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Debonding of FRP EBR: from testing to design

External bonding of fibre reinforced plastic (FRP) strips to reinforced concrete (RC) beams has been widely accepted as an effective method for strengthening. The ultimate flexural strength of strengthened RC beams can be improved significantly, but it is often impaired by premature failure modes, such as concrete cover separation.
Several models have been proposed dealing with this issue. The aim of this study is to assess the performance of the existing models with experimental data gathered from the published literature. It is concluded than the models based on fracture energy seem predict better the failure load than the models based exclusively on shear strength of concrete.
Moreover, the behaviour of bond between FRP and concrete is a key factor controlling the behaviour of concrete structures strengthened with FRP composites. This work presents a study on the bond strength using several types of test methods.
Experimental data from literature used to assess the performance of the several test methods. Furthermore, ABAQUS software used to model the test methods in order to understand the behavior of failure and investigate the stresses in concrete and in FRP plate. Another aim of this dissertation is to identify which of the available test methods better represents a real situation and can thus yield more representative data than can be used to effectively calibrate the fracture energy parameter.
It is concluded than the theoretical prediction from the “fracture energy” models is slightly conservative when the compressive concrete strength is high. The double test and bending test may be the two test more rappresentative to rapresent the debonding, both test have similar behavior justified from the similar tangential stress and trend as well as in those tests the load necessary to reach the tensile strenght is higher respect the single shear test.

Mostra/Nascondi contenuto.
Introduction Chapter 1 1 Chapter 1 Introduction 1.1 General Reinforced concrete (RC) is widely used as a conventional material for building in civil and industrial engineering construction since it was invented in 19 th century. Nowadays, the unsatisfactory behavior of existing structures is becoming one of the major problems faced by structural engineers. Reasons for inadequate behavior include previous errors in design, inferior materials, corrosion due to environmental attack, bad construction practices, damage due to exceptional loads. In addiction load that for what they were originally designed for. Depending from the circumstances, there are two possible solutions: demolish and rebuilt or strength the structure. There is a large variety of material and techniques that are available for repair of damaged concrete building and structures. However, the traditional strengthening and repair methods present a great number of practical problems. In addition, most traditional techniques are intrusive, time consuming and expensive. In recent years the development of synthetic and epoxy adhesives combined with the using of Fiber Reinforced Concrete (FRP) has led to a very effective technique for repairing or strengthening concrete structures. There has been an increase in the use of fiber reinforced polymer to repair and strengthen structural members such as slabs, beams and columns. FRP uses to increase flexural strength of slabs, flexural strength and shear strength of beams and shear strength and the confinement of columns. Another application is to enhance continuity between precast members at joint. The principal reasons are to use FRP: the structural members that need to be strengthened by FRP are subjected to more applied load, for example, increasing the vehicle loads on bridges, changing the use of buildings from residential to commercial and accidental events such as earthquakes. Therefore it is necessary to add the reinforcement to the weaker members. Moreover, the occurrence rate of earthquake has increase over the past years, structures and building suffer from lack of proper maintenance and also the effects of natural disasters. Hence, FRP sheets are used to

Laurea liv.II (specialistica)

Facoltà: Ingegneria

Autore: Fabio Durante Contatta »

Composta da 151 pagine.

 

Questa tesi ha raggiunto 292 click dal 11/05/2011.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.