Search Results (9,004)

Weaknesses generated in asphalt pavement structures have a serious impact on the service life of pavements. In order to improve such situations and achieve the goal of enhancing the durability of the pavement structure, this study assesses the performance of heavy-duty asphalt and high-viscosity asphalt, using four high-performance asphalt mixtures: heavy-duty AC-20, high-viscosity AC-20, heavy-duty SMA-13, and heavy-duty SMA-10. Three composite pavement structures were designed: 3 cm SMA-10 + 3 cm SMA-10, 4 cm SMA-13 + 4 cm SMA-10, and 6 cm SMA-13 + 4 cm AC-20. Interlayer performance analysis was conducted on single-layer and composite structures through oblique shear tests; dynamic modulus, fatigue life, and antirutting performance tests on asphalt pavement structural layers were designed and conducted, and the durability performance of high-performance asphalt pavement structural layers was evaluated. The experimental results show that the shear strength of heavy-duty AC is higher than that of heavy-duty SMA, the 4 + 4 combination structure has the best shear strength, the 6 + 4 combination structure has the best structural performance and fatigue resistance, and the 3 + 3 combination structure has the best high-temperature antirutting performance. The comprehensive performance of the 4 + 4 structure is the best among the three combined structures, followed by that of the 6 + 4 structure, and the performance of the 3 + 3 structure is the worst. In addition, this study used bonding energy as an evaluation index and verified the applicability of the bonding energy evaluation index by studying four types of single-layer pavement structures and three types of composite pavement structures. Full article

PVC pipe jacking is prone to cause yielding or buckling under the jacking force and may lead to engineering failure. The relationship between the buckling modes, ultimate bearing capacity, different diameter–thickness ratios, and length–diameter ratios of PVC pipe jacking under different load forms was analyzed. The calculation methods for allowable jacking force and the single allowable jacking distance are obtained through theoretical analysis and three-dimensional finite elements. The buckling mode of the pipe under uniform load changes from symmetric buckling to asymmetric buckling and then to the overall Euler buckling form as the length–diameter ratio increases. The ultimate bearing capacity of the pipe approaches the theoretical value of yield failure when L/D $\le$ 6. For L/D $>$ 6, the pipe undergoes buckling, and the ultimate bearing capacity determined by the axial buckling value and the buckling load can be calculated according to the long pipe theory formula when L/D $>$ 8.5. Under eccentric loads, the failure mode transitions from local failure to Euler buckling with increasing pipe length. The ultimate bearing capacity of pipe is obviously lower than that of uniform load, but as the length–diameter ratio increases, this difference decreases until it becomes consistent. Full article

With rapid urbanization, many cities have experienced significant changes in land use and land cover (LULC), triggered urban heat islands (UHI), and increased the health risks of citizens’ exposure to UHI. Some studies have recognized residents’ inequitable exposure to UHI intensity. However, few have discussed the spatiotemporal heterogeneity in environmental justice and countermeasures for mitigating the inequalities. This study proposed a novel framework that integrates the population-weighted exposure model for assessing adjusted thermal comfort exposure (TCEa) and the spatiotemporal weighted regression (STWR) model for analyzing countermeasures. This framework can facilitate capturing the spatiotemporal heterogeneities in the response of TCEa to three specified land-surface and built-environment parameters (i.e., enhanced vegetation index (EVI), normalized difference built-up index (NDBI), and modified normalized difference water index (MNDWI)). Using this framework, we conducted an empirical study in the urban area of Fuzhou, China. Results showed that high TCEa was mainly concentrated in locations with dense populations and industrial regions. Although the TCEa’s responses to various land-surface and built-environment parameters differed at locations over time, the TCEa illustrated overall negative correlations with EVI and MNDWI while positive correlations with NDBI. Many exciting spatial details can be detected from the generated coefficient surfaces: (1) The influences of NDBI on TCEa may be magnified, especially in rapidly urbanizing areas. Still, they diminish to some extent, which may be related to the reduction in building construction activities caused by the COVID-19 epidemic and the gradual improvement of urbanization. (2) The influences of EVI on TCEa decline, which may be correlated with the population increase. (3) Compared with NDBI, the MNDWI had more continuous and stable significant cooling effects on TCEa. Several mitigation strategies based on the spatiotemporal heterogeneous relationships also emanated. The effectiveness of the presented framework was verified. It can help analysts effectively evaluate local thermal comfort exposure inequality and prompt timely mitigation efforts. Full article

Surface scattering greatly impacts and improves the acoustic quality of an auditorium, affecting properties such as the reverberation time, early decay time, definition, and sound strength. However, this aspect has not been sufficiently investigated to date. In this study, six completed auditoriums are taken as research samples and computer simulations are performed to analyze the variation patterns in the acoustic-quality parameters as functions of increments in the surface scattering coefficients. The results show that the reverberation time and early decay time change marginally (<5%) when the ceiling scattering coefficient increases from 0.01 to 0.99. When the sidewall scattering coefficient increases, the reverberation time and early decay time shorten, and the variation range expands (5–16.7%). In most cases, the definition and sound strength do not significantly change (<0.05 and 1.0 dB). A balcony on the auditorium sidewall can affect the reverberation time-change curve when the sidewall scattering coefficient changes. Changes in the ceiling and sidewall scattering coefficients affect the reflected sound-energy distribution along the time axis differently. Sidewall scattering has a significantly greater impact on the impulse response than ceiling scattering. The findings of this study provide theoretical guidance for the scattering design of the surface of theater auditoriums. Full article

Generally speaking, the traditional lever amplification damping system is installed between adjacent columns in a building, which occupies a significant amount of space in the building. In contrast to amplification devices in different forms, the damper displacement of the intermediate column damper system is smaller, and the vibration reduction efficiency is lower. In light of these drawbacks, this study proposes a new amplification device for energy dissipation and vibration reduction, which is based on an intermediate column–lever mechanism with a viscous damper (CLVD). Initially, a specific simplified mechanical model of CLVD is derived. Subsequently, an equivalent Kelvin mechanical model of CLVD is derived to intuitively reflect CLVD’s damping and stiffness effect. The damping ratio added by CLVDs to the structure is calculated according to that model; the additional damping ratio and additional stiffness are utilized to calculate the displacement ratio R_d and shear force ratio R_vof the structure with CLVDs to the structure without CLVDs. R_d and R_v are introduced to evaluate the vibration reduction effect of the structure with CLVDs, and the effects of various parameters (such as intermediate column position, beam’s bending line stiffness, lever amplification factor, damping coefficient, and earthquake intensity) on R_d and R_v are analyzed. The results indicate that when the ratio of the distance from the intermediate column to the edge column to the span of the beam is 0.5, CLVD owns the optimal vibration reduction effect. Increasing the beam’s bending line stiffness is beneficial for CLVD to control structural displacement and shear force ; when the leverage amplification factor is too large, the CLVD provides the structure with stiffness as the main factor, followed by damping. Additionally, when the ratio of the displacement amplification factor to the geometric amplification factor satisfies f_d/γ = 1/2^1−0.5α, the CLVD has the optimal displacement control effect on the structure. After that, measures are provided to optimize the CLVD in different situations in order to effectively control the inter-story displacement and the story shear force of the structure. Consequently, a nine-story frame is taken as an example to elaborate the application of CLVDs in the design for energy dissipation and vibration reduction. The results reveal that the CLVD scheme adopting the proposed optimization method can effectively enhance the displacement amplification ability of CLVDs, resulting in an additional damping ratio of up to 12%. At the same time, the inter-story displacement was reduced by almost 40% under fortification earthquakes. Through the research in this study, designers can obtain a new choice in structural vibration reduction design. Full article

Chloride corrosion is a key factor affecting the life of marine concrete, and surface chloride concentration is the main parameter for analyzing its durability. In this paper, we first introduce six erosion mechanism models for surface chloride ion concentration, reveal the convection effect in the diffusion behavior of chloride ions, and then introduce the corrosion mechanisms that occur in different marine exposure environments. On this basis, the analysis is carried out using empirical formulations and machine learning methods, which provides a clearer understanding of the research characteristics and differences between empirical formulas and emerging machine learning techniques. This paper summarizes the time-varying model and multifactor coupling model on the basis of empirical analysis. It is found that the exponential function and the reciprocal function are more consistent with the distribution law of chloride ion concentration, the multifactor model containing the time-varying law is the most effective, and the Chen model is the most reliable. Machine learning, as an emerging method, has been widely used in concrete durability research. It can make up for the shortcomings of the empirical formula method and solve the multifactor coupling problem of surface chloride ion concentration with strong prediction ability. In addition, the difficulty of data acquisition is also a major problem that restricts the development of machine learning and incorporating concrete maintenance conditions into machine learning is a future development direction. Through this study, researchers can systematically understand the characteristics and differences of different research methods and their respective models and choose appropriate techniques to explore the durability of concrete structures. Moreover, intelligent computing will certainly occupy an increasingly important position in marine concrete research. Full article

In the construction industry, the imperative for visual surveillance mechanisms is underscored by the need for safety monitoring, resources, and progress tracking, especially with the adoption of vision intelligence technology. Traditional camera installation plans often move toward coverage and cost objectives without considering substantial coverage overlap, inflating processing and storage requirements, and complicating subsequent analyses. To address these issues, this research proposes a voxel-based site coverage and overlapping analysis for camera allocation planning in parametric BIM environments, called the PBA approach. The first step is to collect information from the BIM model, which is the input for the parametric modeling step. After that, the PBA approach simulates the virtual devices and the construction layout by employing visual language programming and then generates a coverage area. Lastly, the performance simulation and evaluation of various placement scenarios against predefined criteria are conducted, including visual coverage and overlapping optimization for eliminating data redundancy purposes. The proposed approach is evaluated through its application to construction projects. The results from these various implementations indicate a marked decrease in data overlap and an overall enhancement in surveillance efficacy. This research contributes a novel, BIM-centric solution to visual information adoption in the construction industry, offering a scalable approach to optimize camera placement while mitigating overlapping areas. Full article

Construction safety requires real-time monitoring due to its hazardous nature. Existing vision-based monitoring systems classify each frame to identify safe or unsafe scenes, often triggering false alarms due to object misdetection or false detection, which reduces the overall monitoring system’s performance. To overcome this problem, this research introduces a safety monitoring system that leverages a novel temporal-analysis-based algorithm to reduce false alarms. The proposed system comprises three main modules: object detection, rule compliance, and temporal analysis. The system employs a coordination correlation technique to verify personal protective equipment (PPE), even with partially visible workers, overcoming a common monitoring challenge on job sites. The temporal-analysis module is the key component that evaluates multiple frames within a time window, triggering alarms when the hazard threshold is exceeded, thus reducing false alarms. The experimental results demonstrate 95% accuracy and an F1-score in scene classification, with a notable 2.03% average decrease in false alarms during real-time monitoring across five test videos. This study advances knowledge in safety monitoring by introducing and validating a temporal-analysis-based algorithm. This approach not only improves the reliability of safety-rule-compliance checks but also addresses challenges of misdetection and false alarms, thereby enhancing safety management protocols in hazardous environments. Full article

In the context of the escalating challenge of climate change, optimizing buildings’ energy performance has become a critical research area, yet studies specifically targeting library buildings are scarce. This study addresses this gap by investigating the impact of multi-objective optimization on energy efficiency and occupant comfort in educational library buildings under future climate scenarios. Utilizing the Non-Dominated Sorting Genetic Algorithm II (NSGA-II), this research optimizes a range of building parameters, including the cooling and heating setpoints, air change rates, shading device depths, window visible transmittance, and window gas types. The optimization aims to balance energy consumption and comfort, using simulations based on future weather data for the years 2020, 2050, and 2080. The results indicate that the optimized solutions can significantly reduce the heating energy by up to 95.34% and the cooling energy by up to 63.74% compared to the baseline models, while maintaining or improving the occupant comfort levels. This study highlights the necessity for dynamic, responsive architectural designs that can adapt to changing environmental conditions, ensuring both sustainability and occupant well-being. Furthermore, integrating these building-level optimizations into a City Information Model (CIM) framework can enhance urban planning and development, contributing to more resilient and energy-efficient cities. These findings underscore the importance of sustainable design practices in the context of climate change and the critical role of advanced optimization techniques in achieving energy-efficient, comfortable educational spaces. Full article

In South Korea, the configuration of land parcels within apartment complexes plays a pivotal role in optimizing land use and facility placement. Given the significant impact of land shape on architectural and urban planning outcomes, its analysis is essential. However, studies on land shape have been limited due to the lack of definitive survey criteria. To address these challenges, this study utilized a map application programming interface (API) to gather raw data on apartment complex layouts in South Korea and processed these images using a Python-based image library. An initial analysis involved categorizing the data through K-means clustering. Each cluster’s average image was classified into four distinct groups for comparison with the existing literature. Shape indices were employed to analyze land configurations and assess consistency across classes. These classes were annotated on a parcel level using the Roboflow API, and YOLOv8s-cls was developed to classify the parcels effectively. The evaluation of this model involved calculating accuracy, precision, recall, and F1-score from a confusion matrix. The results show a strong correlation between the identified and established classes, with the YOLO model achieving an accuracy of 86% and demonstrating robust prediction capabilities across classes. This confirms the effective typification of land shapes in the studied apartment complexes. This study introduces a methodology for analyzing parcel shapes through machine learning and deep learning. It asserts that this approach transcends the confines of South Korean apartment complexes, extending its applicability to architectural and urban design planning on a global scale. Analyzing land shapes earmarked for construction enables the formulation of diverse design strategies for building placement and external space arrangement. This highlights the potential for innovative design approaches in architectural and urban planning worldwide. Full article

Because of the flanges on T-shaped shear walls (TSSWs), the shear force acting on such walls results in a shear lag effect, making it impossible to forecast with accuracy the normal stresses of the flanges using the Bernoulli–Euler assumption. Shear lag (SL) in flanged walls has, however, received less attention from researchers, particularly in experimental studies. Understanding the SL in T-shaped reinforced concrete shear walls under shear and axial force is the main goal of this work. First, a SL model is suggested for TSSWs. In this model, the SL deflection is considered to be the generalized displacement and the SL warping deformation, and it is assumed to be a quadratic nonlinear function. Then, experimental and numerical simulation studies are, respectively, conducted to investigate SL effect of TSSWs, and also to evaluate the accuracy of the SL method. Finally, the parameter analysis is conducted to investigate the influence of axial load, shear force, and flange length on the SL effect of TSSWs. The results show that the SL of the TSSW is significant, the normal stress distribution (NSD) of the flange is uneven, and the normal stresses near the web are higher, according to the results of the analytical, simulated, and experimental results. The SL model can accurately predict the normal stresses of the flange of TSSWs, and the quadratic parabola assumption of the SL warp displacement of TSSWs is reasonable. Parameter analysis shows that axial force has little effect on the SL effect of TSSWs. The TSSWs under larger shear force have the more obvious SL effect. A more obvious SL effect occurs in the TSSWs with longer flanges. Full article

The porous nature of lightweight expanded clay aggregate (LECA) is decisive in the physical and mechanical properties of concrete. A comprehensive experimental study consisting of 13 different mixtures and 234 specimens was carried out on density, absorption capacity, porosity, compressive strength, splitting tensile strength, modulus of elasticity, and the effect of moisture state of LECA concrete. Dry compressive strengths of mixtures were found to be between 18–38 MPa, and 9% higher on average than moist compressive strength. Modulus of elasticity values decreased significantly when specimens were oven-dried, where the decrease was 26% on average. The study also includes an evaluation of modulus of elasticity prediction models. All prediction models consistently overestimated dry modulus of elasticity, which is problematic for structural applications of LECA concrete. A unique model for modulus of elasticity prediction was developed as part of the study and verified using independent data from literature for its accuracy. Full article

A shaking table test of a 1/60 scale cross-fault bridge model considering the effects of soil–bridge interactions was designed and implemented, in which the bridge model was placed in two individual soil boxes to simulate the bridge across a strike-slip fault. Three seismic ground motion time-histories with permanent displacements were selected as input excitations to investigate the influence of seismic ground motions with different frequency characteristics on the seismic response of the testing soil–bridge model. The one-side input method was used to simulate the seismic response of bridges across faults. The seismic responses of the soil and bridge in terms of acceleration, strain, and displacement were analyzed. The test results show that the one-side input method can simulate the seismic response of the main girder displacements well and the displacements and strains of piers and piles of the bridge structure spanning a fault. The strain responses at near-fault pile foundations are much larger than those farther away from the fault. Compared with other bridges, the cross-fault bridge is more prone to torsional and displacement responses during earthquakes. Surface fault rupture can lead to permanent inclination of the bridge piers, which should be paid more attention to in the practical engineering design of the bridges. Soil–bridge interactions can suppress the amplification effect of soil on ground motions. The test results can provide a reference for future research and the design of cross-fault bridges. Full article

Desert areas contain abundant desert sand (DS) resources, and high-volume recycling of DS resources as components of cement-based materials can achieve high-value applications. In this paper, DS was processed into desert sand powder (DSP) and replaced with cement in high volumes (20 wt.%–60 wt.%) to produce cement pastes. The mechanical properties, heat evolution, nanomechanical characteristics, microstructure, and economic and environmental impact of cement pastes were studied. The results show that adding 20 wt.% DSP increases the compressive strength of pastes and accelerates cement hydration, compared with the control group (0 wt.% DSP). Meanwhile, incorporating an appropriate amount of DSP (20 wt.%) effectively reduces porosity, increases the proportion of harmless and less harmful pores, and reduces the proportion of more harmful pores. From the perspective of nanoscopic properties, the addition of 20 wt.% DSP increases the C-S-H volume fraction, especially enhancing the transformation of low-density C-S-H to high-density C-S-H. Notably, the sample incorporating 60 wt.% DSP exhibits the lowest values for CI coefficients (13.02 kg/MPa·m³) and Cp coefficients (2.29 USD/MPa·m³), thereby validating the application of high-volume DSP feasibility in cement-based materials. Full article

This paper focuses on clarifying the heat transfer coefficient necessary for determining the indoor temperature distribution during night ventilation using floor-level windows. Measurements were used to identify the factors that influence the vertical temperature distribution within a room wherein phase-change materials (PCMs) were installed at the floor level. The investigation revealed a temperature differential ranging from 1 °C to a maximum of 3 °C between the floor and the center of the room, attributable to external climatic conditions (outdoor temperature and wind speed). This variation was found to depend on the degree of mixing of indoor air currents. This deviation was critical because it significantly affected the phase-change temperature of PCMs, thereby impacting their thermal storage capabilities. Consequently, this study aimed to refine the predictive accuracy of indoor temperature distributions by proposing a modified vertical temperature distribution model that incorporated these findings. The results of this study are expected to provide better design strategies for building constructions that incorporate PCMs, and to optimize their functionality in passive cooling systems. Full article