High-rises need seismic retrofitting: Prof
Published on: Friday, July 03, 2015
Kota Kinabalu: High-rise buildings in the State would need to be retrofitted accordingly so that they can withstand earthquakes, expected to happen more frequently in the future.Universiti Malaysia Sabah (UMS) Head of Civil Engineering Programme Prof Dr Abdul Karim Mirasa (pic) said the cost of seismic retrofitting would be significantly steep but did not see any way around it as Sabah will be more prone to stronger earthquakes."The cost of dampers for seismic resistant buildings is cheaper if they are incorporated into the designs of the buildings. I cannot say that all the buildings in the State are not earthquake resistant because designs of buildings are decided by the clients.
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"For example, the Bakun Dam developer (in Sarawak) wanted to incorporate dampers into its design. So they engaged a professor from UTM to do some analysis and simulation and the dam is fitted with proper damping system," he said.However, he said, it is still possible to retrofit existing high-rise buildings in the State and encouraged owners, especially critical government buildings, to equip their properties with proper isolators or dampers to minimise the risk of damages to their buildings.One way of doing this, he said, is by imposing new building code into the existing code to require engineering consultants to include seismic dampers in their designs that could withstand certain magnitude of earthquake.The seismic isolation of a structure reduces the transfer to the structure of ground motion produced by an earthquake.
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"Currently, we are using the British Code in our building design and it does not have seismic damper requirement. Only the Euro Code does. In my opinion, there is an urgent need for us to apply that code for Sabah."This is because in terms of ground acceleration or ground movement, Sabah is categorised as 2B, which is the worst in the whole country. We are experiencing tremors almost every year now.
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"Buildings taller than four storeys are more susceptible to damages due to earthquake. Our buildings can withstand wind load or horizontal load, but not vertical load," he said, adding that various types of seismic dampers that can be retrofitted into buildings include elastomeric isolator, slider, pendulum, rotating ball bearing and dampers.He added that it is surprising that while it is a general knowledge that it is imperative for the government to quickly incorporate the Euro Building Code into the existing building code in the State, nobody wants to do something about it.Perhaps, he said, the Public Works Department should seriously think about it and his team is willing to discuss the matter with them."Of course, the cost of building will be higher but not astronomical.Only between 10 and 20 per cent. considering the cost of retrofitting that would be more expensive. But I see that we are quite relaxed about this now. We are happy with what we have and when tragedy strikes, then we will start to panic," he said.Karim said while Ranau and Kundasang can breathe a sigh of relief for now since the recent earthquake meant that the fault line there has lost its stress, Lahad Datu, which is another earthquake prone area, is a ticking time bomb."The POIC is built right on top of a major fault line. There is an urgent need to retrofit the buildings there. So I think, what they need to do is get a consultant, discuss this thing and plan how they can go about it."It is very difficult to know what will happen if an earthquake strikes, because it would all depend on the magnitude and the epicentre. To be on the safe side, we need to take care of the earthquake problem," he advised.Nevertheless, Karim warned that a longer lasting earthquake, even at a medium magnitude, will still be able to bring a building down due to the mechanical resonance.Mechanical resonance is the tendency of a mechanical system to respond at greater amplitude when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies. It may cause violent swaying motions and even catastrophic failure in improperly constructed structures including bridges, buildings and airplanes.Stay up-to-date by following Daily Express’s Telegram channel.
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