Showing papers in "Structure and Infrastructure Engineering in 2005"
TL;DR: In this article, the authors provide guidance for the proper evaluation of existing facilities for continued service, since their focus is on new construction, since current codes of practice provide little guidance for proper evaluation for existing facilities.
Abstract: Civil infrastructure in the United States is at risk from aging, leading to structural deterioration of bridges, buildings, and other facilities from aggressive chemical attack, corrosion, and other physical mechanisms. Decisions regarding maintenance, rehabilitation and other requirements for continued utilization of a facility should be supported by quantitative evidence that aging has not caused structural strength or stiffness to deteriorate to the point where the capacity of the system to withstand or mitigate future extreme events is impaired. Current codes of practice provide little guidance for the proper evaluation of existing facilities for continued service, since their focus is on new construction. Rehabilitation investments should be aimed at maximizing the likelihood of successful future performance at minimum costs. Probabilistic risk analysis methods can provide quantitative tools for the management of uncertainty in condition assessment and are an essential ingredient of risk-informed man...
246 citations
TL;DR: In this paper, the development of reliability-based management of inspection, monitoring, maintenance and repair (IMMR) of various types of offshore structures is described, with a focus on management of hull damage due to crack growth and corrosion.
Abstract: Development of reliability-based management of inspection, monitoring, maintenance and repair (IMMR) of various types of offshore structures is described, with a focus on management of hull damage due to crack growth and corrosion. Operational experiences with respect to degradation of various types of offshore structures are summarized. The interrelation between design criteria and IMMR is emphasized. Explicit design for robustness in terms of an accidental collapse limit state and monitoring by the use of the leak before break principle to identify damage are highlighted. It is shown how design for robustness, choice of inspection method and scheduling as well as repair strategy, need to be implemented to obtain an acceptable risk for various types of offshore structures. Finally, the particular features of reliability based structural reassessment for extension of the service life, are briefly outlined and exemplified.
165 citations
TL;DR: In this paper, a framework for the proper modeling and treatment of each type of uncertainty in the formulation of risk-informed engineering decisions is proposed, which is illustrated with applications to bridges and offshore marine structures.
Abstract: Engineers deal with uncertainties in all their activities, and must often make decisions under conditions of uncertainty and risk. Infrastructures engineering is no exception—design codes are developed to ensure a desired level of safety and performance, or to ensure a specified operational life with a prescribed level of reliability; the required decisions must often be formulated without complete information and thus contain uncertainties. In considering uncertainties, it is important to recognize two broad types; namely, the aleatory type which is associated with natural randomness and the epistemic type which is associated with imperfect knowledge. Proposed here is a framework for the proper modeling and treatment of each type of uncertainty in the formulation of risk-informed engineering decisions. The concepts are illustrated with applications to bridges and offshore marine structures.
121 citations
TL;DR: In this article, the utilization of Markov decision processes as a sequential decision algorithm in the management actions of infrastructure (inspection, maintenance and repair) is discussed, and the use of this approach to determine optimal inspection strategies is described, as well as the role of deterioration and maintenance for steel structures.
Abstract: The utilization of Markov decision processes as a sequential decision algorithm in the management actions of infrastructure (inspection, maintenance and repair) is discussed. The realistic issue of partial information from inspection is described, and the classic approach of partially observable Markov decision processes is then introduced. The use of this approach to determine optimal inspection strategies is described, as well as the role of deterioration and maintenance for steel structures. Discrete structural shapes and maintenance actions provide a tractable approach. In-service inspection incorporates Bayesian updating and leads to optimal operation and initial design. Finally, the concept of management policy is described with strategy vectors.
94 citations
TL;DR: The European Integrated Research Project (EIRP) as mentioned in this paper aims at improved methods for the upgrading of existing railway bridges within the European railway network, aiming to increase the transport capacity by allowing higher axle loads and by increasing the maximum speeds.
Abstract: A European Integrated Research Project has recently been started within the 6th Framework Program of the European Commission. The project aims at improved methods for the upgrading of existing railway bridges within the European railway network. The main objectives of the project are to increase the transport capacity by allowing higher axle loads and by increasing the maximum speeds. Other objectives are to increase the residual lifetime of existing bridges and to enhance management, strengthening and repair systems. The overall goal is to enable the delivery of improved capacity without compromising the safety and economy of the working railway. A consortium consisting of railway bridge owners, consultants, contractors, research institutes and universities will carry out the project, having a gross budget of more than 10 million Euros. Funding from the European Commission covers a major portion of the four-year project costs.
43 citations
TL;DR: In this paper, it is recognized that civil infrastructure systems are essential in providing the range of services generally considered necessary to support a nation's economic well-being and quality of life, and it is of the utmost importance to government, business, and the general populace that these services are sustained over the long term by periodic replenishment of the physical systems that deliver them.
Abstract: It is by now well recognized that civil infrastructure systems are essential in providing the range of services generally considered necessary to support a nation's economic well-being and quality of life. Consequently, it is of the utmost importance to government, business, and the general populace that these services are sustained over the long term by periodic replenishment of the physical systems that deliver them. This has proven challenging for several reasons. First, civil infrastructures do not all lie within the public domain. Second, infrastructures are complex systems that are vulnerable to failures or service degradations in other systems because of their interconnected and interdependent natures. Third, despite the obvious importance of reliable and resilient systems to our collective social, economic, and political well-being, it has been difficult to fund the necessary maintenance and capital improvements. Deciding what levels of reliability should be provided and who should pay for it are ...
40 citations
TL;DR: In this article, a preliminary analysis was performed on the California data set, to quantify the deterioration transition probabilities actually observed, and to determine whether it is yet possible to validate the key assumptions of Markovian bridge deterioration models.
Abstract: Markovian bridge deterioration models have been in use in the United States since the early 1990s, using the AASHTO Guide to Commonly-Recognized Structural Elements. California has one of the oldest databases of inspection history using this standard. A preliminary analysis was performed on the California data set, to quantify the deterioration transition probabilities actually observed, and to determine whether it is yet possible to validate the key assumptions of Markovian bridge deterioration models. Several important conclusions were reached, which should provide guidance for future research and implementation.
38 citations
TL;DR: In this paper, an experimental methodology is proposed for the in situ assessment of possibly deteriorated elastic properties of dam concrete and for the estimation of the local stress state in a concrete dam.
Abstract: In this paper an experimental – numerical methodology is proposed for the in situ assessment of possibly deteriorated elastic properties of dam concrete and for the estimation of the local stress state in a concrete dam. The methodology described herein consists of the following operative stages: excavation of two parallel small holes (instead of the single one generally employed for rock testing); measurements of diameter variations in both holes by dilatometers; combination of experimental tests with computer simulations and inverse analyses for the parameter identification by means of artificial neural networks. Numerical validation tests of this parameter identification methodology are presented and its novelties and potentialities are discussed.
38 citations
TL;DR: In this paper, a non-contact scanning vibration measurement system employing laser doppler vibrometers was proposed to rationalize vibration monitoring in real-scale structures, and the results showed that the return or reflected laser beam quantity depends on subtle differences in the surface condition of a measurement object.
Abstract: In order to rationalize vibration monitoring in structures, this paper addresses a non-contact scanning vibration measurement system employing laser doppler vibrometers. Generally, in the case of measurement for concrete members or dirt-adhering steel members, monitoring by laser doppler vibrometers is extremely difficult due to low laser reflectance. In this study, it is experimentally verified that the return or reflected laser beam quantity depends on subtle differences in the surface condition of a measurement object. Therefore, by searching the vicinity of the insufficient measurement point for the optimum point which provides a maximum reflected laser beam quantity, a remarkable improvement of measuring accuracy for real-scale structures can be achieved. As an example, vibrations of steel girders and reinforced concrete deck of actual bridges are measured, so as to verify the measuring accuracy of the developed system, and eigen local mode shapes of the members are able to be identified.
38 citations
TL;DR: In this article, the first part of the in-situ measurements and data analyses for the tests conducted during backfilling and during service of a long-span corrugated steel culvert railway bridge over Skivarpsan, Rydsgard, Sweden.
Abstract: The paper presents the first part of the in-situ measurements and data analyses for the tests conducted during backfilling and during service of a long-span corrugated steel culvert railway bridge over Skivarpsan, Rydsgard, Sweden. Static and dynamic tests were carried out measuring strains and displacements. Temperature readings were taken along with the measurements. Comparisons of moments during compaction showed that there is good agreement between test results and theoretical values. The theoretical calculation of the rise of the crown during compaction and the crown moments due to live load seem to be conservative, while the theoretical axial forces agree reasonably with the measured axial forces.
24 citations
TL;DR: In this article, the authors present their recent work on load rating of the reinforced concrete T-beam bridge population in Pennsylvania to objectively re-qualify them based on field-testing.
Abstract: There is consensus on the importance of objectively and reliably assessing the condition and load capacity of aged bridges. Although each bridge may be considered as a unique structure, the behavior of many bridge types may be governed by only a few mechanisms and related parameters, especially if a population is constructed from standard designs. By identifying these parameters, and their variation within the population, it is possible to extend findings such as load rating obtained from a statistical sample to the entire population. Bridge type-specific strategies for load rating and condition assessment in conjunction with statistical sampling may therefore offer significant advantages for inspecting and load rating bridges sharing common materials, similar geometry and detailing, and the same critical behavior mechanisms. In this paper, the writers present their recent work on load rating of the reinforced concrete T-beam bridge population in Pennsylvania to objectively re-qualify them based on field-...
TL;DR: In this paper, a theoretical and an experimental approach to determine the inherent damage of a bridge is described, and a fairly precise method to assess the fatigue life cycle of steel bridges is presented.
Abstract: The prediction of a realistic life cycle and the extension of the service life is an important task in reducing costs of civil engineering structures in the future. The paper first gives an overview of the necessary steps of the overall procedure of a precise life cycle assessment. The knowledge of the existing, inherent damage of a structure is an essential prerequisite for life cycle prediction. A theoretical and an experimental approach to determine the inherent damage is described. The paper concludes with the presentation of a fairly precise method to assess the fatigue life cycle of steel bridges. The methods are developed besides others at the Collaborative-Research-Center “Monitoring of Structures” at the Technical University at Braunschweig, Germany.
TL;DR: In this article, a load test carried out on the Luiz I steel bridge in the city of Porto, Portugal is described and some results obtained from the load test and from a short observation period before and after the test are presented.
Abstract: The present article summarizes relevant aspects concerning the monitoring system adopted during a load test carried out on the Luiz I steel bridge in the city of Porto, Portugal. The instrumentation is described and some results obtained from the load test and from a short observation period before and after the test are presented. Additionally, the performance of fibre optic Bragg grating sensors is appraised in measuring field strains and temperatures. The results are compared with those given by using a bridge numerical model, in which some integrity parameters are to be assessed by the monitoring data.
TL;DR: In this article, a bridge management system (BMS) is used to decide when to act and which level of intensity should be used in maintenance/repair/strengthening operations.
Abstract: Bridge Management Systems (BMSs) provide an efficient means of manipulating information about a bridge in order that its long-term health is assured and maintenance programmes can be formulated in line with budgetary constraints and funding limitations However, some weak points remain unsolved and thus limit the possibilities of BMSs Since accurate material deterioration and damage evolution models are not yet fully developed, one of the weaknesses of a BMS is how to decide when to act and which level of intensity should be used in maintenance/repair/strengthening operations A high level of uncertainty is associated with the decision of undertaking these operations as the available deterioration models (chloride ingress, carbonation, alkali – silica reaction) are still not completely accurate due to the many variables involved (environmental, material, loading) Structural monitoring is a possible way of dealing with such a problem Normally, in situ measurements have been used just to update deteriora
TL;DR: In this article, failure probabilities associated with alternative designs of retaining walls are calculated using a formulated approach that accounts for model uncertainty, variable correlation and spatial variability, and failure probabilities are demonstrated through a case study that is based on a real construction project.
Abstract: The uncertainties involved in geotechnical design are considered. Using a formulated approach that accounts for model uncertainty, variable correlation and spatial variability, failure probabilities associated with alternative designs of retaining walls are calculated. Application of this approach is also demonstrated through a case study that is based on a real construction project. The study provides evidence that failure probabilities are significantly influenced by considerations regarding the spatial variability of parameters and the model uncertainty, as well as the adopted statistical modelling of the variables. Furthermore, the study facilitates observations regarding the calibration of codes of practice for the design of retaining walls.
TL;DR: In this paper, an experimental investigation was conducted to strengthen shear deficient reinforced concrete columns using ferrocement jacketing and three scale model specimens, identical to the actual bridge piers, were tested.
Abstract: An experimental investigation was conducted to strengthen shear deficient reinforced concrete columns using ferrocement jacketing. Three scale model specimens, identical to the actual bridge piers, were tested. One of the piers was tested under as-built condition while the other two were strengthened with layers of wire mesh before being tested. All the specimens were subjected to a simulated seismic loading and constant axial load. It was observed from the experimental results that the ferrocement-jacketed specimens exhibited enhanced stiffness, strength, energy dissipation and ductility and the mode of failure changed from brittle shear failure to a ductile flexural failure. The control specimens failed by shear at a relatively low lateral displacement. A finite element model was developed and the results obtained from the numerical analysis compared well with the experimental results. A design methodology for strengthening piers with square/rectangular columns with inadequate shear strength using ferro...
TL;DR: In this paper, the authors discuss many of these issues and their effects on decisions made to manage the state bridge inventory from a practitioner's point of view, and discuss the tradeoffs between many competing interests and conform to numerous constraints.
Abstract: With over 20,000 employees, an annual budget of approximately US$10 billion and the Maintenance and Operations responsibility for over 58,000 lane-miles of highway and over 12,000 bridges, the California Department of Transportation is by most measures a large agency. To be effective, management decisions must constantly assess the tradeoffs between many competing interests and conform to numerous constraints. This paper discusses many of these issues and their effects on decisions made to manage the state bridge inventory from a practitioner's point of view.
TL;DR: The 3rd International IABMAS Workshop on life-cycle cost analysis and design of civil infrastructure systems was held on 24-26 March, 2003, also in Lausanne, Switzerland as discussed by the authors.
Abstract: This article gives an overview of two recent research projects conducted at the Division for Maintenance and Safety of Structures (MCS) at the Swiss Federal Institute of Technology of Lausanne, Switzerland (EPFL) and summarizes the results of the 3rd International IABMAS Workshop on life-cycle cost analysis and design of civil infrastructure systems held on 24–26 March, 2003, also in Lausanne, Switzerland. The two research projects and the Workshop all had the same overarching goal — namely, to improve the consideration of life-cycle costs in bridge decision-making. The research projects investigated the methods of considering multiple limit states in the determination of cost-effective interventions and the methodologies to consider the functioning of the entire network in the determination of management strategies. The Workshop was held to focus future research in the areas of risk-based safety evaluation of structures and infrastructure-related decision-making.
TL;DR: In this article, a novel alternative concept for the development of selectively sensitive excitations, which does not require precise knowledge of the system parameters, was proposed, is discussed and developed, which provides a methodology to improve the condition of the inverse problems by transforming the original problem into a sequence of smaller ones.
Abstract: Life-cycle performance evaluation of structures relies heavily on the usability of measured data. Typically, measurements are utilized to update the state of knowledge about a structure. This usually leads to a system identification problem. Due to the ill-conditionedness of inverse problems, the actual value of the obtained data may be severely reduced. Selective sensitivity provides a methodology to improve the condition of the inverse problems by transforming the original (large) problem into a sequence of smaller ones. The paper discusses this concept and develops a novel alternative concept for the development of selectively sensitive excitations, which does not require precise knowledge of the system parameters.
TL;DR: In this paper, the authors describe innovative bridge decks that have been implemented and describe how they have been used in the construction of bridges and bridges in the Middle East and North America, respectively.
Abstract: For more than a century, important civil engineering structures such as bridges, high-rise buildings, dams and marine platforms have contained iron or steel as the reinforcement for concrete or wood. The useful lives of such structures have often been severely limited by the corrosion of this ferrous component. Much thought has been given in recent years to constructing structures that are lighter, stronger and non-corrosive. These innovative structures are new and for these to be accepted by the engineering community monitoring is mandatory. ISIS Canada has been developing such structures and monitoring them. In this paper, innovative bridge decks that have been implemented are described.
TL;DR: In this article, the performance cycle prediction of reinforced concrete structures involves many factors, which introduce uncertainties, and a probabilistic approach as opposed to a deterministic one is therefore more appropriate to generate reliable cycle predictions.
Abstract: A performance assessment of corroded reinforced concrete (RC) structures requires an acute understanding of both material deterioration and its impact on structural behaviour, in order to evaluate its durability, safety, serviceability and remaining service life. The corrosion phenomenon is usually due to carbon dioxide and chloride ions. More generally, the environmental conditions may determine what kind of deterioration mechanism can produce structural degradation depending on relative humidity, temperature, severity of the surrounding environment, materials properties, etc. Consequently, the performance cycle prediction of reinforced concrete structures involves many factors, which introduce uncertainties. A probabilistic approach as opposed to a deterministic one is therefore more appropriate to generate reliable cycle predictions. This paper focuses on the application of the principles of such a probabilistic approach to calculate for a typical set of RC bridges in France, the critical times corresp...
TL;DR: The Maintenance Information Management System established by Hanshin Expressway Public Corporation (HEPC) is a computerized database and a processing and reference system of all bridge structure elements that helps to plan annual budget allotments and work prioritization using the life cycle cost minimization rule.
Abstract: For efficient management of various structures in a large highway network, systematic handling of data is essential since its volume has swollen over the years and it takes different forms such as diagrams and photos. The Maintenance Information Management System established by Hanshin Expressway Public Corporation (HEPC) is a computerized database and a processing and reference system of all bridge structure elements. As it is a comprehensive application, HEPC is also developing its own version of a bridge management system, which helps to plan annual budget allotments and work prioritization using the life cycle cost minimization rule. Both systems are tools to support a rational decision-making process of maintenance/repair programmes under the recent curtailed financial situation.