Building style caused collapses, book says

PUBLISHED : Tuesday, 26 May, 2009, 12:00am
UPDATED : Tuesday, 26 May, 2009, 12:00am

The use of old-fashioned building methods was the main reason schools collapsed more readily than other buildings in the Sichuan earthquake last year, according to a book compiled from hazard assessment reports.

The book, entitled Wenchuan Earthquake Building Damage Investigation and Analysis of Post-disaster Reconstruction, was published by China Architecture and Building Press. Reports about the book appeared in several mainland newspapers yesterday.

Produced by some of the most prominent universities on the mainland, the book supports the official conclusion that there is no evidence that poor building quality caused thousands of students to die in the disaster. Parents have tried to sue builders, but courts have refused to accept the cases.

A main theme of the book is that the school buildings collapsed not because of bad quality but their old-fashioned structure.

'Most of the schools in the quake zone used masonry structure ... resulting in relatively poor earthquake resistance,' said one of the papers, jointly written by civil engineering professors at Tsinghua, Southwest Jiaotong, and Beijing Jiaotong universities.

'Most government buildings use frame structures with reinforced concrete, and they suffered the least.'

The schools were mostly built according to a masonry structure - an old method in which individual units are built one on top of the other and bound together with mortar. The Pyramids in Egypt and the Great Wall are among the most successful masonry structures.

But few masonry structures can stand for long periods, and they are especially vulnerable to earthquakes. Even a very slight horizontal shift - which seismologists call twisting and stretching - can make them crumble.

A frame structure with reinforced concrete was invented during the Industrial Revolution and widely adopted in western countries after the San Francisco earthquake in 1906. In this method, steel reinforcement bars are set into concrete to create a flexible and extremely hard-to-break frame. This structure significantly outperforms masonry during earthquakes.

But frame structures are also usually more expensive than masonry. They were not popularly adopted on the mainland until after the Tangshan earthquake that killed more than 240,000 people in 1976.

In the Sichuan quake zone, and other less developed areas, masonry is still the dominant structure for schools, government-subsidised housing and factories.

'In some remote towns and villages, concrete and steel are scarce. It is much cheaper to make bricks with mud to build a school,' said a professor at the Research Institute of Structural Engineering and Disaster Reduction at Tongji University in Shanghai, who refused to be named because of the sensitivity of the issue.

According to a guideline released by the central government, masonry is still allowed in school reconstruction projects in Sichuan. Supporters of masonry argue that it is unrealistic to ban the building method and that with reinforcement the buildings can still resist some earthquakes.