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U.S. Department of Transportation U.S. Department of Transportation Icon United States Department of Transportation United States Department of Transportation
OFFICE OF RESEARCH, DEVELOPMENT, AND TECHNOLOGY AT THE TURNER-FAIRBANK HIGHWAY RESEARCH CENTER

Structures Laboratory Overview

Laboratory Purpose

Laboratory Description

Laboratory Capabilities

Laboratory Services

Laboratory Equipment

Recent Accomplishments and Contributions

Laboratory Purpose

There are approximately 618,000 bridges in the United States, including bridges on the National Highway System and bridges maintained and operated by various State and local entities. These bridges are essential to our Nation's mobility. The Structures Laboratory is a unique facility at Federal Highway Administration’s (FHWA’s) Turner-Fairbank Highway Research Center that specializes in developing and testing bridge designs, materials, and construction processes that promise safer and more efficient structures in the Nation's highway system.

The purpose of the Structures Laboratory is to support FHWA's strategic focus on improving mobility through analytical and experimental studies to determine the behavior of bridge systems under typical and extreme loading conditions. These experimental studies may also include tests of bridge systems developed to enhance bridge durability and constructability over time. Data from these studies help upgrade national bridge design specifications and improve the safety, reliability, and cost effectiveness of bridge construction in the United States.

The Structures Laboratory also provides bridge failure forensic investigation services to State departments of transportation, FHWA divisions, National Transportation Safety Board (NTSB), and other organizations. Through this forensic service, the laboratory determines the causes of bridge structural failures and develops practices and procedures to help avoid similar failures from occurring in the future.

Laboratory Description

The Structures Laboratory has the capability to perform a broad range of tests to characterize the performance of bridge structures and structural systems. This capability resides in five individual facilities: the main Structures Laboratory, the annex structures laboratory facility, the outdoor testing facilities, the computer modeling and simulation facility, and the material testing facility.

Laboratory Capabilities

The main Structures Laboratory (figure 1) is a state-of-the-art facility for indoor testing of full-scale bridge structures and large components under static and dynamic loads. This laboratory, built in 1984, consists of a strong floor and reconfigurable loading frames that can be customized to erect and test structural components and full-scale bridges. This strong floor measures 181 by 51 feet (55.2 by 15.5 meters) and includes a grid of 573 tie-down holes. Static loads are applied using a large inventory of hydraulic rams. Dynamic loads are applied using a network of closed-loop servo-hydraulic test stations. Two 20-ton (178-kilonewton) overhead cranes service the entire floor area and can operate separately or together to erect structures, and set up experiments.

"Overview of the FHWA Structural Testing Laboratory. On the left there is a pretensioned concrete bridge girder that is being supported at its ends and is being subjected to a vertically downward load at its midspan. On the right, a steel truss with a gusset plate connection is being stressed within a reinforced concrete loading frame."

Figure 1. The main Structures Laboratory showing: (1) Full-scale pretensioned girder load capacity experiment in blue load frame (left) and (2) Concrete reaction wall (center) used to perform steel gusset plate experiments.

The annex structures laboratory facility—the original Structures Laboratory—was built in the 1960s and still provides additional testing capability. The annex structures laboratory facility has a strong floor area measuring 12 by 40 feet (3.7 by 12 meters) and has one 15-ton (89-kilonewtons) overhead crane.

The Structures Laboratory's outdoor testing facilities, consisting of permanent geosynthetic reinforced soil abutments and an outdoor strong floor, were constructed during the late 1990s to provide additional capacity for testing large-scale components subjected to environmental loading. The permanent test abutments cover a single 70-foot long (21.4 meters long) span with a width of 13 feet (4.0 meters), and the outdoor strong floor measures 25 by 30 feet (7.6 by 9.2 meters).

The material testing laboratory maintains the capability to evaluate a wide variety of material properties of steel and concrete, including strength, elastic modulus, dynamic fracture toughness, static fracture toughness, and fatigue crack growth. Digitally controlled servo-hydraulic load frames are used for fracture and small specimen material strength testing. The laboratory also maintains the capability to perform microscopic examination of fracture surfaces and the microstructure of metallic materials and welds. These capabilities are utilized to support the research activities in the Structures Laboratory and to assist in forensic evaluation of failures in the field.

The computer modeling and simulation laboratory allows researchers to build and analyze detailed models capable of simulating experimental test results with very high accuracy.

Laboratory Services

The Structures Laboratory provides the following services:

  • Fundamental research into the strength, fatigue resistance, serviceability, and safety of bridges, bridge components, and other highway structures.
  • Applied research to assess the suitability of various structural components and systems for different services.
  • Field evaluation of in-service structures.
  • Forensic evaluation of structural failures.
  • Systems integration at superstructure and substructure interfaces.

Laboratory Equipment

The Structures Laboratory and facilities contain the following equipment.

  • Numerous static and dynamic load actuators of 10,000 to 2 million pound force (44- to 8,896-kilonewton-) capacity.
  • State of the art data acquisition with the capability to perform very large structural experiments.
  • Numerous instruments to measure load, displacement, rotation, and strain in structures.
  • Servohydraulic Load Frames:
      • One uniaxial load frame with an axial load capacity of 22 kips in compression and 22 kips in tension.
      • One uniaxial load frame with an axial load capacity of 1,000 kips in compression and 509 kips in tension.
      • One uniaxial load frame (figure 2) with an axial load capacity of 550 kips in compression and 550 kips in tension.
      • Two reconfigurable load frames (figure 3), each with axial load capacity of 1,000 kips for static test and 550 kips for dynamic tests.
      • One uniaxial load frame with an axial load capacity of 220 kips and 220 kips in tension.
      • One uniaxial load frame (figure 4) with an axial load capacity of 110 kips in compression and 110 kips in tension.
  • One electromechanical load frame with an axial load capacity of 22 kips in tension and compression.
  • A Charpy V-notch tester and two hardness testers.
  • Microscopes and metallurgical testing equipment.
  • Video extensometer systems.
  • Three-dimensional laser measurement system with a volumetric accuracy up to 0.002 inches (0.049 millimeters) with a diameter range up to 361 feet (100 meters).
  • Cementitious composite mixing, casting, and curing equipment.
  • Software licenses to perform advanced, nonlinear finite element modeling of structural behavior.

 

"A threaded steel rod is being subjected to a uniaxial tensile load within a testing machine. The rod is held at both ends by large side-loading hydraulic grips. The rod has fractured near its midpoint due to the applied load."

Figure 2. Image of 550-kip servohydraulic test frame in the Material Testing Laboratory performing a tensile test on a large diameter threaded rod.

"A 62-foot long, 35-inch deep pretensioned concrete bridge girder is being subjected to structural loading. The girder is supported at each end and is being subjected to a vertically downward load at its midspan. Instrumentation and lighting are concentrated toward midspan where the load is applied."

Figure 3. Image of a full-scale load capacity experiment showing: 1) large-scale pretensioned concrete girder being subjected to flexural loading and 2) load frames serving as reaction points through which the loading is applied.

"A servohydrualic test uniaxial test frame is being used to test the structural response of a pair of steel pretensioning strands that are spliced within a block of ultra-high performance concrete. The actuator is located in the bottom of the frame and the load cell is located near the frame’s crosshead near the top of the frame."

Figure 4. Picture of 110-kip servohydraulic test frame in the Material Testing Laboratory performing a test on the bond and splice length of prestressing strand embedded in ultra-high performance concrete.

Recent Accomplishments and Contributions

Mohebbi, A., B. Graybeal, and Z. Haber. (2022). “Time-Dependent Properties of Ultrahigh-Performance Concrete: Compressive Creep and Shrinkage,” Journal of Materials in Civil Engineering, V. 34, No. 6, 15 pp., DOI: 10.1061/(ASCE)MT.1943-5533.0004219.

El-Helou, R., Z. Haber, and B. Graybeal. (2022). “Mechanical Behavior and Design Properties of Ultra-High-Performance Concrete,” ACI Materials Journal, V. 119, No. 1, pp. 181-194, DOI: 10.14359/51734194.

El-Helou, R., and B. Graybeal. (2022). “Shear Behavior of Ultra-High Performance Concrete Pretensioned Bridge Girders,” Journal of Structural Engineering, V. 148, No. 4, 13 pp., DOI: 10.1061/(ASCE)ST.1943-541X.0003279.

El-Helou, R., and B. Graybeal. (2022). “Flexural Behavior and Design of Ultrahigh-Performance Concrete Beams,” Journal of Structural Engineering, V. 148, No. 4, 20 pp., DOI: 10.1061/(ASCE)ST.1943-541X.0003246.

Muzenski, A., Z. Haber, and B. Graybeal. (2022). “Interface Shear Behavior of Ultra-High Performance Concrete,” ACI Structural Journal, V. 119, No. 1, 14 pp., DOI: 10.14359/51733008.

Mohebbi, A., and B. Graybeal. (2022). “Prestress Loss Model for Ultra-High Performance Concrete,” Engineering Structures, v. 252, 14 pp., DOI: 10.1016/j.engstruct.2021.113645.

Padilla-Llano, D., and J. Ocel. (2021). “Qualification of Electroslag Welds made from HPS 485W (70W) and 345W (50W) Steels,” Journal of Constructional Steel Research, V. 183, 12 pp., DOI: 10.1016/j.jcsr.2021.106705.

Ocel, J. (2021). “Historical Changes to Steel Bridge Design, Composition, and Properties,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-21-020, 67 pp.

Graybeal, B., E. Brühwiler, B.-S. Kim, F. Toutlemonde, Y. Voo, and A. Zaghi. (2020). “International Perspective on UHPC in Bridge Engineering,” Journal of Bridge Engineering, V. 25, No. 11, 16 pp., DOI: 10.1061/(ASCE)BE.1943-5592.0001630.

Beckett, C., and J. Ocel. (2021). “Evaluation of Holes Fabricated Using Plasma Arc Cutting,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-20-056, 159 pp.

Russian, O., and J. Ocel. (2020). “Mechanical Performance of Welds Using ASTM A709 Grade 50CR Steel as Base Metal,” Journal of Constructional Steel Research, V. 170, DOI:10.1016/j.jcsr.2020.106121.

Haber, Z., B. Graybeal, and B. Nakashoji. (2020). “Ultimate Behavior of Deck-to-Girder Composite Connection Details Using UHPC,” Journal of Bridge Engineering, V. 25, No. 7, 14 pp., DOI:10.1061/(ASCE)BE.1943-5592.0001574.

Holt, R., and B. Graybeal. (2020). “Florida International University Pedestrian Bridge Collapse Investigation: Assessment of Bridge Design and Performance,” NTSB Accident ID: HWY18MH009, Federal Highway Administration, 90 pp.

Graybeal, B., and Z. Haber. (2019). “Turner-Fairbank Highway Research Center Factual Report: Concrete Interface Under Members 11 and 12,” NTSB Accident ID: HWY18MH009, Federal Highway Administration, 15 pp.

Ocel, J., B. Graybeal, and Z. Haber. (2018). “Turner-Fairbank Highway Research Center Factual Report: Steel and Concrete Materials Testing,” NTSB Accident ID: HWY18MH009, Federal Highway Administration, 46 pp.

Ocel, J., B. Graybeal, and Z. Haber. (2018). “Turner-Fairbank Highway Research Center Factual Report: Final: Post-Tensioning System Performance Testing,” Federal Highway Administration, 23 pp.

Provines, J., J. Ocel, and K. Zmetra. (2019). “Strength and Fatigue Resistance of Clustered Shear Stud Connectors in Composite Steel Girders,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-20-005, November 2019, 250 pp.

Ocel, J., J. Provines, V. Charito, and G. Jizba. (2019). “Residual Strength of Cable Stay Strands from Blast Qualification,” Journal of Bridge Engineering, V. 24, No. 8, DOI:10.1061/(ASCE)BE.1943-5592.0001452.

Graybeal, B., and R. El-Helou. (2019). “Development of an AASHTO Guide Specification for Ultra-High Performance Concrete,” Proceedings, 2nd International Interactive Symposium on UHPC, 9 pp., DOI: 10.21838/uhpc.9708.

El-Helou, R. and B. Graybeal. (2019). “The Ultra Girder: A Design Concept for a 300-foot Single Span Prestressed Ultra-High Performance Concrete Bridge Girder,” Proceedings, 2nd International Interactive Symposium on UHPC, 9 pp., DOI: 10.21838/uhpc.9707.

Mohebbi, A., Z. Haber, and B. Graybeal. (2019). “Evaluation of AASHTO Provisions for Creep and Shrinkage of Prestressed UHPC Girders,” Proceedings, 2nd International Interactive Symposium on UHPC, 10 pp., DOI: 10.21838/uhpc.9706.

Graybeal, B. (2019). “Design and Construction of Field-Cast UHPC Connections,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-19-011, 44 pp.

Greene, G., and B. Graybeal. (2019). “Lightweight Concrete: Shear Performance,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-15-022, 326 pp.

Greene, G., and B. Graybeal. (2019). “Lightweight Concrete: Transfer and Development Length of Prestressing Strands,” FHWA, U.S. Department of Transportation, Report No. FHWA-HIF-19-018, 206 pp.

Graybeal, B., and F. Baby. (2019). “Tension Testing of Ultra-High Performance Concrete,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-053, 206 pp.

Haber, Z., and B. Graybeal. (2018). “Performance of Grouted Connections for Prefabricated Bridge Deck Elements,” FHWA, U.S. Department of Transportation, Report No. FHWA-HIF-19-003, 156 pp.

Haber, Z., J. Muñoz, I. De la Varga, and B. Graybeal. (2018). “Bond Characterization of UHPC Overlays for Concrete Bridge Decks: Laboratory and Field Testing,” Construction and Building Materials, V. 190, pp. 1056-1068.

Graybeal, B., Z. Haber, I. De la Varga, and R. Spragg. (2018). “Accelerated Construction of Robust Bridges through Material and Detailing Innovations,” Proceedings, 9th International Conference on Bridge Maintenance, Safety, and Management, Melbourne, Australia, 8 pp.

Haber, Z. and B. Graybeal. (2018). “Lap-Spliced Rebar Connections with UHPC Closures,” Journal of Bridge Engineering, V. 23, No. 6, 12 pp., DOI:10.1061/(ASCE)BE.1943-5592.0001239.

Haber, Z., I. De la Varga, B. Graybeal, B. Nakashoji, and R. El Helou. (2018). “Properties and Behavior of UHPC-class Materials,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-18-036, 153 pp.

De la Varga, I., Z. Haber, and B. Graybeal. (2018). “Enhancing Shrinkage Properties and Bond Performance of Prefabricated Bridge Deck Connection Grouts: Material and Component Testing,” ASCE Journal of Materials in Civil Engineering, V. 30, No. 4, 12 pp.

Yuan, J., B. Graybeal, and K. Zmetra. (2018). “Adjacent Box Beam Connections: Performance and Optimization,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-093, 129 pp.

Ocel, J., J. Provines, and V. Charito. (2018). “Cable-Stay Strand Residual Strength Related to Security Threats,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-109, 100 pp.

Haber, Z., B. Graybeal, B. Nakashoji, and A. Fay. (2017). “New, Simplified Deck-to-Girder Composite Connections Using UHPC,” Proceedings, 2017 National Accelerated Bridge Construction Conference, Miami, 10 pp.

Swenty, M., and B. Graybeal. (2017). “Characterization of Materials Used in Field-Cast Precast Concrete Connections,” PCI Journal, Nov-Dec, pp. 33-44.

Ocel, J. (2017). “Behavior of a Steel Girder Bolted Splice Connection,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-042, 86 pp.

Graybeal, B. (2017). “Adjacent Box Beam Connections: Performance and Optimization,” TechNote, FHWA-HRT-17-094, 12 pp.

Graybeal, B. (2017). “Emerging UHPC-Based Bridge Construction and Preservation Solutions,” Proceedings, UHPFRC 2017, Montpellier, France, 10 pp.

Graybeal, B., and Z. Haber. (2017). “Ultra-High Performance Concrete for Bridge Deck Overlays,” FHWA, U.S. Department of Transportation, TechNote, FHWA-HRT-17-097, 16 pp.

Haber, Z., J. Munoz, and B. Graybeal. (2017). “Field Testing of an Ultra-High Performance Concrete Overlay,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-096, 57 pp.

Ocel, J., B. Cross, W. Wright, and H. Yuan. (2017). “Optimization of Rib-to-Deck Welds for Steel Orthotropic Bridge Decks,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-17-020, 121 pp.

Maya Duque, L.F., and B. Graybeal. (2017). “Experimental Study of Strand Splice Connections in UHPC for Continuous Precast Prestressed Concrete Bridges,” Engineering Structures, V. 133, pp. 81-90, DOI: 10.1016/j.engstruct.2016.12.018.

Maya Duque, L.F., and B. Graybeal. (2017). “Fiber Orientation Distribution and Tensile Mechanical Response of UHPFRC,” Materials and Structures, V. 50, No. 1, 17 pp. DOI: 10.1617/s11527-016-0914-5.

Graybeal, B. (2017), “Bond of Field-Cast Grouts to Precast Concrete Elements”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-16-081.

Beckett, C. and J. Ocel. (2016). “Evaluation of Bolt Holes Fabricated by Using Plasma Arc Cutting,” Transportation Research Record: Journal of the Transportation Research Board, No. 2573, Transportation Research Board, Washington, D.C., pp. 134–142, DOI: 10.3141/2573-16.

Graybeal, B. (2016). "Dimensional Stability of Grout-Like Materials Used in Field-Cast Connections," FHWA, U.S. Department of Transportation, TechNote No. FHWA-HRT-16-080, 12 pp.

Ocel, J. (2015) and Provines, J., “Properties of Anchor Rods Removed from San Francisco-Oakland Bay Bridge”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-15-057.

Ocel, J. (2014), “Interlaboratory Variability of Slip Coefficient Testing for Bridge Coating”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-093.

Graybeal, B. (2014), “Design and Construction of Field-Cast UHPC Connections”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-084.

Ocel, J (2014), “Fatigue Testing of Galvanized and Ungalvanized Socket Connections”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-066.

Ocel, J (2014), “Slip and Creep of Thermal Spray Coatings”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-083, .

Ocel, J. (2014), “Guidelines for Design and Rating of Gusset-Plate Connections for Steel Truss Bridges”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-063.

Graybeal, B. (2014), “Lightweight Concrete: Development of Mild Steel in Tension,” FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-030.

Graybeal, B. (2014), “Splice Length of Prestressing Strand in Field-Cast Ultra-High Performance Concrete Connections”, FHWA, U.S. Department of Transportation, Report No. FHWA-HRT-14-041.

Last updated: Friday, January 20, 2023