بررسي آزمايشگاهي ظرفيت خمشي و فشاري پانل هاي بتن مسلّح به الياف شيشه

Experimental Investigation of Compressive and flexural capacity of concrete panels reinforced with GFRP fiber

استفاده از الياف يك گام مؤثر در جلوگيري از انتشار ريزترك ها در جبران ضعف مقاومت كششي بتن محسوب مي شود و نياز به يك طرح اختلاط بهينه جهت كسب مقاومت‌هاي مكانيكي قابل قبول مي باشد. در اين مقاله يك تحقيق آزمايشگاهي با در نظر گرفتن متغير هاي مختلفي مانند نوع الياف شيشه، درصد الياف، درصد و نوع سيمان و نوع سنگدانه و پارامترهاي ديگر ، با ساخـت و آزمايش 42نمونه مكعبي بتني فشاري و 78 پانل خمشي بتني GFRC انجام شده است. نمونه هاي خمشي تحت بارگذاري هاي گسترده، متمركز، و رفت و برگشتي قرار گرفتند. نتايج نشان داد درصد الياف زيادتر منجر به افزايش مصرف سيمان ، ميزان جذب انرژي، ضريب طاقت، و حداكثر بار تحملي در پانل هاي خمشي تحت بار گسترده و بارگذاري رفت و برگشتي تا 37 درصد و افزايش تعداد سيكل هاي لازم جهت رسيدن به مقاومت نهايي در بارگذاري رفت و برگشتي شد.

Application of fiber is effective step to preventing crack propaganda and remedy concrete tensile strength weakness particularly at the precast and expose walls and shell roofs, so an optimum mix design to obtain acceptable mechanical strengths and reducing cement assumption. An experimental compressive investigation was conducted in this paper and several variables such as different kind and percentage of fiber, different kind and percentage of cement, and different aggregate sizes were considered. 42 compressive 100 mm cubic specimens and 78 GFRP concrete flexural 200 by 800 mm panels at different thickness 20, 40 and 60 mm were casted. Flexural specimens were tested under three different loading; distributed, concentrated, and cyclic loading. The test results showed that even though the compressive strength of concrete specimens were not increased by adding fibers, so white cement and Cinoma fiber showed the more effective compare to those specimens cast with gray cement and NEG fibers. The cement consumption, energy absorption, toughness index of GFRP concrete specimens cast with higher percentage of fiber particularly with NEG fibers were increased. Through increasing fiber percentage, the numbers of cyclic, the maximum tolerated loads at the cyclic loading were consequently increased by 37 and 25%. Comparison of specimens tested under distributed and concentric loadings showed that the maximum tolerated capacity and energy absorption and, toughness index for specimens under distribution loading were respectively increased by 5-10 % and 22-36% due to better load transferring and using fiber potential.