A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement ...A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement (among) the rail, the sleeper and the beam is taken into account. An example is presented and numerical results are compared. The results show that the additional longitudinal forces calculated with the new model are less than those of the previous, especially in the case of the flexible pier bridges. The new model is also suitable for the analysis of the additional longitudinal force transmission between rails and bridges of ballastless track with small resistance fasteners without taking the sleeper displacement into account, and compared with the ballast bridges, the ballastless bridges have a much stronger additional longitudinal force transmission between the continuously welded rails and the bridges.展开更多
The 2-dimensional unsteady aerodynamic forces,in the context of both a thin airfoil where theory of potential flow is always applicable and a bluff bridge-deck section where separated flow is typically induced,are inv...The 2-dimensional unsteady aerodynamic forces,in the context of both a thin airfoil where theory of potential flow is always applicable and a bluff bridge-deck section where separated flow is typically induced,are investigated from a point of view of whether or not they conform to the principle of linear superposition in situations of various structural motions and wind gusts.It is shown that some basic preconditions that lead to the linear superposability of the unsteady aerodynamic forces in cases of thin airfoil sections are no longer valid for a bluff section.Theoretical models of bridge aerodynamics such as the one related to flutter-buffeting analysis and those concerning aerodynamic admittance(AA)functions,however,necessitate implicitly this superposability.The contradiction revealed in this work may throw light on the perplexing problem of AA functions pertaining to the description of buffeting loads of bridge decks.Some existing theoretical AA models derived from flutter derivatives according to interrelations valid only for thin airfoil theories,which have been employed rather extensively in bridge aerodynamics,are demonstrated to be illogical.Finally,with full understanding of the preconditions of the applicability of linear superposability of the unsteady aerodynamic forces,suggestions in regard to experiment-based AA functions are presented.展开更多
文摘A new mechanics model, which reveals additional longitudinal force transmission between the continuously welded rails and the bridges, is established on the fact that the influence of the mutual relative displacement (among) the rail, the sleeper and the beam is taken into account. An example is presented and numerical results are compared. The results show that the additional longitudinal forces calculated with the new model are less than those of the previous, especially in the case of the flexible pier bridges. The new model is also suitable for the analysis of the additional longitudinal force transmission between rails and bridges of ballastless track with small resistance fasteners without taking the sleeper displacement into account, and compared with the ballast bridges, the ballastless bridges have a much stronger additional longitudinal force transmission between the continuously welded rails and the bridges.
基金Projects(51178182,90915002)supported by the National Natural Science Foundation of ChinaProject(SLDRCE10-MB-03)supported by the Open Project of the State Key Laboratory of Disaster Reduction in Civil Engineering,China
文摘The 2-dimensional unsteady aerodynamic forces,in the context of both a thin airfoil where theory of potential flow is always applicable and a bluff bridge-deck section where separated flow is typically induced,are investigated from a point of view of whether or not they conform to the principle of linear superposition in situations of various structural motions and wind gusts.It is shown that some basic preconditions that lead to the linear superposability of the unsteady aerodynamic forces in cases of thin airfoil sections are no longer valid for a bluff section.Theoretical models of bridge aerodynamics such as the one related to flutter-buffeting analysis and those concerning aerodynamic admittance(AA)functions,however,necessitate implicitly this superposability.The contradiction revealed in this work may throw light on the perplexing problem of AA functions pertaining to the description of buffeting loads of bridge decks.Some existing theoretical AA models derived from flutter derivatives according to interrelations valid only for thin airfoil theories,which have been employed rather extensively in bridge aerodynamics,are demonstrated to be illogical.Finally,with full understanding of the preconditions of the applicability of linear superposability of the unsteady aerodynamic forces,suggestions in regard to experiment-based AA functions are presented.
