The glulam knee-braced frames and braced frames are both conventional structural systems that are generally adopted in engineering practice. However, it remains a question what are the advantages and ...challenges of the knee-braced frames compared with the braced frames and how to choose the appropriate lateral-resisting structures for the projects under a given design requirements. This paper provides numerical models of 3- story, 5- story, 6- story and 9- story glulam braced frames and glulam knee-braced frames with the same architectural plan view. Increment dynamic analysis (IDA) is performed to determine the limit state of MaxISDR (maximum inter-story drift ratio) for the glulam braced frames and the glulam knee-braced frames under different seismic hazard levels, i.e., IO (Immediate Occupancy), LS (Life Safety), CP (Collapse Prevention) and CD (Complete Destroy). Fifty earthquake records are adopted for the subsequent probabilistic seismic demand analysis based on the MaxISDR and ResISDR (residual inter-story drift ratio) damage indices. The fragility curves of these two types of structures are highlighted. The results show that, the limit state of MaxISDR for the glulam braced frames under the IO, LS, CP and CD hazard level are recommended to be 0.6%, 1.2%, 2.0% and 3.5% respectively. The limit state of MaxISDR for the glulam knee-braced frames under the IO, LS, CP and CD hazard levels are recommended to be 1.0%, 2.0%, 3.2% and 5.5% respectively. In addition, for the structural height that below 6 stories, the knee-braced frames have lower probability of MaxISDR exceedance than the braced frames under the earthquake with high PGA and lower probability of ResISDR exceedance than the braced frames. However, for the structural height of 9-stories, the recoverability of the knee-braced frames decreases rapidly. Adding some braces to the knee-braced frames can be a good solution to increase the lateral stiffness of the structures. The comparison results may provide technical reference for the structural design of glulam structures.
•Numerical models of glulam braced frames and knee-braced frames with the same architectural plan view are provided.•Increment dynamic analysis (IDA) is performed to determine the limit state of MaxISDR for selected structures.•Probabilistic seismic demand analysis and fragility curves of these two types of structures are discussed.
The rapid progression of mass timber structures towards greater spans presents a challenge for the flexural behavior of glulam beams. In this study, this challenge was addressed by reinforcing the ...glulam beams with prestressing tendons which were bonded to the glulam beams by epoxy resin. The objective of this study is to investigate the influence of prestressing force levels and bonded types on the flexural behavior of prestressed glulam beams. Four-point bending tests were conducted on twelve glulam beams prepared by unreinforced, unbonded prestressed or bonded prestressed techniques. Experimental results revealed that the glulam beams exhibited increased ductility under prestressing force. Compared with unreinforced beams, the prestressed beams demonstrated a remarkable increase of up to 78.8 % in flexural capacity and 13.5 % in flexural stiffness. For the prestressed beams, the flexural capacity increased as prestressing force increases. Compared with the unbonded prestressed beams at the same prestressing force level, the bonded ones exhibited higher flexural capacity and flexural stiffness. Additionally, the bonded prestressed beams exhibited a slight increase in tendon stress at the end of the prestressing tendon during loading, indicating favorable bonding behavior of epoxy resin. Numerical models were developed to predict the non-linear flexural behavior of prestressed beams, and the numerical results showed good agreements with the experimental results. Parametric analysis based on the numerical models was conducted on the prestressed beams at various prestressing force levels. The positive effect of the bonded prestressed method on the flexual behavior of glulam beams was further substantiated.
•Bending tests were conducted on unbonded and bonded prestressed glulam beams.•The influence of prestressing force levels and bond types was investigated.•Numerical models were developed to predict the nonlinear flexural behavior.•The enhancement mechanism was further elucidated through parametric analysis.
This paper presents an experimental study aimed at characterizing the lateral cyclic behaviour of Glulam (GL), Laminated Veneer Lumber (LVL), and Glued Laminated Veneer Lumber (GLVL) shear walls ...anchored to the foundation by means of conventional hold downs and angle brackets, which are fastened to the timber walls with annular ring nails. Monotonic and cyclic tests are conducted on these mechanical anchors, with hold down connections tested under tensile loads and angle bracket connections under shear loads. Withdrawal tests on annular ring nails embedded in GL, LVL, and GLVL elements are also conducted, to investigate the withdrawal response of the fasteners. The experimental tests reveal that the lateral behaviour of GL, LVL, and GLVL shear walls is similar to that of Cross-Laminated Timber (CLT) shear walls, primarily governed by the wall base connections and by the wall geometry. Hold down and angle bracket connections exhibited a mechanical behaviour governed by the steel-to-timber joints, to large extent comparable with that of typical hold downs and angle brackets fastened to CLT elements. Generally, higher ductility and lower load carrying capacity were reached by hold downs and angle brackets fastened to GL elements compared to those reached by hold downs and angle brackets fastened to LVL and GLVL elements. All quantities relevant for the seismic design, such as stiffness, load carrying capacity, ductility, and overstrength factors are calculated and discussed through the paper. These quantities are then compared with results from different experimental investigations on hold downs and angle brackets fastened to CLT elements available in the literature. Finally, an analytical model for the calculation of the lateral load carrying capacity of the shear walls is presented and used to verify that the same calculation models used for CLT shear walls can be adopted for GL, LVL, and GLVL shear walls.
•The lateral behaviour of Glulam, LVL and GLVL shear walls is investigated.•The cyclic behaviour of hold downs and angle brackets fastened to Glulam, LVL and GLVL elements is investigated.•Mechanical properties and overstrength factors of the wall base connections are presented.
•A-state-of-art review was conducted on novel engineered wood and bamboo composites.•Attentions were paid to their manufacturing technologies, modeling approaches, and mechanical ...properties.•Mechanical properties of the engineered wood and those of the engineered bamboo were compared.•Several structural application cases of these engineered wood/bamboo composites were illustrated.
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.
•Carbon-based FRP fabrics increase the load bearing capacity, energy dissipation capacity and stiffness values of the column-beam joints region.•The load-carrying capacity of the angle joint is ...higher than that of the ALUMIDI fastener.•As the dimensions of the column and beam elements increase, their load carrying capacities increase.
Glulam columns and beams are structural wood engineering products, which are formed by gluing the timbers together in parallel with the help of glue and are widely used in the construction of wood structures. Steel plates, aluminum plates or simply wooden parts are commonly used at the joints of wood structures. Steel elements that are often used as joints can corrode and also aluminum plates are not resistant to heat. For this reason, the use of non-metallic fasteners is one of the topics that have been emphasized recently. In this study, it is aimed to strengthen the joints of glulam column-beam connection with carbon fiber reinforced polymer. For this purpose, 2 column-beam joint samples were produced from each connection type using WV90080 and ALUMIDI 160, WV90110 and ALUMIDI 200 connection elements. One of the samples produced in each connection element was wrapped, and the other was not. The column-beam joint samples produced were subjected to the load–displacement test within the framework of the experiment. It was determined that the load bearing capacity, energy dissipation capacity and stiffness values of the samples whose column-beam connection area was strengthened. It has been specified that reinforcement with carbon-based FRP fabric increases the strength and durability of the column-beam connection area.
The research and development of timber and timber-hybrid systems depends heavily on the testing of large or full-scale structural components, which is often limited by laboratory space and budget ...constraints. Testing of small-scale samples is an alternative approach which can avoid costly experimental campaigns; however, little is known about evaluation of serviceability performance measures, including natural frequency and stiffness, which typically govern the design of elements in timber and timber-hybrid long-span systems. Downscale testing of timber is known to be susceptible to changes in material properties with size, the so-called ‘size effect’, but existing research into the size effect in timber focuses on strength rather than serviceability parameters. This work explores the effect of scaling down Glulam and hybrid carbon fibre (CFRP) reinforced Glulam beams, by comparing the dynamic and static performance of beams tested at both full-scale and approximately half scale. Outcomes of this experimental study indicate that serviceability parameters present small variations with scale, whereas strength parameters are affected by size effect in being consistently smaller in the full-scale samples when compared to their small-scale versions. It was also observed that tension-only reinforcement in hybrid CFRP–timber beams appeared to reduce the size effect in both static and dynamic parameters.
•Glulam and hybrid beams presented good correlation between scales in serviceability.•CFRP reinforcement in tension zone counteracts the size effect on bending strength.•Scaling of testing samples allows more repetitions and simpler experimental setup.
Currently, there is limited knowledge of the dynamic response of taller glue laminated (glulam) timber buildings due to ambient vibrations. Based on previous studies, glulam frame connections, as ...well as non-structural elements (external timber walls and internal plasterboard partitions) can have a significant impact on the global stiffness properties, and there is a lack of knowledge in modeling and investigation of their impact on the serviceability level building dynamics. In this paper, a numerical modeling approach with the use of “connection-zones” suitable for analyzing the taller glulam timber frame buildings serviceability level response is presented. The “connection-zones” are generalized beam and shell elements, whose geometry and properties depend on the structural elements that are being connected. By introducing “connection-zones”, the stiffness in the connections can be estimated as modified stiffness with respect to the connected structural elements. This approach allows for the assessment of the impact of both glulam connection stiffness and non-structural element stiffness on the dynamic building response due to service loading. The results of ambient vibration measurements of an 18-storey glulam timber frame building, currently the tallest timber building in the world, are reported and used for validation of the developed numerical model with “connection-zones”. Based on model updating, the stiffness values for glulam connections are presented and the impact of non-structural elements is assessed. The updating procedure showed that the axial stiffness of diagonal connections is the governing parameter, while the rotational stiffness of the beam connections does not have a considerable impact on the dynamic response of the glulam frame type of building. Based on modal updating, connections exhibit a semi-rigid behavior. The impact of non-structural elements on the mode shapes of the building is observed. The obtained values can serve as a practical reference for engineers in their prediction models of taller glulam timber frame buildings serviceability level response.
•An alternative approach to model connections in taller glulam timber frame buildings with “connection-zones” is proposed.•The impact of non-structural elements on the serviceability level response is explored.•The semi-rigid behavior in glulam timber connections has been shown and estimates of the stiffness range for these connections are provided.
•Full-scale glulam frames with BRBs were tested under cyclic loading.•BRBs improve the glulam frames’ strength, stiffness and energy dissipation.•Two types of timber-steel interface connections were ...strong and stiff to work with BRBs efficiently.•The capacity design approach proved to work well.
This experimental study investigates cyclic performance of a timber-steel hybrid structural system consisting of glulam frames and buckling restrained braces (BRBs). The BRBs are designed as ductile elements in the hybrid system to dissipate energy under seismic loading. Following the capacity design approach, two full-scale 8 m wide and 3.6 m high BRB glulam frame (BRBGF) specimens were tested. The BRBs were connected to the glulam frames by pins and steel gusset plates. Dowelled connections with inserted steel plates were used in one specimen to connect the glulam members while screwed connections with steel side plates were used in the other specimen. The test results showed that the integration of BRBs into the glulam frames significantly improved the load carrying capacity and energy dissipation. Both BRBGF specimens achieved a minimum ductility factor of 3.0 based on CEN method. The connections and the glulam members were well protected without significant damage. Therefore, the dowelled connections and screwed connections provided solutions to engage BRBs efficiently to resist lateral loads in this hybrid system.
Laminated wood beams have become a preferred solution compared to standard solid beams due to their ability to carry larger loads and in larger spans (greater distances). The increase in wood usage ...and the varieties of its applications have highlighted the necessity for the enhancement of the maximum load-carrying capacity and overall load-displacement behavior of laminated wood beams. Among the various strengthening options applied to increase the maximum load-carrying capacity and material performance, the most commonly preferred choice is strengthening with CFRP (Carbon Fiber Reinforced Polymer). Within the scope of this study, a total of 26 glulam wooden beam test specimens were produced. Variations were introduced in terms of the number of laminated layers, the distance between finger joint connection points, finger joint orientation, the use or lack of use of strenghthening, and distance between CFRP strips. The specimens were subjected to monotonic static loading through a four-point bending test, allowing for an examination of how these variables influenced the bending behavior. The values obtained from the experimental study and the numerical study conducted using the finite element software ABAQUS were compared and interpreted. These values included ultimate load capacity, displacement at ultimate load, initial stiffness, displacement ductility, and energy dissipation capacity. Based on the conducted analyses, it was observed that the strengthening method involving CFRP strips developed within the extent of this study significantly increased the load-bearing capacity of finger jointed glulam wooden beams. Furthermore, it was shown to have a highly positive impact on the overall load-displacement behavior.
Earthquake resistant frame using diagonal glulam columns and steel tie rods are suggested as an innovative timber structure system, implemented in a real building project. This structure system ...contains glulam columns resisting lateral and vertical load, enables buildings to have flexible architectural space within them. To confirm initial stiffness and strength, a loading test for a partial frame of this structure was carried out. In addition, method for creating stress analysis model of this frame for structure design is suggested by FEM analysis tracing the result of the experiment.
