Influence of reinforcement-arrangements on dynamic response of geogrid-reinforced foundation under repeated loading

The dynamic response of the subgrade under moving train loads provides information on subgrade settlement prediction, condition evaluation, and so forth. This paper presents the field dynamics tests on the transition subgrade in the Shuo-Huang heavy-haul railway in China. The variation characteristics of the peak dynamic displacements along the track and subgrade slope were analyzed, and the random distribution characteristics of the peak dynamic displacements at the subgrade shoulder were studied. The response characteristics of the subgrade during the train passage were investigated, and the attenuation regularities of vibration along the subgrade slope were identified. The results indicated that the action of the train moving loads on the subgrade has obvious periodicity, and two bogies in the adjacent wagons should be considered as one loading unit. The peak dynamic displacements at the subgrade shoulder obey normal distribution under the repeated loading of the loading unit. The subgrade bed is dramatically influenced by the dynamic loadings of the trains, and the moving train loads have little influence on the part below the subgrade bed. The results of the research provide the basis for the evaluation of instantaneous and long-term dynamic stability of the subgrade and offer guidance for simulating train moving loads in the model test and numerical analysis to study the dynamic response of the subgrade.

Download Full-text

Dynamic response of two-span continuous composite bridges

Canadian Journal of Civil Engineering ◽

10.1139/l88-078 ◽

1988 ◽

Vol 15 (4) ◽

pp. 579-588 ◽

Cited By ~ 3

Author(s):

Nabil F. Grace ◽

John B. Kennedy

Keyword(s):

Dynamic Response ◽

Natural Frequencies ◽

Plate Theory ◽

Strain Range ◽

Fatigue Cracking ◽

Repeated Loading ◽

Real Problem ◽

Bridge Model ◽

Composite Bridges ◽

Composite Bridge

With the continuing trend towards lighter and more flexible continuous composite bridges, problems of vibration are becoming increasingly more important. Furthermore, fatigue cracking can be a real problem in such bridges when subjected to several thousands of resonance cycles over its life. In this paper the dynamic response of continuous composite bridges and the influence of repeated loading at resonance frequency on the structural response are investigated. A closed-form series solution based on orthotropic plate theory is developed to predict the natural frequencies of two-span continuous composite bridges. Expressions for the equivalent rigidities of a composite bridge are also given. The results are verified and substantiated by experimental results from 1/4-scale bridge model. Estimates of frequencies based on beam theory as well as the effects of concrete and fatigue cracking on the natural frequencies and strain range are examined. Finally, it is shown that a fatigue-cracked composite bridge, when properly repaired, can regain most of its stiffness and ultimate load-carrying capacity. Key words: bridges, composite, concrete, continuous, dynamics, fatigue, orthotropic, rigidities, steel, tests.

Download Full-text