• Earthquakes and Structures
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• 제11권4호
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• pp.681-699
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• 2016

Steel box girders have two webs and two flanges on top that are usually connected with shear connectors to the concrete deck and are also known as tub girders. The end diaphragms of such bridges comprise of a stiffened steel plate welded to the inside of the girder at each end. The diaphragms play a major role in transferring vertical and lateral loads to the bearings and substructure. A review of literature shows that the cyclic behavior of diaphragms under earthquake loading has not been studied previously. This paper uses a nonlinear finite element model to study the behavior of the end diaphragms under gravity and seismic loads. Different bearing device and stiffener configurations have been considered. Affected areas of the diaphragm are distinguished.

• 한국공간구조학회논문집
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• 제2권2호
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• pp.51-58
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• 2002

This paper is presented an experimental studies on bond stress between steel and concrete in concrete filled steel tubes. In the actual building frames, vertical dead and live loads on beams are usually transferred to columns by beam-to-column connections. In case when concrete filled steel tubes are used as columns of an actual building frame which has a simple connection, shear forces in the beam ends are not directly transferred to the concrete core but directly to the steel tube. Provided that the bond effect between steel tube and concrete core should not be expected, none of the end shear in the beams would be transferred to the concrete core but only to the steel tube. Therefore, it is important to investigate the bond strength between steel tube and concrete core in the absence of shear connectors.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.325-342
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• 2020

The current study is focused on the evaluation of the ultimate strength of stiffened panels found in ship hull structures that are subjected to combined uniaxial thrust, in-plane and out-of-plane bending moments. This loading condition, which is in general ignored when performing buckling checks, applies to representative control geometries (stiffener with attached plating) as a consequence of the linearly varying normal stresses along the ship's depth induced by the hull-girder vertical bending moment. The problem is generalized by introducing a non-uniform thrust described by a displacement ratio and rotation angle and by introducing the slenderness ratios, within the practical range of interest. The formed design space is explored through methods sourcing from Design of Experiments and by applying non-linear finite element procedures. Surrogate empirical models have been constructed through regression analysis and Response Surface Methods. An additional empirical model is provided to the literature for predicting the ultimate strength under uniaxial thrust. The numerical experimentation has shown that is a significant influence on the ultimate strength of stiffened panels as the thrust non-uniformity increases.

• Steel and Composite Structures
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• 제33권6호
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• pp.793-803
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• 2019

Concrete-filled steel tubular (CFST) beam-columns are widely used owing to their good performance. They have high strength, ductility, large energy absorption capacity and low costs. Externally stiffened CFST beam-columns are not used widely due to insufficient design equations that consider all parameters affecting their behavior. Therefore, effect of various parameters (global, local slenderness ratio and adding hoop stiffeners) on the behavior of CFST columns is studied. An experimental study that includes twenty seven specimens is conducted to determine the effect of those parameters. Load capacities, vertical deflections, vertical strains and horizontal strains are all recorded for every specimen. Ratio between outer diameter (D) of pipes and thickness (t) is chosen to avoid local buckling according to different limits set by codes for the maximum D/t ratio. The study includes two loading methods on composite sections: steel only and steel with concrete. The case of loading on steel only, occurs in the connection zone, while the other load case occurs in steel beam connecting externally with the steel column wall. Two failure mechanisms of CFST columns are observed: yielding and global buckling. At early loading stages, steel wall in composite specimens dilated more than concrete so no full bond was achieved which weakened strength and stiffness of specimens. Adding stiffeners to the specimens increases the ultimate load by up to 25% due to redistribution of stresses between stiffener and steel column wall. Finally, design equations previously prepared are verified and found to be only applicable for medium and long columns.

• Structural Engineering and Mechanics
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• 제5권3호
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• pp.269-281
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• 1997

The overall buckling mode in a composite steel-concrete beam over an internal support is necessarily lateral-distortional, in which the bottom compressive range displaces laterally and twists, since the top flange is restrained by the nearly rigid concrete slab. An efficient finite element method is used to study elastic lateral-distortional buckling in composite beams whose steel portion is tapered. The simplified model for a continuous beam that is presented herein is a fixed ended cantilever whose steel portion is tapered, and is subjected to moment gradient. This is intended to give an insight into distortion in a continuous beam that occurs in the negative bending region, and the differences between the cantilever representation and the continuous beam are highlighted. An eigenproblem is established, and the buckling modes and loads are determined in the elastic range of structural response. It is found from the finite element study that the buckling moment may be enhanced significantly by using a vertical stiffener in the region where the lateral movement of the bottom range is greatest. This enhancement is quantified in the paper.

• Structural Engineering and Mechanics
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• 제19권3호
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• pp.347-359
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• 2005

This paper attempts to develop the analytical model of estimating the fatigue damage using a linear elastic fracture mechanics method. The stress history on a welding member, when a truck passed over a bridge, was defined as a block loading and the crack closure theory was used. These theories explain the influence of a load on a structure. This study undertook an analysis of the stress range frequency considering both dead load stress and crack opening stress. A probability method applied to stress range frequency distribution and the probability distribution parameters of it was obtained by Maximum likelihood Method and Determinant. Monte Carlo Simulation which generates a probability variants (stress range) output failure block loadings. The probability distribution of failure block loadings was acquired by Maximum likelihood Method and Determinant. This can calculate the fatigue reliability preventing the fatigue failure of a welding member. The failure block loading divided by the average daily truck traffic is a predictive remaining life by a day. Fatigue reliability analysis was carried out for the welding member of the bottom flange of a cross beam and the vertical stiffener of a steel box bridge by the proposed model. Results showed that the primary factor effecting failure time was crack opening stress. It was important to decide the crack opening stress for using the proposed model. Also according to the 50% reliability and 90%, 99.9% failure times were indicated.

• Steel and Composite Structures
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• 제47권2호
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• pp.239-251
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• 2023

The stiffness evaluation of cracked base metal is of great guidance to fatigue crack reinforcement. By carrying out fatigue tests and numerical simulation of typical cracking details in steel box girder, the strain-degradation law of cracked base metal was analyzed and the relationship between base metal stress and its displacement (stiffness) was explored. The feasibility of evaluating the stress of cracked base metal based on the stress field at the crack tip was verified. The results demonstrate that the stiffness of cracked base metal shows the fast-to-slow degradation trend with fatigue cracking and the base metal at 50mm or more behind the crack tip basically lose its bearing capacity. Drilling will further accelerate stiffness degradation with the increase of hole diameters. The base metal stress has a negative linear relation with its displacement (stiffness), The stress of cracked base metal is also related to stress intensity factor and its relative position (distance, included angle) to the crack tip, through which the local stiffness can be effectively evaluated. Since the stiffness is not uniformly distributed along the cracked base metal, the reinforcement patch is suggested to be designed according to the stiffness to avoid excessive reinforcement for the areas incompletely unloaded.

• 한국강구조학회 논문집
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• 제16권2호통권69호
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• pp.275-284
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• 2004

기둥-보 약축 접합 디테일 개발을 위해서 접합부의 거동을 파악하는 것이 선행되어야한다. 약축 접합부의 형식에 따른 강축 접합부의 거동을 파악하기위하여 기존 브라켓타입 용접접합부의 각 요소들 즉 패널존, 수평스티프너의 유무 및 위치를 변수로 고려하였다. 본 연구에서는 접합부에 수평스티프너가 있는 경우는 접합부를 수직스티프너로 보강한 단순보로 치환하여 접합부의 내력을 산정하였으며, 수평스티프너가 없는 경우는 기둥플랜지의 국부휨강도, 기둥 웨브의 국부인장강도, 기둥 웨브의 크립플링강도 및 기둥웨브의 최대 좌굴강도를 고려한 내력 평가식을 사용하였고 이론해석결과와 실험결과를 비교 분석하였다.

• 한국산학기술학회논문지
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• 제15권1호
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• pp.561-568
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• 2014

조립식 경골잔교는 Spine-girder인 단일거더 시스템이므로 휨 뿐만 아니라 비틀림에 큰 영향을 받는 구조물이다. 본 연구에서는 경골잔교의 합리적인 설계를 위하여 설계 시 고려사항을 도출하고자 하였다. 거동분석을 위한 구조해석 유한요소모델을 개발하고, 실험 결과와 비교하여 타당성을 검증하였다. 경골잔교의 거동분석을 통하여 국부적인 과대응력 발생을 방지하기 위하여 Bone-beam 하단부에 보강재 설치가 필요하며, 플랜지의 법선응력은 ?비틂, 플랜지와 웹의 전단응력은 순수비틂에 의한 영향이 지배적으로 작용하는 것을 확인하였다.

• 한국강구조학회 논문집
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• 제9권2호통권31호
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• pp.237-248
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• 1997

크레인 주행거더에서 빈번히 발생되는3 종류의 균열을 재현하기 위해서 거더 길이 640 mm, 높이 600 mm, 폭 300 mm의 시험체 2기를 제작하여 피로실험을 수행하였다. 시험체의 균열은 재하점 부근과 가세트 단부 및 하부플랜지와 웨브의 모살용접부에서 발생하였다. 재하점 근방의 균열은 수직보강재가 위치한 상부플랜지와 웨브 사이의 모살용접부에서 발생해서 웨브의 대각선 방향으로 진전하였다. 또한 하부플랜지 종비드에서 발생된 균열은 주행거더방향에 수직으로 성장하였다. 크레인 주행거더의 각 부위의 피로등급은 JSSC 피로설계지침의 피로등급과 비교해 보면, 재하점 근방의 모살용접부는 E 등급, 가세트 단부는 G 또는 H 등급, 하부플랜지 종비드 부위는 D 등급 정도로 나타났다. 가세트 단부와 종비드 부위는 피로설계지침과 잘 일치하고 있음을 알 수 있다.