We are independent & ad-supported. We may earn a commission for purchases made through our links.

Advertiser Disclosure

Our website is an independent, advertising-supported platform. We provide our content free of charge to our readers, and to keep it that way, we rely on revenue generated through advertisements and affiliate partnerships. This means that when you click on certain links on our site and make a purchase, we may earn a commission. Learn more.

How We Make Money

We sustain our operations through affiliate commissions and advertising. If you click on an affiliate link and make a purchase, we may receive a commission from the merchant at no additional cost to you. We also display advertisements on our website, which help generate revenue to support our work and keep our content free for readers. Our editorial team operates independently from our advertising and affiliate partnerships to ensure that our content remains unbiased and focused on providing you with the best information and recommendations based on thorough research and honest evaluations. To remain transparent, we’ve provided a list of our current affiliate partners here.

What Is a Box Girder?

Dan Cavallari
By Dan Cavallari
Updated May 17, 2024
Our promise to you
AboutMechanics is dedicated to creating trustworthy, high-quality content that always prioritizes transparency, integrity, and inclusivity above all else. Our ensure that our content creation and review process includes rigorous fact-checking, evidence-based, and continual updates to ensure accuracy and reliability.

Our Promise to you

Founded in 2002, our company has been a trusted resource for readers seeking informative and engaging content. Our dedication to quality remains unwavering—and will never change. We follow a strict editorial policy, ensuring that our content is authored by highly qualified professionals and edited by subject matter experts. This guarantees that everything we publish is objective, accurate, and trustworthy.

Over the years, we've refined our approach to cover a wide range of topics, providing readers with reliable and practical advice to enhance their knowledge and skills. That's why millions of readers turn to us each year. Join us in celebrating the joy of learning, guided by standards you can trust.

Editorial Standards

At AboutMechanics, we are committed to creating content that you can trust. Our editorial process is designed to ensure that every piece of content we publish is accurate, reliable, and informative.

Our team of experienced writers and editors follows a strict set of guidelines to ensure the highest quality content. We conduct thorough research, fact-check all information, and rely on credible sources to back up our claims. Our content is reviewed by subject matter experts to ensure accuracy and clarity.

We believe in transparency and maintain editorial independence from our advertisers. Our team does not receive direct compensation from advertisers, allowing us to create unbiased content that prioritizes your interests.

A box girder is a type of structural beam used in construction that is very often made of steel, though in the past iron was commonly used for construction purposes. This type of beam uses one or more enclosed cells within the beam for structural integrity, as opposed to an I-beam or H-beam, both of which have open ends. Bridge construction will often necessitate the use of the box girder, as will other structures such as buildings. This type of girder can usually hold more weight than an I-beam, and it will be more resistant to torsional damage, or twisting.

Bridges are sometimes constructed with a box girder design on a much larger scale. Bridges that curve or bend especially benefit from this design because of the box girder's ability to resist torsion. Concrete can actually be poured into the appropriate shape, usually underneath the bridge's deck, to add torsional rigidity to the overall structure. The box girder design may feature only one cell, or box, while other designs may feature a multi-cell system that includes many boxes. The shape of the box is not always rectangular, either; each box can be tapered to accommodate a specific design for the structure. This is sometimes called a cellular girder design.

The disadvantages of a box girder can prevent it from regular use. These beams are generally more expensive to fabricate, and they can be more susceptible to rusting and corrosion because water can begin to pool within the cell of the beam. Several bridges using the box girder design have collapsed in the past, leading to a reevaluation of the design's usefulness and safety for bridge design. Many bridges are still built using this technique, however, with no great safety risk.

A significant advantage of box girders is the ability to support a significant amount of weight in the same length as compared to an I-beam. Structures can therefore be built taller, wider, or longer using box girders than with other designs. The multi-cell design can enhance the strength even further, making it possible to build long bridges over wide spans. The bridge and other structures will, however, often require more regular inspection and maintenance to ensure the girders are still strong, well conditioned, and able to handle the regular stresses of the structure. Such inspections and maintenance can become costly, and combined with the overall cost of fabricating the materials, the structure may become cost-prohibitive to build with such girders.

AboutMechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.

Discussion Comments

AboutMechanics, in your inbox

Our latest articles, guides, and more, delivered daily.

AboutMechanics, in your inbox

Our latest articles, guides, and more, delivered daily.