The study of the response of tall buildings to wind has become more critical with the increase of super tall buildings in major cities around the world. Outrigger-braced tall building is considered as one of the most popular and efficient tall building design because they are easier to build, save on costs and provide massive lateral stiffness. Most importantly, outrigger-braced structures can strengthen a building without disturbing its aesthetic appearance and this is a significant advantage over other lateral load resisting systems. Therefore this thesis focuses on the optimum design of multi-outriggers in tall buildings, based on the standards set out in the Australian wind code AS/NZS 1170.2. / As taller buildings are built, more outriggers are required. Most of the research to date has included a limited number of outriggers in a building. Some tall buildings require more outriggers especially for those more than 500m building height. Therefore there is a need to develop a design that includes many outriggers (e.g. more than 5). In addition, wind-induced acceleration is not covered in most of the research on outrigger-braced buildings. The adoption of outrigger-braced systems in tall buildings is very common and therefore a discussion of wind-induced acceleration will be included in this thesis. / Most of the current standards allow for the adoption of a triangular load distribution in estimating the wind response of a structure. However, there are only few publications on the utilization of a triangular load distribution to determine the optimum location of a limited number of outriggers. This issue will be addressed in this thesis and will be compared with a uniformly distributed wind load. Further to this, an investigation will be carried out on the factors affecting the efficiency of an outrigger-braced system in terms of the core base bending moment and the total drift reduction. / This thesis principally provides a preliminary guide to assess the performance of outrigger-braced system by estimating the restraining moments at the outrigger locations, core base bending moment, the total building deflection, along-wind and crosswind acceleration of a tall building. While many computer programs can provide accurate results for the above, they are time-consuming to run. For designers working on the preliminary design in the conceptual phase, a quick estimation drawn from a simpler analysis is preferable. Therefore, as an alternative to computer-generated estimations, a methodology for an approximate hand calculation of the wind-induced acceleration in an outrigger-braced structure will be developed.

The civil engineering and architectural communities are highly focused, these days, on designing buildings that maximize utilization of energy available from natural resources. This dissertation presents a quantitative study of the effect of high-rise office building morphology on energy and structural performances for the major climates. The parameters of the building morphologies are varied - the building footprint shape, the placement of the structural core/walls, and the building orientation. The energy analysis is performed using Autodesk Ecotect Analysis 2011; while using SAP2000 for the structure analysis and design. The key observations are: 1) the building morphology has a significant effect on the annual energy consumption, 2) placement of the structural core/walls in the east and west sides significantly improve the energy performance, 3) the tradeoff in the cost of placing the structural core/walls to maximize operating energy efficiency is too great, 4) for built to code buildings the energy demand may be considered marginally sensitive to changes in aspect ratio, and 5) high quality thermal properties of code-built envelope systems offer more flexibility to designers with regard to the building site planning without creating negative impacts on total energy demand.

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Techniques for preliminary analysis of various tall building systems subjected to lateral loads have been studied herein. Three computer programs written in Matlab® graphical user interface language for use on any personal computer are presented. Two of these programs incorporate interactive graphics. A program called Wall_Frame_2D is introduced for two-dimensional analysis of shear wall-frame interactive structures, using the shear-flexural cantilever analogy. The rigid outrigger approach was utilized to develop a program called Outrigger Program to analyze multi-outrigger braced tall buildings. In addition, a program called Frame Tube was developed which allows analysis of single and quad-bundled framed tube structures. The tube grids are replaced with an equivalent orthotropic plate, and the governing differential equations are solved in closed form. Results for lateral deflections, rotations, and moment, shear, and torque distributions within the various resisting elements are compared against other preliminary and "exact" matrix analysis methods for several examples. SAP2000 was used to obtain "exact" results. The approximate analyses are found to give reasonable results and a fairly good indication of the behavior of the actual structure. These programs are proposed for inclusion in a knowledge-based approach to preliminary tall building design. The tall building design process is outlined and criteria are given for the incorporation of these "Resource Level Knowledge Modules" into an integrated tall building design system.

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