Showing papers in "Structure and Infrastructure Engineering in 2016"
TL;DR: A brief overview of the recent research achievements in the field of life-cycle engineering for civil and marine structural systems is presented in this paper, where the authors indicate future dire threats of structural degradation due to ageing, mechanical stressors, and harsh environment.
Abstract: Structural systems are under deterioration due to ageing, mechanical stressors, and harsh environment, among other threats Corrosion and fatigue can cause gradual structural deterioration Moreover, natural and man-made hazards may lead to a sudden drop in the structural performance Inspection and maintenance actions are performed to monitor the structural safety and maintain the performance over certain thresholds However, these actions must be effectively planned throughout the life-cycle of a system to ensure the optimum budget allocation and maximum possible service life without adverse effects on the structural system safety Life-cycle engineering provides rational means to optimise life-cycle aspects, starting from the initial design and construction to dismantling and replacing the system at the end of its service life This paper presents a brief overview of the recent research achievements in the field of life-cycle engineering for civil and marine structural systems and indicates future dire
209 citations
TL;DR: In this paper, full-scale tests are conducted to determine the ultimate bearing capacity of continuously jointed segmental tunnel linings, considering changes of the surrounding environment, and the design of tested linings and loading schemes are described.
Abstract: The serviceability of segmental tunnel linings is attracting more and more attention within the operation of urban rail traffic. Full-scale tests are herein conducted to determine the ultimate bearing capacity of continuously jointed segmental tunnel linings, considering changes of surrounding environment. The design of tested linings and loading schemes are described. The most important results are the evolution of deformations, cracking and opening of joints and forces in bolts. The bearing capacity, role of joint bolts and failure mechanism of the tested linings are analysed. It is found that failure of these linings is caused by the failure of joints. Thus, in order to optimise structural design of tunnel linings, more attention needs to be paid to maximise the joint strength. It is also found that circumferential joint bolts could take action and offer the safety margin in connection with the response of segmental structures. What’s more, a comparison of different experimental loading conditi...
125 citations
TL;DR: The sensitivity analysis of the proposed model indicates that construction defect, overload, mechanical damage, bad installation and quality of worker are the most significant causes for the O&G pipeline failures.
Abstract: Safety assessment of oil and gas (O&G) pipelines is necessary to prevent unwanted events that may cause catastrophic accidents and heavy financial losses. This study develops a safety assessment model for O&G pipeline failure by incorporating fuzzy logic into Bayesian belief network. Proposed fuzzy Bayesian belief network (FBBN) model explicitly represents dependencies of events, updating probabilities and representation of uncertain knowledge (such as randomness, vagueness and ignorance). The study highlights the utility of FBBN in safety analysis of O&G pipeline because of its flexible structure, allowing it to fit a wide variety of accident scenarios. The sensitivity analysis of the proposed model indicates that construction defect, overload, mechanical damage, bad installation and quality of worker are the most significant causes for the O&G pipeline failures. The research results can help owners of transmission and distribution pipeline companies and professionals to prepare preventive safety...
124 citations
TL;DR: In this paper, an updated macro-model, based on the equivalent pin-jointed diagonal compressive strut, is presented, which is able to represent the stiffening effect of the infill panel with openings by taking into account both the size of the opening and the vertical load acting on the frame.
Abstract: During the last decades, several macro-models have been proposed for the modelling of the infill panels' contribution to the lateral strength of frames Despite all this effort, a robust model, which takes into account the influence of the vertical load, is not yet available Furthermore, the influence of the very common case of infill walls with openings, such as windows and doors, has been neglected in all the code provisions that have been published so far In this paper, an updated macro-model, based on the equivalent pin-jointed diagonal compressive strut, is presented The proposed macro-model is able to represent the stiffening effect of the infill panel with openings by taking into account both the size of the opening and the vertical load acting on the frame Detailed and in-depth parametrical investigation, based on finite element analysis, shows that the proposed mathematical macro-model can be used as a reliable and useful tool for the determination of the equivalent compressive strut width since it accounts for a large number of parameters, which are not generally accounted for by the already available models in the literature
101 citations
TL;DR: In this article, a critical review of the experimental studies that have been carried out and of the assessment approaches developed in the last three decades to assess the life expectancy of masonry arch bridges is provided.
Abstract: Masonry arch bridges constitute a significant proportion of European road and rail infrastructures. Most of them are well over 100 years old and are supporting traffic loads many times above those originally envisaged. The inherent variation in their constituent materials, the traditional design criteria and methods used for their construction, their deterioration over time caused by weathering processes and the development of other defects, significantly influence the mechanical response of these historic structures. A deep understanding on the numerous factors that affect the structural behaviour of masonry arch bridges and on the analysis methods to assess the life expectancy of such bridges and inform maintenance and strengthening strategies is essential. This paper provides a critical review of the experimental studies that have been carried out and of the assessment approaches that have been developed in the last three decades to these aims. The current knowledge is established and areas of ...
96 citations
TL;DR: In this paper, the authors present the formulation of maintenance in asset intensive organizations, as breakdowns can have an impact on the capacity, quality and cost of operation of an organization.
Abstract: Maintenance can represent a significant portion of the cost in asset intensive organisations, as breakdowns have an impact on the capacity, quality and cost of operation. However, the formulation o ...
91 citations
TL;DR: The details for the development of the noise-mapping BIM–GIS platform based on ArcGIS are presented to show the role of such platform in the decision-making process of both urban planning and interior design.
Abstract: Traffic noise is a major health concern for people living in urban environments. Noise mapping can help evaluating the noise level for certain areas in a city. Traditionally, noise mapping is performed in 2D geographic information system (GIS). The use of 3D GIS is also emerging in noise mapping in recent years. However, the current noise-mapping platforms can only conduct noise evaluation for the outdoor environment and the indoor environment separately. In addition, related information about absorption coefficient and transmission loss (TL) in noise calculation is not properly retrieved and is often replaced with a single value. In this research, building information modelling (BIM) and 3D GIS are integrated in order to combine traffic noise evaluation in both outdoor environments and indoor environments in a single platform. In our developed BIM–GIS integration platform, the built environment is represented in a 3D GIS model that contains information at a high level of detail from BIM. With the...
78 citations
TL;DR: In this paper, the authors constructed a model to calculate the coupled dynamic response of train-track-bridge systems, and each component of the model is presented in detail together with the corresponding data.
Abstract: This study gathers all necessary information to construct a model to calculate the coupled dynamic response of train–track–bridge systems. Each component of the model is presented in detail togethe ...
74 citations
TL;DR: In this article, a hybrid machine learning model for predicting the ultimate punching shear capacity of FRP-reinforced slabs was proposed, which employed the least squares support vector machine (LS-SVM) to discover the mapping between the influencing factors and the slab punching capacity.
Abstract: Fibre-reinforced polymer (FRP) provides an alternative reinforcement for concrete flat slabs. This research proposes a hybrid machine learning model for predicting the ultimate punching shear capacity of FRP-reinforced slabs. The model employs the least squares support vector machine (LS-SVM) to discover the mapping between the influencing factors and the slab punching capacity. Furthermore, the firefly algorithm (FA), a population-based metaheuristic, is utilised to facilitate the LS-SVM training. A data-set which contains actual tests of FRP-reinforced concrete slabs is utilised to construct and verify the proposed approach. The contribution of this research is to establish a hybrid machine method, based on the LS-SVM and FA algorithms, for meliorating the prediction accuracy of FRP-reinforced slabs’ ultimate punching shear capacity. Experimental results demonstrate that the new model has achieved roughly 55 and 15% reductions in terms of Root Mean Squared Error compared with the formula-based a...
68 citations
TL;DR: In this paper, the authors used a sensitivity analysis to quantify the dominant train properties (mass and spacing of wheels and bogies) that contribute to ground-borne vibration generation, with the aim of reducing the complexity of train-track numerical models.
Abstract: This paper uses a sensitivity analysis to quantify the dominant train properties (mass and spacing of wheels and bogies) that contribute to ground-borne vibration generation, with the aim of reducing the complexity of train–track numerical models. This research is significant because ground-borne vibration from railways is a growing problem, particularly in urban areas. Despite this fact, attempting to predict vibration levels is complex because there are many variables that contribute to the overall dynamic response. Therefore, a deterministic approach is commonly used, that ignores many of these variables. Thus, this paper identifies the variables that can be ignored, while highlighting those that are highly influential on vibration generation. For this purpose, a previously validated 2.5D finite elements-boundary elements approach is used to simulate dynamic train–track interaction. It is computed many times for a variety of modelling variables to investigate the effect of each on the ground-borne vibration levels in the far field. It is found that increases in unsprung mass of the train causes a large increase in vibration levels. Furthermore, changes in wheel/bogie spacing and semi-sprung mass are found to have a minimal effect on vibration generation.
67 citations
TL;DR: In this article, the authors present an investigation of carbonation-induced deterioration in three typical Chinese cities (Kunming, Xiamen and Jinan) under a changing climate.
Abstract: A changing climate which leads to increases in atmospheric CO2 concentration, and changes in temperature and relative humidity (RH), especially in the longer term, will accelerate the deterioration processes and consequently decline the safety, serviceability and durability of reinforced concrete (RC) infrastructure. This paper presents an investigation of carbonation-induced deterioration in three typical Chinese cities (Kunming, Xiamen and Jinan) under a changing climate. The changing trends of atmospheric CO2, local temperature and RH of typical Chinese cities are projected based on the latest CO2 emission scenarios. The time-dependent analysis is based on Monte Carlo simulation, and includes the uncertainty of climate projections, deterioration processes, material properties, dimensions and accuracy of predictive models. Deterioration of RC structures is represented by the probabilities of reinforcement corrosion initiation and damage. It was found that the mean carbonation depths by 2100 may increase...
TL;DR: In this paper, the Cleddau bridge was used to investigate thermal effects in steel box-girder bridges and their bearings, and a physics-based model of the bridge is created to which temperature distributions inferred from in situ measurements are supplied as input.
Abstract: This paper illustrates how long-term measurements can be analysed to understand bridge behaviour under changing environmental conditions and how the developed understanding can help explain the performance of its critical components. Measurements from the Cleddau bridge, a structure that has been continuously monitored for more than two years, are used to investigate thermal effects in steel box-girder bridges and, in particular, their bearings. Observed temperature distributions are very different to the recommended distributions in design codes (BS EN 1991-5: 2003). These temperature distributions create plan bending of the box girder, which in turn impose forces at the bearings that have contributed to its wear. This paper investigates bearing movements of the bridge using numerical models, and estimates the resulting forces at the supports. A physics-based model of the bridge is created to which temperature distributions inferred from in situ measurements are supplied as input. Model predictio...
Abstract: In this work, the seismic capacity of single and multi-span masonry arch bridges was assessed by limit analysis. A preliminary statistical survey was carried out on a stock of about 750 railway bridges in Italy, classified according to characteristics and expected collapse mechanisms under seismic excitation. A comprehensive parametric study was carried out on identified homogeneous classes, to calculate limit horizontal accelerations triggering the collapse mechanism in longitudinal and transverse directions. Iso-acceleration envelope curves, representing limit horizontal acceleration of the bridge as a function of geometric parameters, were then derived. These graphs can be used for preliminary seismic safety checking of existing masonry bridges, once the main geometric parameters are available by simple visual inspections and geometric surveys, and can easily be implemented in a Bridge Management System to prioritise seismic retrofitting interventions.
TL;DR: In this paper, the accuracy of a selection of expressions currently available to estimate the in-plane shear strength of reinforced masonry (RM) walls, including those presented in some international masonry codes, is compared with a set of experimental results reported in the literature.
Abstract: This paper analyses the accuracy of a selection of expressions currently available to estimate the in-plane shear strength of reinforced masonry (RM) walls, including those presented in some international masonry codes. For this purpose, predictions of such expressions are compared with a set of experimental results reported in the literature. The experimental database includes specimens built with ceramic bricks and concrete blocks tested in partially and fully grouted conditions, which typically present a shear failure mode. Based on the experimental data collected and using artificial neural networks (ANN), this paper presents alternative expressions to the different existing methods to predict the in-plane shear strength of RM walls. The wall aspect ratio, the axial pre-compression level on the wall, the compressive strength of masonry, as well as the amount and spacing of vertical and horizontal reinforcement throughout the wall are taken into consideration as the input parameters for the pro...
TL;DR: In this paper, the authors compare the long-term reliability and cost-effectiveness of wood and steel poles, and show that steel is a viable alternative to wood due to its advantages such as lower maintenance cost, light weight, consistent performance and invulnerability to insect attacks.
Abstract: Power distribution systems are susceptible to damage from natural hazards, especially hurricanes. Hurricane winds can knock down distribution poles thereby causing power outages resulting in millions of dollars in lost revenue and restoration costs. Wood has been the dominant material used to support overhead lines in distribution systems in the US. Recently however, utility companies have been searching for cost-effective alternatives to wood due to environmental concerns, durability concerns and high cost of maintenance. Steel has emerged as a viable alternative to wood due to its advantages such as lower maintenance cost, light weight, consistent performance and invulnerability to insect attacks. Both wood and steel poles are prone to deterioration over time due to decay and corrosion, respectively. As utility companies increasingly adopt the use of steel poles, there is need for a comprehensive approach to compare the long-term reliability and cost-effectiveness of wood and steel poles. This s...
TL;DR: This work presents an enhanced variant of partially observable Markov decision processes (POMDPs) for the life cycle assessment and maintenance planning of infrastructure and presents a framework able to tackle non-linearities that likely characterise action models.
Abstract: The signs of deterioration in worldwide infrastructure and the associated socio-economic and environmental losses call for sustainable resource management and policy-making. To this end, this work presents an enhanced variant of partially observable Markov decision processes (POMDPs) for the life cycle assessment and maintenance planning of infrastructure. POMDPs comprise a method, commonly employed in the field of robotics, for decision-making on the basis of uncertain observations. In the work presented herein, a continuous-state POMDP formulation is presented which is adapted to the problem of decision-making for optimal management of civil structures. The aforementioned problem may comprise non-linear and non-deterministic action and observation models. The continuous-state POMDP is herein coupled with a normalised unscented transform (NUT) in order to deliver a framework able to tackle non-linearities that likely characterise action models. The capabilities of this enhanced framework and its applicab...
TL;DR: In this article, a decision support framework based on lifetime functions has been proposed to quantify maintenance cost, failure consequences and performance benefit in terms of utility by considering correlation effects, which effectively employs tri-objective optimisation procedures in order to determine op...
Abstract: Decision-making regarding the optimum maintenance of civil infrastructure systems under uncertainty is a topic of paramount importance. This topic is experiencing growing interest within the field of life cycle structural engineering. Embedded within the decision-making process and optimum management of engineering systems is the structural performance evaluation, which is facilitated through a comprehensive life cycle risk assessment. Lifetime functions including survivor, availability, and hazard at component and system levels are utilised herein to model, using closed-form analytical expressions, the time-variant effect of intervention actions on the performance of civil infrastructure systems. The presented decision support framework based on lifetime functions has the ability to quantify maintenance cost, failure consequences and performance benefit in terms of utility by considering correlation effects. This framework effectively employs tri-objective optimisation procedures in order to determine op...
TL;DR: In this article, a compact reinforced reactive powder concrete (CRRPC) was proposed to retrofit deteriorated asphalt overlays and to strengthen orthotropic steel deck (OSD) bridges.
Abstract: Compact reinforced reactive powder concrete (CRRPC) was proposed to retrofit deteriorated asphalt overlays and to strengthen orthotropic steel deck (OSD) bridges. The resultant OSD-CRRPC composite deck is also referred to as a light-weight composite deck (LWCD) system. This paper provides experiences and lessons learned from the first application of CRRPC to retrofit the deficient asphalt overlay of an existing steel bridge in China. The paper includes information relating to finite element (FE) model analyses, a fatigue loading test, construction processes and a field measurement. FE analyses revealed that a 50-mm CRRPC layer decreased the vehicle-induced stresses in the OSD by 34–83% relative to an OSD with an 80-mm asphalt overlay. As a result, the fatigue life of the OSD could be extended significantly. The static and fatigue safeties of CRRPC were proved by comparing the predicted and experimental stresses, and field construction demonstrated the feasibility of the proposed system. CRRPC developed no...
TL;DR: In this article, the influence of the diffusion model on the time-variant corrosion damage of concrete cross-sections is studied with reference to the local damage of the reinforcing steel bars and the global deterioration of bending moment curve capacity curves.
Abstract: In durability analysis and life-cycle assessment of concrete structures transport of chlorides and other aggressive agents is generally described by using Fick’s laws of diffusion. This model is frequently applied in a simplified one-dimensional (1D) form. However, in practical applications the diffusion process is more properly described by two- or three-dimensional patterns of concentration gradients. In this paper, the accuracy of the 1D modelling of diffusion and its impact on the life-cycle assessment of concrete structures under corrosion is evaluated in deterministic and probabilistic terms with respect to more accurate two-dimensional (2D) formulations. The influence of the diffusion modelling on the time-variant corrosion damage of concrete cross-sections is studied with reference to the local damage of the reinforcing steel bars and the global deterioration of bending moment–curvature capacity curves. The results show that 2D diffusion models may be necessary for a realistic life-cycle a...
TL;DR: In this paper, numerical investigations on the performance of SMA-reinforced concrete (RC) bridge bents to monotonic and seismic loadings are presented, and incremental dynamic analyses are conducted to compare the response of the SMA RC bents with traditional steel bents considering the peak and residual deformations after seismic events.
Abstract: One of the important measures of post-earthquake functionality of bridges after a major earthquake is residual displacement. In many recent major earthquakes, large residual displacements resulted in demolition of bridge piers due to the loss of functionality. Replacing the conventional longitudinal steel reinforcement in the plastic hinge regions of bridge piers with super-elastic shape memory alloy (SMA) could significantly reduce residual deformations. In this study, numerical investigations on the performance of SMA-reinforced concrete (RC) bridge bents to monotonic and seismic loadings are presented. Incremental dynamic analyses are conducted to compare the response of SMA RC bents with steel RC bents considering the peak and the residual deformations after seismic events. Numerical study on multiple prototype bridge bents with single and multiple piers reinforced with super-elastic SMA or conventional steel bars in plastic hinge regions is conducted. Effects of replacement of the steel rebar...
TL;DR: In this paper, a design methodology based on the theory of plastic mechanism control (TPMC) is presented for dual systems combined by moment resisting frames and concentrically braced frames (MRF-CBF dual systems).
Abstract: In this paper, a design methodology based on the theory of plastic mechanism control (TPMC) is presented for dual systems combined by moment resisting frames and concentrically braced frames (MRF–CBF dual systems). The study is focused on the design of structures failing in global mode, i.e. whose collapse mechanism is characterised by the yielding of all the tensile diagonals, the buckling of the compressed ones, and the development of plastic hinges at all the beam ends and at the base of first-storey columns. The results of push-over analyses and nonlinear dynamic analyses carried out with reference to MRF–CBF dual systems designed according to the proposed procedure are compared with those obtained with reference to the same structural scheme designed according to Eurocode 8. The advantages obtained in terms of seismic performances are outlined and also economic issues are investigated pointing out the convenience of seismic design based on TPMC.
TL;DR: In this paper, the authors investigated the feasibility of incorporating an artificial neural network (ANN) as an innovative technique for modelling the pavement structural condition, into pavement management systems, and developed an ANN model for the prediction of strains primarily based on in situ field gathered data and not through the usage of synthetic databases.
Abstract: This article aims to investigate the feasibility of incorporating of an artificial neural network (ANN) as an innovative technique for modelling the pavement structural condition, into pavement management systems. For the development of the ANN, strain assessment criteria are set in order to characterise the structural condition of flexible asphalt pavements with regards to fatigue failure. This initial task is directly followed with the development of an ANN model for the prediction of strains primarily based on in situ field gathered data and not through the usage of synthetic databases. For this purpose, falling weight deflectometer (FWD) measurements were systematically conducted on a highway network, with ground-penetrating radar providing the required pavement thickness data. The FWD data (i.e. deflections) were back-analysed in order to assess strains that would be utilised as output data in the process of developing the ANN model. A paper exercise demonstrates how the developed ANN model c...
TL;DR: In this article, the authors focused on the assessment of the costs and benefits of climate adaptation strategies for reinforced concrete (RC) structures subjected to chloride ingress and climate change, and measured the cost-effectiveness of adaptation measures in terms of the Benefit-to-Cost Ratio (BCR) and the probability that BCR exceeds unity.
Abstract: Reinforced concrete (RC) structures placed in chloride-contaminated environments are subjected to deterioration processes that affect their performance, serviceability and safety. Chloride ingress leads to corrosion initiation and its interaction with service loading could reduce its operational life. Chloride ingress and corrosion propagation are highly influenced by weather conditions in the surrounding environment including climate change. Therefore, both structural design and maintenance should be adapted to these new environmental conditions. This study focuses on the assessment of the costs and benefits of climate adaptation strategies for existing RC structures subjected to chloride ingress and climate change. We studied RC structures built at different periods under different construction standards in France. The cost-effectiveness of adaptation measures was measured in terms of the Benefit-to-Cost Ratio (BCR) and the probability that BCR exceeds unity –i.e., Pr(BCR>1). The results of the paper could provide practical advice to policy makers to improve the management of existing RC structures under a changing climate by discussing the influence of the following factors on the mean BCR and Pr(BCR>1): specific exposure conditions, climate change scenarios, risk reduction due to the implementation of adaptation strategies, type of structural component, years of construction and adaptation, discount rates and damage costs.
TL;DR: In this paper, an approximate method for assessing the impact of structural deterioration and non-stationary live loads on structures, which requires only low-dimensional integration and reduces the cost of assessing time-dependent reliability over a service life extending to 50 years significantly.
Abstract: Concrete structures may deteriorate over time due to aggressive service environments, leading to a reduction in their strengths, stiffnesses and reliabilities. In general, the assessment of time-dependent reliability of ageing structures must consider uncertainties in structural deterioration as well as non-stationarities in the structural load processes. This paper develops an approximate method for assessing the impact of structural deterioration and non-stationary live loads on structures, which requires only low-dimensional integration and reduces the cost of assessing time-dependent reliability over a service life extending to 50 years significantly. This approximate method is demonstrated through several examples. The importance of non-stationarities in the resistance and load processes on time-dependent reliability is illustrated and the accuracy of the method is confirmed in several cases utilising Monte Carlo simulation.
TL;DR: In this paper, an extensive cost analysis for maintenance and seismic retrofit of typical existing road bridges, based on integrated procedures for assessment of state and seismic vulnerability, is described, which will allow public authorities and private managing companies to estimate economic indicators regarding the extent of resources required for bridge maintenance and retrofit in areas subject to seismic events.
Abstract: The work describes an extensive cost analysis for maintenance and seismic retrofit of typical existing road bridges, based on integrated procedures for assessment of state and seismic vulnerability. In particular, visual inspections to evaluate total sufficiency ratings and a simplified seismic assessment were carried out for each structure, according to procedures proposed in earlier works. The results were then used as input data for statistical analysis, to calibrate new unit maintenance, seismic retrofit and total cost equations. The procedure was applied to a stock of bridges in the province of Vicenza, north-east Italy. The results will allow public authorities and private managing companies to estimate economic indicators regarding the extent of resources required for bridge maintenance and retrofit in areas subject to seismic events.
TL;DR: In this paper, a framework based on a multi-objective genetic algorithm is proposed to identify optimal retrofit and repair combinations which ensure public safety while minimising lifetime environmental, economic and social performance measures of sustainability for infrastructure exposed to natural hazards.
Abstract: The decaying state of our infrastructure paired with rising emphasis on sustainable engineering suggests the need for upgrades which are selected based on their ability to provide adequate performance under natural hazards and minimise negative impacts on the three pillars of sustainability: society, environment and economy. This paper poses a framework based on a multi-objective genetic algorithm to help identify optimal retrofit and repair combinations which ensure public safety while minimising lifetime environmental, economic and social performance measures of sustainability for infrastructure exposed to natural hazards. Assessment of the case-study application results reveals the relationship between life-cycle environmental, economic and social indicators of sustainability for a bridge subject to earthquakes. The framework is anticipated to help guide the selection of retrofit and repair combinations by providing a set of ‘near-optimal’ non-dominated solutions, which enhance sustainability while ens...
TL;DR: In this paper, a probabilistic approach that combines Monte Carlo simulation with the extreme value theory is used and the existence of track irregularities is taken into account along with the variability of parameters related to the bridge, the track and the train.
Abstract: In this work the running safety of high-speed trains on a short-span bridge is assessed. A probabilistic approach that combines Monte Carlo simulation with the extreme value theory is used and the existence of track irregularities is taken into account along with the variability of parameters related to the bridge, the track and the train. As case study, a 12 m span filler beam bridge was selected as the train–bridge interaction effects are most significant for short spans. The running safety is assessed for the case of loss of contact between the wheel and the rail, taking into consideration only the vertical wheel–rail interaction and assuming that no lateral forces act on the train. This research enables the characterisation of the wheel unloading coefficient, the identification of the critical wheel and also the definition of the maximum allowable speed for trains to run safely on the bridge.
TL;DR: In this article, the authors compared the performance of TBM and CBM from the viewpoint of condition transition and life cycle cost, and found the optimal maintenance solutions for both maintenance policies using dynamic programming and performed a simulation study.
Abstract: Cost-effective maintenance of infrastructure systems within an acceptable level of safety and performance is the major concern of managing agencies. Recent maintenance approaches have offered two distinct maintenance policies: time-based maintenance (TBM) and condition-based maintenance (CBM). This paper compares the two policies under different cost environments for stochastically deteriorating infrastructures. The performance of TBM and CBM is evaluated from the viewpoint of condition transition and life cycle cost. We found the optimal maintenance solutions for TBM and CBM using dynamic programming and performed a simulation study. The simulation study showed that TBM causes some unexpected deterioration that leads to high cost, while CBM maintains a certain level of condition steadily under consistent inspection, which enables steady spending at the management level. The life cycle cost under CBM is relatively symmetric and has a more concentrated distribution than TBM, which has a large numbe...
TL;DR: In this paper, the authors consider the potential consequences of life-cycle engineering decisions far beyond the limits for which there is practical experience and propose a risk-informed decision tool for managing public investments in performance assurance and risk mitigation of civil infrastructure.
Abstract: Civil infrastructure facilities play a central role in the economic, social and political health of modern society. Such facilities are susceptible to ageing, which is stochastic in nature and makes their reliabilities time dependent. Life-cycle engineering analysis and risk-informed decision tools have advanced in recent years for managing public investments in performance assurance and risk mitigation of civil infrastructure. However, certain civil infrastructure projects may be designed for service periods that are substantially longer than what has been typically expected of buildings, bridges and similar facilities, extending the potential consequences of life-cycle engineering decisions far beyond the limits for which there is practical experience. Current assessment procedures will require modification to evaluate performance of civil infrastructure facilities over extended time frames and to support sustainable and equitable decisions affecting long-term public safety. This paper considers a numbe...
TL;DR: In this paper, the authors present the concept of emergency resilience and the framework for assessing this short-term resilience for urban lifeline systems in the emergency recovery stage, which can quantify differences in system performance (pre-disaster vs. post-recovery) using the new recovery degree feature, and integrate a new performance response function based on network equilibrium theory to assess emergency resilience in both the technical and organisational dimensions.
Abstract: Resilience is an emerging concept for analyzing the dynamic performance of critical infrastructures during the post-disaster recovery process. Although a number of studies examined how to assess long-term resilience (1 year +), very few have investigated short-term resilience (few days to several weeks following a disaster). This study presents the new concept of ‘emergency resilience’ and the framework for assessing this short-term resilience for urban lifeline systems in the emergency recovery stage. This framework can quantify differences in system performance (pre-disaster vs. post-recovery) using the new ‘recovery degree’ feature. It also integrates a new performance response function which is based on network equilibrium theory to assess emergency resilience in both the technical and organisational dimensions. In the case study of the water pipeline network in Lianyungang, China, the results showed that the levels of the recovery budget b and recovery resource r had different effects on emer...