bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cyclic Material Behavior of Ultra‐High‐Strength Fine‐Grained Steels and Welds for the Application in Fatigue Assessment Approaches
Authors: Möller Benjamin , Wagener Rainer , Melz Tobias 
Published: September 2019

ABSTRACTUltra‐high‐strength fine‐grained steels are a convenient choice in highly loaded structures in order to realize lightweight design applications. An example is given by the topside of the telescopic boom of truck cranes. Such applications belong to the low cycle fatigue, where the material behaviour predominantly elastic‐plastic. Within elastic‐plastic approaches, the cyclic material behavior is the basis for a fatigue assessment. Therefore, not just the cyclic material behavior of 8 mm thick sheet metal of two steels, S1100QL and S1300QL, but also their laser beam and laser hybrid welded butt joints is characterized based on strain‐controlled fatigue testing. The basis for the cyclic material behavior of welded joints is an integral treatment from base material to base material. On the one hand, the strain‐controlled fatigue results allow a comparison of investigated steels in base material and as‐welded state. Even though, a longer fatigue life of laser beam welds is found compared to laser hybrid welds, the as‐welded condition shows a reduced fatigue life in general. On the other hand, the cyclic material behavior leads to parameters that are applied in elastic‐plastic fatigue assessment approaches, e.g. the notch strain approach, and includes information about transient material effects. A cyclic softening of both the base material and the as‐welded state is identified. In the future, a functional relation of the parameters of the cyclic stress‐strain curve with the damage is capable to describe the cyclic softening.
Improved remaining fatigue life of an orthotropic bridge deck: Combination of analyses, tests and measurements
Authors: Unterweger Harald 
Published: September 2019

ABSTRACTPreviously to the renovation of a long steel highway bridge, built in 1969, the remaining fatigue life of the orthotropic bridge deck should be analysed. The bridge structure is a very slender box‐girder bridge with three spans (L = 120 + 210 + 82 = 412 m). The heavy traffic is very high, with approximately 1,2 million trucks per year in the busiest lane.This paper gives a summary of the comprehensive numerical analyses, combined with extensive measurements (traffic data, stress spectra at relevant details) and also fatigue tests on full scale test specimen. Fortunately, in front of the bridge an automatic lorry counting device was installed and therefore the numbers and types of lorries in each lane, on each day, within the last decade were well‐known.In addition, simplified models for the numerical simulation of the heavy traffic on the orthotropic bridge deck are shown, with comparison to field measurements of stress spectra under service conditions. These measurements were done to overcome the uncertainties in the simulation, e.g. overloads, specific lorry types, different positions within the lane and dynamic effects.Fatigue tests were done for the detail of the joint between the longitudinal ribs and the cross girder, with a non‐typical only one sided welded connection. For this detail also a very effective strengthening solution was developed and tested.
Fatigue behavior and retrofit of bulb rib orthotropic steel decks With R40 slits in cross beams
Authors: Nozawa Naoki , Sakano Masahiro , Tabata Akiko , Sugiyama Hiroki , Ishii Hironori 
Published: September 2019

ABSTRACTA number of fatigue cracking experiences have been reported at the lower part of cross beam slits intersected by bulb ribs with R less than 35mm. In this study, fatigue behavior of cross beam slits with R of 40mm is investigated and effectiveness of retrofitting methods of R dressing and small size attachments, through fatigue tests using three specimens cut out from a removed bulb rib orthogonal steel deck box girder bridge. The shape and size of R dressing were determined through finite element analyses. As a result, stress concentration was higher at the upper part than the lower part of slits. By the R dressing, stress concentration moved from fillet welds to R part in the mother material. By the small size attachment, stress concentration decreased at the upper part of slits. Fatigue cracks were initiated at the upper part of R40 slits and propagated into fillet welds between the deck plate and cross ribs without retrofitting methods, while no fatigue cracks were developed with R dressing and small size attachments. After fatigue cracks were initiated, small size attachments could stop propagation, of there cracks.
The impact of local geometry on the fatigue life of a welded structural detail
Authors: Skoglund Oskar , Leander John 
Published: September 2019

ABSTRACTFatigue often limits the capacity of welded steel bridges, and thus often governs the amount of steel required. The fatigue life is, to a large extent, governed by stress concentrations and the magnitude is controlled by local as well as global geometry; by improving the local geometry the stress raising effects can be lowered and by increasing the global dimensions the nominal stress can be reduced. The fatigue assessment format presented in the Eurocode gives little or no room for the designer to control the local geometry of the structural detail, and is often left with increasing the overall dimensions in order to improve the fatigue life of the structure. This paper aims at investigating the possible impact on the fatigue life of welded steel structures by different weld geometries. In this paper a vertical stiffener will be studied by fracture mechanics. The study showed that significant improvements in fatigue life can be made by small changes to the weld geometry and the most pronounced effect was by changing the weld toe radius, and for the case studied at least one higher detail category could be assigned to the vertical stiffener.
Optimized design of steel car parks for fully spread fires
Authors: Thaarup Martin , Giuliani Luisa 
Published: September 2019

ABSTRACTThe design optimization of steel structure is usually carried out by choosing a profile that minimizes the amount of steel, under the boundaries of carrying mechanical loads and being compliant with maximum allowed displacements. The fire verifications are typically performed at a later design stage by applying the amount of insulation needed to keep the profile below its critical temperature during fire. This strategy keeps the steel costs to a minimum, but often results in relatively high costs for insulating the structure, which may nullify the scope of the original design optimization. This study investigates possible beneficial effects of including fire verifications at the early design stage of a structure. The methodology is presented with reference to a steel car park structure insulated with intumescent paint against a fully spread fire and is based on the minimization of the sum of the steel and insulation costs. The results show that the optimization leads to a reduction of 36% of the material costs.The price is also compared to the case of an uninsulated structure designed against local fires. This design assumption allows avoiding fire insulation, but has been challenged by past cases of major fire spread, such as the recent car park in Liverpool. The paper shows that the conservative assumption of a full spread fire corresponds to the doubling of the material costs, when the structure is traditionally optimized by minimizing the amount of steel for the ordinary design conditions. However, the proposed optimization limits the cost increment to 19% of the material costs and just 6% of the total costs of the structure. This increment lies within the expected variation of costs during the realization of a structure and indicates that a higher safety level of steel car parks can be achieved, while maintaining a competitive market price against concrete structures.
Fire risks in suspension bridges
Authors: Narasimhan Harikrishna , Giuliani Luisa , Jomaas Grunde , Jensen Jakob Laigaard 
Published: September 2019

ABSTRACTLong‐span suspension bridges provide vital support to society and its development. With ever increasing road traffic, such bridges are increasingly exposed to greater risks from fires. Experience shows that a significant fire in a truck without dangerous goods (like the 2013 New Little Belt Bridge fire in Denmark) can grow rapidly to reach temperatures above 1000°C, thereby making it a fire comparable to the hydrocarbon fire test standard. Compared to fuel tankers, the relatively high frequencies of trucks carrying normal (but flammable) goods make such significant truck fires more likely. Significant fires on a suspension bridge can lead to strength reduction or cable failure that could result in a reduction in bridge load rating and a need for long‐lasting repairs. Such outcomes mean high societal costs due to long‐term disruption of the connectivity provided by the bridge. Hence, there is a need to systematically assess fire risks in suspension bridges, focusing on a) fire frequencies and proportion of significant fires that can affect key bridge elements, b) fire consequences to key bridge elements and c) implementing mitigation measures when needed. Main cables in a suspension bridge are vital for structural integrity and at the same time difficult and expensive to replace during the bridge lifetime. This means that, in addition to ensuring no cable failure and no bridge collapse during fire, non‐exceedance of critical temperatures that could result in extensive damages and/or irreversible strength loss after fire is also important. Evaluating cable performance with respect to such criteria requires a detailed modelling of heat transfer into the cable, taking into account the nature of fire, multiple heat transfer modes, packing arrangement within the cable and geometrical exposure conditions.The above issues are addressed and useful insights are provided to help in understanding the fire risk picture for suspension bridges.
General Method for the fire design of tapered steel columns: Out‐of‐plane flexural buckling
Authors: Maia Élio , Real Paulo Vila , Lopes Nuno , Couto Carlos 
Published: September 2019

ABSTRACTThe General Method (GM) covers the safety check of structural elements with complex support conditions and/or of non‐prismatic members. However, it's not widely validated at normal temperature and is inexistent in fire part of the Standard EN 1993‐1‐2. With that in mind, this investigation aims at proposing and validating the GM to perform the safety check of unrestrained tapered columns at elevated temperatures. This is done, first, by including, in the original formulation, the reduction of steel material properties with the temperature, and later by improving the EN 1993‐1‐2 out‐of‐plane buckling curve.With this novel approach, the GM shows good agreement to numerical results and produces accurate predictions of out‐of‐plane resistance for tapered columns at elevated temperatures.
Deformation of Installation Mounting Rails in Case of Fire: Deviation between strains acc. EN 1993‐1‐2 and tested strains above 760°C
Authors: Beiter Clemens , Reichel Susanne 
Published: September 2019

ABSTRACTCentral components of modular installation systems are thin‐walled mounting rails from cold formed steel, guiding loads from attached installations via bending to supports.For temperatures of 760°C and above calculations with the stress‐strain relationships of EN 1993‐1‐2 provide deviant and unsafe deformation results compared to large scale fire bending tests following the standard temperature‐time curve acc. to EN 1363‐1. Therefore, deflections of these mounting rails in case of fire could be reliably determined in the past only with large scale fire tests. As an important attribute of modular installation systems is their flexibility in geometry and load supporting configurations, fire tests for the deformation evaluation of mounting rails are either required to a significant extent or conservative approximations via worst case scenarios are used, leading to over engineered solutions.This article describes the evolving discrepancy of the stress‐strain formulation specified in EN 1993‐1‐2 compared to results of unsteady thermal creep tests between 700°C and 800°C for S250GD and S280GD steel grades. In addition, it describes a new method how reliable statements about deformations of thin‐walled profiles in case of fire based on unsteady thermal creep tests, numerical simulations and large scale validation testing can be made in a flexible manner.
Denmark: The Global Leader in Special Steel Structures
Authors: Støttrup‐Andersen Ulrik 
Published: September 2019

ABSTRACTAlthough small in size and without any domestic production of steel, Denmark has over the years contributed with a series of innovative steel structural designs, and today plays a key role globally in the design and construction of some special steel structures.Danish engineers have been pioneers internationally in many fields and have a good reputation worldwide. This is also the case within steel structures. Today, Danish consulting engineering firms are extremely big compared to the size of its native population. These firms contribute significantly to global ranking within special steel structures, for instance, masts and towers, steel foundations for offshore wind turbines and large span steel bridges. Additionally, Danish engineers and fabricators are at the forefront globally within steel structures for wind turbines.The Author has worked with structural steel design for more than 45 years in Ramboll– – the largest consulting engineering company in Denmark. He has participated in many innovative designs and contributed to the national and international standardisation of codes of practice.This paper introduces the global leads on special steel structures, as well as some innovative steel designs in Denmark. Out of the large portfolio of innovative steel structural projects performed by Danish engineers, only a small fraction of steel projects from the past 45 years are mentioned, primarily where Ramboll has been involved.
Comparative Study on the Fatigue Assessment Concepts for Horizontal Butt Welds of Wind Turbine Towers
Authors: Spüntrup Hendrik Schulze , Rauch Marion , Knobloch Markus 
Published: September 2019

ABSTRACTThis paper presents a comparative study on the fatigue life prediction of different fatigue assessment methods. The nominal stress concept, the local stress concept and a two‐stage‐model, which consists of the strain‐life approach and the crack propagation method are applied to compute the fatigue life of horizontal butt welds and to assess the methods capability to provide adequate prognosis of fatigue life of wind turbine towers. The comparative study shows the impact of weld imperfections on the fatigue life according to the local stress concept and the strain‐life approach. The later approach even considers the influence of actual geometry and imperfection on the total damage sum. The approach has a great potential to accurately predict the fatigue life of butt welds and notch details of wind turbine structures with precise manufacturing, sophisticated processes and high‐quality control.
FE Simulation of High Frequency Mechanical Impact (HFMI) Treatment – First Results
Authors: Gkatzogiannis Stefanos , Knoedel Peter , Ummenhofer Thomas 
Published: September 2019

ABSTRACTHigh Frequency Mechanical Impact treatment is investigated numerically in the present paper. A first‐step numerical dynamic analysis is carried out using the solver LS‐Dyna. The treatment of an unnotched component of S355 is simulated. The strain rate dependent material parameter Cowper‐Symonds is calibrated for the investigated material based on data from literature. Goal of the present analysis is to act a first step for a robust engineering approach, which will calculate with sufficient preciseness the residual stresses introduced by this post‐weld treatment. The calculated residual stresses of the present investigation are compared with respective measurements found in literature. Deviation between measured and simulated residual stresses indicates the need for further improvement of the present model.
State‐of‐the‐Art Framework for Structural Design of Offshore Wind Jacket Foundations
Authors: Nielsen Martin Bjerre , Jensen Jacob Fisker , Harper Christopher , Knudsen Lennart Skovbjerg , Pedersen Ronnie Refstrup 
Published: September 2019

ABSTRACTA state‐of‐the‐art framework for design of jacket foundations for offshore wind turbines is presented. It is illustrated how an efficient, yet highly accurate structural model can be achieved by a combination of a comprehensive beam finite element model and more detailed shell/solid finite element models, where the former suffices for representing the overall global behaviour, while the latter improve the representation of non‐trivial structural details such as the transition piece and tubular joints. Hereby the verification of the majority of the structural elements according to various design codes can be automated on beam element level, while the fatigue performance via the hot‐spot method as well as detailed stress and buckling analysis for relevant joints and details can be performed based on the detailed shell/solid finite element models readily available for stiffness representation. This computational framework ensures consistency between the local and global description levels and an efficient cloud interface facilitates the thousands of design load cases that typically requires consideration for a full detailed design to be simulated within a reasonable amount of time.
A consistent approach for flexural and lateral torsional buckling as basis for a general buckling curve
Authors: Feldmann Markus , Nonn Jonas , Heinemeyer Christoph 
Published: September 2019

ABSTRACTChapter 6.3.4 of EN 1993‐1‐1 (1) deals with the General Method for the verification of stability problems of in‐plane loaded frames or beams. For the general case of having combined moment and normal force the method provides two different approaches to determine the reduction factor for out‐of‐plane buckling. They accord to the special case of lateral torsional buckling (“LTB” – i.e. with moment only) and flexural buckling (“FB” – i.e. with normal force only) on the other hand. However, in general cases this produces inconsistencies leading to conflicts with the intended generality of the formulation and finally to incorrect results. Because the individually combined effect of the in‐plane actions My and N are the reason for the out‐of‐plane instability. This requires a reduction considering the individual load combination. To find a solution for this, the in‐plane‐ and out‐of‐plane effects can be put together in a general formulation to obtain a buckling curve for combined moment and normal force ensuring consistency with the buckling curves of the special cases. By this the choice of buckling curves in Eurocode 3 clause 6.3.4 (1) can be improved.
New stability design methodology through overall linear buckling analysis
Authors: Szalai József , Papp Ferenc 
Published: September 2019

ABSTRACTTwo new stability design methods are presented: the Overall Strength Reduction Method (OSRM) and the Overall Imperfection Method (OIM). Both methods are based on the linear buckling analysis (LBA) of global structural models and use the standard reduction curves. The OSRM is formulated in the classic way using generalized slenderness and reduction factors while the OIM uses equivalent amplitude for the buckling mode based geometrical imperfection. It is shown that both methods have the same mechanical background which is built on two essential components: (1) the generalized form of an Ayrton‐Perry (or Perry‐Robertson) type strength reduction method for basic reference members and (2) a generalized transformation technique connecting the real members of the global structural model with the proper basic reference member. The first component is a mechanically consistent extension of the model behind the traditional buckling curves used only for specific stability cases like flexural buckling of columns or lateral‐torsional buckling of beams so far. The second component can be regarded as the generalization of the well‐known effective length approach. The new design methods cover all types of buckling modes (flexural, torsional, flexural‐torsional, lateral‐torsional or any interaction), which can be calculated by LBA of structural models composed of uniform or non‐uniform members with arbitrary cross‐sections and support conditions and subjected to any complex loading (e.g. biaxial bending with moment gradient, direct torsion effects etc.). There is no need for any additional input for the calculations (like effective length factors, unrestrained lengths of beams, moment gradient factors, equivalent length for the imperfection amplitude etc.) since all the necessary information is received from the elastic critical load and buckling mode shape. This paper clarifies the mechanical interpretation and proper calculation of all the components of the two methods and shows some comprehensive validation study on the performance.
Influence of Slenderness Ratio on the Buckling Behaviour of Curved Panels in Pure Shear
Authors: Van Staen Gilles , De Backer Hans , Van Bogaert Philippe 
Published: September 2019

ABSTRACTCurved steel plates are commonly used in aerospace and naval engineering, using very thin plates in order to create lightweight structures. In recent years, the use of this kind of plates is extended towards bridge design, with several examples in Belgium. Since bridges have to carry larger loads, the thicknesses of these plates increase up to several centimetres. The decreased plate slenderness influences the buckling behaviour of the plates, leading to elastoplastic buckling. Multiple finite element models are created to investigate the buckling response of these plates. A single plate with simply supported and clamped supported edges are subjected to pure shear. The parameters used are the plate thickness and the curvature ratio in order to have a large spectrum of stability influence. Results show that for the perfect plates the buckling behaviour changes with increasing curvature. With the use of the American Specifications AISI and their specifications for flat plate thicknesses, new rules are determined to predict the buckling behaviour for all kinds of curved panels.
Experimental behaviour of stainless steel cellular beam in fire
Authors: Malaska Mikko , Cashell Katherine , Alanen Mika , Mela Kristo , Afshan Sheida 
Published: September 2019

ABSTRACTThis paper presents a description and the analysis of a fire test on a cellular beam made from grade 1.4301 stainless steel. Cellular beams are increasingly popular in the construction as they provide a structurally and materially efficient design solution as well as allowing the passage of services. In addition, stainless steel is also increasing in popularity for structural applications owing to its inherent durability and ductility, as well as other attractive properties such as structural efficiency and low maintenance requirements. However, the behaviour of stainless steel cellular beams in fire has received little attention from the research community until recently. In the current paper, a description is presented of an experimental investigation into the fire behaviour of grade 1.4301 stainless steel cellular beams. The experimental arrangements are described together with the details of the specimen. The test occurred at the fire testing laboratory at Tampere University, Finland. For the member test, the beam spanned 4,3 m, with an overall depth of 290 mm and 200 mm diameter openings along the span. It was found that the unprotected beam lasted for 29 minutes during the test, after being exposed to a standard fire, and the experiment was eventually stopped due to excessive rate of deflection. The test specimen has been analysed using available design methods and the results are presented herein.