The Danyang–Kunshan Grand Bridge: A Testament to Engineering Ingenuity
Stretching across the picturesque landscapes of China, the Danyang–Kunshan Grand Bridge stands as a monumental testament to human ingenuity and innovation. In this article, we delve into the fascinating story behind the construction of this engineering marvel, its significance in the realm of infrastructure, and the awe-inspiring engineering feats that have made it the longest railway bridge in the world.
Content:
1. Engineering Marvel of Unprecedented Scale
Record-Breaking Length: Explore the staggering dimensions of the Danyang–Kunshan Grand Bridge, spanning an incredible distance of approximately 164.8 kilometers (102.4 miles).
Structural Design: Understand the intricate engineering and structural design principles that underpin the bridge’s construction, enabling it to traverse diverse terrain and withstand the rigors of high-speed railway operations.
2. Construction and Development
Vision and Planning: Uncover the ambitious vision behind the construction of the Danyang–Kunshan Grand Bridge and the meticulous planning process undertaken to bring this vision to fruition.
Construction Challenges: Learn about the challenges faced during the construction phase, from navigating complex geological conditions to overcoming logistical hurdles on a massive scale.
3. Significance and Impact
Enhanced Connectivity: Discover how the Danyang–Kunshan Grand Bridge has transformed transportation infrastructure in China, providing a vital link between major cities and regions.
Economic Growth: Explore the bridge’s role in driving economic growth and development along its route, fostering trade, tourism, and regional integration.
4. Technological Innovations
Advanced Engineering Solutions: Delve into the cutting-edge engineering technologies and methodologies employed in the construction of the Danyang–Kunshan Grand Bridge, showcasing China’s expertise in infrastructure development.
Sustainability Initiatives: Learn about the bridge’s sustainable design features and environmental conservation efforts, demonstrating a commitment to responsible infrastructure development.
5. Cultural and Symbolic Significance
Architectural Icon: Appreciate the architectural beauty and grandeur of the Danyang–Kunshan Grand Bridge, which has become an iconic symbol of modern engineering excellence.
Cultural Heritage: Understand the cultural significance of the bridge, serving as a testament to China’s rich history of innovation and technological advancement.
6. Future Prospects and Legacy
Continued Expansion: Explore plans for the future expansion and enhancement of the Danyang–Kunshan Grand Bridge, as China continues to invest in its transportation infrastructure network.
Legacy of Excellence: Reflect on the lasting legacy of the bridge as a beacon of engineering excellence and a source of national pride for China.
The Danyang–Kunshan Grand Bridge stands as a monumental achievement in the annals of engineering history, a testament to human creativity, innovation, and perseverance. As the longest railway bridge in the world, it serves not only as a vital transportation artery but also as a symbol of China’s unwavering commitment to infrastructure development and technological advancement. As we marvel at its grandeur and scale, let us also celebrate the collective human endeavor that has brought this engineering masterpiece to life, connecting communities, driving progress, and shaping the future of transportation infrastructure on a global scale.
How Artificial intelligence (AI) can optimize bridges design?
Introduction:
Bridges are important pieces of infrastructure that connect communities and facilitate transportation. Bridge design requires careful consideration of various factors, including structural integrity, safety, cost-effectiveness and environmental impact.
With the advent of artificial intelligence (AI), engineers and designers now have powerful tools to optimize bridge design.
In this article, we will examine how artificial intelligence can revolutionize the bridge design process and increase its efficiency .
1. Data analysis and prediction :
AI algorithms can analyze massive amounts of bridge design data, including geological studies, traffic patterns, and weather conditions. Conditions and historical performance data.By processing this information, AI can recognize patterns and make accurate predictions about how different bridge structures will perform under different conditions. This allows engineers to optimize bridge designs for maximum safety and durability.
2. Structural Optimization :
Artificial intelligence can help optimize the structural design of bridges by considering multiple parameters simultaneously. Using algorithms such as genetic algorithms or neural networks, artificial intelligence can explore a wide range of design possibilities and identify the most efficient and cost-effective solutions. This approach can result in bridges that use fewer materials, have a lower environmental impact, and can better withstand various stresses and strains.
3. Simulation and Testing:
AI can simulate and test bridge designs in virtual environments, allowing engineers to evaluate their performance before construction begins. Using AI-based simulations, engineers can analyze the behavior of different bridge structures in different scenarios, such as earthquakes, heavy traffic, or extreme weather conditions. This helps identify potential vulnerabilities and allows for changes early in the design process, saving time and resources.
4. Maintenance and Monitoring:
AI can play a key role in bridge maintenance and monitoring. By integrating sensors and IoT devices into bridge structures, AI algorithms can continuously monitor the health and performance of bridges in real-time.This allows early detection of structural problems such as cracks or corrosion and enables timely maintenance. AI can also analyze collected data to predict maintenance needs, optimize inspection schedules, and extend the life of bridges.
5. Cost Optimization:
AI can help optimize bridge design and construction costs. By analyzing historical data and considering various factors such as material costs, labor costs, and construction techniques, AI algorithms can suggest cost-effective design alternatives. This can result in significant savings without compromising the structural integrity and safety of the bridge.
6. Conclusion:
Integrating artificial intelligence into bridge design processes has the potential to revolutionize the way bridges are designed, built and maintained. By leveraging AI capabilities in data analysis, prediction, structural optimization, simulation, and cost optimization, engineers can build safer, longer-lasting, and more cost-effective bridges. As artificial intelligence continues to develop, we can expect new innovations in bridge design that will ultimately lead to the development of smarter, more sustainable infrastructure that benefits society.
Bridges are marvels of engineering that stand inconspicuously amongst us. We don’t think of them much even when we are passing over them. Nowhere are these structures more impressive then when the are built over water, which brings us to the question how are bridges built over water?
When the water is shallow, construction is easy. A temporary foundation is made on which piers are built to support the upper structure and the bridge is then built! It’s when the water is deep that other techniques are needed.
There are many methods to complete such as task in deep water but here we will explore the main three. These three methods of bridge building are called battered piles, cofferdams and caissons.
Battered Piles:
These are poles that are driven into the soil underneath the water. Piles are hammered into the water until the turn outward or inward at an angle. This makes the piles firm and increases their ability to carry lateral loads.
Piles are inserted in the ground using pile drivers. These are mechanical devices that may be transported to a location on a floating pile driving plant.
Battered Piles at a bridge project in Sweden
Pile drivers may also be cantilevered out over the water from piles that have been installed in advance. With the use of pile frames, pile hammers and winches, pile drivers hammer the piles into the soil until the turn outward or inward at an angle. The pile are now ready to carry lateral loads and can provide the foundation of support for the bridge.
The next step is to construct the pile caps above the piles. Once this is done, the bridge is ready to be built.
Cofferdams:
These are temporary enclosures made be driving sheet piling into the bed of a body of water to form a watertight fence. This is called the cofferdam. There is more to this bridge technique. Once the sheet piles have been inserted in the water to create a cofferdam, the water is pumped out of the enclosure.
Now, the construction workers can built the bridge as if the are working on dry land. The process then becomes relatively easy.
Cofferdam
Caissons:
There are two types of caissons, open and pneumatic.
An open caisson is a structure that is usually shaped like a box. It is open, at the top and bottom. The caisson is usually constructed on land then floated into position and sunk, so that the upper edge is above water level.
The caisson has a cutting bottom edge so that it sinks through soft silt on the bed. Inside is a series of large pipes or dredging wells. These are used to dredge up the bed material. As more material is dredged up, the caisson sinks and more sections are added to the shaft to keep it above water.
Once the caisson reaches the correct depth, concrete is laid to seal the bottom and then more concrete is poured into the caisson to form a solid post.
Steel Open Caisson
A pneumatic caisson is similar to an open caisson but it has an airtight bulkhead above the bottom edge. This is fitted with air locks. The space between the cutting edge and the bulkhead is called the working chamber. In this space, the water is removed using air pressure. Construction workers can then enter the chamber and excavate the soil.
It is important that the air pressure in the chamber be carefully monitored so the workers do not get the bends.
Pneumatic Caisson
But how do engineers pick which technique to use?
This all depends on the condition of the site and the technology available. These are important decisions to make that only exports can fully handle.
A truss is a special type of structure renowned for its high strength- to- weight and stiffness- to- weight ratios.
This structural form has been employed for centuries by designers in a myriad of applications ranging from bridges and race car frames to the International Space Station.Trusses are easy to recognize: lots of straight slender struts joined end- to- end to form a lattice of triangles, such as the bridge in Fig.1.
Fig.1 Truss bridge in Interlaken, Switzerland
In large structures, the joints are often created by riveting the strut ends to a gusset plate as shown in Fig.2.
A structure will behave like a truss only in those regions where the structure is fully triangulated; locations where the struts form other polygonal shapes (e.g., a rectangle) may be subject to a loss of stiffness and strength.
Fig.2 Joint formed by riveting a gusset plate to converging members
The special properties of a truss can be explained in terms of the loads being applied to the individual struts. Consider the three general types of end loadings shown in Fig.3 tension, compression, and bending.
If you were holding the ends of a long thin steel rod in your hands and wanted to break it or at least visibly deform it, bending would be the way to go. Thus, if we could eliminate bending of the struts as a potential failure mode, the overall strength and stiffness of the truss would be enhanced.
Fig.3 Different end loading possibilities. The dashed represents the deformed shape produced by the applied forces
This is precisely the effect of the truss geometry on the structure, as the stiff triangular lattice serves to keep any bending induced in the struts to a minimum.
Accelerated Bridge Construction – Best Practices and Techniques Free PDF
This textbook has been developed for the purpose of incorporating the latest developments in accelerated bridge construction (ABC) projects. Its objectives are to focus on creating awareness, educate, train, and inform bridge engineers in the art and science of effective rapid construction and delivery to the public.
It will entice the State Department of Transportations and its staff to select rapid construction techniques and save travel time of the public and money, especially during construction.
The applications of routine design procedures using AASHTO LRFD Specifications, State Design Manuals with specific reference to ABC, and the vast amount of bridge design software will not change except for new load combinations resulting from Lifting, transporting, erection, roll-in, slide-in, or float-in loads, etc.
Content :
Introduction to Modern Accelerated Bridge Construction
Recent Developments in ABC Concepts
Research and Training in ABC Structural Systems
Innovative ABC Techniques
Modular Bridge Construction Issues
Rapid Bridge Insertions Following Failures
ABC Planning and Resolving ABC Issues
Prefabrication of the Superstructure
Prefabrication of the Substructure and Construction Issues
Alternative ABC Methods and Funding Justification
A Review of Chapters, River Bridges, and Conclusions
A bridge is a structure providing passage over an obstacle. The obstacle may be a river, valley, road or railway. The passage may be for highway or railway traffic, pedestrian, canal or pipeline.
As the saying “Build bridges and you will have a friend” goes, bridges have a unique attribute of connecting different people. Rivers and mountains form physical barriers between people to interact, trade with one another, live and work together. For Ethiopia this holds especially true as the country is known as “The Water Tower of Africa” due to the high
rainfall we receive, which resulted in quite many big rivers dissecting the rough terrain and flowing deep in the valleys. Consequently we are composed of people speaking about 82 different languages.
Transportation network is crucial for the development and prosperity of a country. Investment by both nationals and foreigners is crucial for economic development of a country, and one of the criteria that foreign investors weigh in their investment decisions in a country is the level of development of the transportation network. Bridges provide essential
links in highways and railways at obstacles. The cost of bridges (and culverts) is a significant proportion of a highway project.
Many cities and towns are established near rivers and bridges add to the beauty of cities and towns. Bridges aid the social, cultural and economic improvements of the locations around them.
Bridges also have military strategic importance. The mobility of an army at war is often affected by the availability or otherwise of bridges to cross rivers. Military training puts special emphasis on learning how to build new bridges quickly while advancing and destroy bridges while retreating.
Bridge engineering is one of the fascinating fields in civil engineering calling for expertise in many areas: structural analysis and design, geotechniques, traffic projection, surveying, runoff calculation and methods of construction. A bridge engineer has to have an appreciation of economics and aesthetics besides ability in analysis and design.
One of the great beneficiaries of globalization is the transport sector, especiallymaritime transport. With cost between the Far East and Europe of about$2 for aDVD player and$30 for a television set, even the longest way pays off! This hasled to an explosionlike increase of container traffic (e.g., between 2004 and 2005 inShanghai by 24%, in Dubai by 17%, and in Hamburg by 17%) .
Consequently, the number and size of container ships has increased permanently (Fig.1).
Fig.1. Development of container ships.
In places with sufficient space for long-ramp bridges, normally high-level bridgesare built (Fig.2). In places with restricted space, road bridges may still be built ashigh-level bridges, but railway bridges as low-level movable bridges (Fig.3).
Because in many ports high-level bridges are unfeasible due to the very restricted space, movable bridges have experienced a veritable renaissance during the lastdecades.
Fig.2. High-level bridge for road and railway traffic: The Za ́rate-Brazo Largo Bridgesacross the Parana ́River, Argentina
Fig.3. A high-level bridge for long-distance road traffic and a low-level bridge for local roadand railway traffic: the Strelasund Crossing at Stralsund, Germany
Lift bridges
Lift bridges are suitable for great spans, but their clearance is limited by the lift towers, which have a great impact on the environment, even when the bridge is closed (Fig.4). The cables linking the bridge and the counterweights may suffer fromsignificant wear.
Fig.4. Kattwyk lift bridge at Hamburg, Germany
The lift bridge has a free span of 50 m and a clearance above the low-water level of13.5 m when in service, and 40 m when opened. The lifting height, therefore, is 26.5 m.It consists of the bridge deck, a steel bridge with orthotropic plate, and four roundedtowers made of reinforced concrete (r.c.), which hoist (and hide) the concrete coun-terweights and machinery. Due to the graceful design of these towers, the often uglyappearance of lift bridges is avoide.
Swing bridges
Swing bridges are also suitable for great spans and do not limit the clearance. The biggest bridge of this type crosses the Suez Canal at El Ferdan, Egypt, with a free spanof about 300 m (Fig.5).
Fig.5.Swing bridge across the Suez Canal at El Ferdan, Egypt
The disadvantages of swing bridges include the following:
When opened, they occupy the embankment over a length of about their main span.
Due to geometrical reasons, it is impossible to have separate bridges for railways and high-ways in close vicinity.
Bascule bridges
Bascule bridges may have a single flap or two flaps and are also adequate for longspans without limiting the clearance. The connection between the two flaps may trans-mit shear forces only, or shear forces and bending moments. For great heights above the water, the counterweight may be attached to the reararm as a pendulum (Fig.6), for reduced heights it has to be integrated with it.
Fig.6. Sample of a bascule bridge with hang-on counterweight: Bridge across the Bay of Cadiz, Spain
Balance beam bridges (draw bridges)
Drawbridges, the precursors of bascule bridges, are most probably the oldest type ofmovable bridge (Fig.7). Compared to bascule bridges, they have the advantageof rather simple piers and a high architectural potential (Fig.8), but the disadvantage that they permit only rather reduced spans.
Fig.7. Vincent vanGogh – Langlois Bridge at Arles, France.Courtesy of Rheinisches Bildarchiv Köln
An homage to the Chinese past, the new bridge makes history in its own right.
TSINGHUA UNIVERSITY
Behold, the world’s largest 3D-printed bridge. The Chinese creation spans 26.3 meters (a little over 86 feet) and has a width of 2.6 meters (almost 12 feet). Its design is a tribute to Chinese architectural history, referencing the historic Zhaozhou Bridge built in A.D. 605, the country’s oldest standing bridge.
While the ancient Zhaozhou span required a decade to build, Professor Xu Weiguo’s team at Tsinghua University needed only 450 hours of printing to finish all of their new bridge’s concrete components. That translates to a little under 19 days. In a press statement, Professor Xu’s team also says that the bridge’s cost came in at just two thirds the tally of ordinary bridge, with savings coming from cutting down on materials and engineering.
The bridge’s print structure in an earlier stage.
Construction in a later phase, printing a bridge board.
The bridge consists of 44 individual 3D-printed concrete units, each of them approximately 3 by 3 by 5 feet. The sides, influenced by the Zhaozhou, were made with 68 individual concrete slabs moved into place by robot arms.
A low angle shot of the bridge. Its design is based on China’s storied bridge history.
Embedded with a real-time monitoring system, the bridge will be able to detect vibrating wire stress and strain with high precision. The Tsinghua press release (read through Google Translate) notes that “the demand for labor in construction projects will be increasingly in short supply” in the future. If China cannot find people to build bridges, “intelligent construction will be an important channel to solve this problem.”
The press release concedes that “there are still many bottlenecks that need to be solved in the construction of 3D concrete printing,” including that while many companies are invested in building the technology, it has not often been used in “actual engineering.”
Professor Xu’s two robotic arms aim to combine these two fields, integrating digital architectural design, print path generation, and concrete material. The first robot has stirring and squeeze push functions, and the second robot is concerned with print path generation and maintaining an operating system.
Before the bridge was built, a 1:4 model was created to test its strength. When that went off without a hitch, the team felt confident enough to proceed in its next goal.
There have been other 3D-printed architectural projects over the last few years, as the technology has become more widespread. A team at MIT built a sample house in a stunning 14 hours. Not that they’re known for comfort, but the Marines recently 3D-printed a barracksin 40 hours. If there are ever houses on Mars, NASA suspects they, too, will be built by robots using 3D printing.
Over the last several thousand years, bridges have served one of the most important roles in the development of our earliest civilizations, spreading of knowledge, local and worldwide trade, and the rise of transportation.
Initially made out of most simple materials and designs, bridges soon evolved and enabled carrying of wide deckings and spanning of large distances over rivers, gorges, inaccessible terrain, strongly elevated surfaces and pre-built city infrastructures.
Starting with 13th century BC Greek Bronze Age, stone arched bridges quickly spread all around the world, eventually leading to the rise of the use of steel, iron and other materials in bridges that can span kilometers.
To be able to serve various roles, carry different types of weight, and span terrains of various sizes and complexities, bridges can strongly vary in their appearance, carrying capacity, type of structural elements, the presence of movable sections, construction materials and more.
Bridges by Structure
The core structure of the bridge determines how it distributes the internal forces of tension, compression, torsion, bending, and sheer . While all bridges need to handle all those forces at all times, various types of bridges will dedicate more of their capacity to better handle specific types of forces. The handling of those forces can be centralized in only a few notable structure members (such as with cable or cable-stayed bridge where forces are distributed in a distinct shape or placement) or be distributed via truss across the almost entire structure of the bridge.
Arch Bridges
Arch bridges – use arch as a main structural component (arch is always located below the bridge, never above it). With the help of mid-span piers, they can be made with one or more arches, depending on what kind of load and stress forces they must endure. The core component of the bridge is its abutments and pillars, which have to be built strong because they will carry the weight of the entire bridge structure and forces they convey.
Galena Creek Bridge, a cathedral arch bridge
Arch bridges can only be fixed, but they can support any decking fiction, including transport of pedestrians, light or heavy rail, vehicles and even be used as water-carrying aqueducts. The most popular materials for the construction of arch bridges are masonry stone, concrete, timber, wrought iron, cast iron and structural steel.
Examples of arch bridge are “Old Bridge” in Mostar, Bosnia, and Herzegovina, and The Hell Gate Bridge in New York. The oldest stone arch bridge ever is Greek Arkadiko Bridge which is over 3 thousand years old. The longest stone arch bridge is Solkan Bridge in Slovenia with an impressive span of 220 meters.
Beam Bridges
Beam bridges – employ the simplest of forms – one or several horizontal beams that can either simply span the area between abutments or relieve some of the pressure on structural piers. The core force that impacts beam bridges is the transformation of vertical force into shear and flexural load that is transferred to the support structures (abutments or mid-bridge piers).
Rio Grande in Las Cruces bridge
Because of their simplicity, they were the oldest bridges known to man. Initially built by simply dropping wooden logs over short rivers or ditches, this type of bridge started being used extensively with the arrival of metalworks, steel boxes, and pre-stressed construction concrete. Beam bridges today are separated into girder bridges, plate girder bridges, box girder bridges and simple beam bridges.
Individual decking of the segmented beam bridge can be of the same length, variable lengths, inclined or V-shaped. The most famous example of beam bridge is Lake Pontchartrain Causeway in southern Louisiana that is 23.83 miles (38.35 km) long.
Truss bridges – is a very popular bridge design that uses a diagonal mesh of most often triangle-shaped posts above the bridge to distribute forces across almost entire bridge structure. Individual elements of this structure (usually straight beams) can endure dynamic forces of tension and compression, but by distributing those loads across entire structure, entire bridge can handle much stronger forces and heavier loads than other types of bridges.
Common types of truss bridges
The two most common truss designs are the king posts (two diagonal posts supported by single vertical post in the center) and queen posts (two diagonal posts, two vertical posts and horizontal post that connect two vertical posts at the top). Many other types of the truss are in use – Allan, Bailey, Baltimore, Bollman, Bowstring, Brown, Howe, Lattice, Lenticular, Pennsylvania, Pratt, and others.
Admiral T.J. Lopez Bridge
Truss bridges were introduced very long ago, immediately becoming one of the most popular bridge types thanks to their incredible resilience and economic builds that require a very small amount of material for construction. The most common build materials used for truss bridge construction are timber, iron, steel, reinforced concrete and prestressed concrete. The truss bridges can be both fixed and moveable.
Cantilever Bridges
Cantilever bridges – are somewhat similar in appearance to arch bridges, but they support their load, not through a vertical bracing but trough diagonal bracing with horizontal beams that are being supported only on one end. The vast majority of cantilever bridges use one pair of continuous spans that are placed between two piers, with beams meeting on the center over the obstacle that bridge spans (river, uneven terrain, or others). Cantilever bridge can also use mid-bridge pears are their foundation from which they span in both directions toward other piers and abutments.
Howrah Bridge, Kolkata
The size and weight capacity of the cantilever bridge impact the number of segments it uses. Simple pedestrian crossings over very short distances can use simple cantilever beam, but larger distances can use either two beams coming out of both abutments or multiple center piers. Cantilever bridges cannot span very large distances. They can be bare or use truss formation both below and above the bridge, and most popular constriction material are structural steel, iron, and prestressed concrete.
Same of the most famous cantilever bridges in the world are Quebec Bridge in Canada, Forth Bridge in Scotland and Tokyo Gate bridge in Japan.
Tokyo Gate bridge in Japan
Tied Arch Bridges
Tied arch bridges – are similar in design to arch bridges, but they transfer the weight of the bridge and traffic load to the top chord that is connected to the bottom cords in bridge foundation. The bottom tying cord can be reinforced decking itself or a separate deck-independent structure that interfaces with tie-rods.
Generic tied-arch bridge with a movable support on the right side
They are often called bowstring arches or bowstring bridges and can be created in several variations, including shouldered tied-arch, multi-span discrete tied-arches, multi-span continuous tied-arches, single tied-arch per span and others. However, there is a precise differentiation between tied arch bridges and bowstring arch bridges – the latter use diagonally shaped members who create a structure that transfer forces similar to in truss bridges.
Tied arch bridges can be visually very stunning, but they bring with them costly maintenance and repair.
The Fort Pitt Bridge is a tied-arch bridge. The arches terminate atop slender raised piers and are tied by the road deck structure
Suspension Bridges
Suspension bridges – utilize spreading ropes or cables from the vertical suspenders to hold the weight of bridge deck and traffic. Able to suspend decking over large spans, this type of bridge is today very popular all around the world.
View of the Chain Bridge invented by James Finley Esq.” (1810) by William Strickland. Finley’s Chain Bridge at Falls of Schuylkill (1808) had two spans, 100 feet and 200 feet
Originally made even in ancient times with materials such as ropes or vines, with decking’s of wood planks or bamboo, the modern variants use a wide array of materials such as steel wire that is either braided into rope or forged or cast into chain links. Because only abutments and piers (one or more) are fixed to the ground, the majority of the bridge structure can be very flexible and can often dramatically respond to the forces of wind, earthquake or even vibration of on-foot or vehicle traffic.
Some of the most famous examples of suspension bridges are Golden Gate Bridge in San Francisco, Akashi Kaikyō Bridge in Japan, and Brooklyn Bridge in New York City.
Akashi Kaikyō Bridge in Japan
Cable-Stayed Bridges
Cable-stayed bridges – use deck cables that are directly connected to one or more vertical columns (called towers or pylons) that can be erected near abutments or in the middle of the span of the bridge structure. Cables are usually connected to columns in two ways – harp design (each cable is attached to the different point of the column, creating the harp-like “strings” and “fan” designs (all cables connect to one point at the top of the column). This is a very different type of cable-driven suspension than in suspension bridges, where decking is held with vertical suspenders that go up to main support cable.
Suspension bridge
Cable-stayed bridge, fan design
Originally constructed and popularized in the 16th century, today cable-stayed bridges are a popular design that is often used for spanning medium to long distances that are longer than those of cantilever bridges but shorter than the longest suspension bridges. The most common build materials are steel or concrete pylons, post-tensioned concrete box girders and steel rope. These bridges can support almost every type of decking (only not including heavy rail) and are used extensively all around the world in several construction variations.
The famous Brooklyn Bridge is a suspension bridge, but it also has elements of cable-stayed design.
Brooklyn Bridge
Fixed or Moveable Types
The vast majority of all bridges in the world are fixed in place, without any moving parts that forces them to remain in place until they are demolished or fall due to unforeseen stress or disrepair. However, some spaces are in need of multi-purpose bridges which can either have movable parts or can be completely moved from one location to another. Even though these bridges are rare, they serve an important function that makes them highly desirable.
Fixed Bridges
Fixed – Majority of bridges constructed all around the world and throughout our history are fixed, with no moveable parts to provide higher clearance for river/sea transport that is flowing below them. They are designed to stay where they are made to the time they are deemed unusable due to their age, disrepair or are demolished. Use of certain materials or certain construction techniques can instantly force bridge to be forever fixed. This is most obvious with bridges made out of construction masonry, suspension and cable-stayed bridges where a large section of decking surface is suspended in the air by the complicated network of cables and other material.
Small and elevated bridges like Bridge of Sighs, ancient stone aqueducts of Rome such as Pont du Gard, large medieval multi-arched Charles Bridge, and magnificent Golden Gate Bridge are all examples of bridges that are fixed.
Temporary Bridges
Temporary bridges – Temporary bridges are made from basic modular components that can be moved by medium or light machinery. They are usually used in military engineering or in circumstances when fixed bridges are repaired, and can be so modular that they can be extended to span larger distances or even reinforced to support heightened loads. The vast majority of temporary bridges are not intended to be used for prolonged periods of time on single locations, although in some cases they may become a permanent part of the road network due to various factors.
The simples and cheapest temporary bridges are crane-fitted decking made out of construction wood that can facilitate passenger passage across small spans (such as ditches). As the spans go longer and loads are heightened, prefabricated bridges made out of steel and iron have to be used. The most capable temporary bridges can span even distances of 100m using reinforced truss structure that can facilitate even heavy loads.
Moveable Bridges
Moveable bridges – Moveable bridges are a compromise between the strength, carrying capacity and durability of fixed bridges, and the flexibility and modularity of the temporary bridges. Their core functionality is providing safe passage of various types of loads (from passenger to heavy freight), but with the ability to move out of the way of the boats or other kinds of under-deck traffic which would otherwise not be capable of fitting under the main body of the bridge.
Movable Bridge in Chicago, USA
Most commonly, movable bridges are made with simple truss or tied arch design and are spanning rivers with little to medium clearance under their main decks. When the need arises, they can either lift their entire deck sharply in the air or sway the deck structure to the side, opening the waterway for unrestricted passage of ships. While the majority of the moveable bridges are small to medium size, large bridges also exist.
The most famous moveable bridge in the world is London Tower Bridge, whose clearance below the decking rises from 8.6m to 42.5m when opened.
Types by Use
When thinking about bridges, everyone’s first thought are structures that facilitate easy passenger and car traffic across bodies of water or unfriendly terrain. However, bridges can be versatile and can support many different types of use. Additionally, some bridges are designed in such way to support multiple types of use, combining, for example, multiple car traffic lanes and pedestrian or bicycle passageways (such as a present on the famous Brooklyn Bridge in New York City).
Pedestrian Bridges
Pedestrian bridges – The oldest bridges ever made were designed to facilitate passenger travel over small bodies of water or unfriendly terrain. Today, they are usually made in urban environments or in terrain where car transport is inaccessible (such as rough mountainous terrain, forests, swamps, etc.). Since on-the foot or bicycle passenger traffic does not strain the bridges with much weight, designs of those bridges can be made to be more extravagant, elegant, sleek and better integrated with the urban environment or created with cheaper or less durable materials. Many modern pedestrian-only bridges are made out of modern material, while some tourist pedestrian bridges feature more exoteric designs that even include transparent polymers in the decking, enabling users unrestricted view to the area below the bridge.
Charles Bridge as viewed from Petřínská rozhledna
While the majority of modern pedestrian bridges were made from the start to facilitate only on-foot access (such as Venice’s Ponte Vecchio and Rialto bridge), other bridges can be transformed from other purposes to pedestrian-only function (such as Prague’s historic Charles bridge).
Car Traffic
Car Traffic – This is the most common usage of the bridge, with two or more lanes designed to carry car and truck traffic of various intensities. Modern large bridges usually feature multiple lanes that facilitate travel in a single direction, and while the majority of bridges have a single decking dedicated to car traffic, some can even have an additional deck, enabling each deck to be focused on providing travel in a single direction.
Double-decked Bridges
Double-decked bridges – Multi-purpose bridges that provide an enhanced flow of traffic across bodies of water or rough terrain. Most often they have a large number of car lanes, and sometimes have dedicated area for train tracks. For example, in addition to multiple car lanes on the main decking, famous Brooklyn Bridge in NYC features an isolated bicycle path.
Train Bridges
Train bridges – Bridges made specifically to carry one or multiple lanes of train tracks, although in some cases train tracks can also be placed beside different deck type, or on different decking elevation. After car bridges, train bridges are the second-most-common type of bridges.
Cikurutug Bridge, Indonesia
First train bridges started being constructed during the early years of European Industrial Revolution as means of enabling faster shipment of freight between ore mines and ironworks factories. With the appearance of safe passenger locomotives and cars, the rapid expansion of railway networks all around Europe, US and Asia brought the need for building thousands of railway bridges of various sizes and spans.
Pipeline Bridges
Pipeline Bridges – Less common as a standalone bridge type, pipeline bridges are constructed to carry pipelines across water or inaccessible terrains. Pipelines can carry water, air, gas and communication cables. In modern times, pipeline networks are usually incorporated in the structure of existing or newly built bridges that also house regular decking that facilitates pedestrian, car or railway transport.
A pipeline bridge carrying the Trans-Alaska Pipeline
Pipeline bridges are usually very lightweight and can be supported only with the basic suspension bridge construction designs. In many cases, they are also equipped with walkways, but they are almost exclusively dedicated for maintenance purposes and are not intended for public use.
Aqueducts
Aqueducts – are ancient bridge-like structures that are part of the larger viaduct networks intended to carry water from water-rich areas to sometimes very distant dry cities. Because of the need to maintain a low but constant drop of elevation of the main water-carrying passageway, aqueducts are very precisely created structures that sometimes need to reach very high elevations and maintain rigid structure while spanning large distances. The largest aqueducts are made of stone and can have multiple tiers of arched bridges created one on top of each other.
The aqueduct at Querétaro city
The modern equivalent of the ancient aqueduct bridges are pipeline bridges, but while the viaduct network used natural force of gravity to push water toward the desired destination, modern pipeline networks use electric pumps to propel water and other material.
Commercial Bridges
Commercial bridges – These are bridges that host commercial buildings such as restaurants and shops. Most commonly used in medieval bridges created in urban environments where they took advantage of the constant flow of pedestrian traffic, today these kinds of bridges are rarely constructed with a notable amount of them being found in modern India. Slovakia’s city of Bratislava is a home of a car passageway bridge with a large tower that hosts a restaurant on top of it.
Medieval bridges are much more commonly known for their commercial applications. Italy is home to two of the best known commercial bridges in the world – the famous multi-tiered Ponte Vecchio in the city center of Florence, and brilliant white Rialto Bridge that spans the scenic Grand Canal in Venice. Both feature numerous shops that offer tourist memorabilia and jewelry.
Types by Materials
The core function of the bridge is to span a stable decking intended for the transport of pedestrians, cars or trains while enduring weight of its core structure, the weight of the traffic, and the natural forces that slowly but surely erode its durability. Various materials can help bridge designers to achieve their goal, and provide stable and long-lasting bridges that require varying levels of maintenance (and in cases of historic bridges, restorations). Here is the breakdown of all the common types of materials that are used in historical and modern bridge building:
Natural Materials
Bridges of natural materials – The first bridges ever made were constructed from unprocessed natural materials, starting from simple wooden logs that were placed across small rivers or ditches, to the large rope-tied bridges that are constructed over large canyons and mountain ranges in inhospitable areas of Asia.
Wood
Wood (Wooden bridges) – Wood is an excellent material that can be used for the creation of small to medium-sized bridges that are best suited for pedestrian or low-weight car transport. In modern times, wooden bridges are most commonly found for spanning short distances or being used to transport people, cars, and livestock over rough terrain or small rivers in Covered Bridges.
Stone
Stone (Stone bridges) – Stone is an excellent long-lasting natural material that can be used for the construction of bridges that can last for centuries. Stone pieces can even be used to construct very large bridge structures that don’t even use concrete – such as in Pont du Gard aqueduct in southern France that uses the weight of individual stones to make an entire 48.8 m high and 275 m structure stable for two thousand years.
Concrete and Steel
Concrete and Steel bridges – Durable, long-lasting and highly versatile modern materials that are today used for the creation of countless types of bridge designs. Coupled with the presence of cables and other modern materials, these types of bridges represent the majority of all the bridges that are currently in public pedestrian, car, and train transport use today.
Advanced Materials
Bridges of advanced materials – As decades go on, modern industry enables bridge builders to gain access to wide array of advanced materials that offer noticeable advantages over traditional construction processes.
You may not think about the bridges you cross on your way to work, but they’re far more than pretty structures that make your commute manageable. Bridges are crucial transportation links that carry road and rail traffic across rivers, gorges or other roads. When a bridge collapses or closes for repairs, it can cause massive traffic problems or strand people altogether, if they live on an island.
Some of the most massive and expensive engineering projects in history have involved building bridges. Although the general physics of bridge-building have been established for thousands of years, every bridge presents complicated factors that must be taken into consideration, such as the geology of the surrounding area, the amount of traffic, weatherand construction materials. Sometimes these factors are miscalculated, or something occurs that the bridge designers didn’t expect. The result can be tragic.
As we go through this list of 10 reasons why bridges collapse, keep in mind that most bridge collapses are the result of multiple factors. For example, a flood that damages bridge piers might not have caused a collapse — except for a design flaw and poor maintenance. Remove one of those factors and the bridge may have remained upright. On the other hand, sometimes a train smashes into a bridge and it just falls down. We’ll consider the possibilities, starting on the next page.
10. Earthquake
Earthquakes cause damage to all structures, including bridges. Major earthquakes can bring about the collapse of dozens of buildings, but collapsed bridges are often the most visible signs of the havoc an earthquake can wreak. Amidst the rubble and devastation, the sight of a damaged bridge from TV news helicopters stands out and becomes the iconic image of that particular disaster.
Such is the case with the Loma Prieta earthquake that struck the California coastal cities of Oakland and San Francisco in October 1989. The earthquake — named for a nearby mountain — caused 63 deaths, and the majority of them occurred in two bridge collapses: One person died as a section of the San Francisco-Oakland Bay Bridge gave way, and 42 others perished when a large portion of the Cypress Street Viaduct carrying Interstate 880 collapsed [source: USGS].
Fortunately, earthquake-triggered bridge collapses are relatively rare. In addition, builders can construct bridges in earthquake-prone areas to withstand tremors — or at least minimize the loss of life when one occurs.
9. Fire
Fire might be the rarest cause of bridge collapses, but fire has brought a few bridges down in the past. In fact, it used to happen much more often, when bridges were made out of wood. Train bridges were especially susceptible to fire, because the steel wheels of the train on the steel rails of the track frequently sent sparks shooting onto the bridge. If it was very dry or the wind fanned the sparks, the bridge could catch fire and burn completely down [source: Letchworth].
Bridge fires aren’t a thing of the distant past, however. Several modern bridges have also collapsed or been severely damaged due to fire. The cause is typically the crash of a tanker truck carrying a large amount of a highly flammable substance like gasoline. The crash triggers an explosion and a blaze so intense it melts the steel used to build the bridge. Eventually, the softened steel can no longer hold up the structure, and the bridge falls.
This is exactly what happened in 2009 when a tanker truck on I-75 near Detroit suddenly burst into flames directly under a bridge. The resulting inferno destroyed the bridge completely and forced the closing of I-75. Amazingly, no one was killed [source: Guthrie].
8.Train Crash
This type of bridge collapse is extraordinarily rare, but one of the worst rail disasters in history, the Eschede train disaster, was a bridge collapse caused by train impact. In 1998, a high-speed train traveling through Germany suffered a mechanical malfunction of one of the wheels. The broken wheel struck a switch and shifted it, throwing subsequent cars onto a different track. Moving at roughly 124 miles (200 kilometers) per hour, the cars derailed and slammed into the piers of a road bridge that passed over the railroad tracks at that point. The massive impact brought the bridge down directly onto the passenger cars of the train, crushing them. As a result, 101 people died in the accident [source: Oestern]. Eighty-three people lost their lives in a similar tragedy near Sydney, Australia in 1977 [source: ABC News].
A MOST UNUSUAL PLANE CRASH
Even rarer than trains crashing into bridges are airplane crashes that destroy bridges. The 1982 crash of Air Florida Flight 90 hit the 14th Street Bridge over Interstate 395 near Washington National Airport, killing several people in their cars. The bridge did not completely collapse, but did require extensive repairs [source: Wilber].
7. Boat Impact
Many bridges cross rivers and other bodies of water. Boats passing under a bridge are usually moving pretty slow (compared to trains), but boats have incredible mass. This means that even a barge, which typically creeps along at very slow speeds, can impart tremendous force if it collides with bridge pilings or piers. That force is sufficient to knock down the bridge in some cases.
An example of this type of incident is the collapse of the Judge William Seeber Bridge in New Orleans in 1993. The bridge carried road trafficover a canal, and a barge passing under the bridge struck a pier supporting the bridge and severed it. Nearly 150 feet (46 meters) of bridge collapsed as a result. One motorist driving on the bridge at the time died in the accident [source: NTSB]. More than a dozen major bridge collapses have been caused by boat collisions in the last 100 years [source: Wardhana].
6.Flood
Floods cause bridge collapses in a few different ways. Severe floods can cause rivers and creeks to overflow, picking up debris like trees, cars and parts of houses. When the river passes under a bridge, the high water level smashes the debris into the bridge. If the impact doesn’t destroy the bridge immediately, the weight of the piled up combined with the force of the flowing water pushing on it can bring the bridge down. This is what happened to the Conemaugh Viaduct in 1889, when the South Fork Dam in Pennsylvania collapsed, unleashing a massive torrent of water down the Little Conemaugh River [source: NPS].
Flooding can collapse bridges in a far more insidious way — by gradually wearing away the earth around and underneath the bridge piers. This process is known to bridge engineers as scour, and occurs whenever bridge foundations are placed underwater. The natural flow of the water can produce scour over many years, but bridges are built to withstand that type of erosion. Engineering techniques such as laying riprap, or layers of heavy rocks, can prevent scour. However, floods dramatically increase the force and volume of water affecting the bridge, and the damage to sediments can cause a bridge to collapse immediately or even days or months later. A study by the American Society of Civil Engineers determined that 53 percent of all bridge collapses are caused by flood and scour [source: Wardhana].
he Schoharie Creek Bridge is an example of a collapse caused by flood and scour. The bridge carried the New York State Thruway over the creek. In 1987, spring flooding caused high water levels. This washed sediment out from under one of the bridge piers, causing it to fall into a hole nearly 10 feet (3 meters) deep. Ten people died in the resulting bridge collapse [source: Storey & Delatte].
5. Construction Accidents
The Quebec Bridge collapsed twice during construction before finally being built.
A surprising number of bridges collapse as they’re being built. You might think these types of collapses aren’t as serious because no one was driving on the bridge at the time of the collapse. Unfortunately, some of the deadliest bridge collapses in history have occurred during the bridge’s construction. While a functional bridge may only have a few vehicles on it when it collapses, it takes hundreds of workers to build a bridge — all of whom may be in dangerous positions in case of collapse.
The 1907 collapse of the Quebec Bridge crossing the St. Lawrence River at Quebec City shows how engineering miscalculations can lead to disaster. The bridge was only partially constructed, but parts were already bending and breaking from the weight of the bridge itself. Engineers were concerned, but unable to take action swiftly enough. When it collapsed, 74 workers were killed [source: Structurae]. Amazingly, when the bridge was being rebuilt in 1916, it collapsed again, killing 13 more workers. It was finally completed in 1917 and remains in use today.
4. Manufacturing Defect
Some bridge collapses are mysteries when they first happen. It isn’t until a detailed investigation is completed that the true cause is revealed. Combing over the wreckage, engineers and accident investigators piece together the bridge’s history, looking at inspection reports and witness accounts of the collapse. At times, the simple failure of a small piece of the bridge caused the entire collapse. Sometimes low-grade or faulty materials were used, rendering the entire bridge too weak to withstand the rigors of time.
The 1967 collapse of the Silver Bridge over the Ohio River at Point Pleasant, W. Va. has become infamous for its connections to Mothman, a strange creature supposedly sighted near Point Pleasant in the months prior to the collapse (The 2002 Richard Gere film “The Mothman Prophecies,” chronicled the story). In truth, the collapse was due to a manufacturing defect in one of the steel eyebars that held the bridge up. Years of corrosion worsened the defect until it eventually failed, resulting in the deaths of 46 people [source: LeRose].
The 1994 collapse of the Seongsu Bridge in Korea was due to poor quality steel in some parts of the bridge and improper welding techniques in the bridge’s construction. 32 people were killed in the collapse [source: Korea National Emergency Management Agency]. The De la Concorde overpass in Laval, Quebec, Canada collapsed in 2006, killing five. The investigation revealed that some aspects of the bridge’s construction were done incorrectly and not according to the design, and that inferior quality concrete became too weak to support the structure.
3. Design Defect
Sometimes, bridges collapse due to design flaws
There are bridges whose collapse was inevitable before the bridge was ever built. The fault lies not with the construction of the bridge, but the design itself. The bridge is doomed to failure from the moment it was laid out on a blueprint.
One of the worst accidents in U.S. history is the collapse of the walkways in the Kansas City Hyatt Regency hotel. The walkways connected various parts of the second, third and fourth floors, overlooking the hotel lobby below — they were essentially pedestrian bridges inside the hotel. On July 17, 1981, the fourth-floor walkway collapsed, crashing onto the second-floor walkway which was directly below it. Both walkways then fell onto the lobby. Both the lobby and walkways were crowded with people watching or participating in an evening dance contest. The collapse killed 114 people [source: Associated Press].
Why did it happen? A redesign of the original plan caused the walkways to be constructed in such a way that structural elements ended up supporting the weight of both the second and fourth floor walkways simultaneously, doubling the load on them. Investigation revealed that even the original design was far too weak to support significant loads — and the redesign made the problem much worse [source: Martin]. It was nearly inevitable that they would collapse at the worst possible moment.
The 2007 collapse of the I-35 Bridge over the Mississippi River in Minneapolis, Minn. was also due to a design flaw. Steel gusset plates which bound key parts of the bridge structure together weren’t large enough. Additional weight placed on the bridge by concrete resurfacing and construction equipment caused the plates to buckle, and the entire bridge collapsed, killing 13 [source: NTSB].
2. Poor Maintenance
Poor maintenance is a difficult problem to diagnose in the wake of a bridge collapse. Many bridge collapses could have been prevented with more stringent inspection and maintenance routines, and lots of collapses that occur for other reasons are exacerbated by poor maintenance. When a bridge is designed, the engineers assume a certain level of maintenance that is necessary for the bridge to live out its intended lifespan. Rusted parts must be replaced, drainage areas cleared, new coats of paint applied and reinforcements added if traffic levels have increased.
A bridge carrying the Connecticut Turnpike over the Mianus River collapsed in the middle of the night in June 1983. The collapse was due to the failure of steel pins that had corroded. Investigators ruled that the bridge’s design and construction weren’t at fault — the collapse was blamed on deferred maintenance that would have spotted and replaced the rusted pins [source: NYCRoads].
1. Odd Occurrences
Some bridge collapses just can’t be explained at all.
We’ve discussed many causes of bridge collapse, but there are collapses that weren’t caused by any of the usual factors — rather, they were caused by events that can only be described as unusual.
In 1958, Cuba held the second Cuban Grand Prix. Legendary racer Juan Fangio was actually kidnapped by socialist revolutionaries before the race, but that wasn’t the worst thing about the event. The course was lined not with guard rails or safety fences, but with spectators standing right at the edge of the track. During the race, driver Armando Garcia Cifuentes lost control of his Ferrari and plowed into the crowd, destroying a temporary pedestrian bridge in the process. Seven people were killed [source: Edmondson].
The Lacey V. Murrow Memorial Bridge in Seattle crosses Lake Washington. It’s a floating bridge, suspended on pontoons. In 1990, a bizarre series of construction errors filled the pontoons with water used in resurfacing the bridge along with rain and lake water from a storm. Over the course of several hours, the bridge sank to the bottom of the lake.
The Winkley Bridge was a pedestrian suspension bridge in Arkansas. It was known for swaying significantly under load. In 1989, a group crossing the bridge started intentionally swinging it. They caused the bridge to sway so fiercely that the support structures failed and the bridge collapsed, killing five [source: Bridgehunter].
