This study reports an experimental and analytical exploration of concrete columns laterally confined with Fe-based shape-memory alloy (Fe-SMA) spirals. For performing experiments, Fe-SMA rebars with a 4% prestrain and diameter of 10 mm were fabricated and concrete columns with internal Fe-SMA spiral reinforcement were constructed with a diameter of 200 mm and height of 600 mm. An acrylic bar with an attached strain gauge was embedded in the center of the specimen to measure local strains. Experimental variables encompassed the Fe-SMA spiral reinforcement, spacing, and activation temperature. Uniaxial compression tests were conducted after applying active confinement to the concrete columns through electrical-resistance heating. Notably, as the Fe-SMA spiral spacing decreased, the local failure zone length and compressive fracture energy of the prepared specimens increased. Additionally, a model incorporating compressive fracture energy was proposed to predict the stress–strain behavior of the. This model, accounting for active and passive confinement effects, demonstrated accurate predictions for the experimental results of this study as well as for previously reported results.

KAERI has planned to carry out a series of dynamic tests using a shaking table and time-history analyses for a channel-type concrete shear wall to investigate its seismic performance because of the recently frequent occurrence of earthquakes in the south-eastern parts of Korea. The overall size of a test specimen is ×× 2500 mm×3500 mm×4500 mm, and it consists of three stories having slabs and walls with thicknesses of 140 mm and 150 mm, respectively. The system identification, FE model updating, and time-history analysis results for a test shear wall are presented herein. By applying the advanced system identification, so-called pLSCF, the improved modal parameters are extracted in the lower modes. Using three FE in-house packages, such as FEMtools, Ruaumoko, and VecTor4, the eigenanalyses are made for an initial FE model, resulting in consistency in eigenvalues. However, they exhibit relatively stiffer behavior, as much as 30 to 50% compared with those extracted from the test in the 1st and 2nd modes. The FE model updating is carried out to consider the 6-dofs spring stiffnesses at the wall base as major parameters by adopting a Bayesian type automatic updating algorithm to minimize the residuals in modal parameters. The updating results indicate that the highest sensitivity is apparent in the vertical translational springs at few locations ranging from 300 to 500% in variation. However, their changes seem to have no physical meaning because of the numerical values. Finally, using the updated FE model, the time-history responses are predicted by Ruaumoko at each floor where accelerometers are located. The accelerograms between test and analysis show an acceptable match in terms of maximum and minimum values. However, the magnitudes and patterns of floor response spectra seem somewhat different because of the slightly different input accelerograms and damping ratios involved.

The estimation of heat source model is very important for heat transfer analysis with finite element method. Part I of this study used adaptive simulated annealing which is one of the global optimization algorithm for anticipating the parameters of the Goldak model. Although the analysis with 3D model which depicted the real situation produced the correct answer, that took too much time with moving heat source model based on Fortran and Abaqus. This research suggests the procedure which can reduce time with maintaining quality of analysis. The lead time with 2D model is reduced by 90% comparing that of 3D model, the temperature distribution is similar to each other. That is based on the saturation of heat transfer among the direction of heat source movement. Adaptive simulated annealing with 2D model can be used to estimate more proper heat source model and which could enhance to reduce the resources and time for experiments.

Anticipation of welding deformation with finite element method is a very interested topic in the industries, adequate heat source model is essential for concluding reasonable results. This study is related to estimate the parameters of Goldak heat source model, and global optimization algorithm is applied to this research. The heat affected zone (HAZ) boundary line of bead on plate (BOP) welding is used as the target, parameters of heat sources are used as the variables. Adaptive simulated annealing is applied and the optimal result is obtained out of 1,000 candidates. The convergence of finite element method and the global optimization is meaningful for estimation of welding deformation, which could enhance to reduce the resources and time for experiments.

이 논문에서는 경계반력법을 이용한 비선형 지반-구조물 상호작용 해석을 위해 LS-DYNA나 MIDAS/Civil 등의 유한요소해석 프로그램과 연계하는 방법을 제시하였다. 경계반력법 적용시 유한요소프로그램에서 구조물과 지반은 선형 또는 비선형 유한요소를 이용하여 모델링하였다. 유한요소의 해석모델 외부의 무한영역으로 전달되는 탄성파를 최대한 흡수하기위해 유한요소 모델의 외측에 LS-DYNA의 경우에는 PML(Perfectly Matched Layer) 요소를, MIDAS/Civil의 경우에는 점성감쇠-스프링 요소를 적용하였다. 비선형 유한요소는 구조물영역에만 적용되는 것으로 가정하였다. 이 연구에서는 입사지진파에 의한 경계반력은 KIESSI-3D 프로그램을 이용하여 계산하였다. 선형 지반-구조물 상호작용 문제에 대해 일반적인 KIESSI-3D의 해석결과와 BRM해석결과를 비교하여 제시된 방법의 효율성을 제시하였다. 또한 수치적 비교를 통해 비선형 구조에 대해 보수적인 응답을 보이는 선형 SSI문제에 대하여 얻은 경계반력이 비선형 지반-구조물 상호작용해석에 효과적으로 적용 가능함을 알 수 있었다.

본 논문에서는 거더교 형식을 갖는 교량구조물의 격자 유한요소모델에 대한 모델개선을 위해 하이브리드 유전자 알고리즘에 기초한 유한요소 모델개선기법을 제안하였다. 하이브리드 유전자 알고리즘은 유전자 알고리즘과 심플렉스 최적화방법에 기초한 직접탐색기법으로 구성하였다. 제안된 기법에 적용할 수 있도록 고유진동수, 모드형상 및 정적 처짐에 대한 계측값과 유한요소해석 결과를 사용한 적합함수를 제시하고, 강성과 질량을 동시에 개선할 수 있도록 이들 세 가지 적합함수의 선형 조합 형태를 갖는 다중목적함수를 제시하였다. 제안된 방법은 2경간 연속 격자 유한요소모델의 수치예제와 단경간 플레이트 거더교에 대하여 검증하였다. 수치예제의 경우, 랜덤 노이즈를 고려한 계측오차의 영향을 수치해석적으로 평가하였다. 수치해석과 실험적 검증을 통해, 제안된 방법이 거더교 형식의 교량에 대한 유한요소 모델개선에 적합하고 효과적임을 검증하였다.

Changes in temperature and humidity inside a concrete has correlation with movement speed and reaction rate of deterioration factors such as carbon dioxide and chloride ions. comparison was performed between temperature and relative humidity inside the concrete and meteorological data for exposure environment through measurement at the site for two years.

Recently, an indirect displacement estimation method using data fusion of acceleration and strain (i.e., acceleration-strain-based method) has been developed. This paper proposes an improved displacement estimation method that can be applied to more general types of bridges by building the mapping using the finite element model of the structure. An experimental validation of the proposed method was carried out on a prestressed concrete girder bridge, and the method provides the best estimate for dynamic displacements.

This paper presents a laboratory validation for a Finite Element model updating method using moving vehicle input-deflection output measurements. In conventional FE model updating, a few natural frequencies measured from field experiments have been used to update the FE model based on the assumption that the mass matrix is known accurately. The proposed approach can update the stiffness matrix without the assumption by using static input-output measurements and can even update the mass matrix by using a few natural frequencies obtained from dynamic measurements. Laboratory experiments were carried out for a scaled model of Samseung Bridge located in the test road of Korea Highway Corporation. For a simplicity of experiments, a mass (11kgf) was located in four different locations on the deck and two deflections were measured by laser displacement meters: one at the center girder, and the other in at the outer girder, both in mid-span. Results showed that the proposed methods was capable to estimate Young's Modulus and the mass density of the model bridge accurately while natural-frequency-based updating may result in significant error when higher modes (2nd, 3rd) were used.

One of the most important processes to accurately predict structural responses is to evaluate accurate structural dynamic properties using finite element (FE) models. The analyzed structural dynamic properties usually show considerable discrepancies with the measured ones because structural details are commonly simplified in the FE models. To identify such discrepancies, FE models of them have been calibrated using the measured dynamic properties in previous researches. In this study, dynamic properties were measured for a historic cathedral and the FE model of it was calibrated using the measured results as a reference. Finally, a procedure of the FE model construction for masonry cathedral were tentatively proposed.

The limit state design code for reliability-based design criteria was enacted in January 2012. And, it was necessary to consider new load carrying capacity method for new design code. Therefore, LRFR and ballowable stress design rating was applied to load carrying capacity and compared with the result. In addition, this research consists of ambient vibration measurement, experimental modal analysis, correction of the initial FE model based on the identified modal properties, and estimation of the load carrying capacity using the updated FE model

Conventionally, the load carrying capacities of bridges have been evaluated from proof loading tests with test trucks by measuring static and dynamic response, such ad deflections or strains under known loading conditions. However, load carrying capacity of bridges was evaluated using the updated finite element (FE) model. To solve these problems, deflections or strains can not represent the bridge's health status as the bridge gets deteriorated. For example, deteriorated boundary condition results in small deflection or strain. The proposed method consists of ambient vibration measurement, experimental modal analysis, correction of the initial FE model based on the identified modal properties, and estimation of the load carrying capacity using the updated FE model. The proposed method has been verified through field tests on a prestressed concrete girder bridge by comparing with the result of the conventional truck loading tests.