Quake, better to prepare than await a surprise
Friday, 22 January 2010
Mir M. Ali
A quake of the magnitude of 6 on the Richter scale hit Bangladesh in the morning of September 4, 2009. It shook the entire country. Its epicenter was located at 450 kilometers north-east of Dhaka. A tremor of 5.3 magnitude on the Richter scale hit Bangladesh more recently. Bangladesh has a history of severe quakes. Both old and new buildings in densely populated Dhaka are vulnerable to quakes. In 2005 the US Department of Defence (DOD) rated Bangladesh as a major earthquake zone. Previously it was in a moderate seismic zone. What does this mean for the safety of over 15 million people who live in Dhaka?
Are all the buildings in Dhaka built according to specifications that can withstand quakes? How many of them would survive, God forbid, a severe quake?
Would the residents be able to live in peace in the surviving buildings when the neighbours' shelters would be damaged or destroyed?
Some areas of Mymensingh, hit by a quake of 7 magnitude on July 27, 2008, were spared of major structural and non-structural damage. That was not the case with China on August 30, 2008. The "Great Sichuan Earthquake", recorded as the 19th deadliest quake of all times, left 69,227 dead, over 374,000 injured, 4.8 million homeless and over 18,000 others traceless.
Many of the cities had to be evacuated since people did not want to live in a haunted environment without functioning infrastructure and city services. Although the quake epicenter was in Wenchuan County in Sichuan province, the tremors were felt as far away as 1000 miles in both Beijing and Shanghai. Even Bangladesh was jolted 8.5 minutes after the quake had hit China, only three months before the 2008 Summer Olympics. China's central government announced a US $146.5 billion rebuilding programme.
How Bangladesh would cope with such a calamity and its aftermath? In Dhaka, one of the most densely populated megacities of the world, a quake would cause much greater losses to life and property. However, Bangladesh University of Engineering and Technology (BUET) deserves credit for its seismic research and mapping of vulnerable zones in Bangladesh. Earlier, Bangladesh National Building Code (BNBC) was created to design quake-resistant building structure. BNBC classified Dhaka as seismic zone 2 for its vulnerability. Its Uniform Building Code (UBC) classifies zones in numerical order as it is done in the western region of the U.S. Most U.S. states, however, have adopted the International Building Code (IBC), which designates seismic design categories, rather than zones. Dhaka is classified under Category D, equivalent to Zone 3, that is a major risk area. Of course, the design requirements could make construction costlier. The code-writing and regulatory authorities in Dhaka can in no way ignore this requirement for future code revisions, that would cost construction 10 to 15 per cent over the standard cost. But it would be better to make the expenditure before than later. Life is undoubtedly more important.
People of China showed how to cope with quake aftermaths. But, unlike Dhaka, Wenchuan is not a political, economic or communication nerve centre.
San Francisco politicians, afraid of scaring the people, after the Great Earthquake of 1906, lied about the damage caused. There would be no excuse for Bangladesh as the authorities are well aware of the value of quake resistance structure in a seismic calamity.
Bangladesh needs to be prepared and not alarmed. "Forewarned is forearmed". It is good policy to make the best use of knowledge. Is Bangladesh doing that?
With the preparations in place, costing an extra 10 or 15 per cent, Bangladesh would not have to regret. This decision is for the political authorities to take. At stake is the security of life and property. The better-off should opt for the extra expenditure on shelter.
Quake-resistant design requires:
l Ductility, that is, the structure will swing, not collapse
l Toughness, that is, the structure will have enough energy absorption capacity
l Redundancy, that is, the structural elements will be able to redistribute stresses through adequate load sharing
l Appropriate architectural design, that is, maintaining structural symmetry, avoiding major mass and stiffness variations in plan and elevation, re-entrant corners in plan, and connecting very flexible elements to very rigid elements, etc.; and paying attention to non-structural elements
BUET gives a reason for cheer and hope, carrying out research on seismicity to re-identify seismic-prone areas of Bangladesh. Newspaper articles in Dhaka are making the public aware about the quake danger. Architects and structural engineers in Bangladesh are paying greater attention to quake-resistant building design following BNBC regulations.
Public participation in and acceptance of building modifications in keeping with quake-resistant designs would benefit Dhaka and other vulnerable areas in Bangladesh. Quake-proof buildings would save life if a quake strikes Dhaka. And it strikes without a notice.
(Professor and Chairman of the Structures Division in the School of Architecture, University of Illinois at Urbana-Champaign, the writer is a Fellow of the American Society of Civil Engineers as well as of the Council on Tall Buildings and Urban Habitat. He teaches a graduate course on earthquake-resistant design. Also a licensed structural engineer in Illinois, he can be reached at e-mail: bdesh1944@yahoo.com)
A quake of the magnitude of 6 on the Richter scale hit Bangladesh in the morning of September 4, 2009. It shook the entire country. Its epicenter was located at 450 kilometers north-east of Dhaka. A tremor of 5.3 magnitude on the Richter scale hit Bangladesh more recently. Bangladesh has a history of severe quakes. Both old and new buildings in densely populated Dhaka are vulnerable to quakes. In 2005 the US Department of Defence (DOD) rated Bangladesh as a major earthquake zone. Previously it was in a moderate seismic zone. What does this mean for the safety of over 15 million people who live in Dhaka?
Are all the buildings in Dhaka built according to specifications that can withstand quakes? How many of them would survive, God forbid, a severe quake?
Would the residents be able to live in peace in the surviving buildings when the neighbours' shelters would be damaged or destroyed?
Some areas of Mymensingh, hit by a quake of 7 magnitude on July 27, 2008, were spared of major structural and non-structural damage. That was not the case with China on August 30, 2008. The "Great Sichuan Earthquake", recorded as the 19th deadliest quake of all times, left 69,227 dead, over 374,000 injured, 4.8 million homeless and over 18,000 others traceless.
Many of the cities had to be evacuated since people did not want to live in a haunted environment without functioning infrastructure and city services. Although the quake epicenter was in Wenchuan County in Sichuan province, the tremors were felt as far away as 1000 miles in both Beijing and Shanghai. Even Bangladesh was jolted 8.5 minutes after the quake had hit China, only three months before the 2008 Summer Olympics. China's central government announced a US $146.5 billion rebuilding programme.
How Bangladesh would cope with such a calamity and its aftermath? In Dhaka, one of the most densely populated megacities of the world, a quake would cause much greater losses to life and property. However, Bangladesh University of Engineering and Technology (BUET) deserves credit for its seismic research and mapping of vulnerable zones in Bangladesh. Earlier, Bangladesh National Building Code (BNBC) was created to design quake-resistant building structure. BNBC classified Dhaka as seismic zone 2 for its vulnerability. Its Uniform Building Code (UBC) classifies zones in numerical order as it is done in the western region of the U.S. Most U.S. states, however, have adopted the International Building Code (IBC), which designates seismic design categories, rather than zones. Dhaka is classified under Category D, equivalent to Zone 3, that is a major risk area. Of course, the design requirements could make construction costlier. The code-writing and regulatory authorities in Dhaka can in no way ignore this requirement for future code revisions, that would cost construction 10 to 15 per cent over the standard cost. But it would be better to make the expenditure before than later. Life is undoubtedly more important.
People of China showed how to cope with quake aftermaths. But, unlike Dhaka, Wenchuan is not a political, economic or communication nerve centre.
San Francisco politicians, afraid of scaring the people, after the Great Earthquake of 1906, lied about the damage caused. There would be no excuse for Bangladesh as the authorities are well aware of the value of quake resistance structure in a seismic calamity.
Bangladesh needs to be prepared and not alarmed. "Forewarned is forearmed". It is good policy to make the best use of knowledge. Is Bangladesh doing that?
With the preparations in place, costing an extra 10 or 15 per cent, Bangladesh would not have to regret. This decision is for the political authorities to take. At stake is the security of life and property. The better-off should opt for the extra expenditure on shelter.
Quake-resistant design requires:
l Ductility, that is, the structure will swing, not collapse
l Toughness, that is, the structure will have enough energy absorption capacity
l Redundancy, that is, the structural elements will be able to redistribute stresses through adequate load sharing
l Appropriate architectural design, that is, maintaining structural symmetry, avoiding major mass and stiffness variations in plan and elevation, re-entrant corners in plan, and connecting very flexible elements to very rigid elements, etc.; and paying attention to non-structural elements
BUET gives a reason for cheer and hope, carrying out research on seismicity to re-identify seismic-prone areas of Bangladesh. Newspaper articles in Dhaka are making the public aware about the quake danger. Architects and structural engineers in Bangladesh are paying greater attention to quake-resistant building design following BNBC regulations.
Public participation in and acceptance of building modifications in keeping with quake-resistant designs would benefit Dhaka and other vulnerable areas in Bangladesh. Quake-proof buildings would save life if a quake strikes Dhaka. And it strikes without a notice.
(Professor and Chairman of the Structures Division in the School of Architecture, University of Illinois at Urbana-Champaign, the writer is a Fellow of the American Society of Civil Engineers as well as of the Council on Tall Buildings and Urban Habitat. He teaches a graduate course on earthquake-resistant design. Also a licensed structural engineer in Illinois, he can be reached at e-mail: bdesh1944@yahoo.com)