https://doi.org/10.11112/jksmi.2026.30.1.1

박수현(Su-Hyeon Park) ; 이병재(Byung-Jae Lee) ; 김윤용(Yun-Yong Kim)

This study investigated the potential of utilizing Fluorine-based Semiconductor Sludge FSS as a mineralizer for the low-temperature sintering of White Portland Cement (WPC) in response to the carbon crisis by demonstrating that FSS-incorporated WPC achieves equivalent or superior compressive strength at a 1,450°C firing temperature (a 50°C reduction from conventional methods), while the resulting repair mortar confirms its applicability as a sustainable repair material by meeting KS standards for whiteness, dimensional stability, and bond performance, with the shear bond strength (1.90 times the tensile bond strength) showing a high correlation (>98 %) to the tensile bond strength.

https://doi.org/10.11112/jksmi.2026.30.1.9

이규완(Kyu-Wan Lee) ; 김도균(Do-Kyun Kim) ; 박영식(Young-Sik Park)

This study proposes a non-contact bridge deflection measurement system utilizing a laser beam and a high-speed action camera to overcome the installation limitations of conventional contact sensors and the dynamic measurement constraints of webcam-based systems. The proposed system is configured with a 4K resolution action camera capable of 100 fps to precisely capture dynamic behaviors during high-speed traffic. Furthermore, a deep learning-based cross-correlation coordinate correction technique was applied to significantly reduce lens distortion and geometric errors. Indoor verification tests demonstrated high precision, recording an error range of approximately 0.03 to 0.04 mm in micro-displacement scenarios of less than 1 mm, which approaches the limit of hardware resolution. In field loading tests conducted on an in-service PSC I-girder bridge, the system confirmed its applicability and reliability, showing a maximum error of less than 0.04 mm under static loads and 0.05 mm under dynamic driving conditions compared to reference LVDTs. The developed system offers a cost-effective and high-precision solution for both static and dynamic displacement measurement, making it highly effective for structural health monitoring of small and medium-sized bridges.

https://doi.org/10.11112/jksmi.2026.30.1.18

고성현(Seong-Hyun Ko)

The objective of this study is to evaluate the failure behavior and seismic performance of octagonal solid-section RC bridge piers and to analyze the influence of lap-spliced longitudinal reinforcement on their failure behavior. A lap-splice detail for longitudinal reinforcement with U-shaped hooks was developed, and the developed detail was applied to three test specimens. Four scaled octagonal solid-section column specimens were fabricated, and cyclic lateral loading tests were conducted under a constant axial load. All specimens were provided with a constant volumetric ratio of transverse spiral reinforcement of 0.592%, while the longitudinal reinforcement ratio ranged from 1.15% to 2.29%. According to the test results, all specimens ultimately failed in a flexural failure mode. The maximum lateral load capacities of the specimens with lap splices were 13∼26% higher than that of the specimen without lap splices, whereas the displacement ductility of the lap-spliced specimens was 25∼34% lower than that of the specimen without lap splices.

https://doi.org/10.11112/jksmi.2026.30.1.28

노승지(Seung-Ji Noh) ; 이종한(Jong-Han Lee)

This study proposes a framework for predicting road surface friction using data collected from Road Weather Information System(RWIS). The framework consists of two main stages: experimental verification of RWIS data reliability and development of a prediction model based on the verified data. Experimental comparisons verified that the friction coefficients measured by RWIS reliably reflect actual changes in road surface conditions, confirming their suitability as reliable indicators. Using the validated dataset, variable importance was evaluated through a Random Forest(RF), and the key variables identified were used to train a Long Short-Term Memory(LSTM) network that captures the temporal characteristics of road friction. By integrating experimental validation with time-series prediction modeling, the proposed framework ensures both reliability and applicability in road surface condition prediction. The outcomes of this study provide a foundation for developing early warning systems for road icing and black ice, contributing to proactive winter road management and improved traffic safety.

https://doi.org/10.11112/jksmi.2026.30.1.35

오상혁(Sang-Hyuk Oh) ; 김현중(Hyun-Joong Kim) ; 유훈(Hoon Yoo) ; 김동주(Dong-Joo Kim)

The existing facility-level management framework has limitations in fully capturing the cumulative damage and detailed deterioration processes of individual structural members. Refining the management unit is a critical prerequisite for extending the service life of road facilities and ensuring efficient maintenance. In this study, a component-level management database (DB) was developed to enhance the precision and efficiency of road infrastructure management. Standard classification schemes for individual components of road facilities were established, attribute data were defined, and a relational database-based management system was designed. The results demonstrate that the proposed component-level DB significantly improves the resolution of inspection information and more effectively supports rational decision-making in maintenance planning.

https://doi.org/10.11112/jksmi.2026.30.1.44

전형민(Hyung-Min Jun) ; 박종건(Jong-Gun Park) ; 허광희(Gwang-Hee Heo)

This study experimentally analyzed the synergistic effect of carbon nanotubes (CNT) and carbon fibers (CF) on the heat generation and electrical properties of cement composites under various thermal conditions. The tests on heat generation and electrical properties were conducted with parameters such as CNT concentrations (0.3 wt.%, 0.6 wt.%), and CF contents (0.3 vol.%, 0.6 vol.%, 1.0 vol.%), various applied voltages (DC 10V, 20 V, 30V, 60V), and different electrode spacings (40 ㎜, 120 ㎜). Furthermore, the surface morphology and microstructure of the conductive cement composite were analyzed using scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). Test results showed that cement composites incorporating CNT and CF together improved the heat generation capacity and electrical properties, confirming that the combination of the two materials was effective in improving conductive properties. In particular, at an applied voltage of 20 V and an electrode spacing of 40 ㎜, the ‘CF0.6CNT0.6’ specimen showed the highest temperature of all specimens, rising to 157.4℃. In addition, as the mixing concentration of CNT and the applied voltage increased, the heat generation capacity improved, and a higher temperature increase effect was exhibited with a narrower electrode spacing. However, even when the concentration of CNT mixed was added up to 1.0 wt.%, the heat generation capacity was not improved. Analysis results of SEM image and EDS confirmed that a conductive network was formed between the CNT and CF particles within the cement matrix.

https://doi.org/10.11112/jksmi.2026.30.1.54

심형민(Hyeong-Min Shim) ; 송민규(Min-Kyu Song) ; 이종한(Jong-Han Lee)

In this study, a model updating technique combining a finite element (FE) analysis model with a deep neural network (DNN) is proposed to evaluate the structural safety of deteriorated bridges. Traditional FE models have limitations in reflecting post-construction conditions of bridges, often leading to discrepancies between analytical and actual structural responses. Moreover, conventional optimization-based updating methods are time-consuming. To address these issues, the proposed method utilizes natural frequencies and mode shapes of the bridge as input data, allowing the DNN to predict member stiffness values. The DNN architecture is automatically optimized through Bayesian optimization. The proposed technique was validated through numerical simulations on PSC-I girder bridge models, demonstrating high accuracy with member stiffness prediction errors within 5% under various damage scenarios. Furthermore, its applicability to real structures was verified using measured data from an in-service railway bridge. The results confirm that the proposed method enables rapid and reliable updating of FE models for practical structural assessment.

https://doi.org/10.11112/jksmi.2026.30.1.62

전승곤(Seung-Gon Jeon) ; 방건혁(Geon-Hyeok Bang) ; 허광희(Gwang-Hee Heo) ; 이재훈(Jae-Hoon Lee)

Large-scale civil engineering structures such as bridges are subjected to various dynamic loads, and when the structural natural frequency coincides with the excitation frequency, resonance may cause a drastic amplification of the structural response. TMD have been widely employed to mitigate such problems; however, their parameters are fixed to the natural frequency assumed at the design stage, so that changes in the structural dynamic characteristics can lead to off-tuning, which may even amplify vibrations. In this study, a CF-TMD(Controlled Friction-Tuned Mass Damper) is developed in which the friction force is switched on and off by electromagnetic force, and a Bang?Bang feedback control algorithm is applied to experimentally verify its vibration mitigation performance. For this purpose, sinusoidal excitation tests are conducted on a cable-stayed bridge model at the first resonant frequency of 3.50 Hz and at 3.65 Hz, where off-tuning occurs, and three cases?uncontrolled, TMD, and CF-TMD?are compared. The experimental results show that, at 3.50 Hz, the maximum displacement in the uncontrolled case (8.35 mm) is reduced to 1.36 mm (a reduction of approximately 83.7%) with the TMD, and further to 1.24 mm (about 85.1% reduction) with the CF-TMD, demonstrating superior control performance. In addition, at 3.65 Hz, the maximum displacement increases from 2.97 mm to 4.06 mm when the TMD is applied, indicating vibration amplification due to off-tuning, whereas it decreases to 2.24 mm when the CF-TMD is applied, corresponding to a displacement reduction of about 24.6% compared with the uncontrolled case. These results confirm that the CF-TMD can provide stable vibration control not only at the resonant frequency but also in the frequency range where off-tuning occurs.

https://doi.org/10.11112/jksmi.2026.30.1.72

이근석(Geunseok Lee) ; 김방현(Banghyeon Kim) ; 조수진(Soojin Cho)

This study addresses the problem of performance degradation in deep learning-based crack detection models when applied across different environments due to inherent domain gaps between datasets. To counteract this, a crack detection framework was developed by implementing Domain Adaptation (DA) technique using weak labels, which can be made in both image-level and point-level. The methodology introduced three key improvements to existing DA methods: the application of dilation-erosion techniques, the integration of the Dice Coefficient Loss function, and the removal of Output Alignment Loss. Experiments conducted across three domain adaptation scenarios using four public datasets demonstrated the effectiveness of the proposed DA approach, achieving a maximum F1-score increase of 16.79%, 26.66%, and 18.78% across the tested scenarios. Findings indicated that image-level pseudo-labels were highly effective when the domain gap was small, while point-level labels yielded greater benefits when the domain gap was large. Ultimately, this research confirms that employing weak labels enables efficient domain adaptation, resulting in high crack detection performance robust to various domain differences.

https://doi.org/10.11112/jksmi.2026.30.1.84

김진성(Jin-Sung Kim) ; 김호준(Ho-Jun Kim) ; 현창진(Chang-Jin Hyun) ; 김윤용(Yun-Yong Kim)

This study developed a restoration material by mixing with functional binders, and wet-response admixtures added to overcome wet environments, and investigated the characteristics the performance of developed restoration material. Wet-response admixtures consist of poly acrylamide and methylcellulose and have been used to enhance workability and durability against wet environments. The functional binders contain ground blast furnace slag and surface-modified silica fume, and was introduced to improve the durability of the restoration materials. The restoration material, developed in the present study, was properly placed without dissociation or loss in the wet condition. The pH of the restoration material was measured to be 9.9 and the amount of suspended solids was 46 mg/L, which satisfied the KCI-AD 102 standard. The strength measurement results of the restoration material, mix SEA-5, showed that the compressive strength, the flexural strength and the bond strength were 55.2 MPa, 15.56 MPa and 1.75 MPa, respectively.

https://doi.org/10.11112/jksmi.2026.30.1.91

김상우(Sang-Woo Kim) ; 이선호(Sunho Lee) ; 장명호(Myung-ho Jang) ; 이정윤(Jung-Yoon Lee)

This study compares domestic and international structural design codes to prevent premature failure of reinforced concrete (RC) beams subjected to indirect loading and evaluates hanger reinforcement design approaches for structural design applications. A comparative review of ACI 318-25, CSA A23.3-24, and Eurocode 2 indicates that the CSA Code provides the most specific recommendations regarding the required amount and reinforcing region of hanger reinforcement intended to prevent strength reduction due to indirect loading. In addition, this study proposes a shear-based hanger reinforcement design concept that distinguishes between the shear contributions of concrete and hanger reinforcement by considering the shear strength reduction characteristics of RC deep beams subjected to indirect loading. Based on the proposed design concept, the applicability of the CSA provisions to RC deep beams under indirect loading was evaluated. The results show that when the soffit offset ratio between intersecting beams is 0.5, the amount of hanger reinforcement specified by the CSA Code is insufficient to prevent shear failure. In contrast, when the soffit offset ratio is 0.25 or less, the CSA provisions require up to 1.8 times more hanger reinforcement than that required to prevent shear strength reduction.

https://doi.org/10.11112/jksmi.2026.30.1.99

박상아(Sang-Ah Park) ; 김승훈(Seung-Hun Kim) ; 정재원(Jae-Won Jeong)

This study reevaluates the design equations for the development length of tension reinforcement anchored at reinforced concrete beam ends subjected to bearing stress. Previous studies have shown that the current KDS 14 20 52 provisions are overly conservative when applied to beam-end anchorage in deep beams evaluated using strut-and-tie models (STMs). A total of 241 reinforced concrete deep beam specimens with shear span-to-depth ratios not exceeding 2.0 were collected from existing studies and classified according to the presence of vertical shear reinforcement. Appropriate strut-and-tie models were applied depending on the reinforcement configuration, and the anchorage capacity of tension ties was evaluated using development length equations from KDS and ACI codes. Comparisons between experimental and nominal shear strengths indicated that tension tie failure governed all specimens and that both codes significantly underestimated shear strength. The average ratios of experimental to nominal shear strength were 2.40 for KDS and 2.18 for ACI, confirming the conservative nature of the current provisions. The results demonstrate the need to reevaluate development length design equations for beam-end anchorage in conjunction with rational strut-and-tie model selection.

https://doi.org/10.11112/jksmi.2026.30.1.105

정재원(Jae-Won Jeong) ; 양성주(Sung-Ju Yang) ; 황환명(Hwan-Myung Hwang) ; 김의용(Eui-Yong Kim) ; 김승훈(Seung-Hun Kim)

This study conducted the push-out tests to investigate the bond behavior of L-shaped steel members with welded flat-plate shear reinforcement embedded in RC (reinforced concrete) and SFRC (steel fiber?reinforced concrete). The test results showed that all specimens exhibited splitting failure, characterized by concrete splitting along the edge region of the embedded L-shaped steel. As the concrete cover thickness increased, both the maximum load and bond stress generally increased. When the cover thickness was increased by approximately 66.7%, the average bond stress of the F0 (RC) and F1 (SFRC) series increased by about 21.1% and 14.1%, respectively. In contrast, when the bond length was doubled, the average bond stress of the F0 and F1 series increased by about 44.0% and 2.6%, respectively. The average bond stress for all specimens of the F0 series was 3.44 MPa, which was about 2.0% different from 3.37 MPa of the F1 series. Therefore, it is judged that the steel fiber reinforcement is more effective in suppressing the rapid decrease in stiffness after the maximum load rather than improving the bond stress. Considering the safety factor, the lower 5% bond stress of the L-shaped steel specimen welded to the flat plate was calculated and evaluated as 1.88 MPa, and the lower 5% bond stress coefficient (k) normalized by the square root of the concrete compressive strength and the cover thickness correction factor was evaluated as k=0.324.

https://doi.org/10.11112/jksmi.2026.30.1.113

엄정우(Jeongwoo Um) ; 심현호(Hyeonho Sim) ; 이재모(Jaemo Lee) ; 장민우(Min Woo Jang) ; 백중철(Joongcheol Paik) ; 염상국(Sang-Guk Yum) ; 박민수(Minsoo Park)

This study proposes a design optimization framework that integrates an Artificial Neural Network (ANN) surrogate model with a Genetic Algorithm (GA) to mitigate the significant computational costs associated with Computational Fluid Dynamics (CFD) analysis in the geometric design of artificial surfing reefs. The design variables are defined as the slope ratio (S), width (W), height (H). Surfing performance is quantified as a composite score through the normalization and weighted combination of wave height, wave duration, and wave angle. Initially, an ANN was trained using OpenFOAM simulation results from 225 design cases generated via Latin Hypercube Sampling (LHS). To enhance model performance, the dataset was augmented by assigning initial ANN predictions as synthetic data to grid candidate points across the entire design space. Analysis of ten repeated training sessions across seven augmentation cases demonstrated that the average validation R^2 and test R^2 improved to ranges of 0.64-0.67 and 0.82-0.84, respectively. The resulting surrogate models served as fitness evaluators within the GA to identify optimal reef geometries. Finally, the validity of the optimized designs and the overall effectiveness of the framework were verified by comparing OpenFOAM re-analysis results with the surrogate model predictions.

https://doi.org/10.11112/jksmi.2026.30.1.122

고민정(Min-Jeong Ko) ; 김규용(Gyu-Yong Kim) ; 이예찬(Yae-Chan Lee) ; 심희진(Hee-Jin Shim) ; 임수빈(Soo-Bin Lim) ; 김정효(Jeong-Hyo Kim)

This study evaluated the mechanical properties and multi-radiation shielding effectiveness of heavyweight concrete incorporating hematite aggregates. Various candidates for heavyweight aggregates, including hematite, magnetite, oxidizing slag, copper slag, and ferro nickel slag, were investigated to analyze density variations according to the aggregate-to-binder(Agg./Binder) ratio. Hematite was selected as the optimal aggregate due to its superior efficiency in achieving the target density. To further enhance neutron shielding performance, 0.3% boron carbide by weight of concrete was added as an admixture.The experimental results indicated that the concrete reached an average density of 3,687 kg/m³, surpassing the target value, and achieved a 28-day compressive strength of 46.8 MPa, thereby satisfying the structural requirement of 43.5 MPa. In radiation shielding tests, gamma-ray transmittance in the 0.3∼1.6 MeV range was reduced by approximately 30% compared to ordinary concrete. Furthermore, the transmittance of fast and thermal neutrons decreased by approximately 17∼23% and 51%, respectively. These results verify the effectiveness of gamma-ray attenuation driven by high-density aggregates and the neutron moderation and absorption capabilities provided by boron carbide. This research is significant as it provides a quantitative basis for designing high-performance shielding materials that enhance radiation safety and overcome the limitations of conventional thickness-dependent shielding designs through composite shielding strategies.

https://doi.org/10.11112/jksmi.2026.30.1.133

김규섭(Kyuseup Kim) ; 김진국(Jin-Kook Kim)

This study found that guard cable barriers using steel wires experience tension loss over time due to various factors, including deformation of anchoring devices, friction with fixing devices, and steel relaxation. Tension loss in guard cables can cause external sagging due to their own weight, create visual discomfort, and even cause the guard cables to lose their protective effect against external impacts. Therefore, this study identifies various causes of tension loss in guard cable barriers and examines their respective impacts to determine the need for maintenance. Loads were planned for the guard cables and the target structures for each span and load-deflection simulations were performed on the guard cable barrier. Comparing the results of effective tension force and deflection calculations, it was confirmed that the conventional type could not meet the requirements of the Road Safety Facility Installation and Management Guidelines under load. A proposed type was developed to address the shortcomings of a conventional type, and compared them with a conventional type through simulation to confirm the performance potential based on analysis. The functionality and performance about proposed type were verified by comparing simulations with conventional type. The load-deflection simulation results for the proposed type showed that it maintained its effective tension force compared to the conventional type when the guard cable lost tension due to load. Furthermore, the proposed type meets the regulation on the provisions for guard cable deflection in the Road Safety Facility Installation and Management Guidelines. The various findings obtained through this study are expected to be useful in estimating maintenance costs and establishing inspection schedules for existing guard cables. In addition, it is expected that future related inspection standards and facilities will be supplemented based on this study and utilized for maintenance of vehicle safety fences and rockfall prevention nets, thereby minimizing the resulting damage.