https://doi.org/10.11112/jksmi.2025.29.3.1

김일순(Il-Sun Kim) ; 최소영(So-Yeong Choi) ; 양은익(Eun-Ik Yang)

In this study, the workability, compressive strength, chloride resistance, and drying shrinkage of concrete mixed with functional materials such as copper powder, phytoncide, and zeolite were evaluated to examine their effects on fundamental properties and durability. The test results showed that the slump and air content tended to be similar to or slightly lower than those of the reference mix, depending on the type of functional material. Compressive strength and chloride resistance generally increased or remained similar compared to the reference mix. Although drying shrinkage either increased or decreased depending on the mixture, the overall variation was relatively small. Zeolite was found to reduce workability by absorbing mixing water and decreasing the effective water-to-cement ratio, while enhancing compressive strength and chloride resistance through pozzolanic reactions. Among the functional materials evaluated, zeolite had the most significant influence on the properties of concrete. In contrast, copper powder and phytoncide were found to have minimal effect.

https://doi.org/10.11112/jksmi.2025.29.3.10

장홍석(Hong-Seok Jang) ; 김성일(Sung-il Kim) ; 소승영(Seung-Young So)

When using a formwork exclusively, the concrete residue remaining on the surface gradually accumulates and increases as the number of uses increases. This residue reduces the release performance when the formwork is demolded and causes unevenness and voids on the concrete surface, causing physical adverse effects on the surface. This study aimed to evaluate the usability of polypropylene(PP) sheet with excellent release properties attached to the surface of aluminum formwork for walls. The pull strength required for formwork removal according to the number of reuses was measured, and the formwork and concrete surface conditions were visually inspected according to the type of PP sheet, whether it was cleaned, and whether release agent was applied. As a result of the study, As the reuses increased, the newly poured concrete was more easily attached to the concrete residue on the panel surface, expanding its area and showing a shape that was completely covered. The lower the pull value required for removing the formwork during formwork dismoling, the fewer the unevenness of the concrete surface after the formwork was demolded, and the result of measuring the rebound hardness of the concrete surface showed a high average rebound hardness.

https://doi.org/10.11112/jksmi.2025.29.3.20

노승지(Seung-Ji Noh) ; 안효준(Hyo-Joon An) ; 이종한(Jong-Han Lee)

Black-ice is a major winter road hazard, forming a thin and nearly invisible layer of ice on the road surface that is difficult for drivers to detect. The risk of black-ice increases during conditions such as sudden temperature drops or cooling after snowfall, making early prediction crucial for road safety. However, existing prediction methods often fail to fully capture rapid weather changes and road surface condition, highlighting the need for more advanced predictive models. This study proposes a black-ice risk prediction model that combines a Random Forest(RF) algorithm with a Long Short-Term Memory(LSTM) network. The RF model is employed to identify key variables that are highly correlated with black-ice formation. These selected variables are used as inputs to the LSTM model, which captures temporal patterns relevant to freezing events. Evaluation results confirm that the proposed model effectively predicts black-ice risk. The developed model has potential for integration into real-time road safety management systems. It is expected to contribute to the prevention of traffic accidents caused by black-ice.

https://doi.org/10.11112/jksmi.2025.29.3.27

오상훈(Sang Hoon Oh) ; 동재욱(Jae-Uk Dong)

The retention period and extension regulations for temporary buildings in South Korea vary by region, leading to legal inconsistencies and administrative discretion issues. While the Building Act Enforcement Decree sets a standard retention period of three years, local governments apply different extension rules?some limit extensions to one time (maximum six years), while others allow unlimited extensions, creating uncertainty and fairness concerns. This study examines the legal and policy challenges caused by regional differences, comparing South Korea’s system with Japan, which offer more standardized regulatory approaches. To resolve these issues, the study proposes national standardization of extension regulations, clearer legal criteria for approvals and rejections, and a structured classification for temporary buildings based on retention periods. Implementing these reforms would enhance regulatory consistency, fairness, and urban planning efficiency, reducing conflicts between building owners and administrative authorities.

https://doi.org/10.11112/jksmi.2025.29.3.35

김현식(Hyun-Sik Kim) ; 이강석(Kang-Seok Lee)

In this research, a novel diamond-shaped bracing method installed with a Laterally Layered Friction Damper (LLFD) to address the limitations of conventional vibration control systems is proposed with the aim of applying it to existing reinforced concrete buildings. First, the material performance and energy dissipation capacity of the LLFD were evaluated through material testing, and simultaneously, a diamond-shaped bracing system installed with LLFD, designed with consideration for facade aesthetics, was selected through a survey-based approach. Two full-scale, two-story reinforced concrete frame specimens, modeled after a reinforced concrete building lacking seismic detailing, were prepared: one as an non-strengthened control, and the other retrofitted with the proposed LLFD diamond-shaped bracing system. A pseudo dynamic testing was performed to investigate the effectiveness of the seismic rehabilitation, focusing on key response parameters such as maximum shear strength, maximum displacement, and earthquake damage degree. The results demonstrated that the LLFD diamond-shaped bracing system significantly improved lateral load resisting capacity and reduced story deformation, even under severe seismic intensities including 400 and 500 cm/s2.

https://doi.org/10.11112/jksmi.2025.29.3.47

유석형(Suk-Hyeong Yoo) ; 강대영(Dae-Young Kang)

Reinforced concrete (RC) walls are widely used in low-, mid-, and high-rise buildings due to their high stiffness and excellent lateral load resistance. The failure mechanism of RC shear walls is governed not only by their aspect ratio but also significantly influenced by the presence and configuration of openings. According to ASCE 41-17, walls with an aspect ratio greater than 3 are classified as flexure-controlled, those with a ratio less than 1.5 as shear-controlled, and those in between as flexure?shear controlled. When openings are introduced, wall-piers and wall-spandrels are formed, which cause stress concentrations and reduce both stiffness and strength. Previous earthquake damage reports and experimental studies have shown that these changes frequently result in shear failure mechanisms around openings, reducing the ductility and energy dissipation capacity of the structure and potentially leading to localized collapse. Despite this, most domestic studies in Korea have focused on flexure-controlled RC walls, while systematic studies of inelastic shear behavior in squat RC walls particularly those with openings remain insufficient. This lack of research presents limitations in assessing the realistic seismic performance of RC walls commonly applied in low-rise buildings. To address this gap, this study investigates the seismic response and fragility of squat RC walls with various opening locations and area ratios. Nonlinear time history analysis using inelastic shear wall elements was conducted, along with incremental dynamic analyses, to evaluate the damage distribution and failure patterns for each parameter. The results aim to provide essential data for performance-based seismic design and practical seismic assessment of RC wall systems in low-rise structures.

https://doi.org/10.11112/jksmi.2025.29.3.59

송정원(Jeong-Weon Song) ; 송진규(Jin-Gyu Song)

This study investigates the seismic strengthening effect of basalt fiber sheet reinforcement and develops a corresponding nonlinear analytical model. Cyclic loading tests and nonlinear analyses were conducted on four reinforced concrete columns: one unreinforced reference specimen and three specimens strengthened with basalt fiber sheets. Nonlinear analyses were performed using Perform-3D (a nonlinear structural analysis software). The strengthened columns exhibited approximately double the lateral strength and drift capacity compared to the unreinforced specimen and showed about nine times greater energy dissipation. The proposed nonlinear model demonstrated close agreement with the experimental results, confirming its validity for simulating the inelastic behavior of reinforced columns.

https://doi.org/10.11112/jksmi.2025.29.3.66

허인욱(In-Wook Heo) ; 다르한바트 할리오나(Khaliunaa Darkhanbat) ; 최승호(Seung-Ho Choi) ; 김성배(Sung-Bae Kim) ; 김강수(Kang-Su Kim)

This study presents an experimental and numerical investigation on the fire resistance performance of permanent steel formed beams. Two full-scale specimens were fabricated, and fire resistance tests were conducted. The vertical deflection and internal temperature distribution of the beams were analyzed as a function of fire exposure time. Based on the experimental results, a nonlinear finite element model was developed to evaluate the structural behavior under elevated temperatures. Using the verified model, a parametric analysis was performed to assess the effect of load ratio on fire resistance performance. The results showed that the beam with a width of 400 mm achieved the target 3-hour fire resistance performance when the load ratio was 0.5 or less, while the 800 mm wide beam satisfied the criteria for load ratios up to 0.8.

https://doi.org/10.11112/jksmi.2025.29.3.76

하수경(Soo-Kyoung Ha) ; 최기선(Ki-Sun Choi)

This study evaluated the bond strength performance of a quasi non-combustible external thermal insulation composite system (ETICS). Pull-off tests were conducted with reference to the ETAG 004 standard on sandwich-type insulation panels composed of calcium carbonate-based external finishing boards (RCB) and quasi non-combustible EPS and PIR insulation cores. The specimens were fabricated using two installation methods: post-installed bonding with adhesive and site-cast concrete. The post-installed specimens exhibited a wide range of failure resistances from 0.037 MPa to 0.140 MPa, with most failures occurring as cohesive rupture within the EPS and PIR cores. In contrast, the site-cast method demonstrated more stable bond performance with failure resistances ranging from 0.124 MPa to 0.140 MPa. The calculated minimal admissible bonded surface areas were 35.7% and 41.7% for the post-installed EPS and PIR systems, respectively, and 24.2% for the site-cast EPS system. These findings indicate that bond strength and installation reliability can vary significantly depending on the type of insulation and installation method, underscoring the importance of selecting an appropriate construction technique to ensure structural safety.