Abstract: As our infrastructure continues to age, retrofitting of existing structural members is becoming a very common practice. Several methods have been researched and proven effective in increasing the axial load capacity of reinforced concrete columns. These methods include concrete, steel, and fiber reinforced polymer (FRP) jackets. Reinforcement for concrete jacketed specimens has traditionally been provided by rebar reinforcement as well as welded wire fabric (WWF). FRP has been applied as a wrap and in composite plate form. A new reinforcement product, Prefabricated Cage System (PCS), is suggested as a possible alternative retrofit reinforcement for concrete jackets. A thorough literature review of concrete retrofit and confinement research was conducted. The aforementioned retrofits are experimentally tested and compared with the new PCS reinforcement product as part of this research. Seventeen circular columns were constructed, retrofitted, and tested under axial compression until failure. Axial load-displacement responses of the specimens were recorded and the critical behaviors of the specimens were documented during testing. Data from the testing is analyzed and compared. Additionally, innovative concepts to accurately determine the behavior of concrete jacket retrofitted columns are presented, which may assist in future concrete jacket retrofit modeling.
Reinforced concrete columns play a very important role in structural performance. As such, it is essential to apply a suitable analytical tool to estimate their structural behaviour considering all failure mechanisms such as axial, shear, and flexural failures. This book highlights the development of a fiber beam-column element accounting for shear effects and the effect of tension stiffening through reinforcement-to-concrete bond, along with the employment of suitable constitutive material laws.
The book describes a detailed comparision of the various engineering properties of an FRP column and a reinforced concrete column. Also, a detailed understanding of the various processes involved in the manufacturing and testing of a FRP composite for retrofitting has been presented. There is a considerable number of existing reinforced concrete structures that do not meet current design standards because of inadequate design and/or construction or need structural upgrading to meet new seismic design requirements. Inadequate performance of this type of structures is a major concern from public safety standpoint. This paper presents an experimental research program aimed at developing a retrofitting technique that utilizes locally available high strength, lightweight, corrosion resistance advanced composites for retrofitting existing reinforced concrete columns. The proposed technique consists of applying Glass Fiber Reinforced Plastic (GFRP) to all surfaces of the concrete column to increase its stiffness and flexural strength.
In most parts of the developed world, the building stock and the civil infrastructure are ageing and in constant need of maintenance, repair and upgrading. Moreover, in the light of our current knowledge and of modern codes, the majority of buildings stock and other types of structures in many parts of the world are substandard and deficient. This is especially so in earthquake-prone regions, as, even there, seismic design of structures is relatively recent. In those regions the major part of the seismic threat to human life and property comes from old buildings. Due to the infrastructure's increasing decay, frequently combined with the need for structural upgrading to meet more stringent design requirements (especially against seismic loads), structural retrofitting is becoming more and more important and receives today considerable emphasis throughout the world. In response to this need, a major part of the fib Model Code 2005, currently under development, is being devoted to structural conservation and maintenance. More importantly, in recognition of the importance of the seismic threat arising from existing substandard buildings, the first standards for structural upgrading to be promoted by the international engineering community and by regulatory authorities alike are for seismic rehabilitation of buildings. This is the case, for example, of Part 3: Strengthening and Repair of Buildings of Eurocode 8 (i. e. of the draft European Standard for earthquake-resistant design), and which is the only one among the current (2003) set of 58 Eurocodes attempting to address the problem of structural upgrading. It is also the case of the recent (2001) ASCE draft standard on Seismic evaluation of existing buildings and of the 1996 Law for promotion of seismic strengthening of existing reinforced concrete structures in Japan. As noted in Chapter 1 of this Bulletin, fib - as CEB and FIP did before - has placed considerable emphasis on assessment and rehabilitation of existing structures. The present Bulletin is a culmination of this effort in the special but very important field of seismic assessment and rehabilitation. It has been elaborated over a period of 4 years by Task Group 7.1 Assessment and retrofit of existing structures of fib Commission 7 Seismic design, a truly international team of experts, representing the expertise and experience of all the important seismic regions of the world. In the course of its work the team had six plenary two-day meetings: in January 1999 in Pavia, Italy; in August 1999 in Raleigh, North Carolina; in February 2000 in Queenstown, New Zealand; in July 2000 in Patras, Greece; in March 2001 in Lausanne, Switzerland; and in August 2001 in Seattle, Washington. In October 2002 the final draft of the Bulletin was presented to public during the 1st fib Congress in Osaka. It was also there that it was approved by fib Commission 7 Seismic Design. The contents is structured into main chapters as follows: 1 Introduction - 2 Performance objectives and system considerations - 3 Review of seismic assessment procedures - 4 Strength and deformation capacity of non-seismically detailed components - 5 Seismic retrofitting techniques - 6 Probabilistic concepts and methods - 7 Case studies
In recent years knowledge of concrete and concrete structures has increased, as has its applications. New types of concrete challenged scientists and engineers, and ecological constraints encouraged the implementation of life cycle design of concrete structures, moving the focus more and more to maintenance and uprating of structures. And since bui
The superior thermal property of concrete associated to its great capability of thermally insulating the embedded reinforcing steel rebar is the main reason for the good behavior of reinforced concrete structural elements in fire condition, compared to other construction materials. However, at elevated temperatures, concrete still undergoes changes in its mechanical and thermal properties, which mainly cause degradation of strength and may lead to the failure of the structure. Retrofitting is a desirable alternative to rehabilitate post-fire concrete structures. However, in order to ensure safe reuse of fire-exposed buildings and to adopt proper retrofitting methods, it is essential to evaluate the residual strength capacity of fire-damaged reinforced concrete structural elements. The focus of this experimental research study is to investigate the fire performance of reinforced concrete columns exposed to elevated temperatures that followed CAN/ULC-S101 standard fire, and then evaluate their residual compressive strengths after fire exposure. In order to effectively study the fire performance of such columns, eight identical 200 x 200 x 1500mm high reinforced-concrete column test specimens were subjected to two different durations of standard fire exposure (1 hour and 2 hours) while being loaded with two different axial load ratios (20% and 40% of the column ultimate design axial compressive load capacity). In a subsequent stage and after complete cooling down, residual compressive strength capacity tests were performed on the fire-exposed columns. Experimental results showed that the residual compressive strength capacity dropped to almost 50% and 30% of its ambient temperature capacity for the columns exposed to 1- and 2-hour fire durations, respectively. It was also noticed that the applied load ratio has less effect on the column's residual compressive strength compared to that of the fire duration.
Fibre-reinforced polymer (FRP) reinforcement has been used in construction as either internal or external reinforcement for concrete structures in the past decade. This book provides the latest research findings related to the development, design and application of FRP reinforcement in new construction and rehabilitation works. The topics include FRP properties and bond behaviour, externally bonded reinforcement for flexure, shear and confinement, FRP structural shapes, durability, member behaviour under sustained loads, fatigue loads and blast loads, prestressed FRP tendons, structural strengthening applications, case studies, and codes and standards. Contents: .: Volume 1: Keynote Papers; FRP Materials and Properties; Bond Behaviour; Externally Bonded Reinforcement for Flexure; Externally Bonded Reinforcement for Shear; Externally Bonded Reinforcement for Confinement; FRP Structural Shapes; Volume 2: Durability and Maintenance; Sustained and Fatigue Loads; Prestressed FRP Reinforcement and Tendons; Structural Strengthening; Applications in Masonry and Steel Structures; Field Applications and Case Studies; Codes and Standards. Readership: Upper level graduates, graduate students, academics and researchers in materials science and engineering; practising engineers and project managers
Proceedings of the U.S.?Japan Seminar on Post-Peak Behavior of Reinforced Concrete Structures Subjected to Seismic Loads: Recent Advances and Challenges on Analysis and Design, held in Tokyo and Lake Yamanaka, Japan, October 25-29, 1999. Sponsored by the National Science Foundation, U.S.A.; Japan Society for the Promotion of Science; Japan Concrete Institute. This collection presents the latest ideas and findings on the inelastic behavior of reinforced concrete (RC) structures from the analysis and design standpoints. These papers discuss state-of-the-art concrete material models and analysis methods that can be used to simulate and understand the inelastic behavior of RC structures, as well as design issues that can improve the seismic performance of these structures. Topics include modeling of concrete behavior; modeling of RC structures (finite element approach and macro-element approach); and experimental studies, analysis, and design issues.
