Please use this identifier to cite or link to this item: http://10.1.7.192:80/jspui/handle/123456789/1608
Title: Study of Outrigger Structural System for High Rise Building
Authors: Patel, Jigneshkumar C.
Keywords: Civil 2008
Project Report 2008
Civil Project Report
Project Report
Civil (CASAD)
CASAD
08MCL
08MCL013
CASAD 2008
Issue Date: 1-Jun-2010
Publisher: Institute of Technology
Series/Report no.: 08MCL013
Abstract: Tall buildings are rapidly increasing around the world, owing to the rise of the land value and the developments in the construction technology. As buildings increase in height, it becomes more important to ensure adequate stiffness against lateral forces. In tall buildings, lateral loads caused by wind and earthquake actions are of- ten resisted by different structural system which is developed to satisfy the strength, stiffness and ductility criteria. The savings in structural materials and cost can be dramatic in high-rise buildings if certain structural systems are employed to utilize the full capacities of the structural elements. The advances in structural systems and material technology made it possible to design light and slender structures satisfying economical and architectural requirements. Various braced-frame and shear wall-frame system have been developed to satisfy above criteria. However, such structures face the problems of vibration induced by the wind load and inconveniences may be caused to the occupants of the building due to excessive defection and acceleration. In order to limit the wind drift to accept- able limit and to maintain human comfort with optimum utilization of material, the outrigger and belt truss structural system is developed. In this system the external columns are connected to the central core wall with very stiff horizontal cantilevers known as outrigger and deep spandrel girder or truss around structure. Outrigger and belt truss can be provided at one or more levels. It is very effective in increas- ing stiffness of structure, reducing both the horizontal top defection and overturning moments. The aim of present study is to understand behaviour of outrigger structural sys- tem under uniform lateral load and effects of outrigger on top storey displacement, core bending moment and drift in high rise building. To control drift in tall buildings: the core and columns are necessary components of the structure while the additional elements, the outriggers, are usually incorporated within the plant levels. The mag- nitude of the reduction in drift and core moment depends on the relative flexural rigidities of the core, outriggers and columns and also the location of outrigger. In the present report behaviour of the outrigger structural system under lateral load is presented. The restraining moments of outriggers acting on the core wall and the equation of the horizontal top defection are derived for two outrigger system. Gener- alized solutions of forces and defections are derived based on two outrigger systems. Approximate manual analysis of structure under lateral uniform wind pressure is presented by converting three dimensional building into equivalent two dimensional building. Comparison of result of approximate manual analysis, two dimensional analyses and exact three dimensional analysis is discussed. The optimum location of outrigger is found out for the one and two outrigger struc- ture system to minimize the wind responses. Buildings with four different locations of outriggers are analysed to obtain optimum location for both one and two outrig- ger system. Parametric study is carried out by varying sizes of structural elements like core, column and outriggers. Nine cases are considered for parametric study of outrigger system. A 50-story reinforced concrete building is studied to determine the optimum location and parametric study. Modeling analysis and design of building with and without outrigger is carried out using ETABS software. Analysis and design of 50-storey regular R.C. building is presented with all loads and load combinations. The static and dynamic analysis of 50 story building is car- ried out using ETABS software. Analysis and design results are found for the building with one and two outrigger structural system and compared with building without outrigger system. Cost comparison of building with and without outrigger system is discussed. The analysis results show that outrigger is very effective in increasing stiffness of structure, reducing both the horizontal top defection and overturning moments in core. The optimum location to construct the outrigger is at mid-level of the height of the building when one outrigger is used in structural system. When two outriggers are used in structural systems, the optimum location to construct the outriggers is between one third to two third of the height of the building. Increasing dimensions of core and column has lower influence in reduction of displacement, core bending mo- ment and drift compared to increasing dimensions of outrigger. Increasing outriggers in high-rise building reduced the total steel quantity of building compared to building without outrigger and also reduced top storey displacement, drift and core bending moments which are very important parameters in tall buildings. So outrigger and belt structural system is most effective structural system in tall buildings. The content of major project is divided in to various chapters. Chapter 1 includes general introduction of outrigger and belt structural system. Chapter 2 presents the review of literature about behaviour and analysis of outrigger and belt structural system. The behaviour of outrigger structural system under uniform lateral load is presented in chapter 3. Comparison of approximate manual analysis and exact three dimensional analysis is discussed in chapter 4. Optimum Location of outrigger under uniform lateral load is presented in chapter 5. Parametric Study of outrigger Struc- tural System is discussed in chapter 6. Analysis and Design of the 50-storey Building with and without outriggers are discussed in chapter 7. Summary, conclusions and future scope of work are included in chapter 8.
URI: http://hdl.handle.net/123456789/1608
Appears in Collections:Dissertation, CL (CASAD)

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