Performance Based Methods for Service Life Prediction
Reports compiled by CIB W080 / RILEM 175-SLM Service Life Methodologies Prediction of Service Life for Buildings and Components
CIB Report: Publication 294
State of the Art Reports Part A Part B Author: Author: Per Jostein Hovde Konrad Moser
ISBN: 90-6363-040-9
March 2004
Copyright © 2004 by CIB, NTNU and EMPA CIB W080 / RILEM 175 SLM Service Life Methodologies Prediction of Service Life for Buildings and Components
Task Group Performance Based Methods for Service Life Prediction
State of the Art Reports
PART A FACTOR METHODS FOR SERVICE LIFE PREDICTION
PER JOSTEIN HOVDE
PART B ENGINEERING DESIGN METHODS FOR SERVICE LIFE PREDICTION
KONRAD MOSER
March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies State of the Art Reports ii
Preface
The State of the Art Reports on methods of service life prediction have been arranged in two parts: A (Factor methods) and B (Engineering design). Each part, individually authored, is self-contained and includes a title page, table of contents, summary, and references and may contain additional information (e.g., preface, abbreviations). References are provided in author date style and are exclusive to the Part in which they are used – they have not been cross-referenced. In order that reference can be made to a specific Table or Figure in the text, these items have been enumerated using a prefix of either A or B pertaining the part in which they are presented. Finally, pagination is continuous over the two parts. CIB W080 / RILEM 175 - SLM: Service Life Methodologies State of the Art Reports iii
Overview of Reports
Considerable work has been carried out in the area of service life prediction as requisite tools for helping assess long-term environmental effects, for maintenance management of infrastructure systems, such as roads, bridges, waterways, water distribution and waste-water removal systems, or indeed for maintenance of building envelope systems, envelope components and related materials. Increasingly, building material and component manufacturers are seeking systematic methods to assess the likely risk to premature deterioration of existing products given specific climatic effects, or the most vulnerable exposure conditions of new products in specified systems. The current joint CIB / RILEM technical committee (CIB W080 / RILEM TC 175-SLM) on methods of service life prediction of building materials and components was created in September 1996. Prior to this, the joint CIB W080 / RILEM Committees (71-PSL, 100-TSL and 140-TSL) have been responsible for a preparing a series of useful working documents as well as co-ordinating the efforts required to bring about nine international symposia related to durability and service life issues and a tenth being planned for 2005 in Lyon, France. The number of significant contributions collectively presented in these conference proceedings provides a substantial depth of knowledge to the field. Full utilization of this body of knowledge for the benefit of manufacturers of building materials and components, designers, specifiers, constructors, as well as asset and property managers, requires the development of suitable guides and related information. It is the aim of CIB W080 working jointly with the RILEM 175-SLM, to help develop the necessary guides, methods, and techniques that will enable practitioners to select the appropriate tools to predict service life. To achieve this aim, the focus of the technical committee is on integrating existing prediction and service life techniques, tools, and methods. This publication comprises two parts of a State-of-the-Art report on performance-based methods of service life prediction. A task group to develop the reports was established over the course of the committee meeting held in Vancouver, Canada in June 1999. The objectives of the task group were defined during were to: • Develop performance based methods for service life design based on models of degradation and environmental actions • Develop a fundamental and scientific approach and provide framework for different levels of design • Provide simplification of scientific models to engineering design • Develop a simplified and practical design approach (“factor method”) The work item was divided into three sub-tasks that focused on different approaches to service life prediction and included: Sub-task 1 "Probabilistic" (also referred to as ‘theoretical’ and ‘stochastic’) Sub-task 2 "Engineering approach" Sub-task 3 "Factor method" Of the three sub-tasks undertaken in 1999, reports for sub-tasks 2 and 3 (“Engineering approach" and “Factor method” respectively) are provided in this publication (Parts B and A CIB W080 / RILEM 175 - SLM: Service Life Methodologies State of the Art Reports iv respectively). The third sub-task, “Probabilistic”, will perhaps be made available at a later date, but was incomplete at the time of publication. The following provides a brief synopsis of the contents of each report in the order in which they are presented in the publication. Part A: P. J. Hovde — Factor Methods for Service Life Prediction Sub-task item 3 — “Factor method” The Factor method is one that has been promoted in the AIJ (Japanese) Guide for Service Life Planning of Buildings as well as in the subsequent ISO standard 15686-1 on Service Life Planning. Although this method has been suggested as an alternate means of estimating service life of components and materials, previous use of this method has not been documented. The State-of-the-Art report prepared for this publication contains the development, evaluation and use of factor methods for service life prediction as it is presented in ISO standard 15686-1. The introduction and background information provide a review of activities over the past decade that address the need for service life prediction tools given the increased focus on sustainable construction both internationally and on a national level. Mention is made of international standardization with ISO as well as the harmonization within the building and construction sector of the EC. Part B: K. Moser — Engineering Design Methods for Service Life Prediction Sub-task item 2 — “Engineering approach” The scope of the sub-task item included the following steps. • Gain an overview on the main methods applied to research and large engineering projects using a scientific approach. These methods often apply mathematical models and stochastic processing to the design data. • Investigate possible modifications to the Factor method that enhances the scientific basis for the method. • Define as to what an "engineering method" should be in terms of complexity of models applied and type and amount of data employed. • Propose one, or several engineering design methods preferably developed on and applied to typical case studies. The sub-task report provides a literature review and an appraisal of the state of the art. Three examples are shown to illustrate the proposed procedure for different basic equations and different quality of input data. These reports represent the most recent advances in regard to the use of the “factor method” and related “engineering” methods to establish the service life of building materials and components. They provide useful background information on their development and offer practical approaches to the use of either method of service life prediction. These represent a valued contribution to the collection of practical technical information on service life prediction.
Chair/Coordinator CIB W080 /RILEM 175-SLM Michael A. Lacasse CIB W080 / RILEM 175 - SLM: Service Life Methodologies State of the Art Reports v
Acknowledgements
These reports have been compiled over the course of the 1999-2003 work programme of the CIB W080 /RILEM 175-SLM Commission and the authors are indebted to the many within the Task Group who made contributions, offered advice, to those who assisted in the review of the documents, and as well to those who helped prepare the final version of the reports. The CIB W080 /RILEM 175-SLM Commission is likewise particularly grateful to the Norwegian University of Science and Technology and the Swiss Federal Laboratories for Materials Testing and Research for having unreservedly supported the Task group leaders in their endeavours over these years.
FACTOR METHODS FOR SERVICE LIFE PREDICTION State of the art
March 2004
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CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 2
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 3
PREFACE
This report presents a state-of-the-art regarding the development, evaluation and use of factor methods for service life prediction, specifically the factor method presented in ISO 15686 Part1. Most of the report describes the background and development of the factor method, and some theoretical evaluation of the method. This may form a basis for further evaluation and implementation of factor methods as a simple and practical tool for estimation of service life of materials and components of buildings in the design and engineering phases.
The technical approach to the development of the ISO factor method is not rigorous. It is in fact highly empirical and may be limited to specific types of building components (materials) used in specific contexts and under expected environmental conditions. This is to some extent emphasized throughout the report. However, the report mainly gives an overview of the development being presented, without giving a more comprehensive explanation and discussion of the factor method. This may be a task for future work.
More recently, some projects have been carried out regarding practical application of the factor method. This seems to be an increasing activity around the world, and the challenge for the future will be to apply the factor method to estimate the service life of a wide variety of materials and components in buildings, in order to present the method and obtain real experience of how it works in practice and how it can be applied during the design and engineering phases of a building. This creates an immediate need for input data, both for reference service lives of materials and components, as well as practical values of the different factors included in the method.
October 2003 Per Jostein Hovde
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 4
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 5
CONTENTS
SUMMARY 7
1. INTRODUCTION 9
2. BACKGROUND 11
3. THE NEED FOR SERVICE LIFE PREDICTION TOOLS 15
4. GENERAL REQUIREMENTS FOR 21 SERVICE LIFE PREDICTION METHODS
5. DESCRIPTION OF FACTOR METHODS 29
5.1 Development of factor methods for service life prediction in Japan 29 5.2 A factor method for evaluation of surface treatment of wooden 31 windows and doors 5.3 Factor method for estimation of service life of components and 32 assemblies as presented in ISO 15686 Part 1
6. EVALUATION OF FACTOR METHODS 35
7. APPLICATION OF FACTOR METHODS 41
8. FURTHER DEVELOPMENT OF FACTOR METHODS 47
REFERENCES 49
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 6
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 7
SUMMARY
This report contains a state-of-the-art regarding development, evaluation and use of factor methods for service life prediction, especially the factor method presented in ISO 15686 Part1.
Chapter 1 and 2 give a short introduction and a background, respectively. In chapter 2, some important activities are described that have taken place during the last decade regarding the increased focus on sustainable development and the need for service life prediction tools, both internationally and on a national level. The international cooperation of standardization within ISO and the harmonization within the building and construction area in Europe is mentioned.
Chapter 3 contains some examples in which the need for service life prediction is explained. Four different tables expressing design lives for different categories of buildings are provided.
In chapter 4 some general requirements are presented that have been set up for service life prediction methods. There are needs on different levels of sophistication and for different purposes, and it is shown that service life prediction is encumbered with considerable uncertainties and that it is not an exact science.
Chapter 5 contains a description and explanation of different factor methods, including the method described in ISO 15686 Part 1.
Chapter 6 contains an evaluation of factor methods. So far, this is mainly based on theoretical considerations, since the ISO factor method has not been used very much in practice.
In chapter 7, some examples of application of the ISO factor method are given. Some of the examples are theoretical in the way that they show how the use of factor methods can be incorporated in design for durability and development of sustainable buildings. There are also a few examples of specific application of the ISO factor method for service life prediction of buildings or building components (facades, windows).
Chapter 8 contains some important aspects regarding further development of factor methods.
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 8
NTNU – Norwegian University of Science and Technology Department of Civil and Transport Engineering March 2004 CIB W080 / RILEM 175 - SLM: Service Life Methodologies Factor Methods: State of the Art 9
1. INTRODUCTION
Buildings and the built environment represent a major amount of the national real capital in different countries. During the last century, there have been extensive construction activities, and the existing building stock represents a great value that requires continuous investments regarding management and maintenance as well as repair and replacement.
Durability is one of the most important issues in the building and construction area, as it influences the following aspects of building materials, components, buildings and structures: