Aging of In-Service FRP Bridge Components
Applications of Fiber Reinforced Polymer (FRP) Composites with glass or carbon fibers and thermoset resins have been growing steadily with an increased number of bridge applications in the field. Pultruded FRP
composite bridge decks and FRP-wrapped concrete systems have been in service for over two decades. However, durability of these composites under varying pH levels, freeze-thaw conditions, fatigue and creep are still not thoroughly understood [International Workshop on Aging of Composites, Final Report by G Hota et al, Sponsored by USDOT-FHWA/NSF, Feb 2014]. Therefore, durability response is being studied using accelerated aging techniques in the presence of water and salt solutions including freeze-thaw effects under laboratory conditions. The degradation rates under different chemo-thermo-mechanical-environments in the lab are being documented. However, the data needs to be calibrated with the field data to
arrive at appropriate knock-down (reduction factors) for strength and
stiffness. Therefore, the goal is to collect field samples of those in-service bridges of varying aging conditions and calibrate the field aging parameters with the accelerated aging test data.
are: 1) to summarize the state-of-knowledgebase overview on aging of FRP
infrastructure systems including data from in-service FRP composite highway structures;
2) to develop material and component resistance factors based on the available data;
3) to collect additional aging data of in-service FRP highway structures and
integrate with information from literature; and 4) to evaluate thermo-mechanical
property degradation and develop prediction models including material and
component resistance (knock-down) factors.
The West Virginia University Constructed Facilities Center has been working on accelerated aging under lab conditions since 1994. Likewise many other universities and government labs have been developing aging data in the past 20 years for FRPs common in infrastructure. Over 500 papers have been collected by various researchers and practitioners on this topic and synthesized most of that information in terms of strength and stiffness degradation rates under varying parameters over a period of time (pH, free-thaw, temperature, moisture levels, etc.). In addition, mechanisms of degradation have been identified including certain theoretical developments to correlate the experimental data. This extensive amount of previous work available in the literature has yet to provide agreed upon materials resistance (knock-down factors), but has laid the groundwork to develop these factors. Several researchers under federally sponsored research programs (e.g. Laio (1998), Karbhari (2003) and GangaRao (2008), NCHRP 10-55, NCHRP 10-73) have succinctly summarized the literature on aging.
FRP when used in strengthening applications enables extending the service life of existing structures (Grand Challenge 1) and when used in the construction of decks helps accelerate bridge construction (Grand Challenge 3). This research will help address these two Grand Challenges indirectly, but more importantly, it will fill a knowledge gap that is directly related to Grand Challenge 5 (Monitoring Bridge Condition). Findings from this research would benefit the large majority of DOTs who already have in their inventory structures built using pultruded FRP decks or strengthened using externally-bonded FRP systems. As such, AASHTO Committee T6 (Fiber Reinforced Polymer Composites) has endorsed this RNS.
|Sponsoring Committee:||AKB10, Innovative Highway Structures and Appurtenances
|Research Period:||24 - 36 months|
|RNS Developer:||Prof. Hota GangaRao, P.E.|
|Index Terms:||Fiber reinforced polymers, Composite materials, Bridge decks, Freeze thaw durability, Creep, Fatigue (Mechanics), Service life, Aging (Materials), Aging infrastructure, |
Maintenance and Preservation
Bridges and other structures