Earthquake-Resistant Structures
Organizational strategies to minimize earthquake damages in Dhaka City
Dhaka, the capital of Bangladesh, is vulnerable to earthquake disasters due to spontaneous urbanization, high population density, haphazard growth of high-rise buildings, unplanned infrastructure, etc. Besides these, inadequate disaster management plans make Dhaka more vulnerable to disaster risk if a seismic tremor of magnitude 7 or over on the Richter scale occurs. An effective earthquake disaster prevention program is required at organizational levels to minimize the risk of disaster.
Earthquake risk in Dhaka city
Dhaka is vulnerable to earthquake disasters for several reasons.
Located in risky seismic zone
Bangladesh has been divided into three main earthquake zones. According to the seismic zoning of Bangladesh, Dhaka falls into Zone 2, that also includes Rajshahi, Natore, Magura, Meherpur, Cumilla, Brahmanbaria, and Feni. Here, the Chittagong-Comilla-Dhaka and Tangail areas have a possible earthquake risk of magnitude of 6 on the Richter scale.
Unsafe structures
The government of Bangladesh has developed national building codes, which include detailed guidelines for earthquake-resistant design of concrete and steel structures. However, these codes are not officially enforced. Due to the lack of effective enforcement mechanisms, it is feared that many new structures do not maintain the necessary requisites for earthquake-resistant construction. Therefore, the number of unsafe structures in Dhaka city is increasing.
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Furthermore, many high-rise buildings and garment factories are being constructed in Dhaka without following the rules. Furthermore, not leaving adequate open spaces while designing buildings also increases the risk of casualties if structures collapse due to earthquakes. Besides these, a significant portion of the structures of Dhaka city have encroached upon the streets and roadways, making those infrastructures more vulnerable for passersby and commuters during earthquakes.
As a result, after a major earthquake of magnitude 7 or over on the Richter scale, these structures can collapse, block streets, hinder rescue operations, and bring the greatest devastation to Dhaka city.
High population density
The population density is very high in Dhaka city. With more than 23.9 million people, and an average of 38,000 people per square kilometer, Dhaka is one of the most crowded cities in the world. As the city is expanding quickly, many new buildings, bridges, roads, and other infrastructure are being constructed to fulfill the needs of this big population.
Millions of inhabitants of Dhaka city live in poorly made buildings.
Soil type
Geographically, Dhaka city is made of soft, wet delta soil, which makes the structures more vulnerable to earthquakes.
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Some effective organizational measures to mitigate earthquake disaster risk in Dhaka city
As an earthquake is a natural disaster, it cannot be prevented. However, adequate measures at national, organizational, and individual levels can minimize the loss of lives and property. Here the organizational measures will be discussed.
Decentralization
Dhaka is the center of the economy and administration of Bangladesh. Therefore, Dhaka’s risk in the context of the earthquake can make the economic stability, and public administration of Bangladesh vulnerable.
Therefore, decentralization of key financial and administrative activities can minimize the damage if Dhaka faces any major earthquake.
Planning for water and airways
If a major earthquake occurs, the existing road communication system in and around Dhaka can be affected, but the effect will be less in waterways. So there should be a plan to restore the existing waterways (canals, rivers in and around Dhaka) for use during the earthquake emergency period.
Dhaka city is surrounded by three rivers, Buriganga, Sitalakhya, and Turag. These rivers can be again turned into the lifeblood of the city. These rivers need extensive dredging to ensure navigability around the year. The city's circular riverway can be a very useful communication route.
Furthermore, helicopters can also perform during emergency response. This will be an effective way in the field of rescue and emergency services distribution.
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Build earthquake-resistant structures
If the structures are not earthquake-resistant, severe damage to lives and properties can occur after an earthquake of 7 or more magnitude hits the city. To minimize the risk of earthquake destruction, earthquake-resistant buildings should be built.
The city authority can create strict regulations and make it obligatory for planners, engineers, and architects to consider earthquake-resistance capacity while making plans and designs.
The common steps of building earthquake-resistant structures include creating flexible foundations; building shear walls, moment-resisting frames, and diaphragms; building Seismic Invisibility Cloak; using earthquake-resistant materials, etc.
Seismic hazard mapping and database preparation
It is essential to develop a comprehensive regional database of all recorded historical earthquakes in and around Dhaka city. A comprehensive regional seismic hazard map of Dhaka city should be prepared to incorporate appropriate building codes.
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Resources such as scientists, seismologists, geologists, engineers, architects, planners, GIS experts, remote sensing experts, and other technicians should be prepared through higher education and relevant training programs to build leadership in earthquake hazard assessment research in Bangladesh.
2 months ago