International Journal of Engineering Research and Reviews
ISSN 2348-697X (Online) Vol. 8, Issue 3, pp: (19-28), Month: July - September 2020, Available at: www.researchpublish.com
Strengthening of Circular Reinforced Concrete Columns with Steel Fiber Added to the Mix after Fire Exposure Nasr Z. Hassan1, Mostafa A. Osman2, Doaa Y. Mohammed3 1
Associate Professor, Civil Eng. Dept., Helwan University, Cairo, Egypt
2
Associate Professor, Civil Eng. Dept., Helwan University, Cairo, Egypt
3
Teaching Assistance, Civil Eng. Dept., Helwan University, Cairo, Egypt
Abstract: Columns are considered one of the most important structural elements in buildings; they transfer the load directly to the foundations. thus, their exposure to any variables or any extreme conditions such as fire may cause the collapse of the building as a result of buckling of columns. The main objectives of this research are to investigate the effect of using the steel fiber reinforcing polymer on the strengthening of circular R.C Columns after exposure to fire. In the experimental program, the volume fraction of steel fiber, strengthening FRP area and method of Strengthening using FRP on the specimens varied in order to determine the effect of these variables on the specimen strength and axial displacement. The experimental program consists of ten reinforced concrete short columns. A column was tested as a control column without steel fiber and without fire, nine columns with different percentages of steel fiber in the mix (0, 0.5%, 1.0%, and 1.5%) by weight, three specimens of the nine were tested only without fire, and six specimens were exposed to fire. then the columns were strengthened with glass fiber with strip of width (100mm, 200mm) respectively. Experimental results indicated that adding steel fiber by different volume fractions increased the load carrying capacity of the reinforced concrete columns. Keywords: FRP, axial displacement, steel fiber.
I. INTRODUCTION The proposed technique of using steel fiber reinforced concrete reduces the manufacture and labor cost that is typically associated with conventional methods. Steel fiber reinforced concrete (SFRC) is used to reduce the problems occurring in concrete such as the weakness of concrete strength at the tension zone. Strengthening of concrete structural members like Columns may be required on many cases such as Deterioration of structure due to environmental effect damage caused by accidents, upgrading loading requirements, revision in loading standards, and seismic retrofitting. This research also includes a study of the effect of each variable on crack patterns, failure shape, load - deformation curves, steel strains, the stiffness, the ductility and energy absorption. From all these parameters a suggestion can be made to strengthen reinforced concrete columns after being exposed to fire.
II. EXPERIMENTAL PROGRAM The experimental study herein tested ten reinforced concrete columns divided into four groups O, A, B and C. all specimens have same dimensions cross section, the cross section is circular section with dimensions 200 mm Diameter and 1250 mm Height. All columns have constant reinforcement. The longitudinal reinforced was 6Ф12 (grade 36/52) and 5Ø8 / m’ was used (grade 24/35) as separate stirrups in transverse direction show in Figure (1).
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