Semester

Summer

Date of Graduation

2026

Document Type

Problem/Project Report

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Hota GangaRao

Committee Co-Chair

P. V. Vijay

Committee Member

Ruifeng Liang

Abstract

ABSTRACT

Experimental Evaluation of 100 ft x 10 ft FRP Truss Pedestrian Bridge

Ashish Dhital

FRP truss bridges are now increasingly used in pedestrian bridge applications due to their high strength-to-weight ratio, corrosion resistance, better impact performance compared with conventional materials, and ease of assembly. These advantages make FRP systems attractive for accelerated construction, remote-site installation, and environments where steel or reinforced concrete bridges may experience corrosion-related deterioration. Due to insufficient data on both strength and serviceability (i.e deflection, frequency) performances. Full-scale testing of FRP pedestrian bridges of longer spans (50’-100’) is needed to better understand the dynamic behavior, long-term creep response, and system failure strength of FRP pedestrian truss bridges under realistic loading conditions, in accordance with the AASHTO 2025 LRFD Guide Specifications for FRP Pedestrian Bridges.

This study presents a field evaluation of a 100-ft × 10-ft pultruded FRP pedestrian truss bridge under different loading scenarios. The bridge responses were evaluated under dead load, 72 psf pedestrian live load, H-5 vehicular load (static and fatigue), lateral load, and free vibration. The three bridge configurations evaluated experimentally were: the original 100’ span bridge without and with a top cap, and the modified bridge (with a prestressed top chord) introducing camber during construction (assembly) of the bridge.

Various measuring devices were used to assess the structural response of the bridge. Strain gages, string potentiometers, dial gages, and accelerometers were installed to measure strain, displacement, and vibration response during testing. The field data from this instrumentation were used to evaluate the bridge's strength and serviceability performance under realistic loading conditions, including thermal response to varying temperatures. Responses from the three bridge configurations mentioned above were compared with responses from finite element analyses and with 2025 LRFD Guide Specifications to assess the adequacy of the bridges' performance. The effects of bridge modifications, prestressing, and the addition of a cap to top-chord members are discussed in this report.

The maximum strains in the FRP bridge members were below the allowable strain limits. None of the three bridge configurations met the L/360 limit for vertical deflection under the 90 psf live load; however, vertical deflection decreased with the addition of the top cap. To address this vertical deflection serviceability issue, further stiffness enhancement is necessary. The lateral deflection of the bridge under a 4.5-kip lateral load, representing the 10-year Mean Recurrence Interval (MRI) wind event, satisfied the L/360 deflection limit specified in the AASHTO 2025 LRFD Guide Specifications for FRP Pedestrian Bridges. A significant 17% reduction in live-load creep deflection was observed after the introduction of camber through prestressing of the top chord. Lateral torsional buckling (LTB) was observed under sustained 72 psf pedestrian live loading before capping the top truss members and was effectively mitigated by adding a top cap to the top chord. The vertical frequency did not meet the 5 Hz criterion but met the code-suggested minimum of 3 Hz, indicating acceptable vibration performance. This limitation can be overcome by increasing the overall bridge stiffness. All three bridge configurations met the 3 Hz lateral frequency requirement. Temperature variations can cause differences in the bridge's structural response.

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