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Title:Z-Spike Rejuvenation to Salvage Timber Railroad Bridge Members
Authors:Nathan J. Miller, Richard M. Gutkowski, Jeno Balogh, and Don W. Radford
University:Colorado State University
Publication Date:Dec 2008
Report #:MPC-08-208
Project #:MPC-275
TRID #:01123443
Keywords:bridge members, fiber reinforced plastics, railroad bridges, repairing, spikes, timber
Type:Research Report – MPC Publications


This research study examined the effectiveness of the fiber reinforced polymer (FRP) spikes in repairing naturally damaged and deteriorated railroad bridge chords. Past research has shown that this process can be quite effective in improving the effective stiffness of railroad chord members that were intentionally damaged. This shear spiking process involves inserting the FRP spikes vertically into railroad bridge members. The spikes are held in place by an adhesive and are intended to repair horizontal cracks that develop in the members over the course of their lifespan.

This study included three specimens that were of varying size and damage conditions. In each case, the spiking technique as well as the overall improvement in specimen stiffness was analyzed. This report summarizes the spiking process used in each specimen as well as the results. It was found that the increase in the stiffness of the specimens was highly dependent on the initial condition of the specimens. The last specimen in the study showed the most promising results as it was also the most damaged. The spikes were installed in slightly oversized holes with epoxy resin as the adhesive. This specimen experienced a 267% increase in the initial effective stiffness when loaded to 15 kips. After a test to 39 kips, this increase was reduced to 179%. This result confirms the potential for shear spiking as a highly effective tool for in situ repair of damaged or deteriorated railroad bridge beams.

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