KSCE Journal of Civil Engineering最新文献

Accurately measuring cable forces is crucial for reliable bridge condition evaluation, yet it remains a challenging task. This study proposes the use of a High-strength Steel Wire Fiber Bragg Grating (HSW-FBG) sensor embedded in commonly-used cables composed of 5–7 mm parallel steel wires. The HSW-FBG sensor facilitates direct strain measurement, offering a simple and user-friendly packaging process for high-precision monitoring throughout the cable’s lifespan. The results demonstrate excellent linearity and repeatability in strain detection of the HSW-FBG sensor. The length of the packaging layer has the most significant impact on the strain transfer efficiency (STE) coefficient and should be at least 60 mm required for optimal performance. Additionally, the elastic modulus of the packaging layer moderately affects the STE coefficient. Adhering to these packaging parameter requirements ensures that the STE coefficient of the HSW-FBG sensor is very close to 1, enabling for high-precision measurement without correction. A systematic analysis of the STE coefficient of the HSW-FBG sensor is conducted, determining reasonable values for the packaging parameters. These findings lay the groundwork for future engineering applications, facilitating accurate measurement of cable forces in practical scenarios.

The International Roughness Index (IRI) is closely related to pavement distress. However, previous studies employing statistics and machine learning approaches would present challenges in comprehensively analyzing the influence of pavement distress on IRI considering their severities. This study introduces interpretable machine learning to investigate the influence of pavement distress on IRI, with a particular focus on the severity of pavement distress. The pavement distress and IRI data for flexible pavements obtained from the long-term pavement performance (LTPP) program were meticulously preprocessed. The developed random forest (RF) model demonstrated satisfactory predictive performance, with an RMSE of 0.2191 and an R² of 0.7874. The relationship between pavement distress and IRI, as captured by the developed model, was further analyzed using the SHapley Additive exPlanations (SHAP) method. The model interpretation identified the transverse crack, rutting, and alligator crack as the key factors influencing IRI. Notably, both transverse and alligator cracks exhibited significant contributions to IRI increment at medium and high severity levels, highlighting the importance of proactive maintenance for these distress types at lower severity levels. Additionally, a threshold in rutting depth was observed, which could increase IRI. A comparative analysis with the AASHTO MEPDG smoothness model demonstrated that the predictive performance of the RF model was notably superior.

Large-scale freezing projects, especially horizontal freezing projects, suffer from the problem of long exposure times, and weakening of the frozen curtain often occurs in the excavation stage. An analytical solution for the temperature between the freezing pipe and excavation surface was deduced in this study to evaluate the freezing effect at this stage. The solution is verified by in-situ measurements of a large-scale freezing project. The analytical solution shows that the temperature is related to the thermal conductivity of the frozen curtain, the shotcrete, the refrigerant temperature, the excavation surface temperature, and the design scheme of the frozen curtain. Moreover, the excavation surface temperature (T_s) is the critical factor. Then, the equations for the thickness and average temperature of the frozen curtain on the side close to the excavation area are derived. Numerical calculations of the frozen curtain base on analytical solution were carried out to analytical frozen curtain. The results show that when the heat dissipation of the exposed excavation surface is considered, the tensile stresses of the vault and bottom plate increase by up to 135%, the compressive stress of the sidewall increases by 29%, and the shear stress of the shoulder increases by 144%. While three solutions were proposed, and their application scenarios and effects are discussed. This study can provide a reference for the design of large-scale freezing projects to protect the frozen curtain after excavation.

To evaluate the seismic performance of aeolian sand concrete shear walls with hidden bracings, a total of 6 specimens were designed and constructed. These specimens were subjected to low cyclic load experiments while maintaining a constant axial compression ratio to assess the impact of the hidden bracings installation on the seismic performance of these walls. The findings reveal that the failure patterns of the shear walls, both with and without hidden bracings, are comparable. The formation and development of plastic hinges were observed at the wall’s base, which result in significant structural failure. The aeolian sand concrete shear walls with hidden bracings have superior load-bearing capacities when compared to their conventional counterparts under same lateral displacements. The hysteresis curves obtained from all 6 specimens are relatively complete and display an evident pinching effect. The aeolian sand concrete shear walls equipped with hidden bracings demonstrate enhanced seismic energy dissipation and ductility relative to the ordinary ones. After analysis and comparison, it is determined that a cumulative damage analysis model, based on repeated energy loads of concrete structures, aligns well with test results. This model proves to be an effective tool for evaluating the damage performance of aeolian sand concrete shear walls with hidden bracings.

The impressed current technique, commonly used in laboratory studies on corroded reinforced concrete, predicts mass loss via Faraday’s law. Although this method is useful for researchers, calibration is crucial to align intended and actual results, particularly regarding concrete type. The purpose of this work was to calculate the calibration parameters for different concrete mixtures that included steel or polypropylene fibres in varying amounts. The investigation was conducted using twenty-one RC columns, which were categorized into seven groups. For a maximum cumulative volume fraction of 1%, each group of columns had a specific fiber-reinforced concrete mix with a specific proportion of steel and/or polypropylene fibers. The corrosion of these reinforced concrete (RC) columns was accelerated through the implementation of the impressed current regime. Gravimetric measurements were conducted on these columns following the completion of the corrosion process. Ultimately, this study encompasses the findings and an analysis of the calibration parameters specific to the different combinations and proportions of fiber-reinforced concrete. Moreover, this research incorporates parametric studies that examine the effects of different ratios of polypropylene and/or steel fibres, together with comprehensive evaluations of the associated cost, offering precise and in-depth observations inside its scope.

In order to expand the application range of polymer reinforced concrete (PRC) and explore the effect of polymer on the impact resistance of concrete, the dynamic compression test on PRC with polymer content (by volume) of 0, 4%, 8% and 12% was carried out. The effects of polymer content and strain rate on the mechanical properties of PRC were studied, and relevant micro-mechanism was analyzed by SEM and MIP tests. The results show that the polymer can improve the dynamic mechanical properties of concrete, and the dynamic mechanical properties of PRC with polymer content of 4% is the best. With the increase of polymer content, the peak strain of PRC increases, the dynamic compressive strength of PRC first increases and then decreases, and the fractal dimension of fragments of PRC first decreases and then increases. The impact toughness of PRC is larger than that of plain concrete, and the impact toughness of PRC with polymer content of 4% is the maximum. Polymer can improve the interfacial transition zone of concrete through filling and bridging, and optimize the pore structure of concrete, thus improving the mechanical properties of concrete at high strain rate. Polymer can be used to improve the impact resistance of concrete.

The stability performance of the frozen curtain formed under standpipe freezing is closely associated with the weak zone penetrated by thermal gradient-related fracture (TGF). The TGF-rich zone further affects the liquid phase flow when the frozen curtain is thawed. However, there is a lack of studies on the TGF-rich zone within the frozen curtain. To address this gap, a simplified and practical 2D bonded particle model-based numerical simulation strategy was developed to identify the possibility of acquiring field characteristics of the TGF-rich zone by conducting numerical tests on samples considering size effects. The results, validated by the experiment, indicated that the influence of size on crack localization zone was comparable to that of the parameter gradient but had a weaker characteristic on crack orientation, which represents the orientation of TGF. In particular, the characterization result of the TGF-rich zone using crack localization zone in the simulation closely matched that using lateral strain localization zone both in simulation and experiment. Regarding the size effects of the TGF-rich zone revealed in the simulation, the estimated field length of the TGF-rich zone accounted for approximately 30% of the zone width characterized by a horizontal thermal gradient, with maximum orthotropic deformation occurring at about 10% of the zone width. These observations validate the existence of TGF within the frozen curtain and contribute to the development of a precise grouting technique to mitigate subsidence within soil deposits subjected to freeze-thaw.

The slime mould algorithm (SMA), a revolutionary metaheuristic algorithm with streamlined operations and processes, is frequently utilized to solve optimization issues in various fields. This paper proposed a modified slime mold method (HKTSMA) based on multiple adaptive strategies to ameliorate the convergence speed and capacity to escape local optima. In HKTSMA, the scrambled Halton sequence was utilized to increase population uniformity. By Adjusting the oscillation factor, HKTSMA performs better in controlling the step length and convergence. A novel learning mechanism was proposed based on the k-nearest neighbor clustering method that significantly improved the convergence speed, accuracy, and stability. Then, to increase the probability of escaping the local optima, an enhanced adaptive t-distribution mutation strategy was applied. Simulation experiments were conducted with 32 test functions chosen from 23 commonly used benchmark functions, CEC2019 and CEC2021 test suite and 3 real-world optimization problems. The results demonstrated the effectiveness of each strategy, the superior optimization performance among different optimization algorithms in solving high-dimensional problems and application potential in real-world optimization problems.

To address the problem of brittle damage of CGACs under seismic loads, a C&S-RAC and an EB-SAC were developed. Multiple sets of shaking table model tests of anchored slopes under the excitation of El Centro, Landers and sine waves were carried out. The effect of the type and frequency of seismic waves on the dynamic response law of the C&S-RAC and EB-SAC reinforced slopes was clarified, and a new method for evaluating the dynamic stability of anchored slopes based on GMM was established. The results show that the shock-absorbing devices of the C&S-RAC and EB-SAC can effectively reduce the shock effect of earthquakes on slopes and reduce the whiplash effect of anchored slopes. The seismic reinforcement performance of each type of anti-seismic anchor cable differs at different seismic frequencies, and the influence of the seismic wave frequency should be considered when selecting anti-seismic anchor cables in the seismic reinforcement design of slopes. The EB-SAC buffer cushion effectively decreases the vibration intensity of the anchor plate and has a stronger seismic isolation effect on high-frequency seismic waves. The research results provide more references for the selection of anchor cables for slope reinforcement in high seismic intensity areas and the stability evaluation of anchored slopes during earthquakes.

Pore-scale variables, specifically porosity and permeability, are vital in deep resource exploration projects like geothermal energy and shale gas. Digital rock measurement techniques (DRMTs) are commonly employed to match these variables with experimental results. However, limited attention has been given to identifying errors and size effects on pores and pore scale variables, as well as spatial heterogeneous characteristics of pore-networks. In this research, we define pore scale variables and investigate the size effects on these variables through statistical analysis. Additionally, we propose novel empirical formulas for predicting porosity and permeability based on X-ray CT images acquired at varying resolutions from the same carbonate rock sample. Our results indicate that the scanning direction has minimal influence on the physical and hydraulic properties, while these properties are significantly affected by image resolution. The porosity and permeability calculated using the proposed formulas show good agreement with experimental results, with errors below 10%. Consequently, the proposed formulas prove to be effective and reliable in evaluating physical and hydraulic properties based on DRMTs.