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ABSTRACT This paper presents a method for modeling and analysis of cable-stayed bridges under the action of moving vehicles. Accurate andefficient finite elements are used for modeling the bridge structure.A beam element is adopted for modeling the girder and the pylons.Whereas, a two-node catenary cable element derived using exactanalytical expressions for the elastic catenary, is adopted formodeling the cables. The vehicle model used in this study is a so-called suspension model that includes both primary and secondaryvehicle suspension systems. Bridge damping, bridge-vehicleinteraction and all sources of geometric nonlinearity areconsidered. An iterative scheme is utilized to include the dynamicinteraction between the bridge and the moving vehicles. Thedynamic response is evaluated using the mode superpositiontechnique and utilizing the deformed dead load tangent stiffnessmatrix. To illustrate the efficiency of the solution methodology andto highlight the dynamic effects, a numerical example of a simplecable-stayed bridge model is presented.27940
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ABSTRACTThis paper presents a method for modeling and analysis of cable-stayed bridges under the action of moving vehicles. Accurate andefficient finite elements are used for modeling the bridge structure.A beam element is adopted for modeling the girder and the pylons.Whereas, a two-node catenary cable element derived using exactanalytical expressions for the elastic catenary, is adopted formodeling the cables. The vehicle model used in this study is a so-called suspension model that includes both primary and secondaryvehicle suspension systems. Bridge damping, bridge-vehicleinteraction and all sources of geometric nonlinearity areconsidered. An iterative scheme is utilized to include the dynamicinteraction between the bridge and the moving vehicles. Thedynamic response is evaluated using the mode superpositiontechnique and utilizing the deformed dead load tangent stiffnessmatrix. To illustrate the efficiency of the solution methodology andto highlight the dynamic effects, a numerical example of a simplecable-stayed bridge model is presented.
1. INTRODUCTIONDue to their aesthetic appearance, efficient utilization of structuralmaterials and other notable advantages, cable-stayed bridges havegained much popularity in recent decades. Bridges of this type arenow entering a new era with main span lengths reaching 1000 m.This fact is due, on one hand to the relatively small size of thesubstructures required and on the other hand to the development ofefficient construction techniques and to the rapid progress in theanalysis and design of this type of bridges.The recent developments in design technology, material qualities,and efficient construction techniques in bridge engineering enablethe construction of not only longer but also lighter and moreslender bridges. Thus nowadays, very long span slender cable-stayed bridges are being built, and the ambition is to furtherincrease the span length and use shallower and more slendergirders for future bridges. To achieve this, accurate proceduresneed to be developed that can lead to a thorough understanding anda realistic prediction of the structural response due to not onlywind and earthquake loading but also traffic loading. It is wellknown that large deflections and vibrations caused by dynamic tireforces of heavy vehicles can lead to bridge deterioration and eventually increasing maintenance costs and decreasing service lifeof the bridge structure.
Although several long span cable-stayed bridges are being build orproposed for future bridges, little is known about their dynamicbehavior under the action of moving vehicles. The dynamicresponse of bridges subjected to moving vehicles is complicated.This is because the dynamic effects induced by moving vehicles onthe bridge are greatly influenced by the interaction between thevehicles and the bridge structure. To consider dynamic effects dueto moving vehicles on bridges, structural engineers worldwide relyon dynamic amplification factors specified in bridge design codes.These factors are usually a function of the bridge fundamentalnatural frequency or span length and states how many times thestatic effects must be magnified in order to cover the additionaldynamic loads. This is the traditional method used today for designpurpose and can yield a conservative and expensive design forsome bridges but might underestimate the dynamic effects forothers. In addition, design codes disagree on how this factor shouldbe evaluated and today, when comparing different national codes,a wide range of variation is found for the dynamic amplificationfactor. Thus, improved analytical techniques that consider all theimportant parameters that influence the dynamic response arerequired in order to check the true capacity of existing bridges toheavier traffic and for proper design of new bridges.