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Thursday, September 23, 1999 Published at 17:22 GMT 18:22 UK

World: Asia-Pacific

Question over Taiwan quake safety

Many buildings in Taiwan survived the earthquake, but some appear to have fallen over like toys.

Quake in Taiwan
This, say experts, is a sign that engineers did not pay enough attention to the foundations, or that the quake virtually turned the soft sediment below into a "liquid" - meaning the apartments should not have been constructed in these locations in the first place.

Dr David Petley, of the UK's Portsmouth University, said: "There are widespread occurrences where building codes are ignored and where development has occurred where it should not have been allowed.

"I suspect that we will see that some of the buildings which have been destroyed have been built on land which according to the planning rules should not have been constructed upon."

Dr Petley has worked on government-backed risk reduction projects in Taiwan since 1991.

[ image: Some buildings withstood the quake - others collapsed]
Some buildings withstood the quake - others collapsed
He said: "There's quite a lot of illegal construction work which goes on in Taiwan as a result of the very rapid development.

"In Taipei we will find that some of the older buildings which have come down in one or another would have broken the building code."

However, seismologists and engineers say that the government's use of three building codes formulated to counter the threat of earthquakes may have spared the island from a death toll far higher than that now being revealed.

The island's last earthquake of this size was in 1935 but for decades the government has planned for a repeat of that moment.

In the capital Taipei, north of the epicentre, modern buildings appear to have been spared from destruction, though one 12-storey hotel completely collapsed in the eastern part of the city.

There have also been reports of concrete foundations of older apartment blocks crumpling but these appear confined to a minority of buildings, some of which may have even been illegally built in the rush for growth.

Tough building code

Walter Mooney of the US Geological Survey said that in comparison with Turkey, Taiwan's preparedness for an earthquake of this magnitude was quite good.

Walter Mooney of the US Geological Survey: "Taiwan compares well with Turkey"
While an estimated 65% of buildings in Turkey were illegally constructed, failing many safety tests, Taiwan has been largely successful in enforcing its own laws.

"One of the biggest differences is that the island has seen some very rapid development in recent times and so they had the advantage of occupying many new buildings," said Mr Mooney.

"These buildings have taken advantage of advances in earthquake engineering.

"Taiwan is one of the most seismically active regions on earth," said Mr Mooney.

"Earthquake preparedness and hazards are something that they deal with virtually every day of their lives so in this regard, they were well warned and quite vigilant."

Modern techniques

Taiwan uses three construction codes - the government's own rules, those of mainland China, and one used by many foreign investors, the California state code.

[ image: Golcuk, Turkey: Almost every building came down]
Golcuk, Turkey: Almost every building came down
These codes demand the use of techniques such as reinforced core concrete columns, deeper foundation piles and "seismic joints" to transmit the massive natural forces away from the seemingly fragile structures.

Professor Amr Elnashai, head of Earthquake Engineering at Imperial College London, said that technology had advanced to the point where a new building could be theoretically tremor-proofed.

"It's not differences in the materials but in the way they are put together," said Prof Elnashai.

Prof Amr Elshanai: "It's not the materials, it is how you put them together"
"If you are designing in an area with no earthquake activity you just design to withstand gravity, the downward forces, and the beams carry the weight and transfer the load to the columns which take it to the foundations.

"But if we start pushing sideways, we need to tie the beams to the columns and make them continuous. We arrange the reinforcements in a fashion to transmit forces from beams to columns.

"It is like a pack of cards. Put two cards vertically on top of each other they can take the load, but push them horizontally and they fall over.

"In theory, we can design to deal with any size or magnitude of earthquake."

"If we have a sensitive structure, for example a nuclear reactor, we say that we will not accept more than a 1% chance of damage.

"But for houses we may say no more than 50%. It is a matter of cost."

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Internet Links

Earthquake Engineering Research Institute

Multidisciplinary Center for Earthquake Engineering Research

Imperial College: Dept of Engineering Seismology and Earthquake Engineering

University of Portsmouth: Dr Petley's Taiwan research

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