In-Service Performance Evaluation and Monitoring of a Hybrid Composite Beam Bridge System

About the report:

The hybrid composite beam (HCB) technology has been presented as a system for short and medium span beam bridges as an alternative to traditional materials such as concrete and steel. An HCB consists of a concrete tied arch encased in a fiber-reinforced polymer shell. When compared to traditional materials, the HCB system is lighter in weight, which allows for multiple members to be transported on a single truck and smaller cranes to be used during construction, and even reuse of existing substructures. In addition, the protective nature of the FRP outer shell provides additional resistance to corrosion for the reinforcement internal to the system, potentially offering an extended lifespan over conventional girders. Similar to other beam-type bridges for highways, the HCB system is made composite with a conventionally reinforced concrete deck.

This study was conducted as a means of evaluating HCB girders for use in a skewed bridge project as a replacement for the existing bridge that crossed Tides Mill Stream along Route 205 in Colonial Beach, Virginia. The existing bridge structure was a short span (~40 ft) simply supported concrete girder bridge with 45° skew and served as a primary connector route for the Colonial Beach community. With respect to the HCB system for bridges, previous testing and applications had been limited to straight bridges, and the Virginia Department of Transportation (VDOT) wished to gather more information on the behavior of these complicated HCBs in a skewed configuration. The primary goal of the investigation was to gain a better understanding of the system behavior including how the loads are transmitted, both at the system and element levels, and also to provide recommendations on how the structure might be inspected and evaluated in the future to ensure the beams are healthy, despite the inability to visually inspect the crucial load carrying components encased in the fiberglass shell.

This study was the second phase of the overall study on the HCB system and followed a laboratory study at Virginia Tech, which focused on the behavior of both the individual HCB members and a full-scale girder bridge configuration. The study presented herein focused on an in-service live load test of the bridge constructed by VDOT across Tides Mill Stream. The live load testing program included the evaluation of lateral load distribution, dynamic load allowance, and the internal load sharing behavior of the HCB members. With respect to the live load performance, the HCB system generally conformed to the provisions of the AASHTO specifications for beam-type bridges but did exhibit some characteristics of a flexible system when the dynamic response was considered. It was also noted that the load sharing behavior within the HCB system was non-composite, with the exterior fiber-reinforced polymer shell behaving somewhat independently of the internal tied arch. In addition to the load-testing program, this study provides recommendations on potential non-destructive evaluation methods that may be appropriate for evaluating the condition of this type of structure.

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