Chidananda S. H, Khadiranaikar R. B., International Journal of Advance Research, Ideas and Innovations in Technology. 1.

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1 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in ISSN: X Impact actor: (Volume3, Issue5) Available online at Flexural Behaviour o Concrete Beams Reinorced With GFRP Rebars Chidananda S. H Basavesvar Engineering College (Autonomous), Karnataka c.nanda143@gmail.com R. B. Khadiranaikar Basavesvar Engineering College (Autonomous), Karnataka dr.rbknaikar@ .com Abstract: This study reports test results o 12 concrete beams measuring 0mm wide 180mm deep 1200mm long reinorced with glass iber-reinorced polymer (GFRP) bars subjected to a our-point loading system. The test specimens were classiied into three groups according to the concrete compressive strength. The main variation done or each beam in all the three groups was a percentage o reinorcement (0.5%, 1%, 1.5% and 2%). Since all the beams were over reinorced ailure occurred due to rupture o concrete at compression zone. The ailure is initiated by a vertical crack at the midspan which extended up to compression zone o the beam and propagated horizontally which leads to bond ailure between top concrete and compression reinorcement. The test results revealed that the crack widths and mid-span delection signiicantly reduced by increasing the reinorcement ratio. The ultimate load increased by 7.5%, 16.8%, 27.7% as the reinorcement percentage increased rom 0.5% to 1%, 1.55 and 2% respectively. The lexural provisions o structural design guidelines namely 440.1R-06, , and S were evaluated against the test data R-06 overestimates the moment resistance o GFRP bars as compared to other codes and experimental results. Whereas all the design guidelines predict nearly the same values or delection. And or crack width approximation Toutanji s equation is more accurate compared to equation. Keywords: GFRP Rebar, Flexural Behaviour, Reinorcement Ratio. 1. INTRODUCTION 1.1 General One o the biggest challenges engineers today acing is the problem o ageing inrastructure, particularly with respect to reinorced cement concrete. The major cause o deterioration o reinorced concrete structures is corrosion o the reinorcing steel. Among others, one viable option is to reinorce concrete with rebars o glass iber-reinorced polymer (GFRP), a noncorrosive material. GFRP reinorcing bars are made primarily o glass ibers. Being non-corrosive, GFRP bars can help extend the liecycle o reinorced concrete structures substantially, as well as reduce their maintenance, repair, and replacement costs. While GFRP is becoming a viable reinorcement alternative, it presents design challenges which are dierent than those in the design o conventional steel reinorced concrete. One important challenge is consideration o a brittle ailure mode in GFRP-reinorced members. Other than the brittle ailure mode, the major shortcoming o GFRP reinorcing bars is their relatively low stiness, when compared to steel. This reduced stiness, combined with other actors such as dierent bond behaviour and lower tension stiening, results in delections that are larger than conventional steel-reinorced beams, at any load stage. Because o these large delections, designs may oten be governed by delection limitations. As such, it is critical that load-delection behaviour can be accurately predicted. 1.2 Objectives The undamental objective o the present study is to investigate the lexural behaviour o GFRP reinorced concrete beams, with a ocus on critically evaluating current design code provisions relating to design with GFRP. The design codes discussed are S (Canadian standards or Design and Construction o Building Structures with Fiber-Reinorced Polymers), (Egyptian guidelines or the use o FRP in the civil construction), and 440.1R-06 (American standards or the Design and Construction o Structural Concrete Reinorced with FRP Bars). 2017, All Rights Reserved Page 119

2 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in 2 EXPERIMENTAL WORK The current research program was carried out to investigate the lexural behavior o concrete beams reinorced with longitudinal GFRP bars (top and bottom). The eects o both concrete grade and the increase in reinorcement ratio on the lexural behavior o the tested beams were studied. 2.1 Test specimen and setup The test program consists o 12 beams split into three main series each o our beams cast with M50, M60, and M70 grades o concrete respectively. The main variation is a percentage o reinorcement ratio. Four dierent reinorcement ratios namely 0.5%, 1.0%, 1.5%, and 2.0% are used to access the lexure behaviour o test specimens strengthened with GFRP bars. The test specimens are named in a series A-B in which irst letter A represents its grade o concrete and the second letter denotes its percentage o reinorcement. For example, in which 50 represents the grade o concrete used in that beam is M50, and it is reinorced with GFRP bars equal to 0.5% o its cross section. The schematic representations o longitudinal as well as transverse reinorcement are shown in Figure 1 and Figure 2. The lexural test setup o GFRP-RC beams under two point loads consisted o placing the specimens between two simple supports with an eective span o 1060mm. Two point loads were applied at a distance 367mm rom both the supports. An upper spreader beam was placed above the point loads to equally distribute the concentrated load rom the machine. During testing, cracks have been marked, delections are measured, and the corresponding loads were noted to observe the behaviour o the beam at various load increments. Sequence, pattern, and width o the cracks until ailure were also examined. The loading coniguration or lexure test has been shown in Figure 3; Figure 1: Detailing o longitudinal and transverse reinorcement Figure 2: Cross sections with varying percentage o reinorcement 2017, All Rights Reserved Page 120

3 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in Figure 3: Loading coniguration or Flexure test 2.2 Test results This section presents the experimental results rom the twelve specimens and is split into two main sections, based on the grade o concrete and reinorcement ratio. The section based on the grade o concrete discusses and compares the results between three dierent grades and the section based on reinorcement ratio deals with the results o beams with dierent reinorcement ratios. Table 1: Results o test specimens reinorced with GFRP bars Specimen ck(mpa) ρ(%) Mexp Δexp Wexp Ultimate load or beams o M50 grade concrete reinorced with 0.5%, 1.0%, 1.5%, 2% are 92kn, 97kN, 101kn and 110kN respectively. And delections in beams were 24.5mm, 21.3mm, 19.6mm and.8mm or varying percentages o GFRP reinorcement. And also crack widths reduced by 36.28%, 43.36% and 54% reinorcement ratio increased rom 0.5% to 1%, 1.5% and 25 respectively. For M60 grade concrete as the reinorcement ratio increased rom 0.5% to 1.0%, 1.5% and 2.0% the ultimate load increased by 11.4%, 18.1%, 24.8% and the delections reduced by.91%, 29.17%, 39% respectively. And there was a tremendous reduction in crack widths i.e crack widths reduced by 46.67%, 66.67% and 72.72% as the percentage o GFRP reinorcement is increased. Compared to M50 and M60 grade concretes M70 concrete exhibited greater load carrying capacity as well as lower deormations. Crack widths reduced by 46.37%, 66.5% and 72.06% or an increment in reinorcement ratio rom 0.5% to 1.0%, 1.5%, 2.0% respectively. 3. RESULTS AND DISCUSSION The ollowing discussion ocuses on comparing the experimental results presented in Chapter 5 with the behaviour predicted by using current design codes and guidelines. The documents discussed are design codes S and , and the report 440.1R-06 with the ocus being placed on the moment resistance, delection, and cracking behaviour. 2017, All Rights Reserved Page 121

4 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in 3.1 Moment resistance 440.1R-06 Provisions: As per 440.1R-06 design guidelines the moment resistance capacities o the beams are calculated using the ollowing equation and the results are tabulated in table 6.1. a M n A d Provisions: According to design guidelines o the moment resistance o the beams reinorced with varying percentages o GFRP rebars are computed using the equation given below. The results o moment resistance are presented in table 6.1. M u A * e a d 2 S Provisions: According to S the ultimate limit moment or an over reinorced beam can be calculated using the ollowing equation with top concrete strain constant which is equal to (ε c = ). And the results are tabulated in table 6.1. M r c Td A 2 1 d 2 1 c Moment Resistance (kn - m) Reinorcement Table 2 compares the experimentally obtained results with predicted results by considering various design guidelines. The above igures indicate that For the higher volume o reinorcement the equation and S equation both perorm well or moment resistance capacity o the beams strengthened with GFRP bars. In all the three cases 440.1R-06 provisions have overestimated the moment resistance capacity o GFRP reinorced beams as compared to other two design guidelines. For the same elastic properties, cross sections, and percentage o reinorcement guidelines predicts higher results than experimentally obtained results. Whereas and guidelines predicts lower values o moment resistance capacity than the experimentally obtained results. The experimentally obtained results or beams strengthened with GFRP rebars well agree with the results o other authors. This indicates that guidelines have overestimated the strength o GFRP rebars and on the other hand and have underestimated the strength o GFRP rebars. Table 2: Moment Resistance o Test Specimens. Specimen MEXP M M M M M M M M M M M M , All Rights Reserved Page 122

5 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in M M M (a) Moment Resistance (kn - m) Reinorcement (b) 40 Moment Resistance (kn - m) (c) Reinorcement Figure 3: Comparison between experimental and predicted results o moment resistance or a) M50, b) M60 and c) M70 grade concrete reinorced with GFRP bars 3.2 Delection Beams with more reinorcement than balanced ( ) are deined as over reinorced and ail by crushing o concrete at the b top surace. Because the majority o beams designed in practice are over-reinorced, all the twelve beams presented here were designed in such a manner. The design process or an over-reinorced beam involves supplying more reinorcement than that o calculated. 2017, All Rights Reserved Page 123

6 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in Delection (mm) Reinorcement 440.1R-06 Provisions: As per 440.1R-06 design guidelines the midspan delection o the beams are calculated using the ollowing equation and the results or all the beams are tabulated in table 6.2. Pa 2 2 3L 4a 48E I c e Provisions: According to design guidelines o the midspan delections o the beams reinorced with varying percentages o GFRP rebars are computed using the equation given below. The results o delection are presented in table PL 48E c I e S Provisions: Delection procedure according to S states that the delection shall be calculated by ormulae based on the integration o curvature at sections along the span. The equation applicable to the test setup adopted in this experimental investigation is given below. And the results or the same are presented Table PL a a Lg EcI cr L L L Table 3: Mid-span delections o test specimens. 3 Specimen ΔEXP Δ Δ Δ T M M M M M M M M M M M M , All Rights Reserved Page 124

7 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in (a) Delection (mm) Reinorcement (b) Delection (mm) Reinorcement (c) Figure 4: Comparison between experimental and predicted results o midspan delection or a) M50, b) M60 and c) M70 grade concrete reinorced with GFRP bars Table 3 shows that, or all twelve beams, the current code provisions under predict ultimate midspan delection. Underprediction o delection is undesirable, particularly at service levels. The cause o this discrepancy can be seen in Figure 4(a), Figure 4(b) and Figure 4(c), which compare the predicted midspan delection behaviour to the experimental behaviour o beams o dierent grades o concrete strengthened with dierent percentages o GFRP bars. The above igures indicate that, beyond cracking, the three methods do not provide signiicantly dierent results. The igure also shows that the major cause o the discrepancy between the predicted and experimental results can be attributed to an underprediction o cracked stiness (or the dierence in slopes postcracking). The results above indicate that the described delection prediction methods do not accurately predict ultimate delection or this test series. All the three methods predict an ultimate delection o approximately 60% o the experimental results. 3.3 Crack widths Code Equations: As per 440.1R-06 provisions, the maximum crack width at any given load can be computed using the ollowing equation. And the results or all the beams are presented in table 6.3. w 2 2 s 2 kb d E 2 Toutanji s Equation: For predicting the maximum crack widths in GFRP-RC beams Tountanji recommended the ollowing equation. And the crack widths or test beams are tabulated in table , All Rights Reserved Page 125

8 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in 0.5 w dc Act E Figure 5(a) and Figure 5(b) indicates that or beams that are over-reinorced Toutanji s model predicts maximum crack width more accurately than the current code provisions. The Tountanji s model is slightly more accurate than code or overreinorced beams in this test series. This analysis does not take into account long-term eects such as creep, which may be signiicant in GFRP reinorced beams. Further research is needed in the area o cracks in order to ully understand the crack development. Table 4: Crack widths o test specimens Specimen WEXP W WTOUTANJI M M M M M M M M M M M M TOUTANJI 1.5 Crack Width (mm) (a) 0.3 Reinorcement 2017, All Rights Reserved Page 126

9 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in 1.8 TOUTANJI 1.5 Crack Width (mm) (b) Reinorcement 2.1 TOUTANJI 1.8 Crack Width (mm) (c) Reinorcement Figure 4: Comparison between experimental and predicted results o crack widths or a) M50, b) M60 and c) M70 grade concrete reinorced with GFRP bars CONCLUSIONS The ollowing conclusions have been drawn rom the current study. At the earliest stages o research into glass-iber reinorced polymer reinorcing bars, it was recognized that this material has a large potential or use in concrete structures, to be suitable as a reinorcing material, design equations must account or such properties as low stiness and brittle ailure mode. As early as 1970 s, it was understood that the lexural behaviour o GFRP reinorced concrete beams could be predicted using equations developed or steel reinorced beams, particularly with respect to moment resistance. Since that era, both the mechanical properties o GFRP bars and the understanding o their behaviour have signiicantly improved. It is recognized, or instance, that the use o GFRP bars results in signiicantly less tension stiening eects than steel bars. Due to this, and other phenomena, modiications to the steel-reinorced concrete equations must be made in order to accurately predict the unique behaviour o GFRP-reinorced concrete in lexure. Increment in percentage o reinorcement ratio rom 0.5% to 1%, 1.5%, 2% causes reduction i crack widths by 46.67%, 66.67% and 72.72% and delection by.91%, 29.17%, 39% respectively. Both increasing grades o concrete and percentage o reinorcement tend to increase the moment resistance o beans reinorced with GFRP bars. From the current study, it can be concluded that the 440.1R-06 provisions overestimate the moment resistance compared to , S as well as experimentally obtained results underssssestimates both moment resistance and delection behaviour o GFRP reinorced beams compared experimentally obtained results and other provisions. 2017, All Rights Reserved Page 127

10 Chidananda S. H, Khadiranaikar R. B., International Journal o Advance Research, Ideas and Innovations in The Tountanji s model is slightly more accurate than code or over-reinorced beams in this test series. This analysis does not take into account long-term eects such as creep, which may be signiicant in GFRP reinorced beams. REFERENCES 1. Abdelmonem Masmoudi, Mongi Ben Ouezdou, Jamel Bouaziz. New parameter design o GFRP RC beams Journal o ASCE Construction and Building Materials 29 (2012) Alsayed S. H. Flexural Behaviour o Concrete Beams Reinorced with GFRP Bars Journal o ASCE Cement and Concrete Composites 20 (1998) l Ashour A. F. Flexural and shear capacities o concrete beams reinorced with GFRP bars Journal o ASCE Construction and Building Materials 20 (2006) Biswarup Saikia, Phanindra Kumar, Job Thomas, K.S. Nanjunda Rao, Ananth Ramaswamy. Strength and serviceability perormance o beams reinorced with GFRP bars in lexure Journal o ASCE Construction and Building Materials 21 (2007) Maher A. Adam, Mohamed Said, Ahmed A. Mahmoud, Ali S. Shanour. Analytical and experimental lexural behavior o concrete beams reinorced with glass iber reinorced polymers bars Journal o ASCE Construction and Building Materials 84 (20) Iman Chitsazan, Mohsen Kobraei, Mohd Zamin Jumaat and Payam Shaigh. An experimental study on the lexural behavior o FRP RC beams and a comparison o the ultimate moment capacity with Journal o ISSN Civil Engineering and Construction Technology, Vol. 1(2), (2010) M. Goldston, A. Remennikov, M. Neaz Sheikh. al investigation o the behaviour o concrete beams reinorced with GFRP bars under static and impact loading Journal o ASCE Engineering Structures 113 (2016) Toutanji, H.A, Saai M. Flexural Behavior o Concrete Beams Reinorced with Glass Fiber-Reinorced Polymer (GFRP) Bars, Structural Journal, Vol. 97, No.5, (2000). 9. Vijay P.V, Gangarao, H.V.S. Bending Behavior and Deormability o Glass Fiber- Reinorced Polymer Reinorced Concrete Members, Structural Journal, Vol. 98, No. 6, (2001). 10. Faza S. S, GangaRao H. V. S. (1992). Pre- and post-cracking delection behavior o concrete beams reinorced with iber-reinorced plastic rebars, Advanced Composite Materials in Bridges & Structures, The Canadian Society or Civil Engineering. Montreal, Canada. (1992) Ashour, A. F., Habeeb, M. N. Flexural behavior o continuous GFRP reinorced concrete beams, Journal o Composites or Construction, ASCE. Vol. 12, No. 2, (2008) Masmoudi, R., Theriault, M., Benmokrane, B. (1998), Flexural Behavior o Concrete Beams Reinorced with Deormed Fiber Reinorced Polymer Reinorcing Rods Structural Journal, Vol. 95, No. 6, Fu, D., Wen, Y., Wang, B. al study on the lexural deormation behavior o concrete beams reinorced with GFRP bars Advanced Materials Research, Vol. 280, (2011) CODES AND STANDARDS 1. American Concrete Institute Guide or the design and construction o concrete reinorced with FRP bars, 440.1R- 06, American Concrete Institute, Farmington Hills, Mi. (2006). 2. Canadian Standards Association. Concrete Design Handbook, A , Mississauga (2004). 3. Canadian Standards Association. Design and Construction o Building Components with Fiber Reinorced Polymers S806-12, Mississauga (2012). 4. Egyptian Code o Practice. The use o Fiber Reinorced Polymer (FRP) In the construction ields Egyptian Standing Code Committee (2005). 2017, All Rights Reserved Page 128