Japanese expert advocates precast housing for Sri Lanka

By Zahara Zuhair
High rise buildings are built so it would ease the urban housing challenges and also for commercial purposes. As so many high rise buildings are mushrooming in Colombo, it’s important to follow proper guidelines and standards when constructing such. 

Having that in mind, Mirror Business recently spoke to Japan Ube Industries Limited Structural Engineer Dr. Takanori Kawamoto during his brief visit to Sri Lanka to attend a construction related forum in Colombo. He is a Doctor of engineering from the Toyohashi University-Aichi of Japan with over 25 years of experience in development design of new retrofitting methods for existing reinforced concrete buildings.
 Below are excerpts of the interview
 

What are the factors that should be considered when constructing a high rise building?
Land or real estate is becoming more and more expensive everywhere in the world. So we, as structural engineers, are focused to make sure we save more space and not restrict it with walls and pillars, so that people have more liveable space inside high 
rise buildings. 

In the olden days high rise buildings had larger columns that consumed a lot of space and large number of columns to support the weight of the structures as we built higher and higher. But now with high strength concrete and new technology that make concrete stronger it is unnecessary to have many columns that take up a lot of space. This helps improve the space availability and the aesthetics of a building. 
It is also important to ensure the safety of the occupants. In Sri Lanka you don’t have earth quakes but in Japan there are earthquakes which damage the structural integrity of buildings. You have to be mindful of that and better to be prepared.  

Ageing population should also be considered when constructing buildings. We have think about how to evacuate them in a case of emergency; how to bring them down fast.
If a person living in higher floors gets a heart attack it could take long time to take him to a hospital. So when we go for high rises we have to think of quick methods of getting people out, including emergency exists. 
Standards must be implemented and applied such as for earthquake reliance, wind reliance. When constructing high rises, it is very important to set the guidelines and strictly adhere to international standards in the structural engineering practice, even if you don’t have them being strictly imposed in the present context.
 

As global green concept is becoming popular, according to you, how should sustainable practices be included when constructing a building?
I think one of the methods to preserve the environment is to reduce wastage, avoid scrap and build each time. If we can use existing old buildings by enhancing their life cycle that also helps improve sustainability. It also makes it unnecessary to spend a lot of money for re-building. Due to the shrinkage of younger population we too face labour force shortage, and capital shortfall. Because of that continuous usage of existing building with seismic retrofit is getting more accepted as the way forward to ensure sustainable 
building practice.
 

Many of the real estate projects target the high-end market, but it’s important to provide affordable homes to everyone. What sort of projects can be developed to cater to the lower-end market?
In Japan, for low cost housing, we use something called precast economy that means we make the house in a factory, all the slabs and walls. We bring it to the location and fix or assemble it on location which is called the precast. This largely reduces construction wastage and helps reduce labour costs.

You cast it in a separate place, bring it and fix it. Those are solid liveable houses, same block you make for everyone. So it’s cheaper rather than building at your place. 
Sri Lanka has to go for that when it comes to low cost housings. For example, architect tells the plans. According to the plan we make different part of the houses and bring it and fix them within a very short period of time. This is not only environmental friendly because no wastage and is not labour intensive. I believe it is a very sustainable method to quickly solve housing problems. 
 

What are the modern trends and technique that are used in the construction industry?
Earlier if you take building columns, they are very large; there was 30 Newtons per millimetres square concrete and that was the tradition those days. Now we are going for over 100 Newtons per millimetres square. Sri Lanka still hasn’t gone up to that level. In certain areas we are going up to 200 Newtons per millimetre. It’s about 5-6 rimes of what is used in Sri Lanka.

Now with the development of high strength concrete, we are using very high reinforce bars, with the column size becoming smaller, they can go up and up. We have a land problem just like in Sri Lanka. It’s very expensive. So with new technology, in smaller spaces, now we can make bigger larger rooms.

In the past, in Japan, when we built a house we don’t build it for a long period in a sustainable wary. Generally after about 25 years we demolish it. But now with higher costs and sustainable approach to construction, we make houses to last long with technology. 
 

A lot more attention should be given for natural hazards. How to tackle such situations?
How we address this in building high risers is by using high strength concrete that can absorb more pressure and also use dampers that improve wind resilience of high risers. This makes the tall buildings only shake during natural hazards but prevent them from collapsing and making sever damage.

Japan has just started seismic design promotion for high-rise buildings as a protection from long-period earthquake ground motion. 
In Japan earthquake occurs frequently and a lot of people die as a result of building related accidents. So now, we are doing construction in such a way that ensures buildings don’t collapse because of earthquakes. We have discovered the technology how to do it. 
 

What can Sri Lanka learn from Japan?
One of the main things I have experienced is the methods Japan has adopted to reduce traffic congestion. Especially in high commercial areas we have taken many measures to reduce traffic and help people move faster and easily for their day to day work.

In Sri Lanka roads are too congested. You have to make them more movable. We also have the same issue, but we have a thing called bypass system. We have used so many various methods in Japan which have brought down the traffic. This helps in emergency situations 
as well.