Structural Efficiency Improvement by Optimization and Performance Based Techniques for Tall Buildings

Abstract

The advent of 21st Century has seen developments in every aspect of science and technology but with these advancements came the issue of sustainability. Material consumption has to be planned so as to use the minimum amount of material possible to reduce the amount global carbon emissions. Engineers have this responsibility on their shoulders to optimize the design processes to save the material while ensuring the performance of design. Moreover there is a dire need to plan our cities in a manner to avoid urban sprawl. One solution to this problem is the use of tall building in urban landscape. Tall buildings not only creates a large floor area for a given small ground space for urban activity but also saves a huge amount of material. Tall buildings is one of the best solutions to the modern problem of urban sustainability. This text limits its scope to the same problem of optimizing the material usage in tall buildings while ensuring the performance of structure. While achieving the required objective it becomes compulsive to sacrifice the code requirements. This cannot be done if the alternative solution to code has not been verified for performance objectives. The process starts with the analysis of an existing building. In our case we chose “Hochhaus Uptown München” which is the tallest building in Munich, Germany. The building is analysed for different schemes of gravity and lateral loads. After the analysis is done the reinforcement is calculated for individual concrete sections. After that the material tonnage for whole building is calculated for later comparative analysis. The second part of this text deals with selection of the optimized aspect ratio. The objective this whole process is to find the maximum height of building so that the dominating stresses remain due to the gravity loads. After this height lateral forces which include wind and seismic forces become dominant which requires additional design requirement and this extra material usage. The philosophy which governs the whole process is that under maximum gravity and seismic loads there will be stresses in the perimeter structural systems, under these conditions there should be sufficient building height so that the moments due to building weight cancels the moment effects due to lateral loads so that under extreme lateral load conditions the perimeter structural system becomes neutral in terms of stresses.