Formulating the optimum parameters of modified hanger system in the cable-arch bridge to restrain force fluctuation and
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(2020) 42:453
TECHNICAL PAPER
Formulating the optimum parameters of modified hanger system in the cable‑arch bridge to restrain force fluctuation and overstressing problems S. Farahmand‑Tabar1 · M. Barghian1 Received: 4 October 2019 / Accepted: 16 July 2020 © The Brazilian Society of Mechanical Sciences and Engineering 2020
Abstract Inclined hangers behave better than vertical ones under lateral loads (i.e., wind or earthquake) despite they are prone to fatigue phenomenon. In some instances, the slackness problem is seen in some inclined hangers, while others may become overstressed. By considering the modified hanger system, the disadvantages of vertical and inclined systems are resolved, while keeping their advantages. The objective of this study is to propose formulations for the optimum application of novel arrangement of hangers in a cable-arch bridge to suppress problems such as overstressing, force fluctuation, and decreasing the probability of fatigue phenomenon in hangers. To define optimum parameters, the modified hanger system was analyzed and compared with vertical and inclined ones considering nonlinear static analysis under dead load as an initial state plus seismic excitation and dynamic impact load of vehicles. Results indicate that the modified hanger system is improved remarkably in comparison with the inclined and vertical hanger systems. Keywords Modified hanger system · Inclined hanger system · Cable arrangements · Cable-stayed arch bridge · Nonlinear dynamic analysis
1 Introduction To improve the vibration characteristics induced by dynamic loads, the cable systems comprising hangers or main cables may increase the stiffness of the cable or arch bridges. Inclined or vertical hanger systems are the applicable forms in the arch or suspension bridges in which forces are transferred from the deck to the arch by these systems. Due to the damping role of the inclined hangers under dynamic loads, their performance is better than vertical hangers. Nevertheless, due to early fatigue or excessive tensile forces in hangers of several bridges, inclined hanger systems require a modification to achieve optimality. The probability of the fatigue phenomena in inclined hangers is high. Due to loads on bridges with inclined hangers, two adjacent cables may be subjected to tension and Technical Editor: Thiago Ritto. * S. Farahmand‑Tabar [email protected] 1
Department of Structural Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran
compression, respectively. By changing the load direction, the compression in one cable changes into tension and vice versa. Therefore, fatigue phenomenon may happen under repeated load changing. A typical example can be mentioned for the Severn suspension bridge in which some inclined hangers were replaced within the first 10 years of its lifetime [1]. Also, remarkable signs of distress were seen in forces of several inclined hangers, while in some others, slackness problem was observed because of their position against loads. The expected
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