The goal of every bridge replacement project is to minimize traffic disruption. Although this can be achieved using temporary structures, it results in high construction costs. More recently, modular construction has been used to cut down the on-site construction time. However this method still significantly impacts traffic flow.
A new technique, known as Accelerated Bridge Construction (ABC), has been developed to mitigate traffic disruption. This process begins with the construction of the new bridge superstructure alongside the existing bridge. Once this is completed, the existing bridge is quickly demolished and the new bridge is slid into place. The final few pieces are installed, and the bridge can quickly reopen to traffic with minimal disruption. This procedure is outlined in detail by the Iowa Department of Transportation:
There are a number of projects throughout the United States that are using this new technique.
Michigan’s Department of Transportation (MDOT) is finalizing plans to replace three bridges this year using this process (M Live). MDOT spokesperson John Richard stated, “You’ll definitely see a lot more bridge slides taking place just because of the less impact on traffic. It’s really changing the industry. All the engineers at MDOT are very excited” (M Live).
New York’s Department of Transportation has already constructed a number of bridges using this process. The construction of the I-84 bridges, which began in June, was completed in October of last year. Despite the length of the project, the actual replacement time totaled 18 hours for each bridge, occurring over two weekends. This resulted in savings of $4 million dollars (Roads Bridges). You can view the time lapse construction video of the bridge here: Accelerated Bridge Replacement
It is evident that the use of ABC as a bridge replacement technique will increase in the coming years. However, it is important that researchers around the world continue to develop more efficient ways to replace the worlds ageing infrastructure. This includes reducing construction time, reducing costs, mitigating the effects on traffic and recycling materials from the demolished bridges.
For more information regarding ABC see the brochures recently published by Aspire Bridge:
The continuing battle for skyscraper supremacy has reached new heights with the completion of Shangai Tower in China. At 632m (2073 ft), it is the second tallest building in the world, just short of the 830m (2723 ft) tall Burj Khalifa (CBC News)
Designers in South Korea however have taken a different approach: instead of focusing on the height of the structure, why not showcase the technological capabilities of the nation. The result is the world’s first ‘invisible’ skyscraper.
Tower Infinity will be constructed in Seoul, South Korea to a height of 450m (1476 ft), making it one of the tallest buildings in the world and the sixth highest tower. The construction was recently approved by the government, but a date has not yet been set for this ambitious project (CNN). The design of the tower was completed by GDS architects, and will feature the third tallest observation deck in the world, a theatre, a roller coaster, various restaurants, and a water park (Inhabitat).
Located near the Incheon International Airport, Tower Infinity is set to become the new face of Seoul. According to GDS architects, “Instead of symbolizing prominence as another of the world’s ‘tallest and best’ towers, it sets itself apart by celebrating the global community rather than focusing on itself. The tower subtly demonstrates Korea’s rising position in the world by establishing its most powerful presence through diminishing its presence.” (GDS)
The structure itself will consist of a series of blending shapes ranging from diamonds to triangles (Good Times). However, what sets the proposed tower apart is the ‘smart’ facade which will render the building invisible to pedestrians at ground level.
How the Magic Works
Cameras will be installed at three different heights and on six different sides of the tower. These cameras will record the building’s surroundings in real-time. These recordings will then be streamed to the 500 rows of LED screens built into the facade of the tower, each edited to seamlessly connect with one another.
By projecting real-time images from the back of the building onto the front, it will create the illusion that the building is in fact, invisible. In addition, the level of transparency can be varied, depending on the desired effect (CNN).
However, this concept could be used for a number of different applications. For one, the TV screens could be used as billboards, creating the worlds tallest advertisement. In addition, the screens could be used to broadcast real-time world events. The possibilities seem endless.
Similar Projects Around the World
The concept of an invisible skyscraper may seem to be novel, but similar projects have been attempted around the world. In Sweden, the Mirrorcube hotel uses a mirrored facade to render itself invisible to all those walking through the forest setting.
The hotel room measures 4 meters in each direction. The room includes a large bed, bathroom, lounge, and rooftop terrace. The mirrored facade allows the structure to co-exist seamlessly with the surrounding environment: an effect that the Tower Infinity is looking to replicate. In addition, a special mesh that is only visible to birds has been installed to protect the wildlife in the area (Telegraph).
The Next Big Project
Countries all across the globe are currently vying for infrastructure supremacy. This has lead to investments of billions of dollars in developing higher, more technologically advanced structures. This trend will increase exponentially as the global economy emerges from the current recession. As a result, the next decade could produce truly spectacular structures.
There is no doubt that the attacks that occurred throughout the United States on September 11, 2001 (twelve years today) changed the course of history. The Twin Towers, located in New York City, collapsed two hours after the first plane hit the north tower. The death toll for these attacks totalled over 3000 (History Channel).
To pay tribute to the victims, plans were made to construct a memorial complex on the site of the old Trade Centers. This complex features five new skyscrappers, a 9/11 memorial and museum, a World Trade Center transportation hub, retail space, and a performing arts centre (World Trade Center). The extensive plans have involved some of the most famous architects, artists and urban developers of our time, including: Santiago Calatrava, David Cholds, Norman Foster, Frank Gehry, Daniel Libeskind, Fumihiko Maki and Richard Rogers (World Trade Center).
The memorial features two 16-acre reflecting pools which are set in the original footprints of the two towers. The largest man-made waterfalls in North America are located in the centre of these pools, and the names of the victims are written around the pool’s edges.
For Every Action, There is an Equal Larger and Opposite Reaction
In addition to the memorial, plans were made to build five new skyscrapers. One World Trade Center, sometimes incorrectly referred to as Freedom Tower (Wall Street Journal), will be the tallest building in the western hemisphere, and the fourth tallest building in the world upon completion. The roof top has a height of 1368 ft (417m), identical to the height of the original North Tower. However, the steel spire situated at the top of the building bring the total height to 1776 ft (541 m). This acts as a symbolic reference to the date that the United States signed the Declaration of Independence, separating the colony from the British Empire.
The structure is composed of a concrete core surrounded by a steel structure. As a result, the tower acts like a ‘building within a building’, attaining a level of safety which far surpasses the current requirements in building codes. Steve Plate, the director of World Trade Center construction for the Port Authority of New York and New Jersey, stated, “The core walls aren’t sheetrock like the original towers, they’re more than 6 feet of concrete in places. We’re rewriting the book on security for office towers.” In addition to this, the podium at the base of the building consist of a 187 ft tall by 200 ft wide concrete slab, increasing the towers safety. (Popular Mechanics).
Once completed, this building will play host to 69 office floors, two television broadcasting floors, two restaurants, an observation deck, and a glass-metal parapet (World Trade Center). The construction of the tower, which began in 2006, is expected to be completed in early 2014.
Green Reaches New Heights
One of the most important features of the new landmark is the achievement of a LEED Gold certification. This has been attained through the use of various green technologies. The 57th floor will play host to two 25,000 gallon (94,600 L) rainwater collection tanks, which will be used for the buildings operational needs. In addition, the toilets are shaped in a way to increase the velocity of the water flushing, reducing the amount of water per flush. According to Steven Plate, “It not just helps the environment. It also saves a lot of operational costs.” (MSNBC News)
Some other ‘green’ features include: the use of recycled debris and materials during construction, an increase in the use of natural light, and an LED backlight system for the podium which is both cost-effective and creates less heat energy,
However, the ‘green’ emphasis has lead to construction costs of almost $4 billion (US), making it the most expensive office tower ever built (Wall Street Journal). Despite this, the significantly lowered operating costs and energy usage make the project economical from a life cycle perspective. For more information about the LEED program, see my previous post entitled “LEED-ing the Way to a Better Future“.
Before the final steel beam was lifted into place for One World Trade Center, President Barrack Obama inscribed, “We remember. We Rebuild. We come back stronger.” (Telegraph) The symbolism behind this is quite strong, and personify’s the project as more than just a building; it represents the resiliency of the American people, and acts as a tribute to those that lost their lives in the horrific attacks.
It is important that people do not forget the past. History can teach us important lessons about the future, and can be one of the most important tools in making the world a better place. This tower stands as a testament, not only to those who lost their lives, but to the thousands of men and women who have worked on building from the ashes. The lessons learned from the collapsed towers are studied all across the globe, and have helped develop new techniques for creating stronger, more resilient structures. It is believed that this will create a new standard for high rise construction, ensuring that the events of September 11 will never again occur.
On August 26th and 27th, the world’s top bridge engineers and architects congregated to New York City for the 2013 New York City Bridge Conference. This conference was first hosted by the Bridge Engineering Association in 2003, but has quickly emerged as one of the leading bridge conferences in the world.
This year, the conference played host to a number of esteemed guests and industry leaders. The lead designer for Istanbul’s new Bosphorus Bridge presented the design and discussed the current specifications for long span suspension bridges. In addition, Thomas Lavigne, a partner in Lavigne Cheron Architects, presented his design for the new Jacques Chaban-Delmas lift bridge in Bordeaux, France. The projects are illustrated below.
The conference also included many other speakers from around the world. The topics discussed include: Cable Supported Bridges; Bridge Rehabilitation; Seismic Analysis and Design; Bridge Monitoring; and Bridge History and Aesthetics.
Innovation in Bridge Rehabilitation
Corrosion of reinforcing, concrete degradation and concrete spalling are the three main concerns when dealing with concrete bridges. Traditional technologies employ a host of testing machines, causing the process to be quite inefficient; typically only 1000 sq. ft. of bridge deck can be inspected within one hour. Not only does this inefficiency increase the total cost of the project, but it creates traffic congestion and puts the worker’s lives at risk.
Researchers from Rutgers University have now developed a fully autonomous robotic non-destructive-evaluation platform. This product is an ‘all-in-one’ bridge inspection tool, and has the potential to drastically change the face of the industry.
The new product comes equipped with four resistivity probes, two surface imaging cameras, a laser scanner,and a GPS tracking system. This allows the robot to conduct all necessary testing, including: impact echo; ground penetrating radar; ultrasonic surface waves; and electrical resistivity testing. Furthermore, it is designed to move laterally and to turn at zero radius along a pre-set inspection path.
This product is able to inspect 4000 sq. ft. of bridge deck per hour (four times faster than traditional techniques). It also requires fewer workers on site, providing a higher level of project safety and efficiency. In addition, real-time data analysis is undertaken in a nearby van, allowing engineers to quickly address any concerns that arise.
Rapid Replacement of US 6 Keg Creek bridge
In an effort to reduce traffic congestion and fatalities during bridge construction, the US Congress approved the formation of the Strategic Highway Research Program (SHRP) in 2005 (Transportation Research Board). The SHRP has since developed an aptly named Accelerated Bridge Construction (ABC) process, which makes use of pre-fabricated modular construction.
The US 6 Keg Creek Bridge replacement in Iowa took place in 2011 and was a pilot project for the new system. This project would typically take six months to complete. However using ABC, the replacement took only two weeks. The fourteen day bridge assembly was made possible by the use of an on-site fabrication plant. However, this could not be done in densely populated areas. A time lapse of the bridge replacement is presented below.
The old bridge was demolished in just one day, using what Bala Sivakumar of HNTB Architects refers to as a “chop and drop” system. The cost of the replacement totalled $231 per sq. ft..
To connect the ‘lego’ pieces, joints were filled with ultra high performance concrete (UHPC). This created full moment connections, emulating a typical cast-in-place construction. The use of UHPC also allowed the six inches of overlapping reinforcing steel at joints to fully develop. However some problems did arise when applying the UHPC to the old concrete. This was resolved by installing post-tensioned rods which created compression within the joints.
The new concepts and ideas discussed at the conference show how advanced the industry has become. However, there are still many aspects of bridge engineering that require improvement and optimization. As the industry grows, new research will continue to bring forth ideas that revolutionize construction practices. It is therefore imperative that conferences continue to occur, providing a platform for researchers to both share and inspire.
The concept of electrified concrete is not new. In 1980, W. Hymer wrote a research paper outlining the advantages of allowing current to flow through concrete. These included: protecting against lightning, eliminating static electricity, environmental healing and radio frequency interference (Concrete Construction). Despite this, little research was done to develop the concept.
Researchers at the National Research Council of Canada (NRC) have begun developing a concrete which allows electricity to flow freely through it. This “smart concrete” can be used to prevent ice from forming, detect micro-cracks, and create cyber secure buildings. The concrete is mixed using conductive aggregates, which allow current to flow freely through the concrete (Txchnologist). However, this technology is expensive, and would only be implemented on critical sections of road and for bridge decks. In these cases, the cost of implementing the system is overshadowed by the amount cities spend on repairs.
According to NRC’s Rick Zaporzan, “With a few tweaks, it can be used for developing a crack-detection system if it’s hooked up to proper sensors that can monitor and interpret that data”. In addition, the concrete could be used to block electromagnetic signals from entering or leaving, creating a cyber secure building. Rick Zaporzan claims that, “The concrete can also be used to protect extremely sensitive medical equipment, and that’s a huge application” (Txchnologist).
Implementing “Smart Roads”
By allowing electricity to flow through concrete roads, vehicles will be able to “recharge” their batteries while driving. Researchers at Japan’s Toyohashi University of Technology have created a process, wherein current sent through concrete decks is able to power objects on the surface (so far they have used the electricity to light an incandescent bulb). Although the technology is in the early stages of development, it could be used to power electric cars, eliminating the need to pull over and recharge (Engadget).
In addition, the Korea Advanced Institute of Science and Technology (KAIST) has developed a 24km strip of road which is able to supply specially made buses with power. Metal plates embedded within the road surface create electromagnetic waves, which provide electricity to the batteries built into each bus. This system eliminates the need for overhead wires, and allows buses to use significantly smaller batteries (CTV News).
The possibilities for this product are seemingly endless. As cities begin to invest in smart infrastructure, more ideas will form, creating a much different world. Until then, however, it will remain a popular research topic for institutes around the globe.
With the recent advent of modular construction, a number of new and interesting projects are popping up all around the world.
Gluck+, an architectural firm based out of New York City, has designed a medium-income, seven storey, 28 unit apartment building in Upper Manhattan. The buildings lot size posed a serious concern for builders, as it does not provide the area required for traditional construction projects. Therefore, the architects at Gluck+ chose to assemble the residence using 56 pre-fabricated modules, all of which are built in a factory in Berwick, Pennsylvania (Architectural Record).
Building the modules in a factory allowed for high levels of quality control, and provided a much more comfortable building environment for workers. In addition, the project could proceed notwithstanding weather conditions. This has lead to an estimated 15% savings in total project cost. The construction time has also been drastically reduced, and the project will take just under one year to complete (four modular units are installed per day, after the initial foundation has been constructed). The residence, which is expected to be completed in October, is also quite aesthetically pleasing. By pulling some stacks forward and pushing others back, several terraces and overhangs are created, giving the structure a distinct look. The assembly process for the modules is presented in the following video:
A number of other modular residential buildings have been popping up in New York. A 32 storey residential housing unit in the Atlantic Yards development site is under construction. When completed, the building will be a whopping 322 ft tall and will hold the title of tallest modular building in New York. Skanska, the company building this project, has estimated that the total cost of the modular building will be 20% less than a traditional building (Skanska News Report). Similar to Gluck+’s design, 60% of the construction will occur off site. The modules will be built in a controlled environment in Brooklyn’s Navy Yard, and will be transported to site. As a result, the building is expected to attain LEED Silver certification, and produce 70 to 90% less construction waste (than traditional construction).
However, there are often risks when implementing new technologies. The Plumbing Foundation of New York City is suing the Department of Buildings for ignoring a number of major building safety rules. Stewart O’Brien, the executive director of the Plumbing Foundation stated, “It’s a dangerous path we walk down when the city appears to be willing to circumvent the clear words of the law so that wealthy and influential developers can make a few extra dollars by using lower paid and untrained assembly line workers” (The Real Deal).
Despite the issues that builders face with this new technology, it is apparent that modular buildings are becoming very popular with engineers and designers. Projects like this, as well as Sky City in China, are indicators of the shift in construction practices within the industry.
It seems quite ironic that the construction industry, which has a history of using immensely creative and complex building techniques, is now reverting quite successfully to the intuitive building style of LEGO.
In the new age of technology, the concept of “slow and steady wins the race” is becoming less and less applicable. In particular, China has recently constructed a series of buildings using pre-fabricated modular sections, cutting the time spent on the construction site to a matter of days.
The world was shocked when they first saw this phenomenon performed in Changasha China, where a thirty storey building was constructed in just fifteen days. If you have yet to see it, here is the amazing time-lapsed footage of the construction process:
The foundation for the structure was already installed prior to the thirty day count, reducing the overall “construction time”. In addition, the project used pre-fabricated modules that were constructed in a manufacturing plant and later shipped to the construction site. Once the pieces were on site, it was just a matter of putting the pieces in place (similar to a standard LEGO set).
The company behind all this, Broad Sustainable Building, is part of Broad Group which also works on a number of different products (i.e. Air Conditioning Equipment, Air Quality Technology, etc.). Their website has very minimal details, but claims that their buildings can withstand magnitude 9 earthquakes. They also allege that they are 5 times more energy efficient, have 20 times purer air, and use 6 times less material. To find out more about Broad Group, you can visit their website at the following link:
In addition to this, construction has begun on the soon-to-be tallest building in the world, the aptly named Sky City.
Sky City, which will cost less than 1 billion dollars US, will rise to a height of 838 meters (10 meters taller than the Burj Khalifa). The building is set to be completed in April 2014, less than a year before the start of construction. To put that into perspective, the Burj Khalifa took more than five years to build and had a total cost of 1.5 billion dollars US (see CNN Report).
It is quite amazing to think that the processes used in construction have been nearly stagnant for thousands of years. The Egyptians employed a similar style of on-site construction when they began building the pyramids. Over the years, construction times for the worlds largest structures have reduced from 20 years to just over 5. With the new prefabricated structures, construction times have been reduced to less than one year, a truly magnificent feat. This allows engineers to think both ‘bigger’ and ‘higher’ as the cost of constructing buildings using the new technique is greatly reduced.
The concept of prefabrication is not new, but employing it at such a scale is quite revolutionary. It takes the work typically performed on the construction site and moves it into the much more comfortable, controlled environment of the manufacturing plant. As this industry grows, there will be much debate as to which construction process provides the safest, well-rounded structures. Either way, the entire industry is in need of a much needed facelift, and this new process may be just the spark it’s been waiting for.