AASHTO Specification Development

The continued economic strength and growth of the United States is closely tied to the strength and reliability of our highway system. The key to improving this system is research: to develop, enhance and implement new design procedures, operational practices, construction methods, enhanced materials, and inspection technology. Too often this research is reactive, conducted in response to emergencies or tragic failures of infrastructure, such as those that occurred at the Silver Bridge, Mianus River Bridge, Cypress Street Viaduct, and the I-10 Escambia Bay Bridge. The goal of transportation agencies is to break that chain of failures by conducting proactive research that can be implemented prior to catastrophic failure. AASHTO, the FHWA and the NCHRP have been driving forces in their funding and support of proactive research. Modjeski and Masters (M&M) has been an active partner with them for decades.

In the late 1980s we were selected to lead a team of experts in the development of the AASHTO LRFD Bridge Design Specifications (LRFD). The new specifications utilize state-of-the-art analysis and design methodologies, and make use of load and resistance factors based on the known variability of applied loads, material properties and resistance models. The load and resistance factors are calibrated from actual bridge statistics. Bridges designed with the LRFD specifications should have more uniform levels of safety, which should lead to superior serviceability and long-term maintainability.

After more than 25 years of developing and maintaining LRFD specifications, M&M continues to hone its industry-leading expertise in bridge services through a number of efforts, including:

  • Guide Specifications for Bridges Vulnerable to Coastal Storms;
  • NHI Course No. 13061: “LRFD for Highway Bridges”;
  • NCHRP 20-7, Task 270, Application of AASHTO LRFD Specifications to Design of Sound Barriers;
  • NCHRP 12-78, Evaluation of Load Rating by Load and Resistance Factor Rating;
  • NCHRP 12-72, Blast Resistant Highway Bridges: Design and Detailing Guidelines, and;
  • FHWA’s Manual for the Design, Construction, and Maintenance of Orthotropic Steel Bridges.
  • Practical Applications on Scores of Complex and Routine Bridges
Bridge Geometry

In the late 1980s we were selected to lead a team of experts in the development of the AASHTO LRFD Bridge Design Specifications (LRFD)...On the heels of that assignment we were awarded a contract to develop Recommended Specifications for the Design, Fabrication, and Erection of Movable Highway Bridges whose end product would become the AASHTO LRFD Movable Highway Bridge Design Specifications.