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departmentresearch group programmeprojectcoordinates)uuid:896ddaa1322642f4ae15d8279a08343cDhttp://resolver.tudelft.nl/uuid:896ddaa1322642f4ae15d8279a08343cnEstimation of the Structural Reliability for Fatigue of Welded Bridge Details Using Advanced Resistance Models)Leonetti, D.; Snijder, H.H.; Maljaars, J.This present paper concerns the application of probabilistic fatigue life prediction models based on S N curves aiming at the estimation of the safety level for a nonload carrying cruciform joint. The safety level is expressed in terms of the reliability index as a function of the number of applied cycles. Estimating the reliability of a structural component against fatigue failure is relevant for both new and existing structures. The analysis is executed considering three models. For each of them, the input random variables are given in a probabilistic manner, based on fatigue test data from the scientific literature. The effect of the model uncertainty on the model response is quantified for both the load and the resistance side, demonstrating its relevance. Moreover, it has been shown that a 0.5 to 1 increase in the reliability index is achievable by applying the newly proposed, more complex model.Fatigue; Steel bridges; Welded joints; Structural reliability; Uncertainty; Buildings and Infrastructures; 2015 Urbanisationenarticle)uuid:15629fdc90be4011a3e7661c36486076Dhttp://resolver.tudelft.nl/uuid:15629fdc90be4011a3e7661c36486076Fracture mechanics based fatigue life prediction for a weld toe crack under constant and variable amplitude random block loading Modeling and uncertainty estimation)Leonetti, D.; Maljaars, J.; Snijder, H.H.Linear elastic fracture mechanics; Fatigue crack growth at weld; Cyclic Rcurve; Mechanically short and long cracks; Buildings and Infrastructures; 2015 Urbanisation)uuid:354613e6f8ea410088cd1c0c4303388bDhttp://resolver.tudelft.nl/uuid:354613e6f8ea410088cd1c0c4303388buAdded value of regular inservice visual inspection to the fatigue reliability of structural details in steel bridges(Hashemi, B.; Maljaars, J.; Snijder, H.H.In order to design structural details of bridges for fatigue, the current version of the Eurocode for steel structures recommends partial factors for fatigue resistance based on the consequences of failure and on the maintenance method. The safelife method is used for details where local formation of cracks could rapidly lead to failure or for details not accessible for inspection and has a relatively high partial factor. The damage tolerant method, on the other hand, is used for cases where fatigue crack initiation does not result in immediate failure so inspection and repair can be performed. In the current Eurocode, this comes with a relatively low partial factor. However, since the probability of crack detection of visual inspection by the naked eye is considerably different from more detailed inspection methods, the required partial factor to design a bridge for fatigue should be based on the way and level of inspection planned during the bridge service life. As a common practice, for most bridges, only visual inspections in short time intervals are carried out. In this paper, the added value of periodic visual inspection on the reliability status of a steel railway bridge is studied. The probability of failure after performing visual inspection is investigated by two approaches: 1) A statistical study on the main causes of bridge failure carried out by other researchers to find the relation between the safelife design method and the design method considering visual inspection; 2) Conducting a survey to collect experts opinions on the matter and using a Bayesian algorithm to assign a probability distribution function to each opinion. A relation between reliability indices for the cases where a bridge is designed < with and without considering the inservice visual inspection, is derived.KBuildings and Infrastructures; 2015 Urbanisation; Architecture and Buildingconference paper)uuid:620061f0075f4e27ad852109d3a32e54Dhttp://resolver.tudelft.nl/uuid:620061f0075f4e27ad852109d3a32e54fSimplified contraintmodified failure assessment procedure for structral components containing defectsTwo basic procedures are currently available to determine the critical condition of a flawed structure, at which unstable crack extension may occur. The first method based on elasticplastic fracture mechanics is accurate but requires a time consuming elasticplastic finite element analysis. The second method estimates the critical condition with an interaction diagram between linear elastic fracture mechanics describing brittle fracture, and a limit load analysis of the net section, i.e. the unflawed ligament. This method is simpler to use but has a lower level of accuracy. The current paper provides a third option, consisting of a constraintmodified failure assessment procedure. It uses a linear elastic solution for evaluating brittle fracture and a simplified elasticplastic analysis for evaluating plastic collapse. This third option provides good agreement with three considered tests.Buildings and Infrastructures; 2015 Urbanisation; Failure Assessment Diagram; Engineering Critical Assessment; Constraint; SIF; TStress; Plastic collapse; Neuber; Triaxiality)uuid:8fdf675ea4684b548648e375a4044905Dhttp://resolver.tudelft.nl/uuid:8fdf675ea4684b548648e375a4044905QFatigue life prediction of hotriveted shear connections using system reliabilityyBefore bolts were invented, hotriveting was employed as technological process to produce builtup structural members of steel structures. Nowadays, these structures being still in service and susceptible to fatigue failure,they need to be assessed for their remaining service life. To estimate the fatigue life distribution of riveted connections is, therefore, a topic of relevance. A system reliability model for estimating the probabilistic fatigue life of riveted shear connections is proposed in this paper. Similarly to other models available in the literature, the failure of the connection is modelled by evaluating potential failure at identified critical locations. In addition to these existing models, the proposed formulation is able to consider: (1) the dependency between failure at different critical locations by updating the state of stress given that a failure has occurred and evaluate the residual fatigue life considering the cumulated damage, and (2) the failsafe behaviour of the connection by using system reliability. Thus, it is possible to evaluate the effect of the position and the number of the rivets on the fatigue life of the connection. The stress and strain field is obtained using the finite element method and the fatigue life estimation is performed using the strainlife approach. The fatigue resistance of the plain material, the rivet clamping force, and the friction coefficient are considered as stochastic quantities. The constant amplitude fatigue life predicted by the reliability model is compared with three datasets of riveted double shear connection having different geometries. In addition, several analyses are performed: (1) a sensitivity study to determine the relationship between the input parameters and the fatigue life, (2) a comparison with other reliability models, and (3) a comparison with a similar connection having a different number of rivets.Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Riveted connections; Reliabilitybased fatigue; Clamping force; Multiple site damage; Constant amplitude loading)uuid:f81dbe543f9942e796c64d052c15018fDhttp://resolver.tudelft.nl/uuid:f81dbe543f9942e796c64d052c15018fyRepresentativeness of compressed flange behaviour for trapezoidal stell sheeting under combined web crippling and bending;Hofmeyer, H.; Vervoort, E.M.C.; Snijder, H.H.; Maljaars, J.An existing theoretical model indicates that the beh< aviour of trapezoidal steel sheeting under combined web crippling and bending moment may be modelled by only the sheeting's compressed flange. Therefore, this paper presents finite element models that simulate only the compressed flange of the sheeting, applying a prescribed displacement field along the flange longitudinal edges to simulate the loading of the bending moment. Seven different and increasingly complex types of these finite element models of a flange are compared with verified finite element models of sheeting for (a) first yield load; (b) ultimate load; (c) yield line patterns; and (d) outofplane deformation patterns. It is concluded that a bottom flange only, or a flange with a rounded bottom corner and load bearing plate do not predict (a) and (b) for sheeting correctly. A moving load bearing plate improves to some extent the prediction of (d) and in combination with an imposed curvature on the flange also (a). Future work should investigate the introduction of large, webcrippling deformation sized imperfections in the flange models, also for flanges representing secondgeneration sheeting.Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Trapezoidal Sheeting; Web Crippling; Bending Moment; Finite Element Model; Compressed Flange)uuid:960312a25b3643a89d92ae143b550972Dhttp://resolver.tudelft.nl/uuid:960312a25b3643a89d92ae143b550972OPartial factors for fatigue loads in the Eurocode system for road bridge design*Hashemi, S.B.; Maljaars, J.; Snijder, H.H.In the Eurocode system, for fatigue design of bridges, the recommended partial factor for fatigue traffic loads is set to 1. In this paper, the adequacy of this approach is investigated by performing a reliability analysis on two types of welded joint in a main girder of a steel motorway bridge. For this purpose, a weigh in motion measurement dataset belonging to a main Dutch motorway has been compared with the fatigue load model 4 of Eurocode EN 19912 with respect to the stress spectrum and the fatigue damage of two structural steel details. Several structural schemes have been considered to study the effect of the shape and length of the influence line. The distributions of the stochastic variables such as dynamic amplification, accuracy of the structural model, and future traffic trends have been estimated or taken from literature. Partial factors for fatigue loads have then been calibrated in such a way that the target reliability is obtained. The influence of each stochastic variable on partial factors has been studied by derivation of the sensitivity factors. The results show that a considerably higher fatigue partial factor is required for fatigue loads on road bridges than the value of 1 currently recommended in EN 19912.KBuildings and Infrastructures; Architecture and Building; 2015 UrbanisationbookPart)uuid:fab941b00ceb47b5a3efd1cd746925d3Dhttp://resolver.tudelft.nl/uuid:fab941b00ceb47b5a3efd1cd746925d3tReliabilitybased fatigue life estimation of shear riveted connections considering dependency of rivet hole failures+Leonetti, D.; Maljaars, J.; Snijder, H.H.B.6Standards and guidelines for the fatigue design of riveted connections make use of a stress rangeendurance (SN) curve based on the net section stress range regardless of the number and the position of the rivets. Almost all tests on which SN curves arebased, are performed with a minimum number of rivets. However, the number of rivets in a row is expected to increase the failsafe behaviour of the connection, whereas the number of rows is supposed to decrease the theoretical stress concentration at the critical locations, and hence these aspects are not considered in the SN curves. This paper presentsa numerical model predictingthe fatigue life of riveted connections by performing a system reliability analysis on a double cover plated riveted butt joint. The connection is considered in three geometries, with differentnumber of rivets in a row and differentnumber of rows. The stress state in the connection is evaluated using a finite element model in < which the frictioncoefficientand the clamping force in the rivets are considered in a deterministic manner. The probability of failure is evaluated for the main plate, and fatigue failure is assumed to be originating at thesides of therivet holes, the critical locations, or hotspots. The notch stress approach is applied to assess the fatigue life, considered to be a stochastic quantity. Unlike other system reliability models available in the literature, the evaluation of the probability of failure takes into account the stochastic dependence between the failuresat each critical location modelled as a parallel system, which means considering the change of the state of stress in the connection when a ligament between two rivetsfails. A sensitivity study is performed to evaluate the effect of the pretension in the rivet and the friction coefficient on the fatigue life.Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Failure analysis; Fatigue of materials; Friction; Location; Reliability analysis; Stochastic models; Stochastic systemsEDP Sciences)uuid:0f43ded3dd684d0494219b138ab516f2Dhttp://resolver.tudelft.nl/uuid:0f43ded3dd684d0494219b138ab516f2Compatibility of SN and crack growth curves in the fatigue reliability assessment of a welded steel joint. 2nd International Conference on Structural Integrity, ICSI 2017, 47 September 2017, Funchal, Madeira, Portugal6Hashemi, B.; Maljaars, J.; Leonetti, D.; Snijder, H.H.Reliability analysis is a crucial phase in assessing the safety status of new and existing structures. One of its applications is to predict the fatigue life of fatigue prone details. Two models are used to formulate the fatigue limit state: SN curves in combination with PalmgrenMiner damage accumulation rule and linear elastic fracture mechanics using fatigue crack growth rate curves. Within each model, choices must be made on the values of the variables and these choices are sometimes different in different standards. This study investigates the consistency between the standards by determining the failure probability of the different models and values for a transverse butt weld joint under Variable Amplitude Loading. Partial factors required for the design are then derived as a function of the required reliability for each model and associated values. The influence of the uncertainties related to each involved variable is evaluated by performing a sensitivity analysis.2015 Fluid & Solid Mechanics; SR  Structural Reliability; TS  Technical Sciences; Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Fatigue reliability assessment; Probabilistic method; SN curves; Linear Elastic Fracture Mechanics; Partial Factors)uuid:afdc973f09a34c5892351183d9b8441dDhttp://resolver.tudelft.nl/uuid:afdc973f09a34c5892351183d9b8441dYFitting fatigue test data with a novel SN curve using frequentist and Bayesian inferenceIn design against fatigue, a lower bound stress range vs. endurance curve (SN curve) is employed to characterize fatigue resistance of plain material and structural details. With respect to the inherent variability of the fatigue life, the SN curve is related to a certain probability of exceedance, a percentile of the fatigue life. This paper is concerned with modelling and estimating uncertainties in fatigue resistance of welded joints under constant amplitude loading. A new SN curve format is proposed and fitted to fatigue test data by using the Maximum Likelihood Method. The results have been compared with the Random Fatigue Limit Model and the Bilinear Random Fatigue Limit Model. The proposed SN curve appears to be more accurate in describing the SN relation in highcycle fatigue: it presents a smooth transition from finite to infinitelife regions and, differently from previous nonlinear SN relations with fatigue limit, this transition is controlled by an independent model parameter. Thereby it provides more flexibility for statistical fitting. In addition, a Bayesian framework is defined to fit the proposed relation including infor< mative and noninformative prior distributions. 2017 Elsevier Ltd2015 Fluid & Solid Mechanics; SR  Structural Reliability; TS  Technical Sciences; Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Bayesian inference; Constant amplitude loading; Frequentist inference; Maximum likelihood; SN curves)uuid:ec81d75f9835481b9e48cbbf81fad44aDhttp://resolver.tudelft.nl/uuid:ec81d75f9835481b9e48cbbf81fad44aUBendingshear interaction of steel Ishaped crosssections. Statistical investigation+Dekker, R.W.A.; Snijder, H.H.; Maljaars, J. Clause 6.2 of EN 199311 covers the crosssectional resistance of steel sections. The bendingshear interaction design rules for Ishaped crosssections make use of a reduced yield stress for the web area. On this basis, a reduced design plastic resistance moment allowing for the shear force is presented. The effect of shear on the bending resistance may be neglected if the shear force is less than half of the plastic shear resistance of the crosssection. Plasticity in the Eurocode is described by the wellknown VonMises yield criterion, however, the formula used for the reduced yield stress deviates from this criterion, resulting in sometimes greater and sometimes smaller values. The background of the Eurocode formula for reduced yield stress can be found in a publication by Drucker. The purpose of the present research is to investigate the influence of shear on the bending resistance of Ishaped steel crosssections with as result a possible reconsideration of the Eurocode design rules. At Eindhoven University of Technology an experimental investigation on bendingshear interaction in rolled steel Ishaped sections was performed. A numerical model was developed in Abaqus Finite Element software to simulate the experiments. With the validated numerical model a larger database of numerical test results was generated, which was subsequently used in a statistical analysis following Annex D of EN 1990 as further developed in the RFCS project Safebrictile. The statistical distributions of the steel properties recommended by Safebrictile were adopted. This paper presents the results of the statistical analysis and safety assessment of the strong axis bendingshear interaction design rule currently present in Eurocode 3. The parametric test group consists of HEA, HEM and IPE sections in the steel grades S235, S355 and S460: in total 180 numerical simulations with increasing amount of shear. A stressstrain model including strain hardening was used in the numerical simulations, since the influence of strain hardening is also largely present in the experimental test program. Based on strain hardening material behavior it is show in this paper that the current partial factor is unconservative for shear dominated beams and should be increased. Alternatively, the design rule should be modified.2015 Fluid & Solid Mechanics; SR  Structural Reliability; TS  Technical Sciences; Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation; Statistical evaluation; Crosssectional resistance; Bendingshear interaction; Isection)uuid:56e5006de31f48b487dd7a1c80d07f64Dhttp://resolver.tudelft.nl/uuid:56e5006de31f48b487dd7a1c80d07f64dNumerical investigation into strong axis bending shear interaction in rolled Ishaped steel sections+Dekker, R.W.A.; Snijder, B.H.; Maljaars, J.Clause 6.2.8 of EN 199311 covers the design rules on bendingshear resistance, taking presence of shear into account by a reduced yield stress for the shear area. Numerical research on bendingshear interaction by means of the Abaqus Finite Element modelling software is presented. The numerical model is validated against the experimental results. A material model based on various tensile test coupons was used incorporating the actual material properties within the tested crosssection. Strong axis threepoint bending tests were simulated by means of continuum solid elements. Good agreement was achieved between numerical and experimental result, both are compared with the EN 199311 < design rule.2015 Fluid & Solid Mechanics; SR  Structural Reliability; TS  Technical Sciences; Buildings and Infrastructures; Architecture and Building; 2015 Urbanisation)uuid:6ac8a0df7d2440e8a31d29e774cf9684Dhttp://resolver.tudelft.nl/uuid:6ac8a0df7d2440e8a31d29e774cf9684MExperimental study into bending shear interaction of rolled Ishaped sectionsThe bendingshear resistance of steel crosssections is covered in EN 199311 [1], taking presence of shear into account by a reduced yield stress for the shear area. An experimental investigation on bendingshear interaction of rolled HE280A beams in S235 and S355 was performed by means of 3point bending tests. Two criteria were considered for the evaluation of the experimental results, being the load at which complete yielding of the crosssection occurred and the ultimate resistance, i.e. the top of the loaddisplacement curve. Experimental results complied with the design rule when the criterion of the ultimate resistance was chosen. Yielding as failure criterion generated unconservative results for shorter beams2015 Fluid & Solid Mechanics; SR  Structural Reliability; TS  Technical Sciences; Buildings and Infrastructures; Materials; 2015 Urbanisation
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