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Our homeland is a relatively small country with huge population. And Dhaka being the capital of Bangladesh, most people are centered in this city. As per current situation Dhaka has a population over 18 million which is almost 11% of the country’s total population. Apart from solving this over population problem, we have to deal with the existing situation and make a suitable habitat for people. But making more and more buildings covering the land area and cutting trees is not a proper solution as it threatens our environment. One possible solution can be instead of covering land we can make skyscrapers as residential buildings. The tallest residential building of the world is situated in New York city named ‘432 Park Avenue’ which is 425.5 meters in height and has 96 floors. Currently City Centre Bangladesh is the tallest building in Dhaka having 37 floors. But it serves commercial purposes. To construct skyscrapers for residential purposes we have a lot of things for consideration.
Sub Structure:
Generally the self weight of the skyscraper which is called dead load is more than the load it will bear or the live load. And with the increase in height the dead load also increases non-linearly. There are lateral loads due to wind and consequent moments which causes increased vertical loads. So foundation is the most important structure since it transfers the vertical load to soil. Combined Piled Raft Foundation (CPRF) is more effective for high rise buildings. In CPRF both piles and raft transfer load to soil by skin friction and end bearing and by contact pressure due to soil respectively. Using this complex structure reduces the numbers of piles to be used. Again only using raft foundation which is a shallow foundation may not satisfy the total settlement and the differential settlement requirements of the building but it improves the ultimate load capacity. So CPRF will satisfy load bearing capacity and reduce the settlement and differential settlements.
Super Structure:
For skyscrapers shear wall is an important element. It is reinforced concrete wall which is provided throughout the entire height. It can be exterior or interior. It resists lateral loads which come mainly from wind and seismic loads. Thus it provides stiffness to the building by carrying horizontal forces like earthquake force. Again from the seismic zoning map we can see that Dhaka is in zone 2 which is moderate in earthquake danger. Zone 3 and 4 is severe and very severe respectively for danger. So avoiding these places we can build skyscrapers in Dhaka and in other places near Dhaka.
Requirements for Living:
As leaving from the top floor of a skyscraper will not be easy during fire, the building itself should be fire resistant and have enough fire extinguishers. Concrete has good fire resistance. That means it has low thermal conductivity and it protects from spread of fire. But mostly steel frame technique is used to construct high rise building for steel having high tensile strength. Again steel is comparatively lighter material. So we can develop a method of composite structure using steel and concrete. The buildings can have water, foam and Carbon Dioxide extinguishers. The building should also have enough numbers of emergency exits. In case of water supply, normal pressure is not enough. The buildings need several systems for boosting water pressure at different height. The skyscrapers need to be divided into zones. The lower one or two zones can get water through normal pressure of the main systems. But the upper zones need boosters to uplift water. Again skyscrapers have a huge demand for electricity. The more families lives in the building, the more power supply is required. So there should be multiple sources for electricity supply as well as standby source of power like generators. Temperature control is another issue in skyscraper. The building can be divided into different zones equipped with its own chiller plant and water heater. In case of elevator, if there is not enough numbers of elevators it will be time consuming for people to go up and down. Using double deck elevators can be an effective solution as it allows double people to fit in and it covers two floors at a time. So fulfilling these facilities skyscrapers as residential buildings can be constructed. Though as a developing country, skyscrapers might not be economical in some cases, engineers, architect and the government should work on this matter and make residences for all the people in Bangladesh and keep the environment green and clean.