Johan Maljaars

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• Prof.dr.ir.
• Professor (Full) at Eindhoven University of Technology

EN 1990 “Eurocode: Basis of structural design” defines structural reliability as the ability of a structure to fulfil the specified requirements during the service life for which it has been designed; the notion covers safety, serviceability and durability. According to this definition reliability is the concern of all parts of the whole suite of E...

Parts manufactured by wire arc additive manufacturing (WAAM) are characterized by a peculiar surface morphology, namely, surface waviness, that negatively affects the fatigue performance. To exploit the full potential of WAAM and minimize the need for postproduction work, it is crucial to utilize the components in the as‐built state. This is becaus...

This paper presents the results of experimental tests and proposes a numerical framework for the prediction of the fatigue behaviour of friction stir welded (FSW) butt-lap joints of aluminium bridge deck extrusions. Fatigue test specimens made of welded real roadway bridge deck extrusions were subjected to cyclic bending under different loading con...

Many old steel bridges contain hot riveted double strap butt joints. The fatigue life of these joints is subject of growing concern. We collected 629 fatigue tests, showing that the fatigue resistance expressed as the net section stress range is extremely scattered. Based on the theory of mechanics and the finite element method, we developed analyt...

Metal structures often exhibit macroscopic defects from which cracks can nucleate during cyclic loading. The current work presents a two-scale approach to enable the prediction of crack nucleation from such defects by taking into account local microstructure features. The geometrical description of the defect and associated non-homogeneous strain f...

Friction stir welding (FSW) has shown considerable promise for highway aluminum bridge deck fabrication but lacks specific quality control guidelines for fit-up defects. This study conducts a performance-based (PB) quality control assessment of butt-lap FSW joints for highway bridge decks. Five FSW conditions were simulated, including a standard co...

The accuracy of stress estimates in Orthotropic Bridge Decks (OBD) may be negatively impacted by the complex load transfer and asphalt properties. Yet, accurate stress estimates are crucial for optimal fatigue verifications. A field measurement and modelling study has been conducted to evaluate the accuracy of finite element (FE) models. The level...

The damage tolerant design philosophy is based on periodical inspections and provides safe bridge operation preventing fatigue cracks from growing up to a critical size. It is possible to optimize the management costs of a bridge throughout its life by designing the inspection frequency, which depends on the capabilities of the inspection method. H...

For the fatigue design of steel railway bridges in Europe, the European standards EN 1991‐2 and EN 1993‐2 provide a factored Load Model '71, called the lambda model. The stress range in the fatigue detail of study should be determined with this model. Engineers can easily verify their structural design for fatigue by comparing this stress range to...

Numerous bridges and viaducts built in Western Europe in the middle of the 20th century are now in service for more than 50 years. Aging and changes in societal demands result in a gradual decline of their technical and functional performance. This consequently forces responsible authorities to replace the obsolete infrastructure in the coming deca...

The design of orthotropic bridge decks (OBD) is driven by fatigue. The Eurocode on fatigue of steel structures – prEN 1993‐1‐9:2023 – provides fatigue resistance (S‐N) curves for relevant details in OBD. These curves are to be used with the far field (nominal) stress. However, due to the complex geometry and loading of OBD, the nominal stress is no...

Sandwich panels consist of two thin‐walled steel faces plus an insulation core. For this core, materials are selected that provide high (shear) stiffness and high thermal resistance. When the panels are subject to fire, the (a) temperature‐dependent behaviour of the steel faces and (b) the possible chemical reactions of the insulation core should b...

This paper presents a method of estimating the hot‐spot stress in orthotropic bridge decks (OBD) using a shell Finite Element (FE) model, in which local thickening is applied around the welded. The dimensions of the area of local thickening are a function of the weld throat thickness and the plate thickness. A comparison of this method with 3D soli...

Purpose Simulations exist for the prediction of the behaviour of building structural systems under fire, including two-way coupled fire-structure interaction. However, these simulations do not include detailed models of the connections, whereas these connections may impact the overall behaviour of the structure. Therefore, this paper proposes a two...

To understand sandwich panel behaviour under fire, expensive full-scale tests, or potentially more efficient fire-structure simulations can be carried out. However, these simulations have only been demonstrated to work for specific applications, either on the global scale (a fire on a simple panel) or on the small scale (a temperature load on a sin...

The fatigue life of orthotropic steel bridge decks in road bridges depends on the load effects exerted by heavy lorries. The contact surface of tyres is one of the important variables. Measurements described in the literature demonstrate that the actual tyre contact surfaces of today's traffic representative for Europe are shorter and slightly wide...

This paper presents the results of experimental tests and a numerical investigation of the fatigue behavior of butt-lap friction stir welded (FSW) joints used in highway bridge decks made from aluminum extrusions. A large-scale fatigue experiment was designed to initiate fatigue failure in the butt-lap FS welds joining two full-scale aluminum extru...

Train axle load measurements performed between 2012 and 2019 at 87 locations in the Dutch railway network are used to evaluate fatigue of railway bridges. The theoretical fatigue damage using realistic influence lines is determined for the measured loads and for the load model from Eurocode EN 1991-2 Annex D. It appears that this load model is (ver...

Capacity design for bolted connections in tension means that yielding of the gross cross‐section is decisive over the ultimate resistance of the net cross‐section. If the requirement for capacity design is met, ductile connection behavior is achieved, and brittle failure is avoided. However, in many practical cases the bolt holes are too large to s...

This paper presents a probabilistic framework to derive the safety factors for fatigue of steel and composite steel concrete road bridges. Engineering models are used for the design and the safety factor is derived in such a way that the design meets the target reliability set by international Eurocode and ISO standards, estimated using measured da...

The failure assessment line (FAL) describes the interaction between plastic failure and fracture of flawed steel components subjected to tension or bending. This paper quantifies the model uncertainty of the FAL as provided in the internationally used British Standard BS 7910:2019 by comparing the assessment with the actual failure load of 82 wide...

p>Fatigue considerations dominate the design of new, innovative steel bridge decks. Weighing bridge deck al- ternatives requires representative values for contact areas and contact stress distributions of the tyres of heavy vehicles. Fatigue load model 4 in the Eurocode EN 1991-2 (FLM4) provides tyre contact areas together with a set of axle loads....

I-shaped hoisting spreader beams are widely used in practice when lifting heavy objects by crane. In general, I-shaped beams that are subjected to a bending moment may be sensitive to lateral torsional buckling. Eurocode 3 (1993-1-1 [1]) provides a calculation method to determine the lateral torsional buckling resistance using buckling curves. The...

A multi-scale simulation approach is proposed to predict the fire resistance of structures comprising connections by bolts, as a supplement to an existing two-way coupled CFD-FEM method. In the existing model, fire is modelled by CFD, and its effects on the overall structure are found via thermodynamic and thermomechanical models. In this paper, de...

Many steel rope systems are subjected to fluctuating tensile loads and therefore can fail due to fatigue. Available fatigue test data indicate that rope diameter, mean stress, socket type, lay angle and rope length influence the fatigue resistance. Most of the tests were terminated before full failure of the ropes. This paper shows that the test te...

Many steel rope systems are subjected to fluctuating tensile loads and therefore can fail due to fatigue. There are indications that the fatigue resistance of full-locked coil ropes is somewhat lower than that of other types of rope. Fatigue test data on full-locked coil ropes have been collected, but they terminate at different conditions. A semi-...

Bolts and bolted connections are frequently used in civil engineering steel structures. This paper presents a meta study where a few thousand fatigue tests on these elements are evaluated. The evaluation reveals that current specifications in design standards need updating to account for the relevant stress parameter and production methods. This su...

A two-scale finite element model is proposed to improve two-way coupled fire-structure simulations. The model consists of (i) a global-scale model, which accounts for the structure, and (ii) a small-scale model for each connection. Structural parts on the global scale are connected by spring elements, which stiffness properties are updated by the s...

Crack closure effects during fatigue crack growth have been studied by many researchers with the finite element method, but appears difficult to accurately predict. Although quantification of crack closure may be a bridge too far, finite element models may help explaining observations from tests and give insight into trends. This paper studies crac...

This experimental study considers load sequence effects in fatigue crack growth in coupon specimens and in element specimens. The coupon specimens were standard edge crack configurations cyclically loaded under four point bending on base metal and welds, whereas the element specimens were full-scale axially loaded tubular joints. Whereas load seque...

Load sequence effects in fatigue crack growth, such as retardation and acceleration due to a large overload (OL) and underload (UL), can dramatically change the (remaining) fatigue life. These effects can be determined using analytical and numerical tools, often trading accuracy for a steep increase in required calculation time. This paper describe...

The effect of embedding in concrete on the fatigue performance of steel reinforcement bars is not evident. Some test series provided in literature demonstrate a higher fatigue resistance of embedded bars as compared to bars in air, whereas others provide a lower resistance. In addition, debate exists on the mechanisms behind the difference between...

A standalone MatLab app is provided for fitting constant amplitude fatigue test data using the 6PRFLM.

This study presents calibration and validation of a cohesive extended finite element model for fatigue crack propagation in ductile materials. The approach relies on a separation between plasticity around the crack tip and fatigue crack growth at the crack tip such that the influence of plasticity on fatigue driving forces is predicted. This implie...

Curved aluminium extrusions are applied in a wide range of industrial applications. Because extrusions are initially straight, an additional process is required to curve the product. Undesired wrinkling of the plate part at the inner radius is frequently observed during the curving process. Wrinkling has already been extensively studied for the rot...

p>Probabilistic fatigue life prediction models of welded steel joints are often used to estimate the level of safety, which is given in terms of the probability of failure or the reliability index as a function of the applied load cycles. Prediction models based on fracture mechanics allow taking into account the effect of inspections on the estima...

p>Many developed countries have a national road network including a significant number of bridges in need of renovation or replacement in the coming years. The reason for this is their technical and functional capacity becoming insufficient due to aging and changes in societal demands. Therefore, these bridges need to be adjusted or replaced. Natio...

A numerical model for corrosion pit propagation under mechanical loading is presented. The level set method is used for corrosion front tracking and also enables the domain to be split into a solid and a pit domain. In the pit the diffusion of atoms originating fromthe dissolution process occurring at the pit front is simulated. Themodel is capable...

Propagation of weld toe cracks under cyclic loading is often predicted using fracture mechanics. In as welded condition, most of the propagation life is spent as a short crack, which is known to behave differently than a long crack. Several studies have been conducted with the aim of correlating the fatigue crack growth rate and the threshold condi...

Bolted connections are applied in many aluminium structures. Stainless steel bolts are often preferred over carbon steel bolts in aluminium connections to prevent galvanic corrosion. However, current design standards and guidelines do not allow for using preloaded stainless steel bolts in slip resistant connections, mainly because of a lack of know...

A R T I C L E I N F O Keywords: Weigh in motion Fatigue Lorry Heavy vehicle Bridge Load model A B S T R A C T Fatigue verification of bridge structures requires information on the loads induced by heavy vehicles, which can be obtained from weigh in motion measurement (WIM) systems. The current fatigue load models applied in Europe are based on traf...

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 non-load 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 structura...

Rolled steel plates and sections are often applied in structures in such a way that the principal load direction corresponds with the rolling direction. Examples are beams, arches, or pylons of bridges, supporting beams of ship decks, and the main elements of crane structures. However, some types of structure are subjected to a multiaxial stress st...

Hot-riveted connections have been widely used in the past for metallic bridges, of which a large part is still in service, making relevant the assessment of their fatigue life. Previous studies have shown that the fatigue behavior of hot-riveted connections depends on many factors; among these, the residual tensile force in the rivets that clamps t...

As part of the ongoing revision of EN 1993‐1‐11 ”Design of structures with tension components“, the current fatigue design rules have been subjected to a critical review. This has resulted in modifications and amendments, including the adjustment of several parameters. This paper provides an introduction to as well as background information on thos...

This paper presents a probabilistic fatigue life prediction model for welded details subjected to variable amplitude random loading, using the nominal stress approach. The proposed model makes use of CA S-N curves in combination with the relative damage rule which allows to globally account for load interaction effects, and the damage limit concept...

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 safe-life method is used for details where local formation of cracks could rapidly lead to failure or for det...

During the ongoing revision of EN 1993‐1‐11 “Design of structures with tension components” the current fatigue design rules were subjected to a critical review. This results in modifications and amendments, including the adjustment of several parameters. The present paper gives an introduction as well as background information on those changes.

Two 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 elastic-plastic fracture mechanics is accurate but requires a time consuming elastic-plastic finite element analysis. The second method estimates the critical condition with a...

Before bolts were invented, hot-riveting was employed as technological process to produce built-up 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 i...

A self-supporting sandwich panel façade system under fire is studied. First, a thermomechanical FE model, which comprises the complete façade system, and incorporates material degradation and geometrical nonlinear behaviour except for the insulation material and connections, is loaded by a fire temperature curve. Eurocode design rules then predict...

Many existing steel bridges are constructed by using hot-driven steel rivets as fasteners. It is known that the fatigue strength of these joints depends on their geometry, since it affects the load transfer mechanism and, therefore, the severity of the stress concentration. Attempts have been taken in the past to provide the characteristic fatigue...

Structures are subjected to cyclic loads that can vary in direction and magnitude, causing constant amplitude mode I simulations to be too simplistic. This study presents a new approach for fatigue crack propagation in ductile materials that can capture mixed‐mode loading and overloading. The extended finite element method is used to deal with arbi...

ratio on the constant amplitude fatigue limit (CAFL). However, fatigue test data show that there is a substantial influence of the stress ratio on the CAFL. In this study, a simple fatigue design criterion for riveted members is proposed taking into account the effect of stress ratio. The applied method is based on the constant life diagram (CLD) m...

p>Orthotropic Steel Decks (OSDs) are widely used in long span bridges because of their extremely light weight when compared to their load carrying capacity. These deck types typically consist of a grillage of closed trapezoidal longitudinal stiffeners and transverse web stiffeners, welded to a deck plate. As a result, fatigue problems occur due to...

In Memoriam of Prof. Dr. Bernt Johansson The use of high‐strength steels (HSS, 460 < fy ≤ 700 MPa) and particularly very high‐strength steels (VHSS, fy > 700 MPa) is limited in steel structures in civil and offshore engineering. This is due to a lack of experience in structures made of these materials and a lack of understanding of the structural p...

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 datas...

This study examines residual stresses in bead-on-plate welded specimens in transverse direction over the thickness of the plate, using a combination of experimental and numerical procedures. Dilatometer and tensile tests were used to determine the phase transition temperatures with associated volumetric strains and the stress-strain relationships o...

Steel orthotropic decks in bridges and ferries have shown to be prone to fatigue cracking. A typical fatigue crack observed in these structures initiates at the root of the weld between the deck plate and stringer and grows into the deck plate. Due to limited fatigue test data available and the deviating characteristics of this type of crack as com...

Standards and guidelines for the fatigue design of riveted connections make use of a stress range-endurance (S-N) curve based on the net section stress range regardless of the number and the position of the rivets. Almost all tests on which S-N curves are based, are performed with a minimum number of rivets. However, the number of rivets in a row i...

Estimating and reducing uncertainty in fatigue test data analysis is a relevant task in order to assess the reliability of a structural connection with respect to fatigue. Several statistical models have been proposed in the literature with the aim of representing the stress range vs. endurance trend of fatigue test data under constant amplitude lo...

This paper investigates the differences in the predicted fatigue life of transverse welded steel joints and cover-plated beams considering statistically based fitting methods on fatigue test data and comparing the results with the S-N relation proposed in international standards. The test data fitting are performed using the Least Square Method (LS...

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: S-N curves in combination with Palmgren-Miner damage accumulation rule and linear elastic fracture mechanics...

Clause 6.2 of EN 1993‐1‐1 covers the cross‐sectional resistance of steel sections. The bending‐shear interaction design rules for I‐shaped cross‐sections 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 resista...

In design against fatigue, a lower bound stress range vs. endurance curve (S-N curve) is employed to characterize fatigue resistance of plain material and structural details. With respect to the inherent variability of the fatigue life, the S-N curve is related to a certain probability of exceedance, a percentile of the fatigue life. This paper is...

Modeling the stochastic evolution of a large-scale fleet or network generally proves to be challenging. This difficulty may be compounded through complex relationships between various assets in the network. Although a great number of probabilistic graph-based models (e.g., Bayesian networks) have been developed recently to describe the behavior of...

The last decade has seen a growing interest in cohesive zone models for fatigue applications. These cohesive zone models often suffer from a lack of generality and applying them typically requires calibrating a large number of model-specific parameters. To improve on these issues a new method has been proposed in this paper based on the Thick Level...

Many aluminium structures contain welded and bolted connections that are modeled as one or more equivalent T-stubs – also referred to as tension zone components – for the structural assessment. Knowledge on the structural behavior of such T-stubs is thus essential for proper designs. However, this behavior has never been checked for fire conditions...

Aluminium plates containing a single hole or multiple holes in a row are recently becoming very popular among architects and consultant engineers in many constructional applications, due to their reduced weight, as well as facilitating ventilation and light penetration of the buildings. However, there are still uncertainties concerning their struct...

Fatigue life or crack growth predictions that use information from crack inspections have been applied to offshore structures and, in recent years, also to steel bridges. Apart from inspection data, a probabilistic crack growth model and knowledge of the distributions and correlations of the variables are required for such predictions. The performa...

Markov-based models for predicting deterioration for civil infrastructures are widely recognized as suitable tools addressing this mechanism. The objective of this paper is to provide insights regarding a network of orthotropic steel bridges in terms of degradation. Consequently, a model combining a dynamic Bayesian network and a Markov chain is fi...

A probabilistic model is developed to investigate the crack growth development in welded details of orthotropic bridge decks. Bridge decks may contain many of these vulnerable details and bridge reliability cannot always be guaranteed upon the attainment of a critical crack. Therefore, insight into the crack growth development is crucial in guarant...

This paper considers local buckling of perforated square aluminium plates. Plates of various slenderness with simply supported edges and subjected to uniaxial compression are studied using the finite element method. Different perforation patterns are investigated, from a single circular hole to 25 circular holes distributed over the plate. A number...

Many welded steel structures in marine, offshore, and infrastructural industries are subjected to variable amplitude (VA) fatigue loads. It is well known that the level and sequence of the load cycles can cause crack growth retardation or acceleration and thus influence the fatigue life. An important sequence effect is generated by a large stress c...

Maintenance for highway bridges is crucial in order to keep the network in a satisfactory condition for users but is also a costly affair. This paper proposes a dynamic, Bayesian network-based model to provide cost-efficient strategies in the context of bridge network management. Characteristics related to uncertainties in both the degradation phas...

The Fatigue Ductile-Brittle Transition (FDBT) is a phenomenon similar to the fracture ductile to brittle transition, in which the fracture mode of the fatigue cracks changes from ductile transgranular to cleavage and/or grain boundary separation. Fatigue at temperatures below the FDBT has a much different crack growth rate than fatigue above that t...

Thermal gradients often occur in fire exposed structures. This paper considers thermal gradients over the cross-section of steel columns. By means of finite element simulations, the paper demonstrates that these gradients reduce the flexural buckling resistance of the columns. This is due to the eccentricity in the column created by the temperature...