Technology Digests / Hybrid-Composite Beam Spans: Revenue Service Results

TD23-023

November 29, 2023
Authors
  • Chris Johnson
  • Duane Otter
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Key Findings

  • The 42-foot HCB span began to show increased deflection and strains after nearly 490 MGT of heavy haul service. The 33-foot HCB span has not shown any change in structural performance after more than 500 MGT of heavy haul service.
  • Design details observed in the 42-foot span likely led to fabrication issues that resulted in premature structural deterioration.
  • The fiberglass casing prevented a direct inspection of the primary load carrying components of the HCB spans. This casing required that the structural performance be assessed using exterior measurements.
  • Failure of the deck-to-arch stirrups likely contributed to the increased deflections.
  • The span-to-depth ratio likely plays a key role in the longevity of the spans.

Hybrid-Composite Beam Spans: Revenue Service Results

As part of an ongoing evaluation of advanced materials and designs for use in railroad bridges, MxV Rail tested 33-foot and 42-foot hybrid-composite beam (HCB) spans in revenue service. The 42-foot span and a separate 30-foot HCB span had been tested previously at the Facility for Accelerated Service Testing (FAST®) near Pueblo, CO. This work was supported by the Association of American Railroads (AAR) under its Strategic Research Initiatives (SRI) Program. The HCB is composed of concrete, steel, and fiberglass components as described in Technology Digest TD09-019.1 The HCB system consists of a concrete arch, a concrete deck, and a vertical shear fin extending longitudinally from the top of the arch to the bottom of the deck. Steel prestressing tendons connect the ends of the arch. The concrete arch provides compression reinforcement, and the steel tendons provide the tension reinforcement. The entire structure is encased in foam with a fiberglass…