Issue34

I. Ivanova et alii, Frattura ed Integrità Strutturale, 34 (2015) 90-98; DOI: 10.3221/IGF-ESIS.34.09 94 The results allowed to know when the first crack appeared. This crack is created before fatigue loading. The changed slope is proof that a crack is created. In fact, this study needs to follow crack propagation. Initially, the unarmed concrete corbel is charged up to the initiation of the first crack. It is characterized by a change in slope and then a second time, is applied a triangular signal with a mean stress up to one million cycles. Triangular signal is applied with a mean stress. Next, reinforced concrete short corbel is subjected to cyclic loading up to one million cycles. After one million cycles, reinforced concrete corbel was static loading until failure. Secondly, it was the same proceeding with strengthened reinforced concrete corbel "CB3u". Tab. 1 shows values of ultimate load F u , minimal load F min and maximal load F max in between 20 % and 40 % of maximum load F u . In fact, with a cyclic load in this range, the development of crack can be followed. The previous experimental study identified the occurrence of cracks and their propagations. F u (kN) F min (kN) 20% F max (kN) 40% Reference corbel: C0 357 71.4 142.8 Strengthened corbel by wrapping: CB3u 651 130.2 260.4 Table 1 : Conditions of fatigue load. E XPERIMENTAL RESULTS AND DISCUSSIONS he results showed for static test the ultimate tensile strengths are respectively 357 kN for reinforced concrete corbel without strengthening and 651 kN for strengthened reinforced concrete corbel bonded by wrapping carbon fiber fabrics. Figure 4 : Effect of fatigue on reinforced concrete corbels under static tests. Influence of static and dynamic loadings on reinforced concrete corbels behavior Fig. 4 described the comparison of behavior between reinforced concrete corbels "C0" loaded in static and dynamic tests. There is a change in slope at 60 kN for unstrengthened corbel in static loading. In fact, after one million cycles of fatigue, T