ارزيابي طول مهار موثر ورق تقويتي FRP بر سطح بتن بر اساس آناليز ميدان كرنش به روش سرعت سنجي تصويري ذرات ﴿PIV﴾

چكيده انگليسي :

Evaluation of FRP to Concrete Effective Bond Length by Strain Analysis Using Particle Image Velocimetry PIV Ardalan Hosseini a hosseini@cv iut ac ir December 19 2012 Department of Civil Engineering Isfahan University of Technology IUT Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisor Dr Davood Mostofinejad Prof Email address dmostofi@cc iut ac ir Abstract Strengthening or retrofitting of existing reinforced concrete RC structures may be performed to provide higher design load resistance increase stiffness or correct strength loss due to deterioration During the last decade an increase in the application of fiber reinforced polymers FRPs has been observed in all engineering branches due to certain advantages of the material including high tensile strength light weight corrosion resistance and ease of application The aforementioned benefits of FRP composites have led engineers and researchers all over the world to utilize FRPs as alternative to conventional strengthening material i e steel for strengthening of RC members The most common technique for flexural shear strengthening of RC beams and slabs utilizing FRP materials is externally bonded reinforcement EBR technique Despite certain benefits of EBR technique such as simple and rapid installation the main problem which has greatly hampered the use of EBR technique is premature debonding of FRP composite from the beam substrate In this case FRP to concrete bond behavior is a key factor controlling debonding failures in FRP strengthened members On the other hand a very important aspect of the FRP to concrete bond behavior is that there exists an effective bond length beyond which an extension of the bond length cannot increase the ultimate load Due to importance of the bond behavior of FRP to concrete bonded joints especially FRP to concrete effective bond length the main intention of the current study is to experimentally evaluate the effective bond length of externally bonded FRP reinforcements by means of single shear bond tests To do so 30 concrete prisms with dimensions of 150 150 350 mm were cast and CFRP sheets having different bond length were adhered to 22 concrete specimens using conventional EBR technique and the other 8 specimens were strengthened using grooving method GM Afterwards all strengthened specimens were subjected to single shear bond test using a 300 kN hydraulic jack specially designed at Isfahan University of Technology IUT In order to benefit from full field deformation measurements a non contact image based technique i e particle image velocimetry PIV was used to investigate the bond behavior of tested specimens Moreover numerous validation experiments were conducted to verify the ability of PIV technique in precise deformation measurements by means of four point flexural tests on steel and RC beam specimens Comparison of experimental results of the current study with the existing models of effective bond length shows the incapability of the existing guideline models in accurate predictions of FRP to concrete effective bond length ACI 440 2R and fib 14 overestimate the effective bond length by a mean error of 100 percent In the other hand due to high stiffness bond of FRP to concrete when using GM all GM specimens failed due to CFRP rupture regardless of grooves length Consequently experimental results of the current study strongly verified the capability of GM for eliminating premature debonding failure Keywords FRP composites debonding single shear test FRP to concrete effective bond length externally bonded reinforcement EBR grooving method GM particle image velocimetry PIV

حسيني، اردلان

ارزيابي طول مهار موثر ورق تقويتي FRP بر سطح بتن بر اساس آناليز ميدان كرنش به روش سرعت سنجي تصويري ذرات ﴿PIV﴾

كامپوزيت هاي FRP , جدا شدگي , آزمايش برش مستقيم , روش نصب خارجي ﴿EBR﴾ , شيار زني ﴿GM﴾