ارزيابي تجربي رفتار خمشي تيرهاي بتن آرمه‌ي خودتراكم حاوي الياف تحت بارگذاري سيكلي

Experimental Evaluation of the Flexural Behavior of Self-Compacting Reinforced Fibrous Concrete Beams under Cyclic Loading

تاكنون پ‍‍ژ‍وهش هاي بسياري جهت ارزيابي رفتار تيرهاي بتن آرمه‌ي اليافي تحت بارگذاري يكنواخت انجام شده است، ولي مطالعات محدودي بر روي رفتار آن ها تحت بارگذاري سيكلي انجام شده است. در اين پژوهش، يك مطالعه‌ي جامع آزمايشگاهي جهت بررسي خصوصيات مكانيكي تيرهاي بتن آرمه‌ي خودتراكم اليافي صورت پذيرفته است. هدف اصلي اين مطالعه، ارزيابي تاثير استفاده از الياف در رفتار المان سازه‌يي تير است. الياف مورد استفاده شامل: الياف فولادي (Steel) و پلي فينيل سولفايد (PPS) بوده است. مقادير انتخابي هر نوع الياف برابر 1/0، 2/0، 3/0، و 4/0 نسبت حجمي الياف به بتن است، و بتن فاقد الياف به عنوان بتن مرجع در نظر گرفته شده است. نتايج نشان مي دهد كه افزودن الياف موجب افزايش ظرفيت باربري و انرژي تلف شده و همچنين باعث كاهش عرض ترك در مقايسه با طرح مرجع مي‌شود. مقايسه‌ي تاثير استفاده از دو نوع الياف مذكور نشان مي دهد كه بتن حاوي الياف فولادي، مقادير انرژي تلف شده‌ي تجمعي بيشتر و مقاومت بالاتري را نسبت به مقدار متناظر در بتن حاوي الياف PPS نتيجه مي دهد.

When a structure is hit by an earthquake, a tremendous amount of seismic energy released by the earthquake is injected into the structure as ground motion. The structure is also subjected to reverse loads, which cause severe deterioration of the concrete. To release seismic energy, the structure should be damaged in such a way that, on the one hand, the collapse of the structure should not occur, and, on the other hand, after the earthquake, the damage should be economically feasible to repair. One of the drawbacks associated with fiber reinforced concrete (FRC) is that the addition of fibers to a traditional concrete mix at high fiber content can result in workability problems. The combined use of Self-Compacting Concrete (SCC) and fibers can solve this problem and facilitate placement for a wider range of structural applications. SCC is a new class of high performance concrete that can spread readily into place under its own weight and fill restricted sections, as well as congested reinforcement structures, without the need of mechanical consolidation and without undergoing any significant separation of material constituents. Although several studies have been conducted on the behaviour of FRC beams subjected to monotonic loading, there is limited research on the behaviour of FRC beams under cyclic loading. This paper presents the results of an experimental study conducted on 18 FRC beam specimens tested under cyclic and monotonic loading. The main objective of this research is to investigate the effect of fibers on structural element (beam) behavior. Steel fiber and PolyPhenylene Sulfide (PPS) were used in this work. The content of fiber was 0.1, 0.2, 0.3 and 0.4 of volume, and concrete without fiber is considered as a reference. The results show that adding fiber increases dissipated energy and bearing capacity and also reduces crack width. A comparison of two types of fiber in this study show that concrete containing steel fiber has a higher amount of cumulative dissipated energy, and higher strength than the corresponding amount in concrete containing PPS fiber.