Articles written in Sadhana
Volume 47 All articles Published: 1 July 2022 Article ID 0130
Evaluation of longitudinal force in railway bridges: comparative evaluation of codal provisions with comprehensive field investigations
SRINIVAS VOGGU SAPTARSHI SASMAL B ARUN SUNDARAM
The present paper focusses on the critical examination of the existing provisions in the current International- and National- Standards for longitudinal force (LF) evaluation in railway bridges during braking and tractive effort from train formation. During the comparative evaluation among the codes, the prevailingstipulations for the allowable vertical load are considered, followed by the same vertical load for bringing the uniformity in the comparison in LF arrived using the codes. It is found that the predicted values are widely different and the disparity is more pronounced when the bridge span is longer than 30 m. Since no wellacceptable strategy is available for evaluation of LF in railway bridges, detailed field investigations are carried out. Five different types of bridges (steel plate girder, prestressed concrete girder, prestressed slab and masonry arch) are considered for field investigations. For each case, the innovative arrangement is conceptualised and designed to capture the developed LF during plying of fully loaded test train formation on the bridge spans. Prior to the massive tests, field level calibration studies are carried out for understanding the dispersion of LF at rail level to the girder level and based on that, the instrumentation and test method is established. During field studies, the instrumentation is carried out from wagon coupler level (or rail level as suitable) to girder level to experimentally estimate the force flow. It is found that the developed schemes are able to provide the critical information on the LF at different levels of the bridge. Further, the magnitude of induced longitudinal force depends on the type of the bridge and the braking case is found to be not as critical as tractive effort. It is also noted that the evaluated LF, though varying from case to case, is 25–40% of the predicted values. The present study emphasized the need for an efficient and elaborate method(s) for evaluation of LF in railway bridges.
Volume 48, 2023
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