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Hot Dip Galvanized Steel Vs. Weathering Steel What's The Right Choice

Steel has long played a key role in American construction efforts. Not only is steel lighter in weight than many other building materials on the market, but it also earns points for durability, affordability, and environmental friendliness. Still, bridge builders may struggle with whether to use more traditional weathering steel or increasingly popular hot-dip galvanized steel. Read on to discover how these options stack up.Hot Dip Galvanized Steel Vs. Weathering Steel What's The Right Choice

Benefits and Drawbacks of Weathering Steel

Long a favorite among bridge builders, weathering steel offers numerous advantages over other building types. Strong and attractive, this material rusts in a way that provides protection against the elements. Builders refer to this as “useful corrosion.”

Still, the news about weathering steel isn’t all positive. Progressively corroding, weathering steel can deteriorate faster if moisture is present. To compensate for this loss of mass and strength, builders may need to use thicker sections of steel from the start. Additionally, salt air and humidity can damage weathering steel, resulting in accelerated corrosion.

Benefits of Hot-Dipped Galvanized Steel

Formed by dipping bare steel in molten zinc, hot-dip galvanized steel is a popular choice in bridge construction. Featuring the strength of weathering steel, hot-dip galvanized steel offers additional benefits, too. Barrier and cathodic protection mean that this material resists corrosion. As a result, this option requires less long-term maintenance than weathering steel. Additionally, hot-dip galvanized steel maintains its structure despite exposure to UV rays, snow, water, and soil and is 100 percent recyclable.

Trust U.S. Bridge With All Your Building Needs

As a bridge building leader, U.S. Bridge brings more than 80 years of engineering and manufacturing expertise to the table. We’re passionate about constructing bridges that withstand time and the elements while making use of materials that are safe for the environment. Ready to learn more about our products and services? Call our steel bridge experts today or contact us online for info.

 

Those who aren’t familiar with bridge building might think of decks as parts of a ship or the area in the backyard where grills are kept. However, in the industry, we know “deck” is a term for the driving surface of a bridge. Whether constructed from concrete, wood, steel, or open grating, decks that form the driving surface of a bridge need to be strong enough for traffic to cross safely. At U.S. Bridge, we provide a full range of sustainable bridge floor and deck solutions to clients throughout the world. Read on to learn more about the types of decks we offer:

Concrete Deck Slab

When it comes to bridge floor and deck products, the concrete deck slab is one of the most popular. Typically between 7 and 9 inches thick, this deck has two layers of steel reinforcing bars to provide strength and durability.

Asphalt

For this deck type, corrugated steel planks, 3, 5 or 7 gauge, are attached to the stringers of the bridge and become a structural component of the structure.. By galvanizing these planks, the flooring is protected against corrosion. With an asphalt overlay, these types of decks provide a long-lasting, economical, driving surface.

Open Grid Steel Deck

If weight constraints are an issue, open grid steel decking is a wonderful option for a bridge floor. It is characterized by whether the grid is filled, or partially-filled with concrete. If concrete is included, a metal pan or form is included near the base or at mid-height of the grid to support the concrete while it cures.

Precast Concrete Panels

One of the most efficient deck types, precast concrete panels can be constructed quickly and easily. Designed and manufactured off site, these panels can be installed one day and driven over the next. Non-shrink grout is mixed and poured in batches on site.

Nail-Laminated Timber Bridge Floor

Ideal for more rustic locations around the country, these timber decks utilize pressure treated lumber to protect against the elements. Additionally, buyers can opt to cover the deck with asphalt if they choose.

Start Building Your Bridge Today

As a leader in bridge floor and bridge flooring solutions, U.S. Bridge engineers and manufactures steel bridges for a wide range of private and public organizations. You can trust us to create a safe, durable bridge that will stand the test of time. To learn more about what we do, call today or contact us for an online bridge consultation.

Analyzing the life cycle costs of steel vs. concrete bridges is of utmost importance to U.S. Bridge and the infrastructure industry in general. Aside from sustainability and social responsibility, U.S. Bridge is dedicated to using the best materials for the job. Depending on the scope of work and bridge design, the choice between steel or concrete could have a long-lasting impact on the sustainability of the structure.

U.S. Bridge asked Michael G. Barker Ph.D., a professor at the University of Wyoming, to draft a white paper regarding the Life Cycle Costs Analysis (LCCA) of bridges. Of particular interest was the use of hot-dip galvanized steel vs. concrete. The study determined that using HDG steel reduces capital costs by 8.5 percent. Below is the executive summary of the report that provides a good snapshot of the report and its findings. You can download the entire white paper here.

Executive Summary

Since the early 1990s, the Federal Highway Administration (FHWA) has promoted the consideration of Life Cycle Costs Analysis (LCCA) in the design and engineering of bridges. LCCA determines the “true cost” of bridge alternatives considering the time-value of money. The Life Cycle Cost analyses employed in this study uses the Perpetual Present Value Cost (PPVC) of bridge alternatives for an equivalent comparison between the alternatives.

Over the years, the author has worked with state departments of transportation and local county engineers on effective and economical bridge construction. A frequent question that arises during meetings is the difference in Life Cycle Costs between steel and concrete girder bridges. Both the concrete industry and the steel industry cite various anecdotal advantages above the other for the Life Cycle Costs over the life of the bridge. There has historically been a healthy competition between material types for new bridge construction. However, there is industry and owner confusion on how the different types of bridges compare on a Life Cycle Cost basis.

Steel vs. Concrete Bridge Analysis

This study developed useful owner information on historical Life Cycle Costs for typical steel and concrete state bridges in Pennsylvania. Typical bridges defined in the study are:

  • Concrete decks supported by steel rolled beams
  • Steel plate girders
  • Precast concrete boxes
  • Precast concrete beams

PennDOT historical records for bridges built between 1960 and 2010 were used to develop the Life Cycle Cost study database. Initial and maintenance costs considered include total project costs (more than just superstructure) as recorded in the PennDOT records. The PennDOT database used for the Life Cycle Cost analyses only includes a subset of the total bridge inventory. Missing cost and date data for a majority of the individual bridges made total inventory impossible. The database consists of 1,186 state bridges out of 6,587 (18 percent of the eligible inventory) built between 1960 and 2010.

The initial costs, Life Cycle Costs, and future costs of the 1,186 bridges in the database are examined with respect to:

  • Variability in bridge type
  • Bridge length
  • Number of spans
  • Bridge life

Protective coating systems were also used to examine steel bridges. The results must be taken into context since the results only represent the bridges that made it into the database. The database is not as comprehensive or desirable for drawing conclusions. The reader must decide how to interpret the tables and figures showing comparisons of initial costs, Perpetual Present Value Costs, maintenance and future costs, and bridge life.  

Report Conclusion Summary

A conclusion that can be drawn is that all the types of bridges are fairly competitive in both Initial Costs and Perpetual Present Value Costs. The average initial costs vary from $174 per square feet to $226 square feet. The average Perpetual Present Value Costs vary between $218 per square feet (Prestressed I Beam) and $278 per square feet (Prestressed Adjacent Box). The lowest average bridge life was 73 years (Prestressed I Beam) and the longest was 82 years (Steel I Beam). The coefficient of variation (standard deviation/mean) of the PPVC was approximately 20 percent, which is considerably high. With the relatively small differences in the PPVC averages, given the dispersion of the PPVC costs (standard deviation), any of the bridge types may have the least Perpetual Present Value Cost for a given project.

Chance for Further Study

This research was limited to a subset of PennDOT bridges. However, the analyses demonstrate the potential benefits of LCC analysis for bridge construction and management. A study of a more comprehensive database of bridges on the initial costs, Life Cycle Costs and future costs of different types of bridges over a diverse set of circumstances would be very useful for bridge owners and managers. A more comprehensive database would allow for a more accurate comparison of bridge types, design details, such as jointless decks, rebar coatings, steel protection systems, and other construction details.

For more information about this study, as well as the benefits of steel vs. concrete bridges, please contact U.S. Bridge today. You can also download the complete white paper here.

USB-Blog-How-it-Works-Engineering-Bridges-To-Handle-Stress

Bridges are often seen as immovable structures, but in truth, they are quite dynamic. Bridges must be engineered to move with environmental stressors in order to avoid unnecessary wear and tear. Additionally, different load types, weather conditions, and traffic can all cause bridges to adjust at various times. In a way, a bridge is an engineering marvel. So, how does it work? Below are some of the key components of bridge engineering and how they handle stress.

Oh, Gravity!

Gravity has the most profound impact on a bridge. Gravity is a constant – no matter what the other conditions, gravity is always acting on a structure, trying to pull it down. Bridges are at an even more unfair advantage against gravity since they span open spaces. For instance, a building, like a skyscraper, is also affected by gravity, but the ground the building is built on pushes back, creating an equilibrium of sorts. Bridges have no ground beneath them to act as a counterbalance to gravity. However, bridge failures are rare, thank goodness! So, how do designers go about engineering bridges to compensate for this gravitational pull?

Compression and tension are carefully balanced by channeling the bridge’s load onto the abutments (the supports on either end of the bridge) and the piers (the supports underneath the bridge).

Other Factors When Engineering Bridges

While gravity may be the most consistent force acting on a bridge, there are a handful of other elements that have a significant impact.

Loads – Bridge loads change often from vehicle to vehicle. Even a bridge specifically designed for one type of job, i.e. a train bridge, will find its load varying often. Different trains and their cargo weigh different amounts. Hence, it is imperative to engineer bridges that can adapt to these loads by flexing and bending and then returning to their normal state once the load passes.

Weather – Weather can wreck havoc on most structures, and bridges are no exception. Earthquakes and hurricanes can greatly impact structural integrity, while tides and wind can cause twisting and swaying. However, water is the most worrisome factor, because its different states generate different results. As snow or rain, water can make a bridge surface slippery; but, as ice, water can get into the crevices of a bridge and expand, causing more issues once the ice melts.

All these elements must be taken into consideration when designing and constructing a bridge. Only true experts understand what it takes to build a robust, durable, and functional bridge.

Find Out More Today

To find out more about how we go about engineering bridges to meet various workloads and demands, please contact U.S. Bridge today. Our team of engineering experts have been building bridges for decades. U.S. Bridge can bring that level of expertise to your next project too.

Optimal Design Of Through-Truss Steel Bridges

Truss bridges are one of the oldest bridge types in America. In fact, even novice bridge enthusiasts can easily spot one, since they are identified by their singular design feature: the truss, which forms triangular units. Truss bridges are used for a variety of reasons, mainly because they can easily accommodate dynamic loads. A through-truss bridge is one in which the roadway dissects the truss, meaning the truss is seen both above and below the deck. Here are a few interesting facts about the optimal design of through-truss steel bridges.

Factors that Impact Truss Steel Bridge Design

When studying through-truss steel bridges, engineers are primarily concerned with three things: optimum weight, optimum height and building material. A combination of these factors greatly impacts not only the cost of the bridge, but also its longevity and usefulness. Additional factors such as weather and use are also taken into consideration.

Determining the Optimal Through-Truss Design

In 2014, students at the civil engineering school at the University of Manchester in the UK studied through-truss bridge design with the goal of understanding the best combination of the above. They were most concerned with bridge stability, longevity, and cost-effectiveness. They determined that the element with the most impact on bridge design was the decking material. While minor adjustments can be made in the width and height, the weight of the decking material has the largest impact on the longevity of the bridge. They also realized that reinforced concrete decking is the most cost-effective; however, when reducing weight is the primarily concern, steel is the best option.

Through-Truss Bridges and U.S. Bridge

U.S. Bridge has been a leader in bridge building since 1936. Our expert staff of engineers, builders, and designers are well-versed in all bridge types, including through-truss steel bridges. Still family-owned and operated, U.S. Bridge is committed to providing customers with the latest in bridge design and construction. Our past clients include state and local governments, as well as businesses.

If you would like to find out more about U.S. Bridge, our work and our team of experts, please contact us today. We are happy to discuss your steel bridge needs and look forward to working with you.

Myths: Modular Prefabricated Short-Span Steel Bridges Are Only Temporary Structures

Modular, prefabricated steel bridges are often considered temporary structures. Using modular design and building bridges onsite has often been considered a more efficient building method, but a less stable one. However, after meeting all the permanence standards set by the AASHTO, the ASTM and the AWS, it was determined that pre-fab short span steel bridges can be considered permanent structures.

Standards for Permanence

Most often, the biggest concern facing modular bridges and permanence, relates to how they are constructed. Bridge parts must be assembled onsite, resulting in welding in possibly less than ideal conditions. For short span steel bridges, this concern is absolved because the welding is all done in a shop, under favorable conditions. This reduces the risk of introduced environmental factors during the welding process, and ensures the pre-fab bridge will withstand the rigors of time and weather.

Myth-Busting Short Span Steel Bridges

The Short Span Steel Bridge Alliance (SSSBA) reports the bridge industry is generally moving toward a modular bridge design. Due to the ease of assembly and the efficiency with which they can be built, pre-fab bridges make more sense. Timing is especially important regarding bridge construction since more than a quarter of all bridges across the United States have been deemed as “structurally deficient” or “functionally obsolete.” Also, using steel as the primary material for short span bridges brings a host of benefits including:

  • Consistent Quality
    Steel production is held to high standards and consistently meets quality requirements.
  • Sustainability
    Almost 93% of all steel is made from scrap steel.
  • American-made
    Structural steel is made in America, providing jobs to American workers and boosting the economy.
  • Quick fabrication and Installation
    Steel can be manufactured fairly quickly. This accelerates the construction timeline and decreases disruption to the surrounding areas.

To find out more about short-span steel bridges and how permanent they are, please contact us at U.S. Bridge today. Our expert team of engineers and builders are more than happy to discuss the benefits and strengths of modular bridge construction with you.