Cahapter 6 Essay Example | Topics and Well Written Essays - 11000 words

Cahapter 6 - Essay Example Steel being the choice of material, this geometric form adopted with few change by architects of different era and became a distinctive feature of Modern Architecture (Arnold 1996). Besides architectural factor, several steel building, rising up with architectural setback, is outcome of the zoning and planning regulation mandated for the region. Geometric form with architectural setback mandated by urban planning and zoning regulations for high-rise building and skyscraper located in medium and higher density district. First zoning laws in New York first mandated this building form, in 1916 to reduce the shadow of the high-rise building at street and sidewalk (Naeim 1989). According to New York zoning law, the buildings established between 1916 and 1960 raised up to certain height. The height of lower part defined with respect to the width of the street on which building established. Hence, in narrow streets, the setback started at lower story. Starting from that level, they had to s et back until the plan area of one fourth of whole site reached. (New York Skyscrapers 1996) In early years, the effect of setback on seismic performance of steel frames was not main concerns of architects and engineers, especially, if they were constructed in medium or low seismicity region. Although, few steel frames experienced severe damage during past earthquake, no direct correlation between the damage and vertical irregularity found (Youssef, Bonowitz & Gross 1995). In several regions, restrictions set for different building, believed unnecessary for buildings designed with steel frames. (Arnold 1996) and (Naeim 1989) Earthquake resistant design provisions and guidelines, addresses the vertical geometric irregularity as an issue related with the accuracy and reliability of analytical methods, used to define elastic and inelastic seismic demands. Once the