Advances in Civil Engineering

Geological conditions and supporting structures are critical factors influencing the deformation characteristics of deep excavations. This study investigates the deformation characteristics and corresponding control measures for typical deep excavations, focusing on a metro station excavation within a mixed soil–rock stratum in Guangzhou. Using field measurement data collected during the excavation phase, we perform a statistical analysis to examine the relationship between maximum deformation and various influencing factors, including excavation depth, spatial effects, and the insertion ratio of the support structure. Additionally, we explore the distribution of excavation deformations, the relationship between lateral and vertical displacements, and deformation modes, offering engineering recommendations for optimization. Our analysis shows that, due to significant variations in the thickness of soft soil layers in Guangzhou, the maximum lateral displacement of the support structures predominantly ranges from 15 to 30 mm, while vertical ground deformations range from 0.86‰ to 2.35‰ of the excavation depth. Increasing the insertion ratio of the support structures improves their stiffness and reduces surface settlement caused by excavation. However, when the base of the support structure is embedded in the load-bearing rock layer and the insertion ratio exceeds 0.25, further increases in the insertion ratio lead to diminishing returns in controlling surface settlement. Both vertical ground deformations and lateral displacements of the support structures are positively correlated with excavation depth, while negatively correlated with the length-to-width ratio, width-to-depth ratio, and insertion ratio of the excavation. Based on these findings, we propose construction measures to enhance the stability of deep excavations and protect adjacent structures.

The integrated modular house by folding pack incorporates key components, primarily focused on joints, particularly occlusion and insertion joints between plates with expansion functionality. These joints are considered structural discontinuities. This study aims to develop a finite element checking method that accurately reflects the actual contact state of key joints in an integrated modular house by folding pack. The investigation delves into the mechanical properties of such houses, establishing a finite element model for the house joints based on elastic‐plastic contact theory. The analysis provides insights into stress and displacement distributions within the house. Simultaneously, a full‐scale experimental test is conducted on the structural occlusion joint between the roof and end plate, which fails at a load of 4.632 kN, with results compared to numerical findings. The study validates the safety and reliability of the structural occlusion joint. Both experimental and numerical results show that the stress and displacement of the structure under various load combinations meet safety and reliability requirements. The finite element analysis of the joint between the roof and end wallboard closely aligns with experimental results. The observed joint strength at failure significantly exceeds the design load, with the joint enduring up to 4.632 kN before failing, affirming its safety and reliability. Moreover, the structural occlusion joint exhibits no evident plastic deformation after 30 cycles, satisfying the requirement for continuous fault‐free cycles.

This study investigates the seismic performance and torsional responses of a 5‐floor steel‐reinforced concrete (SRC) structure with special‐shaped columns. A three‐dimensional seismic simulation shaking table test was conducted to analyze the dynamic coupling effects in lateral, torsional, and lateral‐torsional directions. The results reveal distinct torsion coupling phenomena in the Y ‐ and X ‐directions during high‐order vibration modes. As seismic intensity increases, the free vibration frequency of the frame structure decreases steadily, while the acceleration amplification coefficient shows a tendency toward reduction. The internal damage to the structure and energy dissipation increase with higher seismic intensities. Notably, when subjected to an 0.80 g PHGA earthquake intensity level, the maximum inter‐storey drift ratio attributed to lateral‐torsional coupling exceeds the required elastic–plastic inter‐storey drift ratio threshold (1/39). Additionally, the damage index of the frame structure, calculated using a deformation and energy parameter model, is 0.56. A novel mathematical model for lateral‐torsional coupled vibration has been developed based on experimental data. The findings indicate that accidental eccentric torsion has minimal impact on the seismic performance of the model structure, with an accidental relative eccentric distance less than 0.1. These results demonstrate superior seismic performance and high torsional deformation capacity of the special‐shaped column design, offering valuable insights for improving earthquake‐resistant structural designs in modern buildings.

Managing concrete segregation during transportation and pouring at construction sites is posed as a substantial challenge. The utilization of continuous mixer units to address segregation and enhance the quality of concrete is discussed in this paper. These mixer units were tested in both horizontal (M–Y mixer) and vertical (ESG mixer) setups. “M–Y” signifies “Maeda–Yamada,” and “ESG” stands for “Energy Saving Gravity.” Fly ash paste and water, representing segregated paste, were used for remixing in the M–Y mixer, while segregated concrete was used in the ESG mixer units to evaluate whether both types of mixer units enhanced the quality of the segregated materials. In the M–Y mixer, the successful mixing of fly ash paste and water was achieved, leading to the attainment of the desired higher water‐to‐powder ratio. The paste content was increased from 40% to 50% and 60%. When the initially segregated concrete was introduced into the ESG mixer, it underwent a transformation into well‐mixed concrete, exhibiting a slump value of 13.5 cm. The 28‐day compressive strength of the segregated concrete witnessed a significant improvement, being elevated from 11.9 to 39.5 MPa. During transportation on the conveyor belt, the concrete was subject to segregation, resulting in a 9.4% reduction in compressive strength. Additionally, during descent through the chute, a decrease of 16.1% was observed. However, through careful adjustments of the ESG mixer units in the chute, the concrete’s performance was enhanced to a level comparable to that achieved at the batching plant. The application of continuous mixer units contributed to the improvement of both the workability and strength of the segregated concrete. This result signifies the improvement in the strength, serviceability, and durability of concrete structures with the enhancement of concrete quality at construction sites.

This paper introduced a road‐use optical fiber sensor with obvious sensing performance that meets the road service conditions and solves the problem of low matching degree between optical fiber sensing technology and the road environment and poor sensing performance at the present stage. The strain transfer formula of the optical fiber was derived through the three‐layer sensing model. The packaging structural material of the sensor was optimized according to the service conditions of the road, and the influence law of the size effect on the road structure was revealed. The sensing effect of the proposed optical fiber sensor was verified by comparison. The results indicate that road temperature, strain, and cross‐coupling effect all affect the center wavelength of the sensor. With the increase of sensor length and diameter, the stress on asphalt layer material decreases, and the stress of the sensor itself is related to the buried layer and the ratio of length to width, the sensors embedded on the upper level or with a larger ratio of length to width bear greater stress. The sensing performance of the sensor at the optimal size is sensitivity 2.124 pm/με, accuracy 2.5 με, and resolution 1.0 με. It can achieve accurate road measurements.

The construction industry in Saudi Arabia has been experiencing poor cost and time performance, leading to financial losses for all project parties involved. This study analyzes the cost and schedule performance of horizontal and vertical projects constructed at a public university between 2012 and 2022. Data on construction costs and schedules were collected and compared to assess project performance, such as cost growth and schedule growth. The findings from analyzing the project data were then used to formulate the interview questions designed to understand key factors contributing to cost and schedule growth and to explore potential solutions. Additionally, factors influencing project cost and time, as identified from a thorough review of previous studies, were used to guide the analysis and the interview process. The results indicate that vertical projects experienced more cost and schedule growth than horizontal projects. Altogether, 80% of both vertical and horizontal projects exceeded their planned budgets by an average of 5%, and ~95% of those projects were completed behind their planned schedules, with an average delay of 160%. The interviews revealed several factors affecting project performance, including owner-related issues such as change orders, payment delays, design errors, and inaccurate quantity estimates; contractor-related issues such as delays in material approvals and inadequate planning; labor-related challenges such as shortages of workers and unavailability of skilled laborers; and government-related challenges such as taxes, visa restrictions, and localization requirements. The findings of this study can help universities in taking proactive steps to reduce changes in construction project costs and durations, thereby improving the overall performance of construction projects.

This article explores the durability and cracking defects associated with 3D-printed concrete, a rapidly emerging technology in construction. As the demand for innovative building techniques grows, understanding the long-term performance of 3D-printed structures becomes crucial. The most important properties of these products are the resistance to freezing and thawing and the possibility of cracking during maintenance. A fine-grained concrete mixture with expanded perlite additive was tested on strength, freezing-thawing resistance, and the reasons for cracking were analyzed during maintenance. Some differences between the results from standard concrete specimens and the results from 3D-printed concrete were obtained experimentally. During the research, 3D-printed concrete specimens were produced with industrial equipment, the density and compressive strength were determined, the mass loss of concrete specimens after freeze/thaw cycles was tested. By reducing the water-to-cement ratio to 11%, the strength of concrete with expanded perlite additive increased from 68.2 to 71.1 MPa. For concrete with W/C equal to 0.47 after 28 freeze/ thaw cycles, the mass loss of 3D-printed specimens reaches 2.09 and 56 freeze/thaw cycles 9.17 kg/m2 , and large surface defects were obtained. An analysis of the origin and recommendations for preventing cracks from occurring in 3D-printed products were carried out. The findings underscore the need for optimized mix designs and printing parameters to enhance durability.

Due to the demand for massive urbanization, more high‐rise buildings need to be constructed in major cities. The framed tube structural system can be an effective framing technique for this case. This system comprises tightly spaced peripheral columns connected by deep spandrel beams. Reinforced concrete structural walls provide substantial lateral strength and stiffness to limit damage when structures are subjected to ground shaking. In this paper, T‐shaped shear walls replace the peripheral columns to obtain better performance. The reduced cost of columns, walls, and beams of square‐shaped framed tube structures with peripheral T‐shaped walls compared to the column is in the range of 8%–18%. The shear lag factor for the ground floor of square‐shaped framed tube structures is also reduced from 4% to 56% for different structural configurations. The concrete quantity of columns, walls, and beams of square‐shaped framed tube structures with peripheral T‐walls is reduced by 6%–19%. The longitudinal reinforcement quantity of columns, walls, and beams is also reduced by 12%–25%. The reaction force for the foundation design of square‐shaped framed tube structures with peripheral T‐shaped walls lies between 2% and 11% less than the square‐shaped framed tube structures with peripheral columns. The seismic performance level of buildings with peripheral T‐walls is immediate occupancy (IO) for the hazard level corresponding to service level earthquake (SLE), design basis earthquake (DBE), and maximum considered earthquake (MCE), while IO to life safety (LS) for the buildings having peripheral columns. The plastic hinge formation of considered buildings with peripheral columns is 1%–5%, 2%–7%, and 7%–12%, SLE, DBE, and MCE, respectively, while the buildings with peripheral T‐walls are insignificant. The drift ratio of buildings with peripheral walls is less than that of those with peripheral columns.

The Bhairab River, characterized by its regular flow and bidaily tidal cycles, is vital to the Khulna region. The River’s water quality is significantly influenced by tidal and seasonal changes. Therefore, comprehensive studies appraising these variations are critically important to fully understand the river’s water dynamics. This research aimed to evaluate the impacts of tidal and seasonal variations on the water quality of the Bhairab River over 1 year. Water samples were collected weekly and hourly from three selected study sites along the river, and physicochemical parameters were analyzed through laboratory testing. The monitored water quality data were analyzed using cluster analysis (CA) and principal component analysis (PCA). Four distinct clusters represent different seasons: premonsoon (PM), postwinter (PW), monsoon (M), and early monsoon and winter (EMW) were identified through CA analysis. The study observed the highest levels of total solids (TS) (13,625–15,950 mg/L), total dissolved solids (TDS) (13,663–14,249 mg/L), chloride (Cl−) (salinity) (6631–7377 mg/L), and electrical conductivity (EC) (8.1–8.6 mS/cm) during the PM period. These concentrations significantly decreased during other periods, reaching their lowest during the monsoon season: TS (800–852 mg/L), TDS (187–193 mg/L), Cl− (32–33 mg/L), and EC (0.33 mS/cm). In contrast, suspended solids (SS) (658–1432 mg/L) and turbidity (320–360 NTU) peaked during the monsoon period and were lower during the PM and PW periods (221–450 mg/L and 120–290 NTU, respectively). PCA highlighted the intrusion of dissolved salts during the PM period, while organic pollutants and SS increased during the early monsoon and monsoon periods. Analysis of 24-h data revealed that TDS and SS levels increased during tidal events and decreased during ebb events. Tide and ebb conditions did not significantly impact dissolved oxygen (DO), Cl−, and conductivity. The comprehensive assessment of water quality variation in the Bhairab River conducted in this study is crucial for ensuring sustainable management of this vital freshwater resource for Khulna, the third largest city in Bangladesh.

The "carbon balance" theory is introduced into the investigation on carbon emission throughout the recycled coarse aggregate concrete's life cycle. It is aimed to study the carbon sink effect on the operation concrete stage, reveal the carbon balance of the recycled coarse aggregate concrete in its life cycle, and design low-carbon concrete based on concrete performance and environmental impact. Considering the carbon adsorption effect, the recycled coarse aggregate concrete's life cycle can be divided into four stages. In addition, the calculation model for carbon emission is constructed to estimate the carbon emission throughout the recycled coarse aggregate concrete's life cycle. The results concluded that the carbon emission was mainly concentrated in the production and transportation stages of concrete composition raw materials, and the carbon sequestration effect through the concrete operation stage cannot be ignored. The carbon sequestration effect obviously increased with the strength grade of the recycled coarse aggregate concrete and the replacement rate of the recycled coarse aggregate increasing. The transportation distance of coarse aggregate in concrete composition materials is the most sensitive factor to the effect of carbon emission on the recycled coarse aggregate concrete. Compared with the ordinary concrete, the recycled coarse aggregate concrete has significant carbon reduction advantages, with 1 m 3 of the recycled coarse aggregate concrete reducing carbon emissions by 70-100 kg. The research findings also provided empirical reference for the government to reduce carbon management on the construction sector from the perspective of carbon balance.

The flatness and damage zone of the tunnel excavation contour is critical to the safety and economy of the project. Considering the seriousness of over-under-excavation and the difficulty of contour formation in the blasting excavation of joint-developing rock mass tunnels, a numerical model was first established by combining compression-shear and tensile-shear failure criterion. Then the analysis of the near-zone stress field distribution and the crack evolution path of the blasthole under different joint characteristics was carried out. Results reveal that the inclination, thickness, and strength of the joints have a significant effect on the crack evolution between the blastholes. The over-under-excavation was most severe when the angle between the joint and blasthole was 45°, while the effect was minimal when the angle was 0° or 90°. The weaker the joint strength and the greater the width, the stronger the blocking effect and the tensile failure effect on the blasting stress wave. Finally, combined with a major engineering example, the smooth blasting scheme of the jointed rock tunnel was optimized and successfully verified. Based on the influence mechanism of joint characteristics, the contour blasting parameters and the technology of large jump delayed initiation and peripheral guiding empty hole were proposed, which significantly improved the smooth effect of the contour surface of the jointed rock mass tunnel.

This study investigates the potential use of geosynthetic materials as capillary barriers to enhance water retention in landscaping soils. The soil was first classified using the Unified Soil Classification System (USCS); then, the Van Genuchten model was used to model and compare the unsaturated hydraulic characteristics of the soil and geosynthetic materials. Five different materials; gravel, sand, needle punched 50 (NP 50) geotextile, thermally bonded (TB) 9 and (TB) 21 geotextiles were used together with silty clay to create capillary barriers in five different 500 mm deep soil columns to determine how each of the materials influences the amount of water stored. Water infiltrated into each of the columns constructed as capacitive moisture sensors tracked changes in moisture content in the soil. The air entry pressure and residual matric suction for the materials were determined from soil water retention curves (SWRCs) and compared to water content retained in each column. This study concluded that a properly designed capillary barrier can increase water retention in landscape soils. It was also demonstrated that materials with the higher residual matric suction (NP 50 and sand) stored more water than those with the least (TB 21 and TB 9).

The reliable synergy between steel and concrete is an important evaluation criterion for the safety and long-term use of steel–concrete composite structures (SCCSs). However, it is still a great challenge to realize fast and automated interface void detection for composite structures such as towers. Therefore, the experiments of void detection of the bridge tower full-scale model were carried out with the background of Zhang Jinggao Yangtze River Bridge and other composite structure bridge towers. An automated inspection robotic device was developed, and a convolutional neural network (CNN) identification and classification model based on excitation vibration acoustic signals for the detection of void damage was proposed. In addition, the applicability of the response characteristics of the acoustic signal to the model and the visualization of the features were discussed. Developed tracked magnetic inspection robots can be applied to a variety of towering and complex confined areas, with real-time inspection efficiency as high as 0.1 m²/s. The method based on excitation vibration acoustic signal analysis can be used as a new method for the detection of void damage in composite structures dependent on automatic inspection devices. The introduction of Mel spectrum features into the analysis of excitation vibration acoustic signals can improve the accuracy of identifying structural void damage. Compared with the conventional MLP and LSTM neural network models, the constructed Mel Spectrum with CNN model can realize high-precision classification of damage, health, and invalid data of the composite structural interface, and the classification and recognition accuracy reaches 96.8%. The equipment and method can realize the accurate and fast detection of the interface void of the towering composite structure. It improves the automation of the void detection process and reduces the safety risk of the detection.

To study the mechanical properties of the lifting anchor under combined tension and shear, the failure mode and bearing capacity of lifting anchor under different load angles are systematically analyze through the comparison of test and finite element numerical simulation results. Firstly, 16 concrete specimens with embedded lifting anchor were subjected to testing at eight different load angles. Then the finite element software Abaqus was utilized to simulate the specimens, and the obtained results were compared with the experimental data to verify the accuracy of the finite element simulation of the mechanical properties of the lifting anchor under combined tension and shear, which provides a basis for the stress analysis of the complex lifting state in the future. The results show that with the increase of load angle, the ultimate bearing capacity and tensile–shear coupling stiffness of the lifting anchor increase gradually. The ultimate combined load of the specimen increased by about 41% from 0° to 90°. The mathematical statistics method was applied to fit the test data, and the calculation formula of the load-bearing capacity of the lifting anchor under the combined action of tension and shear is established. The average R-squared value of the calculation formula is 0.95, which is in good agreement with the experimental data and improves the design and evaluation accuracy of this type of structure.

In recent years, there have been several instances of building collapse incidents resulting from shear failure. The complicated stress state and extremely nonlinear behavior seen in RC structures under shear loading are responsible for this phenomenon. Scholars and engineers worldwide have yet to propose a suitable model to address the issue correctly. Most computational approaches currently in use rely on semi-empirical and semi-theoretical formulations. The primary modes of shear transmission in cracked reinforced concrete include shear stress inside the uncracked concrete region, aggregate interlock, dowel action, stirrup action, and tensile residual stress. The shear force calculation is contingent upon the choice of the shear transfer model. This study comprehensively overviews the current shear calculation techniques and their respective applications. The pros and cons of these techniques were thoroughly examined. The present study investigated the suitability of these shear calculation formulas for RC structures subjected to intricate natural conditions, mechanical stress, and high-strength and high-performance concrete structures.

Understanding the interface shear behavior between clay and structures is crucial in geotechnical engineering. The mechanism of the roughness effect in the shear process between the clay and structures was studied to reveal the macroscopic and microscopic interface shear behavior. The different surface protrusion shapes of the structures were produced using a three-dimensional (3D) printer. Direct shear tests were conducted to analyze the shear failure modes and peak and residual strengths under different conditions. Subsequently, a discrete element method (DEM) numerical analysis was employed to study the contact network, soil fabric evolution, shear zone, coordination number, and void ratio variations in the interface shear. The test results indicated that the shear interfaces exhibited the same failure mode under various conditions, and the peak and residual strengths showed a strong positive correlation with roughness. The results obtained from numerical calculations match the experimental findings. The contact orientations and principal stresses shifted during the shear process, and the shear zone, coordination number, and void ratio also showed regular changes with the change of roughness. The evolution of microscopic parameters in DEM can effectively help explain the macroscopic interface shear behavior.

Limestone or river aggregates have been traditionally used as aggregates in ready-mixed concrete from the past to the present. The depletion of these natural aggregates used in ready-mixed concrete has led the concrete industry to investigate aggregate resources and search for alternative aggregates. In this study, natural rocks defined as basalt type from Karacadağ, located within the borders of Diyarbakır, Şanlıurfa, and Mardin provinces in the Southeastern Anatolia Region of Türkiye, were used as aggregate materials. The mechanical strength of concrete produced with basalt aggregate was examined. In order to determine the physical and mechanical properties of the produced basalt aggregate concretes, unit weight, compressive strength, and splitting tensile strength experiments were carried out on hardened concretes. In addition to the physical and mechanical properties of basalts, their chemical composition properties have been investigated. In the experimental study, crushed basalt aggregates with size fractions 0–5, 5–11.2, and 11.2–22.4 mm were used. The water/cement ratio of the concrete produced in the study was 0.45, and the selected cement contents were determined as 300 kg/m³, 350, and 400 kg/m³. The fracture parameters of the produced concrete were presented with the two-parameter fracture model (TPFM). Statistical analyses of this study show that the fracture parameters of cube samples made with basalt aggregate commonly found in the region are acceptable for use in construction sites.

When many repetitions of an expensive or time-consuming analysis are needed, simplified models are usually adopted to reduce the cost. This is often the case with gravity dams under seismic load, especially if geometry variation needs to be considered. Deterministic analysis of dams is an important part of preliminary analyses but generally leads to overconservative designs. In recent years, many researchers have studied the potential of machine learning techniques to reduce the computational burden of dam assessment. However, generating the training dataset for a surrogate model based on high-fidelity (HF) data can be expensive when a large set of uncertain parameters is considered. To address this issue, this study proposes the use of multifidelity surrogate (MFS) models. In this method, datasets with different levels of fidelity are combined to generate a highly accurate surrogate model at a lower cost. To illustrate this, the seismic behavior of a gravity dam is assessed by means of a HF nonlinear finite element model that considers geometric, material, and seismic uncertainties. In addition, five lower fidelity (LF) models are combined with HF samples to generate multifidelity models. The goodness of fit of the models and the computational time to produce the dataset are used to identify the combination that optimizes the MFS model performance. The results show that including medium- or low-fidelity samples improves the predictive performance of a surrogate model and reduces its computational burden. The results also show that the data generation and the selection of the best LF model depend on the size of the HF dataset.

The study investigates the seismic response of long-span single-tower and single-cable steel truss girder cable-stayed bridges, which structurally differ from traditional bridge types, and there is limited research on the influence of cable arrangement on the seismic response of long-span single-tower steel truss girder cable-stayed bridges. Therefore, based on the engineering background of the world’s largest span single-tower and single-cable steel truss girder cable-stayed bridge, a finite element model of the entire bridge is established to study the effect of cable arrangement on the seismic response of the bridge. The results indicate that although a double-cable plane arrangement can slightly reduce the torsion of the main girder, it cannot completely eliminate the occurrence of torsional vibration modes. However, by employing structural measures such as sufficient stiffness and reasonable width of the steel truss girder, the negative impact of single-cable plane arrangement on the dynamic characteristics of the bridge can be mitigated. It is suggested to adopt a single-cable plane arrangement when the standard width of the main girder is narrow, while a double-cable plane arrangement is more suitable when the standard width of the main girder is wide. These findings provide an important reference for the design of similar structures in the future.

The academic community has paid much attention to the research topic of structural health monitoring (SHM) and damage identification for several decades, which flourishes the development of diverse damage identification approaches. The sensitivity-based damage identification enjoys popularity due to its clear physical meaning and long development history. However, this type of method faces challenges of fewer applications on the large-scale structure, slow convergence rate, and poor performance based on the sensitivity of the modal parameters. Aiming at the existing obstacles, this study enables to propose a novel method based on time series analysis model and improved sparse regularization technique for damage identification of the large-scale structure. Firstly, the model reduction technique is introduced to condense the unconcerned degrees of freedom (DOFs) of the finite element model (FEM) of the large-scale structure, and then the sensitivity of the autoregression (AR) coefficient with respect to the damage coefficient for the large-scale structure has been deduced, which can reduce the uncertainty, which comes from modal identification, in modal parameter sensitivity. Furthermore, the mean-value normalization strategy is incorporated into the sparse regularization solving process to improve the computational efficiency. The proposed method has been validated based on a numerical continuous rigid frame bridge and an experimental steel truss bridge. Compared to the moth-flame optimization (MFO) algorithm and traditional regularization methods, for both noise-free and noise polluted data, the iteration curves illustrate that the proposed method can achieve convergence within about 200 iterations, while the MFO algorithm is always trapped into local optima; meanwhile, the traditional regularization method needs more iterations or even cannot meet the preset tolerance. Furthermore, regarding the numerical example, the damage identification results show that the max identification errors of the proposed method are 6% among the three cases under noise-free and noise-polluted data, while the max identification errors for MFO and the regularization method are 15% and 10%, respectively. And for the experimental example, based on the limited sensors, the proposed method can accurately detect the damage location and quantify damage severity with a good accuracy, which means this method has good potential for actual engineering structure. To summarize, the findings highlight that the AR coefficient sensitivity combined with improve sparse regularization can effectively detect damage of large-scale structure, providing a feasible way to expand the application of the sensitivity-based method.

The composite cross arm tower exhibits excellent electrical performance, which contributes to a reduction in the width of transmission line corridors, minimizes the use of steel in transmission towers, and mitigates issues such as wind bias tripping. This functionality supports the low-carbon design of overhead transmission lines, emphasizing the importance of quality and efficiency. However, the elimination of the suspension insulator string in composite cross arm linear towers leads to significant longitudinal unbalanced tension during adverse conditions such as conductor line breaks or ice accumulation. This excessive force can cause local damage or even collapse of the tower due to overstressing of the diagonal members. To address this challenge, we propose a new composite cross arm structure incorporating a C-shaped rotating device designed to alleviate unbalanced tension in composite cross arm towers. The mechanical performance of this structure was assessed through both full-scale tests and finite element simulations, confirming that the structure operates within an elastic range. The rotation axis was identified as the weakest point, with stress peaks remaining significantly below the yield strength, thereby indicating a high level of safety and a considerable safety margin. The C-shaped rotating device features a 380 mm range of motion and effectively releases unbalanced tension during actual line operations. Overall, the new composite cross arm structure with the C-shaped rotating device demonstrates favorable mechanical properties.

Several studies from the Strategic Highway Research Program (SHRP) have demonstrated that improving asphalt binder standards by incorporating performance-based characteristics can benefit road network administrators. This approach provides a better understanding of pavement behavior during its operational phase. Despite these findings, Ethiopia’s current asphalt binder procurement process still relies on the penetration grading system, which uses a 25°C test temperature with a 100-g loading weight. This method fails to simulate the extreme temperature and loading conditions that pavements experience. Additionally, the empirical parameters derived from this test do not fully capture the stress–strain relationships of pavement performance. This research introduces the performance grading (PG) system, a key component of SHRP’s developments, with two main objectives: (1) to develop a PG map for Ethiopia and (2) to evaluate asphalt binder performance using PG testing standards. Achieving these objectives requires two different approaches. First, the PG map was developed using 20 years of air temperature data from the National Meteorological Agency. The SHRP prediction model was applied to convert air temperature to pavement temperature, yielding a PG classification with 98% reliability. The second objective involved performing conventional and Superpave binder tests on asphalt samples collected from various ongoing projects. The PG determination test provided a generic binder classification, while the multiple stress creep recovery (MSCR) tests delivered more detailed performance data, including traffic loading capacity and maximum temperature tolerance. The results identified five major PG-grade temperature zones in Ethiopia, with PG 58-10 and PG 64-10 dominating. While the asphalt binders are suitable for most regions, projects in eastern and western Ethiopia (PG 76-10 and PG 70-10) may experience excessive rutting with current binders usage (60/70 and 40/50).

The sand crisis has received growing attention in recent years, and a number of substitutes have been examined by researchers in order to reduce the use of river sand. Typical substitutes are industrial by-products that would otherwise require land for waste disposal. Steel slag (SS) is one such by-product that can be used as a replacement for alluvial sand in concrete. A comprehensive review of the effects of sand replacement by SS on physical, mechanical, and durability properties of concrete is presented in this study. The primary objectives of this study are to (1) evaluate the impact of varying proportions of SS as a sand substitute on the mechanical and durability properties of concrete, (2) identify the optimal percentage of SS replacement to achieve enhanced performance, and (3) address the existing knowledge gap regarding the sustainability of using SS in concrete applications. A systematic review of the available data revealed the promising application of SS as sand replacement in concrete with enhanced concrete strength and durability. Considering all aspects of concrete applications, the optimum level of SS replacement is reported in a range from 30% to 60%, meeting concrete’s physical, mechanical, and durability expectations. The findings also show further research is needed to determine the durability of SS concrete (SSC) for different intended applications.

Coal mine roof accident is one of the most important geological disasters faced by coal mine, and roof displacement is an important index to measure the effect of roadway control and construction safety. Therefore, this study puts forward the machine learning method to study the advance prediction of coal roadway roof displacement. By identifying six important influencing indexes of coal roadway roof displacement, the prediction dataset of coal roadway roof displacement is established and the correlation and importance of the indexes are analyzed. Based on Random Forest (RF), XGBoost, and Gradient Boosting Decision Tree (GBDT) algorithms, three kinds of roof displacement prediction models are established respectively. R², mean absolute error (MAE), mean square error (MSE), mean absolute percentage error (MAPE), and root mean square error (RMSE) are selected to evaluate the performance of the models. The results show that the RF model has the best performance while the XGBoost model has the worst performance. When RF model is applied to coal mine roadway, the average R² is 0.92, and the relative error of prediction is 1.76%–9.11%, which indicates that RF model has greater accuracy and applicability in advance prediction of coal roadway roof displacement. It can be used to predict the roof accidents of coal mines to ensure the safety and stability of the roadway enclosure rock during the construction period. The study will be helpful in planning of mining, improving the recovery rate of resources, and promoting the intelligent development of coal mine.

The groundwater extraction will lead to a drop in water level, causing a change in the distribution of additional stress in the strata. This phenomenon leads to uneven settlement of the railway subgrade. In severe cases, this could threaten the safe operation of trains. Therefore, the degree and main factors influencing groundwater extraction in the settlement of the railway subgrade need to be determined through research. Based on railway subgrade engineering, the first step involved monitoring the settlement resulting from groundwater extraction during the spring irrigation period. Following this, the settlement characteristics of the subgrade structure were analysed. Subsequently, based on the Biot consolidation theory of the soil, a numerical simulation model was established to study the threshold parameters of the groundwater extraction on site. Finally, the primary and secondary relationships of the influencing factors must be clarified. The research results show that: (1) According to the monitoring data, groundwater extraction resulted in a subgrade subsidence of 15.2 mm, exceeding the prescribed threshold, affecting the engineering quality. (2) By the numerical simulation results, the distance parameter of the wells is the most significant factor affecting the deformation of the subgrade, followed by the quantity of extraction. So, the distance between the wells and the tracks should be kept at more than 150 m; the pumping volume should not exceed 1500 m³/day. (3) Using horizontal jet grouting piles to reinforce the subgrade can reduce the maximum uneven deformation from 18.14 to 7.86 mm, an effective settlement control measure.