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Renal injury, a prevalent clinical outcome with multifactorial etiology, imposes a substantial burden on society. Currently, there remains a lack of effective management and treatments. Extensive research has emphasized the diverse biological effects of natural polysaccharides, which exhibit promising potential for mitigating renal damage. This review commences with the pathogenesis of four common renal diseases and the shared mechanisms underlying renal injury. The renoprotective roles of polysaccharides in vivo and in vitro are summarized in the following five aspects: anti-oxidative stress effects, anti-apoptotic effects, anti-inflammatory effects, anti-fibrotic effects, and gut modulatory effects. Furthermore, we explore the structure-activity relationship and bioavailability of polysaccharides in relation to renal injury, as well as investigate their utility as biomaterials for alleviating renal injury. The clinical experiments of polysaccharides applied to patients with chronic kidney disease are also reviewed. Broadly, this review provides a comprehensive perspective on the research direction of natural polysaccharides in the context of renal injury, with the primary aim to serve as a reference for the clinical development of polysaccharides as pharmaceuticals and prebiotics for the treatment of kidney diseases.

Under the background of marine strategy and clean energy strategy, China has carried out large-scale construction around marine ranching and offshore wind farms and made great achievements. However, the problems such as high project cost, the fragmentation of marine habitats and maritime conflict are becoming increasingly prominent, which have led to the test and exploration of integrated development of offshore wind farms and marine ranching at home and abroad. Based on the analysis of relevant research and test work at home and abroad, suggestions are put forward for the current situation of integrated development of offshore wind and animal husbandry, as well as the difficulties and challenges in economic and policy feasibility, site selection and planning, fish species selection, supporting equipment development, ecological impact assessment (noise, electromagnetic field, base interference, heavy metal migration, etc.), etc.

Wooden cantilever covered bridges are known for their marvelous shapes and manufacturing technique. Many wooden cantilever covered bridges were constructed during Ming and Qing Dynasties in Anhua province, China, due to the “Tea-Horse Trade” policy. The excellent performance of wooden materials and exquisite building techniques have kept these wooden bridges well-preserved and worthy of investigation. This paper conducted a comprehensive review of wooden cantilever covered bridges in Anhua, especially for the eight bridges listed as historical and cultural heritage protected at the provincial or the national level. The discussions covered the historical background of the bridges, their locations and dimensions, and the details of their structures including the cantilever systems, corridors, and roofs. Moreover, the cultural background was introduced to better understand the meaning of the decorations carved on the bridges and the logic of location selections.

Background: Trichoderma species are rich source of bioactive secondary metabolites. In the past decades, a series of secondary metabolites were reported from different Trichoderma fungi, among which terpenoids possessing versatile structural diversities and extensive pharmacological activities are one of the particularly important categories. Aim of Review: The review aims to summarize the terpenoids isolated from Trichoderma species regarding their structural diversities, biological activities, and promising biosynthetic potentials. Key Scientific Concepts of Review: So far, a total of 253 terpenoids, including 202 sesquiterpenes, 48 diterpenes, 2 monoterpenes and 1 meroterpenoid, were isolated and identified from Trichoderma species between 1948 and 2022. Pharmacological investigations of Trichoderma terpenoids mainly focused on their antibacterial activities, antifungal activities, inhibitory activities on marine plankton species and cytotoxic activities, indicating that Trichoderma species are important microbial agents for drug discovery and environmentally friendly agrochemicals development. Intriguing chemistry and enzymology involved in the biosynthesis of Trichoderma terpenoids were also presented to facilitate further precise genome mining-guided novel structure discovery. Taken together, the abundance of novel skeletons, bioactivities and biosynthetic potentials presents new opportunities for drug and agrochemicals discovery, genome mining and enzymology exploration from Trichoderma species. The work will provide references for the profound study of terpenoids derived from Trichoderma, and facilitate further studies on Trichoderma species in the areas of chemistry, medicine, agriculture and microbiology.

Two types of city-oriented noise barriers, i.e., fully-enclosed noise barrier and bilateral inverted l-shaped semi-enclosed noise barrier, have been gradually adopted in city centres along high-speed railways to reduce noise pollution. The aerodynamic impacts of high-speed trains present a threat to the long-term durability of the city-oriented noise barriers. To promote the usage and increase the sustainability of city-oriented noise barriers, a moving-model experiment system with city-oriented noise barriers and HST with a scale ratio of 1:16.8 is established. The train type is CRH380A and the train speed is up to 350 km/h. A systematic comparative study on the aerodynamic performance of the two types of city-oriented noise barriers is conducted. The similarities and differences of transient pressure time–histories, spatial distribution of pressure peaks and spectral characteristics of aerodynamic pressure acting on the two types of noise barriers are compared and discussed. Moreover, the influence of train speed on the characteristics of the train-induced aerodynamic pressure is also investigated. The results show that the pressure fluctuation of the two types of noise barriers is caused by different reasons. Compared with the fully-enclosed noise barrier, the transient pressure of the semi-enclosed noise barrier is more sensitive to train speeds. The research results may provide a reference for the engineering design of city-oriented noise barriers on high-speed railways.

Abstract Appropriate modeling of an experimental technology is necessary in order to estimate the aerodynamic characteristic of railway trains and infrastructure (e.g., bridges). Simulation of the earth’s wind characteristics of nature is a well-established practice by using an atmospheric boundary wind tunnel. However, in the mountainous area, the wind characteristics are strikingly different from those of the plain area, the amplitude variation of wind is related to complex terrain. Compared with atmospheric boundary layer winds, which are customarily treated as stationary, winds associated with gust winds originating from mountain areas exhibit rapid changes during a short period. A lack of available field test data and testing techniques has hindered such knowledge of the effect of mountain wind on railway-related applications. To simulate the characteristics of gust winds and prepare for follow-up studies of the impact on the railway-related structures, a gust wind generator was developed in an atmospheric boundary wind tunnel — the CSU wind tunnel. Further, the performance of the gust-wind generator was studied and analyzed under the condition of the combined operation between a gust-wind generator and a wind tunnel.

This paper presents an experimental study on the box girder of a low-tower cable-stayed railway bridge with a W-shaped section that consists of prestressed concrete diagonal braces. A 1:6 scale test model was designed and constructed for the experiment. The mechanical behavior of the test model was investigated under two loading conditions: a double-track train symmetrical load and a single-track train unsymmetrical load. The experimental results were validated against a finite element model. Furthermore, the torsional performance of the box girder section was analyzed and discussed.

Prompt detection of landslides is crucial for reducing the disaster risk and preventing landslides. However, landslide detection in practical applications still faces many challenges, such as the complexity of environmental backgrounds, the diversity of target scales, and the enormity of model weights. To address these issues, this paper proposes a lightweight LBE-YOLO model for real-time landslide detection. Firstly, a lightweight model is designed by integrating the GhostConv lightweight network with the YOLOv8n model. Inspired by GhostConv, this study innovatively designed the GhostC2f structure, which leverages linear thinking to further reduce the model parameters and computational burden. Additionally, the newly designed EGC2f structure, incorporating an attention mechanism, not only maintains the model’s lightweight characteristics but also enhances the network’s capability to extract valid information. Subsequently, the Path Aggregation Network (PAN) was optimized by introducing a bidirectional feature propagation mechanism to improve the model’s feature fusion ability. Additionally, the Bijie landslide dataset was expanded through data augmentation strategies, thereby further improving the model’s generalization capability. The experimental results indicate that, compared to the YOLOv8n model, the proposed model increased accuracy by 4.2%, while the model’s weight and computational load were reduced by 32.0% and 35.5%, respectively. This verifies the superiority of the LBE-YOLO model in landslide target detection, which will help mitigate the impacts of natural disasters.

Abstract The modal parameters identification of bridges under non-stationary environmental excitation has caught the attention of researchers. This paper studies the non-stationarity of wind velocity, and extracts the time-varying mean wind velocity based on a discrete wavelet transform and recursive quantitative analysis. The calculated turbulence intensity and turbulence integral scale under the non-stationary model are smaller than those under the stationary model, especially the turbulence integral scale. The empirical wavelet transform is used to identify the modal parameters of long-span bridges, and the power spectral density spectrum is proposed as a replacement for the Fourier spectrum as the basis of the frequency band selection. The bridge modal parameters are then compared using the covariance-driven stochastic subspace system identification method (SSI-COV) and the Hilbert transform method based on an improved empirical wavelet transform (EWT-HT). Both methods can accurately identify the modal frequency, and the absolute difference between these two methods is equal to 0.003 Hz. The wind velocity results in a change of less than 1% in the modal frequency. The absolute difference between the modal damping ratios identified using SSI-COV and EWT-HT is significant and can reach 0.587%. The modal damping ratios are positively correlated with the mean wind velocities, which aligns with the quasi-steady assumption. In addition, the applicability of SSI-COV and EWT-HT is also evaluated using the standard deviation, coefficient of variation, and range dispersion indicators. The results show that the EWT-HT is more applicable to the identification of the modal parameters of long-span bridges under non-stationary wind velocities.

The application of three-dimensional laser scanning technology in the field of tunnel deformation monitoring has changed the traditional measurement method. It provides an automated and intelligent solution for monitoring the geometric deformation of tunnel sections due to its high efficiency and independence from environmental influences. In this paper, based on B-spline fitting and iterative nearest point (ICP) alignment, the calculation of the difference between the radial distance and the design radius of a tunnel is transformed into a curve transformation that iterates over the nearest-neighbor points and calculates the difference in the distance between the corresponding points. The innovation of this paper is that the high-precision tunnel deformation monitoring method integrating B-spline fitting and ICP alignment can automatically compensate for the missing point clouds, is not affected by the point clouds of the tunnel inner and outer liner appendages, is more sensitive in the local deformation feedback and can be applied to a variety of tunnel shapes. The results indicate that our method maximally improves the accuracy of the horizontal convergence calculation by 28.6 mm and the accuracy of the vault settlement by 27.8 mm in comparison with the least squares circle fitting algorithm.

Ensuring road safety, structural stability and durability is of paramount importance, and detecting road cracks plays a critical role in achieving these goals. We propose a GM-ResNet-based method to enhance the precision and efficacy of crack detection. Leveraging ResNet-34 as the foundational network for crack image feature extraction, we consider the challenge of insufficient global and local information assimilation within the model. To overcome this, we incorporate the global attention mechanism into the architecture, facilitating comprehensive feature extraction across the channel and the spatial width and height dimensions. This dynamic interaction across these dimensions optimizes feature representation and generalization, resulting in a more precise crack detection outcome. Recognizing the limitations of ResNet-34 in managing intricate data relationships, we replace its fully connected layer with a multilayer fully connected neural network. We fashion a deep network structure by integrating multiple linear, batch normalization and activation function layers. This construction amplifies feature expression, stabilizes training convergence and elevates the performance of the model in complex detection tasks. Moreover, tackling class imbalance is imperative in road crack detection. Introducing the focal loss function as the training loss addresses this challenge head-on, effectively mitigating the adverse impact of class imbalance on model performance. The experimental outcomes on a publicly available crack dataset emphasize the advantages of the GM-ResNet in crack detection accuracy compared to other methods. It is worth noting that the proposed method has better evaluation indicators in the detection results compared with alternative methodologies, highlighting its effectiveness. This validates the potency of our method in achieving optimal crack detection outcomes.

The occurrence of unintentional islanding will seriously threaten the stable operation of a microgrid (MG). Therefore, detecting the islanding of an microgrid timely is an important premise to ensure the microgrid operates safely and stably. However, the problem of dead zone exists in the traditional islanding detection process because the threshold of various electrical feature quantities of the point of common coupling (PCC) cannot be determined effectively. To solve this problem, an islanding detection method based on CatBoost is proposed for an microgrid. The novelty of this method lies in two aspects: 1) To reduce the error brought by the electrical feature quantities with weak correlation in the process of islanding detection, an analysis method based on the Spearman correlation coefficient is used to extract the electrical feature quantities closely related to islanding detection. 2) To determine the threshold of the electrical feature quantities more accurately and reduce the dead zone of island detection, an integrated learning machine is used to dig out correlations between the electrical feature quantities and the operation of an microgrid. The performance of the proposed islanding detection method is verified based on the modified IEEE13-bus system. The results of the example verify that the proposed islanding detection can achieve higher detection accuracy in cases of grid-connected interference and line faults.

This paper presents a new type of wind guide barrier (WGB). Through wind tunnel experiments, the key parameters of three types of WGB were studied, as well as their effects on the aerodynamic characteristics of a high-speed train and blunt body box girder system, while the bridge deck wind field was investigated. The results show that the shielding effect is the main factor affecting the windproof performance of the WGB. When the WGB is installed, the mean wind pressure distribution on the train is comparable to that of using a vertical wind barrier while reducing barrier resistance and the resistance of the bridge–barrier system. At the same time, the WGB can guide the oncoming flow, resulting in an increase in the streamwise and vertical wind velocity ratios on the bridge deck, as well as an increase in the maximum aerodynamic coefficient on the train.

Wind speed forecasting is advantageous in reducing wind-induced accidents or disasters and increasing the capture of wind power. Accordingly, this forecasting process has been a focus of research in the field of engineering. However, because wind speed is chaotic and random in nature, its forecasting inevitably includes errors. Consequently, specifying the appropriate method to obtain accurate forecasting results is difficult. The probabilistic forecasting method has considerable relevance to short-term wind speed forecasting because it provides both the predicted value and the error distribution. This study proposes a probabilistic forecasting method for short-term wind speeds based on the Gaussian mixture model and long short-term memory. The precision of the proposed method is evaluated by prediction intervals (i.e., prediction interval coverage probability, prediction interval normalized average width, and coverage width-based criterion) using 29 monitored wind speed datasets. The effects of wind speed characteristics on the forecasting precision of the proposed method were further studied. Results show that the proposed method is effective in obtaining the probability distribution of predicted wind speeds, and the forecast results are highly accurate. The forecasting precision of the proposed method is mainly influenced by the wind speed difference and standard deviation.

Porous wind barriers (PWBs) are gradually applied to tunnel–bridge–tunnel infrastructures (TBTIs) along high-speed railway lines. Due to the remarkable aerodynamic effect of high-speed trains (HSTs), the windproof performance of a PWB at tunnel–bridge section (TBS) is particularly critical when a HST passes through the TBTI under crosswind. And it seems to be easily ignored by researchers. This study aims to determine the influence mechanism of the PWB in the TBS. A CFD dynamic model of air–train–PWB was built based on porous media theory, and its reliability is verified by model and field tests. The main results are as follows: the corresponding variation amplitudes of the train’s aerodynamic load coefficients are reduced by 36–95% when a PWB is set in the TBS; adopting the same design parameters along the full-length PWB on the TBTI is unreasonable; the PWB height and porosity in the TBS must be increased and reduced more than 33%, respectively, to achieve equivalent windproof performance. The conclusions in this paper can provide a preliminary idea for the optimization design of the PWB on the TBTI.

Cable-supported photovoltaic systems (CSPSs) are a new technology for supporting structures that have broad application prospects owing to their cost-effectiveness, light weight, large span, high headroom, few pile foundations, short construction period, and symbiosis with fisheries and farms. Recently, a new CSPS with a much smaller settlement and stronger wind resistance was proposed. The new CSPS, with a 10% lower cost compared with traditional fix-tilted PV support, is a better alternative to traditional photovoltaic (PV) support systems. In this study, the failure models and bearing capacity of the primary structures of the new CSPS were investigated in detail using the FEM method, and a design method for the new structure was proposed based on the limit state design method. The results showed that the structure had a strong load-bearing capacity. Failure of the cables and triangular brackets are the two main types of failure of the primary structure. The cross-sectional area of the cables is the most important factor affecting the load-bearing capacity of the structure and directly affecting the failure modes of the CSPS. The numerical case verified that the proposed design method works well and that the designed structure has sufficient loading capacity and is cost-effective.

A running train induces a slipstream around it, which is closely related to its aerodynamic features and crucial for the safety of people and structures near the track. However, the effect of crosswinds is almost inevitable when the train runs on a bridge. In this work, an experimental study using moving model testing technology was conducted to investigate the effects of wind speeds, train speeds, and yaw angles on the aerodynamic performance of a Fuxing Hao high-speed train running on a bridge under the influence of crosswind. The results show that, for the crosswind cases, the slipstream velocities on the leeward side of the train are generally higher than those in the no-crosswind cases. Moreover, the results were compared for the cases with the same effective yaw angle of 21.8° but different wind speeds (6 m/s, 8 m/s) and train speeds (15 m/s, 20 m/s), which suggests the method of the resultant wind’s yaw angle is no longer valid when the train runs on a bridge due to the aerodynamic interactions.

A high-speed train will likely experience hazardous driving environments because of the transient effect of complex airflow condition when the train runs on the infrastructure scenario consisting of the tunnel–bridge–tunnel under crosswind. The evolution of aerodynamic loads and flow structure is investigated by numerical simulations. In these simulations, the arrangement of an infrastructural scenario refers to a real prototype under construction. Results indicate the flow structure and pressure distribution around a train change from a symmetrical state in the tunnel to a remarkable asymmetry state in the bridge within 0.1 s. This phenomenon causes a sharp aerodynamic shock on the train body. The coupling effect of the crosswind environment and the transformation of the train running scenario will likely affect the transient aerodynamic response. The maximum values of different aerodynamic loads exhibit time-resolved discrepancy when a train runs in ISTBT. The transient characteristics of the aerodynamic loads strengthen with the increase in wind speed but weaken with the increase in train speed. Such characteristics will likely deteriorate further if the wind direction is in the opposite direction relative to that of a moving train.

With the increase of the running speed of the high-speed train (HST), aerodynamic interference between the HST and surrounding structures becomes more and more important. Traditional wind tunnel experiments using the stationary model can not fully reveal the pulsing behavior of the aerodynamic forces on both the HST and surrounding structures. This paper numerically investigates the aerodynamic characteristics of an HST running on a bridge in cross-wind. The simulation results reveal that when there is no wind barrier, the stationary model case with the yaw angle identical to the moving model case can roughly reproduce the main flow structures around the train. However, once the train runs downstream a wind barrier, the stationary model cannot reveal its aerodynamic characteristics regardless of the yaw angle adopted. The moving model scenario successfully captures the pulsing behavior of the forces on both the train and wind barrier, which is concealed in the cases with a stationary model. The present results indicate that only the moving model method can fully reveal the aerodynamic characteristics and interactions between the train and surrounding structures, especially in evaluating their dynamic response.

Prostate cancer is the second most common malignant cancer in males. It involves a complex process driven by diverse molecular pathways that closely related to the survival, apoptosis, metabolic and metastatic characteristics of aggressive cancer. Prostate cancer can be categorized into androgen dependent prostate cancer and castration-resistant prostate cancer and cure remains elusive due to the developed resistance of the disease. Natural compounds represent an extraordinary resource of structural scaffolds with high diversity that can offer promising chemical agents for making prostate cancer less devastating and curable. Herein, those natural compounds of different origins and structures with potential cytotoxicity and/or in vivo anti-tumor activities against prostate cancer are critically reviewed and summarized according to the cellular signaling pathways they interfere. Moreover, the anti-prostate cancer efficacy of many nutrients, medicinal plant extracts and Chinese medical formulations were presented, and the future prospects for the application of these compounds and extracts were discussed. Although the failure of conventional chemotherapy as well as involved serious side effects makes natural products ideal candidates for the treatment of prostate cancer, more investigations of preclinical and even clinical studies are necessary to make use of these medical substances reasonably. Therefore, the elucidation of structure-activity relationship and precise mechanism of action, identification of novel potential molecular targets, and optimization of drug combination are essential in natural medicine research and development.

Introduction: With the development of transportation system and the economy, the rapidly increasing number of automobiles brings the associated problem of road traffic noise, especially in metropolitan and densely populated high-rise cities like Hong Kong. In Hong Kong, approximately one million people are affected by severe road traffic noise. Excessive noise exposure is hazardous to the health and wellbeing of people and therefore has drawn progressively more attention in Hong Kong. The Calculation of Road Traffic Noise (CRTN) has been adopted as the sole tool to evaluate road traffic noise in the form of descriptor LA10. The accuracy and suitability of the CRTN method for predicting road traffic noise in Hong Kong were evaluated in this study by comparing the prediction results and measured traffic noise levels. The results show that the CRTN method was able to provide adequate predictions with correlation coefficients of 0.8032 and 0.7626 between the predicted and measured LA10 for 2007 and 2017 respectively. The predicted traffic noise levels on different floors of seven selected residential buildings in 2017 were compared with those predictions for the same buildings in 2007. The worsening traffic noise exposure in these residential buildings was analysed and some suggestions and counter-measures to alleviate the traffic noise problems are put forward. Since the situation of Hong Kong is an example of what may happen in other cities, the present longitudinal study of the road traffic noise in Hong Kong hopes to contribute to a better urban acoustic environment worldwide. Context: Excessive noise exposure is hazardous to the health and wellbeing of people and therefore has drawn progressively more attention in Hong Kong. The urban road traffic noise exposure of residential buildings in Hong Kong over the past decade has been analysed. Aims: This study aims to assess the road traffic noise exposure of residential buildings over the past decade. Settings and Design: Measurements of traffic noise levels at some selected residential buildings were first conducted in 2007, and then repeated at the same buildings in 2017. Material and Methods: The CRTN was adopted to predict the traffic noise levels based on the recorded traffic flow data. Results: The exposure of these buildings to road traffic noise is higher in 2017 than in 2007. The study illustrates that the deterioration of the urban acoustic environment may not be caused by an increased total number of vehicles, but that heavy vehicles are dominantly responsible for the increased traffic noise levels. Restriction of vehicle velocity for urban street canyons is useless for road traffic noise control. Conclusions: This study shows the deterioration of traffic noise levels is mainly due to the increased heavy vehicles instead of the increased total number of vehicles. The alleviation of traffic noise levels by velocity restriction may not be obvious for urban street canyons and may only work with a certain velocity range.

Due to the coupling impacts of solar radiation, wind, air temperature and other environmental parameters, the temperature field of steel structures is significantly non-uniform during their construction and service stages. Corrugated web steel beams have gained popularity in structural engineering during the last few decades, while their thermal actions are barely investigated. In this paper, both experimental and numerical investigations were conducted to reveal the non-uniform features and time variation of the corrugated web steel beams under various environmental conditions. The heat-transfer simulation model was established and verified using the experimental temperature data. Both the experiment and simulation results demonstrate that the steel beam has a complicated and non-uniform temperature field. Moreover, 2-year continuous numerical simulations of steel beams’ thermal actions regarding eight different cities were carried out to investigate the long-term temperature variations. Finally, based on the long-term simulation results and extreme value analysis (EVA), the representative values of steel beams’ daily temperature difference with a 50-year return period were determined. The extreme temperature difference of the steel beam in Harbin reached up to 46.9 °C, while the extreme temperature difference in Haikou was 28.8 °C. The extreme temperature difference is highly associated with the steel beam’s location and surrounding climate. Ideally, the outcomes will provide some contributions for the structural design regarding the corrugated web steel beam.

With the intensification of energy consumption, how to make rational and efficient use of wind energy has been studied all over the world. The construction of facilities to obtain wind energy requires an accurate assessment of the wind characteristics of the local terrain. In order to study the wind characteristics on an island in Southeast China, a 1:1300 terrain model is established, and the characteristics of mean wind and fluctuating wind are studied by numerical simulation and wind tunnel test. The results show that wind speed is affected by the incoming wind direction and local terrain. Wind speed on windward slopes and flat areas with no obstructions is higher, and wind speed on leeward slopes and valleys is lower. Then, the wind attack angle of each measuring point is mainly in the range of −10°~10°, which is much higher than that in flat areas. The positive and negative wind attack angles are controlled by the incoming wind direction, and the size is closely related to the local terrain. As for pulsation characteristics, the disturbance of the inflow determines the turbulence intensity. The incoming wind direction mainly affects the turbulence intensity on the hillside, while the turbulence intensity in the valley and flat area is controlled by the local terrain. In addition, the fluctuating wind speed power spectra on the island is more consistent with the von Karman spectrum, which is quite different from the Kaimal spectrum. The bandwidth on hillsides and valleys will not change with the change in inflow, but for flat areas, the bandwidth is greatly affected by the inflow direction.

Wind tunnel tests were carried out to measure the wind pressure of a 200 m high natural-draught cooling tower. An analysis of the distribution characteristics of external pressure was then conducted to determine the pressure coefficients Cp(θ, z) in a given wind profile. Finally, the effect on the response of the shell and the buckling safety of the shell, applying the simplified height-constant pressure coefficient Cp(θ) and the realistic pressure Cp(θ, z), was determined. Taking the wind load specified in the code as an example, the influence of the distribution of external pressure on the wind-induced response was further analyzed. The results indicate that the pressure distribution varies with not only the height z but also the circumferential angle θ, and the wind load of both ends of the tower is significantly greater than that of its middle. Moreover, the wind-induced static responses of the tower under the action of the realistic pressure distribution Cp(θ, z) and the simplified approach Cp(θ) are basically consistent, because the wind load distribution is more important than its magnitude for the wind-induced response of cooling tower, and the wind-induced response of the cooling tower is dominated by the local shell deformation.

The objective of the present research was to study the effect of temperature on the mechanical properties, failure mode and uniaxial compression constitutive relationship of a modified polyurethane concrete. A total of 24 cube and 27 prism specimens were fabricated, and the uniformity of the polyurethane concrete was checked. The compressive test, splitting tensile test and static uniaxial compression test were carried out at 0, 15, 40 and 60 °C. The failure mode, cube compressive strength, splitting tensile strength, axial compressive strength, elastic modulus and the compressive stress–strain curves of the modified polyurethane concrete were obtained. Based on the experimental results, a uniaxial compression constitutive model of the modified polyurethane concrete considering temperature characteristics was proposed. The results show that the elastic modulus, cubic compressive strength, splitting tensile strength and axial compressive strength of the modified polyurethane concrete decrease with the increase of temperature, and the peak strain and ultimate strain increase significantly. When the temperature rises from 0 to 60 °C, the cubic compressive strength, splitting tensile strength and axial compressive strength are decreased by 67.1%, 66.4% and 73.3%, respectively. The calculation results of the proposed constitutive model are in good agreement with the test results. The results are expected to guide the application of the modified polyurethane concrete in bridge deck pavement.

Wind barriers can effectively reduce the risk of overturning and derailment of high-speed trains running on a bridge under crosswind. However, it can adversely affect the wind resistance of the bridge. There are few studies on the aerodynamic performance of curved wind barriers. In this paper, the effects of curved wind barriers with four curvatures (0, 0.2, 0.35, and 0.50) and different train-bridge combinations on the crosswind aerodynamic characteristics of a train-bridge system are investigated. The results show that the curved wind barrier can significantly reduce the wind speed below a certain height on the bridge deck. The curved wind barrier with small curvature can better reduce the aerodynamic force of the train; however, it greatly increases the aerodynamic force of the bridge. A wind barrier with a curvature of 0.35 is recommended because it takes into account the aerodynamic characteristics of the train and bridge at the same time. The porosity of a wind barrier greatly influences the aerodynamic performance of the train on the track of the windward side of the bridge, while the wind barrier has little effects on the train on the track of the leeward side of the bridge. The aerodynamic performance of the train on the track of the windward side of the bridge is less affected by whether or not a train on the track of the leeward side of the bridge is present.

Wind tunnel tests are a commonly used method for studying wind characteristics of complex terrain; but truncation of the terrain model is usually unavoidable and affects the accuracy of the test results. For this reason, the effects of truncated and original terrain models on the simulation of wind characteristics for complex terrain were investigated by considering both nontruncated and truncated models, with the truncated model considering the applicability of two types of transition sections. The results show that the effect of topographic truncation on profiles of mean velocity and turbulence intensity is different for regions and that inclination angle profiles are extremely sensitive to the changing topographic features upwind. In those cases, the spectra of streamwise velocity were overestimated in the low-frequency range but underestimated in the high-frequency range due to topographic truncation. At the same time, the less negative value of the slope of the spectra was found at the inertial subrange. Furthermore, the normalized bandwidth was also influenced by topographic truncation, which was narrowed in windward and leeward regions and broadened in the valley region. We should note that the performance of the transition sections used in this study was quite limited and even resulted in inaccuracies in the simulation.

The intelligent crack detection method is an important guarantee for the realization of intelligent operation and maintenance, and it is of great significance to traffic safety. In recent years, the recognition of road pavement cracks based on computer vision has attracted increasing attention. With the technological breakthroughs of general deep learning algorithms in recent years, detection algorithms based on deep learning and convolutional neural networks have achieved better results in the field of crack recognition. In this paper, deep learning is investigated to intelligently detect road cracks, and Faster R-CNN and Mask R-CNN are compared and analyzed. The results show that the joint training strategy is very effective, and we are able to ensure that both Faster R-CNN and Mask R-CNN complete the crack detection task when trained with only 130+ images and can outperform YOLOv3. However, the joint training strategy causes a degradation in the effectiveness of the bounding box detected by Mask R-CNN.

Train speed is increasing due to the development of high-speed railway technology. However, high-speed trains generate more noise and discomfort for residents, enclosed housing for sound emission alleviation is needed to further reduce noise. Because these enclosed housings for sound emission alleviation restrain the air flow, strong and complicated aerodynamic pressures are generated inside the housing for sound emission alleviation when a train passes through at a high speed. This train-induced aerodynamic pressure, particularly its dynamic characteristics, is a key parameter in structural design. In the present study, the train-induced unsteady aerodynamic pressure in an enclosed housing for sound emission alleviation is simulated using the dynamic mesh method, and the dynamic characteristics of the aerodynamic pressure are investigated. The simulation results show that when the train is running in the enclosed housing for sound emission alleviation, the unsteady aerodynamic pressure is complicated and aperiodic, and after the train leaves the housing for sound emission alleviation, the aerodynamic pressure reverts to periodic decay curves. Two new terms, the duration of the extreme aerodynamic pressure and the pressure change rate, are proposed to evaluate the dynamic characteristics when the train passes through the barrier. The dominant frequency and decay rate are adopted to express the dynamic characteristics after the train exits. When the train runs in the enclosed housing for sound emission alleviation, the longest durations of the positive and negative extreme aerodynamic pressures are in the middle section, and the maximum change rate of aerodynamic pressure occurs at the entrance area. After the train exits the housing for sound emission alleviation, the pressure amplitude at the central region is always higher than those close to the entrance/exit. The dominant frequency of the aerodynamic pressure is identified and explained using wave propagation theory, the decay rate of the aerodynamic pressure at all sections is close.

Structural damage identification technology is of great significance to improve the reliability and safety of civil structures and has attracted much attention in the study of structural health monitoring. In this paper, a novel structural damage identification method based on transmissibility in the time domain is proposed. The method takes the discrepancy of transmissibility of structure response in the time domain before and after damage as the basis of finite element model updating. The damage is located and quantified through iteration by minimizing the difference between the measurements at gauge locations and the reconstruction response extrapolated by the finite element model. Taking advantage of the response reconstruction method based on empirical mode decomposition, damage information can be obtained in the absence of prior knowledge on excitation. Moreover, this method directly collects time-domain data for identification without modal identification and frequent time–frequency conversion, which can greatly improve efficiency on the premise of ensuring accuracy. A numerical example is used to demonstrate the overall damage identification method, and the study of measurement noise shows that the method has strong robustness. Finally, the present work investigates the method through a simply supported overhanging beam. The experiments collect the vibration strain signals of the beam via resistance strain gauges. The comparison between identification results and theoretical values shows the effectiveness and accuracy of the method.

This paper focuses on the dynamic characteristics of the metro train’s bogie frames based on the field test data. The acceleration signals of both motor bogie frame and trailer bogie frame of a standard B-type metro train were measured. Running tests on the Metro line 21 of Guangzhou (China) were carried out. The acquired acceleration signals of bogie frames were analyzed through several methods to identify the dynamic characteristics of the motor and trailer bogies in the time-frequency domain. The spectral analysis and time-frequency representations show that noise components exist in the high-frequency domain of the original signal, especially for the acceleration signal of the motor bogie frame. Then, the soft thresholding process and discrete wavelet transform decomposition process are conducted to obtain a denoised version of the original signals in the time-frequency domain. The vibration frequency domain and energy distribution of bogie frames under different train speeds are analyzed. The track irregularity wavelength of the metro line is calculated and analyzed based on the measured bogie frames’ acceleration signals. The dynamic characteristics of the metro train’s bogie frames in this paper can be adopted as a reference in the track diagnosis of the elevated metro line.

The aerodynamic features of a train and flat closed-box bridge system may be highly sensitive to train-bridge aero interactions. For the generally utilized railway bridge-deck with two tracks (the upstream and downstream ones), the aero interactions above are occupied-track-dependent. The present paper thus aims to reveal the aero interactions stated above via a series of wind tunnel tests. The results showed that the aero interactions of the present train-bridge system display four typical behaviors, namely, the underbody flow restraining effect, bridge deck shielding effect, flow transition promoting effect, and the flow separation intensifying effect. The above four aero interactions result in obvious reductions in the aerodynamic forces of the train in wind angle of attack α of [−4°, 12°] and in the static stall angle of the bridge-deck, and leads to sensible increases in the absolute values of the bridge aerodynamic forces in α of [−4°, 12°]. Upon comparing the results with the same train and bridge system but with the train model mounted on the downstream track, the quasi-Reynolds number effect was non-detectable when the train model was moved to the upstream track. Thus, no drag crisis and other saltatory aerodynamic behaviors were observed in the present study in α of [0°, 12°].

The suspended monorail (SM) vehicle–bridge system has been considered a promising modern transit mode due to its clear advantages: low pollution, high safety, convenient construction, and low cost. The wind-induced response can significantly affect the running safety and comfort of this type of vehicle due to its special suspended position from a fixed track. This study is the first to systematically investigate its aerodynamic characteristics and interference effects under various spacing ratios using wind tunnel tests and numerical simulations. A high level of agreement between the wind tunnel test and CFD (computational fluid dynamics) results was obtained, and the aerodynamic interference mechanism can be well explained using the CFD technique from a flow field perspective. A wireless wind pressure acquisition system is proposed to achieve synchronization acquisition for multi wind pressure test taps. The paper confirms that (1) the proposed wireless wind pressure acquisition system performed well; (2) the aerodynamic coefficients of the upstream vehicle and bridge were nearly unchanged for vehicle–bridge combinations with varying spacing ratios; (3) the aerodynamic interference effects were amplified when two vehicles meet, but the effects decrease as the spacing ratio increases; (4) the aerodynamic force coefficients, mean, and root mean square (RMS) wind pressure coefficients for the downstream vehicle and bridge are readily affected by the upstream vehicle; (5) the vortex shedding frequencies of vehicles and bridges can be readily obtained from the lift force spectra, and they decrease as the spacing ratio increases; and (6) a spacing ratio of 3.5 is suggested in the field applications to ensure the running safety and stability of the SM vehicle–bridge system under exposure to crosswinds.

Friction action is a damping mechanism used in civil structures. It often works together with traditional viscous damping. The rolling friction action is nonlinear, and its scaling process in shaking table model tests is suspect, especially in cases of working in combination with traditional viscous dampers. To solve the problem, a numerical model of simplified viscous damper-Coulomb friction base isolation system was scaled. The comparison between the scaled and the prototype model results showed two important factors that influence the scaling of rolling friction action. One factor is the unscaled gravity acceleration, which results in an adverse friction force and seismic responses of scaled models. These adverse seismic responses can be improved by changing the friction coefficient to correct for the abovementioned adverse friction force in the dynamic equation. Another factor is the friction variation in space, causing adverse scaled seismic responses. These adverse seismic responses can be improved by moving the variable friction positions along the scaled size of contact surface. The influence of the above two factors can be weakened by increasing the traditional viscous damping component and the earthquake intensity.

Wind barrier structures on railway bridges are installed to mitigate the wind effects on travelling trains; however, they cause additional wind loads and associated aerodynamic effects on the bridge. An innovative concept was developed for a wind barrier structure in this study that used a glass–fibre–reinforced polymer (GFRP) that may deform properly when subjected to a crosswind. Such deformation then allows for wind to pass, therefore reducing the wind loads transferred to the bridge. Wind tunnel experiments were conducted on a 1/40-scale train and bridge models with the proposed GFRP barrier subjected to airflow at different speeds up to 20 m/s. The side-force and overturning-moment coefficients of both the train and the bridge were evaluated to characterise the aerodynamic effects. The results show that favourable side-force and overturning-moment coefficients of the train were provided by wind barriers taller than 10 cm. The aerodynamic coefficients of the train were not significantly affected by the airflow speeds; meanwhile, the overturning-moment coefficient of the bridge decreased with the increase in airflow speed due to smaller wind resistance of the barrier after deformation. A numerical analysis was conducted on both the reduced- and full-scale models of the train–barrier–bridge system and the results supported the findings obtained from the wind tunnel experiments.

Digital image projection (DIP) with traditional vertical calibration cannot be used for measuring the water droplets/film on a curved surface, because significant systematic error will be introduced. An improved DIP technique with normal calibration is proposed in the present paper, including the principles, operation procedures and analysis of systematic errors, which was successfully applied to measuring the water droplets/film on a curved surface. By comparing the results of laser profiler, traditional DIP, improved DIP and theoretical analysis, advantages of the present improved DIP technique are highlighted.

This study carries out a detailed full-scale investigation on the strong wind characteristics at a cable-stayed bridge site and associated buffeting response of the bridge structure during construction, using a field monitoring system. It is found that the wind turbulence parameters during the typhoon and monsoon conditions share a considerable amount of similarity, and they can be described as the input turbulence parameters for the current wind-induced vibration theory. While the longitudinal turbulence integral scales are consistent with those in regional structural codes, the turbulence intensities and gust factors are less than the recommended values. The wind spectra obtained via the field measurements can be well approximated by the von Karman spectra. For the buffeting response of the bridge under strong winds, its vertical acceleration responses at the extreme single-cantilever state are significantly larger than those in the horizontal direction and the increasing tendencies with mean wind velocities are also different from each other. The identified frequencies of the bridge are utilized to validate its finite element model (FEM), and these field-measurement acceleration results are compared with those from the FEM-based numerical buffeting analysis with measured turbulence parameters.

This paper focuses on the dynamic responses of a metro train−bridge system under train-braking. Experiments were performed on the elevated Metro Line 21 of Guangzhou (China). A continuous, three-span, rigid-frame bridge (42 m + 65 m + 42 m) and a standard B-type metro train were selected. The acceleration signals were measured at the center-points of the main span and one side-span, and the acceleration signals of the car body and the bogie frame were measured simultaneously. The train−bridge system’s vibration characteristics and any correlations with time and frequency were investigated. The Choi−Williams distribution method and wavelet coherence were introduced to analyze the obtained acceleration signals of the metro train−bridge system. The results showed that the Choi−Williams distribution provided a more explicit understanding of the time−frequency domain. The correlations between different parts of the bridge and the train−bridge system under braking conditions were revealed. The present study provides a series of measured dynamic responses of the metro train−bridge system under train-braking, which could be used as a reference in further investigations.

Dynamics of the double-beam system under moving loads have been paid much attention due to its wide applications in reality from the analytical point of view but the previous studies are limited to the simply supported boundary condition. In this study, to understand the vibration mechanism of the system with various boundary conditions, the double-beam system consisted of two general beams with a variety of symmetric boundary conditions (fixed-fixed, pinned-pinned, fixed-pinned, pinned-fixed and fixed-free) under the action of a moving force is studied analytically. The closed-form frequencies and mode shapes of the system with various symmetric boundary conditions are presented by the Bernoulli-Fourier method and validated with Finite Element results. The analytical explicit solutions are derived by the Modal Superposition method, which are verified with numerical results and previous results in the literature. As found, each wavenumber of the double-beam system is corresponding to two sub-modes of the system and the two sub-modes associated with the first wavenumber of the system both contribute significantly to the vibration of the system under a moving force. The analytical solutions indicate that the mass ratio, the bending stiffness ratio, the stiffness ratio of contact springs and the speed ratio of the moving force are the factors influencing the vibrations of the system under a moving force. The relationships between these dimensionless parameters and the displacement ratio of the system are investigated and presented in the form of plots, which could be referred in the design of the double-beam system.

The wind-sensitive long-span suspension bridge is a vital element in land transportation. Understanding the wind characteristics at the bridge site is thus of great significance to the wind- resistant analysis of such a flexible structure. In this study, a strong wind event from a landfall typhoon called Soudelor recorded at the Jiangyin Bridge site with the anemometer is taken as the research object. As inherent time-varying trends are frequently captured in typhoon events, the wind characteristics of Soudelor are analyzed in a non-stationary perspective. The time-varying mean is first extracted with the wavelet-based self-adaptive method. Then, the non-stationary turbulent wind characteristics, e.g.; turbulence intensity, gust factor, turbulence integral scale, and power spectral density, are investigated and compared with the results from the stationary analysis. The comparison highlights the importance of non-stationary considerations of typhoon events, and a transition from stationarity to non-stationarity for the analysis of wind effects. The analytical results could help enrich the database of non-stationary wind characteristics, and are expected to provide references for the wind-resistant analysis of engineering structures in similar areas.