유리섬유강화폴리머(GFRP) 보강근은 굽힘부에서 크린클링에 의해 유효 단면이 물리적으로 감소하면서 강도 저하가 발생한 다. 현재 유한요소 모델링에서는 재료 강도만을 저감할 뿐, 이에 따른 강성 저하는 고려하지 않고 있다. 본 연구에서는 물리적 단면 손실을 직접 반영하는 등가 환산 단면법을 제안하고, ABAQUS를 이용하여 기존의 강도 감소법과 비교하였다. 3가지 직선부 직경(13, 16, 19 mm)에 대한 2차원 보 해석 결과, 정규화된 굽힘 인장강도는 직경 비에만 의존하여 하나의 2차 곡선으로 수렴되었다. 등가 환산 직경을 적용할 경우 축강성은 68∼76%, 휨강성은 47∼58%로 감소하였다. 콘크리트 방음벽 기초에 대한 3차원 비선형 해석 결 과, 강도 감소법은 인위적으로 낮춘 파단 기준에 의해 GFRP가 조기 파단함으로써 극한 하중을 약 11% 과소 평가하는 것으로 나타났 다. 등가 환산단면법은 GFRP 보강근 굽힘부의 유한요소 모델링에 있어 보다 물리적으로 합리적인 접근법을 제공한다.

As domestic traffic policies have shifted from vehicle-centric approaches to a ‘Safe Speed’ paradigm, the installation of roundabouts has surged. However, existing studies based on linear statistical models have failed to identify the complex non-linear interactions between geometric features and accident severity, limiting their ability to provide concrete design thresholds. To overcome the lack of traffic volume data, this study developed a geometry-based Design Capacity Index (DCI) and proposed a new analytical framework using the Equivalent Property Damage Only (EPDO) rate per unit capacity as the dependent variable. Utilizing a dataset of nationwide roundabouts (2007–2020), a grid search-optimized eXtreme Gradient Boosting (XGBoost) model and SHAP analysis were applied, achieving a 40.5 % performance improvement over linear baselines. The results revealed that circulatory roadway width was a dominant factor; contrary to the 'Road Diet' theory, ensuring 'Geometric Sufficiency' (wider lanes) proved more effective for safety in medium-to-large roundabouts. Furthermore, a 'Broad Optimal Zone' was identified within an inscribed circle diameter (ICD) of 35–70 m, while a 'Paradox of Scale' emerged beyond 70 m where safety benefits plateaued. Additionally, raised crosswalks served as essential offset measures, consistently reducing accident costs regardless of the intersection size. Based on these findings, this study provides empirical evidence for revising design guidelines to prioritize the 35–70 m ICD range and advocates for the mandatory installation of physical calming measures in oversized roundabouts.

This study proposes a surrogate model framework that integrates finite element analysis and deep learning to rapidly estimate equivalent material properties of patterned sheets. Conventional homogenization methods can only be applied after the pattern geometry has been finalized, requiring additional modeling and simulation. In contrast, the proposed approach establishes a surrogate model in advance, enabling the immediate estimation of equivalent material properties once the pattern geometry is defined. A dataset of 5,000 cases was generated using simulations, and Bayesian hyperparameter optimization was applied to improve model performance. The surrogate model achieved R² values above 0.99 for all target properties, confirming high internal consistency. Experimental validation with patterned STS304 specimens yielded meaningful results, with all errors remaining within 15%, which demonstrates the reliability of the proposed surrogate model despite minor deviations caused by fabrication imperfections and limited training data. Despite these limitations, the proposed system enables instant estimation of equivalent properties from pattern geometries, offering significant reduction in computational cost and design time. This approach enhances design reliability and provides a practical tool for the application of patterned materials in industrial engineering.

기후 변화로 인한 강우 강도의 증가로 도시 우수 배제시설의 설계 기준이 상향되고 있으나, 노후 하수관로는 오히려 변형과 통수 효율 저하 문제를 겪고 있다. 다양한 노후화 유형 중에서도 이음부 관 침하로 인한 관정렬 교란은 국부적인 역구배, 퇴적물 누적, 추가적인 손실수두를 유발하는 주요 요인이다. 본 연구에서는 관 침하가 배수 성능에 미치는 수리적 영향을 평가하기 위해, 경사 2°의 직경 600 mm 원형 우수관을 대상으로 전산유체역학 해석을 수행하였다. 해석 영역은 맨홀 간 40 m 하수관로 구간을 모델링하였으며, 그중 10 m 구간은 경사 변형이 존재하도록 설정하였다. 상류단(P1)과 하류단(P2) 간의 압력 차이를 이용해 국부 손실수두(Δhloc)와 손실계수(K)를 계산하였고, 수정된 Manning 식을 통해 등가 조도계수(nnew)를 산정하였다. 해석 결과, 관 처짐각이 0°에서 14°로 증가함에 따라 압력 손실은 0 Pa에서 1,298 Pa로, 손실계수(K)는 0.00에서 0.293으로 증가하였으며, 이때 등가 조도계수(nnew)는 약 6% 상승하였다. 본 연구결과는 노후 하수관로의 관침하 현상이 에너지 손실과 수리 저항을 크게 증가시킴을 보여주며, 도시 배수 시스템에서 관 침하로 인한 성능 저하를 정량적으로 평가할 수 있는 근거를 제시한다.

소프트 로보틱스는 기존의 강체 시스템에 비해 향상된 유연성, 적응성, 그리고 안전성을 제공하며, 이는 특히 인간과의 상호작용이 나 비정형 환경에서의 응용에 적합하다. 소프트 로봇을 위한 다양한 구동 메커니즘 중 형상기억합금(SMA)-섬유 액추에이터는 경량 성, 저소음 작동, 높은 에너지 밀도 등의 장점으로 유망한 솔루션으로 부상하고 있다. 본 연구에서는 P-루프 형태로 구성된 SMA 기반 섬유 액추에이터를 사용하여 제작된 소프트 니트 그리퍼의 구동 성능 및 굽힘 거동을 해석하였다. 그리퍼의 변형 거동을 모델링하고 예측하기 위해 ABAQUS 환경에서 등가 유닛 셀(EUC) 모델을 활용하여 소프트 니트 그리퍼와 EUC 모델 간의 굽힘 성능을 분석 및 비 교하였다. 해당 모델은 전기 자극에 따른 형상기억 효과로 인한 대변형을 시뮬레이션하기 위해 기하학적 비선형성을 포함하였다. 분 석에는 P-루프 구조에서 나타나는 굽힘 거동이 포함하였으며, 이는 효과적인 파지 및 조작을 위해 중요한 요소이다. 실험적 검증은 다 양한 전압을 그리퍼에 인가하고, 그에 따른 굽힘 각도를 측정함으로써 수행하였다. 실험 결과, 인가 전압이 증가함에 따라 굽힘 각도 도 유의미하게 증가하였으며, 최대 180°까지의 변형이 관찰되어 액추에이터의 우수한 성능을 입증하였다. EUC 모델을 기반으로 한 수치 해석 결과는 최대 굽힘 각도에서 단 5%의 오차 범위를 보이며 실험 결과와 매우 근접한 양상을 나타내어, 제안된 모델링 접근법 의 정확성과 신뢰성을 확인하였다. 본 연구는 EUC 모델이 SMA-섬유 기반 소프트 그리퍼의 구동 거동을 효과적으로 예측할 수 있음 을 보여주었으며, 차세대 소프트 액추에이터의 설계 및 성능 향상을 위한 중요한 통찰을 제공하였다. 또한, 형상에 밀착되며 유연한 작동이 요구되는 현대 소프트 로보틱스 및 생체의료 응용 분야에서 SMA-섬유 복합재의 활용 가능성을 확인하였다.

This study investigated the vertical displacement behavior caused by differential drying shrinkage in jointed concrete pavements. This study proposed a method to convert this behavior into an equivalent linear temperature difference for structural analysis. Controlled experiments were conducted under varying humidity and airflow conditions to simulate pavement environments. The test results showed that a lower relative humidity and added airflow significantly increased the vertical displacement, particularly at the slab edges. A 3D finite element model using ABAQUS was developed to analyze the behavior and derive the equivalent linear temperature difference that increased with curing age and varied notably with environmental conditions. These findings highlighted the impact of early-age environmental factors on the shrinkage behavior and suggested that the proposed method offered a practical approach for predicting deformation without repeated physical testing.

본 논문에서는 다양한 FDM 출력 공정 변수에 따라 결정되는 출력물의 비등방 물성을 구조 해석 과정에서 반영할 수 있는 개선된 해석 방안을 제안하였다. 출력 공정 변수에 대한 물성의 민감도를 분석하였으며, 실제 출력물에 대한 인장 시험을 통해 적층 방향에 따라 이방 특성이 도출됨을 확인하였다. 또한, 출력물에 대한 단면 분석을 통해 적층 레이어 높이 및 필라멘트 채움률 등의 공정 변수 들이 내부 공극 특성에 영향을 미치며, 결과적으로 출력물의 이방 특성이 유발된다는 사실을 확인하였다. 나아가, 적층 방향, 적층 레 이어 높이, 필라멘트 채움률 등이 동시에 고려된 균질화 모델 분석을 통해 출력 과정에서 발생되는 내부 공극 분포가 출력물의 기계적 거동 특성에 미치는 영향을 규명하고자 하였다. 수치 예제로써 로어 컨트롤 암 출력물의 비등방 특성이 반영된 구조 해석을 수행하였 으며, 이를 통해 FDM 출력물 설계 과정에서의 개선된 해석 방안의 타당성을 검증하였다.

The turbine wheel plays a crucial role in operating turbines, and with recent advancements in technology, the performance requirements for turbine wheels have significantly increased. Consequently, it is essential to predict failure speeds, as turbine wheels must maintain high stability and reliability under harsh operating conditions. In this study, only the centrifugal loads generated by rotati were considered, excluding conditions such as temperature and pressure. A round-shaped fuse section was applied to the turbine wheel, and the stresses induced by variations in shape were analyzed to predict failure speeds. The results obtained using the Hallinan criteria were compared with the results from finite element analysis (FEA) to validate the predicted failure speeds, showing good agreement between the two methods.

This study aims to calculate the passenger car equivalent (PCE) of heavy vehicles on one-lane exit sections of underground roads. Traffic-flow simulations were performed using the VISSIM software program. The scenarios were designed under varying conditions, including design speeds of 40 and 50 km/h, slope gradients ranging from 3% to 9%, and heavy vehicle proportions between 5% and 40%. The mixed-traffic flow capacity was calculated for each scenario at the threshold levels, and the PCE was estimated based on the two capacity conditions. The results revealed that the PCE decreased at lower design speeds. For slopes less than 6% at a design speed of 40 km/h, and for slopes less than 4% at 50 km/h, the PCE remained consistent across all conditions. Single-lane exit sections are often employed on underground roads because of congestion and structural constraints. However, when heavy vehicles are present in these sections, the overall traffic flow is dictated by the speeds of the heavy vehicles. To address this issue, the implementation of variable or temporary two-lane exit sections has been proposed to enhance traffic flow and capacity.

The purpose of this study was to optimize the design of asphalt concrete pavements for Jeju Island by considering the regional characteristics of the island. This study employed an MEPDG program to determine the allowable traffic loads for class 4 vehicles by considering the axle loads, climate, and material properties. Samples of basalt asphalt concrete from Jeju were used to measure the dynamic modulus for material property estimation. The climate input was based on 30-year climate data from Jeju. The thicknesses and moduli of the subgrade, subbase, and asphalt layers were incorporated into the design. The regression-analysis program SPSS was used to develop a regression equation for the overlay design, factoring in the modulus and thickness ratios between the existing and overlay asphalt layers. A pavement-thickness design formula tailored to Jeju's characteristics was derived. An equivalent single-axle load factor (ESALF) formula was developed to facilitate traffic-load estimation for different roads, enabling the easy incorporation of varying traffic volumes into the design. The ESALF formula demonstrated a high correlation with the pavement thickness, subgrade conditions, and axle loads, whereas the pavementthickness design formula exhibited strong correlations with the pavement thickness, subgrade state, thickness ratios, and modulus ratios. The use of basalt aggregates in asphalt concrete pavements provides an economically viable and technically sound solution for Jeju. The proposed design methodology not only reduces costs but also enhances pavement performance and road safety. The developed formulas offer flexibility in adjusting designs based on specific traffic conditions, providing optimal pavement solutions for different road categories.

정온한 생활환경의 보전과 국민 건강의 보호를 위해 소음에 대한 환경기준을 환경정책기본법에 따라 일반지역과 도로변지역으로 구 분하여 관리하고 있다. 그 중 도로변지역에 있는 주거지역은 주간시간대 65 dBA, 야간시간대 55 dB 이하로 환경소음을 관리하여야 한 다. 그러나, 심화된 도시화에 따라 주거건축물의 밀도는 보다 높아지고, 도심 내 간선도로의 고속화로 주거지역에 대한 도로소음의 영 향이 증가되어가고 있다. 소음진동관리법에서는 방음시설의 설치 등의 조치를 의무화하고 있으며, 이에 따라 방음벽, 방음터널 등 다 양한 방음시설이 소음저감 대책으로서 현장의 여건에 따라 사용되고 있다. 최근, 배수성 아스팔트 포장이 노면에서의 흡음에 따른 타 이어-노면 간의 마찰소음 저감 효과를 바탕으로 손쉽게 적용할 수 있는 방음대책의 하나로 활용되고 있다. 하지만, 저소음 아스팔트 포장이 일반 아스팔트 포장에 비해 환경소음을 저감시킬 수 있는지 정량적으로 평가하는 것이 매우 어려운 상황이다. 최근 타이어-노 면 간의 마찰소음을 정량적으로 평가할 수 있는 CPX 측정방법이 KS I ISO 11819-2로 표준화되어 국토부의 ‘배수성 아스팔트 콘크리 트 포장 생산 및 시공지침’ 중 소음 측정방법에도 인용되어 있다. 하지만, CPX 방법은 정속 주행시 환경의 영향을 통제한 상태에서 근접 소음만을 측정하기 때문에, 포장 종류나 경년변화에 따른 상대적인 차이를 정량화하는 것은 유리하지만, 환경기준에 따른 소음저 감도를 직접적으로 비교할 수 없는 단점이 있다. 이에 따라, 본 연구에서는 CPX 측정방법으로 도출한 포장구간별 소음저감량과 환경 소음 평가의 기준이 되는 갓길에서 측정한 등가소음간의 상관관계 분석을 통해, 환경소음 관리 및 도로소음 평가를 위한 CPX 측정결 과의 활용방안에 대해 고찰하였다.

Electric-propulsion systems for ships, also known as electric propulsion devices, represent the current direction of development for maritime power. Issues concerning the environment and fuel economy have compelled the maritime transport sector to seek solutions that reduce emissions and improve fuel efficiency. In this process, power electronics technology plays a significant role in the propulsion systems of ships. Selecting an efficient battery system is of great importance for enhancing the cruising range of yachts and minimizing environmental impact. The battery model is crucial for revealing the working principles of batteries, and it is extremely critical for the application and development of battery technology. The Battery Management System (BMS) serves a crucial regulatory function, optimizing both the safety and performance of battery cells. Central to its operation is the precise estimation of the battery's State of Charge (SOC), a process dependent on an exacting battery model. This system not only enhances longevity and reliability but also ensures that energy storage solutions meet high standards of efficacy. This study focused on testing the impedance characteristics of lithium-sulfur batteries (LSB) at various SOC points and establishing first- and second-order RC equivalent circuit models. The model parameters were identified through experimental data. Subsequently, a simulation platform was constructed using MATLAB/Simulink to simulate the behavior of LSB under a constant current discharge condition. The simulation results showed that the second-order RC model had significantly lower errors than the first-order model, demonstrating higher accuracy. These achievements can provide technical support for the research of energy storage systems in the green aviation and maritime industries.

In Korea, five major ports have been designated as sulfur oxide emission control areas to reduce air pollutant emissions, in accordance with Article 10 of the “Special Act on Port Air Quality” and Article 32 of the “Ship Pollution Prevention Regulations”. As regulations against vesseloriginated air pollutants (such as PM, CO2, NOx, and SOx) have been strengthened, the Ministry of Oceans and Fisheries(MOF) enacted rules that newly built public ships should adopt eco-friendly propulsion systems. However, particularly in diesel–electric hybrid propulsion systems,the demand for precise control schemes continues to grow as the fuel saving rate significantly varies depending on the control strategy applied. The conventional Power Take In–Power Take Off(PTI–PTO) mode control adopts a rule-based strategy, but this strategy is applied only in the low-load range and PTI mode; thus, an additional method is required to determine the optimal fuel consumption point. The proposed control method is designed to optimize fuel consumption by applying the equivalent consumption minimization strategy(ECMS) to the PTI–PTO mode by considering the characteristics of the specific fuel oil consumption(SFOC) of the engine in a diesel–electric hybrid propulsion system. To apply this method, a specific fishing vessel model operating on the Korean coast was selected to simulate the load operation environment of the ship. In this study, a 10.2% reduction was achieved in the MATLAB/SimDrive and SimElectric simulation by comparing the fuel consumption and CO2 emissions of the ship to which the conventional rule-based strategy was applied and that to which the ECMS was applied.

A program was written that calculates the contact point and rolling radius difference by considering the lateral displacement of the wheelset with respect to the rail. The characteristics of the equivalent conicity were analyzed according to the distribution characteristics of wheelset lateral displacement using the calculated rolling radius difference. The standard deviation value representing the characteristics of the wheelset lateral movement should be appropriately applied considering the range of the lateral wheelset displacement. If a small standard deviation value is applied when the lateral displacement increases during actual driving condition, the equivalent conicity could be underestimated, which may cause a problem in determining a reliable stability of the railway vehicle.

When performing finite element analysis using materials with porosity the porosity shows different mechanical properties from the existing mechanical properties of the existing base materials. In this study the equivalent properties were calculated and verified by applying the representative volume element (RVE) method and assuming that the material with porosity is a 2D orthotropic material. In case of finite element analysis using porous material or composite material, it is inefficient to perform the analysis through material modeling. Based on the element volume and element stress values ​​derived using the finite element analysis program, the representative stress values ​​and elastic modulus matrix were calculated using Python. In addition, equivalent properties were derived using the calculated elastic modulus matrix. The pores were simulated by etching a thin plate specimen made of STS304 material in a certain pattern, and the elastic modulus and Poisson's ratio were measured through a UTM and compared with simulation results. It was confirmed that an error of 7.028% for elastic modulus and 10% for Poisson's ratio occurred, and through this, the validity of this simulation was verified.

The demand for materials with porosity is steadily increasing and the need for porous materials is increasing in fields such as chemical engineering and energy storage. In order to minimize trial and error, verifying design validity through finite element method at the design stage has the advantage to verify design validity with low cost. However there are limitations in finite element analysis using porous materials. In this study calculating the equivalent mechanical properties reflecting the porosity was carried out, and the first step was the isotropic elasticity in plane stress condition. The equivalent elastic modulus and the equivalent Poisson's ratio were derived through simulation. Assuming that the voids exist in a two-dimensional symmetrical shape and a constant distribution, the unit cell was defined and the equivalent mechanical properties were calculated. The specimen with same condition were measured through a universal test machine (UTM), the elastic modulus and Poisson's ratio were measured. The similarity between the value obtained through the simulation and the value measured through the experiment was under 5%, so the validity of this simulation was verified. With this result, FEM with porous materials will be used for design.

A corrugated steel plate wall (CSPW) system is advantageous to secure the strength and stiffness required for lateral force resistance because of its high out-of-plane stability. It can also stably dissipate large amounts of energy even after peak strength. In this paper, a preliminary study has been carried out to use the CSPW system in the seismic retrofit of existing reinforced concrete (RC) moment frame buildings. The seismic performance for an example building was evaluated, and then a step-by-step retrofit design procedure for the CSPW was proposed. An equivalent analytical model of the CSPW was also introduced for a practical analysis of the retrofitted building, and the strengthening effect was finally evaluated based on the results of nonlinear analysis.