Bowman Perspectives: The Evolution of Bridge Engineering – A Q&A with Gary Graham

Bowman Perspectives: The Evolution of Bridge Engineering - A Q&A with Gary Graham

Bowman's chief engineer of transportation discusses bridge construction, design and the challenges of aging infrastructure across the United States.

The evolution of bridge construction and design is not just a technical challenge but a crucial factor in ensuring the safety and longevity of our transportation infrastructure. As cities expand and face new challenges, the decisions we make today will shape the reliability and resilience of our bridges for decades to come. The recent Francis Scott Key Bridge collapse underscores the urgent need for innovation in this field.

Gary Graham highlights how modern technologies and evolving design practices are transforming bridge construction. Gary offers valuable insights into how these advancements are addressing current challenges and shaping the future of infrastructure resilience and safety.

Q: How can engineers design bridges that prevent similar tragedies like the one in Baltimore from happening?

A: When we design a bridge, we design it for the standards of the day. Baltimore's Francis Scott Key Bridge, designed in 1977, was a through-arch truss bridge built to the industry standards of that time. I doubt the engineers back then could have anticipated today's larger ships and the loads they transport traveling underneath it. Today, bridge design requires a deep understanding of site condition, loads and forces, which continue to evolve as commercial trucks and vehicles grow larger-requiring constant updates to design criteria.

To improve safety and longevity, engineers design bridges today with a greater importance on redundancy, ensuring that if one element fails, the remaining elements can still carry the load. Unlike truss bridges, which lack redundancy and are vulnerable to collapse if a key component fails, newer bridge designs offer better redundancy and can span further distances. Durability can also be enhanced by using materials and designs that withstand local environmental conditions, such as corrosion-resistant materials and high-performance coatings. Additionally, modern technology, such as advanced modeling and simulation tools, allow engineers to simulate stresses and identify potential failure points.

Most importantly, it's crucial to study past bridge failures, like the Key Bridge collapse, to understand what caused them and ensure any lessons learned are applied to new designs.

Q: How can recent technological advancements in bridge construction help prevent incidents like the Francis Scott Key Bridge collapse and other recent similar events?

A: Following the construction of the Francis Scott Key Bridge, numerous innovations have emerged. Most notably, cable-stayed bridges, which can span farther than traditional truss bridges. While we don't know what the new design of the Key Bridge will be, a cable-stayed bridge would be a good option. It would allow engineers to move the two main piers further out, creating a wider channel and keeping them out of the shipping lanes.

If a longer span isn't feasible, pier protection systems like dolphins or fenders can safeguard against ship impacts. Segmental construction techniques, where the bridge deck and substructure are built in sections and assembled on-site, have also become more common. This method enhances efficiency, quality control and cost-effectiveness.

Another advancement is the use of precast and prefabricated components, like abutments, wing walls and other bridge components. This not only improves quality but also speeds up construction with greater precision. Furthermore, stringent quality control and supervision during construction are more critical than ever, ensuring that all design specifications are met and that the bridge's strength and durability fully comply with project standards.

Q: How has bridge design evolved over time, and in what ways has this progress improved safety?

A: Advancements in materials, such as high-performance concrete and stronger steel alloy, have significantly improved the strength, durability and longevity of modern bridges. Accelerated bridge construction (ABC) has significantly improved safety by minimizing traffic disruptions during construction, protecting both the public and workers. Bridge owners have also adopted new project delivery methods, such as the design-build method.

Technological advancements have transformed the plan development process. Tools like computer-aided drafting (CAD) and building information modeling (BIM) enable detailed 3D models. These tools allow engineers to spot and resolve design conflicts early, ensuring more accurate and efficient projects.

Regular bridge inspection, now aided by drones and real-time monitoring systems, allows for a more thorough examination-ensuring continuous assessment of bridge health and detecting issues early to maintain safety and functionality.

About Gary Graham

Gary Graham is a chief engineer of transportation at Bowman. He brings nearly 40 years of transportation industry experience, specializing in bridge and highway design. His extensive career includes roles with the Pennsylvania Turnpike Commission and the Pennsylvania Department of Transportation, where he has led the design and delivery of numerous complex transportation projects. Graham's deep knowledge of state and federal transportation regulations, along with his expertise in navigating complex regulatory frameworks, has made him a leader in delivering successful infrastructure solutions.

*This Q&A draws from the August 2024 "Infrastructure Insider Interview" with Gary Graham, originally published by Roads & Bridges.