In recent years, wood has become an increasingly popular building material for its environmental friendliness. Large-span timber structures are in high demand, of which the spliced joints play an ...important role for the main structural members. In this research, six specimens with two connection configurations, i.e., the slotted-in-steel-plate connection (SC) and the cover-plate connection (CC), were designed and subjected to cyclic loading tests. Besides the traditional data acquisition system, contact-free displacement measurement was also applied. The feasibility was verified since the moment-rotation curves obtained through the two methods showed strong consistency. Through the analysis of the mechanical properties of the joints, different methods for the determination of the yielding point of the specimens were compared and discussed. The test results show that the ultimate strength and stiffness of the CC connection were 59.04% and 187.7% higher than that of the SC connection, whereas the ductility of the former was 77.02% lower than that of the latter. Factors influencing on their mechanical properties were further analyzed. It is noted that while the ultimate strength is dominated by the steel plates, the stiffness and ductility depend more on the glulam elements and fasteners. Recommendations were also proposed as a design basis for the two types of connections.
•Two types of spliced joints for large-span timber structures were designed. Six full-scale specimens were tested.•The mechanical properties of the connections were compared and analyzed, and suggestions for improvement were proposed.•PTV was applied to obtain the displacement data. The applicability of contact-free measurement was verified.•Methods for the yielding definition were compared. EEEP method is suitable for specimens with obvious brittleness.
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•Component method for moment-resistant timber connections with glued-in steel rods.•Moment–rotation behavior of the ductile glulam beam-to-column connections.•Equivalent components ...for steel box section connecting elements.•Development of the theoretical model and evaluation using experimental results.
This paper presents an analytical method of the determination of the moment resistance, initial stiffness and the rotation capacity of glulam beam–column connections with glued-in rods. The methodology is based on the component method and is implemented using appropriate mechanical models. As a simplified component of the steel box sections, the substitute T-stub in the model is well verified by the experimental results, whether with or without the transverse web stiffeners. On the basis of the mechanical properties of the individual components such as initial stiffness, load resistance and a further force–deformation relationship, the moment–rotation curves of the entire joint can be obtained. The proposed model is evaluated against the experimental results, which shows good agreement between the two.
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•Experimental investigation under indoor environment was conducted.•The influence of loading levels and the number of shear connections on long-term deformations.•Long-term ...deflection, interface slip, and timber strain were measured and analyzed.•Time-dependent behaviour of timber-concrete composite beams were predicted.
This paper presents the results of long-term experiments performed on three timber-concrete composite (TCC) beams. An innovative fabricated steel plate connection system, which consists of screws and steel plates embedded in concrete slabs, was adopted in the TCC beam specimens. The adopted shear connection can provide dry-type connection for TCC beams. Steel plates were embedded in concrete slabs while the concrete slab was constructed in factories. The timber beam and concrete slab can be assembled together using screws at the construction site. In this experimental programme, the beam specimens were subjected to constant loading for 613 days in indoor uncontrolled environments. The influence of long-term loading levels and the number of shear connections on the long-term performance of TCC beams was investigated and discussed. The mid-span deflection, timber strain, and interface relative slip at the positions of both connections and beam-ends were recorded throughout the long-term tests. It was found the long-term deflection of the TCC beam increased by approximately 60% while the long-term loads were doubled. Under the influence of the variable temperature and humidity, the TCC specimens with 8 shear connections showed slighter fluctuations compared with the TCC beam with 6 shear connections. In the 613-day observation period, the maximum deflection increment recorded was 6.56 mm for the specimen with eight shear connections and 20% loading level. A rheological model consisting of two Kelvin bodies was employed to fit the curves of creep coefficients. The final deflections predicted of all specimens at the end of 50-year service life were 2.1~2.7 times the initial deflections caused by the applied loads. All beam specimens showed relative small increments in mid-span deflection, strain and relative slip over time without any degradations, demonstrating the excellent long-term performance of TCC beams using the innovative steel plate connection system, which is also easily fabricated.
This paper presents a novel approach to non-standard timber assembly – Robotic Timber Construction (RTC) – where robotic fabrication is used to expand additive digital fabrication techniques towards ...industrial full scale dimensions. Featuring robotic systems that grasp, manipulate, and finally position building components according to a precise digital blueprint, RTC combines robotic assembly procedures and advanced digital design of non-standard timber structures. The resulting architectural morphologies allow for a convergence of aesthetic and functional concerns, enabling structural optimisation through the locally differentiated aggregation of material. Initiated by the group of Gramazio Kohler Research at ETH Zurich, this approach offers a new perspective on automated timber construction, where the focus is shifted from the processing of single parts towards the assembly of generic members in space. As such, RTC promotes unique advantages over conventional approaches to timber construction, such as, for example, CNC joinery and cutting: through the automated placement of material exactly where it is needed, RTC combines additive and largely waste-free construction with economic assembly procedures, it does not require additional external building reference, and it offers digital control across the entire building process, even when the design and assembly information are highly complex. This paper considers 1) research parameters for the individual components of RTC (such as computational design processes, construction methods and fabrication strategies), and 2) the architectural implications of integrating these components into a systemic, unifying process at the earliest stages of design. Overall, RTC leads to profound changes in the design, performance and expressive language of architecture and thus fosters the creation of architecture that profoundly reinvents its constructive repertoire.
•An overview is given on additive digital fabrication of nonstandard timber structures.•The focus is set on Robotic Timber Construction (RTC), which integrates advanced computational design and automated assembly into a systemic, unifying system.•Of particular concern are experimental setup and research parameters and procedures.•Experimental prototype results are discussed.•The industrial implementation is described.
•The embedded compressive mechanism of mortise-through-tenon connections subjected to cyclic loading was investigated.•A simplified equation for predicting the moment-rotation relationship was ...derived.•The so-validated model was used for extensive parametric analysis by changing different parameters.
This paper investigates the moment-rotation relationship of historic timber structures. In particular, the embedded compressive mechanism of these connections subjected to cyclic loading was investigated and a simplified equation for predicting the moment-rotation relationship was derived. The analytical model was validated by using the results of three 1/3.2-scaled mortise-through-tenon connections, including one intact connection and two connections with a gap between the mortise and through-tenon, tested under quasi-static loading. Then, the so-validated model was used for extensive parametric analysis by changing different parameters, such as the gap between the mortise and through-tenon, friction coefficient and material properties of wood. It is shown that the friction coefficient and elastic modulus perpendicular to grain along the radial direction of wood had an influence on the moment-rotation relationship of the connections, especially for the initial stiffness and ultimate moment of the connections, and both of them increased with a larger friction coefficient and elastic modulus. However, with the increment of the gap between the mortise and through-tenon, the initial stiffness and ultimate moment decreased gradually.
Based on the Modal Stability Procedure (MSP), this paper investigates numerical variability of vibration frequencies of novel adhesive free engineered wood products (AFEWPs), namely adhesive free ...laminated timber beams (AFLB) and adhesive free cross-laminated timber panels (AFCLT), assembled through thermo-mechanically compressed wood dowels. Structures are modelled by finite element method with twenty-node hexahedral solid elements. Several new variants of MSP formulation for the twenty-node solid element have been developed, and the most suitable one using an efficient diagonal mass matrix was selected for the study. Statistical characteristics of the frequencies obtained from the MSP formulation are compared with those obtained from a direct Monte Carlo Simulation. Comparison of computational cost between the MSP formulation and the direct Monte Carlo Simulation is also presented, showing the efficiency of the MSP formulation.
The use of timber allows reducing the environmental impact in the construction sector. However, as the demand for construction timber rises, the pressure on the world’s forest is increasing too. To ...maintain an adequate supply of timber from sustainable forests in the coming decades, the building industry must adopt practices that reduce the impact on forestry. Reuse is one of the principles of Circular Economy (CE). Among the technical challenges of reuse are the variability and the short size of the stock of elements coming either from demolition or from new construction, such as cut-offs and temporary scaffolding. This work presents a study for the design of structural configurations with short and non-regular sized elements that would normally be considered waste. The configurations are based on the principle of structural reciprocity and are generated by an optimization algorithm that allows minimizing the material waste and maximizing the stock elements use. A computational strategy based on the SPEA-II multi-objective method is employed for the investigation of optimal trade-offs between competing objective functions, such as structural lightness and optimal use of stock inventory. The goal of this work is demonstrating the feasibility of an industrial process, borrowing key elements from the Industry 4.0 paradigm, for a streamlined and economical production of standardized building components using non-standard reclaimed elements.
The maintenance of historic wooden structures requires the assessment of the timber elements that compose them. The accurate knowledge of their mechanical performance is a fundamental aspect to ...guarantee conservation, safety, and usability. In this work, the assessment of the mechanical properties of timber was done by visual and machine strength grading. The visual grading rule developed for new wooden products was applied, as well as that established by the Italian standard for historic load-bearing structures. Machine grading was also performed by simulating the procedures applicable to the dismantled or in situ elements. The strength and stiffness values expected according to the different strength grading procedures were compared with the values obtained from destructive tests. As a result of visual grading, the modulus of elasticity was in line with the provisions of the standardization, while the characteristic strength was lower. With machine grading the yields were lower, but the characteristic strength values of the classes were respected, especially if combined with a visual inspection rejecting decayed or damaged pieces. The modulus of elasticity, however, was higher than that of the class, thus being underestimated.
•Prediction of the mechanical properties of historic load-bearing wooden structures is crucial for their conservation.•Visual and machine strength grading were applied on dismantled timber and verified through destructive tests.•Bending strength was lower than expected by applying the visual grading rules, the modulus of elasticity was in line.•The machine grading led to lower yields, but the characteristic strength of the classes were respected.
•The bending moment, initial stiffness and energy dissipation capacity of joint with gap gradually decrease as increasing the damage degree.•The existence of gap can reduce the ductility of joint and ...aggravate the degree of stiffness degradation of M-T joint at the same rotation.•The empirical degradation formulas related to key cyclic performance parameters are established.•A degraded hysteretic model is proposed to predict hysteretic behavior of a joint with gap.
Gaps are very common in the mortise-tenon (M-T) joints of traditional timber structures, and they significantly reduce the rotational performance of joints. To evaluate the effect of gaps on the rotational behavior of straight M-T joints, we fabricated four 1/3.2-scaled Chinese traditional straight M-T joint specimens using Pinus sylvestris logs, one without a gap and three with different gaps, and subjected them to cyclic loading tests strictly in accordance with the international test standard ISO-16670. The failure modes, strength, initial rotational stiffness, ductility, deformation, and energy dissipation capacity of the joints were investigated. The results indicated that the apparent slippage, the tenon pulled out, and the plastic deformation for the mortise edge were exhibited in the specimens with gaps. The bending moment, initial rotational stiffness, and energy dissipation capacity of the joints with gaps gradually decreased as the damaged degree increased. The ultimate rotation of joints with gaps reached 0.2 rad, indicating a good deformation capacity. Furthermore, the gap can aggravate the degree of stiffness degradation of the M-T joint at the same rotation. Based on the experimental results, the empirical degradation formulas related to key cyclic performance parameters, considering the gap effects, were established. Based on the degradation relationships of the key hysteretic parameters of the joint with gaps, a hysteretic model for a joint with a gap was proposed and validated. Good agreement between the model predictions and experimental results was observed.
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