber. The result shows that the strain of the FRP plate deceases as the distance from loaded end increases and then stays at a relatively low level till the end of bond length. This implies that the strain distribution of FRP plate bonded with timber is similar to that of FRP-to-concrete bond. Bonded joints fabricated by using Six 10 were tested to have higher bond strength but fail suddenly with little debonding, while load plateau occurred in joints made by using 3M Scotch-Weld 2216 indicating the propagation of debonding. At the trial stage, load eccentricity and lack of support at the far end of the joint induced some degree of bending to the FRP plate, which affected the overall strain profile. It was suggested by the single shear tests that accurate test results depend on both precise fixture fabrication and careful experimental execution. Research focus has been diverted to near-surface mounted (hereafter NSM) bonded joints test, for it directly simulates the bond condition between FRP and wood for the proposed strengthening method. Three series of tests with eight NSM bonded joints have been conducted to investigate the interfacial behaviour and corresponding influential parameters including bond length, timber types and humidity. There exists an important concept that the bond strength of FRP to timber cannot always increase with a longer bond length. The specific limit of bond length is known as effective length beyond which the bond strength does not increase. Different moisture contents were achieved by curing the bonded joints in the moisture chamber for different time, namely one week or two weeks. This aimed to emulate the actual living conditions where humidity level varies considerably and its effect on the bond performance should be accounted for. The test results showed that NSM joints behaved similarly to the single-shear bonded joints. However, NSM bonded joint did not always have a desired failure mode, which can be attributed to the insufficient surface preparation and lack of pressure in the bond area during the curing process. The humidification tended to weaken the bond of the NSM joints, probably because the adhesive strength cannot fully develop under high moisture condition.
... In work [31], pultruded rectangular CFRP bars were investigated as reinforcement for glued laminated beams and the effect of the anchorage length of the CFRP bars on the bending of the beams was determined. Experimental studies in papers [32,33] based on flexural strength tests of timber beams with different dimensions, with different glued-in FRP fibres (i.e., CFRP cords, GFRP cords and BFRP bars) and with two types of adhesives (i.e., melamine glue and epoxy resin). The study concluded that FRP cord reinforcement is a potential alternative to pultruded bars. ...
These elements are innovative and of interest to many researchers for the reinforcement of wooden elements. For the reinforced beam elements, the effect of the reinforcement factor, FRP and steel elastic modulus or FRP and steel arrangement of the reinforcement on the performance of the flexural elements was determined, followed by reading the load-displacement diagram of the reinforced beam elements. The finite element model was then developed and verified with the experimental results, which was mainly related to the fact that the general theory took into account the typical tensile failure mode, which can be used to predict the flexural strength of reinforced timber beams. From the tests, it was determined that reinforced timber beam elements had relatively ductile flexural strengths up to brittle tension for unreinforced elements. As for the reinforcements of FRP, the highest increase in load-bearing capacity was for carbon mats at 52.47%, with a reinforcement grade of 0.43%, while the lowest was for glass mats at 16.62% with a reinforcement grade of 0.22%. Basalt bars achieved the highest stiffness, followed by glass mats. Taking into account all the reinforcements used, the highest stiffness was demonstrated by the tests of the effectiveness of the reinforcement using 3 mm thick steel plates. For this configuration with a reinforcement percentage of 10%, this increase in load capacity was 79.48% and stiffness was 31.08%. The difference between the experimental and numerical results was within 3.62–27.36%, respectively.
... In contrast, nonlinear material behavior of some kind is used in compression in the vast majority of studies; see, e.g., numerical analyses in [1][2][3][4]. For the description of stress-strain relationship beyond the elastic limit, one may consider several variants, such as completely plastic (e.g., [5,6]), bilinear (e.g., [7][8][9]), higher-order (e.g., [10]), and even tri-linear [11]. Hill also suggested a bilinear anisotropic stress-strain relationship that may be used to predict orthotropic linear elastic-quasi-rigid behavior in tension and orthotropic linear elastic-perfectly plastic or bilinear behavior in compression; this model is applied in several studies, e.g., [12][13][14][15]. ...
The presence of knots significantly influences the mechanical behavior of timber. This research presents a parametric finite element analysis of the effect of knot characteristics on the flexural capacity of timber beams. Parameters include knot radius, longitudinal and vertical positions, length, and diving angle. The generation of the FE model is based on a technique developed in a previous research stage. The validation of the model is done via bending tests on a set of beams as well as a number of independent research studies. The numerical model accurately recreates the three-dimensional geometry of the knot and related fiber deviations. The capacity of the beams under bending is evaluated via the Tsai–Wu failure criterion. Findings reveal that the presence of knots in the tension zone leads to an early tensile failure and insufficient utilization of compression capacity, the decrease of bending capacity may rise significantly (up to 39% in this investigation), the knot inclination may positively or negatively influence the behavior depending on the diving angle, and moderate knot length can be detrimental to flexural capacity.
... Another work also revealed a 21.5% rise in strength and a slight improvement in stiffness of 4.69% [21]. A 10% increase in stiffness and a 44-60% increase in capacity were observed by [22]. Moreover, the use of CFRP sheets for wood strengthening resulted in a stiffness increase of 15-60% [23], and an increase of 20% in another study [24]. ...
The strengthening of timber beams with carbon-fibre-reinforced polymers (CFRP) has been widely used in the last decades to enhance the behaviour of historical or new timber structures, usually for bending. While considerable improvement in capacity and ductility is typically achieved, the increase in stiffness was, in many cases, well short of analytical expectations, which tend to overestimate stiffness. This study addresses the problem by investigating the underlying mechanical behaviour using experimental, analytical, and numerical tools on a sample of Norway spruce (Picea abies) beams reinforced with carbon-fibre fabric. In the experimental program, each beam is tested for bending with and without CFRP reinforcement in order to determine specimen-specific stiffness increase on an individual basis. The reinforcement yielded an increase of 27% in capacity, 53% in ultimate displacement, and 133% in compliance, verifying its efficiency. Axial compression tests on an independent sample are also performed to verify modulus of elasticity in compression. Numerical computations based on a beam model and a three-dimensional finite element model are performed with the introduction of separate moduli of elasticity for tension and compression in timber. Inverse computation using the experimental load–deflection curves yielded the moduli and the compression yield stress of timber to provide the best match between tests and simulations. The mean difference of only 6% in stiffness between FEM and the tests is obtained. The dominance of normal stresses in the longitudinal direction is found, in correspondence with the experimentally observed tensile failure of timber (apart from a few defected specimens). Compression yield stresses are within 7% (beam model) and 2% (FEM) error compared with the control axial tests. The differences between FE simulations and tests in ultimate load and compliance are within 1%. This study concludes that the application of CFRP in the composite beams enables the determination of timber material properties opposed to pure timber beams without reinforcement, and the adoption of separate moduli of elasticity for tension and compression leads to adequate modelling of reinforced timber beams.
... Bu amaçla, karbon, cam ve aramid gibi fiber takviye kumaşlar, emprenye işlemi, yoğunlaştırma, yüksek kaliteli ahşap malzemelerin birlikte kullanılması dahil olmak üzere birçok farklı yöntem tercih edilmektedir [34]. Ahşap malzemenin yük taşıma kapasitesini ve mukavemet özelliklerini artırmak için fiber takviye sistemlerinin kullanılması yaygın olarak uygulanan bir yöntem haline gelmiştir [35]. Ahşap malzemenin güçlendirilmesinde, yapıları restorasyona tabi tutarak yapı elemanlarının yük taşıma kapasitesini geliştirmek, deprem ve dış etkilerden dolayı oluşabilecek hasarları ortadan kaldırmak, yetersiz detaylandırma sonucu meydana gelen erken yorulma ve kırılmaları önlemek, uzun süre kullanıma bağlı olarak yük taşıma kapasitesinde oluşan kayıpları telafi etmek gibi nedenler etkili olmaktadır [36]. ...
Ahşap, yaygın olarak kullanılan en eski yapı malzemelerden birisidir. Farklı alanlarda da farklı amaçlarla kullanımına yönelik giderek artan bir talep vardır. Bu talebi karşılayabilmek için ahşap esaslı yapısal kompozitler geliştirilmiştir. Bu çalışmada, ısıl işlem uygulanmış ve fenol formaldehit (FF) tutkalı kullanılarak karbon ve cam elyaf ile güçlendirilmiş kayın (Fagus orientalis Lipsky) kompozit örneklerin bazı fiziksel ve mekaniksel özellikleri araştırılmıştır. Bu amaçla ahşap malzemelere 150, 175 ve 200°C sıcaklıkta 3 saat süre ile ısıl işlem uygulanmış ve deney örnekleri hazırlanmıştır. Test sonuçları, karbon ve cam elyaf ile güçlendirilmiş örneklerin eğilme direnci (MOR) ve eğilmede elastikiyet modülü (MOE) değerlerini artırdığını göstermiştir. Bununla birlikte liflere paralel basınç direnci (CS//) değerlerinde, uygulanan ısıl işlem sıcaklığına ve güçlendirici malzeme türüne göre önemli değişikliklere neden olurken, liflere paralel yapışma direnci (SS) değerlerinde düşüşler belirlenmiştir. Genel olarak, karbon fiber ile güçlendirilmiş deney örneklerin MOR ve MOE değerleri, cam elyaf ile güçlendirilmiş örneklerden daha yüksek, CS// ve SS değerleri ise daha düşük belirlenmiştir.
... [5,6]), bilinear (e.g. [7][8][9]), higher-order (e.g. [10]), and even tri-linear [11]. ...
The presence of knots significantly influences the mechanical behaviour of timber. This research presents a parametric finite element analysis of the effect of knot characteristics on the flexural capacity of wood beams. Parameters include knot radius, longitudinal and vertical positions, length, and diving angle. The generation of the FE model is based on a technique developed in a previous research stage, and bending tests on a set of beams were employed for the validation. The numerical model accurately recreates the three-dimensional geometry of the knot and related fibre deviations. The capacity of the beams under bending is evaluated via the Tsai--Wu failure criterion. Findings reveal that the presence of knots in the tension zone leads to an early tensile failure and insufficient utilization of compression capacity. The decrease of bending capacity may rise to 39\%, and the knot inclination may positively or negatively influence the behaviour depending on the diving angle.
... Reinforced beams initially fail in the tensile zone and then crush in the compression zone [14]. Several authors observed such behaviors [2,4,6,13,16,[39][40][41][42]. Thus, the stresses presented by the numerical model are consistent with the stresses obtained from the experimental model. ...
Incorporating steel bars as reinforcement in glued laminated timber beams is a technique that aims at better structural performance, allowing the reduction of cross-sections. In the present research, based on experimental results from literature about the reinforcement of timbers beams, a parametric study was carried out with the aid of 164 numerical simulations performed within the scope of linear and nonlinear physical analysis via the finite element method to evaluate, with the aid of analysis of variance (ANOVA), the span, base, height, and the reinforcement ratio influence in the service force, ultimate force, and ultimate displacement. Multiple regression models evaluated by ANOVA were established to estimate the service and ultimate forces and ultimate and service displacements as a function of other variables. The results showed an average increase in the service load of 32% and 49%, and the ultimate load of 42.90% and 66.90%, for reinforcement rates of 2% and 4%, respectively. Regarding the multiple regression models, due to the good values obtained from the adjusted determination coefficients to estimate the values of the forces and the ultimate displacements, these can be used in the pre-design of glued laminated timber beams reinforced with steel bars.
... Neben den Verstärkungen analysierten sie auch detailliert verschiedene Klebstoffe in Kombination mit Faserverbundkunststoffen (FVK). Ehlbeck und Colling (1987) Kuilen (1991), Plevris und Triantafillou (1992), Hernandez et al. (1997), Blaß und Romani (2001), Johnsson et al. (2007) und Blank (2018). Haller und Wehsener (1999) untersuchten die Verstärkungswirkung von Glasfasergewebe für Stabdübel-Schlitzblechverbindungen. ...
Eine bekannte Schwachstelle von Brettschichtholz aus Nadelholz sind die im Vergleich zur Biegefestigkeit sehr geringen Schub- und Querzugfestigkeiten. Aus diesem Grund war es das Ziel dieser Arbeit, ein furnierverstärktes stabförmiges Holzprodukt für tragende Zwecke im Bauwesen zu entwickeln – holzbewehrtes Holz. Holzbewehrtes Holz ist ein neues, hochleistungsfähiges Holzbauprodukt mit deutlich verbesserten Eigenschaften bei Schub- und Querzugbeanspruchungen.
... [2,[11][12]), bilinear (e.g. [1,[20][21][22]), higher-order (e.g. [23]), etc. ...
Fibre-reinforced polymers (FRP) are widely used to enhance the performance of structural elements of various materials, including timber. Measurements of reinforced beams mostly involve load-deflection relationships in order to experimentally verify mechanical improvements, while numerical simulations require material parameters for constitutive laws. In this study, a numerical method based on the classical beam theory is presented to inversely determine the elastic-plastic parameters of the timber material and the reinforcing FRP fabric using measurement data on full-scale composite beams. Data on bending tests of spruce beams obtained in a previous research stage are used to demonstrate the method. The method can provide material parameters for the full size composite structural element prepared under conditions relevant to actual design conditions, including the reinforcement preparation. It is found that the bilinear model is an adequate description for wood, and good agreement between simulated and measured data is obtained. Model material parameters are computed and presented for several specimens individually.
... For bar-shaped FRP (e.g., bars, rods, and cords), the fabrication procedures always require slotting on the timber surface. Johnsson et al. (2007) studied pultruded rectangular CFRP rods as the reinforcement of glulam beams and investigated the influence of the anchoring length of CFRP rods on the bending performance of beams. A theoretical model was proposed, and it presented great predictions in comparison to the experimental results. ...
The fiber-reinforced polymer is one kind of composite material made of synthetic fiber and resin, which has attracted research interests for the reinforcement of timber elements. In this study, 18 glued-laminated (glulam) beams, unreinforced or reinforced with internally embedded carbon fiber–reinforced polymer (CFRP) sheets, were tested under four-point bending loads. For the reinforced glulam beams, the influences of the strengthening ratio, the modulus of elasticity of the CFRP, and the CFRP arrangement on their bending performance were experimentally investigated. Subsequently, a finite element model developed was verified with the experimental results; furthermore, a general theoretical model considering the typical tensile failure mode was employed to predict the bending–resisting capacities of the reinforced glulam beams. It is found that the reinforced glulam beams are featured with relatively ductile bending failure, compared to the brittle tensile failure of the unreinforced ones. Besides, the compressive properties of the uppermost grain of the glulam can be fully utilized in the CFRP-reinforced beams. For the beams with a 0.040% strengthening ratio, the bending–resisting capacity and the maximum deflection can be enhanced approximately by 6.51 and 12.02%, respectively. The difference between the experimental results and the numerical results and that between the experimental results and analytical results are within 20 and 10%, respectively.
... erefore, to further improve the practical utilization of the proposed CLB, strengthening techniques [24][25][26][27] are recommended, which are of important necessity. In wood structures, strengthening techniques include prestressed steel bar [24], carbon fiber-reinforced polymer (CFPR) sheet [28,29], glass fiber-reinforced polymer (GFRP) sheet [30], and CFRP bar [31]. Wei et al. conducted a series of tests to study the effect of the steel bar and FRP sheet on the flexural performance of the bamboo scrimber beams [8]. ...
In order to accord well with the requirements of sustainable development and green construction, a cross-laminated bamboo composed of an odd number of orthogonally oriented layers of bamboo scrimber is proposed in this paper. Adjacent bamboo layers are face-bonded by structural adhesives under pressure. The uniform mechanical and physical properties can be obtained through the orthogonal layup. Flexural performances of three groups of one-way CLB slabs and two groups of one-way CLB slabs strengthened with CFRP grids were investigated via four-point monotonic loading configuration until failure. Experimental parameters of thickness of the layer, number of layers, and manufacturing processes of CFRP grids were taken into consideration. Experimental observations showed that the failure of the CLB slab was brittle, and different failure modes were found in the CLB slab with CFRP grids via different manufacturing processes. Test results showed that the load-carrying capacity increased with the thickness of the layer, number of layers, and application of CFRP grids pressed in the bamboo layer, but the CFRP grids pressed in the interface of adjacent bamboo layers weakened the load-carrying capacity. The strain analysis demonstrated that the compression region was utilized with more efficiency via CFRP grids pressed in the bamboo layer, and the plane cross section assumption is suitable for both CLB slab and CLB slab strengthened with CFRP grids. A theoretical calculation method of flexural load-carrying capacity was proposed for the CLB slab, the accuracy of which was proved.
... Glišović and Johnsson carried out a series of experiments to study the impact of GFRP on the stiffness, bearing capacity, and ductility of Glulam beams [14,15]. The ultimate bearing capacity of Caribbean pine Glulam beams strengthened with fiber reinforced polymer (FRP) and without FRP were compared and analyzed [16]. ...
An anchorage device is an integral part of the prestressed Glulam beams. Therefore, its rationality and practicability have significant effects on the mechanical performance of the prestressed beams. To investigate the impact of the anchorage devices on the bearing capacity and stiffness of the prestressed beams, this paper compared and analyzed four kinds of anchors in detail through the finite element software. The results showed that when the initial mid-span deflection was 5 mm, 10 mm, and 15 mm, the bearing capacity of prestressed beams with four anchorage devices was 80.37–177.24%, 93.56–182.51%, and 95.62–194.60% higher than that of ordinary Glulam beam, respectively. When the initial mid-span top prestresses were 1 MPa, 1.5 MPa, and 2 MPa, the bearing capacity of prestressed beams with four anchorage devices was 101.71–172.57%, 105.85–175.88%, and 109.64–180.87% higher than that of ordinary Glulam beam, respectively. In addition, based on the simulation results, the prestressed beam with the external anchorage had the highest bearing capacity and stiffness. The deformation capacity of the beam with boot anchorage was the largest. The stress distribution of the beam installed under beam anchorage was the most uniform, and the beam with slotted anchorage was easy to cause stress concentration at the notch. Finally, based on the outstanding performance of the external anchorage, it was selected to carry out one experiment, and the experimental result showed that the simulation could predict the damage model and load–deflection relationship of the prestressed beams well.
... In the case of the use of densified wood in a layered composition, several key factors come into consideration, such as wood species, degree of wood densification, and layers' thickness [11]. Using additional non-wood reinforced components in the wood-based layered materials improves the bending properties in general because of neutral axis movement; however, this is conditioned by the appropriate placement of the fibers' overall composition and its orientation [19,8,3,20,4]. Commonly used non-wood reinforcement materials in the woodworking industry are carbon fibers, aramid fibers, and glass fibers [33]. ...
This work analyzes the influence of the composition of laminated materials based on solid and thermo-mechanically densified beech wood and the application of reinforcing elements in the form of reinforcing fibers. The paper investigates the behavior of the elastic, plastic, and total bending work and their ratios concerning the composition of the material. These characteristics are essential in determining the appropriate application of these materials in structural systems concerning the deformation energy in the elastic and plastic stress-strain areas. From the material point of view, factors such as the input thickness of beech lamellas (5 and 9 mm), the degree of densification of lamellas (references, 10%, 20%, 30%, and 40%), and the application of reinforcing fibers (carbon and glass) were observed and distinguished. There are several approaches to evaluate elastic and plastic work in bending. This paper deals with a more accurate method by integrating the curve of the force-deflection diagram. The output of the article points to a more efficient choice of beech wood modifications by densification concerning the formation of internal cracks in conjunction with the reinforcing fibers.
... Although extensive research has been done on the application of FRP composites for reinforcement, repair and reinforcement in concrete and masonry building elements, there are limited studies on their application in wooden structures. The majority of available studies have focused on flexural strengthening [3][4][5][6][7][8]. Reinforcement with fiber reinforced polymers (FRP) is one of the methods commonly used to repair existing wooden structures or to create high performance structures in newly built wooden structures. ...
Wood material can be destroyed over time due to different environmental factors (fungus and insect, rainwater). Building elements may need to be reinforced over time as a result of natural disasters or during use. Heat treated wood materials are more resistant to fungi and insects and their usage area is wide due to their high dimensional stability. However, with the heat treatment, there is a slight decrease in the mechanical properties of the wood material. In this study, it is aimed to investigate the effect of strengthening heat-treated ash samples with carbon, glass, basalt, aramid based fiber polymer on the load bearing capacity of the material. As a result of this study, it was observed that the flexural properties of heat-treated wood materials increased. It has been determined that reinforcement with carbon-based FRP fabrics significantly increases the flexural strength and elasticity module values of heat-treated wood material.
... The enhancement of FRP bar strengthening wood members has been proven by many researchers. Johnsson et al. [43] found that GiR reinforcement method increased the short-term flexural load-carrying capacity of glulam beams by 49%-63% on average. The reinforced beams demonstrated a moderate enhancement in ultimate moment capacity and stiffness [44,45]. ...
Retrofitting of existing ancient and modern timber structures has been an important project recently. And it triggers a need of excellent strengthening methods, so does the strengthening of newly built architecture. Traditional strengthening methods have shortcomings such as high costing and destroying the aesthetic of the structure, many of which can be overcome by means of using fiber reinforced polymer (FRP) composites. However, the behavior of FRP-towood systems has yet to be thoroughly researched compared with their FRP-toconcrete or FRP-to-steel counterparts. As FRP retrofitting and strengthening timber structures has a promising future, better understanding of their failure modes will enable more precise designs balancing safety and cost. Three of the most common FRP-to-wood systems in the literature are discussed in this paper, namely, the externally bonded reinforcement (EBR), the near-surface mounted (NSM) and the glued-in rods (GiR) techniques. Debonding of the FRP from the substrate is one of the most common failure modes, which exhibits the significance of the interface bond between FRP laminates and wood. Hence, bond properties and behavior of FRP-to-wood composite systems are described, parameters influencing the composite action are summarized in this paper, previous works on the bond interface of FRP and timber element are reviewed and future topics are also suggested. This work can provide a reference for future research and engineering applications.
... FRP kompozitlerin beton ve yığma yapı elemanlarında donatı, onarım ve güçlendirme amaçlı uygulanması konusunda kapsamlı araştırmalar yapılmış olmasına rağmen, ahşap yapılarda uygulaması konusunda sınırlı sayıda çalışma bulunmaktadır. Mevcut çalışmaların çoğunluğu eğilmeye karşı güçlendirmeye odaklanmıştır [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41]. ...
Sürdürülebilir yapı malzemeleri, yaşam döngüleri boyunca minimum düzeyde enerji harcayan, hammaddelerinin elde edilmesi, işlenmesi, kullanımı, bakım-onarımı ve atık oluşumları sırasında çevreye ve insan sağlığına zarar vermeyen malzemelerdir. Ahşap malzeme en yaygın kullanılan yapı malzemeleri arasındadır. Ancak mevcut kaynakların sürdürülebilirliğinin sağlanması için malzemenin servis ömrü boyunca korunması gerekmektedir. Uzun yıllardır ahşap malzeme yapıların inşasında kullanılmaktadır. Ülkemizde tarihi ahşap yapılar zaman içerisinde onarım ve güçlendirmeye ihtiyaç duymaktadır. Geleneksel onarım yöntemleri, ahşap malzemeye zamanla böcek arız olmasına, mantarlaşmaya ve çürüklüğe sebep olmaktadır. Ayrıca bütün zarar görmüş elemanların sökülmesi özellikle maliyet ve işçilik açısından önemli problemler ortaya çıkarabilmektedir. Bu nedenle, yapıda kullanılan ahşap elemanların tamamının değiştirilmesi yerine zarar görmüş elemanların onarılması sürdürülebilirlik açısından daha uygundur. Yapılan bölgesel değişiklik ile birlikte kavela, çivi, blonlama tekniği gibi yeni birleşimler oluşmaktadır. Fiber takviyeli polimerler ile güçlendirme ile zamandan tasarruf sağlanmakla birlikte görsellik açısından da önemli avantajlar sunmaktadır. Bu nedenle fiber takviyeli polimerlerin kullanımı daha sürdürülebilir ve yenilenebilir bir yapı oluşturmaya katkı sağlayacaktır.
... Borri et al. (2005), for example, studied the use of externally adhered CFRP pultruded laminates on the tension zone of wooden beams and they achieved improvements in the ultimate strength of about 42%. The use of one or two pultruded rods introduced in slots made from the outside, within the tension area, was studied by Johnsson et al. (2007) for glulam beams. The load capacity was increased by 44% and some improvements in ductility were mentioned, indicating the advantages of two rods instead of just one. ...
This work examined the enhancement of bending strength properties of two wood species, namely fir and pine, reinforced with two carbon fibre fabrics (CFF) of different areal weight, in two different layouts. CFF applied in the bottom surfaces of the specimens (‘F’-type) and in the second wrapped in the bottom surfaces and up to the half of the lateral surfaces (‘U’-type).The results indicated that samples which are reinforced with CCF show higher MOR and MOE values than the controls and this improvement was found to be significantly different. The reinforcement layout affected the bending properties of both pine and fir wood, since the corresponding values are higher in U-shaped reinforcement than in F-type reinforcement, at identical CFF areal weights. In the case of fir wood, the CFF areal weight did not significantly affect the bending properties.
... erefore, to improve the practical utilization of the bamboo engineering material, the strengthening techniques [21][22][23][24] are recommended and of important necessity. In the previous studies of wood structures, strengthening techniques include prestressed steel bar [21], carbon fiberreinforced polymer (CFPR) sheet [25], glass fiber-reinforced polymer (GFRP) sheet [26] and CFRP bar [27], etc. However, the incompatible elastic moduli of steel and wood resulted in the significant deformation of the wood and large prestress loss [28]. ...
Until now, the systematical and comprehensive strengthening techniques have not been formed for the bamboo structure. Under such background, this paper aims to explore the effects of the application of the nonprestressed and prestressed basalt fiber-reinforced polymer (BFRP) bars on the flexural performance of the beams made of the laminated bamboo and reconstituted bamboo materials. Two series of four-point bending tests were thus conducted. In the first series of tests, the pure laminated bamboo beam and the laminated bamboo beam applied with nonprestressed BFRP bar were compared. Test results showed that the ultimate load and deformation capacity of the laminated bamboo beam was improved due to the existence of the BFRP bar. In the second series of tests, the reconstituted bamboo beams applied with nonprestressed and prestressed BFRP bars were compared. It is found that the ultimate load of the reconstituted bamboo beam was not improved by the application of the prestressed force. The further analysis related to the prestress loss demonstrated that the prestress loss before the release of the prestressed BFRP bar could reach up to 31.8–37.3% compared with the design initial prestressed stress. The prestress loss caused by the elastic deformation of the bamboo beam can be neglected. For all tested specimens, the plane section assumption was acceptable and the position of the neutral axis of the beam gradually moved down with the increase of the applied load.
Timber structures have been valued for their versatility, aesthetic appeal, and sustainability; however, they are prone to deterioration over time. With the growing interest in mass timber
production, ensuring the durability and serviceability of timber has become increasingly important. This paper provides a comprehensive state-of-the-art on the durability of timber alongside an in-depth review of the historical and recent developments in the application of FRP materials for the purpose of strengthening and rehabilitating wooden structures. In addition, this
review critically underlines a range of experimental, numerical, and analytical studies incorporated FRP materials into timber structure as strengthening technique. The outcome of this research will contribute as a valuable resource for scholars and engineers through facilitating a comprehensive understanding of the available reinforcement techniques of timber.
Sawn-timber products are products processed from sawn timber, where the appearance and the other properties of the final product are strongly related to the sawn timber. This chapter begins with sawn timber in general and presents the various sawn timber products such as solid timber for construction, glued-laminated timber (glulam), cross-laminated timber (CLT), and solid-wood panels in detail. Further timber-based products comprising pattern, millwork, cabinetry, pallets, trusses, etc., are highlighted shorty. The various product-specific technologies, manufacturing processes, as well as product properties and applications are described. Some key market data are provided to each of the product category. The chapter ends with a short survey of joinery-machining concepts for customizing the sawn-timber products.KeywordsGlued-laminated timber (glulam)Cross-laminated timber (CLT)Solid-wood panelsSawn timberSawn-timber productTimber trussesJoinery machines
This study’s objective is to examine the general behavior of glulam timber beams strengthened with CFRP (Carbon Fiber Reinforced Polymers) strips and ascertain the impacts of the applied strengthening technique on the performance of timber beams under the influence of rapid dynamic impact loading. In the study, the innovative strengthening method developed with CFRP strips was placed on the lower tensile surface of glulam timber beams and positioned as more than one layer between laminated beam parts. In addition, placing CFRP fan-type anchors on the endpoints of the strips to delay the debonding of CFRP strips from the surface is an innovative application examined in this study that contributes to the literature. The glulam timber beams that strengthened with the developed method and non-strengthened reference test specimens were tested with the free-weight drop test setup. The acceleration, displacement, strain at the tensile surface, and the variations of the applied impact loading by the time were measured and interpreted. In this way, the performance level of the strengthening technique under the effect of the impact loading was investigated. The glulam timber beams strengthened with CFRP strips are modeled using ABAQUS finite element software to compare the numerical analysis with the experimental results and determine the extent to which the numerical analysis might produce realistic results.
Glulam materials were commonly used and are ease in construction materials. Glulam timber provides strength and stiffness, to increase the properties of it while using in construction, along with reinforcement bars. The reinforcement material used by most of the researchers was Fiber-Reinforced Polymers (FRPs) Since this provides fatigue resistance, high tensile strength, stiffness and, durability properties. This paper reviews the structural behavior of glulam beams with different reinforcement materials. The parameters discussed were the strength of the connections, compressive strength, flexural strength, and tensile strength of beams. Result exhibits that FRP material is the best reinforcement material for glulam beams. Notch connections result in fail earlier and fire test also exhibits early failure than expected.
Laminated wooden beams are more preferred in the production of wooden structures than solid timber beams because they have a higher load-carrying capacity and allow larger openings to be used in the structure. The widespread use of wooden structures and the increasing size of the structures have revealed the need for strengthened laminated wooden beams and increase their ultimate load capacity. It has become necessary to develop reinforcement details to increase the ultimate load capacity of laminated wooden beams in wooden railroads or highway bridge beams, where the traffic load increases, especially in large wooden structures, in cases where large openings must be passed. Within the horizon of the study, the behavior and performance of three-layer glulam wooden beams strengthened with anchorage and non-anchorage CFRP strips with different bonding length under flexural loading were investigated experimentally. The three-point bending test was applied to glulam timber beam test specimens produced by laminating yellow pine wood material using the polyurethane adhesive. General load-displacement behaviors, ultimate load capacity, initial stiffness, displacement ductility ratios, and energy dissipation capacities were obtained. The increase in the bonding length of the CFRP strips used for strengthening in the glulam timber beam specimens and the use of CFRP fan type anchors at the strip ends increased the ultimate load capacity and initial stiffness values of the wooden beams, as well as the displacement ductility ratios and energy dissipation capacity values.
The present paper shows the first results of an ongoing research aimed at studying the potentiality of the combination of laminated timber and natural fibers to obtain high-performance structural elements. The experimentation conducted has involved a set of Cross Laminated Timber (CLT) panels made of maritime pine grown in Sardinia (Italy) and externally reinforced with natural flax fibers fabrics. A bending test program has been carried out on two CLT layouts, three-layers and five-layers panels, for a total of 34 specimens. Three-layers panels have been tested with single and double strip of flax fibers aiming to evaluate any difference in the rupture mechanism, capacity and stiffness. The proposed technique allows a straightforward application on the intrados of the panel, aimed at increasing its capacity and stiffness. Results show that in case of three-layers panels a significant increment of load-carrying capacity and stiffness has been achieved, whilst for five-layers panels the effectiveness of the reinforcement is negligible. Variations in the failure mechanisms of reinforced panels have been discussed.
This paper presents a study on the reinforcement of existing wood elements under bending loads through the use of FRP materials. An analytical investigation was first conducted on the behavior of a generic FRP-reinforced wood section. This study, in turn, led to a numerical procedure based on non-linear wood properties, suitable for application in the design of FRP reinforcement of old, pre-existing wood beams under varying configurations of intervention layouts and materials. An experimental programme based on a four-point bending test configuration is proposed to characterize the stiffness, ductility and strength response of FRP-wood beams. Mechanical tests on the reinforced wood showed that external bonding of FRP materials may produce increases in flexural stiffness and capacity. The FRP composite material was made of High Tensile Carbon monodirectional reinforcing fabrics embedded in an epoxy resin matrix. This reinforcing method can be applied without necessitating the removal of the overhanging part of the pre-existing wood structure, thus maintaining the original historical structure. In addition, a beam non-linear model was proposed to predict ultimate load. At the end of this paper results of the experimental programme are presented and used for comparison with the numerical procedure.
"Report TVSM-1012"--Spine. Thesis (Ph. D.)--Lund University, 2000. Includes bibliographical references.
This paper describes aspects within an experimental and theoretical programme aimed generally at improving the structural performance of laminated beams fabricated from Irish-grown Sitka spruce. Such timber is characterised by low density and small dimensions, is likely to distort when dried and tends to fail in tension due to the presence of knots. The well-established technique of laminating timber overcomes some of these disadvantages and the improvements are most marked with low quality donor material. It has been found that the addition of modest ratios of FRP composite reinforcement can suppress tension failure in beams. The study of failure modes, particularly in tension-reinforced beams, is the main focus of this paper. It establishes that the ultimate load capacity depends on the behavior of the timber in compression, resulting in much more consistent behavior as well as a considerable increase in flexural stiffness.
This research project demonstrates how advanced composite materials can be used to strengthen existing timber bridge beams in order to increase the load capacity of the bridge. Many times, the timber bridges were not designed to withstand the heavy truck traffic that they are currently carrying, and are therefore replaced in favor of modern concrete or steel bridges. Current methods of strengthening timber bridges are not always practical or economical and so these bridges are simply replaced at a high cost to the public. This project investigated whether applying composites in the form of either a fabric wrap or laminate strips to timber beams would increase the load capacity of the beams. Bidirectional carbon fabric was the primary strengthening material used. A total of 10 solid-sawn Douglas Fir timber beams were taken from a timber stringer bridge in Yuma, Ariz. that was replaced in 1999. Seven of the 10 creosote-treated beams were reinforced with carbon fiber and then tested for bending strength, shear strength, and stiffness. Three of the beams were tested as unreinforced control specimens. The results show that applying carbon fabric to the timber beams provides significant increases in the bending and shear capacity, and nominal increases in the stiffness of the beams. Allowable stress modification factors are conceptually discussed that could potentially be used by engineers to determine the safe load-carrying capacity of beams reinforced with carbon fiber. However, a statistically significant number of timber beams strengthened with carbon fiber need to be tested to arrive at definitive stress modification factors.
An experimental program was undertaken at The University of Manitoba to test timber stringers strengthened with glass fibre reinforced polymer (GFRP) bars. Various strengthening schemes were investigated as a means of increasing the load carrying capacity of timber stringers in shear and flexure. The shear strengthening was achieved by inserting GFRP dowels in the centre of the cross section along the length of the stringers. The flexural strengthening used the concept of near-surface-mounted GFRP bars. Fifty beams were tested to evaluate the performance of the various strengthening schemes. The behaviour of the beams is described in terms of mode of failure, mechanical properties, and load–deflection behaviour. This study found that strengthening timber stringers with GFRP reinforcement increased the ultimate strength of the stringers and reduced its variability. It is believed that the shear and flexural GFRP reinforcements act as a truss member within the timber beam and bridge the local defects and discontinuities of the timber.Key words: timber, glass fibre reinforced polymer, bridge, stringers, dowels, strengthening, ductility.
A promising use for high performance composite materials is to reinforce timber beams. The present paper studies the use of glass fibres to reinforce sawn timber sections. Consideration is given to strength phenomena of commercial timber alone and in reinforced sections in bending and shear. Experimental results are presented for two sizes and qualities of wood beams using matched samples of pairs of beams, reinforced and not. Results establish that the wood itself in the composite section shows a great strength increase, and that the increase in moment resistance of the reinforced beams is far greater than that predicted by simple models
Over the past decade, the issue of deteriorating infrastructure has become a topic of critical importance in Europe, and to an equal extent in the United States and Japan. The deterioration of decks, superstructure elements and columns can be traced to reasons ranging from ageing and environmentally induced degradation to poor initial construction and lack of maintenance. Added to the problems of deterioration, are the issues related to the needs for higher load ratings and increased number of lanes to accommodate the ever-increasing traffic flow on the major arteries. As an overall result, a significant portion of our infrastructure is currently either structurally or functionally deficient. Beyond the costs and visible consequences associated with continuous retrofit and repair of such structural components, are the real consequences related to losses in production and overall economies related to time and resources caused be delays and detours. As we prepare for the twenty-first century, the renewal of our lifelines becomes a critical issue. The introduction of fibre -reinforced polymers (FRPs) in civil engineering structures has progressed at a very rapid rate in recent years. These high-performance materials have unique properties that make them extremely attractive for a wide range of structural applications. The basic concepts relative to the use of FRPs for structural strengthening, along with examples of application, have been presented by a numerous of researchers all over the world. The rapidly expanding body of literature in this area, along with corresponding increase in level of activity, confirms the fact that these new materials are progressively gaining wider acceptance by the civil engineering community. Nevertheless, if the method shall be successfully used it is of utmost importance that a proper design forms the base for the strengthening work to be carried out. Therefore, design guidelines are of utmost importance. In Sweden t design guidelines for external strengthening with FRP was written and incorporated in the Swedish Bridge Code: BRO 94 in 1999. This paper presents a short summary of the existing Swedish guideline. FRP strengthening design is a quite straightforward process, if the designer possesses knowledge in the area. However, consideration must be taken to special possible failure modes related to the FRP sheets or laminates. In addition the existing strain (stress) field on the structure can be of considerable importance for existing structures. Furthermore, the execution process is of tremendous importance as it is essential to understand where and when the strengthening materials can and should be used. If the work is not carried out in a careful way -the final strengthening result could be severely affected for FRP Plate Bonding.
Tim-ber Beams Notched at the Support. TVSM-7071, Div. of Structural Mechanics Aligned Fibre Reinforcement Panel for Wood Members
- Riberholt H B Enquist
- P-J Gustafsson
Riberholt H, Enquist B, Gustafsson P-J, et al. (1992) Tim-ber Beams Notched at the Support. TVSM-7071, Div. of Structural Mechanics, Lund Institute of Technology, Lund 20. Patent 94/21851 (1994) Aligned Fibre Reinforcement Panel for Wood Members. International Publication no. WO 94/21851
ICBO Evaluation Report PFC-5100
- Icbo
Timber Beams Notched at the Support. TVSM-7071, Div. of Structural Mechanics
- H Riberholt
- B Enquist
- P-J Gustafsson
Tests with Glass-Fibre Reinforcement of Wood Perpendicular to the Grain
- H J Larsen
- P-J Gustafsson
- B Enquist
- HJ Larsen
Fracture Perpendicular to Grain – Structural Applications. Timber Engineering
- P-J Gustafsson
Plug Shear Failure in Nailed Timber Connections – Avoiding Brittle and Promoting Ductile Failures
- H Johnsson
Plug Shear Failure in Nailed Timber Connections - Avoiding Brittle and Promoting Ductile Failures. Doctoral thesis, Div. of Timber Structures
- H Johnsson
Analysis of Generalized Volkersen-joints in terms of Non-linear Fracture Mechanics
- P-J Gustafsson
Composite reinforcement of timber in bending
- K C Johns
- S Lacroix
- KC Johns
Fracture Perpendicular to Grain - Structural Applications
- P-J Gustafsson