https://doi.org/10.4334/JKCI.2025.37.5.543

전상민(Sang-Min Jeon) ; 정철우(Chul-Woo Chung) ; 김지현(Ji-Hyun Kim) ; 권성준(Seung-Jun Kwon) ; 장승엽(SeungYup Jang) ; 김형기(Hyeong-Ki Kim)

In this study, the appropriateness of the current domestic limit for initial chloride content in concrete was evaluated by assessing the probability of reinforcement corrosion using a probabilistic approach. The fib Model Code 2010 was utilized as the analytical framework. To ensure reasonable input parameters?such as mix proportions, exposure conditions, and cover depth?relevant statistical data and standards were thoroughly reviewed. The probability of reinforcement corrosion was then evaluated under various design conditions, with the initial chloride content per unit binder ranging from 0.01% to 0.2% across different mix proportion scenarios. The results indicated that, for structures exposed to external chloride ingress, higher allowable initial chloride content can significantly influence design outcomes. However, for structures located in environments where external chloride ingress is not a concern, the current domestic limit of 0.3 kg/m3 is relatively conservative compared to international standards. From a theoretical perspective, based on the distribution of initial chloride content in the fib Model Code 2010, it was found that increasing the initial chloride content up to 0.2 wt.%/binder?equivalent to the minimum threshold in EN 206:2013?still provides an adequate safety margin.

https://doi.org/10.4334/JKCI.2025.37.5.553

채경훈(Kyoung-Hun Chae) ; 임정국(Jeong-Guk Im) ; 박태원(Tae-Won Park) ; 허무원(Moo-Won Heo)

In this study, the seismic performance of torque-controlled expansion anchors with improved structural details (sleeve and header) was evaluated. Simulated seismic tension tests were conducted to assess the anchors seismic performance in accordance with the service-condition tests outlined in the “Concrete Anchor Design Method and Example Book (KCI-M-24-018)”. The repeated load tests showed that no damage or failure occurred in any of the anchors up to the end of the test, and the monotonic load tests confirmed that the average residual tension strength of all anchors attained or exceeded the evaluation criterion of 1.6Neq. The failure mode of all anchors was characterized by concrete breakout failure accompanied by radial cracking. This result is attributable to the improved structural details, which provide high tension resistance that effectively inhibits cracking and the effects of repeated loading, thereby evenly distributing the external load over the concrete substrate. In addition, the characteristic strength (F5%) of all the anchors tested was higher than the nominal strength (Nn) as determined by the domestic anchor design formula. Therefore, it was confirmed that the torque-controlled expansion anchor with improved structural details is suitable for non-structural materials that require seismic design through high seismic tensile resistance.

https://doi.org/10.4334/JKCI.2025.37.5.563

강호비(Ho-Bi Kang) ; 임동규(Dong-Gyu Lim) ; 김영진(Young-Jin Kim) ; 최명성(Myoung-Sung Choi)

This study experimentally investigated the bond performance of precast bridge deck joints incorporating ultra-high-performance Concrete (UHPC), aiming to overcome the limitations of existing design codes and enhance both constructability and structural efficiency. Traditional jointing methods, such as loop splices, exhibit drawbacks like reduced constructability and structural inefficiency. As an alternative, UHPC was applied as a joint-filling material to assess its potential for reducing splice lengths while securing structural performance. Fourteen splice specimens were tested under four-point loading, with compressive strength levels (80 MPa, 100 MPa, 120 MPa) and splice lengths (8db, 10db, 15db) considered as primary variables. The test results demonstrated that UHPC with a compressive strength of 100 MPa achieved sufficient structural performance even with splice lengths shorter than those specified in current design standards. Additionally, improvements in bond stress and crack control attributed to fiber reinforcement were observed. These findings provide fundamental data for improving anchorage and splice design provisions to reflect the superior material properties of UHPC, while also maximizing the constructability advantages of precast construction.

https://doi.org/10.4334/JKCI.2025.37.5.573

강호비(Ho-Bi Kang) ; 임동규(Dong-Gyu Lim) ; 김영진(Young-Jin Kim) ; 최명성(Myoung-Sung Choi)

This follow-on work examines the limitations of existing design standards in estimating the bond strength and development length of ultra-high-performance concrete (UHPC) and proposes an improved design equation. To achieve this, domestic and international design standards were reviewed, and a lap splice test was conducted to evaluate the bond performance of UHPC. The experimental results revealed that existing design standards may not fully reflect the actual bond performance of UHPC. For example, Eurocode 2, KDS, and the Fiber-Reinforced SUPER Concrete Structural Design Guidelines estimate bond strength based on pull-out tests, while neglecting splice length. Although ACI 318 considers the effect of splice length on bond performance, it is based on empirical formulas derived for conventional concrete, resulting in discrepancies when applied to UHPC. To address these issues, this work proposes a new bond strength model and development length equation that more accurately reflect UHPC bond characteristics. The proposed approach is expected to optimize bond performance, enhance structural safety, and improve the efficiency of precast construction employing UHPC.

https://doi.org/10.4334/JKCI.2025.37.5.581

김태훈(Tae-Hoon Kim) ; 방춘석(Choon-Seok Bang) ; 김이현(Leehyeon Kim) ; 선창호(Chang-Ho Sun) ; 김익현(Ick-Hyun Kim)

This work involved identifying and quantifying the corrosion characteristics of prestressing strands and examining the associated tensile strength reduction, a key mechanical property that significantly affects the durability and structural safety of deteriorated prestressed concrete structures. Using the charge passed through the proposed test circuit over a certain period, the expected corrosion level of the prestressing strand specimens was calculated based on Faraday’s rule. This quantification method was able to accurately predict the corrosion characteristics of the prestressing strands. Furthermore, monotonic tensile tests conducted on 64 accelerated-corroded strand specimens provided a reasonable reduction equation for tensile strength degradation. This equation provides a basis for modeling both the local and global behavior of corroded prestressing strands.

https://doi.org/10.4334/JKCI.2025.37.5.589

우욱용(Ukyong Woo) ; 이명훈(Myung-Hun Lee) ; 최하진(Hajin Choi)

The issue of 3D point cloud loss in rebar spacing measurement when using depth cameras on construction sites was investigated. By analyzing the structural characteristics of depth cameras, this study identifies key causes of data loss, such as repeated rebar patterns and lighting conditions, and proposes two measurement techniques: intersection-based measurement and camera tilt adjustment. Field experiments were conducted on slab and column rebar placements to verify the accuracy and applicability of the proposed methods. The results showed that both methods enabled complete measurement coverage, with a maximum error rate of 7%, which falls within the 10% tolerance typically permitted in construction inspections. These findings demonstrate that the proposed measurement methods can effectively overcome the limitations of conventional depth camera?based systems, enabling accurate and real-time monitoring of rebar placement. Ultimately, this contributes to advancing digital and remote-based construction supervision by offering a practical and reliable alternative to traditional on-site inspections.

https://doi.org/10.4334/JKCI.2025.37.5.599

신혜원(Hyewon Shin) ; 박예원(Yewon Park) ; 전종수(Jong-Su Jeon)

This study develops predictive equations for model parameters to simulate the nonlinear hysteretic behavior of hollow reinforced concrete (RC) columns using a lumped plasticity model. The model parameters were calibrated against previously reported experimental results, and predictive equations were derived through regression analysis. The proposed equations exhibited better accuracy compared with an existing distributed plasticity model in terms of initial stiffness, maximum strength, and strength degradation. The proposed model was applied to numerical bridge models incorporating hollow RC columns, and a parametric study was conducted to evaluate seismic fragility curves under varying design parameters. The results indicated that shear span, longitudinal reinforcement ratio, and section thickness are critical parameters influencing the seismic vulnerability of hollow RC columns.

https://doi.org/10.4334/JKCI.2025.37.5.609

서수연(Soo-Yeon Seo) ; 윤현도(Hyun-Do Yun)

Code equations for calculating the compressive strength of horizontal joints in precast concrete wall structures were reviewed, and the influence of major factors affecting compressive strength was identified based on the results of 100 horizontal joint compression performance tests conducted previously. Additionally, these data were used to assess the suitability of current code equations. The findings revealed that the PCI method provided the most reasonable predictions. However, for both internal and external joints, the compressive strength was often inaccurately predicted and not consistently evaluated on the conservative side. Based on data analysis, a modified equation is proposed for the PCI method to properly account for the grout width expansion factor. The use of this modified equation enables more accurate estimation of the compressive strength of horizontal joints.

https://doi.org/10.4334/JKCI.2025.37.5.619

윤준영(Jun-Young Yun) ; 조진우(Jin Woo Cho) ; 조은선(EunSeon Cho) ; 한상환(Sang Whan Han)

When assessing the seismic performance of reinforced concrete (RC) frames, it is important to use an accurate numerical model for columns because the seismic behavior of the columns significantly affects the structural performance. In most previous studies, the parameters of column models were determined using empirical equations. However, it is difficult to fully capture the complex and nonlinear characteristics of actual columns using empirical equations developed from regression analyses. This study developed a machine learning (ML) model to construct an idealized backbone curve for RC columns. For this purpose, test data for rectangular RC columns under cyclic loading were collected from previous research. Three damage states were defined to construct the backbone curve, and the accuracy of the proposed ML model was subsequently validated. It was shown that the measured backbone curves of the collected columns could be precisely predicted using the parameter values obtained from the proposed ML model.

https://doi.org/10.4334/JKCI.2025.37.5.627

임태훈(Tae-Hun Lim) ; 문선영(Sun-Young Moon) ; 최가은(Ga-Eun Choe) ; 이승훈(Seung-Hoon Lee) ; 김한수(Han-Soo Kim)

This study presents a single degree of freedom analysis procedure for reinforced concrete members with asymmetric rebar layout subjected to axial and blast loads using the OpenSees program. The nonlinear dynamic responses of symmetric and asymmetric RC columns were compared with experimental results to verify the accuracy of the proposed method. Sectional analysis of a representative example showed that when subjected to 10 % of the maximum axial load, the flexural strength of the asymmetric section increased by 1.2 times compared to the symmetric section. Blast analysis results indicated that as plastic deformation increased, the difference in dynamic response between symmetric and asymmetric sections also increased, reaching up to 36.8 %. This study presents a method to improve the blast performance of reinforced concrete columns without increasing the cost, and can be utilized as an efficient design method for performance-based blast design in the future.

https://doi.org/10.4334/JKCI.2025.37.5.635

곽병훈(Byeong-Hun Kwak) ; 박지훈(Ji-Hun Park)

In this study, the use of plastered amorphous steel fiber-reinforced mortar, without steel wire mesh, is proposed as a seismic retrofit strategy for unreinforced masonry buildings. The proposed strengthening method was applied to masonry wall specimens in which the piers adjacent to openings were prone to rocking failure. Cyclic loading tests were conducted to validate the effectiveness of the proposed retrofit strategy. In addition, strength equations for the amorphous steel fiber-reinforced mortar layer on masonry walls with openings were developed, accounting for flexural strength and equilibrium in the panel zone. The accuracy of these equations was verified through comparison with experimental results.

https://doi.org/10.4334/JKCI.2025.37.5.645

최원준(Wonjun Choi) ; 이상현(Sanghyun Lee) ; 김치경(Cheekyeong Kim) ; 허석재(Seokjae Heo)

Artificial intelligence (AI) has increasingly transformed structural engineering over the past decade. However, the rapid proliferation of diverse AI applications often obscures a holistic understanding of their true impact on the engineering profession. This paper addresses this gap by providing a systematic review of 35 key studies from 2015 to 2025 across five core domains: structural health monitoring (SHM), design optimization, seismic design, predictive maintenance, and large language models (LLMs). Rather than viewing them as isolated facets, we synthesize emerging these trends to propose that the field is converging toward a new, unified paradigm: the ‘Human-AI Collaborative System.’ In this paradigm, AI excels as a tireless computational partner for complex analyses and data processing, while the human engineer is elevated to the role of a strategic decision-maker, focusing on problem definition, critical judgment, and ethical oversight. This review highlights that the primary challenge is no longer just developing more accurate AI, but rather creating a seamless and reliable integration framework for human-AI collaboration. Ultimately, this paper provides a forward-looking perspective on how such synergy will define the future of structural engineering, fostering safer, more efficient, and more innovative built environments.

https://doi.org/10.4334/JKCI.2025.37.5.655

장태수(Tae Soo Jang) ; 이영욱(Young-Wook Lee)

The effect of mat foundation modeling on the seismic performance of low-rise pilotis buildings was evaluated using nonlinear static analysis. The seismic performance of the example building with unidirectional or bidirectional eccentricity was evaluated after being stiffened with steel braces, in accordance with the Seismic Performance Evaluation Guidelines (SPEG, 2021). The mat foundation was modeled using the fixed-end (FE) approach per SPEG (2021) and a spring model with finite stiffness according to ASCE/SEI 41-23. Additionally, in cases of foundation tension, a fixed-end model allowing uplift (FE-R) per SPEG (2021) was analyzed. For both example buildings, the maximum reaction force predicted by the spring model was lower than that of the FE and FE-R models. This reduction is attributed to the spring model’s distribution of concentrated forces due to spring stiffness and yielding. Moreover, the ratio of the reaction force to the bearing capacity of the foundation in the spring model was smaller than that of both the FE and FE-R models.