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• The mechanical properties of the bolt connection of a newly engineered bamboo – LFB were investigated by experiment study and finite element simulation. • Based on Johansen's yield theory, a theoretical calculation equation for the bolted LFB connection's bearing capacity was proposed. • A theoretical calculation equation for the load-slip relation of the bolted LFB connection was proposed. This paper investigated the mechanical performance of the bolted steel-laminated-flattened-bamboo (LFB)-steel connection under compression parallel to grain using experimental and finite element (FEM) methods, focusing on the bolt diameter and the thickness of the main member. Results showed that increasing the bolt diameter significantly enhanced the connection's bearing capacity and initial stiffness. However, the strength of the connection no longer increased when the main member's thickness exceeded 75 mm. Two ductile failure types were identified for the bolted steel-LFB-steel connection: bearing failure of the main member beneath the bolt and bending yield failure of the bolt. Based on Johansen's yield theory, a theoretical calculation equation for the connection's bearing capacity was proposed considering the transition of connection behaviour and the development of friction force between the main member and steel plate surface. A theoretical calculation equation for the load-slip curve of the bolted connection was proposed, assuming the strain of the LFB material beneath the bolt was linearly distributed, which could predict the behaviour in the elastic and yielding stage of the load-slip curve. Finally, another multilinear model for the load-slip curve was proposed based on the proposed theoretical equation and test results, which could better demonstrate the strengthening stage of the load-slip behaviour. [ABSTRACT FROM AUTHOR]

The chloride-induced reinforcement steel corrosion usually causes premature failure of performance in reinforced concrete structures subjected to chloride environment. However, conventional prescriptive design methods or fully probabilistic methods cannot ensure an explicit performance in design stage. The main objective of this study is to develop a performance-based service life design method, by which concrete structures such as bridges can be designed according to a predefined performance level to satisfy the target service life, reliability and deterioration level. The mechanism of chloride-induced reinforcement steel corrosion initiation was analyzed to deduce a time-varying limit state function, and the corresponding stochastic model was developed considering the effects of random factors. Through first-order reliability method, a partial factor formula was deduced to realize performance verification in performance-based design process. Finally, a case study of a concrete bridge deck exposed to marine environment was presented and the sensitivity analysis of steel corrosion was carried out. The proposed performance-based design method can rationally deal with the uncertainties of random parameters and ensure the predefined target performance to be satisfied during design process instead of predicting performance after design. [ABSTRACT FROM AUTHOR]

• Dynamic response of asphalt mixture was monitored in SGC test by SmartRock sensors. • Understanding of compaction characteristics between PAC, SMA and AC mixtures. • Effect of nominal maximum aggregate size on compaction of mixture is investigated. Compaction degree is an essential parameter to characterize the construction quality and performance of asphalt pavement. Under the same compaction conditions, asphalt mixtures with different aggregate sizes and gradation may exhibit different compaction characteristics. Accordingly, this paper aims to study the compaction characteristics of asphalt mixture at the meso -scale through particle response of the mixture by using SmartRock sensor. Firstly, a laboratory test scheme of the asphalt mixture is designed and the SmartRock sensors are used to obtain the internal stress of the mixture during compaction. By comparing the particle stress with the height of the specimen, it is inferred that the stress state of the particles can reflect the compactness of the compacted material, and the change rate of compaction degree in logarithmic coordinates is proposed to characterize the compaction performance of the asphalt mixture. Furthermore, the quantitative analysis is comprehensively conducted related to the different nominal maximum aggregate size (NMAS), locations and gradation types. The results reveal that the asphalt mixture with larger NMAS has a better compactibility in terms of forming a stable skeleton structure, and the mixture in the middle of specimen can be compacted more easily than that in the top and bottom area of specimen. It can be aslo found that the gradation type affects the compaction performance through the probability of coarse aggregates interlocking with each other. The open-graded mixture (i.e, PAC-16) is relatively faster to achieve the target compaction degree than gap-graded and dense-graded mixtures (i.e, SMA-16 and AC-16, respectively). Although the asphalt mixture with larger NMAS and coarser gradation can reach a certain compaction degree with a rapid speed, it doesn't mean the mixture can achieve higher compaction degree finally under the action of subsequent compaction work. The test result shows that the asphalt mixture with coarser aggreages is relatively difficult to compact with lower final compactness. The experimental research sheds substantial light on the internal relationships between the response of the particles and compaction charateristics of asphalt mixture at meso -scale. [ABSTRACT FROM AUTHOR]

• Dynamic response of pavement and vibrating drum were monitored by SR and HCF sensors. • High frequency signals were used to analyze the dynamic response in vibrating compaction. • Linear relation was established between acceleration of vibrating drum and compactness. • Understanding of compaction mechanism in terms of acceleration and stress for particles. Although compaction is one of the most critical steps during the construction of asphalt pavements, effective real-time technologies to detect the compactness of the asphalt mixture non-destructively are still rare. Currently, most methodologies in practice are experience-based, and few studies have provided insight into the particle interaction characteristics and quantitative response during the vibration compaction of asphalt pavements. Accordingly, both field and laboratory tests are conducted in this study to investigate the response of an asphalt mixture quantitatively under a vibrating compaction load at the meso-scale. First, a field test program is designed, and sensors (e.g., SmartRock and acceleration sensors) are used to measure the dynamic response of an asphalt pavement and the vibrating drum during vibrating compaction. The quantitative analysis reveals that the first three rolling impacts exert a significant and dominant compact effect on the asphalt mixture. Subsequently, a linear relationship between the acceleration of the vibrating drum and the vertical stress in the asphalt pavement is demonstrated. Furthermore, the SmartRock sensor is also employed in the laboratory test to detect the internal dynamic response under gyratory compaction, and the relationship between the compaction degree and the vertical stress in the asphalt mixture is established. Finally, three assessment methods for asphalt mixture compactness are proposed as characterization of the compactness by the acceleration of a vibrating drum, intermediate variables such as the stress of the mixture under a gyratory compaction, or acceleration and stress of the pavement. Comparison of the results illustrates that the dynamic response inside the mixture during the compaction can directly reflect the compaction degree of the asphalt mixture, and the compaction degree and the peak acceleration of the vibrating drum exhibit a strong linear correlation during the vibration rolling process. [ABSTRACT FROM AUTHOR]

• Pyrolysis products' distribution of bitumen and its four components were studied. • From saturates, aromatics, resins to asphaltenes, their thermal stability gradually increases. • The pyrolysis products of resins resemble that of asphaltenes. To further understand thermal properties of bitumen, saturates, aromatics, resins and asphaltenes (SARA) were separated from two bitumen firstly. Then the thermal stability and activation energy of SARA components during combustion were investigated via thermo gravimetric-differential scanning calorimetry (TG-DSC). Additionally, the composition and distribution of pyrolysis products of four components in pyrolysis process were evaluated by pyrolysis gas chromatograph coupled with mass spectrometry (PY-GC–MS). The results indicate that asphaltenes have the best thermal stability, followed by resins, aromatics and saturates, and the activation energy of light components is lower than that of heavy components. Two bitumen are different in distribution of pyrolysis products, which may be caused by different sources and production processes. But they have similar composition, the pyrolysis products of heavy components are more complex than those of light components. The combustion behavior and pyrolysis products of bitumen are better understood from a new perspective of its components. [ABSTRACT FROM AUTHOR]

• A lightweight and efficient BLS-based crack detection model is proposed to automatically classify and identify crack images. • The bottleneck structure of MobileNetV3 is introduced as the convolution module of the proposed broad learning system for feature extraction. • By training and validating with public and realistic crack image datasets, the proposed model achieves fast and efficient incremental learning as training samples increase. • The sliding window algorithm is introduced to efficiently recognize and locate cracks in the large-size image. Concrete surface crack detection is an important means to ensure infrastructure security, including bridges and tunnels. In recent years, computer vision has been widely adopted for concrete surface crack detection, and the intelligent crack detection method based on computer vision has achieved good results with the breakthrough of the deep learning algorithm. However, there are also some challenges, such as complex architecture, high computing burden, and time-consuming training. In this paper, a lightweight broad learning system detection method called MobileNetV3-BLS is proposed. First, the inverted residual structure with the linear bottleneck of MobileNetV3 is introduced as the convolution module of the proposed broad learning system for feature extraction. Then the extracted features are employed to randomly generate both mapping and enhancement nodes in a broad learning system, which are used to train the crack detection model. The proposed MobileNetV3-BLS can improve crack detection accuracy and training speed compared with other classical deep learning networks. On the other hand, the proposed method is a dynamic network of which the weights can be updated quickly to achieve incremental learning by adding new nodes and samples. [ABSTRACT FROM AUTHOR]

• A new type of engineered bamboo product (LFBL) was presented to improve the utilization rate of bamboo resources. • Mechanical properties of bolted steel connections in LFBL under cyclic loading were studied by experiments. • Failure modes of bolted steel connections in LFBL under cyclic compression parallel and perpendicular to the grain. • Several analytical models for the prediction of cyclic load-deformation response. In beam-column systems, bolted steel connections in laminated composite structures are being increasingly employed for their superior mechanical performance. Laminated flattened-bamboo lumber (LFBL) is a newly engineered bamboo product and a promising structural material since its production process could achieve the high-efficiency utilization of bamboo resources. This research investigated the load–displacement behavior of bolted steel connections of LFBL under cyclic compression. A total of 30 specimens in 6 groups were tested to determine the hysteresis curves, the effects of the bolt number, and failure modes under cyclic compression parallel and perpendicular to the grain. The test results illustrated that splitting and crushing failure were the main failure modes. With the increase in bolt quantity, the maximum load and initial stiffness of all specimens were significantly increased, while the ductility slightly decreased. The theoretical models of the skeleton curves and the reloading and unloading curves under cyclic loads were put forward, and the proposed equations were able to predict the entire cyclic load–displacement response. This study is aimed at offering guidelines for LFBL applications in future construction engineering. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dowel-bearing characteristics of laminated flattened-bamboo lumber (LFBL) were tested. • The effecte of diameter, length, width, thickness and four kinds of arrangement method of flattened-bamboo panels was considered. • The applicability of different prediction formulas was evaluated, and the new formulas were proposed for predicting the dowel-bearing strength of LFBL. This paper examines the dowel-bearing strength of laminated flattened-bamboo lumber (LFBL) perpendicular to grain under the influence of the flattened-bamboo arrangement method, the bolt diameter, and specimen size in accordance with ASTM D5764-97a. There were 360 specimens tested in total. As a result of the test results, it was demonstrated that the arrangement method of flattened bamboo panels significantly affected the dowel-bearing strength of the LFBL. In two of the groups (bolt direction perpendicular to the grain), the dowel-bearing strength was significantly greater than in the other two groups (bolt direction parallel to the grain). According to the arrangement method of the bamboo panels, the size effect on dowel-bearing strength varies. However, the dowel-bearing strength always decreased as the diameter of the bolt increased. Four typical failure modes and load–displacement curves were classified. Results of the tests were compared with those calculated by predicting formulas from other studies, allowing empirical equations for predicting the dowel-bearing strength of LFBL specimens to be developed. [ABSTRACT FROM AUTHOR]

The adoption of bamboo poles in construction can support the reduction of carbon dioxide emissions generated by the manufacture of conventional structural elements produced from unsustainable industrialised materials. This research focuses on the study of the nonlinear softening behaviour and failure mechanism of bamboo poles in bending through a series of experimental tests on Moso (Phyllostachys pubescens) bamboo and Finite Element simulations supported by digitisation techniques. The results indicate that this nonlinear behaviour is caused by the incremental development of cracks at the locations where the circumferential tensile capacity of bamboo is exceeded leading to the eventual failure of the pole. Also, the simulations in this study suggest that reinforcing bamboo poles with pretensioned stainless steel bands is ineffective in counteracting the development of significant circumferential tensile stresses and the associated longitudinal cracks. More generally, this work highlights the challenges and limitations of applying traditional methods of structural testing and design for manufactured components to a highly variable natural structural element and speculates whether modern digital technologies can be adopted to manage more effectively the effects of this inherent variability. [ABSTRACT FROM AUTHOR]

This study investigated the interfacial bond performances between ordinary Portland cement concrete (OPCC) and self-compacting geopolymer concrete (SCGC). The studied factors include nano-SiO 2 , repair material type, curing time, casting direction, and interface pretreatment method. The interfacial bond performances were assessed by Bi-surface shear and drying shrinkage tests. The evolutions in elemental compositions, hydration products, and microstructure in the matrix and interface were verified by BSE/EDS, XRD, and FTIR tests, respectively. ANOVA analysis was conducted to quantitatively analyze the influences of each factor from a statistical approach. The results demonstrated that the bond strength of SCGC increased by 24.5% to 31.7% compared to conventional OPCC. Meanwhile, geopolymers exhibited more compact microstructures but higher drying shrinkage (ε sh,u =891 µε). While nanofillers significantly amplified the cracking potential of geopolymers, which was attributed to the higher early-stage autogenous shrinkage instead of drying shrinkage. The SCGC showed a high enrichment degree of calcium at the interface, indicating that more calcium-rich products were formed. In contrast, the use of nano-SiO 2 in SCGC caused the enrichment of Na, Al, and Si at the interfacial regions, which provided extra nucleation sites for the polymerization of (C, N)-A-S-H gels. The nano-SiO 2 enhanced the intensity of the hydroxide ion and Si-O-T band and promoted the formation of (C, N)-A-S-H gels. The ANOVA analysis proved that the repair material, nano-SiO 2 , and interface treatment were significant factors to affect the interfacial bond strength. In addition, geopolymer-based repair materials were less sensitive to the casting direction, which differed from the conventional self-compacting OPCC. [Display omitted] • Geopolymer concrete at the same strength grade has 25-30% higher bond strength than conventional OPCC. • Nanofillers amplified the cracking potential of geopolymers due to higher early-stage autogenous shrinkage. • nano-SiO 2 in SCGC caused the enrichment of Na, Al, and Si at the interfacial regions. • geopolymer-based repair materials were less sensitive to the casting direction. [ABSTRACT FROM AUTHOR]

• Concrete compressive strength grows at 1.2% of bamboo sticks and decreases at 2.4% • Concrete elastic modulus grows at 1.2% of bamboo sticks and decreases at 2.4% • The lower the bamboo stick diameter the higher compressive strength. • Increased length of bamboo sticks increases concrete stiffness. • High bamboo sticks volume ratio decreases bonding strength of concrete aggregates. Over the past decade, bamboo has received much attention due to its sustainability and strength. The advantages of bamboo over other natural fibres include its abundant existence, high yield, and the ability to quickly reach a maximum height and strength in 3–8 years. Bamboo can be used as an independent structural material and concrete reinforcement in the forms of bamboo culms, bamboo splints, and bamboo composite bars for low-rise and low-cost buildings. In this study, bamboo sticks were adopted as reinforcement for concrete cubes. The following influencing factors were considered: bamboo stick volume ratios of 0.6 %, 1.2 %, and 2.4 %, bamboo stick diameters of 1 mm, 1.5 mm, and 2 mm, and bamboo stick aspect ratios of 10, 20, and 30. The test result shows that with the addition of 0.6 % of sticks, the BSRC compressive strength rose by 3.24 and 17.33 % for length-to-diameter ratios 20 and 30, respectively. The compressive strength of specimens was enhanced by adding 1.2 % and 2.4 % bamboo sticks with a length-to-diameter ratio of 10 by 21.38 and 20.94 %, respectively. The obtained results were compared with the mechanical properties of conventional concrete cubes. Currently, river sand and fresh water are the most often used materials in manufacturing concrete. The widespread use of river sand and freshwater has resulted in major environmental issues. Because many places of the world lack appropriate supplies of fresh water, overuse of this resource is not advised. As a result, saltwater and sea sand were used to create both bamboo stick reinforced concrete and plain concrete specimens. Lastly, a model of strength and stress–strain was proposed. [ABSTRACT FROM AUTHOR]

• Three layers of bituminous films at different stages of aging and rejuvenation were obtained by staged extraction method. • The selective absorption of bitumen by BOF is significantly higher than that by natural aggregate. The selective absorption of bitumen by aggregates exhibits a time-dependent effect. • The selective absorption of bitumen by aggregates is most significant during the short-term aging process. • Bitumen delamination occurs due to selective absorption of bitumen by aggregates, resulting in little effect on the road performance of bituminous mixtures. The selective absorption of bitumen by BOF has been systematically studied by previous scholars. However, there is still a lack of research on the selective absorption of bitumen by BOF at different aging stages. Hence, this issue deserves systematic investigation. Also in order to understand how to improve the pavement performance of BOF based bituminous pavement, this study is designed to explore the selective absorption behavior of BOF to bitumen components at different aging and rejuvenation stages. The protocols of short-term aging, PAV aging, and second PAV aging were subjected to specimens to simulate different service time of bituminous pavement. The complex modulus, phase angle, chemical composition and four component contents of different stages and layers of bituminous samples were analyzed by dynamic shear rheometer and Fourier infrared spectroscopy and thin layer chromatography with flame ionization detection. The road performance of the bituminous mixtures at different stages was also investigated. The results show that the BOF and natural aggregates all reveal selective absorption of bitumen, while BOF demonstrates a more significant effect for bitumen than natural aggregates. The selective absorption of bitumen by aggregates exhibits a time-dependent effect, resulting in the strongest selective absorption at the stage of short-term aging. Bitumen layers display multi layered system due to selective absorption of bitumen by aggregates, while effects insignificantly on the road performance of bituminous mixtures. The decrease in the ability of adhesion for bitumen due to aging is the key factor affecting performance of bituminous mixtures. [ABSTRACT FROM AUTHOR]

• The source position and compression direction were considered for large-scale specimens. • Comparisons among the test results considering different influencing factors were carried out. • Analytical models were proposed for PBSL under local compression. Large-scale parallel bamboo strand lumber (PBSL) structural elements are often subjected to local compression especially in beam-to-column connections as well as in beam-to-beam connections. The current paper presents an experimental investigation on the local compression behaviour of PBSL. 20 specimens were collected from different parts of a PBSL block under radial and tangential compression loading. Load-displacement curves of all specimens were recorded and observed failure patterns were carefully investigated to understand underlying mechanics. Tangentially loaded specimens predominantly failed due to debonding of fibres triggered by deformations perpendicular to the grain. On the other hand, radially loaded specimens showed a combined failure caused by debonding in perpendicular to the grain direction as well as tensile failure of bamboo fibres in the longitudinal direction. Key design parameters such as elastic modulus, stiffness, ultimate strength and Poisson's ratio for all specimens were computed and compared against end vs middle specimens as well as radial vs tangential specimens. Radially loaded specimens showed higher load carrying capacity due to better bonding, whilst the specimens collected from the middle part of the PBSL block were relatively more ductile than the others. Analytical models for load–displacement repose as well as for stress–strain behaviour were proposed for the considered specimens. Ramberg-Osgood based stress–strain model showed good agreement with test results. [ABSTRACT FROM AUTHOR]

• Bimodulus model to determine the strain and stress distribution of bamboo poles in bending. • Analytical model based on experimental testing of small clear bamboo samples. • Model validation based on full-scale experimental four-point bending tests. • Proposed model predicts the cross-sectional elastic strain and stress distributions. The building industry is currently under pressure to transit from non-renewable materials with high embodied energy towards natural and sustainable options. Bamboo poles are some of the most promising renewable structural elements, but their formal utilisation in construction requires the development of appropriate analytical models and new design tools to address their challenging natural and organic nature. Considering the composite nature of bamboo poles and the properties of their high-strength sclerenchyma fibres and parenchyma matrix, this paper presents the formulation of an analytical bimodulus model to determine the cross-sectional strain and stress distribution in bamboo poles in bending. This model was validated through full-scale experimental four-point bending tests on Moso (Phyllostachys pubescens) bamboo poles suggesting a constant tensile elastic modulus of fibres for this species. [ABSTRACT FROM AUTHOR]

• Bonding behavior of two asphalts with five aggregates was studied. • Different indexes were used to evaluate the bonding strength of asphalt-aggregate system. • BOF slags show higher adhesive strength to asphalt than andesite and limestone. • Different factors affecting the bonging behavior of asphalt-aggregate system were evaluated. The bonding behavior of asphalt-BOF (Basic Oxygen Furnace slag) system is of great significance for ensuring durable pavement performance. In this research, moisture stripping rate test and moisture stability test were used to measure the adhesive strength of asphalt with BOF compared with two mineral aggregates. Combined surface free energy with SARA fractions, the bonding behavior of asphalt and its components with different aggregates were assessed by means of adhesion work. Additionally, the effects of physicochemical properties of BOF, the rheological properties of asphalt components and experimental factors on the weights of the affecting factors were studied via grey correlation analysis method (GCAM). The results indicate that the adhesion strength of asphalt with BOF slag is superior to andesite and limestone. Surface free energy showed that the rheological behavior of aromatics is closest to its mother asphalt. By means of GCAM, it can be concluded that alkalinity and surface texture of BOF slag have a critical contribution to the bonding strength of asphalt-BOF slag system. Dynamic water pressure can aggravate asphalt stripping off and has an important effect on the adhesive strength. [ABSTRACT FROM AUTHOR]