الفهرس 
CHAPTER (1): INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In this research, many important issues relevant to the structural design of
reinforced concrete tall building have been studied. At the first of all, the structural
engineer has to be aware which analysis method should be used to achieve the
optimization of structural analysis. For this purpose, chapter (3) of the research has
focused on a comparison between the most commonly two methods for seismic
analysis namely, equivalent static method and elastic response spectrum method.
Because most design codes don’t recommend the use of the first method if the
height of the building reaches a certain value, seven levels of heights for a shear
wall system started by 5 stories then, the number of stories is gradually increased
to be (10, 14, 17, 20 , 24 and 30) stories have been modeled using software
packages ETABS. All of these cases have been analyzed by the aforementioned
two methods, which adjusted according to ECP 2012, EC8: 2004 and UBC 1997.
For the aim of comparison, the results of drift at top in addition to the values of
overturning moments at base were tabulated versus each height and code. The
obtained results showed that the implementation of equivalent static method would
be accompanied by uneconomic design for medium to high-rise buildings where it
would be convenient for seismic analysis of low-rise buildings.
The second problem that faces the structural designers is how to select the most suitable structural system that serves both architectural and structural conditions. Therefore, a large portion of the present study has focused on a comparison between the efficiency of the most commonly structural systems that usable for reinforced concrete tall buildings such as framing system, shear wall system, wall frame system, tubular column system, tubular frame system and bundled frame
Chapter (6)
tubes system. A proposal configuration for each structural system has been presented in chapter (4) for 30-storey reinforced concrete building. All systems have been examined for sustaining the same lateral load, which represented by both seismic and wind loads. Seismic analysis has been performed in two different forms namely, the elastic response spectrum and the linear time history analysis. The elastic response spectrum analyses have been performed according to ECP 2012, EC8: 2004, IBC 2012 and UBC 1997 while linear time history analysis has been performed according to the old records of elcentro earthquake record 1940. On the other hand, wind load analysis has been performed according to ECP 2012.
The six systems have been modeled and analyzed on ETABS. Then, the results of drift at top in addition to the values of overturning moments at base resisted by each system excluding its central core have been obtained and tabulated for each case and code for the aim of comparison. The systems have been arranged in descending order according to the values of drift at top and overturning moments. The results showed that the most efficient system in sustaining lateral loads is bundled frame tubes while the least efficient system was framing system. These results are coincided with those from the old researches relevant to our study, which summarized in chapter (2) of the research.
If the architectural constraints forced the structural designer to use insufficient stiffened system, the designer has to stiffen the existed system by any way. Such a common way to impart stiffness in the structure is to use outrigger or belt truss or using together instantaneously. However, to achieve the optimal use of outrigger, it is very important to employ it in the optimum position through the building height. Therefore, chapter (5) of the research concentrated on two important issues, the first issue concerns about determining the optimum position of outrigger while, the second one discusses the efficiency of outrigger system for sustaining earthquake and wind loads in comparison with the previous six systems. Moreover, construction cost comparison is adopted for the seven systems.
Chapter (6)
Regarding the first issue, a parametric study has been done to determine the optimum location of outrigger. Whereas, many different positions for single and two-outriggers have been randomly selected, modeled and analyzed by ETABS for the same response spectrum, which defined according to ECP 2012, EC8: 2004, IBC 2012 and UBC 1997 in addition to linear time history analysis according to the records of elcentro 1940. The results of drift at top and the periodic time of the first mode shape are obtained and tabulated versus each case to determine the optimum position. The results showed that the optimum location for single outrigger in 30-storey building is at the seventeenth floor or equal 0.455H measured from the top. Moreover, the optimum location for two outriggers in 30-storey building was one in the tenth floor and the second in twentieth floor or 0.33H and 0.67H. These conclusions are found identical with those from the hand calculations that presented in the head of this chapter. Since the number of outriggers is always found, divide the height into equal parts so the optimum positions for three outriggers are concluded 0.25H, 0.50H and 0.75H in addition; the optimum position for four outriggers is 0.2H, 0.4H, 0.6H and 0.8H.
The second issue was drift and cost comparisons between the aforementioned six structural systems including another one namely “outrigger system” which represented by frame system or bundled frame tubes with single outrigger placed at the 17PthP floor for each one. Drift comparison was performed based upon the results of drift at top for both seismic and wind analysis cases, which performed in chapter (4) while cost comparison was performed, based upon the self-weight of the structural system per unit area. The objective of both comparisons is to determine the most economical system amongst the presented ones.
The results showed that using outrigger system is always accompanied by a great effect in improving the lateral stiffness especially in very week system whereas, using outrigger in the 17PthP floor with framing system makes it stronger than the frame system, shear wall system, wall frame system and tubular columns systems.
It is also observed that using outrigger with strong systems like S6 is always accompanied by slight improvement in lateral stiffness.
The conclusions from the above work and the suggested recommendations for the future works are summarized.