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Abstract This chapter summarizes the work presented in the thesis and concludes the results of it to develop recommendations for future studies according to the Egyptian Codes, ECP-203(2007) and ECP-201(2012) to develop new structural system design provisions. 6.2 Summary This study is mainly concerned with the behavior of braced concrete columns over reinforced concrete shear walls in high-rise buildings which used to resist loading in high-rise buildings and lateral forces from wind and earthquakes instead of using shear wall all over the height of the building. Parametric studies are carried out for six main systems that are modeled in three dimensions as residential buildings with different parameters and geometry. ETABS (v 15.2.2) is used to model and analyze this systems using three dimensional linear analysis. The six systems are studied under the effect of several parameters such as number of stories and the existence of bracing members between columns or just tie beam. Their effect on bending moment values, shear force and normal, as well as story displacement, and inter-story drift are analyzed. Comparisons between the results show the difference between values and the indifference between others values including the percentage of saving. 6.3 Conclusions The main conclusions in this research are presented as follows: 1. Using columns with connecting beams and bracing (Truss system) as a structural system in high rise buildings enhance the general behavior of RC shear walls. 2. The developed finite element models were found to be highly suited for the analysis of high rise buildings, both in case of using solid shear walls, and in case of using the equivalent truss system. 3. The equivalent truss system behavior showed that it is recommended to use this system in the whole building height, and not in a limited number of floors at the building top, in order to avoid high shear force variations at the level where the system changes from “shear wall” to “truss”. 4. Use of a combined system of shear walls, and equivalent trusses in a building was tested, and showed that the “equivalent truss system” carries less moment than the “shear walls”. In addition, the shear force carried by the “truss system” is much less than that carried by the “shear walls”, indicating that the majority of the forces carried by the truss system are carried at the top floors. 5. In practical application in an actual building case, analysis results showed that the transformation of shear walls into an equivalent truss system has the effect of increasing the overall building stiffness, and reducing its total lateral drift at top, when framing action exists in the whole building. 6. Models modified to minimize the above-mentioned framing action showed that the truss system working on its own, without significant framing action in the building is less stiff than the “shear wall” case. It is therefore recommended that replacement of the shear walls by an equivalent truss system should be combined with significant framing action in the building. For every building under design, the two models should be analyzed, and decision to use the equivalent truss system should be based on the amount of saving produced in the overall building cost. 7. Analysis of the actual building was performed using both equivalent static and response spectrum methods. The analysis results showed that both models produced similar results. The replacement of shear walls by equivalent truss systems resulted in an approximately 5% reduction in building weight, which reflected almost exactly in a similar reduction of about 5% in the base shear observed in case of “Equivalent Static” analysis, and “Response Spectrum” analysis. 8. Application of the proposed system showed to an actual case showed an economical advantage. A reduction of 38% of concrete quantities in the shear walls was observed for 20 story building, about 45% for 15 story building, and about 46% for 10 story building. 9. Similar Reduction in steel quantities of about 11%, 19% and 38% for 20, 15, and 10 story buildings were observed respectively. |