bluuebunny/crossref_metadata_2025 huggingface dataset:
An experimentally validated study for open rib profiles steel‐concrete composite slabs behavior in partial connection
Authors: Soltanalipour Milad , Ferrer Miquel , Marimon Frederic
Published: September 2019

In this paper the strength of steel deck‐concrete composite slabs is studied. Conventional slabs with open and dovetail profiles are studied with different designs, galvanized and stainless steel. Partial connection method (PCM) in Eurocode‐4 is permitted for slabs with ductile longitudinal shear behavior. Ductility, as explained in the clause 9.7.3(3), depends on the fact that the failure load exceeds the load corresponding to the slip (0.1 mm) in more than 10%; then the slab is classified as ductile. Apparently, the aim of this criterion is to ensure the slab can undergo further deflections until the whole yielding of the cross‐section is achieved, as required hypothesis by the PCM. The aim of this paper is to study the stresses developed at the cross‐section of composite slabs with open and dovetail profile, in order to evaluate the yielding degree of the cross‐section. Based on the results of this study, it is recommended to exclude open profiles from partial connection method (PCM), even if the slab is classified as ductile through Eurocode definition. Although all studied specimens are classified as ductile according to Eurocode‐4 clause 9.7.3(3), the observed stress distribution at cross‐section proves that yielding occurs in the slab with re‐entrant profile only, whereas slabs with open‐rib profiles remain almost elastic until their brittle failure.
Parametric study on non‐ductile demountable shear connectors
Authors: Odenbreit Christoph , Kozma András
Published: September 2019

The basic principle of the circular economy is to reduce or totally eliminate waste and carbon dioxide production with the help of a multiple, efficient usage of resources. The application of reusable structural elements plays an important role and can contribute essentially to a low‐carbon future. Within the European research project REDUCE (Grant Agreement number: 710040), composite beams and steel‐based flooring systems, which are demountable and reusable, have been developed and investigated. The experimental investigations showed that the structural behaviour of the newly developed shear connectors differs from the behaviour of the traditionally applied welded studs. Some behave in a non‐ductile way.

In order to assess, how far the regulations of EN1994‐1‐1 for shear connections can still be applied, parametric studies have been conducted. The respective numerical models were developed with the use of the commercially available finite element software ABAQUS® and were validated against the experimental observations. The effects of the lack of ductility of the shear connectors on the structural behaviour of the entire composite beam was examined with different types of shear connectors, shear connector layouts and material grades.

This contribution presents the underlying laboratory tests as well as the results of the supplementing numerical parameter studies. The outcome provides valuable information for future design guidance concerning the use of demountable shear connectors in composite beams.
Resistance of the beam‐to‐column component “column web panel in shear” – numerical and analytical investigations
Authors: Corman Adrien , Jaspart Jean‐Pierre , Demonceau Jean‐François
Published: September 2019

The « component method » is nowadays recognised by the European codes as the reference method to design and characterise steel and steel‐concrete composite joints. This method, which may be seen as a macroscopic application of the finite element method, consists in dividing the joint into a series of zones through which the forces are transferred, those zones being named “components”. Among them, the so‐called “column web panel in shear”, when activated and appropriately designed, can play a key role by providing a reserve of ductility to the joint. In Eurocode 3, Part 1‐8, a simple analytical model is proposed to predict the behaviour of this component in terms of stiffness and resistance. However, some recent researches have demonstrated that, in many cases, the so‐predicted resistance tends to be significantly overestimated, which turns out to be rather concerning from a safety point of view. In this context, the present paper will reflect first results of investigations conducted at Liège University on that problematic. In particular, beam‐to‐column welded joints have been studied in order to: (i) highlight the above‐mentioned problem through comparisons between existing experimental results and Eurocode 3 predictions, (ii) develop a sophisticated finite element model using the software Abaqus©, (iii) validate this FEM model using existing experimental results and (iv) develop an extensive parametric study in order to highlight the key parameters governing the resistance capacity of the studied component. Based on the conducted investigations, the final goal consists in providing a new analytical formulation which is able to predict more accurately the resistance of the column web panel in shear.
Mode‐based Beam and Connection Analysis of Frames
Authors: Hansen Anders Bau , Jönsson Jeppe
Published: September 2019

Major steel structures are commonly constructed as frames or trusses. The connections between its beams and columns have a crucial influence on the global behaviour. However, a detailed assessment of the joints is often neglected with rough simplifications, which may lead to poor results. On the other hand, if performing a detailed assessment it is a time‐consuming task requiring special expertise. Consequently, the idea stressed in this paper is a novel approach on how to analyse thin‐walled steel frames including a detailed assessment of both the joint and beam mechanics.

The approach is based on a transformation from standard degrees of freedom into a displacement‐based mode formulation. Furthermore, this transformation reduces the total number of degrees of freedom to be computed for advanced joints and beam elements. All this is achieved by adopting an advanced beam element formulation as well as introducing the idea of a ‘joint element’ formulated by finite shell elements. One of the main advantages of this idea is a general formulation of the joint, which makes it valid for many beam‐to‐column configurations. Furthermore, beam members can either be closed or open sections due to the adopted advanced generalised beam theory. Furthermore, a detailed analysis of the joint element itself is also achieved by this approach. Finally, an increased efficiency is achieved due to reduction of the total amount of degrees of freedom of the advanced model, and a new in‐depth knowledge of the joint behaviour is gained from this approach as well, due to the displacement‐based mode formulation.
Torsional Capacity of Slip Joints with Polygonal Hollow Sections
Authors: Bräutigam Katharina , Knoedel Peter , Ummenhofer Thomas
Published: September 2019

Polygonal steel sections are widely used for lighting towers and are more and more adopted for transmission line towers. They convince with an inconspicuous appearance compared to steel lattice towers. Therefore, instead of flange connections “invisible” joints are preferred, such as slip joints. The European design rules for overhead electrical lines (1) cover the use of these joints very generally by a constant ratio of the overlapping length L and the section's diameter D. It is neither distinguished between load conditions nor between cross‐sectional shapes. The ratio value L/D = 1.5 is based on bending tests without regard to torsional moments. In the design of transmission line pylons, torsional loading occurs in the load case of a single‐side loss of a transmission line. Thus, there is a need to improve the knowledge on the load bearing effect of a slip joint connection within this special load case.

In this paper the torsional capacity of slip joints is investigated to identify the capability of polygonal cross sections to carry this additional load, particularly in comparison with circular hollow sections. On the basis of numerical and analytical analysis, an adaption for the design of the slip joints is proposed.
Study of the Rigidity of a Concentrically Braced Frame Connection Using End Plates
Authors: PARENT Serge , ROY Nathalie , GAUTHIER David
Published: September 2019

In steel buildings, concentric braced frames are often used as lateral force resisting systems. In this type of systems, the connection between the beam‐gusset connection and the column may consist of end plates or double‐angle sections. Connection design with double angles is simple and well documented, but it requires the handling of many steel angles. On the other hand, single continuous end plate connection design is based on the use of a single plate, easily produced in the shop leading to a lesser risk of manufacturing errors. The purpose of this research project is to characterize the behaviour and stiffness of three types of connections used in a concentrically loaded braced frame: a standard double angle connection (DAC), a continuous end plate connection only welded to the web of the beam (EPW), and a continuous end plate connection welded all around to perimeter of the beam (EPF). The results of nine full scale samples are presented. These results use a HSS127×127x4.8 brace connected to a W310×45 or W460×52 beam. The beam‐gusset assembly connects to the web or to the flange of a W250×73 column. The connections are subjected to a progressive cyclic loading until failure in a full‐scale assembly in the laboratory. The preliminary results make it possible to characterize and compare the three types of connections attached to the web/flange of the column. In conclusion, the three connections have different stiffness factors. The EPF connection is the most rigid, followed by the DAC connection and finally the EPW connection.
Validation of simple superelement model of warping transfer in moment connections of portal frames
Authors: Vaszilievits‐Sömjén Bálint , Szalai József , Rad Majid Mohavedi
Published: September 2019

A simple beam element‐based modelling technique has been developed to allow the analytic definition of a stiffness matrix to describe the behavior of corner region between two doubly symmetric thin‐walled I beams connected through moment connection. The stiffness matrix describes the relation between „out‐of‐plane” type deformations of connected beam ends and related internal forces including shear force parallel to the flanges, torsion, weak axis bending and warping of flanges. The model allows to simulate the warping and distortion of the beams within the connection region. The resulting stiffness matrix is compatible with the thin walled beam theory with 7DOF beam elements. A parametric study has been performed to validate the model with shell element‐based simulation, using Abaqus and ConSteel software, concentrating on the direct out‐of‐plane behavior of portal frames. In the validation process first and second order analysis results and results of linear buckling analysis have been analyzed. The correctness of the shell element‐based simulation has been proved by full‐scale laboratory test. The test result has shown excellent agreement with the numerical simulation and with the proposed model.
Stiffness of steel‐to‐timber connection under cyclic loading
Authors: Gocál Jozef , Odrobiňák Jaroslav
Published: September 2019

The paper deals with experimental and theoretical analysis of a problematic structural detail occurring in contemporary combined timber‐steel road and pedestrian bridges – the connection of a steel crossbeam to a main timber girder. This joint is usually designed as a bolted connection and it is often required to behave as a rigid one in the plane perpendicular to the timber element in order to ensure the main timber girders against lateral and torsional buckling. The required stiffness of the joint is reached by its appropriate configuration, however, it is significantly affected by a dynamic character of loading, which causes gradual deterioration of the joint components finally resulting in possible decrease of the joint stiffness. In order to investigate this problematic detail more exactly, laboratory tests on specially prepared specimens were performed. The specimens were subjected to static and cyclic loading, as well. The joint stiffness is determined by means of component method that is rather well processed in the field of joints of steel structures. The input parameters for application of this method for combined steel‐to‐timber connection are specified on the basis of tests results. The aim of the research is to define how cyclic loading affects the stiffness of the investigated joint and to give some recommendations for practical modelling of this joint.
Connections in mixed structures with steel columns with threaded rods and normal strength concrete beams: Numerical analysis with incremental load
Authors: Gutiérrez Oscar , Bermúdez Carlos
Published: September 2019

This research proposes to evaluate the suitability of a new type of hybrid or mixed joint for framed structures that are composed of H shape vertical elements made of structural steel and reinforced concrete with rectangular section horizontal elements. Researchers of Spanish origin have made the first experimental campaigns of these mixed joints using stud connectors welded to the flanges of the structural steel, which implies a follow‐up to the welding procedure. These researchers have concluded that these joints offer good resistance to static loading and that the contribution of strength by adherence and friction between the steel column and the concrete beam is important. In the framework of this research, relevant laboratory tests (cyclic load tests) will be carried out to evaluate and characterize the behavior of the joint in the event of seismic events, for areas of high seismic hazard, in addition, the modeling of the joint using the Finite Elements Method and the theory of mixtures of composite materials that anticipates their mechanism of failure. The innovative components of this research are the implementation of threaded rods, which will cross the flanges of the steel column and the evaluation of this joint under cyclic loading. This article will present and analyze the results of the first stage of this investigation, in which two partial models of the mixed joint with static load were made, which was applied at the end of each of the beams until producing its mechanism of failure. The results show an early failure mechanism on the outside contact surface between the two materials and deformations in the column outside the area embedded by the concrete.
Time‐optimized assembly of bridge bearings: Force‐fit gap compensation of steel‐connections with metal‐polymers
Authors: Kunde Carsten , Di Gregorio Luigi
Published: September 2019

The time factor plays one of the major roles in today's steel building. Particularly in the field of traffic infrastructure operational interruptions caused by assembly or repair work cause financial and economic trouble.

New solutions for repair and assembly aimed at reducing costs and time are therefore in great demand, whether in the form of new materials or innovative application methods. A novel gap compensation material based on high strength polymers developed in Germany reduces time and cost in steel construction and assembly. The material works as a “liquid shim plate” and joins steel elements with a 100% force and form fit connection. The product can be applied in situ without machining or disassembly flexibility and safety for construction and maintenance works.

The “liquid shim material” DIAMANT MM1018 is the first of its kind to be awarded the general building authority approval (abZ) by the German Institute of Building Technology (DIBt) [1] and approved by German railways (Deutsche Bahn) through intern regulation.
Economic viability of demountable steel‐concrete composite beams
Authors: Gîrbacea Ioan Andrei , Nijgh Martin Paul , Veljkovic Milan
Published: September 2019

Composite beams are commonly used in current design practice due to their efficient material use and competitive execution. The shear connection is mainly achieved by means of headed studs welded on the top flange. However, the welded connectors obstruct the possibility of a non‐destructive disassembly required to reuse the steel beams and concrete slabs. Raised concern regarding sustainability aspects drive the construction sector to introduce a shear connector which enables the demountability of the flooring. Composite action can be enabled by a bolted connection consisting of an embedded bolt and coupler connected by an external injection bolt through the top flange of the steel beam. This paper aims to assess the initial investment costs and economic viability of two demountable steel‐concrete composite beam solutions. The investigated systems comprise of two different concrete flanges: a prefabricated solid deck and an in‐situ casted profiled sheeting slab. The cost inputs of the analysis were defined by industry experts based on assumed labour and material requirements. The unit price of the novel connector is significantly higher (approx. 15 times) compared to the regular headed welded stud. This justifies the need to optimize the connector arrangement in order to keep the cost per square meter as low as possible. Non‐uniform connector arrangements can be used to reduce construction time and costs with minor decrease in beam stiffness. A tool was developed to generate a batch of 13500 composite beam designs which were later analysed in terms of costs.
No standard lock gates for the new sea lock in IJmuiden, the largest lock in the world
Authors: van Lierop Pieter
Published: September 2019

In the Dutch city of IJmuiden, a new sea lock is currently under construction. With a lock chamber of 500 m long and 70 m wide, it will be the largest lock in the world. The latest generation of seagoing vessels will be able to access the harbour of Amsterdam using this lock. At the same time, at an altitude of 8.85 meters above sea level, the Netherlands are protected from the rising sea water for the next two centuries. The lock must be constructed in between of the existing operational locks. Because of this lack of space, the water levelling system is incorporate in the rolling gates. The required performance of the gates as well as the drive mechanism, in terms of reliability, availability, maintainability, safety and robustness), was highly governing during the design process, and resulted in a final design that cannot be described as standard.
A Repairable Connection for Earthquake‐Resisting Moment Frames
Authors: Richards Paul W.
Published: September 2019

Most steel moment frames are designed so that the beams act as structural fuses during earthquake loading. This approach, while effective for life safety, has poor resilience because it is difficult to replace beams in a building. A repairable steel moment frame connection has been developed that may be attractive to engineers and constructors. The connection has a fuse plate bolted to the beam bottom flange which experiences shear yielding during severe earthquakes, protecting both the column and the beam. After an earthquake, the fuse plates can be removed and replaced to unlock residual frame deformations and prepare the building for another event.

Full‐scale experiments were conducted to validate the performance of this repairable connection. Two tests were performed with a W690×125 beam and a W530×196 column. The tests demonstrated rotation capacities of at least 0.05 rad, which exceeded AISC requirements for special moment frames. The fuse plate was effective in preventing beam damage in each test, and the second test demonstrated that the connection could be repaired by replacing the fuse plate.
Splice Connection Details for Eccentrically Braced Frame Replaceable Links
Authors: Bozkurt Mehmet Bakır , Topkaya Cem
Published: September 2019

Eccentrically braced frames (EBFs) can be used as a lateral load resisting system in seismic prone regions. A typical EBF consists of links, beams, columns and braces. Links are the fuse members providing energy dissipation during an earthquake. After a seismic event, damaged links need to be replaced with the new ones to recover initial stiffness and ductility of the structure. A comprehensive experimental research program has been undertaken to develop new replaceable link details. One of the proposed details is based on splicing the beam outside of the link and braces. In this type of a replaceable link, both the bearing type and slip critical type connections can be employed with different levels of bolt pretension. Four nearly full scale EBFs with replaceable links were tested to study the effect of the type of connection and gap size adopted in splice connections. The results indicate that both the bearing and slip critical type of connections can be employed for the splice connections if the bolts are fully pre‐tensioned and frictional faying surfaces are provided.
Seismic Response of Steel Structures with Properly Detailed Tension‐Only Steel Braces
Authors: Flogeras Antonios K. , Papagiannopoulos George A. , Karabalis Dimitris L.
Published: September 2019

This paper summarizes the results from non‐linear time‐history seismic analyses of tension‐only concentrically braced 3‐D steel structures. Such braces can be produced by a cheap and easy to fabricate detailing process which allows the brace to slide when in compression and to develop a resisting force when in tension. A comparison between steel structures designed with the proposed tension‐only braces and with buckling‐restrained braces is performed on the basis of commonly used seismic response and demand indices. It is shown that tension‐only and buckling restrained braced structures may exhibit similar behaviour. Nevertheless, column overstress in compression is larger for the tension‐only braced structures. Preliminary conclusions regarding the use of the proposed tension‐only braces as a seismic force‐resisting system for steel structures are drawn.
Seismic Response of Steel Structures Equipped with the Seesaw System
Authors: Katsimpini Panagiota S. , Papagiannopoulos George A. , Karabalis Dimitris L.
Published: September 2019

This work provides seismic response results from non‐linear seismic analyses of low‐rise 3‐D steel structures equipped with the seesaw system. In particular, seismic response results involving height wise distributions for peak interstorey drift ratios (IDR) and peak residual interstorey drift ratios (RIDR) as well as plastic hinge formations are obtained for 2‐ and 8‐storey fixed‐base steel structures. Additionally, soil‐structure interaction is considered for these steel structures and its effect in the aforementioned seismic response results is discussed. It is concluded that the seesaw system constitutes an attractive solution for low‐rise 3‐D steel structures as buckling problems associated with common steel braces are eliminated and their damping capacity increases considerably.
Calibration of welding simulation parameters of fillet welding joints used in an orthotropic steel deck
Authors: Spyridoni Kallia , Xin Haohui , Hermans Marcel , Veljkovic Milan
Published: September 2019

A common problem of orthotropic steel decks is fatigue failure under cyclic loading. The fillet welded connection between the deck and longitudinal stiffeners is a position where cracks are generally found. Residual stresses induced by welding influence fatigue crack initiation and propagation. An effective way of predicting the stress distribution in complicated 3D welded joints is via three‐dimensional subsequent thermo‐mechanical finite element analyses. The methodology of numerical modelling of the welding procedure in order to predict the induced residual stresses is presented in the paper. Predicted results are verified by temperature and distortion measurements derived during a small‐scale welding experiment. In the case of the thermal analysis, a double ellipsoid heat source model is used to simulate the heat input. Convection and radiation heat loss coefficients used in FEA are calibrated by the experimental results. The validated numerical procedure is then applied to a typical orthotropic steel deck joint to predict the residual stress distribution.
Influence of material on inelastic behaviour and local buckling of SHS Members under cyclic loading
Authors: Nagai Tomoaki , Ochi Kenshi
Published: September 2019

Previous studies on the influence of different manufacturing process on mechanical properties of cold‐formed, hot‐rolled and cold‐formed with subsequent heat treatment square hollow sections have proposed the FEM analysis with the Chaboche model for cyclic behaviour of Square Hollow Sections. Previous test and numerical results showing the ultimate behaviours with local buckling and hardening/softening under cyclic bending can be simulated with accuracy. In order to investigate the relations of fracture and maximum bending stress at the corner of the sections, these previous studies used the model of the section with 45 degrees around the member axis. This paper presents the results of the FE analysis with standard axis of the Square Hollow Sections. FE analyses were carried out to examine the effects of the material properties and diameter to thickness ratio on the load‐deformation curves. Based on the cyclic loading protocol as experimental procedures, numerical results are compared with loading history each other. The section with high yield ratio steel shows the higher bending strength than low at lower magnitude loading cycles. The behaviours at the maximum magnitude cycles get closer for all material sections. The required rotation capacity for classification with seismic design is compared with the results of FEA for the SHS members.
New Eurocode for Towers, Masts and Chimneys
Authors: Nielsen Mogens G.
Published: September 2019

The Eurocodes are under revision these years as part of the maintenance of the codes for design of structures in Europe under the responsibility of CEN/TC 250. The primary purpose of the maintenance of the Eurocodes is to include the newest knowledge within the field, secondary also to reduce the number of Nationally Determined Parameters (NDPs) to make the Eurocodes more harmonised. Furthermore, will the changes reflect practical experiences gained using the existing codes. However, it is CEN/TC 250 policy to minimise corrigenda to stabilize the Eurocodes.

Eurocodes for Steel Structures consist of several parts, among these EN 1993‐3‐1 ‘Towers and Masts” (1) and EN 1993‐3‐2 “Chimneys” (2). These two parts are going to be merged into EN 1993‐3 ‘Towers, Masts and Chimneys’. A Project Team SC3‐T11 consisting of 5 members from 5 countries is preparing the new draft EN 1993‐3.

However, some parts of these specific standards are related to safety; these will be moved from the old parts to the new EN 1990 ‘Basis of structural Design’. Other parts, related to the wind load will be moved to the updated version of EN 1991‐1‐4 ‘Actions on Structures, General Actions, Wind Actions’.

The Author is the chairman of the Project Team preparing the new draft of the Eurocodes for Towers, Masts and Chimneys (EN 1993‐3). He has been engaged with Ramboll for more than 30 years, and has been involved in design of towers and masts over most of Europe.

This paper will give an overview over the changes related to towers & masts and chimneys and describes how the number of NPDs will be minimized.
A calibrated verification model for fatigue assessment of road bridges
Authors: Leander John , Skoglund Oskar
Published: September 2019

The format suggested in the Eurocode for fatigue verification of road bridges is under scrutiny in this paper. The model is easy to use in practice, which is important for design purposes, but its accuracy has been questioned. For this reason, a reliability‐based evaluation of the safety level has been performed and is briefly recapitulated in this paper. It shows a large scatter in reliability index ranging from unacceptably low to overly conservative. A calibration of the existing model has been performed showing a more consistent reliability level. Results from comparisons of the existing and calibrated models are shown for real bridges considering the influence on design stress ranges. The results show that the Eurocode model is conservative for short span bridges subjected to low traffic volume. For other cases, the Eurocode model is non‐conservative.
Biaxial compression in class 4 orthotropic steel panels using Eurocode methods
Authors: Gren Simon Mathias , Hansen John Elnegaard , Kærn Jens Christian
Published: September 2019

When designing class 4 steel sections in accordance with EN1993‐1‐5, two different methods are proposed; The Effective Section Method (ESM) and the Reduced Stress Method (RSM). The ESM is generally known for leading to results closest to the post‐buckling capacity, with the RSM considered more conservative. The RSM is much more general though, and a combination formula is present for combining longitudinal stresses, transverse stresses and shear stresses, whereas a suitable combination formula is not available for the ESM.

In connection with the steel design of the orthotropic composite deck on the Queensferry Crossing, an investigation into the suitability of the ESM was made. This, as it was believed that the use of this method would lead to the most cost‐efficient design. The Queensferry Crossing (1) has stay cable planes positioned near the middle of the deck, leading to a transverse continuous compressive stress in the bottom steel plate. As EN1993‐1‐5 (2) does not provide a method for combining longitudinal stresses with continuous transverse stresses when using the ESM, a need for a suitable combination formula was evident.

In this paper a combination formula for combining longitudinal stresses, uniform transverse stresses and shear stresses in an orthotropic steel panel using the ESM is proposed. A typical panel from the Queensferry Crossing is used, when results from the ESM and RSM are compared for various stress distributions, with results from a fully non‐linear FE shell model. A good relation between the ESM and the fully non‐linear FE shell model is found, when the combination formula is used, and it is shown that significant savings to the steel quantities can be made by utilizing this combination formula.
Steel structures for the new “Seilbahn Zugspitze” – on top of Germany! Topic: Fabrication & Construction
Authors: Walder Markus
Published: September 2019

Stahlbau Pichler with Headquarter and Production in Bolzano (I) from 17 December 2015 until 21 December 2017 has been responsible for fabrication, construction and installation of the new upper and lower station of the new areal tramway “Seilbahn Zugspitze” in Garmisch – Germany. In 2 years more than 1.100 tons of steel structures have been put on “top of Germany” optimizing logistics, installation and also fabrication. One of the biggest challenge of the project was the altitude of 3.000m above sea level of the construction site with no road access, so that all material had to be delivered to the site with a special material ropeway. Another challenge was that the construction site was always open to the public, because the client did not want to close the cableway for guests and last but not least temperature and wind had a big influence on the whole construction process.
TWO‐STAGE‐MODEL FOR THE PROGNOSIS OF FATIGUE LIFE: APPLICATION TO BUTT WELDS
Authors: Röscher Stefanie , Knobloch Markus
Published: September 2019

This paper presents a Two‐Stage‐Model to determine the fatigue life. The model follows the distinction between the crack initiation and the crack propagation according to the phenomenological background. The first stage uses the local notch‐strain concept to predict the number of cycles for crack initiation Ni considering the cyclic material behaviour as well as the load‐time history. The second stage calculates the crack propagation based on a linear‐elastic fracture mechanics‐approach. Using the X‐FEM‐Method in combination with cyclic loading, an arbitrary, solution‐dependent crack path was achieved to determine the number of cycles for propagation Np. The Two‐Stage‐Model was applied to butt welds to determine the total fatigue life Nf. The study investigated the ability of the model to consider the influence of the weld geometry. The results are presented by means of SN‐Curves for initiation life, propagation life and total fatigue life and compared to experimental results.
Performance of large‐scale fatigue tests
Authors: Dürr André , Bucak Ömer , Roth Jakob
Published: September 2019

The fatigue strength for the design of steel structures is generally determined experimentally by fatigue tests. Because the results of fatigue tests usually have a large scatterband, there is a larger number of tests for every construction detail required. For cost reasons, the fatigue tests are therefore performed generally with small‐scale specimens.

In recent years there were performed several large‐scale fatigue tests for the examination of the size‐effect on the fatigue strength of welded steel structures at the University of Applied Sciences Munich. Especially the resonance testing system using attached external vibrators is an appropriate and cost‐effective method for performing fatigue tests with large‐scale specimens. With this method large‐scale fatigue tests with specimen dimensions comparable to real structures up to 18 m girder lengths and weights up to overall 20 tons were carried out in different research programs.

Within this paper the test set‐up of these large‐scale fatigue tests is shown. The paper summarizes the obtained results for the typical construction detail of the transverse stiffener welded on plates and rolled sections (HISTAR‐profiles) with flange thicknesses up to 100 mm and for the construction detail of welded K‐joints made of hollow section profiles with wall‐thickness up to 60 mm.
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

Ultra‐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

Previously 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

A 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

Fatigue 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

The 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

Long‐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

The 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

Central 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

Although 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.