Abstract
The requirements for using GFRP bars are growing as several researchers have shown the functionality of bars in concrete columns. The demand to characterize the mechanical properties of GFRP bars is therefore rising, although there is no standardized test method for evaluating the compressive behavior of these bars. This experimental study presents the determination of the mechanical properties of GFRP composite bars in compression, namely the stress-strain curves, compressive strength, ultimate crushing strain, and modulus of elasticity. The compressive properties of these bars were calculated following ASTM D695-10 (Compression Test) with some modifications. A total of 27 specimens were tested for the proposed test procedure. The diameter of the GFRP tendon used in the test was 10, 12, and 14 mm, and the length to bar diameter ratio L e /d b (4, 8, and 16) was investigated for the compressive strength of the bars. These two parameters were used to establish the relationship between the length to diameter ratio and strength. Besides, two steel caps with a length of 50 mm each were installed to both ends of each specimen to avoid premature failure. It was observed that the test method enables to successfully evaluate the compressive characteristics of the GFRP bars. Experimental discussions were performed based on the test results from stress-strain curves, bar graphs, and scatter curves. The results indicate the increase in length to diameter ratio decrease the buckling stress and the compressive to tensile strength ratio for L e /d b ratio of 16 specimens in buckling failure mode. The failure mode transformed from crushing to buckling and a combination of crushing and buckling between the two different failures modes with an improvement in the L e /d b ratio. It shows that there was no yield section on the test specimens during the entire test loading process. The compressive GFRP bars present typical brittle failure. Keywords: Compressive Test, GFRP Bars, Diameter, L e /D b Ratio, Stress-Strain Curve, Buckling DOI: 10.7176/CER/13-5-04 Publication date: August 31 st 2021
Highlights
Corrosion is possibly the biggest civil engineering problem that causes architects, governments, and contractors to spend billions of dollars on the reconstruction of steel-enhanced concrete structures
Three modes of failure such as crushing, buckling, and shearing along with cracking and splitting thread in few specimens was observed in the Glass Fiber Reinforced Polymer (GFRP) bars tested in compression, which were highly influenced by the Le/db ratio for every bar diameter More details of the observed mode of failure are described below: 3.1.1 Crushing failure
This study examines the effect of bar diameter and the effective length to bar diameter ratio (Le/db) on the compressive behavior of GFRP bars
Summary
Corrosion is possibly the biggest civil engineering problem that causes architects, governments, and contractors to spend billions of dollars on the reconstruction of steel-enhanced concrete structures. The use of Fiber Reinforced Polymers (FRP) began in the building industry in the 1970s It was not until the 1990s, that non-metallic bars began replacing steel bars as internal reinforcements in concrete structures. The use of Glass Fiber Reinforced Polymer (GFRP), better known as fiberglass rebar, is a perfect way to fully eliminate the risk of corrosion in building structures. This is an alternative material used in the building industry for steel. The Canadian Guideline for the Design and Construction of Building Structures with FRP [4] requires the use of GFRP bars in concentrically loaded columns where their contribution to the strength of the column is ignored. Recent studies have adjusted the trend of the most recent design guidelines
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