Abstract

Steaming and heating as pretreatments before log sawing reduce the negative effects of growth strain (GS). The object of this work was to study the reduction of GS in logs of Dipteryx panamensis from a fast-growth plantation using steaming and heating treatments and evaluate the effects on the lumber quality. According to the results, the maximum temperature in the center of the log was approximately 90°C after 24 hours for both treatments. GS decreased after heating and steaming. The average value of GS for three treatments was 2,085.61 microdeformation units (με) before the treatment, decreasing to average value to1,692.14 με after the treatments. This reduction in turn produced a reduction of crook due to sawing measured in logs and semilogs and a decrease in the values and incidence of crook, bow, twist, and split. Similarly, color parameters (L*, a*, and b*) were statistically affected by the treatment, except for parameter L* in sapwood. In general, wood darkening was observed. Lastly, both treatments applied to D. panamensis logs showed few differences in GS, in crook due to sawing measured in logs and semilogs, and in the values and incidence of crook, bow, twist, and split. Therefore, both treatments achieved GS reduction in D. panamensis lumber.

Abstract

Forestry production is one of the fundamental industries of the national economy, and enhancing production efficiency can aid in balancing the contradiction between the economic growth of forestry and forest resource conservation. Therefore, studying the coupling coordination between forestry production efficiency and regional economic development is of great practical significance for obtaining the development philosophy of green and circular economies and implementing supply-side structural reform in forestry. In this study, the forestry production efficiencies and economic development levels of 31 provincial-level administrative regions of China during 2009 to 2018 are estimated using the super efficiency slacks-based measure model and the entropy weight method. Additionally, the coupling coordination and development trends of forestry production efficiencies and regional economic development levels are investigated by means of the coupling coordination model and GM (1,1) model. Research findings suggest that forestry production efficiencies and economic development levels of 31 provincial-level administrative regions in China maintained steadily growing trends during 2009 to 2018; however, there was middle to low-level coupling coordination between regions. Such coupling coordination remains to be improved because it indicated a spatial pattern of high in the east and south and low in the west and north. To conclude, some suggestions for promoting sound and coordinated interactions between forestry production efficiency and regional economic development are offered.

Abstract

Rapid Ohia Death is a major concern for the viability of ohia (Metrosideros polymorpha) in Hawaii and has led to restrictions on log movement. The potential for using disodium octaborate tetrahydrate (DOT) and didecyl dimethyl ammonium chloride (DDAC) dip diffusion treatments to control the two causal fungi (Ceratocystis lukuohia and Ceratocystis huliohia) was investigated. A 10 percent boric acid equivalent dip diffusion treatment killed the pathogens in 0.5-cm-thick disks obtained from 4.0- to 5.0-cm-diameter limbs of naturally colonized trees. DOT tended to diffuse more consistently in 50- to 60-cm-long bolts of small (4.0 to 9.0 cm) and large (9.1 to 17.0 cm) diameter healthy ohia compared with those bolts naturally infected by C. lukuohia. Diffusion periods longer than 6 weeks resulted in deeper penetration. Immersion (24 h) of logs (1.3 m long; 9 to 17 cm diameter) from C. lukuohia artificially inoculated trees in two forest locations in a 15 percent DOT/1 percent DDAC solution and storage for 10 weeks before evaluation resulted in incomplete elimination of the pathogen and lower boron concentrations in the inner sapwood than outer. Further investigations are needed to explore using either higher boron concentrations or longer diffusion periods to deliver fungicidal concentrations of boron deeper within the wood matrix.

Abstract

The defect rate of initially produced block bamboo (Bambusoideae) parts is >20 percent. Sorting out these defective parts manually is a highly time-consuming and tedious process. An intelligent sorting system was developed based on machine vision using a Radial Basis Function (RBF) neural network learning algorithm in this study. First, a high-speed charge-coupled device camera was used to obtain a series of images of perfect and defective block bamboo parts. Next, the RBF neural-network learning algorithm was applied to obtain defect characteristics and to locate defective parts moving forward on a conveyor belt. An array of air jets was designed to force defective parts off the belt. Experimental results showed that the average defective part removal rate of the proposed system was 91.7 percent.

Abstract

A need exists to develop improved test methods for evaluating potential wood preservatives in aboveground outdoor exposure. Our studies have shown that the three-component lap joint specified in AWPA Standard E27-15 represents an improved design for aboveground testing. One option for evaluating the extent of decay with this method relies on visual assessment. However, based on my observations in field tests, this assessment method does not provide an accurate measurement of the extent of wood biodeterioration in the early stages of decay. A second method of evaluation provided in this standard (in figure 4 of the standard) uses bending stiffness and dynamic modulus of elasticity (MOE) as alternate methods for determining the extent of decay, and this option was chosen to follow the progress of biodeterioration in this study. It was found that both of these methods provided an accurate assessment of decay in the early stages of biodeterioration that was superior to visual assessment.

In an attempt to accelerate the rate of wood decay, some of the test units were treated with nitrogen-rich casein, and this resulted in a greater than twofold increase in the decay rate compared with the untreated controls. Another group of samples were treated with thiamin, but this resulted in only a slight increase in decay rate, whereas a combined treatment with both casein and vitamins resulted in a further increase in the decay rate beyond that of casein treated samples. Based on the results from this study, it is concluded that pretreatment of wood samples with thiamin has the potential for accelerating wood decay in aboveground test samples. Furthermore, the use of bending stiffness and dynamic MOE to measure the extent of wood decay was found to be superior to mass loss. Additional studies are needed to determine whether this concept could be useful in accelerating development of new wood preservatives.

Abstract

The effect of pretreatment with either boron or glycerol followed by thermal modification on the durability of Douglas-fir heartwood was evaluated in an American Wood Protection Association ground proximity test in Hilo, Hawaii. Non–thermally modified samples were generally more heavily decayed than any of the modified woods, but there was no consistent effect of different thermal modification conditions on decay resistance. Thermally modified woods tended to perform better than untreated timbers but not as well as copper azole–treated Douglas-fir heartwood lumber in test at the same site. The results are discussed in relation to how the extreme site conditions might have made it difficult for thermally modified materials to perform.

Abstract

For this study, spruce–pine–fir (Picea–Pinus–Abies [SPF]) specification material, oriented strand board (OSB), and domestic twisted nails that were driven vertically and perpendicular-to-grain were selected. Referring to GB/T 13942.1-2009, nailed joints specimens were exposed both to white rot fungus and brown rot fungus for 1 month to 6 months. The monotonous loading test was applied to the specimens based on ASTM D1761-88. The holding power of the nails and weight loss of both OSB and SPF were investigated. Theoretical maximum load of the nailed joints was calculated according to Eurocode5. Results illustrated that the load, stiffness, and energy consumption of the nailed joints showed significant linear decline with the decay time. A linear decline of the ductility coefficient was not obvious, and there was no obvious difference between white rot fungus and brown rot fungus. Effect of decay on the OSB was much greater than the impact on the SPF. The decay grade of the nailed joints was established according to the linear relationship between weight loss and maximum load. Based on Eurocode5, the study calculated the maximum load of the nailed joints and introduced the correction coefficient γ to better predict the maximum load.

Abstract

Full-culm bamboo has been used for millennia in construction. Specific connections are normally required to suit its unique morphology and nonuniform structure. Presently, the use of full-culm bamboo is limited in the construction industry as a result of a lack of information and test standards about the use and evaluation of full-culm connections. This study aims to further explore this area by investigating the failure modes in bamboo bolt connections in uniaxial tension by considering fiber direction in finite element analysis. Three types of bolt configurations of varying permutations, namely, single, dual, and orthogonal, were investigated. An orthotropic material was used as a constitutive model in finite element formulation to capture the inhomogeneity prevailing in bamboo culm. From the strain-field analysis of a hollow-inhomogeneous model representing bamboo, shear-out failure was dominant, as a localized area equivalent to the bolt diameter was affected due to high material orthotropy with high axial strength but weak radial and tangential strength. Bearing failure is assumed to precede shear-out failure at the bolt–bamboo contact interface, as the embedding strength was affected by localized strain concentration. The strain distribution in various bolt arrangements was found to vary between bolted connections of inhomogeneous-hollow geometry of bamboo and the ones of inhomogeneous-solid geometry representing timber. The observation in this study highlights the need for alternative design criteria to specifically assess the damage mechanism in bamboo connections.

Abstract

The rising interest in wooden multistory buildings (WMSB) has led to multiple studies investigating how construction professionals perceive different structural frame materials. These investigations, however, exclude viewpoints from public employees (i.e., civil servants), who are central to driving the implementation of WMSB. This study is part of a broader inquiry to examine perceptions from Finnish civil servants who are responsible for municipal land-use planning and development. To this end, a questionnaire applying the theory of planned behavior was designed. Civil servants were asked to evaluate how strongly they believe WMSB possess 16 attributes in comparison to concrete multistory buildings (CMSB). The attributes constitute statements concerning various economic, social, and environmental impacts of multistory buildings, as well as technical properties. Responses (N = 273) indicate that WMSB are believed to possess positive environmental attributes and to support economic development. In contrast, CMSB are regarded to have lower construction and maintenance cost and to be less susceptible to fire. Furthermore, exogenous factors, like demographics, previous experience, and social environments, were significantly correlated to respondents' beliefs. Especially prominent was the relationship between profession and beliefs about technical and environmental attributes. Future research should focus on determining whether the set of attributes assessed in this study are relevant to the implementation of multistory building projects within Finnish municipalities.

Abstract

In order to better understand the differences in orthotropic viscoelastic properties of Chinese fir (Cunninghamia lanceolata) in frozen and non-frozen states, the storage modulus (E′) and loss modulus (E″) of the longitudinal, radial, and tangential specimens were investigated under water-saturated conditions with temperatures ranging from −120°C (or 30°C) to 280°C. Results revealed that the order of magnitude in E′ for each orientation was consistent for temperatures below 0°C, while the anisotropy in E′ was reduced due to the enhancement effect of ice. Frequency-dependent γ-relaxation was observed at approximately −96°C for all orthotropic directions. A sharp discontinuity in E′ occurred at approximately 0°C for each specimen, together with the corresponding sharp peak in the E″ spectrum. Furthermore, the frozen free water had an effect on the orthotropic viscoelastic behavior in the water-saturated specimens within the range of −120°C to 280°C. Specimens with a frozen history leveled off at the initial temperature ramping phase for each orientation, while a frozen history reduced the decline in stiffness of the wood specimens. Similar to the variations in E′, the dramatic loss of water increased the complexity of the E″ values. The loss of free water also had a pronounced effect on the viscoelastic properties during the temperature ramping process. Thus, in the wood industry, it necessary to consider the variations in the orthotropic viscoelastic performance of specimens under water-saturated conditions during the water loss process.

Abstract

Laminated bamboo furniture is high in ecological value and low in overall cost, exhibiting broad prospects for industrial development. Studies have been conducted on human visual cognition of wood and textiles but not of glue-laminated bamboo materials. This study employed a subjective questionnaire and eye-tracking technology to explore the effect of the laminated bamboo furniture surface characteristics on human visual cognition. The results indicate that the fixation count and total fixation duration of caramelized glue-laminated bamboo materials were higher than those of natural colors; participants tend to pay more attention to the colors of glue-laminated bamboo surfaces than to their textures. Although no significant differences have been identified between the overall evaluations attributed to various types of glue-laminated bamboo, within specific cognitive dimensions, participants evaluate natural and caramelized colors differently. Natural glue-laminated bamboo furniture is associated with a greater sense of usability and cultural design in participants' visual cognition, whereas caramelized glue-laminated bamboo furniture is associated with a greater sense of beauty. Total fixation duration and fixation count for the surface characteristics of laminated bamboo furniture are positively correlated with participants' subjective visual appraisals. The longer it takes for participants to notice a laminated bamboo furniture product and the more frequently they fix their gaze on it, the more favorable their evaluation of the product is. These research findings provide a reference to designers for the design of laminated bamboo furniture.