معرفي روش مهارهاي تار و پودي ﴿WWS﴾ و مقايسه ي آن با ديگر روش هاي متداول جهت تقويت تيرهاي بتني با FRP

چكيده انگليسي :

Warp and woof strap WWS method for strengthening of concrete beams with FRP sheets and comparison with other conventional methods Mohsen Diari m dyaribidgoli@cv iut ac ir July 8 2013 Department of Civil Engineering Isfahan University of Technology IUT Isfahan 84156 83111 Iran Degree M Sc Language Persian Supervisors Dr Davood Mostofinejad Prof Email address dmostofi@cc iut ac ir Dr Mohamad Reza Eftekhar Assist Prof mreftekhar@cc iut ac ir Abstract Fiber Reinforced Polymer FRP composites are widely accepted as a promising and easy to use construction materials especially for strengthening purposes due to the numerous advantages such as high tensile strength ease of application light weight and corrosion resistance One of the most common methods for flexural strengthening of concrete beams with FRP materials is the Externally Bonded Reinforcement EBR method The main problem that has greatly hampered the use of EBR method is the premature debonding of FRP laminate from the beam substrate This will shorten the expected lifespan of the reinforced membrane and makes EBR method uneconomical Surface preparation of concrete before attaching FRP sheets is considered as a suitable method to postpone debonding in EBR technique but with limited effects One of the methods is using U shaped straps at the both ends or throughout the beam Conventional U shaped straps can increase flexural strength of reinforced concrete beams as well as delaying and even in some cases preventing the debonding of FRP laminates in the longitudinal tensile surface of the beam One of disadvantages of conventional U shaped straps is to control undesirable phenomenon of longitudinal FRP sheet debonding But these straps are not in contact with the sheet in the longitudinal tensile surface of the beam So when ever longitudinal sheet separates from the surface of the beam straps can not inhibit the debonding phenomenon and the flexural capacity able The purpose of the present study is to provide an improved ability to benefit from the advantages of conventional U shaped method as well as removing weaknesses in order to control the vertical and shear stresses between the FRP sheet and beam tensile surface and also providing the ability to direct contact between the U shaped way of tensile surface This method is called the Wrap and Woof Strap WWS and the results are looking pretty good In order to gain to the the study purposes 23 reinforced concrete beams were made with dimensions 120 160 1400 mm and strengthened by FRP sheet in different configurations Then beams were subjected to four point flexural loading The results have shown that the Wrap and Woof Strap WWS method change failure mechanisms of FRP sheet and it s capability in increasing flexural strength of beam is much better the other methods like Externally Bonded Reinforcement EBR and conventional U shape straps Even in many cases this new method completely eliminates the undesirable phenomenon of FRP sheet debonding and increase loading and ductility capacity of specimens Key Words FRP Debonding Rupture Externally Bonded Reinforcement EBR U shaped strap Wrap and Woof Strap WWS Vertical and shear stress PDF created with pdfFactory trial version www pdffactory com

دياري، محسن

معرفي روش مهارهاي تار و پودي ﴿WWS﴾ و مقايسه ي آن با ديگر روش هاي متداول جهت تقويت تيرهاي بتني با FRP

تقويت خمشي , جداشدگي , مهار U شكل