Earticle

Structural failures in steel connections under extreme loading conditions, such as earthquakes or unexpected impact loads, can lead to catastrophic progressive collapse. Among various connection types, the T-stub connection is a fundamental component whose failure mode is highly sensitive to the geometric configuration of its bolts. This study proposes an automated parameter optimization framework for bolt layouts in H-beam T-stub connections to mitigate prying action and enhance structural resilience against disasters. To achieve a high-fidelity analysis, a nonlinear finite element (FE) model was developed using Abaqus. The model incorporates an H-400x200x8x13 section and M20 (F10T) high-strength bolts, accounting for complex surface-to-surface contact, material plasticity, and large deformation effects. To transition from traditional trial-and-error design to a datadriven safety management approach, the FE model was integrated with Isight to automate the optimization of critical design variables: the gauge distance (g) and edge distance (e). The optimization process employed the Optimal Latin Hypercube design of experiments (DOE) to sample the design space efficiently. A surrogate model was subsequently constructed using Response Surface Methodology (RSM) to analyze the sensitivity of the structural response to bolt positioning. The results demonstrate that optimizing the bolt coordinates can significantly reduce the prying force, thereby preventing premature bolt fracture and increasing the energy dissipation capacity of the connection. From a disaster information perspective, this research provides a quantitative foundation for Digital Twin-based structural health monitoring. By establishing a relationship between geometric parameters and failure limits, the proposed methodology enables more accurate safety assessments of existing infrastructure. This study contributes to the development of intelligent disaster prevention systems by integrating advanced numerical simulation with automated optimization techniques to ensure the structural integrity of steel-framed buildings.

부분구조법(部分構造法)으로 프리스트레스드 콘크리트 원자로격납건물(原子爐格納建物)의 지진에 대한 확률위험도분석이나 내진 안전여유평가시 상부구조에 관한 입력자료(入力資料)가 되는 구조물(構造物)의 고유전동수와 구조물 상부에서의 최대가 속도값의 구조변수(構造變數)에 대한 변동성이 연구되었다. 본 연구는 먼저 구조모델의 고유진동수에 가장 큰 영향을 미치는 구조변수를 결정하기 위하여 각 구조변수(構造變數)의 상대적(相對的) 민감도(敏感度)를 분석(分析)하였고, 각 변수의 결정에 포함될 수 있는 불확실성(不確實性)의 정도를 고려하여 Monte Carlo 수치모형실험을 수행하였다. 최대 가속도값의 변화는 직접적분(直接積分)에 의한 시간이력곡선법으로 분석되었다. 연구결과로 첫번째모드의 고유 진동수와 건물 정상부의 최대가속도값은 각 변수중 탄생계수의 영향을 가장 크게 받으며, 결정론적 방법으로 구한 값과 비교할 때 확률론적 방법으로 구한 값(평균+표준편차)은 (+)12% 정도 변함을 알 수 있다. 또한 휨강성의 불확실성을 고려하면 동적응답은 (-)4%~(+)14% 정도 달라진다.

The variations of the natural frequencies and the peak response acceleration at the top of prestressed concrete reactor building due to random variability and/or model uncertainty of structural parameters are studied. The results may be used as essential input parameters in seismic probabilistic risk assessment or seismic margin assessment of the reactor building. The sensitivity test of each structural parameter is first performed to determine the most influential parameter upon the natural frequency of structure model. Then Monte Carlo simulation technique is applied to evaluate the effect of parameter variation on the natural frequencies and the peak response acceleration. The acceleration time history is obtained by direct integration scheme. As the study results, it is found that the fundamental natural frequency and the peak response acceleration at the top of the building are most strongly affected by Young's modulus among the structural parameters, in which the value of mean plus one standard deviation obtained by probabilistic approach deviates up to about (+)12% from the result of deterministic method. Considering the uncertainty of flexural rigidity, the structural responses vary in range of (-)4%~(+)14%.

The working space is one of the important indexes to measure the working capability of parallel mechanism. In this paper, the working space of a new type of 3-PRS parallel mechanism is studied. In the beginning, a novel 3-PRS parallel mechanism is proposed with the kinematics analyzed, and then the working space and volume are obtained by search algorithm, and the working space is drawn using MATLAB. Finally, the influence of the structural parameters on the working space is discussed, which provide theoretical basis for parameter optimization.

With the rapid development of high-repetition rate X-ray free electron laser (FEL), the issues of thermal deformation and stress in optical elements, such as mirrors, under high thermal loads have become increasingly prominent. Traditional design optimization relies on repeated Thermal-Structural coupling finite element simulations, which face bottlenecks, including low optimization efficiency and insufficient utilization of historical data. This paper proposes an optimization approach that combines PyAnsys parametric scanning with deep learning-based surface shape prediction, aiming to enhance the optimization efficiency of mirror cooling structures and support parameters. A parametric simulation platform is constructed using PyAnsys Geometry and PyMechanical, enabling the rapid generation of model variants within 30 s. Additionally, a historical database containing geometric features, physical parameters, and operating conditions is established. Furthermore, a deep neural network-based mirror height error prediction model is developed, and experiments show that the model can predict surface height errors with RMS <0.08 nm in water-cooled silicon mirror cases. This method has the potential to shorten the traditional design iteration cycle to a few hours, significantly enhancing data reuse. Future work should focus on incorporating incremental learning and physical constraints to improve the reliability of extrapolation for multi-condition scenarios and refine the optimization loop.

The space reactor is the primary energy supply for future space vehicles and space stations. The radiator is one of the essential parts of a space reactor. Therefore, the research on radiators can improve the heat dissipation power, reduce the quality of radiators, and make the space reactor smaller. Based on MOOSE multi-physics numerical calculation platform, a simulation program for the combination of heat pipe and fin at the end of heat pipe radiator is developed. It is verified that the calculation result of this program is accurate and the calculation speed is fast. Analyze the heat transfer characteristics of the combination with heat pipe and fin, and obtain its internal temperature field. Based on the calculation results, the influence of structural parameters on the heat dissipation power is analyzed. The results show that when the fin width is 0.25 m, fin thickness is 0.002 m, condensing section length is 0.5425 m and heat pipe radius is 0.014 m, the power-mass ratio is the highest. When the temperature is 700K-900K, the heat dissipation power increases 41.12% for every 100K increase in the operating temperature. Smaller fin width and thinner fin thickness can improve the power-mass ratio and reduce the radiator quality.

Estimation of uncertain parameters is required in many engineering problems which involve probabilistic structural analysis as well as prognosis of existing structures. In this case, Bayesian framework is often employed, which is to represent the uncertainty of parameters in terms of probability distributions conditional on the provided data. The resulting form of distribution, however, is not amenable to the practical application due to its complex nature making the standard probability functions useless. In this study, Markov chain Monte Carlo (MCMC) method is proposed to overcome this difficulty, which is a modern computational technique for the efficient and straightforward estimation of parameters. Three case studies that implement the estimation are presented to illustrate the concept. The first one is an inverse estimation, in which the unknown input parameters are inversely estimated based on a finite number of measured response data. The next one is a metamodel uncertainty problem that arises when the original response function is approximated by a metamodel using a finite set of response values. The last one is a prognostics problem, in which the unknown parameters of the degradation model are estimated based on the monitored data.

Procedures for estimation of axial or flexural rigidities of bridge members by neural networks are shown. To treat large scale structures containing many unkwon parameters, substructuring concept is introduced. The measurement points are selected considering the sensitivity of the element stiffnesses of interest. Utilization of relative mode vectors is found to be very effective for the local parameter estimation. Then, the study focuses on the method to obtain the training set enough to represent structures. It is shown that noise injection is effective to reduce the estimation errors caused by measurement noise. Verification of the present method is carried out using a cable-stayed bridge model.

The processing shrinkage of polyester filament fabrics in relaxed and pre-set state give a direct influence on the mechanical and physical properties of the fabrics which effect fabric hand. This paper surveys correlation between fabric structural parameters such as warp and weft densities of the fabrics, and weft twist and processing shrinkage of the fabrics. For the purpose of this objective, specimens with various warp and weft densities, twists, and weft linear densities are prepared for the plain and satin weaves, respectively. All the specimens were processed into finishing process, and processing shrinkage in the relaxation and pre-set processes were measured.

As computer capability and test skill become more and more advanced, finite element method and modal test are being widely applied in engineering design. In order to correlate and reconcile the inevitable discrepancies between the analytical and experimental models, many techniques have been developed. Among these methods, multiple-system methods are known as the effective tools in that they can supply the rich modal data available which are experimentally obtained. These abundant modal data can help structural system parameters estimated well. Multiple-system methods can be classified into the structural modification methods and feedback controller methods. The structural modification methods need the physical attachment of structures and their concept may limit the application of them. To overcome this drawback, the feedback controller methods are addressed which enable us to get more modal data without the structural change. Mode decoupling controller(MDC), one of them, is to use acceleration out)ut feedback to perturb an open-loop system. The output feedback controller generally cannot guarantee the stability of a closed-loop system. However, MDC can solve this problem under the certain constraints. So far, MDC utilizes accelerations as the sensor signals. In this research, strain sensors are going to be picked up to apply to the MDC. Strain output is recently used for structural system identification due to the drastically improved and miniaturized strain sensor. In this paper, we show that the MDC using strain output has differences compared with acceleration output in estimating the structural system parameters. The associated simulation is performed to demonstrate the above mentioned characteristics.

The shape of K-R curve for an ideally brittle material is flat because the surface energy is an unvaried material property. However, the K-R curve can take on a variety of shapes when nonlinear material behavior accompanies fracture. By the way, a general metallic material is nonlinear, structural steel is such. Therefore, the J-R curve form J-integral value instead of K parameters can be used to evaluate elastic-plastic materials with flaws in terms of ductile fracture that can be significant to design. In this paper, R-curve behaviors form K and J parameter is considered for the precise assessment of fracture analysis, in case of JS-SS400 steels.

In this study, design parameter exploration based on finite element analysis was performed to find the optimal shape of bellows, the key component of compressor-embedded refueling tank for a newly developed hydrogen refueling station capable of high-pressure charging above 900 bar. In the design parametric study, the design variables took into account the bellows shapes such as contour radius and span spacing, and the response factors were set to the maximum stress and the gap in the contact direction. In the shape design of the compressor bellows for hydrogen refueling station considered in this study, it was found that adjusting the contour span is an appropriate design method to improve the compression performance and structural safety. From the selection of optimal design, the maximum stress was reduced to 49% compared to the initial design without exceeding the material yield stress.

The effect of twist parameters on the structure and properties of OE friction yarn has been investigated. The produced samples were three blended yarns of 100 % cotton, 65% cotton/35 % polyester and 65% cotton/35 % acrylic with ten different twist parameters. Yarn properties such as breaking stress, breaking strain and fiber slip were evaluated. A scheme of fiber classification that characterizes the special shapes and configurations of in OE friction yarns is proposed. Under this scheme, fault fibers are grouped into five different catagories ;hooked, looped, V-shaped, folded and entangled fibers. Data on fiber configurations shows a decrease in the number of fault fibers with increasing twist parameter. Yarn breaking stress shows an increase with increasing twist parameter, but breaking btrain has slightly decreased with increasing twist parameter. Furthermore, the fiber slip related to yarn stability shows rapidly decreasing trend with increasing twist parameter and the twist efficiency in the OEfriction spinner has about 20-30% by change in materials and twist parameters.

철도교량은 활하중의 비중이 크고 선로라는 정해진 경로를 주행하는 주기성 강한 열차 하중의 재하로 인하여 정확한 동적특성 파악이 중요하다. 이 논문에서는 기존에 개발된 가장 대표적인 모달해석 기법인 PS, FDD, p-LSCF, SSI BR 및 SSI CVA의 철도교량에 대한 적용성을 검토하고 성능 비교를 통하여 장단점을 분석하였다. 또한 상대적으로 진폭이 크나 지속시간이 짧은 철도교량에 대한 하나 이상의 측정데이터가 존재할 때, 보다 정확한 모달파라미터 산정을 위한 방법에 대한 검토도 수행하였다. 검토는 강재-콘크리트 합성 슬래브교량에 대한 수치해석 모델을 이용하였으며, 해석프로그램은 ABAQUS를 사용하였다.

Since the railroad bridge is subjected to the heavy and periodic live load, which runs through a fixed path called the track, it is important to accurately identify dynamic properties. In this paper, the applicability of existing representative modal analysis methods including PS, FDD, p-LSCF, SSI BR and SSI CVA to a railroad bridge is examined and relative performance is compared. Also, considering the characteristics of a railroad bridge which has vibration of relatively high amplitude but short period, a method to obtain more accurate modal parameter estimates is studied when more than single response measurement set is available. The review is performed using a numerical model for a steel-concrete composite slab bridge and a commercial finite element analysis program, ABAQUS.

As for the safety evaluation of existing large-scale structures, methods for estimation of the structural and dynamic properties are studied. Sequential prediction error method in time domain and improved FRF estimator in frequency domain are comparatively studied. For this purpose, impact tests of 2 bay 3 floor steel frame structure are performed. Results from both methods are found to be consistent to each others, however those from the finite-element analysis are slightly different from experimental results.

본 연구는 혼합 이노베이션(mixture innovation) TVP-VAR 모형을 이용하여 지난 30년 기간의우리나라 통화정책 효과 전달체계의 구조적 변화를 분석하였다. 첫째, 최근의 기간으로 올수록통화충격에 대한 생산과 인플레이션의 충격반응이 약화되는 추세가 발견되었다. 둘째, 통화충격에대한 통화정책의 반응은 최근 보다는 초기 표본기간에 더 강하고 지속적이었으며 이 기간 통화당국이 경기안정화 이외에 다른 요인들에 더욱 반응하였던 것으로 나타났다. 따라서 생산증가율및 인플레이션의 수준과 변동성의 장기 완화추세는 주로 통화정책 운영기조 변화와 이에 따른통화정책 효과의 전달체계의 구조적 변화에 기인한 것으로 평가된다. 마지막으로 두 차례 경제위기기간에 대한 분석결과, 강력한 확장적 통화정책이 위기 탈출에 도움이 된 것으로 나타났다. 이상과 같은 분석결과는 통상적인 선형 VAR 모형을 이용한 통화정책 효과의 평가에는 그 한계가있다는 것을 의미한다.

Using the TVP-VAR with mixture innovation, this study evaluates structural changes in transmission mechanism of monetary policy in Korea over the past three decades. First, our impulse response analysis indicates that the effects of monetary shocks on output and inflation have weakened in recent periods relative to earlier periods. Second, policy response to monetary shocks is stronger and more persistent in earlier periods and monetary authority responds more to factors other than output and inflation. These results imply that the observed long moderation of output growth and inflation over the three decades is mostly attributable to structural changes in monetary transmission mechanism in association with operational regime changes in monetary policy. Lastly, the analysis indicates that strong monetary expansions are effective policy responses in times of economic crisis. The results imply that policy analysis in Korea using a conventional linear VAR model may be misleading.

강-콘크리트 편개형 방폭문은 외피 구조로서의 강재 박스와 내부의 철근콘크리트 슬래브 부재로 구성된 방호 구조물이다. 국내 방폭문 설계의 경우 폭압의 크기, 철근량 및 강박스의 강판두께와 같은 설계변수의 변화가 구조거동에 미치는 영향에 대해서 연구결과가 많지 않은 관계로 방폭문의 구조가 효율적으로 설계되지 않고 있다. 본 연구에서는 배근 간격 및 강재 박스의 강판 두께, 하중조건 등을 변수로 하여 유한요소 해석에 의한 구조거동 특성을 분석하였으며, 또한 방폭문의 구조성능을 구분하기 위해 산정되는 회전연성도 및 변위연성도를 재검토하고자 하였다. 유한요소해석 결과에 따르면, 배근 간격을 변수로 할 때 보다 강재 박스의 강판 두께가 변할 경우가 처짐과 같은 구조거동에 있어서 더 큰 변화를 나타내고 있음을 알 수 있었다. 이와 같은 결과는 외피의 강재 박스의 강판 두께를 증가시킬 때 방폭문에 흡수된 변형 에너지가 더 큰 폭으로 감소하고, 결과적으로 전체적인 구조거동으로서의 처짐이 더 작게 발생하기 때문인 것으로 분석되었다. 또한, 방폭문의 구조성능을 구분하기 위한 방법으로서 회전 연성도 및 변위 연성도를 비교한 결과, 해석 대상 방폭문들의 성능은 회전 연성도 1도 및 변위 연성도 3을 기준으로 분류될 수 있었다. 폭발압에 대한 방폭문의 손상 수준을 분류하기 위해서는 향후 다수의 폭발시험 및 해석적 연구가 필요할 것으로 사료된다.

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.