土木工程毕业设计外文翻译2.pdf

JOURNAL OF ENGINEERING MECHANICS JULY 2000 711 ISSUES ININFRASTRUCTUREHEALTHMONITORING FORMANAGEMENT By A E Aktan 1F N Catbas 2K A Grimmelsman 3and C J Tsikos4 ABSTRACT The most critical issues that have been identifi ed as being needed to implement meaningful and benefi cial applications of health monitoring for infrastructure management are discussed Issues related to infra structure health monitoring for management can be defi ned in three overlapping categories In this context engineering tools methods and knowledge should be developed and utilized to answer societal and educational aspects of the problem while taking advantage of the information tools and methodologies available today The need for integrated research education and practice for infrastructure management is emphasized The challenges in the integration of intelligent transportation and structural systems concepts within an optimum integrated asset management framework are described and illustrated Examples from ongoing research on the health monitoring of short span bridge families and long span bridges are presented to illustrate the issues INTRODUCTION We defi ne health monitoring as the measurement of the op erating and loading environment and the critical responses of a structure to track and evaluate the symptoms of operational incidents anomalies and or deterioration or damage indicators that may affect operation serviceability or safety reliability The intrinsic payoff in integrated operational and structural health monitoring is signifi cant In this context health moni toring is analogous to human health management serving as the backbone of an integrated asset management program at the systems level for civil infrastructure as discussed below Fig 1 depicts that infrastructure health monitoring requires various strategies and specialized diagnostic tools depending on where a facility may be in its life cycle and whether an event or symptom triggers a routine or an in depth checkup just as in medical health management Civil engineers have been applying heuristic forms of health monitoring through visual inspection to certain classes of pub lic civil structures such as highway bridges and river naviga tional facilities Also notable is the advent of many intelligent transportation system ITS technologies and signifi cant invest ment in closed circuit television cameras sensors hardware and software for operational monitoring of critical stretches of roadways tunnels and intersections However integrating the operational and structural health monitoring of bridges espe cially long span bridges and those that constitute critical nodes within a transportation system has not been attempted The is sue is to transform the current practice to a more rational and effective one while integrating operational and structural health monitoring thereby providing objective accurate and suffi ciently comprehensive data to serve as a basis for reliable eval uations projections and forecasts In this manner the advan tages that are expected from applying an asset management approach to civil infrastructure might be realized Ultimate Goal and Long Term Promise The ultimate goal that promises the maximum payoff and justifi es the investment required for meaningful health moni 1John Roebling Prof Dir Drexel Intelligent Infrastructure and Transp Safety Inst D13 Drexel Univ Philadelphia PA 19104 2Res Asst Prof Drexel Intelligent Infrastructure and Transp Safety Inst DI3 Drexel Univ Philadelphia Pa 3Assoc Res Engr Drexel Intelligent Infrastructure and Transp Safety Inst DI3 Drexel Univ Philadelphia PA 4Assoc Dir Drexel Intelligent Infrastructure and Transp Safety Inst DI3 Drexel Univ Philadelphia PA Note Special Editor Roger Ghanem Discussion open until December 1 2000 To extend the closing date one month a written request must be fi led with the ASCE Manager of Journals The manuscript for this paper was submitted for review and possible publication on February 25 2000 This paper is part of the Journal of Engineering Mechanics Vol 126 No 7 July 2000 qASCE ISSN 0733 9399 00 0007 0711 0724 8 00 1 50 per page Paper No 22239 toring research and development is the implementation of an integrated asset management approach to infrastructure sys tems For example bridges and retaining structures pave ments roadways traffi c control and safety systems are intertwined infrastructure components of an aggregate trans portation system These components are also subject to inter action with traffi c organizational and social systems Net work level integrated management of a transportation system offers substantial cost effectiveness through a systemwide op timization of operational performance and life cycle preser vation The advantages expected from asset management nat urally depend on data information and knowledge to serve as a foundation for reliable projections and forecasts The fi rst prerequisite for effective integrated asset manage ment is an accurate and complete understanding and character ization of the interacting systems with all the critical parameters affecting component and individual system performances Sec ond objective data on the current condition of various assets and a realistic understanding of their depreciation under various maintenance and renewal scenarios is needed Third the ability to evaluate the payoff potential of various investment scenarios is required For example to estimate the payoff from investing in different systems or regions of a network the corresponding changes in the performance of affected system components and sound temporal projections of the asset conditions social and environmental impacts corresponding to various investment sce narios would be needed Objectives and Scope of Paper The writers have been exploring effective approaches to ed ucation research and technology demonstrations in civil in frastructure systems engineering They have taken advantage of the signifi cant synergy intrinsic in effectively integrated and coordinated teams from academe government and industry and various engineering and nonengineering disciplines Such teams inevitably take a holistic approach to research First a wide array of analytical experimental and information tools were integrated within a systems identifi cation and integration approach Second actual operating or decommissioned civil infrastructure systems and components represented by high way bridges were studied and several were tested to controlled damage and failure This enabled an understanding of the prevalent issues and the data information and knowledge lim its that obstruct effective technology demonstrations in infra structure systems Such an integrated and holistic systems level approach to research revealed complex interactions of natural societal and mechanical built systems Aktan et al 1998a c and led to a better identifi cation of the prevailing issues affecting health monitoring The objective of this paper is to present and discuss the most critical issues the writers have identifi ed as needing res olution in order to implement meaningful and benefi cial ap 712 JOURNAL OF ENGINEERING MECHANICS JULY 2000 FIG 1 Analogy between Human and Infrastructure Health Monitoring plications of health monitoring The challenges in the integra tionofintelligenttransportationandstructural systems concepts within an optimum integrated asset management framework will be described and illustrated Examples from ongoing research on the health monitoring of short span bridge families and long span bridges will be presented to illustrate the issues GLOBAL ISSUES Societal and Educational Aspects of Problem Rigorous research approaches nonconventional thought processes and tools that are currently outside the realm of traditional civil engineering are needed to effectively study civil infrastructure systems related problems In 1998 the Na tional Science Foundation NSF Washington D C awarded a grant for establishing a National Institute for Civil Infrastruc ture Systems to New York University s School of Government New York perhaps as an experiment to seek the most effective organization and leadership for consensus between the very large number of stakeholders NSF 1997 There is no unique manner of integrating disciplines however the dynamics of coordinated research and development focused on a major so cietal problem through the participation of many individuals from academe government and industry and how such a team may accomplish the production of successful meaningful re search products should be considered as a major research area by itself Research to Education to Practiceand Terminology It is recognized that advancing infrastructure systems re search education and practice cannot be accomplished just by civil engineers or just by engineers in general There is a need for a new educational paradigm to transform engineering ed ucation to one that can effectively address the lack of an in dustry and workforce capable of taking ownership of the prob lem There have been efforts by many educators programs organizations and institutions to improve civil engineering ed ucation Pennoni 1992 Yao 1996 Moore et al 1998 Initia tives for systemic change in engineering education have been issued by NSF to educate professionals who can more effec tively function at the intersection of the natural societal and mechanical environments NSF 1996 The need for consensus by all stakeholder groups should be recognized as the best approach to infrastructure education re form For example federal and state legislatures agencies and stakeholders have been quite effective in dealing with seismic risk in the western United States through the National Earth quake Hazards Reduction Program legislation Civil engineers have taken the lead in earthquake engineering research edu cation and practice since the 1950s leading to the current crop of capable professionals Shortcomings of infrastructure per formance and its ineffective management may be costing the nation as much as or more than a major natural disaster every other year pointing to the need to undertake a similar ap proach to advancing the state of the art in education research and practice of infrastructure management Matalucci 1997 A related issue regards consensus defi nitions terminology and expectations from infrastructure health monitoring that are currently lacking For example the following terms are com monly used by practicing engineers in the highway transpor tation systems area inspection visual arms length in depth nondestructive evaluation NDE bridge testing condition rat ing load rating inventory operating permit maintenance management rehabilitation and replacement The following is some of the terminology used by many engineers in infrastruc ture research structural identifi cation condition assessment deterioration science durability damage detection capacity and reliability evaluation health monitoring integrated asset management renewal engineering and smart materials and systems Clearly there is a need for clarifi cation of the rela tionships between the terminology used by researchers and practitioners Organizational Issues Institutional effectiveness and productivity has been identi fi ed by NSF 1989 as a strategic research area for improving infrastructure performance In the last decade many state and local infrastructure agencies have been going through reorgan ization or reengineering however considerable differences re main in the policies and practices of most DOTs The process of reorganization of an infrastructure agency should take into JOURNAL OF ENGINEERING MECHANICS JULY 2000 713 FIG 2 Design Performance and Organizational Systems for Highway Bridge Engineering consideration the basic product i e the infrastructure system as opposed to just following a business model To illustrate consider Fig 2 which compares the design performance and organizational systems related to typical highway bridges In most DOTs that go through reengineering integration of con struction design maintenance and operation divisions and bridge pavement and ITS bureaus may not be considered to be a major requirement However the detachment between design performance and organizational systems as illustrated in Fig 2 may be a major impediment to the institutional ef fectiveness of most infrastructure agencies ISSUES RELATED TO INFORMATION TOOL AND METHODOLOGIES Integrative Information Systems Integrated asset management is predicated on the design and development of integrative systems that literally will merge the transportation and information highways Such systems are also a prerequisite for effective health monitoring Information systems that will serve for future civil infrastructure systems management will have to take advantage of the existing data information and knowledge on all critical assets Because such material typically exists in disconnected and nonrelational da tabases the information systems will have to integrate legacy data with objective fi eld data collected through the application of technologies being developed for ITSs Currently most as sets are not linked or integrated and there may be signifi cant variation in the confi dence interval and objectivity of legacy data representing the condition and performance of various asset classes Contemporary data acquisition presentation analysis and archival approaches do not offer true location independent real time data acquisition retrieval organization display or analysis applications because of this lack of inter connectivity Integrative information systems the main feature of which is depicted in Fig 3 are envisioned to serve as the cement for new and objective data and information to be retrieved from relevant components throughout the critical locations of an infrastructure system such as the entire transportation system or an electric power grid in real time and with a fi ne spatial distribution Such systems would acquire and provide on de mand real time data to administrators engineers researchers operators enforcement offi cials and the public A kernel console of an integrative information system for asset management using a geographic information system as a foundation is depicted in Fig 4 In this system real time information coming from many sources and locations regard ing the assets and resources is integrated with legacy infor mation and identifi ed organized evaluated and analyzed Transportation authorities have already invested signifi cant re sources into cameras sensors scales message signs pass sys tems and hardware software for ITS applications However the information gathered by these devices is not integrated presented or accessible to all users who can take advantage of the data To realize the payoff promised by ITS it is es sential to advance the information technology aspects of cur rent implementations Integrative information systems would help provide on line access to data the integration and syn chronization of data from various sources and the develop ment of graphical interfaces and applications software to fa cilitate the analysis design and interpretation of the data Most importantly an integrative information system would further be integrated with a heuristic knowledge base and pos sess a certain level of intelligence so that many modes and frequencies of data streaming from many nodes of a large net work may be preprocessed and operators are alerted if inci dents or anomalies requiring human intervention are diag nosed Otherwise it is not realistic to expect even well trained human operators to successfully recognize all critical incidents and events in a timely manner We note several examples of integrative information systems with artifi cial intelligence in cluding battle systems employed by the U S Navy and U S Air Force and systems employed by air traffi c controllers The information issues are discussed further below in relation to information technology needs for health monitoring Information Integration and Interpretation Information integration fusion in health monitoring is crit ical for reliable interpretation of data and information from health monitoring Information integration is closely depen dent on how data is transformed to information During the design and execution of any experiment it is critical to design 714 JOURNAL OF ENGINEERING MECHANICS JULY 2000 FIG 3 Distributed Database Architecture and Network Topology FIG 4 Console for Integrative Information System for Asset Management the sensors data acquisition data processing and archiving or warehousing in conjunction with the design of information fu sion presentation display and interpretation The complexity of the data that must be obtained from an integrated opera tional and structural health monitor is illustrated in Fig 5 This fi gure illustrates a data space permitting conceptualization of the wide spectrum of spatial temporal and frequency and modality characteristics of data that would have to be man aged Along the temporal axis in Fig 5 characteristics may range from real time to proxy data For example a real time image is required for incident detection whereas data in historic ar chives going back to the initial construction of a 100 year old bridge may be needed for its preservation To fully understand the impact of seasonal changes of temperature on the accu mulation of intrinsic forces in a bridge one would need to examine data collected over decades to account for events such as El Nin o that may signifi cantly affect the climate Along the spatial axis in Fig 5 the data may relate to an image or strain measurement at a critical weld several inches long or to the measurement of wind velocity and direction characteristics along a wide valley that may extend for many miles If the operation of a transportation network encom passing a 30 km2region were monitored a large number of cameras and temperature sensors would be nee