Tokyo embraces clean and quiet disassemblingPublished 10/10 at 15:20
Japanese contractor, Taisei Corp., has introduced a safe and environmentally friendly demolition system that is considered by many as a turning point in the industry. The ‘Taisei Ecological Reproduction System’, or more simply known as the ‘Tecorep’ system, is ideal for locations where conventional demolition methods cannot be used such as ultra-high rise buildings. PDi Asia Editor Shinichiro Nakaba reports.
New solutions are continually developed to face new challenges in modern society. Big cities with high population densities have relied on the opening up of areas to create more space for its inhabitants, and now, with the skyscrapers getting older and becoming obsolete, the difficult task is to find ways to renovate areas with minimum impact on the neighbourhoods.
The Tecorep System
In Tokyo, the Taisei Corp. has introduced a safe and environment friendly demolition system for ultra-high rise buildings that is considered by many as a turning point in the industry. Places that cannot use conventional demolition technics such as blasting to bring down buildings, will be able to use the demolition method called the ‘Taisei Ecological Reproduction System’, or simply known as ‘Tecorep’.
The method consists of having the roof of a building covered and reinforcing the main floor structural points to disassemble from the top to the bottom. Sound proof panels are attached to the external part of the construction, not only to minimise usual disturbances such as sound pollution, but also to protect pedestrians from the risk of falling debris. “The main purpose is to complete the disassembling without being noticed, quietly, in the most imperceptible way possible. Our idea is to make the people in the surrounding areas question themselves as to what had just happened when they face an open space instead of a building they used to see every day,” says Mr. Hideki Ichihara, productivity promotion department of architecture and engineering division manager, Taisei Corporation.
Since the disassembling activities are undertaken under a roof, weather conditions do not affect operations, thereby increasing productivity. The system also allows reducing the shielding material by half, with the ‘closed’ nature of the work ensuring noise levels can be lowered by 17dB to 23 dB when compared to conventional demolition methods. Additionally, any dust that in ordinary circumstances would reach a distance of 300m, is reduced by 90%.
Another surprising benefit of Tecorep is its power generation system that creates electricity which can be stored in batteries and used for multiple purposes. The energy is produced when lowering the disassembled material from the top floors to the ground. It is similar to a bicycle chain that generates light while pedalling, and has proved possible to produce 100kW of electricity per hour when a batch of 5t of components is lowered from 100m.
Disassembling work pace depends on the ceiling height; in 2011, the Otemachi Financial Center’s 4m tall floor required six working days to be demolished, whereas in 2012, the Akasaka Prince Hotel needed 10 days to disassemble two floors of 6.4m height. Both projects required a team of approximately 100, consisting of 80 permanent workers for disassembling, and 20 technicians to deal with Tecorep.
“The development of this technology is endless. We are always learning new things and looking out for a wide range of solutions,” explains Mr. Ichihara. The greatest result of this constant development is the cost decrease. Tecorep at first aimed to conduct the disassembling with the building roof intact supported jacks in the construction columns. The present system introduces new and light roofing for the entire building, which reduces the pressure from the top, making it possible to substitute the jacks for clips connecting the roofing to the construction columns and floor base.
The new equipment is simpler, faster to install, safer and allows a significant initial cost reduction, and was used on petro company JX Building close to Tokyo Station between 2016 and 2017. “The cost was reduced by 50%. The temporary jacks for big columns gave way to a system of clips connecting the new lighter roof, and the building permanent structure. The equipment is cheaper and easier to put in practice,” says Mr. Ichihara. For the next stage, the Tecorep project team is studying ways to install the clips only in the construction main points, and not in the entire building as they were used in the previous work, where it is estimated the cost will reduce by a 20%.
Making the roof lighter also helps to decrease the risk of accidents related to earthquake which are a very common occurrence in Japan. With a lighter roof, the building structure gains resistance making the working place and surrounding areas safer for workers and pedestrians. However, the latest development does not mean that the latest version is the best, as it has merely added to the range of services offered by Taisei. Older technology might be more suitable depending on different factors, such as the building design and construction area, which needs to be taken into account in a country where an earthquake might present a different cost benefit scenario when presented with new ideas and equipment.
For tall buildings in big cities
According to Mr. Ichihara, Tecorep System is financially viable for a building with more than 20 floors. For constructions with 10 floors, he believes the cost ends up 15% higher than conventional demolitions method, with the disassembly of more than 30 floors being marginally cheaper. “We have to prepare a new light roof for the entire building. This cost is divided by the floors we have to dissemble. The more we use the equipment in the same building, the cheaper it comes,” he says. The cost must also include the risk of an accident caused by any residue that might fall from a 30th floor building for instance.
The distance between the building and other constructions, such as a road or access, is also important when analysing the cost benefits of any project, furthermore, the proximity of a sidewalk daily used by thousands of pedestrians might make the adoption of Tecorep almost mandatory. The technology is also recommended for use on redevelopment projects, but older buildings condemned to be demolished, might not possess the structural resistance to support this system. Information concerning the supporting ground, and how natural problems such as erosion affect stability etc, also has to be taken into account. Because of the wide range of factors to be assessed and accounted for, the effective use of the system is mainly limited to large cities with a high concentration of skyscrapers that are separated 100m or so. “In Japan, we use Tecorep in Tokyo. Places outside big cities might have no need for this technology,” believes Mr. Ichihara.
Taisei Corp. has now received enquiries from demolition companies in New York, Chicago, London, Singapore, Taipei and Kuala Lumpur concerning its system, however, exporting the technology is not an easy task. The project team needs access to a wide range of information such as plans for the building, dissembling machinery available, working standards and so forth. “In foreign countries, many things are unpredictable. We are not even sure about the existence of a construction plant. We can send engineers to study the scenario, but then the cost might jump,” says Mr. Ichihara.
Developing Tecorep was a much bigger challenge than anyone can imagine, with the project team having to deal with something completely new. There was a need to understand a concept where things that seem to be simple, would not work, and deal with matters such as carbon dioxide emissions in a close environments and working without natural light. “We had to conduct the activities in a closed place, and people outside would not even perceive there was a disassembling operation conducted next to them,” says Mr. Ichihara.
It took two years to put the ideas behind the system into practice, and since 2011 Tecorep has started four demolition projects using Tecorep, with the company finding that every building has its own unique challenges. Despite the extensive budgeting and cost-benefit analysis required before using the system, there is not a department responsible for Tecorep at Taisei Corporation. Four people heading different divisions study the clients’ requirements, with planning a new project taking around a year. If the project is approved, another six months are required to finalise details before starting the disassembling.