Issue34

I. Ivanova et alii, Frattura ed Integrità Strutturale, 34 (2015) 90-98; DOI: 10.3221/IGF-ESIS.34.09 91 I NTRODUCTION n the 20 th century the people believed that concrete is eternal material. Nonetheless today everyone knows that all concrete structures and elements have a certain service life. During their life the original quality and sustainability changed. In fact it's necessary to have a good deal of knowledge about the mechanical properties and mechanical behavior of reinforced concrete structures [1] under different environmental conditions. It allows to take timely measures for the protection and extend the life of reinforced concrete. The reinforced concrete short corbel is one important element as cast monolithic with the column element to wall element like demonstrated by Ivanova and all [2-4]. Corbels are used very often in industrial buildings and structures. For example: a participating corbel in reinforced concrete bridge construction lay on the structural elements of the bridge superstructure (beams and plates). Then they are subjected to repeat varying load of traffic [10]. These stresses on a large scale can lead to reaching the ultimate limit state of fatigue. Indeed the strengthening of concrete elements operating under static and dynamic loads is of special interest for the following reasons: cyclically variable dynamic load caused uniquely or dual significance stress and strain state. The intensity and diversity of dynamic load action create conditions for specific behavior of reinforced concrete elements [8]. Then also the joint work between reinforced concrete and composite material allowed a resumption of fatigue stresses. The development of new technologies using composite materials leads to improve the load carrying capacity and the mechanical properties of reinforced elements. It is possible also to increase flexural and shear strength to reduce deformations and cracks expected [9, 11]. The carbon fiber fabrics as external reinforcement are bonded with epoxy resin which resumed tensile stress in the fiber direction. In award, carbon fiber materials are characterized by a low specific gravity, a high tensile strength, fatigue performance and anti-corrosion. This paper presents an experimental study of strengthened reinforced short concrete corbels under static and dynamic loads. The carbon fiber fabrics is applied on a tensile zone where it is located and available supporting tensile steel. So carbon fiber fabrics absorbed more tensile stresses and provided a high strength of element [5, 6 and 7]. Based on the inventory of researches have concluded that reinforcement with carbon fiber fabrics reduced appearance and spread of cracks, provided greater durability and higher maximum load. E XPERIMENTAL PROGRAM our reinforced short concrete corbels are tested. Among them two specimens without reinforcement and the other two specimens are strengthened by externally bonded carbon fiber fabrics in wrapping. The experimental study is investigated to study the crack path and crack growth in reinforced short concrete corbel. This study is compared with repaired reinforced short concrete corbel bonded with carbon fiber fabrics under static and dynamic loads. The objective of this study was to exhibit strengthened reinforced concrete corbel behavior under repeated load. Then, this study is compared with strengthened reinforced concrete behavior under static loading. Then this paper described also the ultimate load versus the cracking mechanisms and the failure modes. T EST SPECIMENS GEOMETRY he column supporting two short trapezoidal corbels cantilevering on either side was 150 mm by 300 mm in cross section and 1000 mm of length. Corbels had cantilever projection length of 200 mm, with thicknesses of 150 mm at both faces of column and in the free end. All reinforced concrete corbel specimens have the same sizes and are strengthened reinforced concrete corbels in the same way detailed as in Fig. 1. For all specimens are tested using a single load with a shear span to depth ratio a/d equal to 0.45. The control specimen without strengthening is denoted " C0 ", the first letter " C " means Corbel and "0" zero indicates without strengthening. The name of strengthened reinforced concrete corbel "CB3u" is made up as follows: The first letter " C " is, as previously C orbel and the second letter represents the type of strengthening (e.g.: B for B andage). Then digit indicates the number of layers (e.g.: 3) and the small letter indicates finally the type of composite material (e.g. u for u nidirectional) . I F T