As of October 1, 2016, the SWUTC concluded its 28 years of operation and is no longer an active center of the Texas A&M Transportation Institute. The archived SWUTC website remains available here.


SWUTC Research Project Description

Sustainability of Transportation Structures Using Composite Materials to Support Growth and Trade

University:  Texas A&M University

Principal Investigator:
Stefan Hurlebaus
Texas Transportation Institute
(979) 845-9570

Project Monitor:
Gil Heldenfels
Vice President & General Manager
Heldenfels Enterprises, Inc.
5700 IH-35 South (Exit 199)
San Marcos, TX 78666

Funding Source:  USDOT and State of Texas General Revenues

Total Project Cost: $59,879

Project Number:  600451-00009

Date Started: 4/1/12

Estimated Completion Date:  3/31/13

Project Summary

Project Abstract:
The goal of this research project is to evaluate the performance of aramid fiber reinforced polymer (AFRP) composite bars in full-scale, prestressed concrete bridge girders in lieu of conventional prestressing steel tendons to overcome issues of corrosion since approximately two-thirds of the total bridges in the United States consist of prestressed steel reinforced concrete which are susceptible to corrosion-induced deterioration [1]. For instance, in 1997, the Intermodal Surface Transportation Efficiency Act (ISTEA) spent $2.5 billion for the highway bridge replacement program, where the majority of the funds went towards replacement or rehabilitation of bridge decks that were damaged due to corrosion. Bridge repairs alone are estimated to require $65 billion for the U.S. interstate highway system that was designed and built in the 50s and 60s compared to $5 billion allocated by the president of the U.S. for cancer research through the National Institute of Health (NIH).

Project Objectives:
The objectives of this study are (1) to design a full-scale AASHTO I-girder (Type I) with pre-tensioned AFRP tendons, (2) to construct and fabricate the girder and the topping slab, (3) to instrument and test the composite girder/slab, (4) to compare the experimental results with a control specimen, and (5) to develop a computational model to predict the pre-stress losses.

Task Descriptions:
Task 1: Literature Review
The research team will compile a literature review, using the Transportation Research Information Service, TRIS, as well as other library sources of reference material to fully document the state of the practice and state of the art on the use of AFRP bar for prestressing bridge girders. The research team has significant experience and expertise with AFRP material, structural modeling, experimental design and testing, and structural design.

Task 2: Design of Full-Scale Girder and Topping Slab
Task 2 of studies is to investigate the design issues from serviceability point of view for a 40′ full-scale, AASHTO I-girder (Type I) with pretensioned AFRP tendons. Specifically, the following items are to be studied: load-deflection and moment-curvature relationships, post-cracking flexural stiffness, induced deformability by cracking up to failure, shear strength of the girder close to the anchorage zone, prestress loss in AFRP tendons, effect of tension stiffening in post-serviceability regions [6], and crack width versus the stress level in AFRP bars.

Task 3: Construction and Fabrication of Full-Scale Girder and Topping Slab
Task 3 includes addressing the constructability issues and implementation process such as applicability of the proposed prestressing system, sufficiency of the shear connectors between the precast topping slab and prestressed girder, feasibility of the idea of using AFRP headed bar as shear reinforcement to avoid using bent bars (stirrups) with low strength capacity, and the required cost for construction and implementation compared to conventional steel case. It is the current thinking of the research team 40′ full-scale, AASHTO I-girder (Type I) with pretensioned AFRP tendonsHeldenfels Enterprises, Inc.High-Bay Structural and Materials Testing (HBSMT) Laboratory

Task 4: Instrumentation and Experimental Testing of the Composite Section
Instrumentation of the specimens is required to monitor deflection and strains in the girder during load testing to failure. Strain gages attached to the reinforcement will measure the strains associated with the loading of the specimens. The strain gages will also be temperature compensated by matching the coefficients of expansion of the carrier and gage alloy to the properties of the AFRP bar so that any expansion of the rebar due to temperature modification will be mirrored by the expansion of the strain gage. In addition to the strain gages attached to the reinforcement, string pots will be used to measure the global displacements of the girder under loading from hydraulic actuators. Note, that all hardware and permanent sensors are already available in the Civil Engineering Structural and Materials Testing Laboratory. The only materials required for specimen instrumentation are the disposable sensors, such as the foil strain gages.
The strength and cracking behaviors of the test specimens will be used to determine the flexural capacity of bridge deck system. The specimen will be tested to failure. As discussed previously, an actuator will be used to apply loading to the specimen in a displacement controlled fashion such that important response can be measured during pre-crack conditions (structurally induced), through specimen yielding, and finally to ultimate failure of the specimen. Instrumentation, as described previously, will be used to measure important specimen response both at the global level (actuator forces and specimen deformations at critical locations) and also at the local level. The specimen response will be utilized in Task 5 of the computational program.

Task 5: Analysis of the Experimental Data and Development of the Computational Models
After the completion of Task 4 the experimental data will be analyzed. Specifically, the following items will be analyzed: load-deflection and moment-curvature relationships, post-cracking flexural stiffness, induced deformability by cracking up to failure, shear strength of the girder close to the anchorage zone, prestress loss in AFRP tendons, effect of tension stiffening in post-serviceability regions, and crack width versus the stress level in AFRP bars.
Then a rigorous numerical analysis using a computational model which will be developed, will be compared with experimental data to better calibrate the model for design purposes. The relaxation loss profiles of the AFRP tendons, which have been less well understood given lack of sufficient experimental data, will also be investigated by to calibrate the computational model for better estimation of the prestress losses. This experimentally validated model will be used to gain new insight into the structural performance of the bridge deck system in different stages of serviceability. The anticipated results are expected to add to the knowledge base of prestressed AFRP tendons for design and implementation that not only enhances the durability of the bridge deck system but also has a broader impact on design of marine structures and parking garages, which are subjected to highly corrosive environment.

Task 6: Dissemination of Results
The final project report will comprehensively document all work performed. This will include the literature review; design procedure of the prestressed AFRP girder, the fabrication of the girder, the experimental setup and procedures, experimental results, and the computational model. Of particular importance, the project will provide documentation on the expected performance of prestressed AFRP girder compared with conventional prestressed steel girder. The report will be presented in a logical format so that engineers can quickly and easily obtain data from within the report.

Implementation of Research Outcomes:
Corrosion-induced deterioration of steel rebar is one of the main reasons for repair and rehabilitation programs for conventional steel-reinforced concrete bridge decks. To overcome corrosion-induced structural issues, researchers have introduced and applied fiber-reinforced polymer (FRP) bars, over the past couple of decades, as a corrosion-resistant candidate for either conventional reinforcing steel or prestressing strands. High strength-to-weight ratio, corrosion resistance, and accelerated construction due to ease of placement of the bars and implementation are the special characteristics that make these bars an appealing alternative for either steel-reinforcing bars or prestressing strands.

This study presents the experimental and analytical investigations of structural performance of a full-scale American Association of State Highway and Transportation Officials (AASHTO) I-girder Type I, reinforced and prestressed with aramid-fiber-reinforced polymer (AFRP) bars, where the bridge girder is composite with a topping deck. The major objectives of this research included evaluating:

  • The constructability.
  • The load and deformation capacities under either flexure or shear tests.
  • The structural performance per AASHTO load and resistance factor design (LRFD) criteria.

Products developed by this research:

Journal Publication:  Computational Modeling of the Flexural Performance of an AFRP Prestressed Girder with a Composite Bridge Deck, S. Pirayeh Gar, M.H. Head, S. Hurlebaus, Texas A&M University, published in the ACI Structural Journal, Vol. 110, No. 6, pp. 965-975, 2013.

Thesis:  Evaluation of Advanced Construction Materials for Sustainable and Durable Infrastructure, Michelle Prouty, Texas A&M University, MS thesis, 2014

Thesis:  Aramid Fiber for Prestressed Bridge Girders, Wesley Cummings, Texas A&M University, MS thesis, 2014

New Technology:  This research also developed and extensively tested a new anchorage system to improve the gripping capacity and sustainability performance during conventional stressing techniques on aramid-fiber-reinforced polymer (AFRP) bars.

Journal Article in Preparation:  Practical Anchorage System for FRP Prestressed Concrete Bridges, W. Cummings, S. Pirayeh Gar, S. Hurlebaus, Texas A&M University, Journal TBD.

Impacts/Benefits of Implementation:
The results of this research confirm the adequate strength and deformation capacities of the composite girder, satisfying the AASHTO LRFD criteria.

Web Links:

Final Technical Report