مقاوم سازي اتصال ستون هاي بتن مسلح دايره يي به پي به كمك ميلگردهاي GFRP و ورق هاي CFRP

STRENGTHENING OF CIRCULAR REINFORCED CONCRETE COLUMNS TO FOUNDATION CONNECTION WITH GFRP BARS an‎d CFRP SHEETS

در نوشتار حاضر، اتصال ستون هاي بتن مسلح دايره يي به پي با استفاده از پليمرهاي مسلح اليافي مقاوم سازي و رفتار آن ها به صورت تحليلي و آزمايشگاهي بررسي شده است. تعداد 4 نمونه اتصال ستون بتن مسلح دايره يي به پي با استفاده از ميلگردهاي GFRP و ورق هاي CFRP مقاوم سازي شدند. يكي از نمونه ها فاقد تقويت، دو نمونه ي ديگر با ميلگردهاي GFRP با قطرهاي متفاوت تقويت شدند. نمونه ي چهارم نيز با ميلگردهاي GFRP و ورق هاي CFRP تقويت شد. اين نمونه ها تحت اثر همزمان بار محوري فشاري ثابت و جابه جايي جانبي چرخه يي قرار گرفتند. به منظور بررسي توانايي نرم افزار آباكوس، نمونه هاي آزمايشگاهي در نرم افزار مذكور شبيه سازي شدند. پارامترهاي سختي اوليه، ظرفيت اتلاف انرژي، ظرفيت باربري جانبي و شكل پذيري نيز در نمونه هاي مذكور بررسي شد. نتايج نشان داد كه تقويت خمشي اتصال موردنظر با ميلگردهاي GFRP موجب افزايش قابل توجه پارامترهاي ذكر شده خواهد شد. افزايش قطر ميلگردهاي GFRP نيز نقش موثري در افزايش پارامترهاي مذكور داشت. بيشترين مقدار افزايش در پارامترهاي مذكور مربوط به نمونه ي چهارم بوده است. همچنين نتايج آزمايشگاهي و تحليلي نمونه ها تطابق قابل قبولي داشتند.

Bridges play a significant role in developing the roads and accelerating the serviceability in normal and emergency situations. The corrosion problem of steel reinforcing bars in reinforced concrete columns of bridges in humid environments results in the early deterioration of these structures. Therefore, it is vital to use the efficient and cost-effective strengthening methods to increase the serviceability of these structures in critical situations. In this study, the strengthening of circular reinforced concrete column to foundation connections with fiber reinforced polymers is investigated. In the experimental part of the study, four specimens of column-foundation connections were cast and tested. One specimen was used as the control specimen without strengthening. Two other specimens were strengthened with GFRP reinforcing bars of different sizes. The fourth specimen was strengthened with both of GFRP reinforcing bars and CFRP sheets. These specimens were under constant axial compressive load and cyclic lateral displacement, simultaneously. Initial stiffness, energy dissipation capacity, lateral load capacity and ductility of the specimens are studied. In order to investigate the ability of the ABAQUS software, the experimental specimens were simulated in the aforementioned software. Test results show that the amount of lateral load capacity, initial stiffness, energy dissipation capacity and ductility increase significantly due to flexural strengthening of circular reinforced concrete column to foundation connections with GFRP bars. The highest increase in the amount of the aforementioned parameters is observed in the specimen strengthened with GFRP bars and CFRP sheets. The analytical results also show good agreement with the experimental results. The main difference between the analytical and experimental results is due to the simulation of pinching effect of the experimental results.