What Is Stainless Steel.docx

1. What is stainless steel 2. Why use stainless steel 3. Types of stainless steel 4. Material specification/ selection for the bridges for Indian Railways 5. Properties and working stresses 6. Effect of cold working 7. Bi Metallic contact 8. Surface finishes 9. Relevant British standards 10. Global references 11. Breakthrough in India 12. JSL Products 13. Availability of material 14. Distribution 15. Services JSL offer for Architects/Designers/Fabricators

STAINLESS STEEL USES IN BRIDGES Posted on March 11, 2018

Stainless steel is a revolutionary material that has produced countless advances in all manner of industries. But perhaps no arena has been more transformed by the many benefits of stainless steel than architecture and engineering. Because of its tremendous strength, corrosion resistance properties, and aesthetic appeal, stainless steel can be found in modern bridges around the world. Stainless steel is an ideal material for use in bridges. It is equally useful for both large and small bridges, thanks to its durability and cost effectiveness. All kinds of bridges in the United States feature stainless steel of some kind, such

as large span bridges, railroad bridges, highway bridges, and pedestrian bridges. Especially considering the current decline in much of America’s highway infrastructure, including many bridges that are in a critical state of decay, the potential to extend the lifetime of these structures by using stainless steel is very appealing.

THE HISTORY OF STAINLESS STEEL IN ENGINEERING AND ARCHITECTURE The earliest bridges were made of wood. Ancient engineers then began using stone and concrete. Iron was not used as the primary bridge support until 1741 in England. Steel eventually became common in bridges in the late 1800’s. But regular steel can be susceptible to corrosion, especially in extreme environments, such as when exposed to saltwater. So it wasn’t until the use of stainless steel became common that bridges were able to enjoy all of the benefits that this material has to offer. Just after the turn of the century, in the early 1900s, several scientists working separately made advances that paved the way for stainless steel. Finally, in 1912, Harry Brearly was looking for a corrosion-resistant solution for gun barrels and was able to industrialize a martensitic stainless steel alloy. Brearly later teamed with Elwood Haynes to form the American Stainless Steel Corporation. It didn’t take long for stainless steel’s potential to be recognized by engineers. In 1925, stainless steel figured prominently in the refurbishing of St. Paul’s Cathedral in London. Here in the United States, the iconic spire of the Chrysler Building was made with stainless steel in 1928. While bridges have relied on general carbon steel for close to 150 years, stainless steel, because of its relative expensiveness, was generally used only for support materials. In particular, it was valued for its anti-corrosion properties and used in safety features such as guardrails and handrails. As more alloys were developed and the costs came down, it began to be used in more structural components, such as beams, welded plate sections, tierods, suspension systems, cables, and pylons. It is only in this century that stainless steel has become a primary bridge material.

THE CURRENT TREND OF STAINLESS STEEL IN BRIDGES The Cala Galdana Bridge is the first duplex stainless steel arch bridge for motor vehicles. It was built over Algendar Creek on the island of Menorca, Spain in 2003. It was constructed to replace the previous reinforced concrete bridge, which had become corroded due to the marine environment. The bridge’s total length is 55 meters (180 feet), with a main span of 45 meters. The grade of stainless steel was 1.4462 and was selected because it has a high resistance to corrosion by chlorides. In the last 20 years, more and more stainless steel bridges are being built, both for pedestrians and vehicles. With the most recent advancements, the cost of such bridges has gone down, and combined with their greater durability, the investment now makes sense. Stainless steel is also prized for its aesthetic appeal, an important consideration in modern architecture. Various grades of duplex stainless steel are especially popular. For example, in 2011 San Diego built the Harbor Drive Pedestrian Bridge. Again, the marine environment was a critical factor in material selection, and duplex stainless steel 2205 was the main metal used. This was the second pedestrian bridge in the U.S. made of stainless steel. The finish of this bridge was important because pedestrians would be using the bridge. They also wanted at least a 100-year service life. Duplex stainless steel is the most recent family of stainless steel alloys. Another name for this class of steel is austenitic-ferritic because its metallurgical structure consists of austenite and ferrite stainless steels in roughly equal

proportions. When duplex stainless steel is melted, the metal reverts to a completely ferritic structure. As the metal is then cooled, roughly half of the ferritic grains become transformed into austenitic grains. Duplex stainless steels are becoming increasingly popular in bridges and other engineering applications because of their superior properties. This includes the fact that these steels are typically twice as strong as austenitic or ferritic alloys. Because of their increased strength, less material is needed, saving both money and weight. These alloys show greater toughness and ductility than comparable ferritic grades as well, though they lag behind some of the best austenitic grades in this regard. As for corrosion resistance, duplex stainless steels have proven to have a performance comparable to 304 or 316 stainless steels, and with particular grades, they have the corrosion resistance required of marine environments, an important consideration for coastal bridges. Another factor in bridge design is a material’s stress corrosion cracking (SCC) resistance. In this regard, duplex stainless steels have the preferred properties of ferritic alloys, and do not suffer the same vulnerabilities that can be found in 304 and 316 alloys, which can suffer corrosion cracking in conditions such as high humidity and heat. Because duplex stainless steels have lower nickel and molybdenum content, they tend to be cheaper than comparable austenitic steels. This, combined with the weight savings mentioned previously, means that duplex stainless steels are extremely competitive on price.

SUMMARY Clinton Aluminum and Steel, with our deep experience working with engineers in all kinds of fields, understands what our customers most need when it comes to a materials provider. We take pride in on our ability to provide the exact product at the exact specifications, quickly and without any hassle. Moreover, we’ll work with you at every step of your production process to make sure that you have all the information you need to make an informed decision. Our staff of experienced technical professionals has an average of nearly 13 years working for Clinton. It’s due to their practical expertise that Clinton is recognized as the Midwest’s leading supplier of aluminum and stainless steel products. Contact us today to learn more about how we can help you get the maximum value out of your purchasing decisions.

Strong, Flexible & Beautiful: The Benefits of Steel Bridge Construction Jun. 9, 2017 Bridge Masters Bridge Design, Bridges and Utilities

According to the National Association of Corrosion Engineers, there are more than 600,000 bridges in the United States. Approximately one-third of them were built using a significant amount of steel, including pipelines and other utility infrastructure components. Steel is one of the most common elements used here in the U.S. and all over the globe to build many types and sizes of bridges, including:    

Long-span bridges Highway bridges Railroad bridges Footbridges

Some of the characteristics of steel that make it an attractive option for bridge builders include its versatility, cost effectiveness, longevity, and sustainability. These qualities allow designers to develop structures that would be impossible to build without steel components. Many of the great landmark bridges are constructed of steel. Still, it’s important to note that steel bridges aren’t just attractive, they’re generally stronger, safer, faster to build, require less maintenance, and are more flexible, which makes them perfect for earthquake-prone and highwind sites. Steel is also used to protect elements on bridges, including utility infrastructure. In addition to all this, environmentalists are more likely to support the construction of steel bridges compared to other types because they’re generally more sustainable and earth-friendly.

The key benefits steel offers bridge developers Economic benefits

Environmental benefits

Lower construction costs compared with The ability to recycle and reuse steel other materials helps save money for bridge components reduces municipal governments. environmental impact. Faster construction reduces traffic and business disruption.

Steel bridges are generally safer to build and less likely to fail.

Steel structures can be visually lighter and more attractive than other bridge Steel produced in controlled manufacturing environments limits waste. types.

Steel bridges last longer than other types, Steel is highly adaptable to different which means they don’t have to be climates and geographic conditions. replaced as quickly. Steel components require less maintenance and don’t need to be replaced as often.

Benefits to society

The relative lightness of steel compared with other materials reduces energy use during delivery and construction.

Steel allows longer spans to be built, The lighter weight of steel means smaller, which limits impact on habitats below. less costly equipment — including lifts — can be used on construction sites.

In certain conditions, a bridge made of steel is the only option to connect two areas. Steel components are less likely to be damaged during extreme events like hurricanes and earthquakes. Steel components are used to transmit critical utility services across bridges.

Let’s look at a few of the benefits of steel in greater detail. Lightweight construction

Steel has a remarkably high strength-to-weight ratio. This minimizes the weight of bridge superstructures, which reduces the cost of building the substructures that support them. This is particularly beneficial when constructing bridges in places where the ground is unstable, such as river beds and canyons. Compared to heavier materials, the lower weight of steel lowers the cost of transporting and handling it.

Sustainability

Steel is the most recycled material on the planet. In fact, almost 99 percent of steel from structures that are retired and demolished is returned to the steel-making process or reused as is. This goes a long way toward minimizing negative environmental impact. More good news: Recycled and reused steel performs at the same level as newly manufactured steel. Steel bridges are also more likely to be repurposed, since it is relatively easy to relocate them. Attractive design

Despite its strength — and in some cases, because of it — steel can be bent and twisted to create virtually any type of bridge. Think about it: steel bridges can look light and airy or solid and stable. They can be formed into any shape, from a simple straight line to a complex curve. The surface of steel may be detailed in countless ways and painted a full range of colors. Steel utility infrastructure can be tucked under a bridge and hidden so it does not affect the design. Faster constructions

Steel is a key contributor to Accelerated Bridge Construction (ABC) techniques. Components are built offsite and shipped to the building location and pieced together. In some cases, complete bridges are built offsite and then moved into place. These techniques reduce bridge construction time from months or years to days or weeks. This has a positive impact on the cost of projects, the environment, traffic and business disruption, and on-the-job accidents.

The most popular types of steel bridges

Steel can carry loads in tension, compression, and shear. That makes it the perfect material to use in many types of bridges. Beam bridges

On this type of structure, steel I-beams hold up reinforced concrete deck slabs. The two types of beam bridges are multi-girders, which have multiple steel beams supporting the decking, and ladder decks, which have two, along with additional bracing between the supports. Cost, site conditions, and length must be considered when deciding which beam bridge type to develop. The benefits of steel: Beam bridges use steel for its strength, not its architectural qualities. They’re built for function and efficiency. Box girder bridges

Box girders are made of two steel webs joined together at the top and bottom by flanges. This creates a closed cell that provides good torsional stiffness, a quality required on curved bridges. In beam and slab bridges, box girders, which weigh less, are used instead of plate girders, which are heavier, at the upper end of the span. Engineers must evaluate whether it is worth the higher cost of fabrication to use them for this purpose.

Composite box girder decks can take the form of multiple closed steel boxes, with the deck slab sitting above them, or an open trapezoidal box, closed off by the deck slab. Longer bridge spans usually leverage either a single box or two of them connected by cross beams. If a bridge is particularly long and minimizing weight is important, an all-steel orthotropic deck is used instead of a reinforced concrete slab. Now, here’s where things get complicated. For particularly long spans, box girders are likely to be a part of a cable-stayed or suspension bridge. In these hybrid structures, the box girders are custom shaped to improve aerodynamic performance. The benefits of steel: Steel girder construction helps engineers solve complex bridge design problems. Truss bridges

Most people are familiar with truss work. It’s the triangulated framework often seen holding up roofs on homes and supporting simpler bridges. Trusses are efficient structural elements because they can act in tension and compression. In addition to being a bridge type, trusses are frequently used in other types of bridges. They are often a component within arches or act as cantilevers and stiffen girders in suspension bridges. The benefits of steel: Trusses are less popular than they used to be because they are costly to fabricate. Still, for many bridges, they are the only alternative available to get the job done. Arch bridges

In these bridges, steel serves the same function as stone or masonry in older structures. It springs upward from — and exerts horizontal thrust on — the foundation. Steel arches act primarily in compression. The deck may be supported on struts, sit directly on the arch, or be suspended from the arch. Another variation of this type of bridge is the tied-arch or bow string arch bridge. The deck is hung from the arch above it and acts as a tension tie. It is well suited for bridges that span waterways, where the ground under them is soft. The benefits of steel: Arch bridges have become more popular in recent decades because they are relatively cost effective, flexible, and architecturally attractive. Using steel on arch bridges gives designers opportunities to expand their creative thinking.

Cable-stayed bridges

Without steel, cable-stayed bridges, today’s most innovative structures, wouldn’t be possible. The main girders of these bridges are supported at defined intervals along the length by tension wires connected to a steel mast or pylon. Because of the strength of steel, there can be two rows of supports, one on either side of the bridge or a single one down the center. The second option makes bridges seem extraordinarily light and ethereal. The towers, which may take the form of A-frames, H-frames, or columns, act in compression. The deck girders sustain compression and bending forces. The benefits of steel: Advances in engineering have made it possible for longer cable-stayed bridges to be built. They are now used in places where suspension bridges would have been constructed in the past. Suspension bridges

These bridges may look complex, but they function in a relatively simple way. Two steel cables are hung between two supports, forming a shallow curve. Additional cables are hung from the supports and connected to the ground. The deck is suspended from these cables by hanging cables. All the steel cables absorb the forces of tension. The deck acts to stiffen the structure and spread the load across it. When designed correctly, the deck prevents the bridge from bending and twisting. If the deck is not engineered properly, the results can be catastrophic. An example of a suspension bridge designed incorrectly is the Tacoma Narrows bridge, which collapsed because of vibration and twisting that occurred during a windstorm. The benefits of steel: The relatively low cost of steel cable and the engineering possibilities it offers makes suspension bridges an ideal option to span long distances, such as canyons, bays, and valleys.

Using steel on bridges

Structural steel is available in different grades. It is formed into an array of products with a wide range of sizes and shapes. The steel used to build bridges is prefabricated in controlled factory conditions. This ensures that the steel is consistent, of high quality, and dependably priced. Some of the processes used to create steelwork for bridges include molding, cutting, drilling, assembling, and welding. Most steel receives a protective coating or treatment that helps it stand up to weather and harsh environmental conditions. Steel is delivered to bridge construction sites as flat products, such as steel plates and strips, or long products, including beams, channels, and angled components. Steel is tested before it leaves the factory to ensure it meets specifications defined by the engineers who design bridges and regulatory agencies. These specifications are based on the forces of tension and compression that the components are required to withstand. The bridge designer considers several factors when selecting the grade of steel for a particular bridge component, including:     

Material qualities of the steel Design needs Cost Product availability Toughness

 

Weldability Corrosion resistance

The steel most commonly used on bridges can be grouped into the following categories:   

 

Carbon steel is the cheapest structural product available. It is used when stiffness is more important than strength. High-strength steel is made more durable by adding alloys during the manufacturing process. It’s usually more expensive than carbon steel and requires special welding techniques. Weathering steel (also known as corten steel) is a high-strength, low-alloy product manufactured specifically to withstand atmospheric conditions. The anti-corrosive properties of weathering steel extend bridge life to 100 years and beyond. Heat-treated carbon steels are the strongest available. The higher strength is the result of exposure to extreme heat. Stainless steel is used in places where corrosion resistance is critical, such as safety components, bearings, and guard rails. Usage is limited because of its high cost.

When steel components are delivered to a bridge construction site, they can be:     

Lifted into place by cranes and other types of equipment, which is usually the case with utility infrastructure and other support components. Slid into place. Rolled to their final positions. Transported by boat or vehicle. Lifted into place under a bridge.

Once in place, they are bolted and welded together to form the finished structure.

How to Combat Corrosion, One of the Top Threats to Bridges Sep. 28, 2018 Bridge Masters Bridge Work, Bridges and Utilities, Safety

It’s true: Corrosion is one of the biggest controllable factors that can affect the structural integrity of bridges. Corrosion is the gradual chemical erosion of metal. Experts find that more than 95 percent of structural damage on bridges can be traced back to some form of corrosion. It’s a particularly big factor on the four out of 10 bridges in the United States that are more than 50 years old, because most have not been treated to prevent it. Bridges in two parts of the United States are more likely to experience significant corrosive damage: 1. Northern states that frequently apply chloride-based snow and ice melting compounds to bridges. 2. Coastal areas, where bridges are impacted by salt water, high humidity, and extreme storms.

Bridges in dry locations, like deserts, are less likely to be damaged by corrosion.

Did you know: The two biggest factors affecting the lifespan of bridges are timeand how much chloride is used on them? Good design and maintenance can slow the effects of time on structures. Sound engineering coupled with leveraging-proven preventative measures can help avoid corrosive damage. Let’s take a look at the ways corrosion can affect bridges and what can be done to prevent it.

How corrosion weakens bridges Corrosion affects the structural integrity of bridges in a five critical ways: 1. Reduces the strength of individual structural elements

Corrosion lowers the effective cross section of critical structural components, which makes them perform in unexpected and unintended ways when stressed. It lowers the axial and flexural strength, which can lead to the partial or complete failure of individual elements, potentially weakening the overall structure. Be aware: Corroded metal elements may look stable, but that doesn’t mean they’re safe. Damaged bridge parts may no longer be able to handle the loads they were designed to support. Severe shaking or extreme twisting (caused by events like an earthquake, accident, or unexpected wind) can push stress beyond the reduced capacity level. It’s important to test corroded elements and replace them immediately if they are no longer able to perform as intended. Note: This type of degradation occurs in both steel and reinforced concrete structures.

2. Lowered shear capacity

As previously mentioned, corrosion can reduce the effective cross-sectional area of major bridge components, including beams and columns. This often reduces the shear capacity of individual sections and the ability to interact with sections connected to them. This leads to friction, vibration, and concussive action that the overall structure may not be able to sustain over time. 3. Increased fatigue

Corrosion can also impact the fatigue strength of steel components and connections. It is known to accelerate cracking and pitting, which is often concentrated in certain areas. This can cause metal elements to break and fail.

Tip: Corrosive damage isn’t limited to the visible parts of structures. It’s often more likely to occur in hidden, hard-to-reach places. If you see water pooling or flowing through an area, use modern lifts, drones, and photographic or x-ray technology to conduct in-depth inspections.

4. Decreased bond strength

The capacity of elements built from composite materials is dependent on how the concrete and rebar interact. Steel expands when it corrodes, which diminishes the bond with the concrete it reinforces and supports. This often weakens structural components, which can contribute to failure. It’s often difficult to identify this type of damage. Use modern x-ray equipment to inspect bridge sections exposed to water and corrosive substances. 5. Diminished ductility

Corrosion lowers the ability of metal sections of bridges to bend and twist. Maintaining this integrity is critical, especially in areas that experience earthquakes, shifting traffic loads, or extreme weather, especially winds. Some of history’s greatest bridge collapseswere caused by structural elements that could not flex as engineered when exposed to these conditions. It forces loads to shift in ways the structure cannot support.

How to prevent corrosion So, what can you do to reduce the effects of corrosion on bridges?

1. Inspect bridges regularly, looking for initial signs of corrosive damage. Taking action early can help prevent more costly repairs in the future. Safe and flexible lifts make it easier to access hard-to-reach sections of bridges that are often most vulnerable to corrosion. 2. Don’t limit inspections to primary structural elements. Also, check things like the utility infrastructure suspended under bridges. Hangers and seals are often affected by corrosive substances. If you find significant damage to utility infrastructure, consider replacing it using modern suspension systems. 3. Apply an epoxy coating to the rebar embedded in concrete beams and pillars. This may not completely stop the corrosion process, but it will slow it considerably. 4. Use less permeable concrete when building new structures and making repairs. It can help prevent water and chloride solutions reaching metal substructures. 5. Apply a sealer membrane between the deck and upper driving surface. It will prevent seepage and pooling of corrosive solutions on and around vulnerable metal parts. 6. Avoid using corrosive snow and ice melting solutions when conditions allow. Plant-based options are being tested and have been found effective in some cold weather locations. 7. Installing heating systems makes it possible to keep bridges ice and snow free without using destructive chemicals. These systems may require a large upfront investment, but they can pay off over time, especially in cold, snowy climates. (When doing a cost benefit analysis, don’t just consider the cost of a system versus the price of chemicals over time. Also take into account the workers

8.

9. 10.

11.

needed to apply melting solutions and clear snow, additional bridge maintenance and repair necessitated by using chemicals, equipment costs, and the financial impact of impassable roads on business and tax revenue.) Take advantage of bridge designs that eliminate or move the joint between the bridge and roadway off the main structure. Joints are the primary way chloride solutions seep into abutments. Placing them on the ends of bridges allows water and chloride solutions to drain away from vulnerable metal components. Repair cracks and potholes as soon as they happen. It helps prevent corrosive fluids from penetrating the road bed and damaging the substructure below. Put extra thought into designing (and retrofitting) drainage systems that push water away from vulnerable metal parts like abutments and girders. Many older bridges were built with systems that have end joints allowing water to spill directly onto girders. (Make sure drainage systems aren’t just bridge friendly but also good for the environment.) Regularly check metal elements protected by fire blankets. Older blankets sometimes hold in water and humidity, which can lead to damage and weakening over time. Modern fire blankets installed using today’s best practices can help prevent this.

Advance planning, smart design, and diligent maintenance are proven ways to protect bridge infrastructure from the devastating effects of corrosion.

When a Bridge is More than a Bridge Sep. 14, 2018 Bridge Masters History, Innovations

When is a bridge more than a bridge? A bridge becomes more than a structure that connects two places when it plays a central role in its community. In this article, we’ll take a look at four bridges that do more than link one place to another. These structures improve the lives of the people who reside, do business, and go to school nearby.

A bridge that’s a Main Street. Kew Gardens is a close-knit neighborhood in the New York City borough of Queens. At its center is a rickety bridge lined with a variety of popular shops, restaurants, and an Art Deco movie theater. It connects Lefferts Boulevard over several railroad tracks. Most in the neighborhood think of it as their Main Street.

A view of the shops on the Kew Gardens Bridge. The century-old bridge has been under threat for nearly three decades because the condition of the structure has deteriorated and become more dangerous over time. Things have gotten so bad that a hole opened up in the floor of one of the shops, which revealed the railroad tracks below. Despite its poor condition, residents have fought against razing the bridge. They’re concerned that demolishing and replacing it would change the village-like character of Kew Gardens. Past attempts at urban renewal have scarred the neighborhood with structures that are too big and modern to fit into its unique collection of smaller historic buildings. People feel that removing and replacing the bridge could be a step too far, cutting out the heart and soul of the community. Residents of Kew Gardens recently got some good news about the future of the bridge. A local council member was able to secure $1 million of government funding to conduct a study about whether to raze or repair it. Instead of using the money for that purpose, the Long Island Rail Road (LIRR), owner of the bridge, decided to put it toward shoring up the substructure, which could extend its life for another 30 years or more. LIRR had fought against repairing the bridge for decades, claiming it was a waste of limited budget dollars. However, vocal community support changed their position, and the organization decided to take steps to ensure the bridge would be able to continue to serve the community. However, this is only the first step toward securing the bridge. The support structure owned by LIRR isn’t the only section that needs rehabilitation work. The superstructure that the shops are built on, which is managed by an outside leaseholder, must be repaired as well.

The current lease expires in 2020. The holder has expressed interest in extending it and making the repairs. If that falls through, others would be allowed to bid on the lease, taking on the responsibility of completing the required rehabilitation work. Owners of businesses located on the bridge hope the issue will be resolved soon so they can start planning for the future. For now, it looks likely that the businesses — and the bridge that supports them — will remain at the heart of Kew Gardens for decades to come.

A painting project connects a community. The Campus District is a Cleveland neighborhood that’s split into north and south sections by highway I-90. The only thing connecting them and keeping them from becoming a “tale of two cities” is the East 22nd Bridge. On the north side of the highway is the campus of Cleveland State University. To the south is public housing that was developed beginning in the 1930s. The highway cut across the Campus District in the 1950s. Since then, the differences between the two sections have become more pronounced. Over time, the highway and bridge that connects them became symbols of racial and economic division in Cleveland. That is, until the city decided to turn the bridge into symbol of unity and connection through the innovative Bridge that Bridges program. During a five-month period this spring and summer, people who work, live, or attend school near the bridge participated in a series of discussions about the neighborhood divide and what could be done to remedy it. As a final step, those who took part in the talks were invited to paint a mural on the bridge that reflects the ideas generated by the community conversations. Over time, more and more people, including passers-by, joined in on the painting project. Many found that it was impossible to be angry or divisive while working together on the mural. Unity, justice, and togetherness are the goals of the Bridge that Bridges program. For now, it looks like the East 22nd Bridge mural is a potent symbol and reminder of the importance of living those values every day. Many people hope this program will be extended to other communities in Cleveland and beyond, making more bridges symbols of unity rather than division.

A bridge project in a highly sensitive location. The designers of the Verona Road overpass in Madison, Wisconsin, were challenged with developing a structure and related roadways that serve a wide range of needs for many different

types of people. It carries vehicular traffic, pedestrians, and bicyclists in a busy urban zone, part of which is home to many disadvantaged people who are dependent on public transit. On top of that, the surrounding area is environmentally sensitive. Because of the complexity, the design and development of the structure became an exercise in community building and compromise. Many factors triggered the redevelopment project:    

Wear and tear on the original structure. Inefficiencies caused by increased traffic. A poorly designed intersection that caused many accidents. Pedestrians and people in wheelchairs being forced to travel on roads because there were no sidewalks in some areas.

In order to solve these issues, the design team came up with a plan to transform the intersection under the bridge into a jug handle and roundabout, which reduces the potential for accidents while keeping the community connected in an environmentally friendly way. This overpass supporting Verona Road for almost 280 feet leveraged a unique design, featuring a pair of steel straddle bent bridges using a single pier column in the central island of the roundabout and pier columns on either side, well outside the bridge footprint. The outside piers straddle the roundabout. Local residents had a big say on whether this innovative design would actually get built. In order to see how it would look and experience how it could impact their everyday lives, the designers developed a complete three-dimensional model, including a video showing how traffic would flow through the area. Check out the 3D-animated drive-through video here. The design was approved because it was easy for people to see how it would speed traffic, increase safety, limit environmental impact, and improve their everyday lives. This innovative structure has brought together a diverse community with complex social and transportation needs.

A bridge that brought together a disconnected community A bridge doesn’t have to be large or located in a busy urban area to play a vital role in its community. In the rural, mountainous Punjab District of Afghanistan, a simple bridge was completed in 2011 that has significantly changed the lives of the approximately 2,500 people who live in the area, along with their herds of sheep and other animals.

The 40-foot-long, eight-foot-wide steel and concrete bridge connects the two sides of Kajabi, a village split in half by a river. Prior to its completion, the only connector between both parts of town — and the larger cities beyond — was a rickety wooden bridge held up by two metal poles. It was extremely dangerous for people, vehicles, and livestock to cross it, especially in the winter and during the spring flood season. Cars and cattle often fell into the river, and pedestrians were injured while crossing it. The old bridge left residents on both sides of Punjab almost completely isolated. The new bridge increased safety and makes it possible to cross the river all year long. It has helped lower the prices of goods sold in the area and those shipped from Punjab to be sold in other towns and cities. That’s because the new bridge can support larger trucks that charge lower freight fees. In addition, more direct shipping routes help speed products to market. Many who left Punjab seeking better economic prospects in bigger cities have returned. One other benefit provided by the bridge: improved education. In the past, students on one side of the village were unable to attend classes in winter and spring. Now they are able to go to school throughout the year. On top of that, parents feel more confident sending younger children over the new bridge, which has increased the number of people getting a formal education. In addition to building the bridge, more than 60 miles of area roads were improved by adding gravel topping. Funding for the project was secured by the Afghanistan Rural Access Project (ARAP), a part of the Ministry of Rural Rehabilitation and Development (MRRD). The goal of ARAP is to provide rural communities across Afghanistan with all-weather roads and bridges, a novelty in vast sections of this impoverished nation. This will allow the communities access to basic services that can help improve the lives and futures of their residents. ARAP has completed development of more than 450 miles of roads and 500 miles of bridges in Afghanistan. In addition, they’ve done maintenance work on almost 2,000 miles of roads. The poor condition of roads in many parts of Afghanistan make maintenance projects as important as new development. The new Kajabi bridge may be small, but it has had a massive impact on the lives of the people in its community and beyond.

They Saw It Coming: Lessons From the Italian Morandi Bridge Collapse Aug. 30, 2018 Bridge Masters History, Safety

The Morandi Bridge, a 50-year-old structure that was part of a highway system connecting the city of Genoa in Italy to France, collapsed on Aug. 14, 2018, during an intense rain storm. Dozens of vehicles fell onto a riverbed, railway, and two warehouses below the bridge, causing significant physical damage. More than 40 lives were lost.

Check it out: Security camera footage documents the collapse of the Morandi Bridge. While experts continue to investigate the reasons for the collapse, many people have theories about why the structure came down. Like many bridges across the globe, there were signs that the Morandi Bridge could fail. In this article, we’ll share some of the warning signs experts saw prior to the Morandi Bridge failure. This could help bridge managers identify issues with other structures and prevent future calamities.

Morandi Bridge: Background This important connector, completed nearly 50 years ago, was named for its designer, Riccardo Morandi. It was a cable-stayed bridge, which means sections of the roadway were cantilevered from towers and supported by stays. This design is generally considered a cost-effective option for mid-sized bridges.

The Morandi Bridge prior to collapse. Notice the significant amount of infrastructure beneath it.

Morandi Bridge by the numbers  

Built: 1963 to 1967 Opened: September 4, 1967

  

Length: 3,878 feet Height: 148 feet at road level, with three 300-foot towers Span: 690 feet

Cable-stayed bridges are more common today than a half century ago, when they were a relatively new concept. The Morandi bridge was somewhat unique because the stays used on it, which are critical for supporting the structure, were made of concrete reinforced with steel tendons. Adding steel enables the concrete to handle the bending and stretching that comes with supporting a roadway. This type of construction is no longer common. Newer bridges of this type use steel cables, which are more flexible, stronger, and more durable than reinforced concrete. There is another major structural difference between the Morandi Bridge and newer ones. It was built with only one pair of cable stays supporting each section of roadway. Those built today usually have many more. (For example, the Tappan Zee Bridge, a cable stay bridge nearing completion north of New York City, has 12 pairs of cable stays holding up each section, 24 in total, rather than just two.) Illustration shows how a cable stayed bridge works:

Sections of roadway are cantilevered from towers and supported by stays. This is important because the Morandi Bridge did not have the redundancy built into it that today’s structures do. While it has not been determined that the number of stays was a contributing factor to the collapse, a bridge with multiple stays per section is better able to survive should one fail or become stressed because of a shift in load, accident, or extreme weather event. By studying bridge failures, engineers have learned that adding structural redundancy can help prevent what’s known as “the domino effect.” This happens when damage to one bridge component causes others to fail, much like when one domino knocks down others positioned near it, turning into a chain reaction.

Possible reasons for the collapse While still under investigation, experts point to many issues that could have triggered the failure of the Morandi Bridge:

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Construction. Reports say work was being done on the bridge’s foundation at the time of the incident. Instability at the foundational level could have caused or contributed to the collapse. Design and construction errors. Since the bridge opened, experts have suggested the original design was flawed. Many believe the calculations used to determine how the concrete would age and perform over time were inaccurate. On top of this, lesser-quality materials may have been used because of budget limitations and cost overruns. This made the concrete prone to cracks, water damage, and corrosion. A similar Morandi-designed bridge in Venezuela has required a high level of ongoing maintenance to retain the structural integrity of the concrete. Weather. The event took place during an extreme summer storm. While many dismiss this as the ultimate reason for the collapse, wind, rain, and higher water flow could have exacerbated other issues. Increased traffic. The Morandi Bridge was built at a time when the area around it was less densely populated and traffic volume was far lower than the current 25 million vehicles per year. Many experts have expressed concern about whether the bridge could handle the extra wear and tear and the weight that comes from increased traffic volume. Weight. Traffic is not the only factor that adds weight to bridges. Decades of repairs, structural enhancements, and repaving can as well. There are reports that the bridge had undergone significant maintenance work over the last few years that could have stressed it beyond its limits.

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Age. Many bridges built during the 1960s are reaching the ends of their useful design lives. Longevity was not a consideration during the road and highway boom of the time. Some experts say the Morandi had another half-century of life in it, while others claim it faced many of the same issues as structures that are aging out. Privatization. The Morandi was owned and managed by a private entity, not a municipal government agency. While the owners completed required inspection and maintenance work, they may have not had adequate funds to upgrade the bridge to withstand current demand and meet today’s design standards. Infrastructure issues. Similar to the United States and many other countries across the globe, infrastructure spending in Italy has been inadequate for decades. This likely contributed to the structural decline of the Morandi Bridge over time. Accident. Although no accidents were reported at the time of the failure, it is possible that an impact on the roadway or to the foundation below could have triggered or contributed to the collapse.

What can be learned from the Morandi Bridge failure Consider the factors that could have contributed to the Morandi collapse to help prevent future bridge failures. Ask yourself: 

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Have you thought about how bridge maintenance and construction work could affect structural integrity? These activities can weaken bridges or add weight they weren’t designed to handle. Extra planning can help prevent unintended consequences. Have you upgraded bridges to eliminate design flaws and meet current design standards? Modern materials, design software, and modeling capabilities have contributed to making bridges lighter, stronger, and safer than ever before. Have you considered the impact of climate change and related extreme weather on bridges? Most older bridges weren’t built to handle stronger winds, major shifts in temperature, more powerful water flow caused by flooding, and wildfires. Consider using fire blankets to protect bridge infrastructure from fire and extreme heat damage. Is it time to upgrade bridges — or build additional ones — to handle higher traffic loads? Traffic in most areas increases incrementally year over year. After several decades, traffic levels could exceed the levels that structures were designed to handle. Have you checked that current load levels are sustainable? Decades of repairs and enhancements could stress certain sections of bridges beyond what they can handle. Consider replacing old structural additions with new ones made from lighter modern materials, like under bridge utility support systems. Is it time for a major bridge rehabilitation? Like many structures built after World War II, bridges from the period weren’t designed to last forever. It may be time to commit to a complete overhaul or replacement. If you can’t secure funds for a renovation or rebuild, inspect bridges regularly for cracks, damage, or unexpected structural changes. Modern lifts can help inspectors and engineers get to hard-to-reach areas of antiquated bridges. What entities should own and manage bridges? The answer is: It depends. If a municipality is cash-strapped, it might make sense to explore alternative private funding sources. If public safety and security is a top priority and private funding isn’t a possibility, ensure municipal agencies have the resources necessary to maintain structural integrity.

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Do you have the resources needed to keep bridges structurally sound? If the answer is “No,” it could be time to partner with government agencies, public advocacy groups, and private entities to find the budget dollars needed to keep people safe. Have you done everything possible to prevent accidents? Computerized signage, automated warning systems, and advanced communications technology are relatively lowcost investments that can help prevent accidents that can trigger bridge failures.

The Morandi Bridge collapse was a tragic event. The best thing that can come from it is using the signals that pointed to its failure to prevent future calamities.

CASE PEDESTRIAN BRIDGE AT TRUMPF HEADQUARTERS   

Footbridge over the heavily trafficked Gerlinger Strasse connects two work sites at the TRUMPF Headquarters Strong, thin, corrosion resistant Forta DX 2205 cut with TRUMPF laser technology Located in Ditzingen, Germany Choose stainless Case Pedestrian Bridge at TRUMPF Headquarters

Footbridge safely connects TRUMPF employees Courtney Tenzschlaich bergermann partner

A family-owned company that dates back to 1923, TRUMPF has become a world leader in industrial laser technology and the manufacture of machine tools used in flexible sheet metal processing. With over 12,000 employees in locations around the world, the company maintains its headquarters in a campus spread-out in Ditzingen, a green suburb of Stuttgart, Germany. As demand for their technological expertise and machine tools has grown, so have the facilities in Ditzingen. There, employees produce 3D laser printers, a variety of laser systems and components for machine tools in buildings that spread across several city blocks.

Connecting employees on campus Bisected by the heavily trafficked Gerlinger Strasse, the campus at TRUMPF has become a lot easier to move around beginning in July 2018, when a pedestrian bridge connecting the two main facilities has been put into service.

The 28 meter long bridge is designed by schlaich bergermann partner and manufactured by Franz Prebeck GmbH &Co KG. Due to the high efficiency of the supporting structure the lightweight shell structure could be made of only 20 mm thin, double curved Outokumpu Forta DX 2205 stainless steel sheets. Specializing in artistic steel constructions, schlaich bergermann partner ensures creative architectural designs, and maintain unique bridge characteristics and aesthetics.

One-of-a-kind cutouts Using Forta DX 2205 as the primary material in the bridge’s construction is ideal not only due to its cost-savings. In southern Germany, where wintery conditions and the use of salt on roadways to combat ice can lead to corrosion quickly, the durability and corrosion resistance found in Forta DX 2205 is a necessity. “We selected Outokumpu duplex for its corrosion-resistant properties, as the roadway below sees a lot of traffic and it needs to stand up to the road salts and icy conditions in winter,” said Florian Prebeck of Franz Prebeck GmbH & Co KG. In choosing duplex, the bridge design is likewise reduced to a minimum, providing it with a modern aesthetic. Thanks to a high standard of efficiency, engineers were able to employ double-curved stainless steel sheets as thin as 2 centimeters, stabilized by upstands which turn toward the footings and form triangular bearing points. With a lightweight shell structure, the one-of-a-kind pedestrian bridge also serves as a showcase for TRUMPF laser technology. The steel sheets provided by Outokumpu for use in the bridge were cut to shape using TRUMPF laser machines at Outokumpu’s service center in Aalten, The Netherlands; cutouts had to be delivered with a BrightLine cut quality. “We appreciated the smooth cooperation with Outokumpu that ensured the steel was delivered on time and cut to spec,” said Florian Prebeck. Because pedestrians will be walking directly on the stainless steel shell, the steel has already been treated to avoid slippage and includes small holes bored at a maximum of 1.5 cm apart. To respond to flux, engineers intend to laser openings into the sheets that are orientated according to how the structure will be used. After around six months construction period the bridge has been completed in June 2018.