European Journal of Wood and Wood Products最新文献

Elastic fasteners have been widely adopted in timber sleeper tracks in certain high-demand areas across North American freight network due to their excellent potential to mitigate rail-rollover derailments by resisting steering moment and rotation of rail from the vertical axis through intense elastic force to securely hold-down the rail to the sleeper baseplate. However, these systems have led to at least 13 derailments reported since 2000 because of sleeper baseplate spike fatigue failures. Previous spike-failure investigations established that the loss of friction at the baseplate-sleeper interface caused by the wave-action of rail was the major mechanism that transfers additional loads to the spikes, and results in spike stresses exceeding the endurance limits. Previous studies also demonstrated the positives of plate hold-down load on controlling spike stress levels; with this load being historically applied via spring washers. Although the static performance of such hold-down systems has been evaluated in the literature, the long-term, time dependent behavior has not been quantified previously. This paper quantifies the effects of timber sleeper species, spring washer resiliency, and installation load on stress relaxation of these systems over 1,000 h in the laboratory under constant climate conditions. Experimental data demonstrate the significant impact of installation load magnitude on relaxation performance – load retention of 96% and 67% observed under 11.1 kN (2,500 lbs.) and 66.7 kN (15,000 lbs.) installation load, respectively. However, the insignificant effect of spring resiliency on the relaxation behavior was reflected through a 2% only change in load retention over a four-fold change in resiliency. A 15% increase in load retention was achieved by using Red Oak in place of Mixed Hardwood which established sleeper species as a critical parameter in such applications. An assessment of an extended experimentation period (i.e., 2,450 h) was carried out to better estimate the end point of relaxation. The experiments were conducted in an environmental chamber that does not represent the harsh conditions (i.e., loads, vibrations, temperature, humidity, or moisture) of the revenue-service tracks. However, results from this work can reasonably be useful to guide the selection of appropriate components along with recommended installation loads for hold-down applications to improve the overall safety of timber sleeper tracks that leverage elastic fasteners.

The paper presents a fully Lagrangian mesh-free solver to simulate the dynamic behavior of post-tensioned timber structures. Weakly Compressible Smoothed Particle Hydrodynamics (SPH) is employed to model both the timber and the tendon. An efficient and simple coupling method between the timber and the tendon is proposed by considering the numerical stability. Besides, the same coupling algorithm is used to model the interaction between column and beam elements. Although the column is treated as rigid in the simulations, the coupling algorithm accounts for the initial compression of the column resulting from post-tensioning. For the verification of the code for solids and material nonlinearity of timber, benchmark problems available in the literature are used. Finally, the solver's capability is demonstrated through dynamic analysis of post-tensioned timber structures. The solutions obtained for all the cases are in good agreement with the experimental and theoretical data, which indicates the applicability and accuracy of the solver.

This paper presents the dynamic characteristics of the glued-laminated-timber (glulam) floor within China's tallest timber office building and establishes a Finite Element (FE) model. The veracity of the FE model is substantiated through experimental validation. The investigation delves into the impact of variations in the dimensions of Reinforced Ribbed Wood Beams (RRTB) on floor vibration characteristics and assesses the comfort index. Both Ambient Vibration Test (AVT) and human walking tests were carried out on the specific floor under scrutiny. The results show that the RRTB significantly increase the overall stiffness of the floor, and change the natural frequency and modal vibration shape of the floor. The thickness of the RRTB exerts a more pronounced impact on the dynamic characteristics of the floor in comparison to its width. The static deflection of the floor proves to be the most responsive parameter to alterations in the size of the RRTB, compared to the fundamental frequency and maximum displacement. For high-rise glulam building floors, AVT can be effectively applied to fundamental frequency testing; Even if the fundamental frequency of the floor meets the comfort index, supplementary acceleration and velocity amplitude tests remain imperative.

Not before the year 2016, the European standard system did allow for classifying the durability of treated wood in addition to natural durability of untreated wood species. After its latest revision, EN 350 (2016) allows a durability classification of solid wood and wood-based materials with the help of five durability classes (DC) between ‘very durable’ (DC 1) and ‘non-durable’ (DC 5). However, different test methods, assessment measures, and calculation methods can be used for durability classification. This inevitably leads to different assessments of the biological durability of wood. This study aimed therefore on a comparative durability classification of preservative-treated and chemically modified wood (here: treated with 1,3-dimethylol-4,5-dihydroxyethyleneurea, DMDHEU) using different laboratory and field test methods. Durability classes of the tested timbers differed not only between tested materials, but depended also on the applied test, assessment, and calculation method. In this respect, the use of relative values (x-values), i.e., mass loss (ML) or MOE loss data compared with a non-durable reference material can help to harmonize the classification and make DCs more comparable. The use of relative values can also help to reduce the effect of varying virulence of test fungi, activity of test soil substrates, and the climate-induced hazard of test sites.

Cork planks with Yellow Stain (YS) defect are rejected from cork-stopper factory industries resulting in large economical losses. This defect has been related to 2,4,6—trichloroanisole (TCA), a chemical compound responsible for an off-flavor aroma in wine known as cork taint. The relation between YS and TCA was confirmed by the analyzes carried out in this work. Considering that fungi have the capacity to convert trichlorophenol into TCA, raw cork planks were collected in a factory and the mycobiota was searched using morphological and molecular methods. Eight genera and order of fungi were obtained and statistical analysis revealed that the Trichoderma genus is significantly related to TCA levels critical for industry, in particular the species Trichoderma atrobrunneum, a fungus belonging to Trichoderma harzianum complex. To our knowledge, this is the first report associating T. atrobrunneum to high TCA levels and YS defect of cork.

Bamboo nodes are an important component for increasing the hardness and stability of growth. However, little is known about how bamboo nodes affect resistance to biological control agents for industrial use. This study aims to analyze the durability differences between node and internode structures against subterranean termites. Two bamboo species, Giganthochloa scortechinii and Giganthochloa levis were investigated to determine their resistance against Coptotermes curvignathus in laboratory (no-choice and choice) and above-ground experiments. Samples measuring 25 mm × 25 mm x bamboo thickness and 100 mm × 40 mm x bamboo thickness were taken from the three portions (bottom, middle, and top) and each portion was subdivided into two parts: nodes and internodes. Moisture content is also determined for each portion and part. Overall, G. scortechinii is more resistant to C. curvignathus than G. levis, and the node section has greater resistance compared to the internode. The resistance of both bamboo species tested increases towards the top of the node and the internode. The weight loss decreases towards the top in all tests, while the nodes show less weight loss compared to the internodes. The visual determination value for G. scortechinii is 7.4 to 9.0 (choice) and 7.5 to 9.2 (no-choice), while 6.6 to 7.5 (choice) and 6.5 to 7.4 (no-choice) for G. levis. The high resistance of the nodes compared to the internodes is closely related to the anatomical structure of the individual parts and the position in the stem.

Parinari curatellifolia is the main species used to produce charcoal in Angola. Its chemical, anatomical, and thermal properties were analyzed. The bark is dark grey, rough, and corky, and the wood is brown to yellow-red. Compared to wood, bark fibers presented lower length, lumen, and wall thickness. There is not much difference between height and cell numbers of rays. Sieve tube elements appear solitary or in small groups (2–3 cells), and vessels were of two diameter classes but diffuse-porous. Bark basic density was lower than wood (505 kg.m^− 3vs. 580 kg.m^− 3). The mean chemical composition from bark vs. wood of P. curatellifolia was ash (3.2% vs. 1.6%), total extractives (12.2% vs. 10.0%), total lignin (42.4% vs. 28.4%), and suberin 5.4%. Families identified by GC-MS from DCM extracts were predominated by fatty acids in wood and triterpenoid contents in bark. Bark and wood had higher antioxidant activity in FRAP and DPPH methods. The bark had a monomeric lignin composition richer in guaiacyl-units (25.9% vs. 22.5%) and lower syringyl-units (5.7% vs. 8.5%). Potassium was the most abundant mineral, while the least was cadmium found in wood and bark. Regarding thermal properties, bark presented higher moisture content (9.0% vs. 8.0%), ash (3.33% vs. 1.61%), total volatiles (27.5% vs. 20.7%), lower fixed carbon (69.1% vs. 77.7%) and higher heating value (20.9 MJ/kg vs. 19.1 MJ/kg). According to these characteristics, both biomasses are interesting for developing more value-added products (e.g., charcoal, bio-chemicals with phytochemistry and pharmacology activities) besides burning under the context of biorefineries.

While traditional wood preservatives may impede wood decay, their potential harm to both human health and the environment has led to limitations in their usage. This has spurred recent research to focus on seeking wood preservatives derived from plants, owing to their inherently eco-friendly attributes. Agricultural waste such as corn stover fractions, are not only abundant but also frequently underutilized, making them promising candidates for such endeavors. This study delves into the antifungal properties of extracts derived from thermally degraded corn stalk and corn cob. The selection of optimal raw materials and the identification of the most effective thermal degradation process were determined based on their inhibitory activity against Gloeophyllum trabeum (Pers.: Fr.) Murr. and Trametes versicolor (L. ex Fr.) Quél. Gas chromatography-mass spectrometry (GC-MS) was employed to analyze the composition of corn cob extracts resulting from various thermal degradation processes. The evaluation of decay resistance involved wood decay resistance tests and electron microscope observations. Results indicated that ethanol extracts from corn cobs heat-treated at 220 °C exhibited the strongest antifungal activity, accompanied by the highest extract yield. Additionally, the corn cob extracts also demonstrated inhibitory effects on the growth of Aspergillus niger, Escherichia coli, and Staphylococcus aureus. Chemical analysis revealed significant quantities of vanillin, squalene, and other compounds known for their antifungal or antibacterial activity in the corn cob extracts. Furthermore, wood treated with these extracts exhibited improved decay resistance, surpassing that against G. trabeum compared to T. versicolor. These findings suggest that thermally degraded corn cob extracts can be utilized as environmentally friendly wood preservative.