Railway Interchange 2019

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An Innovative Prestressing System for Concrete Crossties Using Shape Memory Alloys (Room M 100 C)

24 Sep 19
11:30 AM - 12:00 PM

Tracks: AREMA Technical Sessions By Functional Group- Track, Technical Sessions By Day- Tuesday

Concrete crossties are typically prestressed with straight high strength steel reinforcements in a constant configuration throughout the length. The conventional prestressing system applies almost uniform prestressing to the entire crosstie, even where the prestressing is unnecessary, such as end regions and compression zones. The excessive stress concentration at the end zones often leads to the development of end-splitting cracks. A new prestressing system with adjustable wire configuration is proposed in this study using shape memory alloys (SMAs). The proposed system allows prestressing force to be applied only at target regions in the crosstie. The proposed prestressing system will help in: 1) Controlling end-splitting cracks, 2) Adjusting prestressing force depending on the demands at rail seat and center regions, and 3) Varying reinforcement configuration in crosstie section along the length. In the proposed system, pre-strained SMA reinforcement is placed in the forms prior to casting the concrete at the locations where prestressing is needed. After concrete is set, prestressing force is activated by heating the SMA reinforcement using electrical resistivity. This paper presents a proof-of-concept experimental study of the new prestressing scheme. Three small scale concrete crosstie specimens with different SMA wire configurations are tested. Digital Image Correlation (DIC) and strain gauges are used to monitor strain distribution along the crosstie during and after prestressing application. The results show that the proposed SMA prestressing system is effective in locally prestressing the regions where concrete cracking is expected. *Missed this Session or want to view it again? Stop by the VirtualAREMA kiosk located in the Registration area to purchase this product today!