Structures Laboratory

Purpose: The approximately 600,000 bridges, including bridges on the National Highway System, as well as bridges maintained and operated by various state and local entities are essential of our Nation's mobility. The Structures Laboratory is a unique facility of the Federal Highway Administration (FHWA) that specializes in developing and testing innovative bridge designs, materials, and construction processes that promise more efficient and 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 others. 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.

Description: The Structures Lab 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 metallic material testing facility.

The main Structures Laboratory is a state-of-the-art facility for indoor testing of full-scale bridge structures and large components. This laboratory, built in 1984, consists of a strong floor with a universal loading frame whose configuration can be customized to erect and test full-scale bridges. This strong floor measures 55.2 by 15.5 m (181 by 51 ft) and includes a grid of 573 tie-down holes. Two 178-kN (20-ton) overhead cranes service the entire floor area and can operate separately or together to unload trucks, erect structures, and set up experiments.

The annex structures laboratory facility—the original Structures Lab—was built in the 1960s, and it is still operating to provide additional testing capability. The annex structures laboratory facility has a strong floor area measuring 3.7 by 12 m (12 by 40 ft) and one 89-kN (10-ton) 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 21.35-m-long (70-ft-long) span with a width of 3.95 m (13 ft), and the outdoor strong floor measures 7.6 by 9.2 m (25 by 30 ft).

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

The metallic material testing lab is used to evaluate a wide variety of material properties of small test specimens, including fracture toughness, fatigue resistance, and strength. The laboratory also allows researchers to microscopically examine fracture surfaces and the microstructures of metallic materials and welds.

Laboratory Equipment: The Structures Laboratory and facilities contain the following equipment.

• Numerous static load actuators of 44- to 8896-kN (10,000- to 2,000,000-lbf) capacity. Numerous dynamic load actuators of 10,000-lb to 220,000-lb capacity.
• Numerous dynamic load actuators of 44- to 979-kN (10,000- to 220,000-lbf) capacity.
• State-of-the-art data acquisition with the capability to perform very large structural experiments with thousands of channels.
• Numerous instruments to measure load, displacement, rotation, and strain in structures.
• Four mechanical testing and simulation servo-hydraulic load frames, two Charpy V-notch testers, and two hardness testers.
• Microscopes and metallurgical testing equipment.
• Cementitious composite mixing, casting, and curing equipment.
• Portable telemetric data acquisition systems for field instrumentation of structures.
• Software licenses to perform advanced, nonlinear finite element modeling of structural behavior.

Uses: The Structures Laboratory and facilities continue to perform the following activities.

• Fundamental research into the strength, fatigue resistance, serviceability, and safety of bridge structures and components.
• 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 super- and substructure interfaces.