• Title/Summary/Keyword: Arch Bridge

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Nonlinear Elastic Optimal Design Using Genetic Algorithm (유전자 알고리즘을 이용한 비선형 탄성 최적설계)

  • Kim, Seung Eock;Ma, Sang Soo
    • Journal of Korean Society of Steel Construction
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    • v.15 no.2
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    • pp.197-206
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    • 2003
  • The optimal design method in cooperation with a nonlinear elastic analysis method was presented. The proposed nonlinear elastic method overcame the drawback of the conventional LRFD method this approximately accounts for the nonlinear effect caused by using the moment amplification factors of and. The genetic algorithm uses a procedure based on the Darwinian notions of the survival of the fittest, where selection, crossover, and mutation operators are used to look for high performance among the sections of the database. They satisfy constraint functions and give the lightest weight to the structure. The objective function was set to the total weight of the steel structure. The constraint functions were load-carrying capacities, serviceability, and ductility requirement. Case studies for a two-dimensional frame, a three-dimensional frame, and a three-dimensional steel arch bridge were likewise presented.

Evaluation of minimum depth of soil cover and reinforcement of soil cover above soil-steel bridge (지중강판 구조물의 최소토피고 평가 및 상부토피 보강 방안)

  • Jung, Hyun-Sik;Lee, Jong-Ku;Cho, Sung-Min;Kim, Myoung-Mo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2004.03b
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    • pp.425-432
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    • 2004
  • In this paper, the results of the numerical analysis for the minimum depth of soil cover have been compared with those of currently suggested codes. Based on this comparison, the minimum depth of soil cover for the structures with long spans was suggested. Results showed that the actual depth of the soil cover required against soil failure over a circular and low-profile arch structure does not vary significantly with the size of the span and for the circular structure, the minimum depth of the soil cover was about 1.5m, and for the low-profile arch structures, below about 1.6m. And the previously established code in which the minimum depth of soil cover is defined to linearly increase with the increase in the span (CHBDC, 2001) was very conservative. For the structure with the relieving slab, the maximum live load thrust was reduced by about 36 percent and the maximum moment about 81 percent. The numerical analysis gave more conservative estimation of the live-load thrusts than the other design methods.

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Detection of Manufacturing Defects in Stiffness of CFTA Girder using Static Loading (정적 시험을 사용한 CFTA거더의 제조시 강성 결함 탐색)

  • Kim, Doo-Kie;Alfahdawi, Nathem;Cui, Jintao;Park, Kyung-Hoon
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.25 no.1
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    • pp.109-116
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    • 2012
  • This paper presents a study on the nonlinear behavior of an innovative bridge girder made from concrete-filled and tied tubular steel arch (CFTA) under static loading. Manufacturing of the CFTA girder may have defects which may highly affect the symmetry and performance of the structure. A simple method is proposed by using stiffness extracted from static test data to detect manufacturing defects of the CFTA girder. A three-dimensional finite element model was used in the numerical analysis in order to verify the method. The proposed method was experimentally validated through static tests of the CFTA girder. The application of the proposed method showed that it is effective in identifying invisible manufacturing defects of the CFTA girder, especially for mass production of a standard type in the factory.

Multi-point displacement monitoring of bridges using a vision-based approach

  • Ye, X.W.;Yi, Ting-Hua;Dong, C.Z.;Liu, T.;Bai, H.
    • Wind and Structures
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    • v.20 no.2
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    • pp.315-326
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    • 2015
  • To overcome the drawbacks of the traditional contact-type sensor for structural displacement measurement, the vision-based technology with the aid of the digital image processing algorithm has received increasing concerns from the community of structural health monitoring (SHM). The advanced vision-based system has been widely used to measure the structural displacement of civil engineering structures due to its overwhelming merits of non-contact, long-distance, and high-resolution. However, seldom currently-available vision-based systems are capable of realizing the synchronous structural displacement measurement for multiple points on the investigated structure. In this paper, the method for vision-based multi-point structural displacement measurement is presented. A series of moving loading experiments on a scale arch bridge model are carried out to validate the accuracy and reliability of the vision-based system for multi-point structural displacement measurement. The structural displacements of five points on the bridge deck are measured by the vision-based system and compared with those obtained by the linear variable differential transformer (LVDT). The comparative study demonstrates that the vision-based system is deemed to be an effective and reliable means for multi-point structural displacement measurement.

Design and Construction Case of Urban Tunnel in Alluvial Soil (충적토사지반에서의 도심터널 설계 및 시공)

  • Chang, Seok-Bue;Huh, Do-Hak;Moon, Sang-Jo;Kim, Do-Su
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.829-834
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    • 2009
  • Alluvial soil is one of the most difficult grounds for tunneling works due to the insufficient ground strength and excessive ground water inflow. Dduk island in Seoul has a wide alluvium developed by two rivers, Han and Jung-Ryang. Subway tunnel of $\bigcirc\bigcirc$ line planed across Dduk island has highly poor ground conditions due to small cover and deeply developed alluvium. Moreover, much part of this tunnel is located parallel to the bridge foundations of another railway with a small horizontal distance. Original design was done in 2002 and construction has been in progress. During the construction, tunnel design has been partly changed and adjusted for the complex ground condition and the demand from related organizations. This paper intend to introduce the urban tunnel design and construction in alluvial soils. This line could be divided three sections(A, B, C) according to ground and adjacent conditions. Section A is featured by mixed tunnel faces consisted with alluvial soils and weathered or weak rocks. The feature of section B is that tunnel underpasses near the bridge foundations of another subway. Lastly, section C with a very short length is the most difficult construction conditions due to the small cover, poor ground, obstacles on and underneath ground surface.

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Successful management of absent sternum in an infant using porcine acellular dermal matrix

  • Semlacher, Roy Alfred;Nuri, Muhammand A.K.
    • Archives of Plastic Surgery
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    • v.46 no.5
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    • pp.470-474
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    • 2019
  • Congenital absent sternum is a rare birth defect that requires early intervention for optimal long-term outcomes. Descriptions of the repair of absent sternum are limited to case reports, and no preferred method for management has been described. Herein, we describe the use of porcine acellular dermal matrix to reconstruct the sternum of an infant with sternal infection following attempted repair using synthetic mesh. The patient was a full-term male with trisomy 21, agenesis of corpus callosum, ventricular septal defect, patent ductus arteriosus, right-sided aortic arch, and congenital absence of sternum with no sternal bars. Following removal of the infected synthetic mesh, negative pressure wound therapy with instillation was used to manage the open wound and provide direct antibiotic therapy. When blood C-reactive protein levels declined to ${\leq}2mg/L$, the sternum was reconstructed using porcine acellular dermal matrix. At 21 months postoperative, the patient demonstrated no respiratory issues. Physical examination and computed tomography imaging identified good approximation of the clavicular heads and sternal cleft and forward curvature of the ribs. This case illustrates the benefits of negative pressure wound therapy and acellular dermal matrix for the reconstruction of absent sternum in the context of infected sternal surgical site previously repaired with synthetic mesh.

SHM-based probabilistic representation of wind properties: statistical analysis and bivariate modeling

  • Ye, X.W.;Yuan, L.;Xi, P.S.;Liu, H.
    • Smart Structures and Systems
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    • v.21 no.5
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    • pp.591-600
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    • 2018
  • The probabilistic characterization of wind field characteristics is a significant task for fatigue reliability assessment of long-span railway bridges in wind-prone regions. In consideration of the effect of wind direction, the stochastic properties of wind field should be represented by a bivariate statistical model of wind speed and direction. This paper presents the construction of the bivariate model of wind speed and direction at the site of a railway arch bridge by use of the long-term structural health monitoring (SHM) data. The wind characteristics are derived by analyzing the real-time wind monitoring data, such as the mean wind speed and direction, turbulence intensity, turbulence integral scale, and power spectral density. A sequential quadratic programming (SQP) algorithm-based finite mixture modeling method is proposed to formulate the joint distribution model of wind speed and direction. For the probability density function (PDF) of wind speed, a double-parameter Weibull distribution function is utilized, and a von Mises distribution function is applied to represent the PDF of wind direction. The SQP algorithm with multi-start points is used to estimate the parameters in the bivariate model, namely Weibull-von Mises mixture model. One-year wind monitoring data are selected to validate the effectiveness of the proposed modeling method. The optimal model is jointly evaluated by the Bayesian information criterion (BIC) and coefficient of determination, $R^2$. The obtained results indicate that the proposed SQP algorithm-based finite mixture modeling method can effectively establish the bivariate model of wind speed and direction. The established bivariate model of wind speed and direction will facilitate the wind-induced fatigue reliability assessment of long-span bridges.

A Study on Tension for Cables of a Cable-stayed Bridge Damper is Attached (댐퍼가 부착된 사장교의 케이블 장력에 관한연구)

  • Park, Yeon Soo;Choi, Sun Min;Yang, Won Yeol;Hong, Hye Jin;Kim, Woon Hyung
    • Journal of Korean Society of Steel Construction
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    • v.20 no.5
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    • pp.609-616
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    • 2008
  • Recently, many ocean bridges that connect land to island or island to island have been constructed along with the improvement of the nation's economy. Long-span bridges can be categorized as suspension bridge, cable-stayed bridge, arch bridge and truss bridge. In this study, correction with respect to construction error can be presented on site through the monitoring of the cable tension change of real structure for four major construction stages so that construction accuracy, including the management of profiles, can be improved. A vibration method, the so-called indirect method that uses the cable's natural frequency changes from the acceleration sensor installed on the cable, is applied in measuring cable tension. In this study, the estimation formula for the effective length of cable with damper is presented by comparing and analyzing between actual measurement and analysis result for the change of the cable's effective length. By the way, it is known that the reliability of estimating cable tension by applying the former method that uses the net distance from damper to anchorage is low. Therefore, for future reference of the maintenance stage, the presented formula for estimating the effective length of cable can be used as a reference for the rational decision-making, such as the re-tensioning and replacement of cable.

Random vibration analysis of structures by a time-domain explicit formulation method

  • Su, Cheng;Xu, Rui
    • Structural Engineering and Mechanics
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    • v.52 no.2
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    • pp.239-260
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    • 2014
  • Non-stationary random vibration of linear structures with uncertain parameters is investigated in this paper. A time-domain explicit formulation method is first presented for dynamic response analysis of deterministic structures subjected to non-stationary random excitations. The method is then employed to predict the random responses of a structure with given values of structural parameters, which are used to fit the conditional expectations of responses with relation to the structural random parameters by the response surface technique. Based on the total expectation theorem, the known conditional expectations are averaged to yield the random responses of stochastic structures as the total expectations. A numerical example involving a frame structure is investigated to illustrate the effectiveness of the present approach by comparison with the power spectrum method and the Monte Carlo simulation method. The proposed method is also applied to non-stationary random seismic analysis of a practical arch bridge with structural uncertainties, indicating the feasibility of the present approach for analysis of complex structures.

Cleidocranial dysplasia : a case report (쇄골두개이골증의 증례)

  • Kim Jae-Duk;Lee Chang-Yul;You Choong-Hyun
    • Imaging Science in Dentistry
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    • v.34 no.1
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    • pp.55-59
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    • 2004
  • Cleidocranial dysplasia is a rare and autosomal dominent disorder characterized by aplasia or hypoplasia of the clavicles, an open fontanelle, dental abnormalities, and short stature, A 17-year-old female who presented with short stature and subsequent delay in eruption of permanent teeth is described. she showed the abnormal hypermobility of the shoulder, ocular hypertelorism and concave nasal bridge. Radiographs revealed the underdeveloped maxilla, defect of the cranium in the fontanelle region, and aplasia of the clavicles. Characteristically, panoramic view revealed near parallel-sided borders of the ascending ramus and downward curvature of the zygomatic arch with hypoplasia. The prolonged retention of deciduous teeth with delayed eruption of permanent teeth and multiple embedded supernumerary teeth were striking. Radiographic and clinical investigations revealed Cleidocranial dysplasia.

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