Fiber Reinforced Polymers – The Technology Applied for Concrete Repair PDF by Martin Alberto Masuelli

Contents

Preface
This book deals with fibre reinforced polymers (FRP). Research on FRP is currently increasing as polymerics entail a quickly expanding field due to the vast range of both traditional and special applications in accordance with their characteristics and properties. FRP is related to the improvement of environmental parameters and consists of important areas of research demonstrating high potential and is therefore of particular interest. Research in these fields requires combined knowledge from several scientific fields of study (engineering, physical, geology, biology, chemistry, polymeric, environmental, political and social sciences) rendering them highly interdisciplinary. Consequently, for optimal research progress and results, close communication and collaboration between various differently trained researchers such as geologists, bioscientists, chemists, physicists and engineers (chemical, mechanical, electrical) is vital.

This book covers the FRP-concrete design of structures to be constructed, as well as the safety assessment, strengthening and rehabilitation of existing structures. It contains seven chapters covering several interesting research topics written by researchers and experts in the field of civil engineering and earthquake engineering. The book provides the state-ofthe- art knowledge on recent progress on humidity and earthquake-resistant structures. This book will be useful to graduate students, researchers and practice structural engineers.

The book consists of seven chapters divided into three sections. Section I includes two chapters on polymers and composites used in FRP. Chapter 1 focuses on the polymers used in FRP. This chapter is a basic study of polymers (as aramids), composites (as carbon and glass fibre reinforced polymers). The use of FRP reinforcements is reviewed, assessment of the art state , and progress made. This includes concepts of polymers, FRP process and a brief discussion related to fibreglass and carbon fibre applications. It is observed that technical problems can all be resolved, but each resolution provides a significant increase in the properties of the polymers. However, in concrete products and composites, the FRP reinforcements in the form of meshes, textiles or fabrics are not only competitive on a technical basis, analysis is also conducted on the use of FRP reinforcements in effective applications on concrete repair.

The use of composites fibre reinforced polymer (FRP) has gained acceptance in civil infrastructure as a result of the need to rehabilitate or retrofit existing structures, construct infrastructure systems faster, and the increase of the usable life of the built environment, all of which are vital. In addition, increased attention to sustainable built environments has challenged engineers to weigh up the environmental and social impacts of their constructions in addition to traditional measures of performance and cost of the built environment.

However, these statements are truncated if no reference to the polymers is made, the properties and compounds derived there from and the resultant interactions that result in civil engineering solution. Therefore, this chapter describes the physicochemical properties of the polymers and compounds used in civil engineering. The issue will be addressed simply and in basic form to allow better understanding.

Chapter 2 is written by Eustathios Petinakis, Long Yu, George Simon and Katherine Dean. This chapter deals with the poly(lactic acid) (PLA), being a compostable synthetic polymer produced using monomer feedstock derived from corn starch, which satisfies many of the environmental impact criteria required for an acceptable replacement for oil-derived plastics. PLA exhibits mechanical properties that make it useful for a wide range of applications, but mainly in applications that do not require high performance including plastic bags, packaging for food, disposable cutlery and cups, slow release membranes for drug delivery and liquid barrier layers in disposable nappies. However, the wider uptake of PLA is restricted by performance deficiencies, such as its relatively poor impact properties which arise from its inherent brittleness, and the significantly higher price of PLA compared with commodity polymers such as polyethylene and polypropylene.

Section II includes three chapters on corrosion protection and concrete repair. These chapters include reviews of information and research results/data on compatibility and on construction repair applications of FRP.

Chapter 3 is written by George C. Manos and Kostas V. Katakalos. This chapter is devoted to the advances of reinforced concrete structural members by externally applying fibre reinforced polymer (FRP) sheets. These structural members represent slabs, beams, columns or shear walls that were either damaged by an earthquake or can be potentially damaged by a future strong earthquake. The strengthening usually addresses either their flexural capacity or their shear capacity. In order to upgrade the flexural capacity, the usual practice is to externally apply the FRP sheets as longitudinal reinforcement either at the bottom or at the top side of the structural member. In order to upgrade the shear capacity, the usual practice is to apply FRP strips externally in the form of transverse reinforcement, either in closed hoops or open U-shaped strips. Moreover, for structural members with the potential of developing compressive zone failure, the strengthening schemes utilize externally wrapped FRP sheets in order to increase the confinement of the compressive zone. The typical forms of earthquake damage of reinforced concrete structural members are presented and discussed. The selected results of experiments focus on the upgrading of either the flexural or the shear capacity of reinforced concrete structural elements.

Chapter 4 is written by Mônica Regina Garcez, Leila Cristina Meneghetti and Luiz Carlos Pinto da Silva Filho. This chapter sheds lights on recent analyses of the efficiency of prestressed carbon fibre reinforced polymers applied to post-strengthen reinforced concrete beams by means of cyclic and static loading tests. Experimental results of static loading tests are compared to the ones obtained through an analytical model that considers a tri-linear behaviour for moment versus curvature curves. These results allow the analysis of the quality and shortcomings of post-strengthen technique studied and make possible the identification of the more suitable post-strengthening solutions to each circumstance.

Chapter 5 is written by Theodoros C. Rousakis and deals with the experimental investigation on a new hybrid confining technique using fibre reinforced polymer sheets and fibre rope as outermost reinforcement. The fibre rope is applied after the curing of the FRP jacket without the use of impregnating resin. The ends of the fibre rope are mechanically anchored through steel collars. Two concrete qualities and three different confinement schemes are examined for comparison. The axial stress versus axial and lateral strain behaviour reveals a remarkable performance of the fibre rope after the fracture of the FRP. The suitably designed fibre rope confinement withstands the force unbalance after FRP fracture, and after a temporary load drop, the load borne by the concrete rises again. The ultimate experimental values recorded from the cyclic compressive loading of confined concrete cylinders show substantial upgrade of concrete axial strain and stress.

Section III includes two chapters on applications of theory-practice analyses in concrete and concrete products.

Chapter 6 is written by Riad Benzaid and Habib-Abdelhak Mesbah, and sheds light on the recent results of an experimental study on the behaviour of axially loaded short concrete columns, with different cross sections that have been externally strengthened with carbon fibre-reinforced polymer (CFRP) sheets.

Chapter 7 is written by Manal K. Zaki and deals with fibre method modelling (FMM) together with a displacement-based finite element analysis (FEA) used to analyse a threedimensional reinforced concrete (RC) beam-column. The analyses include a second-order effect known as geometric nonlinearity in addition to the material nonlinearity. The finite element formulation is based on an updated Lagrangian description. The formulation is general and applies to any composite members with partial interaction or interlayer slip. An example is considered to clarify the behaviour of composite members of rectangular sections under biaxial bending. In this example, complete bond is considered. Different slenderness ratios of the mentioned member are studied. Another example is considered to test the importance of including the bond-slip phenomenon in the analysis and to verify the deduced stiffness matrices and the proposed procedure for the problem solution.

I hope this book benefits graduate students, researchers and engineers working in resistance design of engineering structures to earthquake loads, blast and fire. I thank the authors of the chapters of this book for their cooperation and effort during the review process. Thanks are also due to Ana Nikolic, Romana Vukelic, Ivona Lovric, Marina Jozipovic and Iva

Lipovic for their help during the processing and publishing of the book. I thank also of all authors, for all I have learned from them on civil engineering, structural reliability analysis and health assessment of structures.