09 Aug DEBUNKED: Myths of Steel Bridges
Lightning only strikes in the same place once. Toilet flushes spin in a different direction in the Southern Hemisphere. A penny dropped from the empire state building can kill a person on the sidewalk.
These are common myths you may have once believed…or still believe. But, the reality is lightning can strike the same place more than once, toilets flush in both directions in both hemispheres, and a penny dropped from the empire state building might hurt — but it wouldn’t kill someone. Myths can shape your beliefs and impact the way you think, what you do, where you go, and what you buy.
Believe it or not, there are many myths surrounding the use of steel in bridge construction. Fortunately, the American Iron and Steel Institute (AISI), the American Institute of Steel Construction (AISC), and the National Steel Bridge Alliance (NSBA) dispelled common misconceptions about steel bridges in this publication.
The publication explains that the misconceptions about the use of steel in bridge construction often arise out of past experiences and do not take technology advancements, material enhancements, design updates and improvements in construction practices into consideration. Believing these myths can not only limit the competitiveness of steel solutions, but also lead to the misuse of steel products and prevent owners from taking advantage of steel in bridge construction.
Let’s debunk these myths!
Myth #1: Concrete bridges outlast steel bridges.
DEBUNKED: There is no credible evidence to support the myth that concrete bridges outlast steel bridges. Many factors, including design, type, frequency, traffic, environment, weather elements and maintenance, affect the life of a bridge beyond whether or not it is constructed with steel or concrete.
Life-cycle performance and the long-term durability of steel bridges have been clearly documented, but the long-term durability of concrete in bridges remains uncertain. After all, it is easier to inspect and determine the structural state of a steel bridge because all components are visible. Properly designed and detailed weathering steel bridges have achieved life cycles up to 120 years with minimal maintenance.
Myth #2: Weathering steel performs only under ideal climatic conditions.
DEBUNKED: In reality, weathering steel performs well when designed and detailed according to the published FHWA and industry guidelines for its use. The rate at which the protective patina forms may vary depending on the climate, but weathering steel is a viable choice for bridge construction in most locations of the country.
Weathering steel bridges should be detailed to ensure that all parts of the steelwork can dry out, by avoiding moisture and debris retention, and ensuring adequate ventilation. As the patina develops, run-off from the steelwork during the initial years, will contain corrosion products, which can stain substructures. This potential problem can be avoided by providing drip details on the bottom flanges of girders and ensuring bearing shelves have generous falls to internal substructure drainage systems.
Myth #3: Optimization by weight is the best approach to economical design.
DEBUNKED: This myth may be true in some cases, but when it comes to bridge construction, savings in material can be offset by increases in fabrication cost. In certain instances, adding weight may provide the least cost solution.
With weathering steel hollow structural sections (HSS), it takes less steel to do the same job. Because less steel is required to support a given load, you can save on material costs. Plus, because weathering steel does not require painting, you will save on the initial construction costs and additional life cycle cost savings due to the very limited ongoing maintenance costs.
The Benefits of Weathering Steel Bridges
While conventional steel bridges take advantage of the latest advances in automated fabrication and construction techniques to provide economic solutions, weathering steel bridges offer further benefits, including:
- Corrosion resistance: Due to its chemical makeup, weathering steel forms a protective rust patina that prevents corrosion in suitable environments.
- Aesthetic appeal: The unpainted appearance of weathering steel blends well in gardens, backyards, parks, and other outdoor environments where bridges are required.
- Eliminates the need for site painting: By eliminating the need for site painting, using weathering steel in bridge construction reduces the duration of construction.
- Minimal maintenance: Periodic inspection and cleaning should be the only maintenance required to ensure the weathering steel structure continues to perform well. This characteristic makes weathering steel ideal for bridges where access can be difficult and disruption needs to be minimized.
- Cost-effective: The minimal maintenance requirement along with the elimination of painting greatly reduces bridge construction cost. In fact, the cost of using weathering steel for bridge construction is about 5 percent lower than using conventional painted steel.
Ready to use weathering steel to construct a bridge?
Contact Central Steel for ASTM A847 Hollow Structural Sections
ASTM A847 hollow structural sections are commonly recommended for bridge construction. Central Steel stocks high-strength, corrosion-resistant steel pipe and tube in a variety of sizes. Contact us today to speak with an experienced sales representative about your project.