Our level of unpreparedness exposed
Published on: Tuesday, July 07, 2015
By: David Thien
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Sabah is actually located on the south eastern Eurasian Plate which is bordered by the Philippine Plate and the Pacific Plate.
The Philippine Plate and Pacific Plate move westward at a rate of about 10cm a year, colliding with the Eurasian Plate.
Additionally, the southern part of the Australian plate is moving north at a speed of 7cm per year, and this plate boundary is the most active and unstable.
Although Sabah is 1,000 km away from the collision of the plates, it still receives more compression force than Sarawak and Peninsular Malaysia as it is the closest part of Malaysia to the Philippines and Sulawesi in Indonesia.
Also, what occurred in Ranau was not linked to volcanism, which is only possible in Tawau and Semporna, where an explosion occurred several hundred years ago. Volcano craters are still visible in Tawau. Mount Kinabalu will not erupt, as the igneous intrusion that formed Mount Kinabalu is caused by the compression of the three Plates mentioned previously.
This also can explain why the water at the Poring Hot Springs turned murky for a few hours, as the earthquake appears to have disrupted a clay deposit that interrupts the fault gap that heats up the rainwater which enters the earth.
Strong tremors in Ranau will continue to happen whenever the stored energy exceeds the Earth’s ability to store it. This happens on a regular basis. In the case of Ranau, it happens at an approximate rate of every 25 years, with the first being recorded in 1966 at a magnitude of 5.3 on the Richter scale. This was followed with a magnitude 5.2 earthquake in 1991, Felix says.
According to architect Lo Su Yin who designed the recently soft opening Bay 21 building which won a GreenRE Silver Award, its engineers have incorporated earthquake resistance measures.
Professionals opined that one way of reducing the vulnerability of big buildings is to isolate them from the floor using bearings or dampers, but this is a difficult and expensive process not suitable for low and medium rise buildings and low cost buildings.
The higher weight is in the building, the more it shakes the building about in an earthquake.
The foundations of earthquake resistant buildings require special considerations to allow for ground movement.
Frequently the foundations of traditional buildings are often designed as ‘pinned’, but, because the bottom of every wall or column bears down onto the foundations, the bases do provide a bit of fixity in the static condition.
This gives some additional strength to the walls or columns, in the static condition. But in earthquake conditions, the ground is not static: it moves up and down, side to side, and can change slope.
If you can imagine a base of a wall or column rotating out of the horizontal, you can see it putting a bend into the wall or column. This means that the apparent fixity at the base is now not giving extra strength but, on the contrary, is contributing to early failure.
Also, in earthquakes, the ground can crack and expand or ruck up within the dimensions of a building, and this would put enormous forces into the structure.
For this reason, foundations of buildings in earthquake areas should always have a grillage of reinforced concrete or steel, going both ways under all load supporting members.
Such foundations should have full strength connections to the columns, and should be strong enough to give positional and rotational restraint to all the columns. It is not possible to make buildings ‘earthquake proof’, to the extent that they will resist any earthquake.
However, buildings can be made earthquake resistant by employing the right earthquake engineering practices and considering structural dynamics.
There are a wide variety of earthquake effects – these might include a chasm opening up or a drop of many metres across a fault line. Therefore, it is not possible to design an earthquake proof building which is guaranteed to resist all possible earthquakes.
However, it is possible during the design and construction process to build in a number of earthquake resistant features by applying earthquake engineering techniques, which would increase enormously the chances of survival of both buildings and their occupants, experts say.
All buildings can carry their own weight (or they would fall down anyway by themselves). They can usually carry a bit of floor loads and suspended loads as well, vertically; so even badly built buildings and structures can resist some up-and-down loads.
But buildings and structures are not necessarily resistant to side-to-side loads, unless this has been taken into account during the structural engineering design and construction phase with some earthquake proof measures taken into consideration.
This weakness would only be found out when the Earthquake strikes, and this is a bad time to find out. It is this side-to-side load which causes the worst damage, often collapsing poor buildings on the first shake.
The side-to-side load can be worse if the shocks come in waves, and some bigger buildings can vibrate like a huge tuning fork, each new sway bigger than the last, until failure.
This series of waves is more likely to happen where the building is built on deep soft ground. A taller or shorter building nearby may not oscillate much at the same frequency.
The more weight there is, and the higher this weight is in the building, the stronger the building and its foundations must be to be resistant to side earthquakes; many buildings have not been strengthened when the extra weight was added.
Often, any resistance to the sway loading of the building is provided by walls and partitions; but these are sometimes damaged and weakened in the main earthquake. The building or structure is then more vulnerable, and even a weak aftershock, perhaps from a slightly different direction, or at a different frequency, can cause collapse.
In a lot of multi-storey buildings, the floors and roofs are just resting on the walls, held there by their own weight; and if there is any structural framing it is too often inadequate. This can result in a floor or roof falling off its support and crashing down, crushing anything below.
Earthquakes alone don’t kill people; collapsed buildings do.
Technology designed to keep buildings from collapsing works essentially in two ways: By making buildings stronger, or by making them more flexible, so they sway and slide above the shaking ground rather than crumbling.
The latter technology employs an idea called “base isolation.”
For about 30 years, engineers have constructed skyscrapers that float on systems of ball bearings, springs and padded cylinders. They don’t sit directly on the ground, so they’re protected from some earthquake shocks.
In the event of a major earthquake, they sway up to a few feet. The buildings are surrounded by “moats,” or buffer zones, so they don’t swing into other structures.
“You actually take the foundation of building and you put it either on almost like springs or on a mechanism so it is allowed to move a little bit with the earthquake.”
Well-designed buildings with base-isolation systems ensure that no lives will be lost, no matter the strength of an earthquake.
More difficult than perfecting the technology is figuring out how large of an earthquake will hit a certain area.
“The issue is estimating correctly the seismic demand. I don’t think there is a problem with the technology.”
Buildings made with base isolation can survive earthquakes better.
Still, some engineers are developing technologies to improve on this idea of semi-floating buildings.
Electronic sensors that detect seismic shaking can tell the building how to react to avoid damage.
“It’s in the spirit of the anti-lock braking systems in cars,” he said.
“They measure the dynamic behaviour of the car and adjust the braking force to get it to do what you want it to do.”
Buildings with censors have been built in Japan. Some use accelerometers, which are also found in newer smart phones, to detect motion.
“If they exceed a certain level, then the damper system goes into action and reduces the amount of shaking” in the building.
Others are trying to make earthquake-safe buildings less expensive.
New buildings with earthquake-resistant technology cost about 10 to 20 per cent more than those built without the precautions, engineers said.
The cost of retrofitting old buildings to modern earthquake standards is much more with base-isolation technology.
High costs keep countries from adopting the latest building techniques and technologies.
Making buildings more basic might actually make them stronger and would cost less than high-tech upgrades.
Sometimes it’s very simple. “Simple square buildings that are relatively stout will do very well in earthquakes.
The problem is that most architects and people don’t like to live in square structures with square windows.
Engineers pointed to other simple solutions, such as reinforcing concrete buildings with steel rods and bolting wooden buildings to their foundations, as ways to prevent mass casualties in earthquakes.
But such measures still aren’t taken in many parts of the world.
“There’s a way to reduce the risk,” he said. “The countries that have not adopted the earthquake building codes tend to be poorer countries and perhaps the degree of sophistication or commitment to code enforcement is also an issue in these countries.”
It would be a start for more developing countries to adopt building codes that include measures about earthquake resistance, but that wouldn’t fix everything.
People all over the world, and with all job types, from city planners to construction workers, need to be aware of technologies and building methods that prevent buildings from collapsing in earthquakes.
“You can write a really good code, but you’d better have the capacity to enforce it,” he said. “You’ve got to have people on the ground who are trained and certified in codes and are willing to enforce the codes.”
It is not unusual during earthquakes that due to snapping of electrical fittings short circuiting takes place.
Fire could also be started due to kitchen fires. The fire hazard sometimes could even be more serious than the earthquake damage. The buildings should therefore preferably be constructed of fire resistant matter.
Very loose sands or sensitive clays are two types of soils liable to be transformed by the earthquake so much as to lose their original structure and thereby undergo compaction. This would result in large unequal settlements and damage the building.
If the loose cohesionless soils are saturated with water they are apt to lose their shear resistance altogether during shaking and become liquefied.
Although such soils can be compact, it is expensive to do so.
Ductility refers to the ratio of the displacement just prior to ultimate displacement or collapse to the displacement at first damage or yield.
Some materials are inherently ductile, such as steel, wrought iron and wood. Other materials are not ductile (this is termed brittle), such as cast iron, plain masonry, adobe or concrete, that is, they break suddenly, without warning.
Brittle materials can be made ductile, usually by the addition of modest amounts of ductile materials, such as wood elements in adobe construction, or steel reinforcing in masonry and concrete construction, experts say.
Damageability is also a desirable quality for construction, and refers to the ability of a structure to undergo substantial damages, without partial or total collapse.
A key to good damageability is redundancy, or provision of several supports for key structural members, such as ridge beams, and avoidance of central columns or walls supporting excessively large portions of a building.
A key to achieving good damageability is to always ask the question, if this beam or column, wall connection, foundation, etc. fails, what is the consequence?
If the consequence is total collapse, the design is bad. The importance of the building should be a factor in grading it for strengthening purposes especially hospitals, clinics, home and business buildings, fire and police stations, water supply facilities, cinemas, theatres and meeting halls, schools, dormitories, cultural treasures such as museums, monuments and places of worship, etc.
For categorising the buildings with the purpose of achieving seismic resistance at economical cost, three parameters turn out to be significant: Seismic intensity zone where the building is located, how important the building is, and how stiff is the foundation soil.
A combination of these parameters will determine the extent of appropriate seismic strengthening of the building. Bearing capacity of three foundation soil types is vital: Soils which have an allowable bearing capacity of more than 10 t/m2, those soils, which have allowable bearing capacity less than or equal to 10 t/m2, and those soils, which are liable to large differential settlement, or liquefaction during an earthquake.
Buildings can be constructed on firm and soft soils but it will be dangerous to build them on weak soils, experts opine.
Hence appropriate soil investigations should be carried out to establish the allowable bearing capacity and nature of soil. Weak soils must be avoided or compacted to improve them so as to qualify as firm or soft to avoid large unequal settlements and damage the building.
If the loose cohesionless soils are saturated with water they are apt to lose their shear resistance altogether during shaking and become liquefied.
Although such soils can be compacted, for small buildings the operation may be too costly and these soils are better avoided.
For large building complexes, such as housing developments, new towns, etc., this factor should be thoroughly investigated and appropriate action taken.
Some politicians have urged for Sabah to be declared as earthquake prone as the recent earthquake was not the first time such an incident occurred. Ranau itself had experienced nine earthquakes since 1989 with the strongest being a 5.6 magnitude earthquake that struck in February that year. Last year, a 4.8 magnitude earthquake also struck the same area.
Sabah, albeit not being in the Pacific Ring of Fire, has recorded at least 15 other earthquakes in other areas which included Sandakan, Kudat, Kunak, Lahad Datu, Tawau, Semporna and Keningau.
The earthquakes in those areas occurred between 2005 up to the recent incident, ranging from magnitudes of 3.3 to 5.8.
The recent earthquake in Ranau also brought to light the level of “unpreparedness” by authorities in dealing with the crisis. An official recognition of earthquake prone zones will be the first step towards preparing affected areas and stakeholders by improving safety conditions and safety regulations.
New buildings must follow regulations that allow structures to withstand earthquake tremors.
As it currently stands, Malaysia does not have any standards or guidelines for making buildings, bridges and public transport quake-safe which is an opportunity for the government to improve standard operating procedures (SOP), which should be reviewed and updated to suit recent events.
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