Showing papers in "Structure and Infrastructure Engineering in 2014"

A review of multi-criteria decision-making methods for infrastructure management

Abstract: In infrastructure management, multi-criteria decision-making (MCDM) has emerged as a decision support tool to integrate various technical information and stakeholder values. Different MCDM techniques and tools have been developed. This paper presents a comprehensive review on the application of MCDM literature in the field of infrastructure management. Approximately 300 published papers were identified that report MCDM applications in the field of infrastructure management during 1980–2012. The reviewed papers are classified into application to the type of infrastructure (e.g. bridges and pipes), and prevalent decision or intervention (e.g. repair and rehabilitate). In addition, the papers were also classified according to MCDM methods used in the analysis. The paper provides taxonomy of those articles and identifies trends and new developments in MCDM methods. The results suggest that there is a significant growth in MCDM applications in infrastructure management applications of MCDM over the last decade...

Lifetime seismic performance of concrete bridges exposed to corrosion

Abstract: This paper presents a probabilistic approach to predict the lifetime seismic performance of concrete bridges exposed to aggressive environments. The time-variant behaviour of critical cross-sections, such as those at the base of the bridge piers, is evaluated in terms of bending moment versus curvature relationships, accounting for the degradation of both concrete and steel. The randomness involved in the diffusion process of the aggressive agents, as well as the material and geometrical uncertainties related to the structural system, is taken into account in probabilistic terms. The assessment of the lifetime seismic bridge performance is therefore obtained by means of probabilistic time-variant nonlinear static analyses of the structural system. The proposed procedure is applied to a four-span continuous bridge with box cross-section piers exposed to corrosion. The results highlight that both strength and ductility of the structural members vary over time, affecting the seismic capacity of the bridge sy...

An application of the SBAS-DInSAR technique for the assessment of structural damage in the city of Rome

Abstract: The remote sensing technique known as Differential Synthetic Aperture Radar (SAR) Interferometry (DInSAR) allows the detection and monitoring of ground settlements, by generating deformation velocity maps and displacement time-series having centimeter to millimeter accuracy. These measurements can contribute to the evaluation of the structural conditions of the constructions. Given the settlements, different approaches exist for the assessment of the structural damage, ranging from empirical estimates to detailed finite element calculations. In this work, we integrate the results of a DInSAR analysis with an intermediate semi-empirical model to investigate three buildings located in the southern part of the city of Rome. The model, originally proposed by Finno et al. [(2005). ASCEJournal of Geotechnical and Geoenvironmental Engineering, 131(10), 1199–1210], considers each building as an equivalent laminated beam, where the layers represent the floors and the core material reproduces the infill walls. The ...

Prediction of railway track geometry deterioration using artificial neural networks: a case study for Turkish state railways

Abstract: The main goal of this paper is to model track geometry deterioration using a comprehensive field investigation gathered over a period of 2 years on approximately 180 km of railway line. Artificial neural networks (ANNs) were adapted for this research. The railway line was divided into analytical segments (ASs). For each AS, the following data were collected: track structure, traffic characteristics, track layout, environmental factors, track geometry, and maintenance and renewal data. ANN models were developed for the main track geometry parameters and produced significant relationships between the variables. In addition, sensitivity analyses were performed to compute the importance of each predictor in determining the neural network. The obtained results proved that ANN may be an alternative method for predicting track geometry deterioration.

Overruns in transportation infrastructure projects

Abstract: Transportation infrastructure projects are prone to cost and schedule overruns. At the time of contract award, a construction contingency budget is often used to accommodate for unplanned events such as scope changes. Recent empirical research has shown that rework during construction as a result of design changes, errors and omission are the major contributors of overruns in projects. The statistical characteristics of rework, and cost and schedule overruns that are experienced from a project's contract award for 58 Australian transportation infrastructure projects are analysed. Theoretical probability distributions are fitted to the rework, cost and schedule overrun data. Goodness of fit tests are used in conjunction with probability-probability (P-P) plots to compare the sample distribution from the known theoretical distribution. A Generalised Logistic probability density function is found to describe the behaviour of cost-overruns and provides the best overall distribution fit. The best fitting distr...

Theoretical study and experimental verification of vibration control of offshore wind turbines by a ball vibration absorber

Abstract: In this paper, a ball vibration absorber (BVA) is introduced for vibration control of offshore wind turbines. The dynamic responses of offshore wind turbines equipped with a BVA are presented. Both theoretical and experimental investigations are carried out. An analytical model for the wind turbine tower system with installed BVA is developed based on Lagrange's equation. The BVA-structure integrated equations are derived and solved in both time domain and frequency domain. A series of shaking table tests on a 1/13-scale wind turbine model with and without a BVA were carried out to evaluate the effects of BVA on the vibration mitigation of the wind turbine tower system under earthquakes and equivalent wind-wave loads. Numerical simulations of the system are performed and compared with the experimental results. Good agreement between the numerical and experimental results is observed. The results indicate that BVA could effectively improve the performance of the offshore wind turbine.

A model for predicting failure of oil pipelines

Abstract: Oil and gas pipelines transport millions of dollars of goods everyday worldwide Even though they are the safest way to transport petroleum products, pipelines do still fail generating hazardous consequences and irreparable environmental damages Many models have been developed in the last decade to predict pipeline failures and conditions However, most of these models were limited to one failure type, such as corrosion failure, or relied mainly on expert opinion analysis The objective of this paper is to develop a model that predicts the failure cause of oil pipelines based on factors other than corrosion Two models are developed to help decision makers predict failure occurrence Regression analysis and artificial neural networks (ANNs) models were developed based on historical data of pipeline accidents The two models were able to satisfactory predict pipeline failures due to mechanical, operational, corrosion, third party and natural hazards with an average validity of 90% for the regression model and 92% for the ANN model The developed models assist decision makers and pipeline operators to predict the expected failure cause(s) and to take the necessary actions to avoid them

Long-term seismic performance of RC structures in an aggressive environment: emphasis on bridge piers

Abstract: Even though accurate structural models have been developed for the performance of corroded structures subjected to monotonic flexure and/or shear, studies on seismic performance that include corrosion damage are scarce. For the lifetime assessment of structures in aggressive environments and earthquake-prone regions, the effects of corrosion on seismic performance need to be taken into consideration. Whereas the seismic demand depends on the results of seismic hazard assessment, the deterioration of seismic capacity depends on the environmental hazard assessment. The analysis of the life-cycle reliability of corroded reinforced concrete (RC) structures under earthquake excitations is the topic of this paper. It includes (a) estimation of the seismic capacity of corroded RC components; (b) seismic and airborne chloride hazard assessment and (c) life-cycle seismic reliability of bridges with corrosion damage. In particular, this paper introduces the visualisation of corrosion process in RC members using X-r...

Diagnostic load testing and assessment of existing bridges: examples of application

Abstract: Load testing method is a significant tool in the assessment of bridge safety. One type of load tests is diagnostic load testing, the aim of which is to establish a comparison between real bridge behaviour and analytical calculation. It can be used either as acceptance test of the structures or as an estimation tool for the load carrying capacity of the already existing structures that have been in service for some time. This article presents diagnostic load tests and three examples of their application to various bridge structures and emphasises their diagnostic potential for assessment. In the majority of cases of diagnostic load tests presented in the literature, the experimental results (deflections, strains, etc) are very close or lower than the predicted ones and for this reason, such tests are expected to validate the existing structure. However, in the cases presented here, it is shown how the experimental results differ considerably from the expected ones. Since the theoretical and the experimental results of all three examples did not match, it was highly recommended to keep the matter under close investigation. A deep insight into the bridges showed serviceability and safety concerns and in some cases a repair/strengthening was necessary.

A continuous Bayesian network for earth dams' risk assessment: methodology and quantification

Abstract: Dams’ safety is highly important for authorities around the world. The impacts of a dam failure can be enormous. Models for investigating dam safety are required for helping decision-makers to mitigate the possible adverse consequences of flooding. A model for earth dam safety must specify clearly possible contributing factors, failure modes and potential consequences of dam failure. Probabilistic relations between variables should also be specified. Bayesian networks (BNs) have been identified as tools that would assist dam engineers on assessing risks. BNs are graphical models that facilitate the construction of a joint probability distribution. Most of the time, the variables included in a model for earth dam risk assessment involve continuous quantities. The presence of continuous random variables makes the implementation of discrete BNs difficult. An alternative to discrete BNs is the use of non-parametric continuous BNs, which will be briefly described in this article. As an example, a model for earth dams’ safety in the State of Mexico will be discussed. Results regarding the quantification of conditional rank correlations through ratios of unconditional rank correlations have not been presented before and are introduced herein. While the complete application of the model for the State of Mexico is presented in an accompanying paper, here some results regarding model use are shown for demonstration purposes. The methods presented in this article can be applied for investigating risks of failure of civil infrastructures other than earth dams.

Feasibility investigation for a bridge damage identification method through moving vehicle laboratory experiment

Abstract: This paper investigated the feasibility of the pseudo-static damage identification method derived from a bridge–vehicle interaction system through a moving vehicle laboratory experiment. The element stiffness index, defined as the ratio of flexural rigidity of a damaged member to that of an intact member, serves as the damage indicator. Three vehicle models and two travelling speeds were considered in the experiment to examine the effect of vehicle's dynamic characteristic and travelling speed on identified results. It is demonstrated that locations and severities of damages are detectable using the proposed method in spite of the probable changes of roadway roughness and environmental conditions. In addition, adopting higher vehicle speed as well as the vehicle with frequency close to that of the bridge increased the probability of detecting damages.

Damage detection in concrete structures using a simultaneously activated multi-mode PZT active sensing system: numerical modelling

Abstract: In this study, a structural health monitoring approach that integrates both electromechanical admittance (EMA) and guided wave (GW) techniques is presented. More specifically, the EMA technique is used for local damage identification, by employing a piezoelectric transducer (PZT) as admittance sensor. Simultaneously, the same admittance sensor is disturbed by selected elastic GWs launched by another PZT to monitor the damages located beyond the sensing area of the admittance sensor. The validation of the integrated approach is achieved by identifying the changes in electrical admittance signatures as measured on the surface electrodes of PZTs. These changes occur when damage alters the mechanical impedance of the examined concrete structure and when propagating GWs encounter structural damage. Finite element models of damages occurring in conventional unreinforced, steel-reinforced or fiber reinforced plastics-reinforced concrete specimens are investigated. Results illustrate that the proposed integrated ...

Modelling of bridge elements deterioration for Serbian bridge inventory

Abstract: In order to improve bridge management practice for public roads in Serbia, a deterioration model for bridge elements was developed using condition data collected over the last 20 years. The distrib...

Seismic risk assessment for a reinforced concrete frame designed according to Chinese codes

Abstract: The analytical formulations of two types of seismic fragility functions, namely seismic demand fragility and seismic damage fragility, are derived from the general definition of fragility function and usually adopted assumptions in seismic risk assessment. Using suitable intensity measure (IM) and damage measure (DM), the well-known Cornell's IM- and displacement-based formulations for seismic risk are revisited from the viewpoint of the analytical fragility functions. It is found that the recently widely used formulations using engineering demand parameters (EDPs) as well as DM-based approaches are two specific cases of the general IM-based risk equation, depending on the chosen fragility parameters. To apply Cornell's formulations to assess the seismic performance of Chinese code-conforming buildings and to investigate the effects of the derived fragility parameters on the seismic performance, a five-storey reinforced concrete (RC) frame designed according to the Chinese codes has been used as a case st...

BuildingsLife: a building management system

Abstract: The financial resources available for infrastructure maintenance and rehabilitation are always limited, which creates a need for efficient resources' management and for the ability to predict maintenance actions throughout the infrastructure's service life. In the context of bridges, management systems have been developed and are already implemented around the world. A much larger variety of maintenance problems and a reduced number of buildings per owner mean that building management systems (BdMSs) are still quite rare. Actually, efficient methods for the service life prediction of building materials still need to be developed. This paper discusses the service life prediction methods used in building components based on deterministic, stochastic or engineering methods. The architecture of a recently developed BdMS – BuildingsLife – is presented, where the service life analysis of components is based on an initial statistical analysis of anomalies obtained from the inspection of in-use buildings. This me...

Life cycle assessment framework for railway bridges: literature survey and critical issues

Abstract: Currently, the whole world is confronted with great challenges related to environmental issues. As a fundamental infrastructure in transport networks, railway bridges are responsible for numerous material and energy consumption through their life cycle, which in turn leads to significant environmental burdens. However, present management of railway bridge infrastructures is mainly focused on the technical and financial aspects, whereas the environmental assessment is rarely integrated. Life cycle assessment (LCA) is deemed as a systematic method for also assessing the environmental impact of products and systems, but its application in railway bridge infrastructures is rare. Very limited literature and research studies are available in this area. In order to incorporate the implementation of LCA into railway bridges and set new design criteria, this article performs an elaborate literature survey and presents current developments regarding the LCA implementation for railway bridges. Several critical issues are discussed and highlighted in detail. The discussion is focused on the methodology, practical operational issues and data collections. Finally, a systematic LCA framework for quantifying environmental impacts for railway bridges is introduced and interpreted as a potential guideline.

GPS monitoring of a steel box girder viaduct

Abstract: Structural performance monitoring of bridges has increased as major infrastructure ages and is required to sustain loads that are significantly greater than those predicted during design. Structural stiffness and/or mass distribution can change over the lifespan of a bridge structure. Resulting changes in profile or resonant frequency provide key indicators of change, and may identify structural defects. Field tests using GPS for monitoring relatively small deformations were carried out on a steel box girder viaduct bridge in the UK. The configuration consisted of five GPS receivers located at key locations on the viaduct and two reference GPS receivers. GPS data was collected at either 10 Hz or 20 Hz and post-processed using proprietary software, along with appropriate filtering and spectral analysis. Three main frequencies were clearly detected by the GPS in the vertical component. A previously reported frequency of approximately 0.56 Hz was identified along with two other frequencies. The peak vertical...

A continuous Bayesian network for earth dams' risk assessment: an application

Abstract: Dams are civil engineering structures to hinder water flows. Criteria such as purpose, size and construction material are useful to categorise them. The latter is used to classify ‘earth dams’, which tend to have higher risk levels than other types. The failure of a dam leads to significant economic loss and usually to catastrophic impacts. In an effort to comprehensively examine the variables that influence earth dam breaks and describe their interactions, a model has been developed in such a way that it allows to assess risks and to prioritise the allocation of resources for maintenance activities. The research was carried out by systematically reviewing the literature, which led to the choice of Bayesian Networks (BNs) as a tool for assessing risks. Using data from seven case studies in Mexico, a model was built, which helped to rank the dams under study, leading to results comparable with those reported in the literature. While the particular type of BN used and its quantification is presented more extensively in an accompanying paper, the model may be of interest for dam owners, managers, practitioners and academics on their efforts to manage earth dams’ risks

Structural performance evaluation of a precast prefabricated bridge column under vehicle impact loading

Abstract: In this study, the numerical analysis method was proposed to analyse the structural behaviour of bridge columns under various impact loading conditions. A parametric study of vehicle impact simulation was carried out to determine the impact loading-time functions. According to the impact simulation results, five-point piecewise linear approximation is proposed and validated. The proposed loading function was applied to the material nonlinear finite element analyses of two different types of bridge piers, the cast-in-place reinforced concrete bridge columns and the prefabricated bridge columns, which were designed under the same loading conditions. The dynamic performances of the considered bridge piers are compared using the results of dynamic numerical analyses. Also, the static design loadings of a vehicle crash defined in the Korean bridge design code and AASHTO LRFD Bridge Design Specifications were applied to analyse the results of the dynamic analyses of the piers.

Risk-based economic assessment of mitigation strategies for power distribution poles subjected to hurricanes

Abstract: This paper presents a risk-based framework to assess the hurricane damage risks to distribution poles, and investigates the risks, costs and benefit of different mitigation strategies. It is estimated that power outages due to storms cause approximately $270 million in repair/replacement costs annually in the USA. Hurricane Irene alone left approximately 6 million residents without power along the east coast of the USA in 2011, causing an estimated $5–$7 billion in damages. These high repair/replacement costs warrant an investigation of mitigation strategies that may aid in reducing replacement and damage costs. This paper describes the reliability analysis of typical timber distribution poles and probabilistic wind models to determine failure probabilities for specific locations. Furthermore, in order to more accurately portray the behaviour of distribution poles, the proposed framework includes the degradation and service-proven reliability of timber distribution poles. Four mitigation strategies are de...

Updating and validation of the dynamic model of a railway viaduct with precast deck

Abstract: This study describes the calibration and experimental validation of the dynamic model of a railway viaduct with precast deck. Global modal parameters of the structure and local modal parameters of the upper slab of the deck are identified based on a dynamic test. The calibration of the numerical model is done using a genetic algorithm that allows obtaining optimal values of 11 parameters of the numerical model. The inclusion of local modal parameters proved to be crucial, as various parameters of the numerical model do not have significant influence on global modal parameters. Mode pairing between numerical and experimental vibration modes is performed using a recent technique based on modal strain energy. The experimental validation of the calibrated numerical model is done by the comparison between numerical responses and experimental responses obtained in a dynamic test under railway traffic. This dynamic test shows the existence of a nonlinear behaviour of the viaduct's supports. There is an excellent...

A new elasto-plastic solution for analysis of underwater tunnels considering strain-dependent permeability

Abstract: An analytical–numerical solution is proposed in this paper for calculating the mechanical and hydraulic characteristics of underwater tunnels, excavated in an elasto-plastic strain-softening and Hoek–Brown rock material considering strain-dependent permeability. The problem is considered with axial-symmetry condition and thus, the initial stress state is assumed to be hydrostatic. Hydraulic and mechanical differential equations governing the plastic and the elastic rock mass around the tunnel are derived. As the derived equations do not have closed-form solutions, a computer program has been prepared, in order to solve the corresponding equations numerically and to examine the analysis. The results obtained are compared with the results obtained using a commercial finite difference code for investigating the effects of utilised simplifying assumptions. The proposed approach is also used to analyse the response of tunnels under different hydro-mechanical conditions. The results show that the proposed solut...

Galerkin scheme based determination of first-passage probability of nonlinear system response

Abstract: An approximate analytical approach for determining the first-passage probability of the response of a class of lightly damped nonlinear oscillators to broadband random excitations is presented. Markovian approximations of both the response amplitude envelope and the response energy envelope are considered. This approach leads to a backward Kolmogorov equation, which governs the evolution of the survival probability of the system. This equation is solved approximately by employing a Galerkin scheme. A convenient set of confluent hypergeometric functions is used as an orthogonal basis for this scheme. The reliability of the derived analytical solution is demonstrated by comparisons with data derived by pertinent Monte Carlo simulations.

Application of singular spectrum analysis to structural monitoring and damage diagnosis of bridges

Abstract: Singular spectrum analysis (SSA) is a novel technique and has proven to be a powerful tool for time series data analysis. Through singular value decomposition of Hankel matrix data, the time series of data can be decomposed into several simple, independent and identifiable components from singular values and singular vectors. It has already been widely applied to process climatic, meteorological, geophysical and economic data. In this paper, we demonstrate that the coupling degree of the 1st and 2nd singular values in SSA contains useful indications on the feature and composition of the analysed signal. The proposed method is successfully applied to the monitoring of structure, such as damage detection of the simulated dynamic system, experimental steel frame, bridge foundation scouring and pier settlement in the laboratory and on-site bridge monitoring during typhoon strike. The proposed algorithm is simple and suitable for structural health monitoring in the field.

The directionality effect in the seismic risk assessment of highway networks

Abstract: This study introduces the directionality effect of the ground motion in the probabilistic seismic risk assessment (PSRA) of lifeline systems. Given an earthquake scenario, the seismic wave strikes each component of the system with a different angle. The angle may vary significantly depending on the shape, the location and the orientation of the structure. An appropriate example of a lifeline system is a highway transportation network, in which under earthquake conditions the bridges are considered the most vulnerable components. The proposed PSRA model requires that the seismic fragility model is a function of a ground motion intensity measure (IM), as in the traditional risk analysis, and the angle of seismic incidence. The model was implemented in a new framework for the PSRA of highway transportation network. In addition, the framework includes new algorithms. One reduces the confidence interval of the results and one increases the computational efficiency. The example used is the highway transportation network serving the Los Angeles area, which has more than 3000 bridges. The results show a considerable difference in the system resilience with or without the seismic directionality taken into consideration. This is important for benefit/cost analysis and it represents a clear departure from the current risk analysis.

Automatic concrete health monitoring: assessment and monitoring of concrete surfaces

Abstract: To predict the degradation of concrete structures is extremely challenging. The typical approach combines periodic visual inspections with required non-destructive tests. However, this methodology only discretely evaluates few areas of the structure, being also time consuming and subject to human error. Therefore, a new method designated ‘automatic concrete health monitoring’ is herein presented which aims at automatically characterising and monitoring the state of conservation of concrete surfaces by combining photogrammetry, image processing and multi-spectral analysis. The method was designed to (i) characterise crack pattern, displacement and strain fields; (ii) map damages and (iii) assess and define restoration tasks.

Flexure strengthening of lightweight reinforced concrete beams using carbon fibre-reinforced polymers

Abstract: A series of 40 lightweight reinforced concrete (LWRC) beams of 1400 mm length and a rectangular cross section of 150 × 200 mm were cast, strengthened and then tested under four-point bending test to study the effectiveness of using externally applied carbon fibre-reinforced polymer (CFRP) composites as a method of increasing the flexural strength of under-reinforced LWRC beams. Parameters investigated include reinforcement ratio, ρ; ρ = 0.55ρb and ρ = 0.27ρb, CFRP sheet length; 600, 800 and 1000 mm, CFRP sheet width; beam width and half-beam width. Three types of strengthening schemes were used: jacketing covers the beam from bottom and two sides with total width of 500 mm, sheets at the tension side with width equal to beam width and sheets with width equal to half-beam width. Test results showed a limited increase in ultimate load-carrying capacity accompanied with some reduction in mid-span deflection for the strengthened beams. Among the strengthening schemes investigated, jacketing was the most effective for strength enhancement (about 41%) with respect to control beam; however, it reduced ductility significantly. An analytical model was proposed for predicting the ultimate load-carrying capacity of LWRC beams strengthened with CFRP composites.

Life-cycle of structural systems: design, assessment, maintenance and management

Abstract: The International Association for Life-Cycle Civil Engineering (IALCCE) was founded in 2006 to support this challenge and to create a fertile ground for promoting the study, research, and applicati...

Structural system identification of cable-stayed bridges with observability techniques

Abstract: Cable-stayed bridges are highly statically redundant, light and flexible structures. This complexity highlights the role of the structural system identification (SSI) method in the calibration of the actual properties of the simplified models of these structures. This study proposes the first application of observability techniques to SSI of cable-stayed bridges. This method enables to define which subset of actual structural variables should be measured on site to identify mechanical properties, such as Young's modulus, area and inertia, or stiffnesses (EA and EI) of deck, pylon and stay cables. The effects of the inclination and inertia of the stay cables and the existence of pylon and deck cracking in the observability of different cable-stayed bridges are studied. The results obtained are validated by the models of actual cable-stayed bridges.

Calibrating a high-fidelity finite element model of a highway bridge using a multi-variable sensitivity-based optimisation approach

Abstract: This article presents the implementation of a calibration procedure for a finite element (FE) model of a state highway bridge using sensory data measured on the bridge. The objective is to modify the high-fidelity FE model of the bridge so that its dynamic behaviour matches, as closely as possible, that of the bridge under analysis. The bridge under investigation is a steel–concrete composite bridge that is instrumented with a wireless monitoring system to collect its vibration response under ambient vibrations. A detailed three-dimensional FE model of the bridge was developed to represent the bridge as realistically as possible. The detailed modelling can minimise the amount of uncertainty in the model and the number of parameters that require updating. A multi-variable sensitivity-based objective function is used to minimise the error between the experimentally measured and the FE-computed modal characteristics. An iterative optimisation approach has been undertaken to find the optimum structural parame...