Search Results (17,842)

In the waterway construction projects of the upper reaches of the Yangtze River, crushed mudstone particles are widely used to backfill the foundations of rock-socketed concrete-filled steel tube (RSCFST) piles, a structure widely adopted in port constructions. In these projects, the steel–mudstone interfaces experience complex loading conditions, and the surface profile tends to vary within certain ranges during construction and operation. The changes in boundary conditions and material profile significantly impact the bearing performance of these piles when subjected to cyclic loads, such as ship impacts, water level fluctuations, and wave-induced loads. Therefore, it is necessary to investigate the shear characteristics of the RSCFST pile–soil interface under cyclic vertical loading, particularly in relation to varying deformation levels in the steel casing’s outer profile. In this study, a series of cyclic direct shear tests are carried out to investigate the influential mechanisms of roughness on the cyclic behavior of RSCFST pile–soil interfaces. The impacts of roughness on shear stress, shear stiffness, damping ratio, normal stress, and particle breakage ratio are discussed separately and can be summarized as follows: (1) During the initial phase of cyclic shearing, increased roughness correlates with higher interfacial shear strength and anisotropy, but also exacerbates interfacial particle breakage. Consequently, the sample undergoes more significant shear contraction, leading to reduced interfacial shear strength and anisotropy in the later stages. (2) The damping ratio of the rough interface exhibits an initial increase followed by a decrease, while the smooth interface demonstrates the exact opposite trend. The variation in damping ratio characteristics corresponds to the transition from soil–structure to soil–soil interfacial shearing. (3) Shear contraction is more pronounced in rough interface samples compared to the smooth interface, indicating that particle breakage has a greater impact on soil shear contraction compared to densification. Full article

Building energy conservation and emission reduction are crucial in addressing global climate change. High-performance insulated building envelopes can significantly reduce energy consumption over a building’s lifecycle. However, few studies have systematically analyzed carbon reduction potential through a life cycle assessment (LCA), incorporating case studies and regional differences. To address this, this study establishes an LCA carbon emission calculation model using Building Information Modeling (BIM) technology and the carbon emission coefficient method. We examined four residential buildings in China’s cold regions and hot summer–cold winter regions, utilizing prefabricated concrete sandwich insulation exterior walls (PCSB) and autoclaved aerated concrete block self-insulating exterior walls (AACB). Results indicate that emissions during the operational phase account for 75% of total lifecycle emissions, with heating, ventilation, and air conditioning systems contributing over 50%. Compared to AACB, PCSB reduces lifecycle carbon emissions by 18.54% and by 20.02% in hot summer–cold winter regions. The findings demonstrate that PCSB offers significant energy-saving and emission-reduction benefits during the construction and operation phases. However, it exhibits higher energy consumption during the materialization and demolition phases. This study provides a practical LCA carbon calculation framework that offers insights into reducing lifecycle carbon emissions, thereby guiding sustainable building design. Full article

Rigid particle models (PMs) that explicitly consider the influence of the aggregate structure and its physical interaction mechanisms have been used to predict cracking phenomena in concrete. PMs have also been applied to reinforced concrete fracture, but the known studies have adopted simplified reinforcement and reinforcement/particle interaction models. In this work, a novel 3D explicit discrete element formulation of reinforcement bars discretized through several rigid cylindrical segments is proposed, allowing the 3D reinforced particle model (3D-RPM) to be applied to reinforced concrete fracture studies, namely for shear failure. The 3D-RPM is evaluated using known three-point and four-point bending tests on reinforced concrete beams without stirrups and on known shear transfer tests due to dowel action. The 3D-RPM model is shown to reproduce the crack propagation, and the load displacement response observed experimentally for different steel contents under three-point bending, for different beam sizes, under four-point bending, and for different bar diameters, under shear. The validation examples highlight the importance of including a nonlinear reinforcement/particle interaction model. As shown, an elastic model contact leads to higher vertical loads in three-point and four-point bending tests for the same set of contact properties and, in the shear tests, leads to an overestimation of the maximum shear strength and to an increase in the model initial stiffness. Full article

Although previous research has examined the mechanical properties of concrete exposed to high temperatures, further investigation is needed into the effects of post-fire curing on the recovery of strength and stiffness of sustainable concretes produced with slag-modified cement. This study conducted an experimental analysis of the residual compressive strength and modulus of elasticity of different types of concrete (20 MPa or 30 MPa) exposed to varying maximum temperature levels (200 °C, 400 °C, 600 °C, 800 °C) and post-fire treatments (with or without rehydration). The concrete specimens were produced using Portland cement CP II-E-32. The rehydration method involved one day of water curing, followed by 14 days of air curing. Statistical analyses revealed potential improvements in the mechanical properties of concretes produced with slag-modified cement due to rehydration processes after exposure to different temperatures levels. The highest values of the relative residual strength factor (Φ_c) were observed in specimens exposed to a maximum temperature of 600 °C, ranging from 0.862 to 0.905. The highest values of the relative residual elastic modulus factor (ψ_c) were verified for a maximum temperature of 200 °C, ranging from 0.720 to 0.778. The experimental results were compared with strength and stiffness predictions of design codes. The inclusion of slag in concrete reduced microcracking during the rehydration process due to the reduced amount of calcium hydroxide in the cementitious matrix, increasing the concrete’s relative residual strength and stiffness after post-fire curing. Full article

This article discusses the findings of an experimental study designed to investigate the cutting forces encountered during the milling of asphalt pavement, considering the influence of cutter teeth wear. Experimental research was carried out for different values of wear, considered as a change in the shape of the active part of the tooth and a reduction in its height. The aspects studied continue the previous research of the authors regarding the study of cutting forces when milling asphalt pavement, using new milling teeth (without wear). Through this new study, the authors want to highlight how the phenomenon of wear influences the mechanical conditions of the chipping process and the efficiency of asphalt pavement processing. The experimental research was performed using an original stand, designed by the authors of the article, equipped with instruments for recording the values of the cutting force in the direction of advance. The experimental part is completed by the numerical modeling using the discrete element method (DEM). Research has shown that the increase in cutting forces is more pronounced at low advanced speed. Increasing the advanced speed leads to a reduction in differences between the cutting forces corresponding to the use or not of the milling tooth wear compensation. The study’s findings offer valuable insights into how milling parameters influence cutting forces, providing a basis for optimizing asphalt pavement milling processes. Full article

Small-section steel-shell concrete immersed tube tunnels are intended for minibuses and have a low fire heat release rate. Standard fire rise curves do not apply to such tunnels. In this study, a coupled method of computational fluid dynamics (CFD) and the finite element method (FEM) was used to simulate the structural temperature distribution in tunnels. Firstly, a tunnel fire dynamics model was established to obtain the inhomogeneous temperature field during tunnel fires. Subsequently, a three-dimensional heat transfer analysis model for the tunnel tube section was established to simulate the temperature transfer characteristics of the tunnel structure with and without fire protection measures under different types of vehicle fires. This study showed that because steel has a higher thermal conductivity, at the same depth, the temperatures were the highest in T-ribs, followed by partitions, and the lowest in concrete; however, the steel components inside the tunnel minimally affected the tunnel temperature. Without fire protection, the steel shell’s surface temperature exceeded 300 °C in as little as 500 s. Temperature’s primary impact on the tunnel’s steel structure was within 30 cm of the steel shell’s surface, and on concrete, it was within 20 cm. The greatest temperature difference between the partition and concrete occurred 10 cm from the steel shell’s surface. These results fill the knowledge gap on heat transfer in these tunnels and have positive practical significance for the fire resistance design of tunnels. Full article

To thoroughly investigate the anchorage performance of a novel prefabricated concrete shear wall system assembled by anchoring closed-loop rebar, rebar pull-out tests were conducted. The effects of different rebar distribution forms, closed-loop rebar anchoring heights, and dowel rebar diameters on anchorage performance were considered. Strain measurements at key points were taken, and the failure modes and peak loads of shear walls with various closed-loop rebar assemblies were obtained. The results indicated that the rebars in all specimens fractured, with peak loads ranging from 90 kN to 100 kN, satisfying the anchorage requirements of the rebar. This demonstrates that even when the anchorage length of the rebar is less than specified, the method of assembling by anchoring closed-loop rebar can still provide good anchorage performance. Moreover, steel bars and concrete have different damage and failure characteristics under different load levels. This research also indicates that specimens with uniformly distributed closed-loop rebar exhibit superior anchorage performance compared to those with adjacent distribution. Furthermore, increasing the overlapping height of the closed-loop rebar contributed to enhancing the safety margin of the anchorage, while the diameter of the dowel rebar (similar to stirrups) had a relatively minor effect on the anchorage performance. These findings provide a scientific basis for the design and construction of prefabricated concrete shear walls with closed-loop rebar. Full article

Single-sided formwork supporting systems (SFSSs) play a crucial role in the urban construction of retaining walls using cast-in-place concrete. By supporting the formwork from one side, an SFSS can minimize its spatial footprint, enabling its closer placement to boundary lines without compromising structural integrity. However, existing SFSS designs struggle to achieve a balance between mechanical performance and lightweight construction. To address these limitations, an innovative instrumented SFSS was proposed. It is composed of a panel structure made of a panel, vertical braces, and cross braces and a supporting structure comprising an L-shaped frame, steel tubes, and anchor bolts. These components are conducive to modular manufacturing, lightweight installation, and convenient connections. To facilitate the optimal design of this instrumented SFSS, a physics-constrained generative adversarial network (PC-GAN) approach was proposed. This approach incorporates three objective functions: minimizing material usage, adhering to deformation criteria, and ensuring structural safety. An example application is presented to demonstrate the superiority of the instrumented SFSS and validate the proposed PC-GAN approach. The instrumented SFSS enables individual components to be easily and rapidly prefabricated, assembled, and disassembled, requiring only two workers for installation or removal without the need for additional hoisting equipment. The optimized instrumented SFSS, designed using the PC-GAN approach, achieves comparable deformation performance (from 2.49 mm to 2.48 mm in maxima) and slightly improved component stress levels (from 97 MPa to 115 MPa in maxima) while reducing the total weight by 20.85%, through optimizing panel thickness, the dimensions and spacings of vertical and lateral braces, and the spacings of steel tubes. This optimized design of the instrumented SFSS using PC-GAN shows better performance than the current scheme, combining significant weight reduction with enhanced mechanical efficiency. Full article

The conventional Trombe wall (TW) with concrete construction has been shown to enhance the indoor environment of buildings in cold and Mediterranean climates. Thus, a TW is an option for reducing energy consumption related to thermal comfort for buildings in the northwestern region of Mexico, characterized by arid and semi-arid conditions with low winter temperatures. The thermal behavior of the TW and a conventional facade (CF) of concrete were compared when installed in the southern wall of reduced-scale test boxes in Ensenada, B.C. Unlike other research works available in the literature, which typically monitored a data point measure of the wall and room temperatures, the present study measured the temperature of key components: the absorber wall, the air at the bottom and top vents, the glass cover, and the air at the cross-section plane of the TW test box. The results showed that the TW increases the air temperature through its channel up to 14 ∘C and yields a maximum thermal efficiency of 84% during a sunny winter week. Further, the indoor air temperature at the midpoint of the TW test module is up to 6 ∘C greater than the obtained on the CF-test module; therefore, the TW improved the thermal comfort conditions during winter. Full article

Reinforced concrete structures are susceptible to chloride ion attack under different conditions, such as water reservoirs, coastal regions, and industrial locations. The physical and mechanical properties of concrete are known to considerably affect the ion penetration velocity. However, studies addressing the effect of coatings on the chloride ion penetration of reinforced concrete are limited. Thus, the objective of this paper is to evaluate the effects of different surface coatings on chloride ion penetration in concrete elements. Acrylic, polyurethane, and epoxy resin coatings were applied in two layers as recommended by the manufacturers. Natural environment chloride ion exposure was conducted in loco in the city of Torres, Brazil, at two marine locations with different geographical characteristics and distances from the sea. In addition, laboratory tests consisting of salt spray and penetration-by-immersion tests were conducted. The concrete's characteristics, including its compressive strength, water absorption, and void index, were evaluated. The results indicate higher efficiency with the polyurethane coating, while the acrylic resin had the worst results, with a difference of up to 4.5 mm between them. Full article

To establish a finite element model that accurately represents the dynamic characteristics of actual super high-rise building and improve the accuracy of the finite element simulation results, a finite element model updating method for super high-rise building is proposed based on the response surface method (RSM). Taking a 120 m super high-rise building as the research object, a refined initial finite element model is firstly established, and the elastic modulus and density of the main concrete and steel components in the model are set as the parameters to be updated. A significance analysis was conducted on 16 parameters to be updated including E1–E8, D1–D8, and the first 10 natural frequencies of the structure, and 6 updating parameters are ultimately selected. A sample set of updating parameters was generated using central composite design (CCD) and then applied to the finite element model for calculation. The response surface equations for the first ten natural frequencies were obtained through quadratic polynomial fitting, and the optimal solution of the objective function was determined using a genetic algorithm. The results of the engineering case study indicate that the errors in the first ten natural frequencies of the updated finite element model are all within 5%. The updated model accurately reflects the current situation of the super high-rise building and provides a basis for super high-rise building health monitoring, damage detection, and reliability assessment. Full article

Cementitious Capillary Crystallization Waterproofing Material (CCCW), as an efficient self-healing agent, can effectively repair damage in concrete structures, thereby extending their service life. To address the various types of damage encountered in practical engineering applications, this study investigates the impact of different mixing methods for CCCW (including internal mixing, curing, and post-crack repair) on the multi-dimensional self-healing performance of concrete. The self-healing capacity of concrete was evaluated through water pressure damage self-healing tests, freeze–thaw damage self-healing tests, mechanical load damage self-healing tests, and crack damage self-healing tests. The results show that the curing-type CCCW mixing method exhibited the best self-healing effect in repairing water pressure, freeze–thaw, and load damages, with corresponding healing rates of 88.9%, 92.7%, and 90.5%, respectively. The internally mixed CCCW method was also effective for repairing load damage in concrete, while the repair-type CCCW mixing method demonstrated the weakest repair effect on these types of damage. For concrete with induced pre-existing cracks, the internally mixed CCCW method, after 28 days of water-immersion curing, exhibited a significantly higher crack self-healing ability, with a self-healing ratio of 333.8%. Optical microscopy observations revealed that the crack surfaces were almost fully sealed, with a substantial deposition of white crystalline material at the crack sites. Further analysis using scanning electron microscopy (SEM) and X-ray Diffraction (XRD) provided insights into the surface morphology and phase characteristics of the self-healed cracks, indicating that calcium carbonate (CaCO₃) and calcium silicate hydrate (C-S-H) were the main products responsible for crack healing. Full article

Due to human activities, the evolution of the lower reaches of the Yangtze River is complex, and the underwater terrain near the docks is varied. There may be serious erosion and sedimentation of the bank slope, which will affect the stability and cause engineering accidents. To explore the changes in underwater terrain and their impacts, taking a dock in Jiangsu Province in China as an example, a multi-beam bathymetry system is used to conduct full coverage measurement of the underwater terrain at the front of the dock. A comprehensive analysis method for underwater terrain is proposed from the perspectives of contour lines, cross-sections, etc., in order to monitor the changes in erosion and sedimentation in the dock area. Then, the impact of underwater terrain changes on the bank slope stability is explored by simulating the bank slope soil and the concrete pile foundation. Targeted engineering measures to ensure the stability and safety of the dock and bank slope are proposed. The methods and conclusions proposed in this manuscript, including underwater terrain measurement, analysis of the impact of underwater terrain changes on stability, and recommendations for related engineering measures, will help to ensure the long-term safe operation of docks. This research will be of great significance in reducing water conservancy accidents and promoting sustainable and efficient development of water resources. Full article

Long-gauge fiber optic sensors have proven to be valuable tools for structural health monitoring, especially in reinforced concrete (RC) beam structures. While their application in this area has been well-documented, their use in RC columns remains relatively unexplored. This suggests a promising avenue for further research and development. This paper presents a thorough comparison of long-gauge fiber optic sensors and traditional measurement tools when used to monitor RC columns under small eccentric compressive loading. The evaluation focuses on the stability and precision of each sensor type. A monitoring system was developed for laboratory testing to assess the performance of various sensor types under specific conditions. The system incorporated four measurement schemes, utilizing a combination of embedded and surface-mounted long-gauge fiber optic sensors, linear variable differential transformers (LVDTs), and point sensors (strain gauges). Long-gauge fiber optic sensors, securely mounted on the concrete surface near the tensile side, were found to accurately measure both large and small deformations, outperforming LVDTs. Compared to strain gauges and embedded optic sensors, the long-gauge fiber optic sensors demonstrated superior average strain measurement and minimal interference from protective covers. Full article

Cemented Sand, Gravel, and Rock (CSGR) dams have traditionally used either Conventional Vibrated Concrete (CVC) or Grout-Enriched Roller Compacted Concrete (GERCC) for protective and seepage control layers in low- to medium-height dams. However, these methods are complex, prone to interference, and uneconomical due to significant differences in the expansion coefficient, elastic modulus, and hydration heat parameters among CSGR, CVC, and GERCC. This complexity complicates quality control during construction, leading to the development of Grout-Enriched Vibrated Cemented Sand, Gravel, and Rock (GECSGR) as an alternative. Despite its potential, GECSGR has limited use due to concerns about freeze–thaw resistance. This project addresses these concerns by developing an air-entrained GECSGR grout formulation and construction technique. The study follows a five-phase approach: mix proportioning of C₁₈₀6 CSGR; optimization of the grout formulation; determination of grout addition rate; evaluation of small-scale lab samples of GECSGR; and field application. The results indicate that combining 8–12% of 223 kg/m³ cement grout with 2–2.23 kg/m³ of admixtures, mud content of 15%, a marsh time of 26–31 s. and a water/cement ratio of 0.5–0.6 with the C₁₈₀6 parent CSGR mixture achieved a post-vibration in situ air content of 4–6%, excellent freeze–thaw resistance (F300: mass loss <5% or initial dynamic modulus ≥60%), and permeability resistance (W12: permeability coefficient of 0.13 × 10⁻¹⁰ m/s). The development of a 2-in-1 slurry addition and vibration equipment eliminated performance risks and enhanced efficiency in field applications, such as the conversion of the C₁₈₀4 CSGR mixture into air-entrained GECSGR grade C9015W6F50 for the 2.76 km Qianwei protection dam. Economic analysis revealed that the unit cost of GECSGR production is 18.3% and 6.33% less than CVC and GERCC, respectively, marking a significant advancement in sustainable cement-based composite materials in the dam industry. Full article