International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 2, Issue 2, pp: (24-34), Month: October 2014 - March 2015, Available at: www.researchpublish.com Page | 24 Research Publish Journals A Comparative Study of Seismic Strengthening of RC Buildings by Steel Bracings and Concrete Shear walls Yaseer Alashkar 1 , Sohaib Nazar 2 , Mohammad Ahmed 3 1 Associate Professor, College of Engineering, Zagazig University, Zagazig, Egypt 2 Lecturer Colleges of Engineering, King Khalid University Abha, KSA 3 Lecturer College of Engineering, King Khalid University, PhD Candidate Cairo University, Egypt Abstract: Shear wall and Steel bracing systems are most widely used in medium to high rise buildings to provide stiffness, strength and energy dissipation required to resist lateral load imposed by earthquakes and wind. In the past shear wall and steel bracing have been proved as most feasible solution for seismic retrofitting or strengthening of buildings. The newly adopted performance evaluation methodology and capacity design principles are examples of these important advancements in seismic engineering. Many existing RC buildings need to retrofit to overcome weaknesses to resist seismic loads. Therefore, there is an essential need to upgrade the seismic performance of existing RC buildings so that they can meet the requirements of the new performance- based seismic design techniques. In this paper, seismic performance of RC building rehabilitated with shear wall and concentrated steel bracing. An earthquake load is calculated and applied on nine stories building located in zone III. A comparison has been made between the effectiveness of different types of steel bracings with concrete shear wall at different locations of the building. The performance of the building is evaluated in terms of story drifts, lateral displacements, bending moments and base shear. Keywords: Retrofit, Seismic Strengthening, Steel bracings, Shear walls. I. INTRODUCTION In the past thirty years moderate to severe earthquakes have occurred in world at intervals of 5 to 10 years caused severe damages and suffering to humans by collapsing the structure, tsunamis, floods, landslides in loose slopes and liquefaction of sandy soils. Socio-economic losses have been increased significantly in the world due to establishment of new cities in earthquake prone areas. However, these developments in construction have not been followed by guidelines of seismic codes in the past. Existing RC buildings designed without considering seismic criteria and ductile detailing may undergo severe damage during earthquake ground motion. The effect of horizontal forces due to wind loads, earthquake loads and blast loads etc. are attaining increasing importance. Strengthening of buildings have been proved as more economical and viable immediate shelter solution rather than replacement of buildings [1]. Reinforced concrete shear walls have been used as most effective solution to provide resistance and stiffening to the buildings against the lateral loads imposed by the earthquakes and wind. Moreover these walls also provide sufficient ductility and lateral control drift in order to minimize the strong lateral load effect especially during earthquake. The use steel bracing is also an effective solution for retrofitting and strengthening of seismically inadequate reinforced concrete frame structure [5, 6, 7]. It is highly efficient and economical method to increase the lateral resistant capacity of the building by increasing its lateral stiffness [8]. In the present study, an existing eight story RC frame structure building has been analyzed, retrofitted with concrete shear wall and steel bracing provided at the boundary and core of the building. SAP2000 (V.14.2) has been used [2]. A