Figure 4
![Schematics of testing methods to evaluate bond of FRP laminates to wood. (a) Type 1: contoured double-cantilever beam (CDCB) for Mode I fracture test [55], (b) Type 2: single-lap shear joints for Mode II fracture test: (i) shear-block test specimen and shearing tool of ASTM D-905 [32]; (ii) double-notched test specimen [35,53,56]; (iii) single-lap shear joint and shearing tool [33,39,40,54] and (c) Type 3: wood beam test: (i) FRP laminate is terminated far from the supports [34]; (ii) FRP laminate extends to the supports [36,57,58]](publication/343286346/figure/fig4/AS:918619324174349@1596027322362/Schematics-of-testing-methods-to-evaluate-bond-of-FRP-laminates-to-wood-a-Type-1.png)
Schematics of testing methods to evaluate bond of FRP laminates to wood. (a) Type 1: contoured double-cantilever beam (CDCB) for Mode I fracture test [55], (b) Type 2: single-lap shear joints for Mode II fracture test: (i) shear-block test specimen and shearing tool of ASTM D-905 [32]; (ii) double-notched test specimen [35,53,56]; (iii) single-lap shear joint and shearing tool [33,39,40,54] and (c) Type 3: wood beam test: (i) FRP laminate is terminated far from the supports [34]; (ii) FRP laminate extends to the supports [36,57,58]
Source publication
![Figure 3: Bond-slip model for CFRP-to-wood interfaces [40]](publication/343286346/figure/fig3/AS:918619324162050@1596027322323/Bond-slip-model-for-CFRP-to-wood-interfaces-40_Q320.jpg)
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...
Contexts in source publication
Context 1
... bond testing methods were adopted by various researchers for different purposes of study, as illustrated in Fig. 4. They can be categorized into three ...
Context 2
... Type 1 testing method involves contoured double-cantilever beam (CDCB, see Fig. 4a) bilayer specimens, which are designed by the Rayleigh-Ritz method to conduct Mode I fracture tests of bonded FRP-wood ...
Context 3
... conduct Mode II fracture test, three different setups of Type 2 testing method are recommended as follows. A shear-block test specimen composed of FRP and a timber block as described in ASTM D-905 is involved in the test (see Fig. 4b(i)). However, this method is only applicable to FRP plate (e.g., Barbero et al. [32]) because compression loading is applied on FRP directly. A modified double-notched test specimen shown in Fig. 4b(ii) is analogous to the one above. It consists of two timber blocks and a piece of FRP plate or sheet, where the block on the left side is ...
Context 4
... are recommended as follows. A shear-block test specimen composed of FRP and a timber block as described in ASTM D-905 is involved in the test (see Fig. 4b(i)). However, this method is only applicable to FRP plate (e.g., Barbero et al. [32]) because compression loading is applied on FRP directly. A modified double-notched test specimen shown in Fig. 4b(ii) is analogous to the one above. It consists of two timber blocks and a piece of FRP plate or sheet, where the block on the left side is fixed while load is applied to the block on the right side. Raftery et al. [35], Crews et al. [53] have adopted this kind of set up to conduct the test. As FRP is sandwiched between two timber ...
Context 5
... this kind of set up to conduct the test. As FRP is sandwiched between two timber blocks, FRP plate surface strains are difficult to monitor, not to mention the shear stress distribution and bond-slip responses. Another set up allows detailed monitoring and inspection of the failure process, due to only one possible path for debonding, as shown in Fig. 4b(iii) adopted by Wan et al. [39,54], Biscaia et al. [40] and Vahedian et al. [33]. This method is also consistent with that used in studying the bond between FRP and concrete or steel. However, it is a challenge to be sure that the alignment is maintained to minimize load eccentricity. This method may not be applicable for FRP sheets ...
Context 6
... sheet/plate attached to the tensile flange of a timber beam. The loading is applied on the beam to create a pure bending zone. This type of testing closely replicates the adhesive shear and peel stresses that are induced by flexural loads. This method consists of two cases, one in which the FRP is stuck only at the middle section of the beam (see Fig. 4c(i), Vahedian et al. [34]) and the other extends to the both ends of beam (see Fig. 4c(ii)). It is worth noting that the second case seems to be the only method when prestressed FRP laminates as external reinforcement of wood beams is encountered ...
Context 7
... the beam to create a pure bending zone. This type of testing closely replicates the adhesive shear and peel stresses that are induced by flexural loads. This method consists of two cases, one in which the FRP is stuck only at the middle section of the beam (see Fig. 4c(i), Vahedian et al. [34]) and the other extends to the both ends of beam (see Fig. 4c(ii)). It is worth noting that the second case seems to be the only method when prestressed FRP laminates as external reinforcement of wood beams is encountered ...
Context 8
... on the above discussions, it is recommended that the test set up illustrated in Fig. 4b(ii) be used for FRP sheets, and that in Fig. 4b(iii) be used for FRP plates to conduct Mode II fracture test in establishing the bond-slip relationship between FRP and wood in tension as surface strain can be easily monitored. The failure modes can be separated into two categories based on the duration of composite action between the ...
Context 9
... on the above discussions, it is recommended that the test set up illustrated in Fig. 4b(ii) be used for FRP sheets, and that in Fig. 4b(iii) be used for FRP plates to conduct Mode II fracture test in establishing the bond-slip relationship between FRP and wood in tension as surface strain can be easily monitored. The failure modes can be separated into two categories based on the duration of composite action between the materials. Failure will occur in wood or FRP, ...
Context 10
... series of test setups for evaluating bond strength of FRP to wood have been involved in the literature. It is recommended that the test setup illustrated in Fig. 4b(ii) be used for FRP sheets, the setup in Fig. 4b(iii) for FRP plates to conduct Mode II fracture test and BPT in Fig. 9b for FRP bars to conduct NSM and GiR test in establishing the bond-slip relationship between FRP and ...
Context 11
... series of test setups for evaluating bond strength of FRP to wood have been involved in the literature. It is recommended that the test setup illustrated in Fig. 4b(ii) be used for FRP sheets, the setup in Fig. 4b(iii) for FRP plates to conduct Mode II fracture test and BPT in Fig. 9b for FRP bars to conduct NSM and GiR test in establishing the bond-slip relationship between FRP and ...
Similar publications
Background
Case-control designs are an important yet commonly misunderstood tool in the epidemiologist’s arsenal for causal inference. We reconsider classical concepts, assumptions and principles and explore when the results of case-control studies can be endowed a causal interpretation.
Results
We establish how, and under which conditions, variou...
Citations
... Over the last three decades, fibre-reinforced polymers (FRP) have been studied and used to enhance the structural behaviour of timber not only in new constructions but for old historical timber as well (Buell and Saadatmanesh 2005;Wan et al. 2014). Reviews on the application of FRP are given by Saad and Lengyel (2022b) and Wang et al. (2020). Typical internal forces of timber beams are shearing and bending, possibly combined with axial forces. ...
Material properties of historical timber structures may change over time due to decay, change of chemical composition of material, biological agents, climatic conditions, etc. Adequate bending performance requires stiffness and strength both in tension and compression, as well as sufficient ductility in compression. While the focus of most research is on the former quantities, the latter one is generally disregarded. This study gives a comparative analysis on complete characterization of compressive behaviour of recent and 60-years-old aged spruce timber (Picea abies). Parallel-to-grain compressive tests on small-sized specimens were conducted to obtain stress-strain diagrams and to determine failure modes. All material properties of stiffness, strength, and ductility were calculated for each specimen. It was concluded that elastic stiffness, elastic limit stress, and compression strength are virtually invariable after sixty years of service while the ductility decreased and the post-peak behaviour became more brittle. It is also found that end-rolling failure mode can yield the same elastic and stiffness properties as the standard kinkband failure. Climatic changes increase the risk of material deterioration prompting for more thorough monitoring and study of historical timber structures. ARTICLE HISTORY
... Too strong a degree of reinforcement had a slight effect on the increase in strength. The accuracy of the insertion of the reinforcement into the timber beams is also of great importance [45,46]. In the case of steel elements, the highest reinforcement process was shown by 3 mm thick sheets. ...
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.
... Unfortunately, one can only find very few papers attempting to provide any review on the topic. Either they focus on a specific area [9,10], or do not cover some important issues [11], e.g., modelling of knots in structural timber which is critical for understanding the effects of FRP on the wood behaviour. The authors of this particular paper intend to give a review as comprehensive as possible and identify and discuss a few unresolved topics as well. ...
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.
... The search for renewable, sustainable materials and energy is a top priority. New reinforcement techniques [1], passively controlled structural systems [2,3], wood, and bamboo as a sustainable green building material, are attracting more attention from the construction sector [4][5][6][7][8]. Bamboo is one of the fast-growing and most productive renewable natural resources in the world and has a high growth rate in the growing season [9,10]. ...
Bamboo vascular bundle fiber and parenchyma (BP) are separated by high-temperature treatment with saturated steam. Bamboo vascular bundle fiber is widely used in the market, but how to develop and utilize parenchyma tissue is a difficult problem. The sulfated cellulose nanofibers (ANFs) were obtained by sulfating BP with a deep eutectic solvent (DES), which provided a theoretical basis for the value-added utilization of BP. Using DES as the reaction medium and reagent, the BP was grafted with a sulfonic acid group to form a gel substance in water, ANFs and nanocellulose gel were obtained by ultrasonic cell crusher. The highest yield of ANFS was 75%. The width of the ANFs was about 3 nm, and a small number of nanofiber aggregates existed at the same time. A high aspect ratio of ANFs, due to their high viscosity, has potential applications as enhancers at low concentrations. Lewis acid (ZnCl2) added based on binary (DES) greatly improved the thermal stability of the ANFs and maintained the crystal form of cellulose I.
... The most fatal inherent defects of wood are biodegradability over time and dimensional instability under alternating environmental conditions [36]. Acetylation can significantly improve this problem. ...
... The influence of the change of different factors on WPG[2,36,38,39] ...
As a green material, wood is widely used in building decoration, railway construction, and other fields. However, the wood itself has inherent defects of being easy to absorb water and deform, rot, and decrease in strength. The physical and mechanical strengths and stability of artificial fast-growing forest wood are even worse. As wood modification can improve the dimensional stability, durability, strength, and other properties of wood, it has been widely used. Chemical modification is the main method of wood modification. The development of nanotechnology has brought more possibilities for wood modification. Owing to the extensive literature available, this article summarizes the representative achievements of wood chemical modification and nanotechnology. The principle, production process, advantages, and disadvantages of various wood chemical modification methods were analyzed, compared, and evaluated. Finally, according to the application status of wood-modified materials, the problems existing in the current wood chemical modification methods and the application of nanotechnology, and the development trend in the future are analyzed.
... Nowadays, because of the increasing carbon emissions in the construction industry, it is necessary to mobilize and develop new sustainable materials for construction use (Chen et al. 2020a, b;Lv and Liu 2019;Sun et al. 2020;Yang et al. 2020;Ding et al. 2020). Bamboo, as a widely distributed natural resource especially in Asia and South America Zhou et al. 2019;Fei et al. 2019;Wei et al. 2020), has the potential to fill this role (Sulaiman et al. 2006;Krzesinska et al. 2008;Chen et al. 2020c;Wang et al. 2020). A relatively new engineered materiallaminated bamboo lumber (LBL) (Li et al. 2016;Xu et al. 2019;Wu 2014;Porras and Maranon 2012;Brito et al. 2018)-has attracted increasing attention from researchers (Sharma et al. 2015;Mahdavi et al. 2011Mahdavi et al. , 2012. ...
The size effect on the axial compressive performance of laminated bamboo lumber is studied through compression tests on three groups of short columns with different heights and section sizes. The failure modes, bearing capacity, strain distribution, and deformation capacity were analyzed. Based on the test results, three groups of stress-strain models of laminated bamboo lumber with different sizes are presented. The simulated results were in good agreement with the test results. The slope method and the parameter method were used to calculate the size effect coefficient and the results showed that the linear regression parameter analysis method is more efficient for analyzing the size effect. It is concluded that the size effect coefficients of compressive strength, ultimate load, elastic modulus, ductility, and compressibility are 0.043 (1/23.26), 0.6676 (1/1.52), 0.064 (1/15.63), 0.0529 (1/18.90), and 0.133 (1/7.52), respectively.
... With the rapid development of modern society, sustainable buildings made of timber or bamboo-based materials are more and more popular because of the high demand for a better living environment for human beings. Timber has been used as a construction material for thousands of years [1][2][3][4][5], however, bamboo [6][7][8][9][10][11][12][13] as a green and natural material that can be harvested in 4-5 years combined with its excellent mechanical properties, has more potential for popularization. Laminated bamboo lumber (LBL) [14][15][16][17][18] is a type of engineered bamboo [19][20][21][22][23] that can be made into structural elements of different sizes according to construction needs while making up the organic limitations of natural bamboo and maintaining the excellent mechanical properties. ...
Eccentric compression tests on 15 chamfered laminated bamboo lumber (LBL) columns with a height ranging from 600 to 3000 mm were conducted in order to study the eccentric mechanical performance. The failure of all specimens was caused by the crack of bamboo fiber in the tensile region. When the ultimate strength was reached, except specimens with a height of 600 mm, all other specimens could bear large deformation, showing good ductility. The lateral displacements of the specimens under eccentric compression were approximately parabolic in the direction of column height. The ultimate bending moment of LBL columns with different slenderness ratios under compression with the same initial eccentricity was a fixed value. The relationship between ultimate capacity, axial displacement, lateral displacement, and slenderness ratio was analyzed based on test results. It was found that the plane section assumption could be used to express the stress and strain distribution of chamfered LBL columns under eccentric compression. A method for calculating the ultimate bearing capacity was proposed using a constitutive model based on the Ramberg-Osgood relation and the empirical formula for calculating the ultimate capacity was given on the basis of the former research as well as the test results in this paper.
... In recent years, wood structures have been paid extensive attention to and actively promoted due to their characteristics of environmental protection and sustainable development [1][2][3][4][5][6]. Glulam is an important material of wooden structures, which has several advantages such as scattered defects, high strength, and variable shapes of cross-sections and components, etc. [7][8][9]. ...
Due to wood creep characteristics, the failure mode, bearing capacity, stiffness, and deformation of its components are doomed to be impacted by long-term loading. This paper conducted a comparative test on creep beams, regulated beams, and short-term beams based on the former long-term loading research. The results demonstrated that the glulam beam experienced tensile failure of the beam-bottom, while the horizontal joint failure and the local compressive failure of the beam-end happened in the reinforced glulam beam and the prestressed glulam beam. The bearing capacity of the creep beams decreased compared with that of the short-term beams; the decline in the bearing capacity of the ordinary glulam beams, the reinforced glulam beams, and the prestressed glulam beams ranged from 4.22% to 9.83%, from 2.64% to 13.23%, and from 2.90% to 9.16%, respectively. However, the bearing capacity of the regulated beam with the deformation restored to the initial value of the load increased by 4.62–14.08%. The prestressed regulation changed the distribution of the stress on the beam and thus enhanced its bearing capacity. The findings of this work could be used as a frame of reference for similar components in engineering applications.
... As shown in Fig. 10, the pull-out resistance of densified bamboo nail ranged from 387 to 395 N. The pull-out resistance was originated from the interface friction between wood and bamboo nail. Since the pull-out speed was constant, the interface friction was mostly related to the surface characteristics of wood and bamboo nail [28,29]. In hence, densified extent had no significant influence on the pull-out resistance. ...
Nail connection is widely used in engineering and construction fields. In this study, bamboo nail was proposed as a novel connector for timber assemblies. Penetration depth of bamboo nail into wood was predicted and tested. The influence of nail parameters (length, radius and ogive radius) on penetration depth were verified. For both tested and predicted results, the penetration depth of bamboo nail increased with the increasing length, radius or ogive radius. In addition, the effect of densification on penetration depth or mechanical properties was evaluated. 1.12 g/cm³ was a critical density when densification was needed, and further increment of density would decrease the penetration depth of nail. The results of this study manifests that the proposed model is capable to predict the penetration depth of bamboo nail. These findings may provide new insight into efficiently utilization of bamboo resources.
... As sustainability becomes one of the major priorities in architecture, engineering and construction (AEC) sector, renewable materials like timber, bamboo and other bio-composite materials are widely used in various fields [9]. Over the past decade, an enormous research has been done and new trends, such as fiber reinforced polymer-to-wood (FRP-to-wood) connections [10] and steel timber composite (STC) connection systems [9], have been developed and studied to provide a reference for sustainable engineering applications. Recently, bamboo has also become one of the main materials in structural applications, and its performance is also very good [9,11,12]. ...
To improve the impact sound insulation performance of building floors and meet the objective requirements for living comfort of residents, in this article, three kinds of elastic cushion materials, Portuguese cork board, BGL insulation sound insulation foam board, and EPP polypropylene plastic foam board, are applied to the sound insulation of a light frame wood floor structure of the same bedroom and compared to the ordinary floor. This study uses the transfer function method and transient excitation method to measure the sound insulation, damping ratio, and elastic modulus of materials, as well as the sound insulation of the floor under the jumping excitation method of daily behavior. Through comparative analysis, the results and factors of improving the sound insulation performance of the floor are obtained, according to which three types of elastic cushion materials and the floor covering composed of them have higher vibration and noise reduction performance. Among them, the overall sound insulation performance of BGL board floor is the highest, followed by EPP board and cork board floor, and ordinary OSB floor is the lowest. Under the jumping excitation method, three floating floors can improve the impact sound insulation performance of the middle and low-frequency bands.
