Development of automatic system for evaluating the stress redistribution in structural members of a steel cable-stayed bridge due to cable stress relaxation

Tien-Thang Hong,Jung J. Kim,Duc-Kien Thai,Seung-Eock Kim 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.44 No.6

In this study, a graphical automatic system is developed in order to investigate the stress redistribution of structural members in a steel cable-stayed bridge. The generalized Maxwell model is selected for stress relaxation estimation, and it is carefully verified and applied to all the cable members of a steel cable-stayed bridge to investigate its stress relaxation. A set of stress relaxation parameters in all cables is determined using the fmincon optimization function. The stress redistribution of the steel cable-stayed bridge is then analyzed using ABAQUS. To shorten the investigation time, all the aforementioned phases are built up to be an automatic system. The automatic system is then employed to investigate the effect of cable cross-section areas and girder spans on stress redistribution. The findings from these studies show that the initial tension in the cables of a steel cable-stayed bridge should be kept to less than 55% of the cable's ultimate strength to reduce the effect of cable stress relaxation. The cable space in a steel cable-stayed bridge should be limited to 15,000 mm to minimize the effect of cable stress relaxation. In comparison to other structural members of a steel cable-stayed bridge, the girders experience a significant stress redistribution.

곡선 사장교의 풍하중을 고려한 횡방향 거동 해석

이재석,최규천 한국풍공학회 2005 한국풍공학회지 Vol.9 No.1

A study for the transverse behavior of the curved steel cable-stayed bridge and PSC cable-stayed bridge under the static wind load as well as dead load and cable forces is presented. To account for the nonlinear behaviors of the curved cable-stayed bridge, material and geometric nonlinearity and time-dependent properties of materials are considered. A cable-stayed bridge is modeled as an assemblage of frame elements consisting of concrete and steel fibers, prestressing tendon segments and three-dimensional curved cable elements. In order to investigate the effectiveness of auxiliary cables on the transverse behavior of the curved cable-stayed bridge, nonlinear analyses on the curved steel and PSC cable-stayed bridge erected with or without the auxiliary cables are carried out. In addition, nonlinear analyses on the transverse behavior of the bridge for the static wind load are carried out at each erection step of the bridge. The numerical results show that the transverse deflections and bending moments of the bridge deck during construction stages can be greater than those of the bridge after completion. Moreover, the auxiliary cables are found to be effective to reduce the transverse deflections and moments of the bridge deck whether the wind load is considered or not. 이 논문에서는 3차원 케이블 지지 프레임의 비선형 해석 프로그램을 이용하여 곡선 강사장교와 곡선 PSC 사장교를 대상으로 시공의 진행에 따른 사하중과 케이블 긴장력에 의한 횡방향 거동은 물론 시공 중의 각 단계에서 발생할 수 있는 풍하중에 의한 상판의 횡방향 거동과 임시 보조 케이블이 풍하중 거동에 미치는 영향을 검토하였다. 곡선 사장교의 비선형 거동을 정확히 예측하기 위하여 각 시공단계마다 재료의 비선형성과 기학적 비선형성은 물론 재료의 시간의존적 특성의 영향을 모두 고려한 비선형 해석을 하였다. 정적풍하중이 작용하는 곡선 사장교의 시공단계를 고려한 비선형 해석을 수행한 결과, 두 가지 형태의 사장교에서 시공 중에 풍하중에 의한 횡방향 거동이 시공이 완료된 후보다 불리한 경우가 있음을 확인하였으며 보조 케이블이 곡선 사장교의 횡방향 거동에 미치는 영향이 작지 않음을 알 수 있었다. 또한 풍하중을 고려할 경우에 과다한 횡방향 거동을 제어하기 위해서는 추가적인 보조 케이블의 설치가 필요할 수 있음을 확인하였다.

강사장교 비선형거동과 하모니 서치 알고리즘에 기반한 사장교 구성 단면 결정

마상수,권태윤,이원홍,안진희 한국구조물진단유지관리공학회 2024 한국구조물진단유지관리공학회 논문집 Vol.28 No.4

In this study, a determination method of structural member section based on Nonlinear behaviors of steel cable-stayed bridges and the Harmony Search algorithm was presented. The Harmony Search algorithm determines the structural member section of cable-stayed bridges by repeating the process of setting the initial value, initializing the harmony memory, configuring the new harmony memory, and updating the harmony memory to search for the optimal value. The nonlinear initial shape analysis of a three-dimensional steel cable-stayed bridge was performed with the cross-section of the main member selected by the Harmony Search algorithm, and the optimal cross-section of the main members of the cable-stayed bridge, such as pylons, girders, cross-beams, and cables, reflecting the complex behavior characteristics and the nonlinearity of each member was determined in consideration of the initial tension and shape. The total weight was used as the objective function for determining the cross-section of the main member of the cable-stayed bridges, and the load resistance ability and serviceability based on the ultimate state design method were used as the restraint conditions. The width and height ratio of the girder and cross-section were considered additional restraint conditions. The optimal sections of the main members were made possible to be determined by considering the geometry and material nonlinearity of the pylons, girders, and cross-sections and the nonlinearity of the cable members. As a result of determining the optimal cross-section, it was confirmed that the proposed analysis method can determine the optimal cross-section according to the various constraint conditions of the cable-stayed bridge, and the structural member section of the cable-stayed bridge considering the nonlinearity can be determined through the Harmony Search algorithm. 본 연구에서는 강사장교의 비선형 거동과 하모니 서치 알고리즘에 기반한 사장교 부재 단면 결정 방법을 제시하였다. 하모니 서치알고리즘은 초기값 설정, 하모니 메모리 초기화, 새로운 하모니 메모리 구성 및 하모니 메모리 업데이트의 과정을 반복하여 최적값을 탐색함으로써 사장교 부재 단면을 결정한다. 하모니 서치 알고리즘으로 선정된 주요 부재 단면으로 3차원 강사장교의 비선형 초기형상해석을 수행하였으며, 초기장력과 형상을 고려하여 복잡한 거동특성과 각 부재의 비선형성을 반영한 사장교 주요 부재인 주탑, 보강거더, 가로보 및 케이블의최적 단면을 결정하였다. 사장교 주요 부재의 단면 결정을 위한 목적함수로는 전체 중량을 사용하였으며, 제약조건으로 한계상태설계법을 바탕으로 하중저항능력과 사용성에 대한 제약조건식 및 보강거더와 가로보 단면의 폭과 높이의 비율을 추가적인 제약조건으로 고려하고, 주탑, 보강거더 및 가로보의 기하 및 재료 비선형성과 케이블 부재의 비선형성에 따라 부재 단면을 결정할 수 있도록 하였다. 최적 단면 결정 결과, 제안한 해석 방법은 사장교의 다양한 설치조건에 따라 최적 단면을 결정할 수 있으며, 비선형성을 고려한 사장교 부재 단면제원을 하모니 서치 기법을 통하여 결정할 수 있음을 확인하였다.

완성계 강사장교의 극한 거동의 해석적 연구

김승준(Kim Seungjun),임석빈(Im Seok-Been),이기세(Lee Kee-Sei),강영종(Kang Young-Jong) 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.2A

논문은 비선형 해석을 통한 완성계 강사장교의 극한 거동에 대해 다룬다. 사장교는 재료적 비선형성과 함께 다양한 기하학적 비선형성을 나타내므로 극한 거동을 명확히 규명하려면 반드시 합리적인 비선형해석이 수행되어야 한다. 따라서 본 연구에서는 합리적인 극한 해석기법을 통해 활하중에 대한 강사장교의 주요한 극한거동을 규명하고자 하였다. 강사장교의 비선형 해석을 위하여 비선형 트러스 요소 및 비선형 프레임요소를 이용하였고, 강재의 재료적 비선형성을 효율적으로 고려하기 위해 개선소성힌지법을 이용하였다. 활하중에 대한 극한 거동을 합리적으 분석하기 위해 본 연구에서는 초기형상해석활하중 해석으로 이어지는 2단계 해석 기법을 통해 극한 해석을 수행하였다. 해석 모델은 총 지간장이 920.0 m 사장교를 이용하였고, 방사형 및 팬 형 사장교를 해석에 이용하였다. 극한 해석결과를 통해 얻은 하중-변위 곡선, 구조물 변형형상, 소성단면, 휨모멘트분포도 등을 분석하여 활하중에 대한 완성계 사장교의 주요한 극한 거동을 규명하였다. This paper presents an investigation on the ultimate behavior of steel cable-stayed bridges using nonlinear finite element analysis method. Cable-stayed bridges exhibit various geometric nonlinearities as well as material nonlinearities, so rational nonlinear finite element analysis should be performed for investigation of the ultimate behavior. In this study, ultimate behavior of steel cable-stayed bridges was studied using rational ultimate analysis method. Nonlinear equivalent truss element and nonlinear frame element were used for modeling the cable, girder and mast. Moreover, refined plastic hinge method was adopted for considering the material nonlinearity of steel members. In this study, the 2-step analysis method was used. Before live load analysis, initial shape analysis was performed in order to consider the dead load condition. For investigation of the ultimate behavior of steel cable-stayed bridges, analysis models which span length is 920.0 m were used. Radiation type and fan type were considered as the cable-arrangement types. With various quantitative evidences such as load-displacement curves, deformed shapes, locations of the yield point or region, bending moment distribution and so on, the ultimate behavior of steel cable-stayed bridges was investigated and described in this paper.

Stability analysis of steel cable-stayed bridges

Tang, Chia-Chih,Shu, Hung-Shan,Wang, Yang-Cheng Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.11 No.1

The objective of this study is to investigate the stability behavior of steel cable-stayed bridges by comparing the buckling loads obtained by means of finite element methods with eigen-solver. In recent days, cable-stayed bridges dramatically attract engineers' attention due to their structural characteristics and aesthetics. They require a number of design parameters and present a high degree of static indetermination, especially for long span bridges. Cable-stayed bridges exhibit several nonlinear behaviors concurrently under normal design loads due to the individual nonlinearity of substructures such as the pylons, stay cables, and bridge deck, and their interactions. The geometric nonlinearities arise mainly from large displacements of cables. Strong axial and lateral forces acting on the bridge deck and pylons cause structural nonlinear behaviors. The interaction is among the substructures. In this paper, a typical three-span steel cable-stayed bridge with a variety of design parameters has been investigated. The numerical results indicate that the design parameters such as the ratio of $L_1/L$ and $I_p/I_b$ are important for the structural behavior, where $L_1$ is the main span length, L is the total span length of the bridge, $I_p$ is the moment of inertia of the pylon, and $I_b$ is the moment of inertia of the bridge deck. When the ratio $I_p/I_b$ increases, the critical load decreases due to the lack of interaction among substructures. Cable arrangements and the height of pylon are another important factors for this type of bridge in buckling analysis. According to numerical results, the bridges supported by a pylon with harp-type cable arrangement have higher critical loads than the bridges supported by a pylon with fan-type cable arrangement. On contrary, the shape of the pylon does not significantly affect the critical load of this type of bridge. All numerical results have been non-dimensionalized and presented in both tabular and graphical forms.

기하학적 특성이 강사장교의 극한 거동에 미치는 영향

김승준(Kim, Seungjun),신도형(Shin, Do Hyoung),최병호(Choi, Byung Ho),강영종(Kang, Young Jong) 대한토목학회 2012 대한토목학회논문집 A Vol.32 No.6A

본 논문은 완성계 강사장교의 기하학적 특성이 극한 거동에 미치는 영향을 분석한다. 사장교는 구조형식의 특성에 따라 매우 효율적인 구조체로 알려져 있지만, 이러한 구조 특성에 따라 구조물의 극한 거동에 영향을 미치는 다양한 비선형성과 함께 복잡한 구조거동을 보인다. 본 연구에서는 거더 및 주탑의 단면 크기, 케이블 배치 형식 및 케이블 단면적 변화에 따른 완성계 강사장교의 극한 거동에 대해 다룬다. 선행연구를 통해 도출된 극한거동에 지배적인 활하중에 대해 각 인자의 변화에 대한 매개변수연구를 수행하였다. 활하중에 대한 완성계 사장교의 합리적인 해석을 위해 초기형상해석-활하중해석을 거치는 2단계 해석법을 통해 극한 해석을 수행하였다. 해석에 고려된 사장교 모델은 총 920.0 m의 지간장을 갖는 강사장교 이고 케이블 배치각도에 따른 거동분석을 위해 방사형 사장교와 팬 형 사장교 모델을 이용하였다. 본 해석 연구를 통해 각 기하학적 특성 인자 변화에 따른 완성계 강사장교의 극한거동 변화 특성을 도출하였다. This study presents the effects of various geometric properties on the ultimate behavior of steel cable-stayed bridges. In general, cable-stayed bridges are well known as a very efficient structural system, because of those geometric characteristics, but at the same time, the structure also shows complex structural behavior including various nonlinearities which significantly affect to the ultimate behavior of the structure. In this study, the effects of various geometric properties of main members on the ultimate behavior under specific live load cases, which had been studied in previous studies, were investigated using a rational analytical method. In this parametric study, sectional dimensions of main members were considered as main geometric parameters. For the rational ultimate analysis under specific live load cases, the 2-step analysis method, which contains initial shape analysis and live load analysis, was used. As the analysis model, 920.0 m long steel cable-stayed bridges were used and two different types of cable arrangement were considered to study the effect of the cable arrangement types. Through this study, the effects of various geometric properties on the characteristics of the ultimate behavior of steel cable-stayed bridges were intensively investigated.

Probabilistic Optimal Safety with Minimum Life-Cycle Cost Based on Stochastic Finite Element Analysis of Steel Cable-Stayed Bridges

한성호,방명석 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.3

This study was intended to efficiently perform the probabilistic safety and optimal design assessment of steel cable-stayed bridges (SCS bridges) using stochastic finite element analysis (SFEA) and expected life-cycle cost (LCC) concept. To that end,advanced probabilistic finite element algorithm (APFEA) which enables to execute the static and dynamic SFEA considering aleatory uncertainties contained in random variable was developed. APFEA is the useful analytical means enabling to conduct the reliability assessment (RA) in a systematic way by considering the result of SFEA based on linearity and nonlinearity of before or after introducing initial tensile force. Appropriateness of APFEA was verified in such a way of comparing the result of SFEA of a simple structure and the result of numerical analysis using Monte Carlo Simulation (MCS) program. The probabilistic method of SCS bridges was set, taking into account of analytical parameters. The dynamic response characteristic by probabilistic method was evaluated using ASFEA, and RA was carried out based on analysis result, thereby quantitatively calculating the probabilistic safety. The optimal design of SCS bridges was determined based on the expected LCC according to the results of SFEA and RA of alternative designs. Moreover, given the potential epistemic uncertainty contained in safety index, failure probability and minimum LCC, the sensitivity analysis was conducted and as a result, a critical distribution phase was illustrated using a cumulative-percentile.

Concept and Analysis of Stay Cables with a CFRP and Steel Composite Section

Wen Xiong,C.S. Cai,Rucheng Xiao,Lu Deng 대한토목학회 2012 KSCE Journal of Civil Engineering Vol.16 No.1

This paper describes the concept of a novel stay cable with a Carbon Fiber Reinforced Plastic (CFRP) and steel composite section. In this concept CFRP core conserves all the advantages of CFRP materials such as light weight and high strength, while steel coat provides protection for the CFRP core and ensures reliable anchorage performance. The steel coat can reduce cost and provide higher stiffness than CFRP materials in some length range. Following this concept, several configurations were proposed for the composite structure. Effects of the key design parameter of the proposed stay cables, namely the ratio of the CFRP section area to the whole section area, were examined through a parametric study using analytical solutions. By doing this, an appropriate range of the ρ value was suggested. Factors that can affect the appropriate range of the ρ value, including the horizontal projected length of stay cables,cable force, and pylon height (i.e., vertically projected length of stay cables), were also studied. Finally, the feasibility of the proposed stay cables was conceptually verified. It was shown that the proposed stay cables could be an excellent alternative to the pure CFRP or traditional steel stay cables.

인공신경망을 이용한 강합성 사장교 차량하중분석시스템 개발

박민석(Park Min-Seok),조병완(Jo Byung-Wan),이정휘(Lee Jungwhee),김성곤(Kim Sungkon) 대한토목학회 2008 대한토목학회논문집 A Vol.28 No.6A

The analysis of vehicular loads reflecting the domestic traffic circumstances is necessary for the development of adequate design live load models in the analysis and design of cable-supported bridges or the development of fatigue load models to predict the remaining lifespan of the bridges. This study intends to develop an ANN(artificial neural network)-based Bridge WIM system and Influence line-based Bridge WIM system for obtaining information concerning the loads conditions of vehicles crossing bridge structures by exploiting the signals measured by strain gauges installed at the bottom surface of the bridge superstructure. This study relies on experimental data corresponding to the travelling of hundreds of random vehicles rather than on theoretical data generated through numerical simulations to secure data sets for the training and test of the ANN. In addition, data acquired from 3 types of vehicles weighed statically at measurement station and then crossing the bridge repeatedly are also exploited to examine the accuracy of the trained ANN. The results obtained through the proposed ANN-based analysis method, the influence line analysis method considering the local behavior of the bridge are compared for an example cable-stayed bridge. In view of the results related to the cable-stayed bridge, the cross beam ANN analysis method appears to provide more remarkable load analysis results than the cross beam influence line method. 국내 교통 현실을 반영한 중(重)차량에 대한 하중 분석은 케이블 교량의 유지관리시 잔존수명 예측을 위한 피로하중모델 개발이나 교량의 설계시 해석에 필요한 활하중 모델 개발시 반드시 필요하다. 이에 본 연구에서는 강합성 사장교 상부구조 하면에 설치된 변형률 센서에서 측정한 신호를 이용하여 교량을 주행하고 있는 중차량의 하중정보를 얻기 위하여, 인공신경망 및 영향선을 이용한 차량하중분석시스템을 개발하였다. 인공신경망의 학습과 테스트를 위한 데이터 확보에 있어서 이론적인 수치 시뮬레이션을 통하지 않고, 실제 교량을 주행하는 임의 차량에 대해 직접 측정한 데이터를 이용하였다. 또한, 학습된 신경망의 정확도를 검증하기 위하여 3종류의 시험재하차량을 반복 주행시켜 구한 값과 계량소에서 측정한 정적 값을 비교하였다. 교량의 국부거동을 고려하기 위하여 가로보를 이용하였고, 인공신경망을 이용한 방법과 영향선을 이용한 방법의 분석결과를 비교한 결과, 인공신경망이론을 적용한 분석방법이 하중 판별의 정확도에 있어서는 영향선 분석방법보다 높은 정확도를 얻을 수 있었다.

지진격리 강재 케이블 교량의 다지점 진동대 실험

김성도,안진희,공영이,최형석,정진환 한국지진공학회 2015 한국지진공학회논문집 Vol.19 No.4

A series of tests was conducted for full-scale single-pylon asymmetric cable-stayed bridges using a system of multiple shaking tables. The 2-span bridge length was 28 m, and the pylon height was 10.2 m. 4 different base conditions were considered: the fixed condition, RB (rubber bearings), LRB (lead rubber bearings), and HDRB (high damping rubber bearings). Based on investigation of the seismic response, the accelerations and displacements in the axial direction of the isolated bridge were increased compared to non-isolated case. However, the strain of the pylon was decreased, because the major mode of the structure was changed to translation for the axial direction due to the dynamic mass. The response of the cable bridge could differ from the desired response according to the locations and characteristics of the seismic isolator. Therefore, caution is required in the design and prediction in regard to the location and behavior of the seismic isolator.