A review of mechanical behavior of structural laminated bamboo lumber

The transition of the construction sector to sustainable development mostly depends on the environmental friendliness of building materials. This, in turn, calls for the development of new, strong, and sustainable materials that would be a worthy alternative for traditional materials, including wood. Over the past decade, laminated bamboo lumber (LBL) has received much attention from engineers, practitioners, and scientists for its attractive mechanical properties, comparable to and in some cases superior to hard and softwood. Moreover, the sustainability of LBL is characterized by its high carbon sequestration, fast time to harvest, high yield, and low energy consumption for processing. However, the behavior of LBL is not yet fully understood, which in turn affects the low awareness and application of the material by practitioners and engineers around the world. Since LBL has a promising future, this article will contribute to a better understanding of its mechanical properties and a more accurate design, taking into account the influencing factors. This article discusses the mechanical properties of three types of structural LBL, namely beams, columns, and sheathing panels. The previous works of researchers on the mechanical properties of structural LBL were reviewed, and thus the most common failure modes, the causes of the destruction of structural elements, and the factors that affect their behavior were discussed and described. This work will serve as a reference for current practitioners and future researc

DETERMINATION OF DESIGN PARAMETERS OF ASPHALT PAVEMENT BASED ON PG TECHNOLOGY

The design parameters are one of the important factors to ensure the quality of asphalt pavement design. In “Highway Asphalt Pavement Design Specification” (JTGD50-2017), the stander of China, used the asphalt mixture anti-pressure resilience modulus at a single temperature of 20 ℃ as the design metrics. However, asphalt mixture, as a sticky-bullet plastic material, shows different mechanical properties at different temperatures. China is a vast territory, and there are great differences between the high and low temperature value (m and n) of each region. Therefore, it is unreasonable to design asphalt pavement only with the asphalt mixture anti-pressure resilience modulus value at 20 ℃. Studies show that the design parameters using PG technology can improve the high temperature anti-rutting and low temperature cracking performance of asphalt pavement

Structural design and construction of an office building with laminated bamboo lumber

With so many advantages such as environmental friendliness, fast-growing, high strength-to-weight ratio, sustainability, and the capability of being reused or recycled, bamboo structures has gained more and more attention for scientists. This paper shows the feasibility of the design of an office building using laminated bamboo lumbers in compliance with the Chinese standards as GB50009-2012, GB50011-2010, GB50016-2014, and GB 50005-2017. Detailed information about the materials and building were offered. A lot of related construction photos were offered to show the building process. This case is a very good application example for laminated bamboo lumber buildings and has attracted many engineers’ attention in industrial field. Laminated bamboo lumber structures should have a bright future. It should become one main structure form in civil engineering area. However, due to none existing engineered bamboo structures design standard now, engineers have to take reference to standards for timber structures. Setting up the standard system is very important for engineered bamboo structures’ application. Through more and more scientists’ hard working, it might be not a long way to build the code system

Assessing larval fish diversity and conservation needs in the Luzon strait using DNA barcoding

IntroductionAccurate species identification and biodiversity assessment of larval fish are essential for effective management and conservation of fisheries resources, as it allows for the estimation of parent stocks, assessment of future recruitment, and prediction of spawning and nursing grounds. However, traditional morphology-based identification methods have inherent limitations, highlighting the need for accurate and efficient techniques to address these challenges effectively. The Luzon Strait, a crucial channel connecting the South China Sea to Western Pacific Ocean, is renowned for its fish biodiversity. However, our knowledge of the biodiversity status of larval fish species in this region remains insufficient.MethodsHere we employed DNA barcoding to assess larval fish species diversity in the Luzon Strait and adjacent waters. We investigated the species composition, diversity, and geographical distribution of larval fish communities in the region. Moreover, we assessed habitat types, human uses, and IUCN conservation status of each larval fish species.ResultsA total of 385 larval fish individuals were collected from 15 stations, and 354 individuals were successfully barcoded and identified, representing 147 species from 93 genera, 44 families, and 22 orders. The interspecific Kimura 2-parameter (K2P) divergence exhibited a significant increase of approximately 55-fold higher than intraspecific divergence. The phylogenetic neighbor-joining tree confirmed the distinct lineages for each taxonomic level, demonstrating the feasibility of DNA barcoding. We observed notable variations in fish species diversity and community composition among sampling stations. Non-metric multidimensional scaling analysis revealed greater diversity and dissimilarity of larval fish community compositions in the western regions compared to the eastern regions. This pattern corresponded to the grouping based on the path of the Kuroshio current, suggesting its influence on the fish community structure. Additionally, economically valuable species were identified at these stations, highlighting their ecological significance as potential spawning or nursery grounds for larval fish. We also examined the habitat type, human use, and conservation status of each larval fish species, providing comprehensive insights into their ecological significance and conservation needs.DiscussionThe establishment of a local DNA sequences database through DNA barcoding will greatly enhance the accuracy of species identification in environmental DNA (eDNA) metabarcoding applications. Altogether, this study offers valuable information for identifying important spawning and nursing grounds of fish populations, thereby supporting sustainable management and conservation of fisheries resources in this region

Fiber alignment angles effect on the tensile performance of laminated bamboo lumber

For better application of laminated bamboo lumber (LBL) in construction industry, the tensile performance of LBL was studied by conducting tension test on LBL specimens with seven different fiber alignment angles, each alignment angle containing 30 specimens. All the specimens only experienced the elastic stage before brittle failure with four failure types. With increasing alignment angle, the tensile strength, tensile modulus, and ultimate tension strain decreased rapidly from 0° to 30°, while they almost remained constant after the angle of 45°. Hankinson’s formula (n = 1.75) can be used to predict the tensile strength of LBL. An empirical equation was proposed to predict the tensile modulus of LBL. The Poisson’s ratio increased and peaked at 15° before declining. Based on the stress–strain coordinate transformation, the relation between shear properties and the alignment angle of LBL was studied; the calculated shear strength decreased with increasing alignment angle, and an empirical equation was proposed, which could be used to obtain the shear strength of LBL for engineering use

Experimental and numerical study on eccentric compression properties of laminated bamboo columns with a chamfered section

The eccentric compression behavior of laminated bamboo lumber (LBL) columns with a chamfered section was investigated using eccentricity of 30 mm, 60 mm, 90 mm and 120 mm. The effect of eccentricity ratio on the ultimate bearing capacity, ultimate strain and failure mode was analyzed through eccentric compression tests. The failure modes of LBL columns with different eccentricities were basically same, which belonged to brittle tension failure. With the increase in eccentricity ratio, the ultimate bearing capacity and ultimate strain gradually decreased. The cross-section strain of the specimen was linearly distributed along the height direction, which conformed to the plane section assumption. The lateral deflection curves had similar characteristics under different load levels and could be expressed by sine half-wave curves. Based on the Hill failure criterion, a 3D finite element model was developed to calculate the ultimate bearing capacity of LBL columns with different dimensions under eccentric compression. According to the simulation results and test results, a general empirical formula was proposed considering both the influence of slenderness ratio and eccentricity ratio. The reliability of the proposed formula was verified by comparing the calculated results with the results in the existing literature

An Effective Approach for Modelling Time Features for Classifying Bursty Topics on Twitter

Several previous approaches attempted to predict bursty topics on Twitter. Such approaches have usually reported that the time information (e.g. the topic popularity over time) of hashtag topics contribute the most to the prediction of bursty topics. In this paper, we propose a novel approach to use time features to predict bursty topics on Twitter. We model the popularity of topics as density curves described by the density function of a beta distribution with different parameters. We then propose various approaches to predict/classify the bursty topics by estimating the parameters of topics, using estimators such as Gradient Decent or Likelihood Maximization. In our experiments, we show that the estimated parameters of topics have a positive effect on classifying bursty topics. In particular, our estimators when combined together improve the bursty topic classification by 6.9 in terms of micro F1 compared to a baseline classifier using hashtag content features