Flexural Strengthening of RC Columns with Low Longitudinal Steel Ratio using GFRP Bars

Mehdi Esfandi Sarafraz

doi:10.1186/s40069-019-0354-z

Abstract

This research describes the results of an experimental work that aimed to investigate the flexural capacity of RC columns with low longitudinal reinforcement ratio that was strengthened with near surface mounted GFRP bars. The experimental program consisted of four square reinforced concrete columns, including one control specimen that were designed with a longitudinal reinforcement ratio below the minimum required ratio of 1% specified by RC design codes. Three of the four specimens were strengthened with different ratios NSM GFRP bar. The specimens were tested under a combined axial compressive load and lateral cyclic displacement to evaluate this retrofit method for the flexural improvement of RC columns. The efficacy of the proposed strengthening method on the flexural capacity, failure modes, hysteretic curves, energy dissipation capacity, and stiffness are discussed on the basis of the test results. The experimental results demonstrated that the contribution of GFRP bars to the flexural capacity of RC columns was significant. Also, an analytical procedure for calculating the bending moment capacity of RC columns strengthened with GFRP bars subjected to axial and lateral is proposed. The model accuracy is demonstrated by comparing the model predictions with the experimental results. The flexural capacity calculated by this method were in good agreement with the experimental results.

Highlights

Reinforced concrete columns are important elements in the structures
3.1 Test Results and Observation The main target in this research was to evaluate the influence of GFRP bars for the flexural strengthening of RC columns with low longitudinal steel rebar ratio, so the response of all specimens due to the low ratio of longitudinal reinforcement was controlled by bending
5 Summary and Conclusions The main idea of this research was to study the use of GFRP bars to modify the flexural capacity of RC columns with low longitudinal reinforcement ratio

Summary

Introduction

Reinforced concrete columns are important elements in the structures. Their damage leads to the failure of the building. Many reinforced concrete columns that were designed and constructed in the last years were designed as gravity columns with minimum longitudinal reinforcement. These columns cannot be able to support sufficient flexural capacity, and they are vulnerable to earthquakes. Reinforced concrete columns can be seismically deficient in the compressive crushing of concrete, shear, reinforcing bar buckling and flexural strength. Flexural capacity defect in RC columns may occur from the low

Objectives

Results

Conclusion