The Architects International Vol 1, Issue 1 - 2018 METHODS OF STRENGTHENING REINFORCED CONCRETE STRUCTURES AND INTRODUCTION TO THE METHOD OF FRP SHEET REINFORCEMENT KAVEH OSTAD-ALI-ASKARI*, VIJAY P SINGH**, NICOLAS R DALEZIOS***, THEODORE C CRUSBERG**** ABSTRACT Many construction buildings and Structural barrier members that was built before 90s in USA, they weren’t designed for Seismic resistance until Federal Emergency Management Agency FEMA started to do seismic evaluation and rehabilitation and suggested reinforcement methods. In this article we evaluate FRP sheet reinforcement. KEYWORDS: Reinforcement Reinforced Concrete Structures, FRP. INTRODUCTION There is a lot of progress in the field of earthquake engineering and structure design in the recent years, so that today we can design earthquake resistant structures with more assurance. Because of reasons like calculating errors, mistakes in implementation, weaknesses in old regulation, changing structural use and operation loads, corrosion of armatures and etc. A lot of reinforced concrete structures cannot satisfy the criteria of regulation, therefore suggesting methods of reinforcement, refinement and rehabilitation for this structures is necessary. REHABILITATION is divided into three main parts: 1-strengthening 2-retrofitting 3-repairing mainly in structure rehabilitation changing this parameters below have more attention toward them and each one will have a crucial part in improvement of structures performance.1-strength enhancement 2-increase in stiffness 3-reduce displacement 4ductility enhancement 5-increase in energy absorption. STRENGTHENING As mentioned in synopsis and introduction, many structures need reinforcement cause of various reasons such as financial and sociological problems. Generally global or local structure rehabilitation * Department of Civil Engineering, Isfahan (Khorasgan) Branch, Islamic Azad University, Isfahan, Iran. Department of Biological and Agricultural Engineering & Zachry Department of Civil Engineering, Texas A and M University, 321 Scoates Hall, 2117 TAMU, College Station, Texas 77843-2117, U.S.A. *** Laboratory of Hydrology, Department of Civil Engineering, University of Thessaly, Volos, Greece & Department of Natural Resources Development and Agricultural Engineering, Agricultural University of Athens, Athens, Greece. **** Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA 01609-2280, U.S.A. Correspondence E-mail Id: editor@eurekajournals.com ** © Eureka Journals 2018. All Rights Reserved. www.eurekajournals.com Methods of Strengthening Reinforced Concrete Structures and Introduction to the Method of FRP Sheet Reinforcement - Kaveh OAA et al. 2 EFFECTIVE FACTORS IN CHOOSING STRENGTHENING TECHNIQUES There is multiple factors strengthening techniques: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. in choosing Cost versus importance of the structure. Available workmanship. Duration of work\disruption of use. Fulfillment of the performance goals of owner. Functionally and aesthetically compatible and complementary to the existing structures Reversibility of intervention. Performance level of quality control. Political and historical significance. Structural compatibility with the existing structural system. Irregularity of stiffness strength and ductility. Control damage to non-structural components. Sufficient capacity of foundation system. Repair materials and technology available. SOME OF THE STRENGTHENING METHODS OF REINFORCED CONCRETE STRUCTURES 1. 2. 3. 4. 5. 6. 7. 8. 9. Concentric or existence steel braces. Post-tensioned cables. Shear walls. Masonry in filled. Base isolator. Steel jacketing. Frp laminates or frp wrapping. Concrete armor. frictional-hysteretic and viscoelastic dampers. RETROFITTING Retrofitting is the process of changing and improvement of designing parameters using available sections. © Eureka Journals 2018. All Rights Reserved. REPAIR Sometimes some structural or non-structural members will be damaged because of phenomenon like fire, earthquake, passing heavy vehicles, rebar corrosion, accidents with vehicles and etc. and they will need repairing in order to gain their main performance. WHAT IS FRP FRP is a kind of composite material consisting of two parts of reinforced fibers that is surrounded by a polymer resin matrix. The fibers can be in one or two perpendicular stretches. Generally there is two types of FRP 1. FRP sheets. 2. FRP rebar. The behavior of FRP sheets is orthotropic or semiorthotropic, that means the modulus of elasticity is different when it's on the same direction as the fibers or when its perpendicular. Generally, the performance of one composite depends on: 1- it's materials 2- the proportion of its material 3-bearing capacity of its fiber and placement of them 4- the constructive behavior with each other and etc. the function of reinforcement fiber is under influence by: 1- the direction of the fibers 2- length of the fibers 3- its shape 4- mixing with resin matrix and the adhesion between the two 5- type of the fiber the main role of matrix is: 1-transfering shear force from reinforcement fiber to the nearby material 2- protecting the fiber from environmental conditions 3-avoid mechanical damages 4-controlling stressed fiber top buckling. REASONS TO USE FRP 1- Bulk production method. 2- Usage in various industries like aircraft and automobile manufacturing. www.eurekajournals.com The Architects International Vol 1, Issue 1 – 2018 3 3- Modified production methods that increased strength and decreased costs. 4- Optimize mixing fiber and resin matrix for better orientation with each other and concrete. 15. Repairing and strengthening important structures like hospitals and historical places. ADVANTAGES OF USING FRP IN REINFORCED CONCRETE STRUCTURES 1. FRP rebar. 2. FRP cover. 1. High durability. 2. Being lightweight. 3. Characteristics resistance and higher modulus. 4. Corrosion resistance. 5. Environmental and chemical resistance. 6. Magnetic inertia. 7. Impact resistance. 8. Low thickness. 9. Easy transportation. 10. Easy sheet implementation. 11. Economic justification for heavy projects. 12. Clean finished surface. DIFFERENT TYPES OF FRP COVERS BASED ON PRODUCTION SOME USAGE OF FRP 1. Increase bearing capacity and plasticity of columns, beams, slabs and reinforced concrete connections. 2. Strengthening of steel and concrete tanks. 3. Strengthening the marine structures. 4. Strengthening the anti-explosion structures. 5. Strengthening the wooden beams and columns. 6. Strengthening the reinforced concrete chimney with building material. 7. Strengthening the reinforced concrete walls. 8. Strengthening the tunnel walls. 9. Strengthening the concrete or steel pipes. 10. Strengthening the brick walls and traditional material. 11. Building coast walls. 12. Industrial roof tops. 13. Reactors equipment seat. 14. Slab floor system in chemical corrosive environment. © Eureka Journals 2018. All Rights Reserved. DIFFERENT TYPES OF FRP IN CIVIL ENGINEERING 1. Handmade covers and vet layup. 2. Pre made composite sheets. 3. Pultrusion sheets: in this process the sheets pass through a thermal chamber and in the meantime it goes under stretching. NEW COMPOSED SYSTEMS Sometimes for structure rehabilitation or strengthening methods for example recently Prof. J.G. Teng presented column model FCSDS that consists of one internal steel pipe and one external FRP cover and the space between them is filled with concrete. We see that this column doesn’t have the same problem as steel pipes because it doesn’t buckle under stress caused by concrete cover, on the other hand the concrete is surrounded FRP cover and ultimate bearing capacity and ultimate strain will greatly increases. STRENGTHENING THE STRUCTURAL BARRIER MEMBERS WITH FRP SHEET FRP sheets is used for buckling, shear and torsion reinforcement and mixing them with bearing members like beams, columns, connections, walls and reinforced concrete slabs and even nonbearing members. Recently the FRP sheets even used for reinforcement of steel profiles and for best use, it will be used in pre stressed mode in reinforcement system. 1. Buckle and shear reinforcement for beams for controlling thematic breakdown like lack www.eurekajournals.com Methods of Strengthening Reinforced Concrete Structures and Introduction to the Method of FRP Sheet Reinforcement - Kaveh OAA et al. 4 of link and adhesiveness at the end of the beam in buckle reinforcement mode, straps or U type sheets will be used for sticking on the end closure of the beam. in shear reinforcement mode we can use integrated pattern sheets or laminates and strips like figure 8. The sheet type used for buckle reinforcement (CFRP laminate) is different than the one used for shear reinforcement (GFRP laminate). high chance of earthquake the importance of reinforcement and seismic structure design has main priority. 3. Exploring various methods of strengthening and comparing them with each other in order to find the best way focusing on economic and social conditions of a location is necessary. FRP straps or even FRP sheets can be used in different angles specially 45 for controlling shear cracks and in various layers even two perpendicular layers. [1]. 2. Column reinforcement REFERENCE [2]. Methods of column reinforcement are: • • • • • • Spiral rebar Circular screwing and wrapping Using composite straps\cables Automatic spiral rebar Gluing pre-made sheets Injecting glue or matrix in case of rectangle columns the shape of FRP sheet make less enclosure so these columns will be filled by concrete in order to become circular and after that they wrapped by FRP sheets. 3. Enhance the connection and slap system or bridge deck [3]. [4]. [5]. We can strengthen the reinforced concrete connections that are sensitive and it's difficult to strengthen them, using FRP sheets. CONCLUSION 1. Using FRP sheets and rebar for reinforcement and rehabilitation of concrete reinforced structures is increasing everyday so theoretical and laboratorial researches are needed. 2. Because our country located faults that have © Eureka Journals 2018. All Rights Reserved. [6]. Jong Wha Bai “Seismic Retrofit for Reinforced Concrete Building Structures" Consequence-Based Engineering) CEB (Institute Final Report-Texas UniversityAugust 2003. Jianhua Liu “Rehabilitation of Seismically Deficient Reinforced Concrete StructuresState of the art” university of Alberta; An Interdisciplinary Journal 2006. Jack P. Moehle “State of Research on Seismic Retrofit of Concrete Building Structures in the US” Pacific Earthquake Engineering Research Center University of California, Berkley; US-Japan Symposium and Workshop on Seismic Retrofit of Concrete Structures-State of Research and Practice. Giorgio Monti “Seismic Upgrade of Reinforced Concrete Columns with FRP” University Spienza Roma, Italy. Michael N. Fardis “Seismic Assessment and Retrofitting of Existing Buildings According to Euro code 8” Dept. of Civil Engineering of Patras, Greece, Fifth National Conference on Earthquake Engineering 2630 May 2003, Istanbul, Turkey. Tetsuo Yamkawa, Mehdi Banazadeh , Shogo Fujikawa “ Emergency Retrofit of Damaged RC Columns Right after Seismic Attack Using Pre-Tensioned Aramid Fiber Belts” 1st Conference on Application of FRP Composite in Construction and Rehabilitation of Structures May 4, 2004, Tehran, Iran. www.eurekajournals.com The Architects International Vol 1, Issue 1 – 2018 5 [7]. [8]. [9]. Ghassan K. Al. Chaar and Georgy E. Lamb "Design of Fiber-Reinforced Polymer Materials for Seismic Rehabilitation of Infilled Concrete Structures "- December 2002- US Army Corps of EngineeringResearch and Development Center. F.M. Mazzolani; G.Della Corte; B. Faggiano “Full Scale Testing and Analysis of Innovative Techniques for Seismic Upgrading of RC Buildings “. Ali Sehat Tabatabaei “Energy Dissipation systems for seismic resistance” Iran civil center website. © Eureka Journals 2018. All Rights Reserved. [10]. T. Yamakawa, K. Nasrollahzadeh Nesheli, H. Satoh “Seismic Retrofitting of RC Columns Using Restressed Aramid Fiber Belts” Fourth International Conference of Earthquake Engineering and Seismology 12-14 May 2003 Tehran, Iran. [11]. M. Sadoughi Yarandi, M. Saatcioglu “Seismic Retrofit of Rectangular Concrete Column with Splice Deficiencies by External Restressing” Fourth International Conference of Earthquake Engineering and Seismology 12-14 May 2003 Tehran, Iran. www.eurekajournals.com