Wednesday, June 27, 2012


by Ayşin SEV and Aydan ÖZGEN

High-rise office buildings, which are developed as a response to population growth, rapid urbanization and economic cycles, are indispensable for a metropolitan city development. In 1930, Clark and Kingston (cited in Klaber, 1930) made the following observations The skyscraper: A study in the economic height of modern office buildings: “Given the high land values in central business sections of our leading cities, the skyscraper is not only the most efficient, but the only economic utilization of certain strategic plots. An exhaustive investigation… has conclusively demonstrated that the factors making for diminishing returns in the intensive development of such plots are more than offset by the factors making for increasing returns…” (Klaber, 1930).
This statement holds true for today; however, the relationship between cost and benefit is more complex in today’s global marketplace. The political ideology of the city plays an important role in the globalization process (Newman and Tornely, 2005; Abu-Ghazalah, 2007). The current trend for constructing office buildings is to build higher and higher, and developers tend to compete with one another on heights. Tenants also appreciate a landmark address and politicians are conscious of the symbolic role of high-rise buildings. The international and high technology styles have accompanied nearly all new tall buildings and became landmark of our cities (McNeill and Tewdwr-Jones, 2003). Nonetheless high-rise office buildings are more expensive to construct per square meter, they produce less usable space and their operation costs are more expensive than conventional office buildings. The space efficiency, as well as the shape and geometry of the high-rise building need to satisfy the value and cost of the development equation. Space efficiency, which is determined by the size of the floor slab, dimension of the structural elements and rationalized core, goes along with the financial benefit.
By the end of 1990s, at more than 30 stories, net to gross floor area ratios of 70-75% were common in office buildings (Table 2) (Davis Langdon and Everest, 1997). However, Yeang (1995) stated in his book “The Skyscraper: Bioclimatically Considered” that net-to-gross floor area should not be less than 75%, while 80% to 85% is considered appropriate. Wherever the tall building is being constructed, achieving suitable space efficiency is not easy, since it is adversely affected by height as core and structural elements expand to satisfy the requirements of vertical circulation and resistance to lateral loads. Space efficiency can be increased by the lease span, which is defined as the distance between the core and exterior wall.
Factors affecting the design of high-rise buildings vary from country to country, such as local climate, zoning regulations, cultural conditions, technological opportunities, and etc. For instance, in Germany, where building codes dictate shallow floor slabs of 8.0 m, efficiencies of 60-70% are common, whereas London’s Canary Wharf Tower, can achieve a netto-gross ratio in excess of 80% with floor slabs of 2500 m2, and 11.0 m lease span. In this respect, when the high-rise office buildings of Turkey are investigated, conceivable space efficiency is not achieved when compared with the examples from the world. As Watts and et al. (2007) stated in their article that “fat is happy”, the highest office buildings of Turkey are happy, however, they are not so successful in respect to space efficiency. Therefore this research tends to compare and reveal the similarities and differences between the tallest office buildings at abroad and in Turkey in terms of space efficiency.
Canary Wharf Tower

Canary Wharf Tower, by Destinys Agent

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