پديد آورندگان :
محمدي، مهديه دانشگاه تبريز - دانشكده مهندسي عمران و سازه , برقيان، مجيد دانشگاه تبريز - دانشكده مهندسي عمران و سازه , فرزام، مسعود دانشگاه تبريز - دانشكده مهندسي عمران و سازه , مستوفي نژاد، داود دانشگاه صنعتي اصفهان - دانشكده مهندسي عمران
چكيده فارسي :
الياف پليمري تقويت شده ( FRP) در مقاوم‌سازي سازه‌هاي بتني و فولادي، پل‌ها، مخازن و ... به طور گسترده استفاده مي‌شوند. وجود محيط هاي مخرب اعم از دماي بالا، محيط قليايي، اسيدي و ... امري اجتناب ناپذير است و در برخي موارد خرابي‌هاي جبران ناپذيري را سبب مي‌شوند. تاثير شرايط محيطي مختلف بر مقاومت اتصال بين بتن و FRP به طور پراكنده مورد بررسي و آزمايش قرار گرفته است. با اين وجود مطالعات در اين زمينه كافي نمي‌باشد. به همين منظور در اين مقاله تاثير محيط قليايي در دماهاي مختلف بر مقاومت اتصال بتن-FRP بررسي شده است. مراحل كار به 4 قسمت تقسيم مي‌شود: 1) ساخت نمونه‌هاي آزمايشگاهي، 2) آماده‌سازي سطحي به دو روش نصب خارجي سطحي ( EBR) و نصب خارجي سطحي روي شيار ( EBROG)، 3) تقويت نمونه‌ها با الياف CFRP و قرار دادن آن‌ها در شرايط محيطي، 4) بررسي مقاومت پيوند سطح بتن- FRP بعد از خارج كردن نمونه‌ها از شرايط محيطي. مقاومت فشاري نمونه‌ها در حدود 35 مگاپاسكال و مدت زمان نگهداري نمونه‌ها در شرايط محيطي 3000 ساعت مي‌باشد. نتايج نشان مي‌دهد كه روش EBROG در شرايط محيطي مختلف عملكرد بهتري نسبت به روش EBR دارد و همچنين ظرفيت باربري نهايي نمونه‌هاي تقويت شده به روش EBROG در حدود 50 درصد بيشتر از ظرفيت باربري نمونه‌هاي تقويت شده به روش EBR است.
چكيده لاتين :
Various researches have been performed regarding the deterioration and behavior of fabrics made from carbon, glass and aramid in different environmental conditions. Carbon fibers reinforced polymer (FRP) are very corrosion resistant. The CFRP laminates are extremely useful in very corrosive atmospheres, such as marine and aggressive chemical atmospheres. They have been advanced over the years because of their high strength, light weight, long-term durability and high resistance to deterioration. The very thin (0.2 - 0.4 mm) laminates are very easy to apply and can be applied in cross directions without any difficulty. Environmental conditions impact on the bond strength of FRP-to-concrete has sparsely been investigated. The sources of CFRP bond deterioration can originate from alkaline attack and thermal expansion. Alkaline attack occurs at the interface of the concrete and a CFRP laminates with the resulting damage to the matrix of the CFRP laminates. Also, alkali aggregate reaction can lead to the destruction of concrete elements. However, studies in this field are not enough and for externally bonded FRP materials, no such long term test results are available yet. Severe corrosion damage can often be prevented by a correct treatment of the structure against chemical influences or aggressive environmental effects. Methods such as the externally bonded reinforcement (EBR), despite of their advantages, have a problem known as the premature debonding of FRP from concrete substrate. In this method the surface of concrete is sanded and cleaned. After the preparation of the surface, the layer of epoxy is applied uniformly on the surface of concrete. Then, FRP is installed on the surface and saturated with epoxy. In other hand, a new strengthen method is the externally bonded reinforced on grooves (EBROG) method that consists of grooves on the surface of concrete. In this method, grooves with a proper length, width and depth are catted on the concrete surface; then the concrete surface and the grooves are cleaned with an air pressure. Later, grooves are filled with an appropriate epoxy. At the end, FRP sheets are installed with a proper epoxy on the concrete surface. In this paper, the effect of environmental conditions, including three alkaline environments with temperatures of 〖 23〗^° C, 〖40〗^° C and 〖60〗^° C, was investigated on the bond strength of FRP-to-concrete. The specimens were strengthened with two methods: EBR and EBROG. Samples were kept in environmental conditions for 3000 hours. Single-shear tests were conducted to evaluate the bond behavior of FRP-to-concrete. Experimental results showed that the specimens strengthened by the EBROG method - in the alkali environment with different conditions - experienced up to 50 % higher than ultimate bond loads compared with the specimens which were strengthened by the EBR method. In the EBR method, the bond failure mode changed from concrete delamination in laboratory condition to epoxy-concrete interface separation in alkali immersion with different temperatures. On the other hand, in the EBROG method environmental conditions had not effect on the mode of failure and more than 90% of specimens experienced FRP rupture. As a whole, the alkali environment caused a sudden drop in the bond strength of FRP-to-concrete substrate.
