Service Life Estimation and Extension of Civil Engineering Structures

Vistasp M. Karbhari, L S Lee

• Publisher: Woodhead Publishing
• Year: 2010
• eBook ISBN: 9780857090928
• Topic: Technologie et ingénierie
• Subtopic: Ingénierie civile

Service life estimation is an area of growing importance in civil engineering both for determining the remaining service life of civil engineering structures and for designing new structural systems with well-defined periods of functionality. Service life estimation and extension of civil engineering structures provides valuable information on the development and use of newer and more durable materials and methods of construction, as well as the development and use of new techniques of estimating service life.Part one discusses using fibre reinforced polymer (FRP) composites to extend the service-life of civil engineering structures. It considers the key issues in the use of FRP composites, examines the possibility of extending the service life of structurally deficient and deteriorating concrete structures and investigates the uncertainties of using FRP composites in the rehabilitation of civil engineering structures. Part two discusses estimating the service life of civil engineering structures including modelling service life and maintenance strategies and probabilistic methods for service life estimation. It goes on to investigate non-destructive evaluation and testing (NDE/NDT) as well as databases and knowledge-based systems for service life estimation of rehabilitated civil structures and pipelines.With its distinguished editors and international team of contributors Service life estimation and extension of civil engineering structures is an invaluable resource to academics, civil engineers, construction companies, infrastructure providers and all those with an interest in improving the service life, safety and reliability of civil engineering structures.- A single source of information on the service life of reinforced concrete and fibre-reinforced polymer (FRP) rehabilitated structures- Examines degradation mechanisms in composites for rehabilitation considering uncertainties in FRP reliability- Provides an overview of probabilistic methods for rehabilitation and service life estimation of corroded structures

Part I

Using fibre reinforced polymer (FRP) composites to extend the service life of civil engineering structures

1

Key issues in the use of fibre reinforced polymer (FRP) composites in the rehabilitation and retrofitting of concrete structures

L.C. Hollaway, University of Surrey, UK

Abstract:

Fibre reinforced polymer (FRP) composites were first used in the building industry during the late 1960s to construct all-composite buildings; also at this time, the construction industry proposed that rebars for reinforcing concrete should be made from composite materials and prestressing tendons for concrete beams should also be manufactured from FRP composites. However, it was not until the mid-1980s that a few research/design teams throughout the world seriously investigated the use of composites to prestress concrete beams and to utilise the material in conjunction with the more conventional materials. FRP composites were seen at that time as materials with a high strength and stiffness and to have a high corrosion resistance; they could be tailored to any design requirement but their high cost was a drawback to their use. In addition, the attitude of the civil engineering industry generally was against the materials but in the late 1980s, composite materials started to have their first major successes in the field of flexural and shear strengthening and seismic retrofitting of degraded concrete structures. This initial thrust has now been extended to areas such as confining concrete columns and strengthening beam/column joints, but in spite of this FRP composites have not yet been fully accepted by all areas of the civil engineering industry. In the strengthening and seismic retrofitting area of civil engineering, the cost of the FRP material is only a relatively small percentage of the overall cost for the work, and because of its physical properties, its fabrication on site can be undertaken much more speedily than if a more conventional material were to be used. Its low weight has an economic benefit in decreasing the erection time and reducing any costly closure period of the highway.This chapter discusses the mechanical and in-service properties of advanced polymer composite materials and their components, their long term loading characteristics and the manufacturing techniques available for use, specifically in terms of rehabilitation and retrofitting of reinforced and prestressed concrete structures. It considers the preparation of the surfaces of the concrete, and of the polymer composite plate, and suggests ways of joining the plate to the adherend. Finally, it anticipates future trends in the field of upgrading structural members.

Key words

rehabilitation

retrofitting

fibre reinforced polymer

speed

1.1 Introduction

The rehabilitation and retrofitting of reinforced concrete (RC) and pre-stressed concrete (PC) structures utilising advanced polymer composites (in the construction industry these materials are referred to as fibre reinforced polymer (FRP) composites) are now well established techniques. Over the last three decades, externally-bonded FRP composite strengthening has been shown to be particularly attractive and it has many advantages, including the light weight and strength of the FRP laminates. Furthermore, the ease of handling and installation techniques without heavy equipment include a simple application in overhead installations where the viscosity of the epoxy adhesive is sufficient to support the self-weight of the FRP strips during curing. (However, the author would not recommend this procedure except under very special circumstances.) The strips can cross other FRP laminate strips, with adjustments in the thickness of the epoxy adhesive layer. In addition, the fabrication technologies for the production of FRP composites have been revolutionised by sophisticated manufacturing techniques. These methods have enabled polymer composite materials to produce good quality laminates with minimal voids and accurate fibre alignment.

This chapter will discuss: (i) The composite materials and their component parts used in the civil infrastructure, (ii) the mechanical, in-service and physical properties of composite materials, (iii) the different manufacturing methods for the FRP composites specifically for the techniques of rehabilitation and retrofitting, and the influence that the various methods have on the FRP composites’ mechanical and in-service properties, (iv) the rehabilitation of RC and PC flexural and shear structural members and the failure modes of the upgraded structural systems, and (v) the retrofitting of RC columns.

1.2 Key issues affecting composite use in construction

For 40 years following the Second World War, the construction industry suffered from a lack of investment, and by the early 1990s there was a serious decline in that industry in both the United States and Britain. The construction industry was regarded as low technology, low skill and labour intensive compared with most other industries. Although economic factors were the main cause of this decline, which meant that methods and materials had changed little over the 40-year period, other underlying factors were believed to include the industry’s widespread over-reliance on the use of litigation and arbitration to settle disputes and claims regarding ‘value for money’. The concern over the lack of investment, performance and productivity of the UK construction industry led the UK Government to commission Sir Michael Latham (Latham, 1993) to investigate the procurement and contractual relations within, and the structure of, the construction industry. It was reported that disputes and conflicts had taken their toll on moral and team spirit and that defensive attitudes were commonplace. Following this report, Latham lead a year-long enquiry with the aim of ending ‘the culture of conflict and inefficiency that dogs Britain’s largest industry’. The second Latham Report, which was published in 1994, concluded that the traditional methods of procurement and contract management and its adversarial culture caused inefficiency and ineffectiveness within the industry. The Latham Reports set the agenda for reform and gave the industry targets. Whilst these reports were widely welcomed, the implementation of their recommendations was perceived to be slow and, as a result, the UK Government established the Construction Task Force, led by Sir John Egan (1998). The Egan Report, ‘Rethinking Construction’, (commissioned by John Prescott, the deputy Prime Minister at the time) was published in 1998 and acknowledged that its foundation was the Latham Report.

The report concluded that there was ‘growing dissatisfaction with construction among both private and public sector clients. Projects are widely seen as unpredictable in terms of delivery on time, within budget and to the standards of quality expected’. The Report saw a need for a change of style, culture and process in the construction industry. To this end, it identified five areas that needed to be in place to secure improvement in the industry, namely, committed leadership, focus on the customer, integrated processes and teams, quality-driven agenda, and commitment to people. Within these areas, the need for partnering and sharing of risk between contractor and client was identified.

The findings and conclusions of the Latham and Egan Reports are reflected in the ‘Strategic Forum for Construction Report’ (2001); these findings are now being implemented by the Government.

These discords within the construction industry were responsible for the lack of investment in research and development and for the practical methods of operation and the materials used in the construction industry changing little over the 40-year period after the Second World War. These problems resulted in a complete lack of interest by the plastics/composites industry in the civil engineering sphere, where the possibility of utilising new materials and therefore market opportunities were not visible to potential investors. By contrast, the use of composites technology in aircraft applications and the use of fibre reinforced polymers in boat hulls and c...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Introduction
• Part I: Using fibre reinforced polymer (FRP) composites to extend the service life of civil engineering structures
• Part II: Estimating the service life of civil engineering structures
• Index