A system-based model for fatigue assessment of riveted railway bridge connections, comprising a number of basic components, is presented in this article. Probabilistic fatigue load spectra are developed through Monte Carlo simulation of train passages over a finite element model of a typical, short-span bridge. Uncertainties arising from loading, resistance and modelling sources are taken into account. The riveted connection is treated through a set of generic sub-systems that capture potential damage in identifiable hot-spots, such as rivets, holes and angle fillets. The fatigue reliability over time is evaluated through system reliability methods by treating these hot-spots as the elements of a structural system. The results show that the probability of failure of the connection depends significantly on the form of the system adopted for the analysis and the rivet clamping force. Damage scenarios accounting for the potential loss of rivet clamping force are investigated, and it is shown that, in some cases, they can affect connection reliability considerably. © 2012 Copyright Taylor and Francis Group, LLC.
Vrouwenvelder T, Faber MH, Chryssanthopoulos M (2003) Mission and work program of the Joint Committee on Structural Safety, APPLICATIONS OF STATISTICS AND PROBABILITY IN CIVIL ENGINEERING, VOLS 1 AND 2pp. 989-994 MILLPRESS SCIENCE PUBLISHERS
Imam B, Righiniotis TD, Chryssanthopoulos MK (2007) Probabilistic fatigue load spectra for riveted railway bridges,
Imam BM, Chryssanthopoulos MK (2010) A review of metallic bridge failure statistics, Bridge Maintenance, Safety, Management and Life-Cycle Optimization - Proceedings of the 5th International Conference on Bridge Maintenance, Safety and Managementpp. 3275-3282
This paper presents a review of bridge failure statistics, based on literature survey and webbased search, focusing on metallic bridges. Failure cases are distinguished between those resulting in bridge collapse and those that have not reached collapse but resulted in loss of serviceability. Classification of the most common failure causes and modes of failure is undertaken. Statistics regarding the time frame of collapses in the bridge lifetime, bridge structural configuration and the number of resulting casualties are presented. The results show that collapses due to natural hazards, design errors and limited knowledge are the most commonly encountered in metallic bridges, followed by accidents and human error. When analysed chronologically, the data demonstrates a decreasing trend for collapses attributed to limited knowledge and an increasing trend in failures resulting from accidents and natural hazards. In terms of non-collapse cases, fatigue failures are found to be predominant. The paper concludes with a discussion of bridge failure consequences and their significance in risk assessment of bridge structures. © 2010 Taylor & Francis Group, London.
Past experience has shown that stringer-to-cross-girder connections in riveted railway bridges are susceptible to fatigue cracking. This fatigue damage is caused by secondary stresses, which develop in the different components of the connection. For this reason, more detailed analysis techniques are needed to capture this type of behaviour. In this paper, a finite element (FE) model of a typical riveted railway bridge is developed by incorporating the detailed local geometry of a stringer-to-cross-girder connection into the global bridge model. Before the development of this model, benchmark FE studies are carried out on a double-lap joint and the results are presented in terms of stress concentration factors and stress gradients. Further verification studies are carried out on a local bridge connection FE model, in terms of its rotational stiffness. After this investigation, a refined FE model of the bridge is analysed under the passage of a freight train. Principal stress histories at different components of the connection are obtained, which are then combined with the plain material S-N curve, in order to identify the most fatigue-critical locations of the connection. These are identified as being the rivet holes and, in some cases, the angle fillet. By considering different rivet clamping stresses and different rivet defect scenarios it is found that the most damaging effects are caused by the presence of clearance between the rivet shank and the hole, and the loss of a rivet. The rivet clamping stress is also found to affect fatigue damage considerably. © 2007 Elsevier Ltd. All rights reserved.
Chryssanthopoulos M, Votsis RA, Abdel Wahab M (2005) Simulation of Damage Scenarios in an FRP Composite Suspension Footbridge, Key Engineering Materials293-294pp. 599-606
Hollaway LC, Chryssanthopoulos MK (2006) Construction and Building Materials: Guest editorial, Construction and Building Materials20(1-2)
Recent studies have found that stringer-to-cross-girder connections in riveted railway bridges are susceptible to fatigue cracking, caused by secondary, deformation induced effects. These effects are difficult to interpret in terms of a single applied stress descriptor, which is customarily used in an S?N assessment. In order to address this problem, the results of a global?local finite element analysis of a riveted railway bridge are used in this paper within the context of the theory of critical distances (TCD). Using the TCD in the way proposed by Taylor [Bellett D, Taylor D, Marco S, Mazzeo E, Guillois J, Pircher T. The fatigue behaviour of three-dimensional stress concentrations. Int J Fatigue 2005; 27(3) 207?21], fatigue damage (a) is shown to converge upon mesh refinement and (b) is found to be relatively sensitive to the selection of the characteristic dimension of the critical volume. Furthermore, comparisons of the TCD-based method with its more traditional, detail-specific S?N counterpart, reveal that the latter can underestimate fatigue damage, in some cases by a factor of 3.5.
GIAVOTTO V, POGGI C, CHRYSSANTHOPOULOS M, DOWLING P (1991) BUCKLING BEHAVIOR OF COMPOSITE SHELLS UNDER COMBINED LOADING, BUCKLING OF SHELL STRUCTURES, ON LAND, IN THE SEA AND IN THE AIRpp. 53-60 ELSEVIER APPL SCI PUBL LTD
Chryssanthopoulos M, Diamantidis D, Vrouwenvelder T (2003) The JCSS Probabilistic Model Code: Experience and recent developments, APPLICATIONS OF STATISTICS AND PROBABILITY IN CIVIL ENGINEERING, VOLS 1 AND 2pp. 907-912 MILLPRESS SCIENCE PUBLISHERS
Manzocchi GME, Chryssanthopoulos M, Elnashai AS (1995) The influence of material variability on failure mode control of steel frames, EUROPEAN SEISMIC DESIGN PRACTICEpp. 245-251 A A BALKEMA
Rafiq MI, Chryssanthopoulos M, Onoufriou T (2005) Improvement in performance of corroding concrete structures using health monitoring systems, pp. 330-330
Chryssanthopoulos MK, Righiniotis TD (2006) Fatigue reliability of welded steel structures, Journal of Constructional Steel Research62(11)pp. 1199-1209
In general, two different approaches to the formulation of the fatigue limit state are considered, the first based on S - N lines in combination with Miner's damage accumulation rule, and the second based on fracture mechanics crack growth models and failure criteria. Often, the two approaches are used sequentially, with S - N being used at the design or preliminary assessment stage and fracture mechanics for more refined remaining life or inspection and repair estimates. However, it is essential to link the results, and the decisions made, at the design and assessment stages, and it is therefore important to develop compatible methodologies for using these two approaches in tandem. In doing so, it is essential to understand and quantify different uncertainty sources and how they might affect the robustness of the results obtained, and the subsequent decisions made about the structure. The objective of this paper is to highlight parts of recent research at the University of Surrey on the fatigue assessment of steel bridges. The work includes the development of a probabilistic fracture mechanics methodology for the prediction of fatigue reliability, using up-to-date crack growth and fracture assessment criteria and incorporating information on inspection and subsequent management actions. © 2006 Elsevier Ltd. All rights reserved.
Hollaway LC, Chryssanthopoulos MK (2006) Editorial,Composites Part A: Applied Science and Manufacturing37(8)pp. 1101-?
MANZOCCHI GME, CHRYSSANTHOPOULOS M, ELNASHAI AS (1994) AN ANALYTICAL SOLUTION FOR THE PROBABILISTIC RESPONSE OF SDOF NONLINEAR RANDOM-SYSTEMS SUBJECTED TO VARIABLE AMPLITUDE CYCLIC LOADING, EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS23(5)pp. 489-506 JOHN WILEY & SONS LTD
Imam BM, Righiniotis TD, Chryssanthopoulos MK (2008) Probabilistic fatigue evaluation of riveted railway bridges, Journal of Bridge Engineering13(3)pp. 237-244
Farreras-Alcover I, Chryssanthopoulos M, Andersen JE (2015) Regression models for structural health monitoring of welded bridge joints based on temperature, traffic and strain measurements, Structural Health Monitoring14(6)pp. 648-662 Sage
A modelling platform based on regression analysis is developed as a novel approach to structural health monitoring of
welded joints of orthotropic bridge steel decks. Monitoring outcomes from the Great Belt Bridge (Denmark) are used
to develop regression models following a weighted least squares approach to characterize the normal correlation pattern
between environmental conditions (daily-averaged pavement temperatures), operational loads (daily-aggregated
heavy traffic counts) and a strain-based performance indicator. The developed models can be used within a structural
health monitoring?based asset management framework for performance assessment (i.e. diagnosis of structural performance
changes) and performance prediction (i.e. prognosis of structural performance leading to service life estimates).
The main novelty of the work presented consists of the development of an algorithm based on statistical control charts
related to the prediction bands of the regression models. The algorithm enables the interpretation of new monitoring
data and the identification of potentially abnormal behaviours via outlier detection, as part of an envisaged ?real-time?
performance assessment application. The proposed approach to outlier detection through structural health monitoring
is finally illustrated considering actual monitoring outcomes from the bridge. This highlights the applicability of the developed
modelling platform and contributes to bridging the gap between monitoring data and monitoring-based information
that can lead to more effective asset management decisions.
Imam B, Righiniotis TD, ChryssanthopouBos MK, Bell B (2006) Analytical fatigue assessment of riveted rail bridges, Proceedings of the Institution of Civil Engineers: Bridge Engineering159(3)pp. 105-116
As some of the older riveted railway bridges are close to or have even exceeded their theoretical fatigue lives, it is desirable to develop a comprehensive fatigue assessment methodology for fatigue-critical details. The aim of this study was to present damage and fatigue life estimates for the riveted connections of a typical riveted UK railway bridge through finite-element analyses. In particular, the effect of connection fixity and assumed fatigue detail classification, the effect of the simultaneous passage of two trains over the bridge, the effect of a reduced Young's modulus for the bridge material and the effect of dynamic amplification are studied under different loading scenarios. A historical load model was developed in order to represent bridge rail traffic between 1900 and 1970. The BS 5400 medium traffic trains were used to represent the bridge traffic from 1970 onwards. It was found that the connection damage is axle-dominated and is affected by the parameters mentioned above. The fully-fixed stringer-to-cross-girder connections were found to be the most fatigue-critical details. The damage accumulation rate was found to be small in the pre-1970 period under the historical load model but showed a considerable increase with the introduction of the BS 5400 trains (post-1970).
Chryssanthopoulos MK, Giavotto V, Poggi C (1995) Characterization of manufacturing effects for buckling-sensitive composite cylinders, Composites Manufacturing6(2)pp. 93-101
This paper presents a detailed statistical analysis on geometric imperfections recorded on two series of nominally identical composite cylinders. These defects can be classified in two categories, both due to the particular manufacturing method used: out-of-roundness and change of thickness due to the overlapping of various layers. The statistical analysis is developed for various purposes: to evaluate the common properties of cylinders with different laminations, to build up a characteristic model for the geometric imperfections suitable for probabilistic simulations in buckling analysis and to identify the parameters for quality control processes. The analysis of the change in thickness due to overlapping layers allows evaluation of the stiffening effects of the manufacturing process that, in some cases, could affect the buckling behaviour of composite cylinders. A standard procedure for the characterization and qualification of manufacturing processes for composite shells, with particular attention to the factors that influence their buckling behaviour, is proposed.
Karatzas VA, Zhang Y, Tsouvalis NG, Chryssanthopoulos MK (2012) A parametric investigation of the response of directly laminated composite-to-metal single lap joints, ECCM 2012 - Composites at Venice, Proceedings of the 15th European Conference on Composite Materials
Adhesive bonding is a rapidly growing technique that offers considerable potential to the repairing and joining of structural members. This work has been performed within the context of FP7 Co-Patch research program and presents a parametric experimental study of adhesively bonded single lap joint geometries between dissimilar materials, namely typical marine steel and carbon fiber reinforced polymers, using the co-curing technique i.e. by directly laminating the composite on the steel. Four different geometry cases with varying overlap and substrate lengths and five different composite material systems were considered and experimentally tested. It may be concluded that the failure load of the joints increased with the increase of the overlap length. The magnitude of this increase is strongly dependant on the quality of bonding over the overlap length, which in turn is associated with the fabrication method, rather than the mechanical properties of the composite material system.
Imam BM, Chryssanthopoulos MK (2012) Causes and consequences of metallic bridge failures, Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE)22(1)pp. 93-98
Robustness evaluation of bridges within a risk-based framework requires estimation of the probability of occurrence of different hazards followed by an assessment of the vulnerability of the bridge with respect to those hazards, as well as quantification of the consequences of potential failure. The first part of the paper deals with a statistical analysis of past metallic bridge failures which can help in identifying the principal hazards affecting bridges and their associated vulnerability. The results show that natural hazards, design errors and limited knowledge are amongst the most commonly encountered causes of collapse in metallic bridges, followed by accidents and human error aspects other than in design. When analysed chronologically, the data demonstrates a decreasing trend for collapses attributed to limited knowledge and an increasing trend in failures resulting from accidents and natural hazards. The paper continues by presenting a categorisation procedure through which consequences arising from potential bridge failures can be estimated. Associated models for quantifying their magnitude considering both spatial and temporal domains are highlighted. Finally, the predictive capability of the models is outlined through a case study.
Janssens V, O apos Dwyer DW, Chryssanthopoulos MK (2012) Assessing the consequences of building failures, Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE)22(1)pp. 99-104
The consequences of structural failures, as a result of a hazard, can take several forms: from material/structural damage and human injuries/fatalities to functional downtime and environmental impact. Within a risk-based robustness framework, consequence modelling is an important step in estimating risk, both in determining the robustness of a building and in assessing the benefit of possible robustness-improving measures. This paper highlights the principles to be adopted in estimating consequences arising from potential building failures. The multi-dimensional and variable aspects of the "cost of failure" are discussed, and the various types of consequences arising from building failure are examined. In this respect, a categorisation of failure consequences is presented, together with associated models for quantifying their magnitude.
Theophilou AI, Chryssanthopoulos MK (2011) A ground motion record selection procedure utilizing a vector-valued intensity measure for optimized incremental dynamic analysis, Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineeringpp. 168-175
A procedure is presented for the selection of ground motion records, suitable for an optimized incremental dynamic analysis. The procedure is optimized with respect to (1) reduction in the number of records, and (2) improved accuracy, compared to random record selection. The procedure is applied to a bilinear single-degree-of-freedom system, which could act as a proxy to a more complex multi-degree-of-freedom system. A vector-valued intensity measure is proposed, which contains the normalized spectral area parameter, in an effort to capture the effect of frequency content and period elongation on the structural response. The damage measure investigated is the ductility factor, whose relationship and correlation to the intensity measure are quantified through regression analysis. By way of example, the prediction of the ductility demand for a bilinear system representing a ten-story building is presented. © 2011 Taylor & Francis Group, London.
Harding J, Chryssanthopoulos M (2006) Professor Patrick J. Dowling CBE DL FREng FRS - Preface, JOURNAL OF CONSTRUCTIONAL STEEL RESEARCH62(11)pp. 1041-1042 ELSEVIER SCI LTD
Rafiq MI, Chryssanthopoulos MK, Onoufriou T (2004) Sensitivity analysis of chloride induced deterioration models for concrete bridges, CD-Rom Proceedings A.A. Balkema Publishers
Kallias AN, Chryssanthopoulos MK (2014) Performance profiles of ageing steel railway bridges affected by atmospheric corrosion, Bridge Maintenance, Safety, Management and Life Extension - Proceedings of the 7th International Conference of Bridge Maintenance, Safety and Management, IABMAS 2014pp. 1089-1096
Atmospheric corrosion is a commonly observed form of deterioration in steel railway bridges. The progression of corrosion damage can lead to inadequate structural performance and reduced safety, which ultimately can lead to catastrophic failures. The rate of deterioration due to atmospheric corrosion is determined by the levels of key climatic variables (temperature and relative humidity) and airborne pollutants (e.g. sulphur dioxide and chlorides), as well as the properties of the protective system applied on the structure (e.g. coating). Currently, the focus in countries with ageing infrastructure is placed on maintaining/upgrading their large stock of existing assets rather than new construction, with the environmental impacts associated with maintenance, upgrade and replacement activities becoming an increasingly important factor. The consistent performance assessment of deteriorating structures can enable the rational prioritisation of resource allocation during asset management. In this paper, a framework is presented for the long-term performance assessment of steel bridges affected by atmospheric corrosion, including the performance of the protective system and distinguishing between condition and resistance performance criteria. Emphasis is given to the consistent exposure classification in line with the corrosivity classification guidelines of international standards. The methodology is demonstrated using a typical short-span steel railway bridge encountered on the UK network. Performance profiles are developed for individual elements of the bridge using, as indicators, coating breakdown and thickness loss factors, as well as bending and shear resistance ratios. © 2014 Taylor & Francis Group.
Rafiq MI, Onoufriou T, Chryssanthopoulos M (2006) Sensitivity of uncertainties in performance prediction of deteriorating concrete structures, STRUCTURE AND INFRASTRUCTURE ENGINEERING2(2)pp. 117-130 TAYLOR & FRANCIS LTD
Photiou NK, Hollaway LC, Chryssanthopoulos MK (2006) Strengthening of an artificially degraded steel beam utilising a carbon/glass composite system, Construction and Building Materials20(1-2)pp. 11-21
To rehabilitate damaged or sub-standard steel structures, techniques utilising the lightweight, high strength and corrosion resistance of fibre reinforced polymer (FRP) composites have been proposed. The flexural load carrying capacity of a steel girder can be increased significantly by adhesively bonding carbon fibre polymer (CFRP) composites to its tension flange. This paper discusses the experimental results to investigate the effectiveness of an ultra-high modulus, and a high modulus, CFRP prepreg in strengthening an artificially degraded steel beam of rectangular cross-section under four-point loading. Four beams were upgraded, two utilising U-shaped prepreg units, which extended up the vertical sides of the beam to the neutral axis height, whereas the other two beams used a flat plate prepreg. All beams had an identical hybrid lay-up of CFRP and glass fibre reinforced polymer (GFRP) composite but for each of the geometrical shapes either an ultra-high modulus or a high modulus CFRP was used. Fabrication of the prepreg material was undertaken in situ and all the prepregs were bonded to the steel substrate utilising an adhesive film. The composite containing the ultra-high modulus CFRP failed when the ultimate strain of the carbon fibre was reached in the pure moment region. The failure load exceeded the plastic collapse load of the undamaged beam, thus demonstrating the effectiveness of the proposed upgrading scheme. On re-loading the failed beams, the U-shaped hybrid upgrade continued to act compositely with the steel beam outside of a well confined region close to the original failure location, whereas the beams with the flat plate upgrade exhibited the typical response of a steel beam, owing to debonding having taken place over practically the entire length of the prepreg. The beams using the high modulus CFRP reached even higher ultimate loads and exhibited ductile response leading to very high deflections; neither fibre breakage nor adhesive failure was observed in either the U-shaped or the flat plate strengthened beam. © 2005 Elsevier Ltd. All rights reserved.
Rafiq MI, Chryssanthopoulos MK, Onoufriou T (2004) Performance updating of concrete bridges using proactive health monitoring methods, Reliability Engineering & System Safety86(3)pp. 247-256
Uncertainties associated with modelling of deteriorating bridges strongly affect management decisions, such as inspection, maintenance and repair actions. These uncertainties can be reduced by the effective use of health monitoring systems, through which information regarding in situ performance can be incorporated in the management of bridges. The objectives of this paper are twofold; first, an improved chloride induced deterioration model for concrete bridges is proposed that can quantify degradation in performance soon after chlorides are deposited on the bridge, rather than when initiation of corrosion at the reinforcement level takes place. As a result, the implications of introducing proactive health monitoring can be assessed using probabilistic durability criteria. Thus, the second objective of the paper is to present a methodology for performance updating of deteriorating concrete bridges fitted with a proactive health monitoring system. This methodology is illustrated via a simple example of a typical bridge element, such as a beam or a part of a slab. The results highlight the benefits from introducing [`]smart' technology in managing bridges subject to deterioration, and quantify the reduction in uncertainties and their subsequent effect on predictions of future bridge performance.
Structural failure consequences can take many different forms: from material/structural damage and
human injuries/fatalities, to functional downtime and environmental impact, as well as loss of
reputation and collateral damage that may be orders of magnitude higher than the reconstruction
cost. Within a risk-based robustness framework, consequence modelling is an important step in
estimating risk, and needs to be undertaken with clarity and transparency. This paper highlights the
principles to be adopted in estimating consequences arising from potential building and bridge
failures. The two structural forms are chosen so as to elucidate factors relevant to cases where
failure is confined to a single facility, or where it is likely to affect a spatial network. Past
experience, as well as methods that are increasingly used in emergency response planning, are
reviewed. A categorisation of failure consequences is presented, together with associated models for
quantifying their magnitude.
A large percentage of the railway bridges in the UK rail network and around Europe are of riveted construction exceeding in many cases 100 years of age. The remaining fatigue life of these bridges is difficult to estimate due to the uncertainties regarding the fatigue behaviour of wrought-iron and older steel material which were used for their construction. The problem is further compounded by the uncertainties associated with the loading both past and future. Previous global finite element analyses of a typical wrought-iron riveted railway bridge have shown that the fatigue critical details are the inner stringer-to-cross-girder connections (Imam et al. 2005). The analyses were carried out under a historical load model (Imam et al. 2005), developed to represent rail traffic in the period 1900-1970, and present day traffic (BS5400 1980) for the period 1970 onwards. Deterministic remaining fatigue life estimates of the connections were found to be sensitive to the level of dynamic amplification as well as the fatigue classification of the details. Following this work, this paper presents probabilistic fatigue life estimates for the most highly damaged stringer-to-cross-girder connection, as identified by the global analysis of the riveted bridge. On the loading side, the problem is randomised through the frequency of train traffic, dynamic amplification and uncertainties regarding the difference between actual and calculated stresses. On the response side, different assumed S-N curves used for detail classification and the Miner sum are also treated as random. The probabilistic analysis, which is carried out using Monte Carlo simulation, shows that the most heavily fatigue-loaded stringer-to-cross-girder connection has considerable fatigue life reserve. Through a sensitivity study, it is found that for a 2.3% probability of failure, the remaining fatigue life of the investigated connection is equal to 68 years for a pessimistic scenario. Under a more realistic combination of variables (base model), the 2.3% characteristic remaining fatigue life is found to be 480 years. Figure 1 shows the effect of different variables on the time to attainment of a 2.3% probability of failure assuming a base model. It can be seen that fatigue life estimates exhibit the highest sensitivity to detail classification, in other words the constant amplitude fatigue behaviour of the detail, and the factor ±, which takes into account the difference between measured and calculated s
Sriramula S, Chryssanthopoulos MK (2013) An experimental characterisation of spatial variability in GFRP composite panels, Structural Safety42pp. 1-11
Probabilistic tools are being used to understand the inherent uncertainty of FRP composites. Over the years different approaches have developed, focusing on behaviour and associated uncertainties at a micro-/meso-/macro-scale, each with specific advantages/limitations depending on the type, and scope, of the analysis being undertaken. Consideration of spatial variability, and associated random field modelling, of geometric and material/mechanical properties is believed to be an important factor in seeking to improve strength and reliability estimates but lack of experimental data has hindered the applicability and usefulness of results hitherto obtained. In this paper, modelling strategies for characterising and specifying the spatial variability in terms of random fields are presented for two distinctly different types of GFRP composite panels. Autocorrelations for, and cross-correlations among, strength and stiffness properties are evaluated in terms of coupon spatial distances for various forms of correlation functions. These properties are found to be well represented by an exponential autocorrelation function, and specific values for correlation lengths are evaluated, providing an insight into the influence of material and manufacturing factors on the properties of GFRP composite material systems. © 2013 Elsevier Ltd.
Photiou NK, Hollaway LC, Chryssanthopoulos MK (2006) Selection of carbon-fiber-reinforced polymer systems for steelwork upgrading, Journal of Materials in Civil Engineering18(5)pp. 641-649
This paper examines the effectiveness of a high and an ultrahigh modulus carbon-fiber-reinforced polymer (CFRP) composite prepreg, both of which have been specifically developed for the civil engineering industry. A film adhesive, compatible with the matrix material of the CFRP composite, has been introduced. The bonding characteristics of this film adhesive have been compared with those of a standard two-part adhesive - widely used in the construction industry - with those of a two-part adhesive - frequently used for high-grade bonding applications in the aerospace industry. The results have shown that when bonding carbon fiber composites to steel, the film adhesive has more favorable characteristics compared to those of the standard civil engineering adhesive, though the high-grade, and higher-cost, aerospace adhesive has superior bonding qualities. It has also been demonstrated that a good understanding of the full load-deformation response of relevant joints, including load-strain and load-extension characteristics, as well as failure mode characterization, is essential. © 2006 ASCE.
ELNASHAI AS, CHRYSSANTHOPOULOS M (1991) EFFECT OF RANDOM MATERIAL VARIABILITY ON SEISMIC DESIGN PARAMETERS OF STEEL FRAMES, EARTHQUAKE ENGINEERING & STRUCTURAL DYNAMICS20(2)pp. 101-114 WILEY-BLACKWELL
Ioannou I, Chryssanthopoulos MK (2011) Probabilistic estimates of scenario loss through a two-stage Monte Carlo approach, Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineeringpp. 252-259
A contribution towards better understanding, and communication to any interested parties, of seismic risk in loss estimation studies is believed to be the distinct treatment of inherent uncertainties (aleatory) from those associated with the models that could, in principle, be reduced (epistemic). In pursuing this objective, this paper treats separately and explicitly these sources of uncertainty through a two-stage Monte Carlo methodology, which may offer some advantages over existing simplified and/or approximate procedures. The methodology can be applied under general conditions, with fragility and exposure curves obtained by any of the generally accepted procedures. It has been implemented in the estimation of the direct financial loss of a single building, though other loss measures could also be incorporated. A three storey moment resisting frame is used to appraise the proposed methodology and highlight the relative importance of uncertainty sources in risk-based scenario loss. © 2011 Taylor & Francis Group, London.
Jin NH, Chryssanthopoulos MK, Parke GAR (2007) A probabilistic methodology for sustainable bridge management, LIFE-CYCLE COST AND PERFORMANCE OF CIVIL INFRASTRUCTURE SYSTEMSpp. 181-189 TAYLOR & FRANCIS LTD
Alcover IF, Chryssanthopoulos MK, Andersen JE (2013) SHM-based probabilistic model updating for performance assessment of welded joints in steel decks considering strain, temperature and traffic data, Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013pp. 4523-4529
Structural monitoring has the potential to reduce the uncertainties associated with the prediction of performance profiles of deteriorating civil infrastructures. However, there is still a need to further develop the theoretical framework to extract relevant information from monitoring data to support management strategies. The present paper focuses on the use of monitoring data to assess the performance of welded joints in orthotropic steel decks. Firstly, a probabilistic model to predict on an hourly basis a strain-related performance indicator based on pavement temperatures and heavy traffic intensities is presented. Model parameters are then estimated/updated using monitoring outcomes from the Great Belt Bridge (Denmark) through Bayesian inference, using Markov Chain Monte Carlo (MCMC) simulation. Including more monitoring data in the estimation process may result in a reduction of the uncertainty of the estimated model parameters, which can be used to determine appropriate monitoring durations. Model-based performance predictions are benchmarked with real monitoring outcomes. Good agreement is found for a short-termprediction time interval of eight consecutive days with similar ambient conditions. The adequacy of the proposed model is discussed based on the obtained results and an overview of the ongoing research is finally given. © 2013 Taylor & Francis Group, London.
Alcover IF, Andersen JE, Alcover IF, Chryssanthopoulos MK, Rafiq MI (2012) Towards a SHM-based methodology for updating fatigue reliability of orthotropic steel decks, Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Managementpp. 232-238
Orthotropic steel decks are likely to experience fatigue issues during their service life, the assessment of which turns out to be rather complex due to their intricate geometric features and the combined influence of traffic and temperature on the characteristics of the pertinent load effects, as well as the presence of various uncertainties. Structural Health Monitoring (SHM) can play a role in reducing some of the inherent uncertainties while assessing fatigue performance using either the S-N or a fracture mechanics approach. However, it is still necessary to develop the theoretical framework for SHM-based methodologies in order to use effectively the outcomes provided by SHM systems, thus avoiding a situation where monitored data cannot be readily incorporated into practical decision making. The present paper reviews current approaches for assessing fatigue in orthotropic decks using SHM data in combination with an S-N approach. A probabilistic model to assess fatigue damage considering pavement temperatures and traffic intensities is presented, which is intended to serve as the basis towards a SHM-based methodology. The objective of such a methodology is to update fatigue reliability in orthotropic decks considering multiple incomplete monitoring data. This should lead to more accurate performance predictions and contribute towards the rational use of SHM methods in or-thotropic steel decks. © 2012 Taylor & Francis Group.
Rafiq MI, Chryssanthopoulos MK, Onoufriou T (2006) Predictive SHM-supported deterioration modelling of reinforced concrete bridges, Proceedings of the 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Costpp. 595-596
Deterioration, increase in loading demand and change in utilization have induced an unknown level of risk in the use of transport infrastructure systems. Bridges being a vital element of such systems, due to their very nature as well as their exposure to harsh environmental conditions, should be effectively managed for the benefit of the overall transport network. Predicting the future condition and reliability of the bridges is vitally important in this process. Probabilistic models have been developed to estimate and predict the extent of deterioration in, for example, concrete bridges. However, the input parameters of these models are fraught with uncertainties, thus severely limiting their accuracy, particularly over longer time frames. On the other hand, continuous innovations in the sensing and measurement technology have lead to the development of monitoring instruments that can provide continuous (or almost continuous) data regarding the actual structural performance in the time frame. This information cannot be used directly for the prediction of future performance, first because it typically pertains to a small number of specific locations, and secondly because it needs to be combined with a whole host of other knowledge components. Furthermore, uncertainties in the instruments/measurements and in the future behaviour of the structure and its interaction with the environment (e.g. including the effects of deterioration) also hinder the predictive capability of current modelling tools. The potential benefits of improving performance prediction through the integration of health monitoring systems with probabilistic predictive models, and their implications on the management of deterioration prone structures are presented in this paper through the development of an integrated methodology. It is shown, through application case studies, that the confidence in predicted performance can be significantly increased through the use of SHM-supported modelling of deterioration and the major inspection and maintenance activities can be delayed on the account of increased confidence in the predicted performance. An example of such integration is illustrated in Figure 1 for various cases of sensor outputs including attainment of limiting value as well as (Graph Presented) confirmation of safety at various points in time during the service life. It is clear that the uncertainty is reduced with the availability of additional information and the level of this redu
Aggelopoulos ES, Righiniotis TD, Chryssanthopoulos MK (2014) Composite patch repair of steel plates with fatigue cracks growing in the thickness direction, COMPOSITE STRUCTURES108pp. 729-735 ELSEVIER SCI LTD
Kazantzi AK, Righiniotis TD, Chryssanthopoulos MK (2008) The effect of joint ductility on the seismic fragility of a regular moment resisting steel frame designed to EC8 provisions, Journal of Constructional Steel Research64(9)pp. 987-996
Structural Health Monitoring Systems (SHMS) are increasingly present in most modern long-span bridges. Those systems can be used to better assess the performance of structures by reducing the uncertainties associated with deterioration modelling. This can potentially lead to a reduction of the operational costs. Despite their promise and potential, a gap still remains between the outcomes of those systems and practical bridge management decisions. As a result, huge amounts of data can be continuously collected which are not readily useable, thus being of reduced interest in practical terms. Methodologies which integrate SHMS within Bridge Management Systems (BMS), need to be developed to address asset management issues traditionally informed by visual inspections and scarce Non Destructive Tests (NDT). This integration should overcome the shortcomings of current approaches and exploit the advantages offered by modern sensor technologies. The present paper reviews the different uses of SHMS on long-span bridges. The motivation of using SHMS to inform and improve bridge management decisions is presented. The interest of a local monitoring approach targeting selected structural components is highlighted. The need of a combined approach between traditional inspection techniques, NDT and monitoring is justified in terms of spatial and temporal coverage. The relevance of probabilistic approaches to assess and update structural performance indicators is outlined. The case of the Great Belt Bridge (Denmark) is described to illustrate the use of SHMS on long-span bridges, together with an overview of ongoing research.
Chloride induced corrosion, caused primarily by de-icing salts or salt spray in marine environments, is one of the most common deterioration processes in reinforced concrete. It often causes a localized loss of section, known as pitting, which can lead to a significant reduction of the structure's service life. In order to predict the impact of this phenomenon on the mechanical properties of the reinforcing bars in concrete a thorough analysis of its characteristics is needed. At present, most of the models found in literature describe uniform corrosion and those that do address localized corrosion focus on a simplified definition of the reduced cross-sectional area of corroded rebars without due attention to physical characteristics and spatial variability. This may be attributed to the limitations of current non-automated and largely heuristic methods used in evaluating the corrosion characteristics on the surface of reinforcement. Automation of the corrosion measurement method would lead to the development of comprehensive corrosion models considering both systematic and random features of the deterioration process. In this paper, experimental results from corroded bars are processed using 3D scanning techniques and characterised using spatial analysis tools, thus preparing the ground for probabilistic corrosion modelling based on random field concepts.
Alcover IF, Andersen JE, Chryssanthopoulos MK (2013) Performance assessment and prediction of welded joints in orthotropic decks considering hourly monitoring data, Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE)23(4)pp. 436-442
Orthotropic steel decks can experience fatigue at welded joints, the assessment of which turns out to be a complex task owing to their intricate geometry, the stochastic nature of the primary live load (traffic flow) and the temperature dependent composite action between the pavement and the steel deck. In recent years, the possibility of monitoring, in addition to traditional inspections, has been put forward as a means of improved assessment. Nevertheless, a rigorous framework to (a) enable the effective use of high amounts of multiple/incomplete data provided by distributed data acquisition systems, (b) improve current monitoring-based assessment methods, and (c) enhance current simulation and data visualization techniques, is still absent. A theoretical framework is presented in which a stress-related performance indicator is estimated through a multiple regression model with hourly pavement temperatures and heavy traffic intensities as independent variables. The proposed performance indicator is proportional to fatigue damage following the principles of the S-N approach and the Miner's rule. Typical applications of this model include (a) analysis of monitoring outcomes for performance assessment, (b) performance prediction of past/future events and (c) fatigue assessment. To illustrate the proposed approach, model-based performance predictions are benchmarked with real monitoring outcomes from the Great Belt Bridge (in Denmark), and good agreement has been observed. Moreover, model predictions are used to estimate the fatigue life of a monitored welded joint. The new methodology enhances Structural Health Monitoring (SHM) methods for orthotropic decks and provides a framework to integrate and visualize the multiple outcomes produced by modern monitoring systems as a part of the Bridge Management System or to assess the remaining life of structures.
Sriramula S, Chryssanthopoulos MK (2009) Random field characterisation of GFRP composite properties, ICCM International Conferences on Composite Materials
Sriramula S, Chryssanthopoulos MK (2009) Quantification of uncertainty modelling in stochastic analysis of FRP composites, Composites Part A: Applied Science and Manufacturing40(11)pp. 1673-1684
Aggelopoulos ES, Righiniotis TD, Chryssanthopoulos MK (2006) Parametric evaluation of CFRP patch effectiveness in fatigue repair, Proceedings of the 3rd International Conference on Bridge Maintenance, Safety and Management - Bridge Maintenance, Safety, Management, Life-Cycle Performance and Costpp. 337-338
Over the years, there has been an increased research interest on the use of adhesively bonded composite reinforcements for upgrading metallic structures. Although most of this work has concentrated on the use of composites for the fatigue repair of aircraft components (e.g. Baker & Jones 1988), recently, a small number of studies has focused on the use of bonded composite plates for strengthening metallic bridge members (e.g. Tavakkolizadeh & Saadatmanesh 2003a). However, the emphasis of this research has been on the strengthening of deteriorated or degraded steel members with only a handful of cases, where the strengthening of fatigue damaged steel bridge components was investigated (e.g. Tavakkolizadeh & Saadatmanesh 2003b). In this paper, the problem of a steel plate with a fatigue surface crack growing in the thickness direction, reinforced with an adhesively bonded composite (CFRP) patch is analysed using the finite element method. Parametric 2D finite element (FE) analyses are performed and the effect of a number of parameters, such as the crack depth and the properties of the patch and the adhesive on the interfacial shear and peel stress distributions, the crack tip stress fields and the fatigue life of the repaired plate is investigated. Results for the shear and peel stresses developed at the steel/adhesive interface indicate that severe stress concentrations occur at the extremities of the patch at the near-crack and end-of-patch positions. Greater peel stresses are found near the end-of-patch region, while the region near the crack is found to be dominated by large shear stresses. The shear stresses in the latter region are found to be several times greater than those near the end-of-patch region. The beneficial effects of crack patching are observed through the considerable reduction in the stress magnification factor Y. A parametric study whereby the Young's modulus and the thickness of the patch (Ec and tc) and the adhesive (Ea and ta), normalised by those of the steel plate (Es and ts), are varied in a systematic way, demonstrates that the reduction in Y is influenced primarily by the properties of the patch (see Fig. 1). Fatigue life calculations based on the crack growth model by Paris & Erdogan (1963) show a significant increase in the fatigue life of the damaged plate, when this is strengthened with a patch. This is shown in Table 1, where the ratio of the fatigue life for a patched plate Np to that for an unpatched plate Nu is presente
Rafiq MI, Chryssanthopoulos MK, Sathananthan S (2015) Bridge condition modelling and prediction using dynamic Bayesian belief networks, Structure and Infrastructure Engineering11(1)pp. 38-50
© 2014, Taylor & Francis.The development of a condition-based deterioration modelling methodology at bridge group level using Bayesian belief network (BBN) is presented in this paper. BBN is an efficient tool to handle complex interdependencies within elements of engineering systems, by means of conditional probabilities specified on a fixed model structure. The advantages and limitations of the BBN for such applications are reviewed by analysing a sample group of masonry bridges on the UK railway infrastructure network. The proposed methodology is then extended to develop a time dependent deterioration model using a dynamic Bayesian network. The condition of elements within the selected sample of bridges and a set of conditional probabilities for static and time dependent variables, based on inspection experience, are used as input to the models to yield, in probabilistic terms, overall condition-based deterioration profiles for bridge groups. Sensitivity towards various input parameters, as well as underlying assumptions, on the point-in-time performance and the deterioration profile of the group are investigated. Together with results from ?what if? scenarios, the potential of the developed methodology is demonstrated in relation to the specification of structural health monitoring requirements and the prioritisation of maintenance intervention activities.
Orthotropic steel decks can present fatigue issues at welded joints, the assessment of which turns out to be a complex task due to their intricate geometry, the uncertain nature of the primary live load (traffic flow) and the temperature-driven composite action between the pavement and the steel deck. Current assessment methods tend to disregard the joint effect of traffic levels and pavement temperatures and rely on relatively long-term monitoring periods to capture strain responses and the overall associated uncertainty. This limits the ability to interpret short-term monitoring data, since failure to quantify this temperature-traffic interaction makes it impossible to understand short-term variations in the monitored strain responses. To overcome current limitations, a heuristic model is presented to predict stress-related performance indicators monitored at welded joints in orthotropic steel decks considering pavement temperatures and traffic levels as input parameters. Model parameters are determined through multiple linear regression and can be regarded as the set of health-related features to perform local Structural Health Monitoring (SHM). Model simulations are benchmarked with real monitoring data from the Great Belt Bridge (Denmark). In general, good agreement is found between model simulations and monitoring data. Current research efforts to improve the limitations of the proposed model are outlined.
The development of a methodology to model network level bridge deterioration using a Bayesian Belief Network (BBN) is presented in this paper. BBN's are capable of handling complex relationships between elements (e.g. beams, columns, etc.) and the system (e.g. stock of bridges) by means of conditional probabilities specified on a fixed model structure. The advantages and limitations of BBN's for such applications are discussed. The application of the methodology is presented through a case study on a group of UK railway masonry arch bridges. The condition of elements within a selected sample of bridges is used as input in the BBN, together with a set of conditional probabilities based on inspection experience, to yield, in probabilistic terms, the overall condition of the bridge group. Sensitivity of various input parameters, as well as underlying assumptions, on group performance is investigated, which can help with the prioritization of assessment and maintenance intervention activities. © 2010 Taylor & Francis Group, London.
MANZOCCHI GME, CHRYSSANTHOPOULOS M, ELNASHAI AS (1995) Response statistics of non-linear SDOF systems with random properties, 10TH EUROPEAN CONFERENCE ON EARTHQUAKE ENGINEERING, PROCEEDINGS, VOLS 1-4pp. 1327-1332 A A BALKEMA
Kazantzi AK, Righiniotis TD, Chryssanthopoulos MK (2008) Fragility and hazard analysis of a welded steel moment resisting frame, Journal of Earthquake Engineering12(4)pp. 596-615
This study focuses on deterioration modelling and performance assessment of metallic bridges affected by atmospheric corrosion, considering also the contribution of typical protective systems in the form of multi-layer coatings. The mechanisms leading to coating degradation are reviewed and the main coating types used by infrastructure owners are highlighted. Building on information contained in industry manuals, a simple model for coating degradation is proposed. Atmospheric corrosion models are then presented, with emphasis given to exposure classification, in line with corrosivity classification guidelines and recent research quantifying the influence of corrosion through dose?response functions. Coating degradation and corrosion models are integrated into a modelling framework, aimed at producing performance profiles of elements in metallic railway bridges. Finally, the framework is implemented in a case study in which a range of condition and resistance performance criteria are presented for different elements, such as girders and stiffeners, and their constituent parts, such as webs and flanges. It is shown that the proposed methodology is sufficiently detailed to enable differentiated performance predictions based on key external factors, and has scope for improvement, especially as coating and corrosion models are informed by the collection of field data.
Onoufriou T, Kyriakides MA, Berberidis K, Chryssanthopoulos MK, Kalis A (2012) SmartEN - Smart management for sustainable built environment including bridges, structures and infrastructure systems, Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Managementpp. 290-297
This paper presents the research and training focus of major European Marie Curie Initial Training Network research programme, SmartEN, which focuses on the development of effective smart proactive management methods for sustainable built and natural environment. The SmartEN research focuses on multi-disciplinary developments combining mainly the areas of proactive management, non-destructive evaluation methods from the civil engineering discipline, with wireless sensor networks, signal processing and communication technologies from the electrical engineering. Recent emerging technologies in miniature wireless sensor platforms which utilize novel digital signal processing offer new opportunities for continuous monitoring of complex systems. These developments open up a completely novel area for multi-disciplinary research towards the 'smart' management of sustainable environment. The SmartEN ITN Marie Curie Programme aims to push innovation through effective development and integration of emerging technologies targeting key application areas of current interest to Europe and worldwide. These include smart proactive management of structural systems such as tall buildings, bridges including long span modern bridges and heritage bridges, transportation infrastructure networks and urban micro-climate as this affects urban structures and infrastructure networks. © 2012 Taylor & Francis Group.
Votsis RA, Stratford TJ, Chryssanthopoulos MK (2009) Dynamic assessment of a FRP suspension footbridge, Advanced Composites in Construction 2009, ACIC 2009 - Proceedings of the 4th International Conferencepp. 144-155
In the past decade, the vibration serviceability of slender footbridges has become the subject of serious investigation. Despite the advantages that FRP materials offer in bridge engineering such as higher strength-to-weight ratio and ease of installation, their use in the construction of slender footbridges has raised concerns with regard to their dynamic response, due to the reduced mass and stiffness of these materials compared with their conventional counterparts. In this paper, the dynamic assessment of a FRP suspension footbridge (the Wilcott footbridge) is described. This is performed using dynamic field testing supported by finite element (FE) modelling: the field testing on the bridge produced values for frequencies, mode shapes and damping which were consequently used to calibrate the FE model. Using the calibrated FE model it was shown that the influence of semistructural or non-structural elements, such as parapets, on the dynamic properties of the structure can be significant. The dynamic response of the structure due to human excitation was also measured during the test. The results confirmed that suspension footbridges built from FRP materials are susceptible to vibrations induced by pedestrians. The response levels of the investigated bridge are lower than the threshold levels specified in the relevant code of practice. © 2009, NetComposites Limited.
Rafiq MI, Chryssanthopoulos MK, Sathananthan S (2014) Bridge condition modelling and prediction using dynamic Bayesian belief networks, Structure and Infrastructure Engineering
The development of a condition-based deterioration modelling methodology at bridge group level using Bayesian belief network (BBN) is presented in this paper. BBN is an efficient tool to handle complex interdependencies within elements of engineering systems, by means of conditional probabilities specified on a fixed model structure. The advantages and limitations of the BBN for such applications are reviewed by analysing a sample group of masonry bridges on the UK railway infrastructure network. The proposed methodology is then extended to develop a time dependent deterioration model using a dynamic Bayesian network. The condition of elements within the selected sample of bridges and a set of conditional probabilities for static and time dependent variables, based on inspection experience, are used as input to the models to yield, in probabilistic terms, overall condition-based deterioration profiles for bridge groups. Sensitivity towards various input parameters, as well as underlying assumptions, on the point-in-time performance and the deterioration profile of the group are investigated. Together with results from 'what if' scenarios, the potential of the developed methodology is demonstrated in relation to the specification of structural health monitoring requirements and the prioritisation of maintenance intervention activities. © 2014 © 2014 Taylor & Francis.
Sriramula S, Chryssanthopoulos MK (2009) Probabilistic models for spatially varying mechanical properties of in-service gfrp cladding panels, Journal of Composites for Construction13(2)pp. 159-167
Aggelopoulos ES, Righiniotis TD, Chryssanthopoulos MK (2011) Debonding of adhesively bonded composite patch repairs of cracked steel members, COMPOSITES PART B-ENGINEERING42(5)pp. 1262-1270 Elsevier
Sriramula S, Chryssanthopoulos MK (2011) Random field modelling of spatial variability in FRP composite materials, Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineeringpp. 2335-2342
Although extensive experimental studies have underpinned random variable characterisation of composite material properties, random field models are so far based primarily on engineering judgement. In this paper, modelling strategies are presented for characterising and specifying the spatial randomness in terms of random fields, utilizing the results of extensive experimental studies at macro scale. To assess the spatial variability in composite material systems, experiments were conducted on two different types of Glass Fibre Reinforced Polymer (GFRP) composite panels. The first set of experiments was carried out on aged and weathered hand lay-up panels, made with Chopped Strand Mat (CSM) glass reinforcement in a polymer matrix while the second set comprised structural grade pultruded GFRP plates supplied in pristine condition. Typical auto and cross correlation patterns for a range of mechanical properties are discussed. It is concluded that manufacturing and in-service conditions play a major role in determining random field parameters, with correlation lengths in appropriately selected functions ranging from 20 to 100 mm © 2011 Taylor & Francis Group, London.
Llano L, Rafiq MI, Chryssanthopoulos MK (2012) Physical characterization of reinforcing bar corrosion in concrete, Bridge Maintenance, Safety, Management, Resilience and Sustainability - Proceedings of the Sixth International Conference on Bridge Maintenance, Safety and Managementpp. 274-281
Chloride induced corrosion, caused primarily by de-icing salts and/or salt spray from marine environments, is one of the most common deterioration processes in reinforced concrete. It often causes a localized loss of section, known as pitting, which can lead to a significant reduction of the structure's service life. In order to predict the impact of this phenomenon on the mechanical properties of the reinforcing bars in concrete a thorough analysis of its characteristics is needed. At present, most of the models found in literature describe uniform corrosion and those that do address localized corrosion focus on a simplified definition of the reduced cross-sectional area of corroded rebars without due attention to actual physical characteristics and spatial variability. This may be attributed to the limitations of current non-automated and largely heuristic methods used in evaluating the corrosion characteristics on the surface of reinforcement. Automation of the evaluation method could allow the creation and development of comprehensive corrosion models which consider both systematic and random features of the deterioration process. In this paper, a preliminary study to characterize geometrically chloride induced corrosion is presented, together with the steps envisaged in order to develop an improved chloride induced corrosion model. © 2012 Taylor & Francis Group.
Shaw A, Sriramula S, Gosling PD, Chryssanthopoulos MK (2010) A critical reliability evaluation of fibre reinforced composite materials based on probabilistic micro and macro-mechanical analysis, Composites Part B: Engineering41(6)pp. 446-453
Niekamp S, Bharadwaj UR, Sadhukhan J, Chryssanthopoulos MK (2015) A multi-criteria decision support framework for sustainable asset management and challenges in its application, Journal of Industrial and Production Engineering32(1)pp. 44-57
© 2015 © 2015 TWI Ltd.Despite an increasing demand for considering sustainability aspects in asset management, there is a lack of guidance for decision-makers on how this can be achieved. The aim of this research is to present rational decision support for sustainable management of industrial assets in situations where there are multiple conflicting objectives. For this purpose, a Multi-criteria decision analysis framework that incorporates sustainability criteria over the whole life cycle has been developed. Stakeholder participation and uncertainty assessment are considered explicitly allowing for a holistic perspective and higher confidence in the results. In order to facilitate communication, methods for visualization of numerical results are highlighted. While the focus of this study is on the development of the framework, the challenges of applying it and potential steps to address these are discussed through an application in the shipping sector.
Kazantzi AK, Righiniotis TD, Chryssanthopoulos MK (2011) A simplified fragility methodology for regular steel MRFs, Journal of Earthquake Engineering15(3)pp. 390-403
Votsis RA, Chryssanthopoulos MK (2009) Assessment of debonding in GFRP joints using damage identification techniques, Construction and Building Materials23(4)pp. 1690-1697
This paper presents a review of bridge failure statistics, based on literature survey and webbased
search, focusing on metallic bridges. Failure cases are distinguished between those resulting in bridge
collapse and those that have not reached collapse but resulted in loss of serviceability. Classification of the
most common failure causes and modes of failure is undertaken. Statistics regarding the time frame of collapses
in the bridge lifetime, bridge structural configuration and the number of resulting casualties are presented.
The results show that collapses due to natural hazards, design errors and limited knowledge are the
most commonly encountered in metallic bridges, followed by accidents and human error. When analysed
chronologically, the data demonstrates a decreasing trend for collapses attributed to limited knowledge and an
increasing trend in failures resulting from accidents and natural hazards. In terms of non-collapse cases, fatigue
failures are found to be predominant. The paper concludes with a discussion of bridge failure consequences
and their significance in risk assessment of bridge structures.
Chryssanthopoulos MK, Imam B (2014) The future of ageing metallic bridges, Bridge Maintenance, Safety, Management and Life Extension - Proceedings of the 7th International Conference of Bridge Maintenance, Safety and Management, IABMAS 2014pp. 95-109
During their service lives, metallic structures are susceptible to degradation through corrosion and fatigue, particularly when loading and environmental demands increase over time. In the UK, as in many other countries, the transport infrastructure network relies on a large number of ageing metallic bridges which require careful performance management under tight budgetary constraints in order to extend their lives for longer than planned, or to overcome deficiencies revealed during operation. Over the past decade, significant progress has been made in understanding many facets of their behaviour, including better appreciation of loading histories and future trends, refined approaches for structural modelling, the potential impact of deterioration processes on performance indicators, and the development of new repair techniques using fibre reinforced composites. Moreover, life cycle considerations have encompassed both economic and environmental criteria. Lessons learned from a variety of projects undertaken in conjunction with infrastructure owners and other stakeholders are reviewed, with attention given to the implications for new construction, whose future will depend on the knowledge that we can transfer successfully from a previous generation of structures. © 2014 Taylor & Francis Group.
Faber MH, Vrouwenvelder ACWM, Sørensen JD, Chryssanthopoulos MK, Narasimhan H (2011) Robustness of structures- A report on a joint European project, Applications of Statistics and Probability in Civil Engineering -Proceedings of the 11th International Conference on Applications of Statistics and Probability in Civil Engineeringpp. 2129-2135
In 2005, the Joint Committee on Structural Safety (JCSS) together with Working Commission (WC) 1 of the International Association of Bridge and Structural Engineering (IABSE) organized a workshop on robustness of structures. Two important decisions resulted from this workshop, namely the development of a joint European project on structural robustness under the COST (European Coop-eration in Science and Technology) programme and the decision to develop a more elaborate document on structural robustness in collaboration between experts from the JCSS and the IABSE. Accordingly, a project titled 'COST TU0601: Robustness of Structures' was initiated in February 2007, aiming to provide a platform for exchanging and promoting research in the area of structural robustness and to provide a basic framework, together with methods, strategies and guidelines enhancing robustness of structures. The project will conclude in October 2011; a summary of the work carried out in this project and the major results achieved are described in this paper © 2011 Taylor & Francis Group, London.
Llano L, Chryssanthopoulos MK, Hagen-Zanker A, Rafiq MI (2013) Stochastic modeling of chloride-induced pitting corrosion of reinforcement bars in concrete, Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013pp. 2659-2664
Chloride induced corrosion, caused primarily by salt spray in marine environments, airborne salts and de-icing salts, is one of the most common deterioration processes in reinforced concrete structures. At present, most of the models found in literature describe uniform corrosion and those that do address localized corrosion focus on a simplified definition of the reduced cross-sectional area of corroded rebars without due attention to physical characteristics and spatial variability. This may be attributed to the limitations of current manual methods used in evaluating the corrosion characteristics on the surface of reinforcement. In this paper, an automated procedure for the acquisition of corrosion depth data on rebars based on 3D laser scanning is investigated. Moreover, the first results of an analysis process based on image analysis using wavelet theory are presented. These results show a promising way of improving the classification of corrosion depths. This can be useful for the relation between spatial distribution of corrosion and mechanical properties of the corroded element. © 2013 Taylor & Francis Group, London.
A vector-valued intensity measure is presented, which incorporates a relative measure represented by the normalized spectral area. The proposed intensity measure is intended to have high correlation with specific relative engineering demand parameters, which collectively can provide information regarding the damage state and collapse potential of the structure. Extensive dynamic analyses are carried out on a single-degreeof- freedom system with a modified Clough?Johnston hysteresis model, using a dataset of 40 ground motions, in order to investigate the proposed intensity measure characteristics. Response is expressed using the displacement ductility, and the normalized hysteretic energy, both of which are relative engineering demand parameters. Through regression analysis the correlation between the proposed intensity measure and the engineering demand parameters is evaluated. Its domain of applicability is investigated through parametric analysis, by varying the period and the strain-hardening stiffness. Desirable characteristics such as efficiency, sufficiency, and statistical independence are examined. The proposed intensity measure is contrasted to another one, with respect to its correlation to the engineering demand parameters. An approximate procedure for estimating the optimum normalized spectral area is also presented. It is demonstrated that the proposed intensity measure can be used in intensity-based assessments, and, with proper selection of ground motions, in scenario-based assessments.
A novel methodology is presented for probabilistic fatigue life prediction of welded joints in orthotropic bridge steel decks. Monitoring data were used to specify time-series model parameters for the main drivers of fatigue damage in such structures, namely pavement temperatures and heavy traffic intensities, which influence the stress range distributions at critical locations. Polynomial regression models were developed to quantify the relationship between fatigue loading, derived using S-N principles from strain measurements at welded joints, with pavement temperatures and heavy traffic counts. The different models were integrated within a fatigue reliability framework, in which the uncertainties arising from material properties and fatigue damage at failure were modelled via random variables. A Monte Carlo scheme was then deployed to predict S-N fatigue damage using the fatigue loading regression models and simulated time-series of heavy traffic and pavement temperatures. Thus, fatigue reliability profiles were generated, which account for different scenarios in terms of future changes in traffic and pavement temperature. The proposed methodology was illustrated considering actual monitoring outcomes from the Great Belt Bridge (Denmark) with reliability profiles developed for both ?baseline? and ?adverse? scenarios in the context of asset integrity management. The combined effect of higher temperature and heavy traffic levels was shown to result in considerable reductions in fatigue reliability, with a commonly used threshold being reached up to 40 years earlier compared to the baseline ?no change? scenario. However, this reduction was not uniform for all the fatigue details considered, emphasizing the importance of monitoring different locations, based on a thorough understanding of the fatigue behaviour of the orthotropic steel deck.
This research presents a combined economic and environmental assessment tool for evaluating the economic and environmental performance of alternative maintenance strategies for optimising service life extension of old railway bridges. It is intended to assist bridge managers in identifying the best overall combination of both economic and environmental criteria in their decision making.
An approach to assess the potential environmental effect of delaying maintenance work into the future, through the introduction of time-weighting of environmental impacts, is proposed. It is intended to aid railway asset managers to determine the potential benefit or dis-benefit of such ?delaying? options, in comparison with ?non-delaying? options.
The methodology of the tool is based on life cycle analysis and accounts for the cost and environmental impacts that arise during the working life of different alternative maintenance strategies. The economic performance of the alternatives is analysed by using Life Cycle Costing (LCC) whilst the environmental performance is assessed based on Life Cycle Assessment (LCA). The tool addresses the potential unequal working lives of alternative maintenance strategies by evaluating cost and environmental performance through an ?equivalent annual? term. The combined economic and environmental performance of the alternatives is evaluated through a multi-criteria decision analysis (MCDA) technique called ?Single Multi-Attribute Rating Technique using Swings? (SMARTS).
A case study based on typical maintenance plans for a U.K. railway bridge is presented to demonstrate the application of the developed methodology. The three alternative maintenance strategies assessed are deck replacement, standard deck restoration and minor deck restoration. Sensitivity analyses are conducted to account for limited knowledge in some of the input quantities.
In summary, this research has shown that the developed combined economic and environmental assessment tool has the ability to identify the best overall performance bridge maintenance alternative and is capable of integrating economic and environmental inputs and presenting the overall performance output in a coherent and transparent way to aid towards decision making. It is believed that it can be of particular use in asset integrity management decisions for assets approaching the end of their original or design service life.
This research is aim at investigating Climate Change effects on buckling strength of steel plate elements. Climate change is the consequence of global warming as a result of the increase of greenhouse gases in the atmosphere due to both natural and anthropogenic reasons. This can lead to changes in environmental and atmospheric pollution parameters which may affect the deterioration rate of engineering materials and infrastructural systems. A review of the state-of-the art dose-response function, which are capable of linking atmospheric pollutants concentrations and environmental variables with long-term deterioration, was carried out to quantify the potential impact of climate change on material corrosion loss of carbon steel. The corrosion loss was then linked with the long-term buckling strength of steel plate elements to produce long-term performance models.
A full mapping of corrosion loss from 0%-90% section thickness loss under compressive and shear loads was undertaken using both linear and non-linear buckling finite element analyses through ABAQUS in order to find out the impact of the effect of section thickness loss on the buckling strength of steel plate elements used in plate girder bridges. A total of 522 three-dimensional finite elements models of realistic plate elements were analysed under different corrosion intensities and patterns, the latter including uniform and non-uniform corrosion as well as pitting corrosion.
The dose-response functions were then utilised to predict long-term corrosion under different climate scenarios. The damage assessment by the well-known ISO model was compared to that of two other models, Klinesmith et al. (2007) and Kallias et al. (2016). From the damage assessment using the dose-response functions it was discovered that the ISO model tends to underestimate the corrosion loss while the Klinesmith and Kallias models were found to result in comparable predictions for corrosion loss over time. The buckling FE results were normalised and plotted in terms of reduction factor curves which can offer a quick way for estimating the buckling strength loss over time, for different corrosion scenarios. These curves can offer useful support to infrastructure owners and managers to assess the implications of corrosion on plate elements and plan effective maintenance strategies throughout the life cycle of assets in the face of challenging climate change uncertainties and financial constraints.
Steel-concrete-steel (SCS) sandwich panels are an efficient means of achieving a strong and stable composite wall. Development in the 70's and 80's focussed on tunnelling, with other applications, particularly in the defence and offshore sectors, appearing later.
Renewed focus has been placed on the system in recent years due to a proliferation of proposals for new nuclear power stations in Europe. Many new nuclear projects that have been completed in recent years have been significantly delayed by problems with reinforcement congestion. SCS construction offers a potential solution to this, since reinforcement is either significantly reduced or eliminated entirely in most designs. As a result of this renewed interest, industry has sought to develop improved design rules, both for economy and easier regulatory approval.
As with any composite system, the strength of the system is derived from the ability of the materials to interface efficiently with each other where they are connected. Review of existing design guides and research showed a gap in understanding of the effects of shear connection on the overall behaviour of the system, particularly when resisting out-of-plane loads. This thesis aims to improve this understanding, leading to improved design provision and a wider range of applications for SCS panels in industry.
An extensive literature search found a large body of test results. However, the majority of these tests are for designs where shear connection is over-provisioned, meaning shear connection is not critical. The tests that were conducted with lower degrees of shear connection were found to be insufficient to draw definitive conclusions about changes in behaviour. For this reason, numerical modelling using finite element analysis was used to supplement the test data. A validation and verification exercise was performed, which showed that the model accurately predicted the behaviour seen in testing, for all of the relevant failure modes.
This thesis focusses on the three design checks that are required for panels subject to out-of-plane loads; bending resistance, shear resistance and deflection. The effect of reduced shear connection on each of these design checks is explored in turn.
For bending resistance, design rules based on first principles cross-section equilibrium are found to accurately predict the point of failure for the majority of cases. However, the existing assumption of a smooth profile of shear connector force is found to be incorrect on the tension plate, with tensile cracking leading to discontinuities in the stud force profile. Further interpretation of this result shows that this can lead to an unconservative prediction of the failure load when a panel with a low degree of shear connection is subject to a uniformly-distributed load (UDL). A new design rule is presented for this situation.
Design equations for shear resistance are found to vary considerably between design codes and countries. As with the bending check, the test database is found to be lacking in tests with low enough degrees of shear connection to draw definitive conclusions about any changes in behaviour. A parametric FE study is presented to investigate these effects. The study focusses on varying the degree of shear connection for groups of beams loaded at different shear-span to depth ratios. Different behaviour is observed in each group, with the influence of shear connection varying, depending on which shear transfer action is dominant. The study shows that unconservative predictions are made for a number of the design models, particularly for slender beams with low degrees of shear connection. A new adjustment is presented for the Eurocode shear resistance model that removes the unconservative predictions. The models from the fib Model Code are suggested as a better alternative, again with some adjustment to account for reduced degree of shear connection.
Infrastructure performance is of great importance for a nation?s economy and its
people?s quality of life. For efficient and effective infrastructure asset management,
structural health monitoring (SHM) has been researched extensively in the past 20-30
years. With an increasing number of SHM systems being installed, the interpretation of
the large volume of monitoring data, i.e. often manifested as condition identification,
becomes essential in asset integrity management. This paper provides an appraisal of
existing literature reviews on SHM, considering both reviews on different types of
structures and those focused on different approaches for data interpretation. It explores
the evolution of research interests in this field and identifies the need for an integrated
physics-based and data-driven structural condition identification approach.
Flat slabs are reinforced concrete slabs supported directly on columns without beams. Flat slabs are commonly used for construction of medium-rise office buildings and car parking structures due to their ease of construction, reduced story height and ease of routing of services. Load concentrations can be significant at edge and corner columns as well as around internal columns, making the slab-column connections susceptible to punching shear failure. Most reported occurrences of progressive collapse in flat slab structures have had punching shear failure as an initial local failure. Some of these collapses progressed horizontally through punching of adjoining connections due to gravity load redistribution, dynamic effects and excessive slab deformation. In many cases, failure also progressed vertically due to impact of falling slabs on lower lying ones.
Design rules specified in codes and building regulations to prevent progressive collapse are not suitable for application to flat slab structures due to the development of failure mechanisms, such as punching shear and compressive membrane action at small deformations; and post-punching shear and tensile membrane action at large deformations. The influence of these mechanisms, and their interaction, on the response of flat slab systems during progressive collapse is not fully understood. Knowledge on influence of the dynamic nature of progressive collapse in flat slab system response is also not fully established. Existing numerical and analytical approaches for assessment of progressive collapse in flat slab structures either limits response assessment to failure at the first connection or neglects one or more mechanisms. Hence, they can provide unrealistic predictions of damage after local failure, little knowledge on the collapse progression and the contributions of neglected mechanisms to overall system response.
In this thesis, numerical and analytical models were developed and validated for the prediction of the post-punching shear capacity of isolated slab specimens, using tests reported in literature. Results of numerical modelling of punching shear strength, residual shear strength after punching and post-punching shear strength in isolated slab specimens agreed with those of tests. Results of residual shear strength after punching and post-punching shear strength obtained analytically were also in agreement with test results.
A numerical approach was developed for the assessment of progressive collapse of flat slab systems. The flat slab system model considered compressive membrane action, tensile membrane action, gravity load redistribution and damage propagation. These mechanisms were not considered in the isolated slab specimens. Results of numerical flat slab system analysis provided a good understanding of the gravity load redistribution after the sudden loss of an internal column, the contribution of compressive membrane action prior to the punching shear failure, tensile membrane and post-punching shear actions after punching shear failure of connections. The transition and interaction between these mechanisms were also investigated.
Analytical slab-column subsystem and flat slab system models were also developed. Both models provided results which agreed with those obtained through dynamic finite element analysis. Results from the analytical flat system model confirmed the contribution of compressive membrane action in the resistance of progressive collapse through the confinement of the slab area around the slab-column connections and the reduction of slab deformation around the slab-column connections. Both numerical and analytical flat slab system approaches showed that for cases of slabs with sufficient integrity reinforcement and no punching shear reinforcement, punching shear failure of adjoining connections would occur though the progressive collapse could be arrested with sufficient area of integrity reinforcement. Required areas of integrity reinfor
The offshore wind turbines (OWTs) are dynamically sensitive, whose fundamental frequency can be very close to the forcing frequencies activated by the environmental and turbine loads. Minor changes of support conditions may lead to the shift of natural frequencies, and this could be disastrous if resonance happens. To monitor the support conditions and thus to enhance the safety of OWTs, a model updating method is developed in this study. A hybrid sensing system was fabricated and set up in the laboratory to investigate the long-term dynamic behaviour of the OWT system with monopile foundation in sandy deposits. A finite element (FE) model was constructed to simulate structural behaviours of the OWT system. Distributed nonlinear springs and a roller boundary condition are used to model the soil-structure-interaction (SSI) properties. The FE model and the test results were used to analyze the variation of the support condition of the monopile, through an FE model updating process using Estimation of Distribution Algorithms (EDAs). The results show that the fundamental frequency of the test model increases after a period under cyclic loading, which is attributed to the compaction of the surrounding sand instead of local damage of the structure. The hybrid sensing system is reliable to detect both the acceleration and strain responses of the OWT model and can be potentially applied to the remote monitoring of real OWTs. The EDAs based model updating technique is demonstrated to be successful for the support condition monitoring of the OWT system, which is potentially useful for other model updating and condition monitoring applications.
Engineers perform fatigue assessments to support structural integrity management. Given that the purpose of
these calculations is linked to problems of decision making under various sources of uncertainty, probabilistic
methods are often more useful than deterministic alternatives. Guidance on the direct probabilistic application of procedures in existing industrial standards is currently limited and dependencies between marginal probabilistic models are generally not considered, despite their potential significance being acknowledged. This
paper proposes the use of Bayesian data analysis as a flexible and intuitive approach to coherently and consistently
account for uncertainty and dependency in fatigue crack growth rate models. Various Bayesian models
are established and presented, based on the same data as the existing models in BS 7910 (a widely used industrial
standard). The models are compared in terms of their out of sample predictive accuracy, using methods with a
basis in information theory and cross-validation. The Bayesian models exhibit an improved performance, with
the most accurate predictions resulting from multi-level (hierarchical) models, which account for variation
between constituent test datasets and partially pool information.