Experimental And Theoretical Study On Seismic Behavior Of Concrete Columns Reinforced With Steel-Basalt FRP Composite Bars And Hybrid Stirrups

Fiber-reinforced polymer(FRP)composite has used widely in civil engineering application due to their superior advantage such as corrosion resistance,a high tensile strength-to-weight ratio,ease of handling and construction,and the wide range of working temperatures.Accordingly,steel-basalt fiber composite bars(SBFCBs)and steel-basalt fiber hybrid stirrups(SBFHSs)it is one of the applications of FRP proposed in this study as innovative hybrid reinforcements.SBFCBs reinforcement made from steel bars with 10 mm diameter and wrapped with BFRP and adhesives with epoxy resin.In addition,the SBFHSs made from steel wire with a diameter of 4 mm wrapped with BFRP and epoxy resin and used as transverse reinforcement.Moreover,ten RC bridge columns were casted and reinforced with SBFCB and SBFHS reinforcement and divided into three groups as the following:Group(A)consisted of four RC column,where three columns of this group were reinforced longitudinally with SBFCB with post-yield stiffness of(0.1,0.3,and 0.5)and transversely with SBFHS stirrup.In addition,the last column of this group is referred as a reference column which was reinforced longitudinally and transversely with ordinary steel bars.Furthermore,several parameters affecting the columns’responses,such as the BFRP reinforcement ratio and the ratio between the post-yield and elastic stiffness of the longitudinal bars,were examined.The results of this group showed that the failures of all four columns were flexural,and the post-yield stiffness of the longitudinal reinforcement had a significant effect on the stiffness,bearing capacity,residual deformation,and amount of energy dissipated by the test columns.Group(B)composed of two columns reinforced longitudinally with SBFCB with post-yield stiffness of 0.3 and transversely with SBFHS stirrup and tested under effect of axial and lateral cyclic load.The main purpose of these columns is to study the bond between concrete and SBFCB bars.Group(C)composed of four columns,where two columns were reinforced longitudinally with SBFCB with post-yield stiffness of 0.3 and transversely with SBFHS stirrup,and other two columns were reinforced with ordinary steel bars.These columns have taken to study the durability of SBFCB and SBFHS under sea water effect(future work).On the other hand,an experimental study was conducted on the confined effects of SBFHS stirrup on the compressive behavior of concrete cylinders.Twenty-one cylinders were reinforced spirally with SBFHSs and tested under axial compressive loading.Different parameter was investigated include steel-wire/BFRP ratio,SBFHS diameter and stirrup volume ratio.In this study an analytical equation was developed for use to predict the stress-strain curves of SBFHS confined concrete.In addition,numerical study was conducted to investigate the cyclic behavior of concrete columns reinforced with SBFCB and SBFHS reinforcements using OpenSees program.The obtained results was compared with experimental values above mentioned.Structure of the thesisThis dissertation is composed of seven chapters covering the development of SBFCB and SBFHS reinforcement with their applications,experimental program,material models,and analysis procedures.The content of these chapters is as follows:Chapter 1:This chapter provides a literature review concerning of fiber reinforced polymer.A historical review which deals with the previous work on SFCB mechanical properties.Chapter 2:This chapter presents the theoretical investigation of proposed study.The purpose of this chapter is to present a design methodologies available for the concrete columns reinforced with SBFCB bars and SBFHS stirrups to predict the columns capacity according to design codes and guidelines-Other parameters such as reinforcement ratio of columns constructed in seismic zones,displacement ductility,shear,strength and curvature of the column was investigated theoretically.Also investigated the seismic performance includes viscous damping ratio energy dissipation.Comparisons between the experimental test results and the theoretical predictions by ACI guidelines are performed.Chapter 3:This chapter describes the experimental study on the confined effects of concrete cylinder reinforced with Steel-Basalt Fiber Hybrid Stirrup(SBFHS)under the compressive behavior.SBFHS is a kind of new innovative stirrup made up of externally basalt fiber reinforced polymer and hybrid with inner steel wire and epoxy resin.Where is characterized by high strength,and good anti-corrosion performance.In this chapter twenty-one of specimens was investigated experimentally,and comparisons were conducted on the load versus displacement and stress with strain and failure mechanism.Moreover,the author conducted an analytical study to develop equations to predicting the stress-strain of confined concrete with SBFHS.Research findings indicate the decrease of spiral spaces enhanced the ductility and concrete core strength of cylinders reinforced with SBFHS.Chapter 4:This chapter presents the first paper in this dissertation which accepted in ASCE’s Journal of Composites for Construction.The paper is titled-Experimental Study of the Cyclic Behavior of Concrete Bridge Columns Reinforced by Steel-Basalt Fiber Composite Bars and Hybrid Stirrups.This paper shows the experimental test results investigation on the cyclic behavior of four large scale circular concrete columns reinforced with SBFCB bars and SBFHS stirrups.The analysis of the results and discussions are presented.These discussions are based on cyclic behavior,effect of various values of post-yield stiffness of(0.1,0.3 and 0.5)of SBFCB on the behavior of RC columns,force-displacement response,and residual deformation and curvature of tested specimens.In addition,the investigation of seismic measurements,such as energy dissipation,stiffness degradation,and viscous damping ratio were conducted.Chapter 5:This chapter presents Bond-based study on concrete columns reinforced by hybrid bars and stirrups under cyclic loading.The study aims to investigate the bond behavior of three circular concrete columns reinforced with SBFCB bars and SBFHS stirrups.Where one column was utilized as a reference,and other two columns were equipped with un-bonded lengths of 150 mm and 300 mm,covering the plastic hinge region above the column base were considered as a parameters study.The results were presented in terms of strength and ductility,force-displacement responses,residual displacement,curvature,force-strain relationship,and seismic measurements.Comparisons between the experimental test results and the analytical predictions by OpenSees program are performed.Based on this study,the theoretical and test results showed significant correlation between SBFCB,SBFHS and concrete.Chapter 6:This chapter presents the theoretical investigation of this dissertation.Entitle a numerical study on concrete columns reinforced with steel basalt fiber composite bars and stirrups.The Open System for an Earthquake Engineering Simulation(OpenSees)program was used in this study to analysis the proposed parameters.Through this study,various parameters have been investigated includes post-yield stiffness and bond-slip.The result of the numerical study was compared with experimental results such as force-displacement,stiffness degradation,viscous damping,and energy dissipation.Chapter 7:This chapter presents a summary of this investigation and the overall conclusions based on the experimental and theoretical results conducted in this dissertation.In addition,recommendations for further research work are also given.