bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental and numerical investigation of reduced web section connections in fire
Authors: Oday Yabari , Mika Alanen , Mikko Malaska , Katherine A. Cashell
Published: September 2023

This paper presents the details and analysis of a fire test conducted on a reduced web section (RWS) connection for steel framed construction. The test was completed in the fire laboratory at Tampere University in order to assess how these connections, usually selected and designed for their seismic performance, behave under fire conditions. RWS connections were first devised for fixed joints in steel framed buildings, with a view to moving the plastic hinge away from the column face during an extreme event such as an earthquake, thus improving the ductility of the structure. Until now, there was very little known of their behaviour under fire conditions. Accordingly, the current paper provides a detailed description and analysis of the fire test on a RWS connection, during which the arrangement lasted for around 16 minutes of standard fire exposure. It also describes the development of a numerical model, which is validated against the test data. The purpose of the model is to enable a more thorough examination of the various parameters and variables that may exist in a real structure, subjected to a real fire.
Damage evaluation of steel frame subjected to impact load at midspan
Authors: Chen Ying , Chen Wensu , Hao Hong , Nie Zhenhua
Published: September 2023

The lower floors of the multi‐storey structure can be impacted by the debris from the upper floor caused by gas and bomb explosion, which may induce damage or failure of the impacted substructure and lead to progressive collapse of large‐scale structure. The behavior of the frame with a steel beam and two adjacent beam‐column joints was numerically analyzed when the beam was impacted at midspan by various combinations of impact mass and velocity. The failure mode of the joints, the impact load and midspan displacement were analyzed. It shows that the beam‐column joint fails prior to the beam under all impact loading scenarios. The residual bearing capacity of the frame was also studied by statically pushing‐down the substructure after impact loading. A damage index was proposed using the residual capacity of the frame after impact loading divided by the static capacity of the joint without impact loading, and four damage levels, i.e., the minor damage, medium damage, severe damage, and collapse, were defined by the damage index. The boundaries of different damage levels of the frame under various impact loads were fitted, and it can be used to evaluate the damage level of the frame subjected to possible impact loads.
Influence of loading frequency on ULCF life of structural steel under variable surface roughness
Authors: Saleem Aleena , Tamura Hiroshi , Katsuchi Hiroshi
Published: September 2023

This paper investigates the effects of a wide range of loading frequencies ranging from 0.005 to 5 Hz and blasting induced surface roughness ranging from 20 to 100 μm on the ultra‐low cycle fatigue (ULCF) life of structural steel. The combined effect of these parameters on ULCF life has not been investigated so far. To this aim, comprehensive ULCF tests were performed on steel specimens under a constant displacement‐controlled environment until the failure occurred. The experimental results manifest that the surface roughness and loading frequency are the governing parameters affecting the ULCF life. The test material exhibits cyclic softening behavior under all loading conditions. An increase in loading frequency from 0.005 to 5 Hz causes a significant increase of 33% and 27% in ULCF life for 20 and 100 μm rough specimens, respectively. However, the effect of frequency on ULCF life becomes less significant at higher values of surface roughness. Moreover, an increase in surface roughness from 20 to 100 μm causes a significant reduction of about 45% and 47% in ULCF life at the loading frequencies of 0.005 and 5Hz, respectively. Furthermore, a correlation between fatigue life and loading frequency as a function of surface roughness is derived by the power law relationship.
LOCALISED FIRE ASSESSMENT OF A STEEL STRUCTURAL SOLUTION IN A PILOT BUILDING
Authors: Gamba Antonio
Published: September 2023

Many tragic fires in the past decades have highlighted the importance of fire safety engineering and its meaningful application in the engineering field. With a constant and significant growth of the research the classical approach based on prescriptive time‐temperature curve, where the gas temperature is assumed to be constant within the entire compartment and always increasing on time has been challenged by a performance‐based one. Performance‐based approach is aiming to represent the fire accounting for more physics than the prescriptive approach, considering ignition, fire growth burning and cooling phase. Nowadays practitioners facing the design stage of a project have to face the choice between designing with prescriptive or performance‐based approach. In this work a comparison between design using performance based and a prescriptive approach will be provided. In particular, the building is under development in the framework of a demonstration RFCS (Research Found for Coal and Steel) project called DREAMERS, founded by the European Commission. The chosen structure for this example is an 800 m2 steel building, which will be built in the Campus of the University of Salerno (Italy). The main peculiarity of the building is the implementation of all the most advanced technologies for the construction of a resilient structure in terms of seismic, robustness and fire safety. The building is designed in steel and steel composite solutions, following a holistic design approach and foreseeing a life time monitoring of its behavior. The flooring system is made of Asymmetric Floor Beams (AFB) and Cofradal® 260, whereas vertical elements are hot rolled HEB sections. The work here presented is showing some of the main challenges related to the fire design as well as application of next generation localised fire models.
ON THE RELIABILITY OF A NUMERICAL TRAVELLING FIRE MODEL
Authors: Gamba Antonio
Published: September 2023

The ongoing urbanization of our society is leading to the situation that many people live, work and gather in buildings of larger size. Open space office buildings are becoming more common, airport terminals are continuously increased in size and new larger railway stations are being built. When it comes to compartments with larger floor areas, the fire may be localized, which means that the fire does not extend on the whole floor. Yet, even when the fire load is distributed, such as in open space office buildings, the area where combustion is raging moves during the fire leading to so‐called “travelling fires”. The classical view of compartment fire with the strong assumption of uniform temperature in the compartment has been challenged, several travelling fire models have been proposed to address the phenomenon. Validation of these models is still scarce. This work is about the assessment of reliability and accuracy of a numerical travelling fire model implemented in a software called GoZone. The assessment is done mainly by comparison of relevant output in a fire compartment such as fire growth rate as well as by comparison of gas temperature, rate of heat released and resulting steel temperature. In the framework of this paper, only a part of the entire assessment focused on office building is presented.
Structural analysis of rack upright frames under a pure compression load by means of a nonlinear Generalized Beam Theory analysis
Authors: Bonada Jordi , Casafont Miquel , Bové Oriol , López Ignasi
Published: September 2023

Rack upright frames of conventional pallet racking systems are obtained by the assembly of uprights and braces or diagonals. Rack uprights are commonly mono‐symmetric open thin‐walled members with regular perforations along their length. These perforations are used to enable the connection with braces and beams by means of bolts or hooks. The structural behaviour of a rack upright frame under a pure compression load, in which the buckling phenomenon has a relevant influence, depends on several geometrical parameters, such as the column cross‐sectional dimensions, perforations characteristics, frame length, distance between braces, etc. Therefore, these particular issues should be considered to perform a proper structural analysis.

In this paper, the structural behaviour of a pallet rack frame under a pure compression load is analysed by means of eigenbuckling and geometrically nonlinear Generalized Beam Theory (GBT) analyses. The influence of GBT deformation modes involved in the analysis is discussed. Moreover, different approaches to reproduce the connection between uprights and braces are presented and discussed. Finally, GBT results are compared with beam, shell finite element analysis and experimental values.
Seismic behaviour of dissipative beam‐to‐column steel and steel‐concrete composite joints
Authors: Skarmoutsos Georgios , Kuhlmann Ulrike
Published: September 2023

The present paper deals with the seismic behaviour of bolted steel and steel‐concrete composite partial‐strength beam‐to‐column joints with endplate connections. In a series of experiments in total 12 two‐sided internal joint specimens were tested, of which 3 were all‐steel and 9 steel‐concrete composite. For those, 5 parameters were varied, (i) thickness of endplate tep, (ii) vertical distance of T‐stub bolt rows e4, (iii) distance of first shear stud to face of the endplate l, (iv) reinforcement ratio of concrete slab ρ and (v) number of bolt rows. The design of the specimens was performed with the help of both the component model as given in EN 1993‐1‐8 and a FEM model. The chosen parameter values were optimised to provide, for given beam and column sections, an upper and lower limit regarding moment capacity and rotational stiffness, for sufficient energy dissipation and ductility. The experimental results show that the stiffness of the concrete slab leads to a significantly different response of composite compared to all‐steel joints, especially regarding rotational stiffness and capacity of the joint as well as flexural stiffness of the (composite) beams. The composite joints present an overall better seismic behaviour compared to all‐steel ones.
Preventing failure propagation in steel truss bridges
Authors: Sánchez‐Rodríguez Ana , López Santiago , Makoond Nirvan , Buitrago Manuel , Riveiro Belén , Adam José M.
Published: September 2023

Metal and steel truss bridges are essential for transportation networks worldwide but are vulnerable to collapse due to deterioration and increasing traffic loads, particularly for ageing structures. Several bridge collapses, such as the Seongsu bridge (South Korea, 1994), I‐35 bridge (USA, 2007), and Chauras bridge (India, 2012), have highlighted the need to develop accurate robustness assessment strategies and efficient mitigation of collapse risks. This paper summarizes results of experimental and computational studies for a steel riveted bridge with a truss‐type structure. The experimental component presented involves unique tests to be performed on a 21 m full‐scale bridge span subjected to the failure of different elements under laboratory conditions. The paper then presents a first approach to explore different damage and failure scenarios for steel truss bridges, which will assist in defining data collection strategies for optimised monitoring and developing data analysis methods for real‐time diagnosis of ageing bridges. With this, the paper contributes to avoiding progressive collapses and presents a framework, developed as part of an ongoing project, to identify vulnerable zones for prioritising monitoring systems that anticipate failure propagation and prevent collapse. The framework is based on a systematic analysis of past bridge failures and simulations of carefully designed generic cases.
Study on Global Imperfection of Modular integrated Construction Structures for Second‐order Analysis
Authors: Ding Yue‐Yang , Liu Si‐Wei , Liu Yao‐Peng , Chen Wen‐Feng , Chan Siu‐Lai
Published: September 2023

The global imperfection significantly influences the stability design of the Modular integrated Construction (MiC) buildings. Currently, the initial global imperfection shapes recommended for MiC structures are formulated based on steel frames whose members are continuously connected. In practice, the columns and beams in MiC structures are composed of the members of adjacent module units, which are discontinuously connected through the special joints. Ignorance of such discontinuous features in MiC structures leads to an inappropriate estimation of the structural resistance. This paper introduces a new initial imperfection shape for MiC structures considering out‐of‐verticality of module columns and eccentricity between modules, capturing the discontinuous feature. Random initial imperfection shapes were generated using Monte‐Carlo simulation based on tolerances in regulations. The proposed imperfection shape is adopted in the analysis of a typical MiC structure and the result is compared with results from existing global imperfections in design codes. This research provides a practical global imperfection for the second‐order analysis and design of steel MiC structures. Recommendation for basic value of the proposed imperfection shape is also provided.
Dynamic Increase Factors for progressive collapse anaylsis of steel structures accounting for column buckling
Authors: Possidente Luca , Freddi Fabio , Tondini Nicola
Published: September 2023

Man‐made hazards, such as fire, explosions, or impacts, may induce the progressive collapse of structures, in which the localised failure spreads from the single affected structural component to other parts of the structure. A typical approach to model progressive collapse consists in performing static column removal analyses considering a Dynamic Increase Factor (DIF), whose determination becomes paramount to account for the dynamic effects related to a sudden column loss scenario. Current recommendations on the definition of such factor mainly consider a beam‐type collapse in non‐linear analyses, though different mechanisms, e.g., column buckling, may govern progressive collapse events. This paper presents the determination of the DIFs through a numerical procedure for five steel structures with an increasing number of storeys. Both global and local imperfections are modeled to account for the geometric non‐linearities of the structure and column buckling. DIF values are obtained considering two different Engineering Demand Parameters (EDPs), suited for describing beam‐type and column‐type mechanisms respectively. The evaluated DIFs are compared with the values recommended in the current UFC design prescriptions for progressive collapse, and considerations on the choice of the appropriate DIF values are provided.
Seismic Performance of Multistory Chevron‐braced Steel Structures with Yielding Beams
Authors: Orgev Ahmet Alperen , Selamet Serdar , Vatansever Cuneyt
Published: September 2023

Lateral loads are resisted by braces in concentrically braced frames. Therefore, braces meet the demand for the load combination based on the seismic provisions. The rest of the system including the connections are determined according to the capacity‐based design, where the brace members yield under tension and buckle under compression. Chevron or inverted V‐braced frames are generally preferred because they allow large openings for doors and windows. However, the seismic‐design requirements in current building codes lead to deep, heavy chevron beams to resist the unbalanced load at beam members due to pre‐ and post‐buckling compressive strength deterioration and full tensile yielding of the braces. This results in uneconomical design. Recent large‐scale experiments of chevron‐braced frames have demonstrated that limited beam yielding is not detrimental to chevron‐braced frame behavior and on the contrary, it utilizes a second yielding mechanism and thereby increases the story drift capacity at which the braces fracture. Also, they propose a new design method for chevron braced frame with yielded beam. This paper expands the previous findings by investigating the seismic performance of 9‐story structures which are designed according to provisions and proposed method. Structural analysis program SAP2000 is utilized for linear design by modelling the full‐scale 9‐story building. Nonlinear finite element analysis software Perform 3D is utilized for the nonlinear time history analysis in which only a single chevron braced frame is modelled. Results show that the proposed building design has larger interstory drift ratios. However, the adjusted collapse margin ratio and the collapse probability for maximum considered earthquake satisfy the required limitations. In other words, the proposed chevron frame design offers a more economical alternative with no significant tradeoff in seismic performance.
Experimental characterisation of connection behaviour for cold‐formed steel panels sheathed with calcium silicate boards
Authors: Ringas Nikolas , Huang Yuner
Published: September 2023

Construction trends aim towards the use of modular cold‐formed steel (CFS) wall panels, comprising of CFS studs and sheathing. Their capacity is influenced by different components employed, with the fastener connection between the sheathing board and the frame being the most critical. Furthermore, as repeated loading scenarios are expected to occur within the life cycle of a structure, it is important to address the uncertainty surrounding the connection behaviour under cyclic loading. A series of push‐out tests were carried out for cold‐formed steel sections sheathed with Calcium Silicate Board, using monotonic and cyclic loading protocols. The cyclic protocol employed focuses on the serviceability limit state with a repeated load‐unload step applied for 10 cycles. Two assembly arrangements, namely back‐to‐back and single stud arrangements were employed. Push‐out test results are presented and discussed herein. Recommendations for the test procedure and design of connection in sheathed cold‐formed steel shear walls are proposed.
Experimental Testing of Post‐installed Anchors for Use in Retrofitting of RC Frame with Steel Braces
Authors: Tewatia Devyani , Kumar P. C. Ashwin
Published: September 2023

The retrofitting of deficient Reinforced Concrete (RC) frames, particularly those with strength and stiffness irregularities such as Open Ground Story, has been widely researched. Steel braces are a great option for retrofitting these buildings, but the narrow section sizes of existing beams and columns pose a challenge. However, post‐installed chemical anchors can provide an efficient, cost‐effective solution for connecting such structures with steel braces, provided that they are designed properly to account for all possible failure modes. This study investigates the use of post‐installed chemical anchors to connect steel braces with narrow‐beam column subassemblies in existing low‐ to mid‐rise Open Ground Story buildings. The three experiment are considered to test the bracing conditions with elastic and yielding brace. The gusset plate is designed as per Balanced Design Procedure to obtain an economical section with controlled yielding and failure sequence. The forces on gusset plate are computed using the Uniform Force Method, which helps in designing the post‐installed anchor dimension and spacing. A comparison is drawn between the three test from which it is seen that the chemical anchors perform well in all cases and conventional brace shows expected performance.
The plastic deformation capacity of the structural system for thin‐web steel beam reinforced with stiffener plates
Authors: Nitawaki Masashi , Ishii Daigo
Published: September 2023

Japanese buildings are generally designed as moment‐resistant frames, and beam ends are required to have high bending strength and high plastic deformation capacity. With H‐shaped beams, the contribution of the web to the bending strength is small, so H‐shaped beams with thick flanges and thin webs are used to reduce the amount of steel required for construction. However, H‐shaped beams with thin webs are prone to local buckling at the ends of the beam, resulting in poor plastic deformation performance. The authors have developed a structural system of steel structures in which the ends of beams are reinforced by stiffener plates with the aim of improving the plastic deformation capacity. Especially when these structural systems are applied to a high‐rise building with large‐sized beams, the effect of reducing the amount of steel is high by reducing the thickness of the web. Reducing the amount of steel can be expected to reduce the loads on the environment and the construction cost. In this paper, the simple stiffening method is proposed with stiffeners that can improve factory manufacturability. Secondly, to confirm the plastic deformation capacity of a stiffened steel beam, a series of cyclic loading tests is carried out using 1/2 scale specimens.
Strengthening of axially compressed bars in lattice towers under load – experimental investigations
Authors: Jastrzębski Kamil , Ślęczka Lucjan
Published: September 2023

This paper presents the results of experimental research, in which hot‐rolled single steel angle members L65×65×7 were strengthened under axial compression. Strengthening was carried out by attaching an additional angle (L65×65×7 or L50×50×5) by a clamp system. The reinforced angle, the reinforcing element and the clamps were hot‐dip galvanized. The paper compares the difference between buckling behaviour and the ultimate load capacity elements strengthened under no load with the elements having the same geometry, in which the strengthening was carried out under the load. The level of force transmission from the reinforced to the reinforcing member is also recognized. The results show the influence of the size of the reinforcement element, the slenderness of the reinforced member, and the spacing of the clamps on the effectiveness of reinforcement. The effect of preload on the ultimate load capacity of the axially loaded element was found to be insignificant in the study conducted (no more than ±4.2%).
Lateral‐Torsional Buckling of welded I‐members with flame‐cut flanges: Experimental and numerical studies
Authors: Lebastard Maxime , Couchaux Maël , Bureau Alain , Hjiaj Mohammed
Published: September 2023

Eurocode 3 design rules for the lateral stability of welded I‐members are based on the assumption of hot‐rolled flanges. In practice, a large amount of welded I‐section members is made of flame cut flanges. However, residual stresses of hot‐rolled and flame‐cut flanges are quite different. The latter are more favourable with respect to out‐of‐plane buckling. The beneficial effect of flame‐cuts commonly performed at the flanges tips is then neglected in design standards. A literature review of lateraltorsional buckling tests on welded I‐members with flame‐cut flanges highlights a scarcity of results on mono‐symmetric and/or non‐uniform members. In addition, tests are generally performed on stocky cross‐sections while welded members are usually slender. Lateral‐torsional buckling tests have thus been conducted on four S355 slender welded members made of flame‐cut flanges: two uniform beams and two tapered beams. Within both couples of beams, one had a doubly symmetric cross‐section, the other one being mono‐symmetric. Experimental results highlight the impact of tapering and/or increasing the compression flange thickness whatever the beam type.

These experimental tests are then modelled with shell finite elements considering imperfections, residual stresses and material laws measured experimentally. The results are in good agreement with experimental tests. Additional finite element analyses are performed varying the residual stresses distribution. A significant impact of the flange fabrication process is confirmed, flame‐cuts increasing substantially the lateral‐torsional buckling resistance.
Structural Response of Wire Arc Additively Manufactured Steel T‐stub Connections
Authors: Guo Xi , Kyvelou Pinelopi , Ye Jun , Gardner Leroy
Published: September 2023

This paper presents an experimental investigation into the structural response of wire arc additively manufactured (WAAM) steel T‐stub connections subjected to tension. A total of fifty‐two T‐stub specimens of different printing strategies and geometric configurations were tested to failure. 3D laser scanning was employed to determine the specimen geometry, while digital image correlation was used to monitor the strain and displacement fields during testing. The structural response exhibited by the tested specimens was more complex than that reported in the literature for conventionally fabricated T‐stubs. Therefore, a new approach for the determination of the plastic resistance and failure modes of WAAM T‐stub connections was developed. Finally, the obtained results were used to evaluate the applicability of current design equations to WAAM T‐stub connections.
Sandwich Panels as Building Envelope under In‐Plane Deformation: Experimental Program and Monotonic / Cyclic Response
Authors: Bittner Lara , Vulcu Cristian , Hoffmeister Benno
Published: September 2023

Strong earthquake loads can cause significant damage to buildings, but even moderate earthquakes with higher return periods are socially relevant as they may cause both infrastructure and economic failures. In an ongoing German nationally funded research project, the behavior of facade elements in lightweight metal construction under in‐plane deformation is currently being investigated with the aim to assess the response and the energy dissipation capacity in the case of seismic events. As past research results indicate the contribution of wall and roof elements to the stiffening of buildings, with the possible consequence of increased earthquake loads due to the natural frequency change, a novel approach for increased resilience of structures with building envelopes in lightweight metal construction may be developed. On the basis of a series of experimental tests, under monotonic and cyclic loading, the effects of in‐plane deformation were studied separately from external influences such as wind and thermal loads. This paper presents: (i) a brief state of the art; (ii) a description of the research framework; (iii) the experimental program; (iv) the specimen configuration, test set‐up, loading protocol and instrumentation; (v) the response under monotonic and cyclic loading; (vi) the main conclusions, as well as the ongoing and future research activities.
Shear transfer at the steel‐concrete interface using different mechanical connectors
Authors: Bogdan Teodora , Degee Herve , Dragan Dan , Obiala Renata
Published: September 2023

The present article is dealing with an assessment of the longitudinal shear at the steel‐concrete interface using several types of mechanical connections. Experimental and numerical tests have been performed to understand better the short and long‐term effects of the influence of the newly defined connectors.

Experimental tests consisted of 12‐column push‐out tests (CoPOT). In the test campaign, four types of surface finishing have been tested: i) reference tests (0v2) without any mechanical shear connectors, (ii) angled, V‐shaped, variant of the novel flat shear connector (Av2), (iii) transversal variant of the novel flat shear connector (Bv2) and (iv) multiple ribs on the flanges having a height of 0.7mm (Cv2). Three specimens for each configuration were tested in short‐term loading. The loading procedure defined in EN1994‐1‐1:2004 Annex B was applied for all the tests. Also, one of each specimen was tested in long‐term loading to observe the effect of concrete shrinkage on the quality of bond performance. No significant differences in behavior were observed between both load sequences and the test results after shrinkage is within the short‐term tests’ margin of variation. Numerical simulations performed using FE software Abaqus®, while applying a simplified definition of the bond, supported the results of the previous investigation.
Fatigue strength assessment of riveted shear splices
Authors: Lettieri Annarosa , Latour Massimo , Rizzano Gianvittorio , Milone Aldo , D'Aniello Mario , Landolfo Raffaele
Published: September 2023

Old‐steel riveted bridges are part of the heritage asset in many countries. Assessing the remaining life and fatigue strength of their structural riveted details is crucial in managing these structures. According to JRC‐ECCS document Assessment of Existing Steel Structures: Recommendations for Estimation of Remaining Fatigue Life, fatigue class 71 is recommended to estimate the fatigue strength of riveted details. However, the predicted fatigue behaviour can lead to excessively conservative estimates. Hence the research community is still focusing on the suitability of current recommendations. This work performs a numerical study to evaluate the fatigue strength of riveted double‐shear splices. Experimental fatigue test results are collected from the literature, and some are used to develop a finite element model in ABAQUS and Fe‐Safe. The adopted modelling fatigue approach is applied to investigate the fatigue behaviour of double‐shear riveted connections with different geometrical properties. The numerical results are compared with all collected data, showing the procedure's effectiveness in predicting the fatigue strength of double‐shear riveted splices. Finally, the numerical and experimental results are compared with the recommended S‐N curves.
Truss bridge design with reclaimed steel elements by performing a stock‐constrained shape and topology optimisation
Authors: van Lookeren Campagne Fé , Sonneveld Michelle , van der Meer Frans , Noteboom Chris , Kavoura Florentia
Published: September 2023

To move up the circular economy hierarchy steel profiles should be reused instead of recycled. To efficiently utilise the limited availability of reclaimed steel elements in new structures, a different approach is required: form follows availability. This paper presents an algorithm for generating truss bridge designs using only reclaimed steel, which optimises material efficiency and avoids cut‐off waste. The algorithm does not require an initial design or a grid of possible positions like the commonly used ground structure method. Instead, it lets a truss geometry grow from start to end. The algorithm was developed using Python in Grasshopper, resulting in a user‐friendly parametric design process. By defining the width and span of a truss bridge and providing a stock of reclaimed elements, a solution cloud of locally optimal truss bridge designs in terms of capacity utilisation is generated, which comply to Eurocode provisions. An optimal design can be selected with given objectives, e.g. the lowest environmental impact. A case study showed that the developed growth method can lead to a truss with 63% less embodied carbon than conventionally designed new steel trusses and 17% less embodied carbon than optimised standard truss designs with retrofitted reclaimed steel elements.
Design optimisation of welded I‐beams made of high strength steels
Authors: Saufnay Loris , Renotte Tom , Mahieu Ludovic , Demonceau Jean‐François
Published: September 2023

Nowadays, hot rolled steel sections are used in practice. The cross‐sectional dimensions are therefore fixed and catalogued by the steel manufacturers. However, when the span of the members and/or the applied load becomes significant, such hot rolled steel sections can no longer meet the ultimate and/or service design criteria and the use of a built‐up welded I‐beam should be considered. They are typically made of three steel plates welded together to form a monolithic I‐beam. By varying the dimensions of these plates, an infinite amount of cross‐section geometries can be defined. But face to this high variability of solutions, the designers encounter difficulties in identifying the most appropriate combination of geometrical and mechanical properties for the constitutive plates.

To study and optimise these profiles, a MATLAB® routine has been developed at the University of Liege. It allows, for different load cases, to find suitable cross‐sectional dimensions that minimise the weight and/or the total cost of the element. This routine follows the current recommendations prescribed in prEN1993‐1‐5 and evaluates the possibility of using transverse stiffeners along the web to further reduce the weight and cost of the element. The so‐developed routine is presented in the present paper. Also, the advantage of considering the use of high strength steels for such structural members is discussed to propose recommendations to the designers for the selection of the most appropriate steel grade.
Robot supported Wire Arc Additive Manufacturing of Steel Columns
Authors: Waldschmitt Benedikt , Lange Jörg
Published: September 2023

Wire Arc Additive Manufacturing (WAAM) is a robot‐controlled welding process used to build up three‐dimensional structures in steel. Like other Additive Manufacturing (AM) technologies, WAAM allows for geometrically‐complex structures to be manufactured which may be unfeasible using conventional methods. Over recent years, WAAM has also gained prominence in the fields of architecture and civil engineering, with applications ranging from fully‐printed steel bridges to individualized steel components. This paper presents the additive manufacturing process of large‐scale applications, focusing on steel columns with circular hollow cross‐sections (CHS). The paper highlights the specific features of the necessary welding and process parameters before the manufacturing process is described in detail. Digital models and welding trajectories are generated with Parametric Robot Programming (PRP) and serve the robot‐controlled printing process. The AM itself is monitored by multiple process‐control checks giving information about resulting weld thicknesses, heights and welding errors influencing the manufacturing strategy of the CHS columns. To be able to make a closing statement about the load‐bearing capacity of the WAAM‐manufactured CHS, final load tests on (stub) columns are carried out.
Load‐carrying capacity of MAG butt and fillet welded joints on high‐strength structural steels of grade S960QL and S960MC
Authors: Brätz Oliver , von Arnim Mareike , Eichler Stefan , Gericke Andreas , Henkel Knuth‐Michael , Hildebrand Jörg , Bergmann Jean Pierre , Kuhlmann Ulrike
Published: September 2023

The use of high‐strength structural steels brings great advantages in constructions regarding material requirements, weight reduction and productivity. Different steel grades within the S960 range are commercially available but not yet represented in Eurocode 3. The weldability of these steels is limited to smaller process windows to ensure the high material properties. In contrast to steels with moderate strength, there is a considerable risk of softening in the heat‐affected zone causing a strength reduction of the connection. By now, the current EN 1993‐1‐12 only extends the design rules to cover steel grades up to S700. Therefore, the potential of these high‐strength steels cannot be used to its full extent in structural engineering. This study, made within a steel application research project (FOSTA P 1507), deals with the weldability and load‐carrying capacity of butt and fillet welded joints of S960QL and S960MC produced by gas‐shielded metal arc welding. The influence of different bevel geometry, filler metal, and plate thicknesses was investigated. To extend the design rules up to S960, a need of an amendment was found for some combinations.
Monotonic and cyclic response of mild, stainless, and high‐strength steels, and their welded connections
Authors: Ene Anna , Stratan Aurel , Both Ioan , Abrudan Ovidiu
Published: September 2023

In the last decades, a significant number of studies have been devoted to the use of high‐performance steels in construction industry, due to their superior mechanical properties. High‐performance steels include, among others, austenitic stainless steel for its large ductility and excellent toughness and high‐strength steel for its high proof stress. When several steel grades are adopted in the same structural component, welded connections between dissimilar steels have a decisive importance in the seismic performance of a dissipative member. An experimental assessment of the monotonic and cyclic response of the of S235 mild‐carbon steel, 1.4404 austenitic stainless steel and S690 high‐strength steel is presented in this paper. The experimental program concerns a series of tensile tests and low‐cycle fatigue tests in several different protocols, performed both on base materials specimens, and on welded connections between dissimilar steels. Besides the material characterization which could provide reliable data for further calibration of the numerical models, the investigation of welded connections allows assessing the feasibility of combining dissimilar steels in dissipative structures.
Influence of load and high temperature on the post‐fire behaviour of high‐strength structural steels
Authors: Lapuebla‐Ferri Andrés , Pons David , Romero Manuel L. , Gardner Leroy
Published: September 2023

In this work, an experimental campaign was carried out to evaluate the post‐fire mechanical performance of high‐strength steel specimens (grade S700) when being subjected simultaneously to different combinations of tensile load and elevated temperature. To this end, transient‐state tests were firstly carried out to obtain the ‘critical temperature’, i.e., the temperature at which a specimen failed while being simultaneously subjected to tensile load and heated at a constant temperature rate. Secondly, post‐fire tests were performed on unloaded as well as loaded specimens. For that purpose, specimens were heated to temperatures below the critical temperature, cooled down in air and finally submitted to tensile testing. In order to investigate the influence of production route, specimens were extracted from cold‐formed circular hollow sections and hot‐rolled sheets. Moreover, coupons with five different thicknesses were tested to investigate the influence of section thickness on the post‐fire behaviour. Residual values of yield strength, ultimate strength, elastic modulus and ductility were determined from the tests and discussed.
New developments in heavy plates for offshore structures
Authors: Lehnert Tobias , Graf Tobias
Published: September 2023

Wind energy is one of the most important pillars in the urgently needed transformation to a more renewable and sustainable world. Electricity demands as well as hydrogen demands are growing and therefore more and more wind turbines will be installed on‐ as well as offshore. To the success of wind energy steel is indispensable and especially heavy plates play a crucial role in the production and installation of offshore wind farms, e.g. for the towers, the foundations of bottom‐fixed turbines or for the strongly growing demand of floating offshore wind turbines. New developments in heavy plate production can therefore help fulfilling the demands for new and larger turbines as well as to bring overall construction cost down by improving the fabrication of these structures. These developments can be related to plate dimensions, tougher materials and steel grades with higher strength or the weldability of the steel in use. This paper will include some of these developments for offshore wind turbines as well as offshore wind business in general and will give an overview on their benefits.
Moment Resisting Frames under the light of Japanese and European Codes
Authors: Maglio Maria , Nastri Elide , Piluso Vincenzo , Sabatino Simona , Sato Atsushi
Published: September 2023

The aim of the work is to make a comparison between the European and Japanese approaches to design Seismic‐Resistant Steel Frames (MRFs) in high seismicity areas. Therefore, the design rules for both the seismic codes are analyzed and compared. These design rules are applied to design a benchmark structure in DC3 ductility class (according to the new prEN1998) and following the Route 3 procedure (according to the Building Standard Law in Japan, BSL). The examined structural typology is a Spatial Moment Resisting Frames with regularity in plan and elevation configuration. The Japanese approach is divided in two stages. The first one regards the Allowable Stress Design (Elastic analysis) in which all the parts of the structure must be kept elastic; service and damage limitation requirements are in demand. The second stage regards the Ultimate Strength Design (Plastic Analysis) in which no‐collapse requirement and the protection of the human life are in demand. The seismic performance of the designed structures is evaluated by means of pushover analyses.
A Fourier‐series numerical approach for the analysis of tubular members
Authors: Ádány Sándor , Schafer Benjamin W.
Published: September 2023

This paper provides an efficient and robust numerical solution for the linear buckling analysis of tubular members, such as the supporting tower structures of wind turbines. The method uses Fourier‐series approximations for the displacement functions. Longitudinal discretization can optionally be applied, i.e., the member can be divided into segments. The strain‐displacement relationship directly considers the curved geometry. The implementation allows for arbitrary support conditions. Four pure loading situations are considered, uniform – in each segment – along the length: normal force, bending moment, torque, and shear force; however, they can arbitrarily be combined, as is commonly occurring in wind turbine towers. The applied methodology results in a computational advantage compared to the shell finite element method, while still maintaining much more generality and applicability compared with common analytical solutions. Furthermore, the method is supplemented with features, as spectral analysis and buckling length calculation.
Bearing capacity of headed studs under combined tension and shear loading in composite beams with large web openings
Authors: Risch Manuel , Kurz W. , Wolters K. , Janiak T. , Christou G.
Published: September 2023

The use of steel‐concrete composite structures with a high installation grade is becoming increasingly popular in building and industrial construction. To reduce construction height building services are routed through web openings in the girders. However, these openings represent local points of interference where, in the case of composite girders, parts of the acting shear forces are transferred from the web of the steel profile into the concrete slab. This results in additional, local stresses in the remaining steel girder and in the concrete chord, which must be considered in the design of the floor girders and shear connectors. Web openings in composite girders are not addressed in the current European design standard for steel‐concrete composite construction (EC 4). Only with the introduction of the second generation of Eurocodes in the coming years this case will be normatively regulated. During the preparation of the standard further questions about the load‐bearing behaviour arose, as the existing design approaches usually only consider a selection of possible failure scenarios or neglect essential verification steps. A joint research project between the University of Kaiserslautern‐Landau and RWTH Aachen University aims to develop a suitable design concept for composite girders with web openings. Model and beam tests accompanied by numerical simulations will provide further information on the complex local and global load‐bearing behaviour of the composite girders.

This paper presents the results of experimental investigations and numerical simulations on the influence of large web openings on the global load‐bearing behaviour of the shear connectors in the composite joint. Based on 60 pull‐out tests and numerical simulations, the load‐bearing behavior of head bolt anchors under combined shear and tensile loading was researched and evaluated.
Numerical investigation of a steel tied arch bridge under fire loading
Authors: Covi Patrick , Tondini Nicola
Published: September 2023

Bridges are strategic infrastructures designed to withstand operating and accidental load conditions. However, among accidental actions, the current structural standards of bridges do not explicitly consider fire actions. However, the fire risk is not negligible, as highlighted by the scientific literature. In fact, despite the probability of occurrence of a fire impacting a bridge is certainly lower than for building, the consequences can be high. Indeed, high vulnerability to the fire of bridges can have a significant impact on the functionality of the infrastructural network. Too high deformations can cause the loss of functionality of the structure with severe repercussions on vehicular traffic and services often incorporated into the structure. The present work fits into this context by analysing the fire vulnerability of a steel tied arch bridge. In most cases, the restraints at the end of the bridge are considered free or fixed‐end conditions. However, the presence of the thermal joints induces restraint conditions that are in between the two limit cases. The modelling of the thermal expansion joints of the bridge was considered. Different plausible fire scenarios were taken into account and were modelled according to natural fire curves. A series of thermomechanical analyses were then developed to identify the failure modes and times of collapse, as well as the deformation behaviour that can cause the loss of functionality.
Experimental investigation of steel frames made of hybrid steel welded I‐sections
Authors: Yun Xiang , Zhu Yufei , Gardner Leroy
Published: September 2023

An experimental investigation into the structural behaviour of steel frames made up of hybrid steel welded I‐section members is presented in this paper. The tested hybrid steel welded I‐section profile had quenched and tempered S690 steel flanges and an S355 steel web. The experimental programme comprised four two‐dimensional, single storey, single bay frames subjected to different combinations of horizontal and vertical loading, thus enabling different beam, sway as well as combined beam and sway plastic collapse mechanisms to be examined. The frames were fully laterally restrained using a bespoke lateral bracing system to ensure that no out‐of‐plane instability phenomena were experienced during testing. The experimental setup, loading schemes, instrumentation and key experimental results are reported. The experimental results are fundamental to developing an understanding of the behaviour of hybrid steel welded I‐sections at the structural system level. Further research is underway to underpin the development of suitable design rules for steel frames made of such hybrid steel welded I‐section members.
Design of Stainless Steel Cross‐Sections by Inelastic Stability Analysis
Authors: Becque Jurgen , Gilbert Saul
Published: September 2023

While carbon steel cross‐sections are traditionally categorized as Class 1, 2, 3 or 4, depending on when local instability occurs relative to the key stages of yielding, for stainless steel the lack of a well‐defined yield point and the presence of continual strain‐hardening render this approach artificial and superfluous. A new design methodology is therefore needed, which accounts for the effects of both strain‐hardening and local buckling.

The proposed method is based on a modified finite strip method, which accounts for the effects of gradual loss of stiffness due to yielding on the stability of thin‐walled members. Extensive verification of the new method against experimental data showed that cross‐sectional capacities are generally well predicted, with average ratios of the measured to the predicted capacity of 1.18 and 1.19 in compression and bending, respectively, and a standard deviation of 0.10 in both cases. This is a significant improvement over the EN 1993‐1‐4 design rules, where the averages over the same dataset were 1.27 and 1.40, respectively, with standard deviations of 0.14 and 0.17. The rotational capacity of stainless steel cross‐sections in bending was also reasonably well predicted, with an average ratio of measured to predicted curvature of 1.79.