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A mechanically consistent approach for stability verification of timber beams in compression and bending around the strong axis – part 2: experimental tests and numerical simulation Slender timber beams in bending can be designed using different methods in view of out‐of‐plane stability. Lateral torsional buckling may be verified either using the so called equivalent member method or by means of 2nd order calculations, considering equivalent imperfections. Applying current codes, however, determining the lateral torsional buckling resistance using either of these both methods, leads to different results. In this paper, the background of both verifications is investigated in deep. Moreover, as an alternative approach, a non‐linear calculation with an imperfection shape in affinity to the critical shape was presented in part 1 of this paper. By scaling the curvature, the same results as by the equivalent member method can be achieved. It was shown that plasticity effects can be considered as well. In this part 2, results of lateral torsional buckling tests on glued laminated timber beams are presented, with nearly ideal boundary conditions and load direction remaining vertical through‐out the test. Based on these test first tentative values can be obtained for the imperfection compatible with the alternative lateral torsional buckling approach presented. [ABSTRACT FROM AUTHOR]

As the carbon storage capacity of timber is recognized, there is growing interest in timber and wooden structures as a solution to various environmental problems. The use of Korean timber with substantial carbon storage capacity is required to reduce Korean carbon emissions and circulate timber resources. In this study, fire tests were conducted to investigate the charring properties of glued laminated timber columns made of Korean larch. The fire tests were conducted under both load-bearing and non-load-bearing conditions. The fire test results showed that the charring depth was affected by the corners of the section and that the load ratio had an insignificant influence on the charring depth when the load ratio was 0.9 or less. This study provides data that can be used to compare the charring properties of laminated wood produced using South Korean larch with the charring properties of foreign standards. This research provides reference data for developing fire-resistant design standards for timber structures made from South Korean timber. [ABSTRACT FROM AUTHOR]

Timber connections were prepared using glulam from tropical plantation species, focusing on key properties for dowel-type joints with half threaded bolts without nuts: Bolt bearing strength and bolt withdrawal capacity. Tests were performed according to ASTM standards. Three half-threaded bolt diameters (12 mm, 16 mm, and 20 mm) were tested in two loading directions, parallel and perpendicular to the grain, with 12 replicates for each configuration. Response Surface Methodology (RSM) using Design Expert Software was applied to optimize bolt diameter for both loading directions. Results showed that bolt bearing strength was higher in perpendicular loading, with the 12 mm bolt achieving 16.6 N/mm², compared to 6.01 N/mm² in parallel loading. Withdrawal capacities varied, with the 16 mm bolt showing the highest capacity in perpendicular loading at 54.2 kN. The study demonstrates that the 16 mm bolt exhibited the optimal diameter-to-embedment length ratio compared to 12 mm and 20 mm bolts, resulting in the highest withdrawal capacity. Consequently, the 16 mm bolt represented the best balance for achieving maximum withdrawal capacity. The optimization suggests using a 16 mm bolt for parallel loading to the grain and a 14 mm bolt for perpendicular loading. [ABSTRACT FROM AUTHOR]

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When oil palm lumber is considered for load-bearing products such as glued laminated timber (GLT), defined strength and stiffness values are required. In this investigation, combined GLT from oil palm wood is tested in compression parallel and perpendicular and glulam lamellas in tension parallel to the vascular bundles. Strength and Young´s modulus in compression and tension parallel increase with the density by power law relationship. In contrast to dicotyle-dons, the strength in construction size exceeds that of small, defect-free test specimens (compression strength perpendicular), are in the same range (tensile and bending strength parallel) or only a little below (compression strength parallel). The specimen size does not influence the strength. The ratio of fc,0 : fm : ft,0 is 1.2 : 0.8 ... 1.7 ... 2.6 : 1 and fc,0 : fc,90 = 2.7 ... 13.0 ... 32.6 : 1 for ρ = 200 ... 400 ... 600 kg/m³; the ratio of Ec,0 : Em : Et,0 is 1.2 : 1.3 : 1 for ρ = 400 kg/m³. Ashby´s performance indices for minimum weight design rise with the density; the strength-density performance indices are comparable or only slightly lower than that for structural size softwood, whereas the modulus-density performance indices are much lower. The challenge in use of oil palm wood for load-bearing construction products is the low stiffness. [ABSTRACT FROM AUTHOR]

Timber connections were prepared using glulam from tropical plantation species, focusing on key properties for dowel-type joints with half threaded bolts without nuts: Bolt bearing strength and bolt withdrawal capacity. Tests were performed according to ASTM standards. Three half-threaded bolt diameters (12 mm, 16 mm, and 20 mm) were tested in two loading directions, parallel and perpendicular to the grain, with 12 replicates for each configuration. Response Surface Methodology (RSM) using Design Expert Software was applied to optimize bolt diameter for both loading directions. Results showed that bolt bearing strength was higher in perpendicular loading, with the 12 mm bolt achieving 16.6 N/mm², compared to 6.01 N/mm² in parallel loading. Withdrawal capacities varied, with the 16 mm bolt showing the highest capacity in perpendicular loading at 54.2 kN. The study demonstrates that the 16 mm bolt exhibited the optimal diameter-to-embedment length ratio compared to 12 mm and 20 mm bolts, resulting in the highest withdrawal capacity. Consequently, the 16 mm bolt represented the best balance for achieving maximum withdrawal capacity. The optimization suggests using a 16 mm bolt for parallel loading to the grain and a 14 mm bolt for perpendicular loading.

Glued laminated timber made from hardwood is a sustainable structural product that is currently gaining momentum due to climatic changes and afforestation policy. Diversities in hardwood species have led to a lack of a complete standard for the production of glued laminated timber from hardwood in Europe. This paper addresses hardwood species available in Croatian forests, namely Carpinus Betulus L. (European hornbeam), Quercus Cerris L. (Turkey oak), and Acer Campestre L. (Maple), in terms of their suitability for the production of glued laminated timber. The suitability is assessed by a multi‐criteria analysis with seven criteria. Visual and physical properties include density, the occurrence of knots, and grain deviation in lamellas. Mechanical properties include the bending strength, modulus of elasticity, and shear strength of glue lines. In order to obtain physical and mechanical properties, corresponding experimental research has been carried out. Production costs have been evaluated in collaboration with the manufacturer. Results indicate a very high potential of European hornbeam and Turkey oak for the production of glued laminated timber. [ABSTRACT FROM AUTHOR]

To reduce the negative impact on the environment, architects, designers, and construction companies need to find and apply eco-friendly and sustainable building solutions. Due to its renewable nature and numerous advantages, timber has become an attractive substitute for steel and concrete in both residential and non-residential construction projects. However, timber application in the construction of grocery stores is a relatively new concept. The purpose of this research is to propose three alternative timber-based structural systems for a grocery store in Lithuania and to select the most efficient option based on multi-criteria decision-making methods. Three alternative glued laminated timber (glulam) structural systems—the glulam column and truss system, the glulam three-hinge frame system, and the glulam column and double-tapered beam system—were designed. The systems were evaluated against ten criteria, reflecting structural properties, cost efficiency, assembling complexity, and aesthetics. Multiple-criteria assessments by the COmplex PRoportional ASsessment (COPRAS) method and simple additive weighting (SAW) method revealed that the best-performing alternative is the glulam column and double-tapered beam system due to the lower cost of load-bearing structures, the smaller quantity of required steel details and fittings, and the highest maximum utility ratio according to serviceability limit states compared to other alternatives. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of composite box beam combined with cold-formed thin-walled steel and glued laminated timber to develop green building structures while improving the load-carrying capacity of a single steel girder and glued timber girder. Two composite beams composed of laminated timber and Q235 cold-formed thin-walled steel were designed and fabricated. Then, the shear performance test with quadratic loading was carried out to analyze the load carrying capacity, damage modes, and deformation characteristics of the test beams, as well as their influencing factors. Subsequently, a finite element model of the composite beam was established, and the loading mode was the same as that of the test to further study the parameters affecting the shear performance of the composite beam. The results of the study indicate that steel and glued timber in composite beams connected by adhesive bonding can work and deform together under load and each give full play to its material properties, especially the composite beams, which exhibit higher shear strength than a steel or timber beam. The effects of parameters such as steel cross-sectional area, shear span ratio, steel skeleton form, and steel cross-sectional strength on the shear capacity of the composite beams were observed, among which the shear span ratio had the greatest effect on the shear capacity of the composite beams. The shear capacity decreased by 14.3% and 19.5% when the shear span ratio was increased from 1.5 to 2.0 and 2.5, respectively. The shear capacity of the combined composite beams increased by 10.6%, 6.3%, and 5.8% when the thickness was increased from 1.5 mm to 2.0 mm, 2.5 mm, and 3.0 mm, respectively. When the combination of the steel cross-section was a box beam, the overall shear-bearing capacity could be increased by 12% compared with the "I" type composite beam, although its shear stiffness was close to that of the "I" section composite beam. [ABSTRACT FROM AUTHOR]

The mechanical properties of materials such as lumber (L), glued laminated timber (GLT), cross-laminated timber (CLT), and Ply-lam CLT (P), which are laminated in cross layers, were compared. As a result, the modulus of elasticity (MOE) was 9.7 to 10.3 GPa, showing no significant difference between the materials. Modulus of rupture (MOR) of L and GLT showed higher strength than that of CLT and P. MOR of CLT and P was at the same level, and there was no difference in strength according to the plywood and lumber arranged alternately. Alternatively, there was a difference in the coefficient of variation of the materials, and CLT and P was 20.2% and 11.8%, respectively; therefore, uniform properties can be secured when using plywood. The compression strength showed the highest compression strength in the order of GLT, L, P, and CLT. P was failure by buckling+delamination, but other materials showed failure by only buckling. The adhesion of P passed the glulam standard (7.0 MPa), and the delamination ratio was very low at 0.41%. It can be used together with CLT. This study is expected to be used as basic data for establishing quality standards.

The aim of this study was to increase the economic efficiency of industrial robots (IR) when subtractive machining timber beams. The most compact possible stack configuration, consisting of three different workpiece geometries, was calculated and machined. When compared to machining individual workpieces, a reduction of the process time is strived for. The workspace of the IR should be fully utilised by an optimised spatial stack configuration (number, location and spacing of workpieces). The stacks were calculated using a parameterised evolutionary solver model in Rhinoceros, Grasshopper, Galapagos and Opossum software. Machining trials were performed to obtain process time data for the IR and as a reference for a benchmark joinery machine (JM). By applying the newly introduced optimisation model, the process time per workpiece, when machining stacks instead of individual specimens, was reduced by 16%. This result was primarily achieved by shifting the share of non-machining time to machining time. When compared to individual machining with a JM, the process time of the IR is still higher. This fact can be outweighed by advantages of IRs such as cost, availability and flexibility, showing that the overall economic efficiency of IRs does in fact hold potential for prefabrication in the timber construction sector. [ABSTRACT FROM AUTHOR]

To reduce the negative impact on the environment, architects, designers, and construction companies need to find and apply eco-friendly and sustainable building solutions. Due to its renewable nature and numerous advantages, timber has become an attractive substitute for steel and concrete in both residential and non-residential construction projects. However, timber application in the construction of grocery stores is a relatively new concept. The purpose of this research is to propose three alternative timber-based structural systems for a grocery store in Lithuania and to select the most efficient option based on multi-criteria decision-making methods. Three alternative glued laminated timber (glulam) structural systems—the glulam column and truss system, the glulam three-hinge frame system, and the glulam column and double-tapered beam system—were designed. The systems were evaluated against ten criteria, reflecting structural properties, cost efficiency, assembling complexity, and aesthetics. Multiple-criteria assessments by the COmplex PRoportional ASsessment (COPRAS) method and simple additive weighting (SAW) method revealed that the best-performing alternative is the glulam column and double-tapered beam system due to the lower cost of load-bearing structures, the smaller quantity of required steel details and fittings, and the highest maximum utility ratio according to serviceability limit states compared to other alternatives.

Over the past 60 years, research has been carried out to provide glulam members with enhanced mechanical performance. Strengthening and reinforcing methods tested to improve the behavior of glulam beams have been predominantly focused on the use of Fiber-Reinforced Polymer (FRP) and steel products. Glulam beams with such modified cross-sections have been shown to be rational alternatives to steel and concrete counterparts in designing stiff and strong structural systems, attracting research interests for reliable long-span and heavy-loading applications. There is, however, no comprehensive study indicating which strengthening configuration is optimum. In this paper, glulam beams in bending are investigated through Reliability-Based Optimization (RBO) to propose a quantitative strengthening scheme. Seven strengthening and reinforcing configurations made in steel and FRP materials are accounted for glulam beams of lengths up to 30 m. RBO results indicate that glulam beams can be configured optimally with more sustainability. Additionally, it allows for the definition of specific safety levels for optimally reinforced and strengthened glulam beams at the lowest cost compared to non-strengthened glulam beams. Furthermore, prestressed material offers the most cost-effective way to create glulam beams that are more sustainable, strong, and safe. [ABSTRACT FROM AUTHOR]

Abstract Four kinds of glued laminated timber were produced (i.e., one with a glued edge-joint and the other three with nonglued edge joints) in the lamina at different positions toward the depth direction. Shear tests using an asymmetric four-point bending method were then conducted for these glued laminated timber specimens. The results showed that although the glued edge-joint specimens had the highest shear strength in all groups, the shear strength decreased as the distance from the adjacent nonglued edge-joint plane decreased. Furthermore, the shear strength of all specimens exceeded the standard shear design strength value (2.1 N/mm2) set by the Ministry of Land, Infrastructure, Transport and Tourism, Japan. Next, the shear strength of the nonglued edge-joint specimens was estimated based on that of the glued edge-joint specimens. Although the mean-estimated shear strength was lower than the mean-measured shear strength, the possibility of the shear strength changing based on the position of the nonglued edge-joint plane specimens from that of the glued edge-joint specimens was still estimated.

Despite many outdoors applications, the number of works aimed to determine the effect of changing conditions on the properties of glulam beams, in particular those produced in non-standard arrangements, is few. Therefore, the aim of this study was to assess changes in flexural strength properties (MOE, MOR) of the beams stored for 30 months in varying conditions. Analyzed variants of pine GLT beams included five-meter-long structural elements reinforced with oak timber, high-quality pine timber and steel rods stored both in the roofed shed outdoors and inside the climatic chamber. Moisture content of the beam varied significantly depending on the placement of the sensors (on the surface or inside the beam). The average modulus of elasticity after 30 months of storage decreased by approx. 7% compared to initial values. The results varied depending on both the assumed beam arrangement and the applied conditions. [ABSTRACT FROM AUTHOR]

A mechanically consistent approach for stability verification of timber beams in compression and bending around the strong axis, part 1 – derivations Slender timber beams in bending can be designed using different methods in view of out‐of‐plane stability. Lateral torsional buckling may be verified either using the so called equivalent member method or by means of 2nd order calculations, considering equivalent imperfections. However, at present determining the lateral torsional buckling resistance using either of these both methods, leads to different results. In this paper, the background of both verifications is investigated in deep. Moreover, as an alternative approach, a non‐linear calculation with an imperfection shape in affinity to the critical shape is presented in part 1 of this paper. If the curvature amplitude is scaled, the same results as by the equivalent member method are achieved. It is shown that plasticity effects can be considered with high precision as well. In part 2, results of experimental tests on lateral torsional buckling of glued laminated timber and laminated veneer lumber beams are presented, with nearly ideal boundary conditions and load remaining vertical through‐out the test. Based on these test first tentative values can be obtained for the imperfection compatible with the alternative lateral torsional buckling approach presented. [ABSTRACT FROM AUTHOR]

To improve wood structure processing efficiency, a palletizing robot suitable for loading and unloading glued laminated timber (GLT) has been developed. The robot comprises a six-axis connecting rod mechanism and a sponge sucker as a grasping actuator, which can enable the intelligent automatic loading and unloading and palletizing operations for small-sized GLT. Matlab robotics was used to construct the kinematic model of the GLT loading and unloading robot. Based on Matlab and Monte Carlo methods, the robot workspace was simulated and analyzed to determine the scope of the robot workspace. Using the high-order quintic and sixtic polynomial curve interpolation method, the trajectory of wood structure parts in the process of loading and unloading operations was planned, respectively, under the two conditions of staying and not staying. Tests verified that the simulation results of the pose of the end-effector were consistent with the actual pose of the robot. The robot's working range could be analyzed intuitively and effectively. The robot's operation trajectory planning provides data support and a parameter basis for the automatic control and program design of a loading, unloading and palletizing robot. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the potential of hardwoods harvested in Croatian forests for the production of glued laminated timber (glulam), mainly of those species for which there is no published performance assessment. Nine sets of glulam beams were produced: three sets using lamellas from European hornbeam, three sets from Turkey oak, and three sets from maple. Each set was characterized by a different hardwood species and surface preparation method. The surface preparation methods included planing, planing followed by sanding with fine grit, and planing followed by sanding with coarse grit. The experimental investigations included shear tests of the glue lines in dry conditions and bending tests of the glulam beams. The shear tests showed satisfactory performance of the glue lines for the Turkey oak and European hornbeam, but not for the maple. The results of the bending tests showed superior bending strength of the European hornbeam compared to the Turkey oak and maple. Planing followed by rough sanding of the lamellas was shown to have a significant influence on the bending strength and stiffness of the glulam from Turkey oak. [ABSTRACT FROM AUTHOR]

Abstract Juvenile wood (JW) can influence the performance of structural boards since it presents lower physical and mechanical properties. This study aimed evaluate the influence of JW proportion on density and modulus of elasticity (MOE) on boards for structural use. Pinus taeda logs 30 years old, had growth rings manually counted (on the pith to bark direction), and the first six rings were painted with color red (0-6), followed by blue (6.1-12), orange (12.1-18), green (18.1-24), and yellow (over 24.1), successively, and cut into boards. The proportion of each color was obtained by analysis of the transversal areas of boards with software. MOE was obtained by a nondestructive test. Multiple linear regression models were applied with 5% of significance. The estimated MOE indicates that boards with at least 57% of orange and green colors (between 12.1 – 24 years old) can achieve the minimum MOE value for using as structural as well as boards without red color but with the presence of green and yellow can have MOE bigger than 7000 MPa. The study indicates a behavior tendency about which proportion and mixed colors can affect the MOE of the board to be classified as structural.

Engineered wood products need alternatives of raw materials to their production. The hybrid Eucalyptus urograndis has great potential to supply the demand of this industrial sector. In this context, the present paper aims to analyse the feasibility of using Eucalyptus urograndis in glued laminated timber (glulam) production. To this end, four groups with ten glulam beams each, were produced and tested. An extensive experimental program was performed in order to determine: the stiffness and bending strength of the beams; and the compression strength parallel to grain of the beams. The performance of structural adhesives was verified based on shear tests of glue lines. The experimental mean of stiffness was higher than 14675 MPa and the characteristic value of compression strength parallel to grain achieved a value above 40 MPa. Nevertheless, failure mode of the glulam beams showed that finger-joints reduced bending strength. The glulam beams produced with Eucalyptus urograndis proved to be a feasible alternative due to their mechanical properties. However, this material presents difficulties in finger-joints adhesion. [ABSTRACT FROM AUTHOR]

Oil palm trunk biomass, abundant in tropical zones, can be utilized as raw materials for lumber-based products to serve the growing building industry; however, its relatively poor mechanical properties must be improved to meet structural requirements. This work aims to improve the properties of oil palm wood as a raw material for glued-laminated timber via thermal compression. Low-density (191–350 kg/m3) and medium-density (350–530 kg/m3) oil palm wood were thermally compressed at 200°C for 1 h with 40% and 25% target compression ratios, respectively. The thermally compressed oil palm experienced different degrees of compression throughout its thickness, which determined its density profile. Thermally compressed medium-density wood had a more uniform density, which makes it more favorable for structural usage allowing simpler connection design. Only the bending and tensile strengths in the parallel-to-grain direction of the thermally compressed medium-density wood met the requirements of a specific class of structural softwood timber. Block shear tests were performed to evaluate the feasibility of face-bonding the thermally compressed wood using a two-component polyurethane adhesive. All block shear test specimens had 100% wood failure percentages. Thus, the thermally compressed medium-density palm wood can be used for glued-laminated timber production under a condition where its own structural grade is established. [Display omitted] ● Oil palm wood was thermally compressed for improving its properties. ● Low and medium density oil palm wood were used for thermal compression. ● Compressed wood manufactured from medium density had more uniform density profile. ● Compressed wood's properties met requirement of certain class of structural softwood. ● Compressed wood had potential for glued laminated timber production. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of composite box beam combined with cold-formed thin-walled steel and glued laminated timber to develop green building structures while improving the load-carrying capacity of a single steel girder and glued timber girder. Two composite beams composed of laminated timber and Q235 cold-formed thin-walled steel were designed and fabricated. Then, the shear performance test with quadratic loading was carried out to analyze the load carrying capacity, damage modes, and deformation characteristics of the test beams, as well as their influencing factors. Subsequently, a finite element model of the composite beam was established, and the loading mode was the same as that of the test to further study the parameters affecting the shear performance of the composite beam. The results of the study indicate that steel and glued timber in composite beams connected by adhesive bonding can work and deform together under load and each give full play to its material properties, especially the composite beams, which exhibit higher shear strength than a steel or timber beam. The effects of parameters such as steel cross-sectional area, shear span ratio, steel skeleton form, and steel cross-sectional strength on the shear capacity of the composite beams were observed, among which the shear span ratio had the greatest effect on the shear capacity of the composite beams. The shear capacity decreased by 14.3% and 19.5% when the shear span ratio was increased from 1.5 to 2.0 and 2.5, respectively. The shear capacity of the combined composite beams increased by 10.6%, 6.3%, and 5.8% when the thickness was increased from 1.5 mm to 2.0 mm, 2.5 mm, and 3.0 mm, respectively. When the combination of the steel cross-section was a box beam, the overall shear-bearing capacity could be increased by 12% compared with the “I” type composite beam, although its shear stiffness was close to that of the “I” section composite beam.

Abstract When a glued laminated timber (GLT) beam with a round hole is subjected to a shear force and bending moment, the hole will crack and fail due to a large tensile stress perpendicular to the grain and shear stresses. If the stresses acting on the hole are known, it is possible to estimate the fracture load. However, it is necessary to obtain the stresses acting on the hole by finite element analysis, which is very time consuming. In this study, to easily estimate the fracture load, we proposed a formula to estimate the bearing capacity at the time of a hole fracture by obtaining the stress acting on the hole through finite element analysis and an approximate formula. The validity of the proposed formula was verified using the existing experimental data of a GLT beam. As a result, it was confirmed that the proposed equation can estimate the fracture load of GLT beams in Japan and that the proposed equation can estimate the fracture load of GLT beams in countries other than Japan with some accuracy.

The dimensions, particularly the depths, of glued laminated timber (GLT) beams are continuously increasing to realize, e.g., wide-span hall constructions or flexible office buildings. However, experimental investigations of large beams are unavailable because of the tremendous effort involved. Numerical simulation campaigns represent an alternative, but their results are heavily influenced by the modeling strategy, and therefore, a different influence of the beam depths on the bending strength was obtained. To predict this influence, also called size effect, we carried out a simulation program covering 8840 GLT beams ranging from 165 mm to 3300 mm in depth, using advanced modeling concepts including discrete cracking and plasticity.We observed a decreasing characteristic bending strength with increasing beam depths and an almost constant mean modulus of elasticity for both considered strength classes. Additionally, the influence of the beam length on the bending strength is analyzed, and it is shown that this influence can be described reasonably well with a simple analytical model based on Weibull’s strength theory. In conclusion, the effective material behavior of GLT is affected by its dimensions. For large beams, this influence is difficult to obtain experimentally; however, numerical simulation campaigns seem to be a promising way to accomplish this.

The paper deals with the analysis of the load-carrying capacity of a timber semi-rigid connection created from a system of two stands and a rung. The connection was made from glued laminated timber with metal mechanical dowel-type fasteners. Not only a common combination of bolts and dowels, but also fully threaded screws were used for the connection. The aim of the research and its motivation was to replace these commonly used fasteners with more modern ones, to shorten and simplify the assembly time, and to improve the load-carrying capacity of this type of connection. Each of these two types of connections was loaded statically, with a slow increase in force until failure. The paper presents results of the experimental testing. Three specimens were made and tested for each type of the connection. Experimental results were subsequently compared with numerical models. The achieved results were also compared with the assumption according to the currently valid standard. The results indicate that a connection using fully threaded screws provides a better load-carrying capacity. [ABSTRACT FROM AUTHOR]

Four kinds of glued laminated timber were produced (i.e., one with a glued edge-joint and the other three with nonglued edge joints) in the lamina at different positions toward the depth direction. Shear tests using an asymmetric four-point bending method were then conducted for these glued laminated timber specimens. The results showed that although the glued edge-joint specimens had the highest shear strength in all groups, the shear strength decreased as the distance from the adjacent nonglued edge-joint plane decreased. Furthermore, the shear strength of all specimens exceeded the standard shear design strength value (2.1 N/mm2) set by the Ministry of Land, Infrastructure, Transport and Tourism, Japan. Next, the shear strength of the nonglued edge-joint specimens was estimated based on that of the glued edge-joint specimens. Although the mean-estimated shear strength was lower than the mean-measured shear strength, the possibility of the shear strength changing based on the position of the nonglued edge-joint plane specimens from that of the glued edge-joint specimens was still estimated. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the mechanical properties of laminated beams containing selected wood species in the tension zone using a four-point bending test. Three beam types were manufactured with respect to the timber used in the tension zone, i.e., beams containing oak or beech timber of I and II quality class and pine timber with no defects (as defects had been removed). The manufactured beams were assessed with respect to bending strength and the modulus of elasticity. The obtained results were compared with the performance of BSH (Industrial beams GL made in Germany—Brettschichtholz) industrial beams. We concluded that beams made from pine timber are an appropriate alternative to spruce beams. The static bending strength of the beams made with hardwood faces was 70% higher than that of beams made with pine wood. All types of beams manufactured in the laboratory met the requirements of at least the GL24c class. [ABSTRACT FROM AUTHOR]

Engineered wood products need alternatives of raw materials to their production. The hybrid Eucalyptus urograndis has great potential to supply the demand of this industrial sector. In this context, the present paper aims to analyse the feasibility of using Eucalyptus urograndis in glued laminated timber (glulam) production. To this end, four groups with ten glulam beams each, were produced and tested. An extensive experimental program was performed in order to determine: the stiffness and bending strength of the beams; and the compression strength parallel to grain of the beams. The performance of structural adhesives was verified based on shear tests of glue lines. The experimental mean of stiffness was higher than 14675 MPa and the characteristic value of compression strength parallel to grain achieved a value above 40 MPa. Nevertheless, failure mode of the glulam beams showed that finger-joints reduced bending strength. The glulam beams produced with Eucalyptus urograndis proved to be a feasible alternative due to their mechanical properties. However, this material presents difficulties in finger-joints adhesion.

The paper deals with the analysis of the rotational stiffness of a semirigid connection created from a system of two stands and a rung. The connection was made from glued laminated timber with metal mechanical dowel-type fasteners. Not only a common combination of bolts and dowels but also fully threaded screws were used for the connection. The aim of the research and its motivation was to replace commonly used fasteners with more modern ones, to shorten and simplify the assembly time, and to improve the load-carrying capacity of this type of connection. Each of these two types of connection was loaded to the level of 60%, 80%, and 100% of the ultimate limit state value. Subsequently, the rotational stiffness was determined for each load level after five loading and unloading cycles. This paper presents the results and comparison of the experimental testing and the numerical modeling. The obtained results were also compared with the assumption according to the currently valid standard. [ABSTRACT FROM AUTHOR]

The non-linear finite element simulation of the ASTM shear and pre-stressed compact tension tests was conducted. Tested specimens were cut from the glued laminated timber made of European spruce (Picea abies) with the lamina thickness of 10.5 mm and 45 mm. The 2D homogeneous orthotropic constitutive model of the tensile-shear fracture in timber, which has been proposed by the authors, was used. The model calibration was adopted from the authors' recent experimental study. The numerical results show that the model can adequately reproduce both the experimental response and the crack pattern, which in certain cases comprises of cracking parallel or perpendicular to fibers. Furthermore, the results confirm that the value of the parameter fASTM xy, obtained from ASTM shear test as the maximum attained force divided by the shearing area, represents the averaged stress at the failure plane, while the extreme stress experienced by the material is much higher. [ABSTRACT FROM AUTHOR]

Engineered wood products (EWP) such as glulam beams are gaining more and more popularity due to several advantages resulting from the wood itself, as well as the constant search for structural materials of natural origin. However, building materials face some requirements regarding their strength. Thus, the study aimed to assess the static bending strength of structural beams produced with the use of pine wood, after the periodic loading of approximately 80 kN for a year. The manufactured beams differed in the type of facing layers, i.e., pine timber with a high modulus of elasticity and plywood. The produced beams, regardless of their structure, are characterized by a similar static bending strength. Moreover, it has been shown that the loading of beams in the range of about 45% of their immediate capacity does not significantly affect their static bending strength and linear modulus of elasticity. [ABSTRACT FROM AUTHOR]

Various factors affect the bonding quality of elements used for timber construction. This review includes literature studies and personal experiences related to relevant technological variables defining glue bond performance in glue-laminated timber elements during their service life. The gluing of hardwood species receives special focus as it is considered by the industry to be the most challenging process for implementation. In particular, the effects of wood species, type of adhesive, glued-wood surface quality, physical and/or chemical modification of the wood, technological solutions for gluing, and varying climatic conditions during the use phase (relative humidity, temperature, air circulation, etc.) are considered. In addition, overlapping of individual influencing factors often leads to problems with bonding, thus requiring strongly integrating measurement methods (e.g. NIR spectroscopy). The causes of variations in the results when glued wood is tested using different standardized methods are discussed. A list of open research questions is provided, and problem solutions are recommended based on systematized cutting-edge knowledge. The aim of the work is to systematize the state of knowledge of wood gluing to create a basis for controlled and stable manufacturing processes. The progress of the work will be reported in further publications. [ABSTRACT FROM AUTHOR]

Abstract Shear experiments on mortise and tenon joints with top and bottom notches in the beam end were conducted with the length of the tenon as a variable. In addition, material experiments were performed to investigate the structural performance of the fracture modes of the joint. The experimental results show that when the lower notch at the beam end experiences splitting, the shear forces were identical for different tenon lengths and did not decrease. In addition, the deformation performance of the joint up to yielding was largely due to the compressive deformation perpendicular to the grain of the wood on the sides of the tenon. Based on the theory of the calculation method of the splitting strength of a notched beam, a formula for the splitting strength when the end of the beam is moment-resisting was proposed. It was confirmed that the proposed formula could estimate the shear force that caused the splitting fracture of the lower notch. In addition, the increase in shear force after the lower notch experienced splitting fracture was due to the increase in clamping force of the beam end due to rotational deformation.

Abstract Three-point bending tests were performed on specimens of glued laminated timber with different specimen heights to failure to determine the relationship between specimen height and bending strength under tension perpendicular to the grain. For the three-point bending tests, two types of glued laminated timber composed of homogeneous grade timber, as specified in the Japanese Agricultural Standard, were used. The laminae used for the glued laminated timber were L80 grade Scots pine and L110 grade Scots pine. The specimens used in the three-point bending tests had dimensions of 105 mm (width) and 10–300 mm (height). The experimental results showed that the bending strength decreased as the specimen height increased, but the rate of decrease in the bending strength decreased with increasing specimen height when the specimen height exceeded 100 mm. From the relationship between the bending strength and specimen height, parameters that fit Bažant’s size-effect law were derived, and for a specimen height of approximately 100 mm, the bending strength was equal to the perpendicular-to-the-grain tensile strength.

To improve wood structure processing efficiency, a palletizing robot suitable for loading and unloading glued laminated timber (GLT) has been developed. The robot comprises a six-axis connecting rod mechanism and a sponge sucker as a grasping actuator, which can enable the intelligent automatic loading and unloading and palletizing operations for small-sized GLT. Matlab robotics was used to construct the kinematic model of the GLT loading and unloading robot. Based on Matlab and Monte Carlo methods, the robot workspace was simulated and analyzed to determine the scope of the robot workspace. Using the high-order quintic and sixtic polynomial curve interpolation method, the trajectory of wood structure parts in the process of loading and unloading operations was planned, respectively, under the two conditions of staying and not staying. Tests verified that the simulation results of the pose of the end-effector were consistent with the actual pose of the robot. The robot’s working range could be analyzed intuitively and effectively. The robot’s operation trajectory planning provides data support and a parameter basis for the automatic control and program design of a loading, unloading and palletizing robot.

When a glued laminated timber (GLT) beam with a round hole is subjected to a shear force and bending moment, the hole will crack and fail due to a large tensile stress perpendicular to the grain and shear stresses. If the stresses acting on the hole are known, it is possible to estimate the fracture load. However, it is necessary to obtain the stresses acting on the hole by finite element analysis, which is very time consuming. In this study, to easily estimate the fracture load, we proposed a formula to estimate the bearing capacity at the time of a hole fracture by obtaining the stress acting on the hole through finite element analysis and an approximate formula. The validity of the proposed formula was verified using the existing experimental data of a GLT beam. As a result, it was confirmed that the proposed equation can estimate the fracture load of GLT beams in Japan and that the proposed equation can estimate the fracture load of GLT beams in countries other than Japan with some accuracy. [ABSTRACT FROM AUTHOR]

The current trend in tall timber building design is a testament to the need for innovative structural systems. In this paper, a new, coupled cross-laminated timber (CLT) system is illustrated. The CLT wall systems are equipped with energy dissipation systems, and the continuous medium method (CMM) design principle is used. The CMM is a simplified (approximate) elastic method that can be used to analyze and design the preliminary geometries of coupled wall systems for uniform or quasi-uniform structures. The energy dissipation components of the structure are coupling beams between the CLT walls, and an energy-dissipating buckling restrained-brace (BRB) hold-down. Performance of the structure was evaluated using incremental dynamic analysis. [ABSTRACT FROM AUTHOR]

Abstract These experiments sought to empirically determine how the initial tightening force influences the ratio of the axial bolt force to the tensile load (load factor) and the load required to separate the joint interface (interface separation load) in tensile bolted joints of glued laminated timber. Load factor decreases with increasing initial tightening force; however, this tendency is reduced the greater the washer–member-end distance. In addition, tensile stiffness increases with decreasing load factor, and the interface separation load increases with increasing initial tightening force. However, in actual testing, the joint interface separated at a lower load that predicted mathematically based on the load factor and initial tightening force.

European beech glued laminated timber European beech wood (Fagus sylvatica L.) is currently used only to a very limited extent for the production of glued laminated timber (glulam). Although this most widespread hardwood species in Central Europe has a very high potential in terms of strength and stiffness, besides its application to railway construction (as sleepers), it has so far been mainly used by the furniture industry and for heating purposes. One main reason for this is the lack of standards and guidelines regulating the production, quality control and specifying the mechanical properties of beech glulam. In this paper, an extensive research project aiming at determining the mechanical properties of beech glulam is presented. Based on bending, tension, compression, buckling and shear tests on beech glulam specimens of different cross sections and strength classes and taking into account previous investigations as well as the results of numerical simulations, the mechanical properties of beech glulam are determined. Furthermore, formulas to account for the effect of the member size on the bending and shear strength as well as buckling curves for the design of columns made of beech glulam are presented. [ABSTRACT FROM AUTHOR]

This paper presents large-scale bending test, up to 19 m length, on glued laminated timber (GLT) beams with well-known beam setup and a model to predict the tensile strength of finger joint connections (FJ). Machine graded timber boards, with information about the dynamic stiffness and local knottiness were used to fabricate 12 GLT beams. The position of the timber boards were tracked throughout the GLT fabrication. To quantify the quality of the FJ additional FJ were fabricated and tested in tension. Based on the results, a model to predict their strength properties based on the grading information of the involved timber boards was developed using maximum likelihood estimation for censored data. [ABSTRACT FROM AUTHOR]

Shear experiments on mortise and tenon joints with top and bottom notches in the beam end were conducted with the length of the tenon as a variable. In addition, material experiments were performed to investigate the structural performance of the fracture modes of the joint. The experimental results show that when the lower notch at the beam end experiences splitting, the shear forces were identical for different tenon lengths and did not decrease. In addition, the deformation performance of the joint up to yielding was largely due to the compressive deformation perpendicular to the grain of the wood on the sides of the tenon. Based on the theory of the calculation method of the splitting strength of a notched beam, a formula for the splitting strength when the end of the beam is moment-resisting was proposed. It was confirmed that the proposed formula could estimate the shear force that caused the splitting fracture of the lower notch. In addition, the increase in shear force after the lower notch experienced splitting fracture was due to the increase in clamping force of the beam end due to rotational deformation. [ABSTRACT FROM AUTHOR]

The paper presents the experimental results obtained for bending strength parallel to the fibers of a beam element made of hardwood (deciduous) glued laminated timber. At the same time, tests were carried out to determine the physico-mechanical characteristics of the wood specimens, in order verify the wood species.