Varol AKAR, Erdoğan UZGİDER

Demiryolu köprülerinin sistem güvenilirlik indislerinin belirlenmesi

Yapılan çalışmada, Güvenilirlik Teorisinin esasları ve bir sonlu elemanlar metodu kullanılarak demiryolu köprülerinin servis yükleri altında güvenilirlik indislerini belirleyen pratik ve etkin bir yöntem geliştirilmiştir. Demiryolu servis yüklerinin, olasılık dağılım fonksiyonları ile istatistik parametreleri belirlenmiştir. Bu çalışma kapsamında, geometrik ve malzeme bakımından lineer olmayan etkiler ile düğüm noktalarının yarı rijit davranış özelliklerinin dikkate alındığı bir yapı analiz programı geliştirilmiştir. Bu program yardımıyla mevcut demiryolu hatlarında hizmet veren çelik kafes kirişli bir köprünün modellemesi yapılmış ve köprü üzerindeki bir elektrikli lokomotifin farklı konumları için göçme mekanizmaları ve bu göçme mekanizmalarına ait eleman göçme sıraları belirlenmiştir. Eleman seviyesindeki güvenilirlik indislerinden köprünün sistem güvenilirlik indisi saptanmıştır.

Determination of system reliability indices of railway bridges

In this study, by using theory of reliability and a finite element method, a practical and effective method determining safety indices of existing railway bridges under service loads has been developed. At present, safety evaluation studies on railway bridges subject to increasing axle loads and traffic density resulting from various economic and technological developments are important. For this purpose an efficient algorithm has been developed to define the potential failure mechanisms of the bridge structures. Then using potential mechanisms and employing theory of reliability an algorithm has been developed which defines system reliability depending on element reliability. In order to define probability distribution functions of railway service loads and statistical parameters (standard deviation, variation coefficient, etc.) of these functions, approximately five hundred freight and passenger train settings in operation for a year have been investigated. A structural analysis program taking into consideration geometrically and materially non linear effects and characteristics of semi-rigid behaviour of joints in the system of bridges has been developed. The steel truss bridges, giving service on Turkish Railway Network have been modelled by using the program and bridge failure mechanisms and order of failure of members for each failure mechanism, for each different position of an electric locomotive on the bridge have been set out. System safety indice of the bridge are then determined by utilising safety indices of each member.

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Bilal, A. ve Ibrahim, A., (1990). Posttensioned Trusses: Reliability and Redundancy, Journal of Structural Engineering, 116, 1507-1521.
DIN 4114, Stahl im Hochbau 13. Auflage (1963). Verlag Stahleisen M.B.H., Düsseldorf.
Frangopol, Dan M., (1999). Bridge Safety and Reliability, ASCE, USA.
Kim, Seung-Eock ve Choi, Se-Hyu, (2001). Practical advanced analysis for semi-rigid space frames, International Journal of Solids and Structures, 38, 9111-9131.
Kim, Seung-Eock, Park, Moon-Ho, ve Choi, Se- Hyu., 2002. 3-D Second-order plastic-hinge analysis accounting for lateral torsional buckling, International Journal of Solids and Structures, 39, 2109-2128.
Madsen, H.O., Krenk, S. ve Lind, N.C., (1986). Methods of Structural Safety, Prentice-Hall Inc., Englewood Cliffs.
Nowak, A.S. ve Collins, K.R, (2000). Reliability of Structures, Mc Graw-Hill Higher Education, Boston.
Smith, I.M. ve Griffiths, D.V., (1988). Programming The Finite Element Method, Second Edition, John Willey & Sons , Chichester.
Uzgider, E., Sanli, A., Piroğlu, F. ve Cağlayan, B. O., (1996). General report for the bridge tests conducted in 1992, 1993 and 1994, NATO Science for stability programme, TU-850- BRIDGES Research Project Report 4, published by the Istanbul Technical University, Civil Engineering Faculty, Structural Department, Istanbul / Turkey.
UIC 776-1, International Union of Railways Code,(1994). Loads to be considered in railway bridge design, UIC, France.
UIC 778-2, International Union of Railways Code,(1986). Recommendations for determining the carrying capacity of existing metal structures, UIC, France.