bluuebunny/crossref_metadata_2025 huggingface dataset:
Buckling Verification of Manhole Area of Tubular Steel Wind Turbine Towers via Non‐linear Finite Element Analysis
Authors: Koulatsou Konstantina G. , Chondrogiannis Kyriakos‐Alexandros , Gantes Charis J.
Published: September 2021

As wind turbine towers grow in height and their blades become longer, actions on the towers are also increased and their safe and cost‐effective design becomes critical for the further development of the wind energy sector. One potential failure mechanism of tubular steel towers is shell local buckling between ring flanges. In the present paper, the buckling behavior of a 120m tall wind turbine tower under realistic wind loads is investigated numerically, focusing on the buckling response near the man‐hole opening. To that effect, nonlinear finite element analyses accounting for geometrical and material nonlinearity and imperfections (GMNIA) is employed. GMNIA is performed taking into account initial geometric imperfections with the most unfavorable shapes resulting from the three primary buckling modes, determining the imperfection size according to EN1993‐1‐6 depending on the assumed fabrication quality class A, B or C. Numerical results are compared to analytical verification according to EN1993‐1‐6. Different wind directions are considered. Moreover, to investigate the influence of the stiffening of the manhole to the tower buckling strength, a comparison between three alternatives of stiffened and an unstiffened manhole is performed.
Experimental study on residual stresses of dual phase high‐strength cold‐formed steel angles
Authors: Xia Yu , Li Zhanjie , Schafer Benjamin W. , Blum Hannah
Published: September 2021

The rapid advance in advanced high‐strength cold‐formed steel makes this material promising for the construction industry to use as structural framing, but necessitates an accurate understanding of mechanical properties, including residual stresses. An experimental study was conducted to measure the residual stress which is generated during the member manufacturing process of a press‐braked angle member composed of advanced high‐strength cold‐formed sheet steel. The amplitude and distribution of membrane and flexural residual stresses around the member cross‐section is presented and the magnitude of residual stresses relative to the yield strength for the test specimen and other previous studies are compared. Additionally, the cutoff length typically recommended for residual stress measurements is investigated by comparing the residual stress distribution around the cross‐section for a section taken from the center and near the end of the member.
Comparative study between stressed skin effect of trapezoidal sheet and sandwich panel roof cladding
Authors: Nagy Zsolt , Kelemen Andrea , Zaharia Gelu , Bács Béla
Published: September 2021

Previous research studied the stabilizing effect of sandwich panel roof cladding and trapezoidal sheet cladding, considering pitched roof portal frame structures. It was observed that these cladding types contribute to the transfer of horizontal loads to the main structural elements, acting in a similar manner as roof bracings, while also providing significant lateral stability to the steel members. Certain methodologies were developed in order to introduce this effect into a 3D numerical model while taking into account the connections between the cladding and the purlins, as well as the influence of the fixing method between the purlins and the main structural members. The current study presents two procedures in order to achieve this and aims to present a comparison between these cladding types in terms of sway displacement of the frame structure with semi‐rigid joints and load transfer by applying the developed methodology to a reference building. The comparison is based on detailed analytical and numerical calculations, carried out by combining the design recommendations available for each cladding type and the developed analysis procedures using a 3D structural analysis software. The analysis results emphasize significant stabilization effects on the structure in both cladding cases.
Comparing Fire Behaviour of Restrained Cold‐Formed Steel Columns with Stiffened and Unstiffened Sections
Authors: Laím Luís , Craveiro Helder D. , Simões Rui
Published: September 2021

Although, some experimental investigations have already been conducted and reported in the literature on cold‐formed steel columns under fire conditions, tests on the structural response of CFS columns in compression with intermediate and edge stiffeners and with restrained thermal elongation are rarely found in the literature, hence the relevance of the current investigation. In the present study, the effect of i) cross‐section shape (including single and built‐up sections), ii) web and edge stiffener configurations (webs with and without intermediate stiffeners and flanges with single edge fold stiffeners and double edge fold stiffeners), iii) slenderness (columns with different boundary conditions: pinned and fixed ends), and iv) stiffness of the surrounding structure to the thermal elongation of such columns have been investigated using an experimental campaign. Based on the research results it is clear that the overlapping regions, composite action, number of stiffeners, section geometry and load level take a crucial role in the fire structural behavior of CFS columns.
Fastener behaviour in sheathed light‐gauge steel stud walls under cyclic and monotonic actions
Authors: Ringas Nikolas , Huang Yuner , Becque Jurgen
Published: September 2021

Steel framed buildings using digitally fabricated light‐gauge steel sections, combined with an offsite panelised fabrication approach, are becoming more widespread and contribute towards reducing cost and erection time without requiring a large workforce to assemble them. Currently, design standards mandate the use of K‐ or X‐bracing in these structures, thus neglecting the beneficial influence of the sheathing on the behaviour of the system, in particular its resistance to lateral loads. This composite behaviour is largely influenced by the performance of the fasteners, which may exhibit tilting, shear failure and fastener pull‐out. This paper takes a first step towards accounting for composite action between light‐gauge steel stud framing and calcium silicate board by focusing on the behaviour of the screws connecting both. Key failure modes are identified, based on direct pull‐out tests and monotonic and cyclic connector shear tests. Significant pinching behaviour was observed under cyclic excitations.
Behaviour of rectangular concrete filled tubular flange girders under combined loading
Authors: Al‐Dujele Rana , Cashell Katherine A.
Published: September 2021

Steel‐concrete composite construction can provide an efficient structural solution by utilizing the two component materials to create a single effective composite section. The high tensile strength and ductility of steel combined with the excellent compressive strength and robustness of concrete results in an effective composite cross‐section which can be used in a wide variety of applications. There are a number of different shapes of composite beam, and this paper is focussed on a relatively new structural solution called concrete filled tubular flange girders (CFTFGs). These comprise a steel beam in which the top flange plate is replaced with a concrete‐filled hollow section. The compression flange can be any shape (e.g. circular, rectangular, and pentagonal) and the focus in the current paper is on simply supported girders with a rectangular section for the compression flange (i.e. RCFTFGs). These members have very high lateral torsional buckling resistance compared with conventional steel I‐girders of similar depth, width and steel weight and are therefore capable of carrying very heavy loads over long spans. However, they are complex to analyse and their behaviour is governed by several inter‐related parameters which are investigated and discussed herein. Given the most common applications of these girders, such as in bridges and carparks for example, they are frequently exposed to a simultaneous combination of high axial loads and bending moments. Although current design codes offer rules for the design of composite columns under combined loading, the design of RCFTFGs, which are asymmetric in nature under the combined effects of tension and bending, are not explicitly included. This work aims to investigate the ultimate strength of RCFTFGs with stiffened webs under the combined effects of various levels of axial tension and positive (sagging) bending moment. Nonlinear three‐dimensional finite element analyses using the ABAQUS computer software package have been developed to facilitate the study. The model is validated using available experimental data and then employed to conduct an extensive parametric study. It is shown that the moment capacity of RCFTFGs is reduced in most situations under the presence of an axial tensile force in the steel beam. In addition, the tensile capacity of the RCFTFGs is limited by the axial capacity of the steel beam alone, with little contribution from the concrete infill. Several influential parameters are examined and conclusions are discussed. Based on the finite element analysis, the moment–axial force interaction relationship is presented and discussed.
Experimental and numerical investigations on steel‐concrete interaction of embedded corrugated web composite members
Authors: Németh Gábor , Kovács Nauzika
Published: September 2021

The application of trapezoidal corrugated plate as the web for girders, thanks to a number of favorable features, modernizes the manufacture of steel‐concrete composite and hybrid structures and provides an alternative, competitive structure for small, medium and large span beams. However, the traditional headed stud shear connectors on the top flange can be considered obsolete in many ways. By embedding the corrugated steel web to the concrete slab, other types of connections should be used, and the behavior of these kind of connections are really promising. In fact, the embedded corrugated web itself functions as a shear connector, though other additive connectors should be used. To understand the structural behavior and design of these embedded connectors, the first step is the examination of the embedded web.

The focus of the research presented in this paper is on the interaction behavior of embedded trapezoidal corrugated webs with additional mechanical shear connectors. As the first steps of the research comprehensive experimental program was completed in the Structural Laboratory of the Department of Structural Engineering in BME. This paper provides an overview for 8 (test) 12 (FE model) specimens of the push‐out test program with the aim to introduce the structural behavior of embedded corrugated steel web and the influence of structural parameters on the shear resistance and deformation capacity through experimental and numerical investigations.
Behaviour of fully encased composite columns under cyclic loads
Authors: Alsamawi Almoutaz bellah , Boumechra Nadir
Published: September 2021

Concrete and steel have different advantages, concrete has high compression strength and low cost while steel has high tensile strength, rigidity and ductility. Composite members have other beneficial qualities beside all of them. Composite columns are used extensively in modern buildings essentially in industrial buildings. The main purpose of this study is an analysis and a comparison between the responses (load‐displacements) of different types of composite columns under cyclic loads. For this purpose, a three‐dimensional (3D) finite element model is developed for the columns, the finite element analysis of composite columns is carried out by using ANSYS code. The numerical model considers the elasto‐plasticity of materials and the non‐linearity of contact friction. It is interesting to observe a large ductility of these composite elements and the efficiency of some types of the composite columns than others. The aim of the study is to analyze the encased composite columns under cyclic loads focused on the different type of steel section. The parameters studied are the influence of axial load levels, skeleton curve, ductility, energy dissipation and the peak lateral load also carried out. The results indicate that the first columns of the specimens have a low specimen energy dissipation due the durability of the columns is higher than the axial load applied, and for better ductility and energy dissipation the axial load level of fully encased composite columns should be limited to approximately a value of 0.6.
Numerical investigation for the design of rectangular concrete encased steel composite columns
Authors: Ergun Ozgun , Schäfer Markus
Published: September 2021

Advanced design methods are becoming more important for the structural analysis. However, their results depend strongly on the quality of the numerical model and its underlying assumptions. Current Eurocode 4 does not provide clear guidance for this analysis type.

A literature review on the compression tests conducted on concrete encased steel composite columns is presented. It was found out that there is a lack in the literature when it comes to the testing of slender composite columns as opposed to numerous tests done on stub columns. A selection of existing specimen tests are then simulated using finite element analysis software ABAQUS. Nonlinearity in the model was defined through materials and geometry. The interface modelling between steel and concrete as well as the modelling of load introduction are discussed. The finite element model was intended to be as generic as possible so that it can be taken as a basis for future parameter studies. Moreover, the column resistance check using interaction curves was discussed. Different approaches to form interaction curves namely strain limitation and plastic section capacity were compared.
Structural response of aluminium alloy concrete filled tubular columns
Authors: Georgantzia Evangelia , Ali Shafayat Bin , Gkantou Michaela , Kamaris George S. , Kansara Kunal , Atherton William
Published: September 2021

There is an increasing trend of using structural aluminium within the construction industry, due to its superior mechanical properties, such as high strength‐to‐weight ratio and high resistance to corrosion. The use of aluminium combined with concrete can be advantageous in terms of the resultant structural capacity. Currently, the design standards for the structural use of aluminium are substantially conservative and less exhaustive, which limits the full exploitation of aluminium as a structural material. This paper aims at developing more reliable structural design specifications based on experimental testing of aluminium‐concrete composite columns. A series of specimens comprising concrete‐filled aluminium hollow sections were experimentally investigated. Square hollow sections and rectangular hollow sections with different aspect ratios were considered. The hollow sections employed 6082‐T6 aluminium alloy and were filled with concrete of C30 grade. The specimens were subjected to gradually increasing axial compressive loading until their failure. The behaviour of the specimens was observed through continuous monitoring and recording of the strain and displacement through instrumentation mounted on the specimens at critical locations. The experimentally obtained load capacities were compared to those predicted by European design specifications. Conclusions with regards to the structural efficiency of concrete‐filled aluminium alloy columns are drawn and design recommendations in line with the observed structural response are made.
Concrete fatigue of composite constructions with rib shear connectors
Authors: Christou Georgios , Hegger Josef , Classen Martin
Published: September 2021

Rib shear connectors are gaining increasingly attention in the field of composite constructions. Especially in bridge constructions, rib shear connectors offer many advantages compared to conventional composite shear connectors such as headed studs. In order to describe the load‐bearing behaviour of rib shear connectors under cyclic loading, the successively increasing slip resulting from the cyclic loading of the shear connectors must be taken into account. The latter leads to the growth of the relative displacements along the composite joint and thus, to the degradation of the previously rigid shear connection. This effect leads to rearrangements of internal forces between the composite partners through which the load bearing behaviour and load bearing capacity of the structure alter. In this article results of experimental investigations on two cyclic single Push‐Out‐Tests (sPOT) and one full‐scale girder test regarding the degradation of the composite interconnection are presented and analysed. The investigated shear connectors in the full‐scale girder test are subjected to a comparable load history to that of the connectors in the sPOT. The results give insight into the effects of the degradation of the shear connection, as previously seen in sPOT, on the overall load bearing behaviour of composite girders.
Crack propagation and residual load‐bearing behavior of composite dowels – effects on the global behavior of composite girders under cyclic loading
Authors: Wolters Kevin , Christou Georgios , Feldmann Markus
Published: September 2021

Fatigue of a composite girder according to Eurocode 4 is carried out on the decisive shear connector. It is not taken into account that the composite girder is an internally highly statically indeterminate system in which the failure of a dowel does not necessarily lead to the failure of the girder. This applies in particular to composite dowels which are characterised by a crack propagation phase with a high residual load‐bearing capacity of a damaged dowel.

In own small part and girder tests as well as numerical studies, numerous positive load‐bearing effects could be identified in composite girders with composite dowels, which increase the lifetime of the girder. In case of an initial crack in a steel dowel, followed by crack propagation, the stiffness degradation of the damaged connector leads to a redistribution of forces. The lifetime of a girder is limited by the residual capacity of the composite joint or by a global failure with increasing partial connection.

A global safety concept for composite girders taking into account the crack development and residual strength of the dowels as well as the redistribution of forces within the composite joint holds an enormous economic potential. This article shows how these effects can be taken into account.
Partial shear diagram of slim‐floor beams
Authors: Zhang Qingjie , Schäfer Markus
Published: September 2021

Slim‐floor beams which have the steel sections fully or partially integrated into the concrete slab lead to a significant reduction of the construction height. Due to its flat lower surface, it provides favourable solution for technical installation. According to EN1994‐1‐1, for composite beams plastic moment resistance is assumed. In the case of slim‐floor sections, due to the reduced construction height by the integration of the steel beam in the concrete and its extended bottom flange, a large compression zone height may be expected, thus concrete failure in the compression zone may happen before reaching the plastic moment resistance Mpl,Rd. Here, strain limit resistance becomes decisive. For design with partial shear connection, EN1994‐1‐1 provides the partial shear diagram based on the plastic bending resistance Mpl,Rd which is not always suitable for slim‐floor beams. Based on strain limited method, the more suitable partial shear diagram of different slim‐floor beams can be developed. From parametric studies of different types of slim‐floor beams, the impacts of critical parameters on the design are highlighted, and the limitations of the current plastic resistance based partial shear diagram are suggested. A simplified calculation method for situation beyond the limitation are also proposed to guarantee an economical design of those beams.
Conception and design of high‐performance steel‐concrete composite slabs
Authors: Pereira Miguel , Simões Rui , Craveiro Hélder
Published: September 2021

The main advantages of steel‐concrete composites slabs are the speed of construction, the elimination of conventional shuttering and the reduction of props. This structural system is widely used, mainly in the execution of floors in composite buildings. Usually, the longitudinal shear resistance is commonly provided by the embossments along the steel sheet. This paper presents an innovative reinforcing system that increases the longitudinal shear capacity and consequently the structural performance of composite slabs. The system is constituted by a set of transversal reinforcement crossing the steel sheeting which allows to take more advantage of the high bending resistance of composite slabs and increase their ductility. Two experimental campaigns were carried out: a small‐scale test programme, to study the resistance provided by the reinforcing system, and a full‐scale test programme, to assess the efficacy of the proposed reinforcing system. The present study allowed to conclude that the resistance and the ductility of composite slabs using the proposed reinforcing system are significantly increased. The design methodology based on the partial connection method can be used to predict the resistance of a composite slab incorporating the proposed reinforcing system.
FEM Analysis of Bridges with Encased Continuous Shear Connectors
Authors: Vanova Patricia , Kvocak Vincent , Kozlejova Viktoria , Dubecky Daniel , Kanishchev Ruslan
Published: September 2021

Composite steel‐concrete constructions with encased I‐beams were initially used as composite floors. Nowadays, they can be usually seen as short railway bridges with span up to 20m. Their main advantages include simplicity of their construction, their low construction height and their effectiveness. To make them more effective, the steel I‐beams were replaced with perforated steel strips. At Technical University of Košice, Faculty of Civil Engineering, several continuous shear connectors with new design were proposed. In order to prove their effectiveness, numerous experiments – push‐out tests, four point flexural tests – were performed at Laboratory of Excellent Research. The purpose was to determine the shear and bending resistance of the connectors. Afterwards, the finite element models were created and analyzed using ABAQUS/CAE software. This paper deals with numerical program of four‐point flexural tests of two strips. The most clue modules ‐ properties, load, step, interaction and mesh are described.
Macro‐modelling of 3D tubular column‐to‐truss beam joints
Authors: NGUYEN Tien Minh , RODIER Anthony
Published: September 2021

The European Research Project “Innovative 3D joints for robust and economic hybrid tubular construction” aims at developing innovative plug‐and‐play joints for hybrid tubular construction where square (or rectangular) tubular columns are combined with truss‐beams composed of cold‐formed lightweight steel beams. This kind of joints provides a highly efficient structural system for modular solutions that are essential for fast‐track construction. An important task of this project is to develop a 3D joint model that takes into account 3D behavior of joints. The 1D component method presented in the Eurocode 3 part 1‐8 is extended to a 3D level by considering all relevant components and interactions between them.

In the literature, some studies showed that the out‐of‐plane deformation of the tubular column faces depends on the loading and boundary conditions of the other faces. The first objective of this article is thus to propose a new 2D springs model taking into account the correlation between out‐of‐plane deformations of the faces of rectangular hollow section (RHS) columns. Then, a formulation of a 3D macro‐element of the joint is presented. Finally, the model is validated using two distinct procedures: 1) an analytical procedure implemented in a symbolic calculation software; 2) a modelling by finite elements.
Yield load estimation of plug & play N type RHS truss connections
Authors: Szlendak Jerzy K. , Szpyrka Adrian
Published: September 2021

The article presents a new concept of II generation N type RHS plug & play truss connection, made in non‐welded technology. In II generation of such joints the tension bracing is not made with two flat bars on both sides of RHS chord and connected with a screw passing through the chord (I generation), but with single round rod going through the clamping blocks and threaded at the ends what allows to screw and fix it to the blocks. Representative connections of such truss are analyzed. Concept of resistance calculations of these joints, using the component method, is shown. Test results and the theoretical resistance follows the different modes of the connections failure are compared.
Numerical analysis of the influence of curling on the strength of connections with one bolt
Authors: Toporiš Matej , Može Primož
Published: September 2021

Curling failure typically appears in bolted connections with thin plates, where the force is transferred by bolt bearing. The curling phenomena is related to the high compressive stresses caused by bolt bearing, which cause the plates to buckle, reducing the bearing strength of connections. Since the reduction of the bearing strength due to curling is not considered in design codes, the curling phenomenon has been studied numerically to understand the mechanical behaviour and to develop simple design rules that take into account reduction in bearing strength. The reduction factor for reducing the bearing resistance by curling was developed taking into account the Eurocode approach, i.e. by calculating the elastic critical force associated to curling and the relative slenderness. Therefore, the elastic critical force in relation to curling was obtained by parametric buckling analysis in finite element software Abaqus. These results were used to develop a simple analytical model for the calculation of the elastic critical curling force. The reduction factor was obtained from the relationship between the results of parametric GMNIA and relative slenderness. The strength of single bolt connections was determined by geometrical and material nonlinear analysis with imperfections (GMNIA) considering various parameters, namely ratio of the bolt diameter to plate thickness, end distance e1, edge distance e2, material grade (S235, S690), shape and amplitude of imperfections and boundary conditions. The accuracy of the reduction factor for bearing strength is checked on the basis of experimental data given in literature.
Innovative 3D joint for steel modular construction
Authors: da Silva Luís Simões , Tankova Trayana , Craveiro Hélder David , Silva Luís Carlos , Simões Rui , Costa Ricardo
Published: September 2021

In recent years, the modular construction has been used in multi‐story and even high‐rise construction. Pre‐fabrication by off‐site manufacture leads to faster construction, improved quality and reduced resources and waste.

The research work presented in this paper is carried out in the scope of the European project INNO3DJOINTS and it aims to develop innovative plug‐and‐play joints which enable modularity. The developed modular construction system is hybrid, whereby tubular columns are combined with cold‐formed lightweight steel profiles to provide a highly efficient structural system. The innovative connection is a device that connects the lightweight truss girder with the tubular column. It consists of a socket welded to the column and a T‐plug which is connected to the truss girder with a lap‐joint. Upon assembly, the T‐plug is simply fitted into the socket. Moreover, the newly developed innovative hybrid plug‐and‐play joints are also suitable for other specific situations such as retrofitting of existing buildings.

This paper presents the developed structural system and the characterization of the plug‐and‐play joints based on experimental tests.
Critical Comparison of Assessment Codes for Steel Moment Resisting Frames
Authors: Gutiérrez‐Urzúa Fernando , Freddi Fabio , Sarno Luigi Di
Published: September 2021

Many existing steel multi‐storey frame buildings worldwide were designed prior to the introduction of modern seismic design provisions or based on outdated hazard maps considering low values of seismic intensity. This often resulted in buildings showing low performances with respect to earthquake loads. Assessment codes, such as the Eurocode 8 Part 3 and the ASCE 41, have been conceived to provide tools to assess the seismic performance of existing structures, to evaluate their adequacy with respect to the current safety standards and the need for seismic retrofit. However, recent research studies have revealed the necessity for a revision of these codes. In particular, for steel moment resisting frames, the current European regulation shares many similarities with older versions of the American codes, but has failed to incorporate changes based on the state‐of‐the‐art knowledge. In addition, the undergoing update of other parts of the Eurocode motivates a full revision of the current standards. This paper compares the assessment procedures of the European and American codes. Two low‐code steel Moment Resisting Frames were considered for case study purposes and the assessment was performed based on three local Engineering Demand Parameters (EDPs), i.e., column's rotation, beam's rotation and panel zone's shear distortion, and the inter‐story drift as global EDP. Incremental Dynamic Analyses were performed for the development of component and system fragility curves. The present work aims to identify some challenges and to provide some preliminary insights for the revision of the Eurocode 8 Part 3.
Study of behaviour of S235‐S460 structural steel elements cut using laser processes
Authors: Zanon Gabriele , Bursi Oreste S. , Bison Paolo , Valli Alberto
Published: September 2021

Laser cutting is an appealing solution to promote steel construction for high machining speed and precision. As a thermal process, it alters the material properties in the heat affected zone (HZA) and, consequently, the structural response at high‐cycle fatigue loadings. With these premises and by means of a multidisciplinary research, the work studies the effects on S235‐S460 steel elements. In order to study the thermo‐mechanical effects produced by the laser cutting process, with particular attention to fiber laser, a finite elements (FE) numerical model was developed with ABAQUS. Both numerical model calibration and validation were carried out through experimental results obtained by means of monitored cutting processes and material tests. The agreement observed between numerical and experimental results highlights the importance of the interdisciplinary research in the study of complex non‐linear thermo‐mechanical problems like those involving laser cutting. Main results of this study concern the effects of laser cutting on the residual stress distribution and on the response of steel elements subjected to high‐cycle fatigue loadings.
Fatigue design in penstocks – comparison of the nominal stress and structural stress method for common details
Authors: Ecker Alexander , Unterweger Harald
Published: September 2021

Penstocks in hydro power plants have a very long working life. They can have high pressure variations during service life, especially in pumped storage power plants caused by the dynamic pressure. Therefore, the fatigue design can be a dominating factor in the design of penstocks. In this paper, two common used construction details in penstocks are investigated with the nominal stress and the structural hot‐spot stress method for fatigue verification. The investigated construction details are: i) a wall thickness transition of the penstock with a weld along the circumference and ii) a ring stiffener welded to the penstock. The results of the different methods for fatigue verification for these two construction details are compared with each other, with variation of different geometric parameters. Also an analytical solution for the stresses in the hot‐spot for the two construction details, based on the semi‐membrane theory of cylindrical shells, was developed. Based on that stresses, stress concentration factors kHS are calculated and are available for practical applications in form of presented Tables in this paper. With the calculated stresses by the semi‐membrane theory in the hot‐spot it can be shown, that they are nearly equal to the hot‐spot stresses of a Finite‐Element‐Analysis, based on the IIW recommendation. Finally, a recommendation for fatigue verification of the two common details in penstocks is given.
Detection of short cracks in riveted connections using Lock‐In‐Thermography
Authors: Sieber Lars , Urbanek Ralf , Bär Jürgen
Published: September 2021

Although many riveted bridge structures made of old structural steel from the 19th and early 20th centuries are still in use today, there is usually no need to replace them. When assessing these steel structures with regard to necessary refurbishment or strengthening measures, engineers need information about the remaining fatigue lifetime in particular.

Often no sufficient remaining fatigue life can be determined based on normative S‐N‐curve assessment. An initiation of fatigue cracks has to be assumed. These cracks occur primarily at the edge of the rivet holes. In the early phase of crack growth below the rivet head, the crack cannot be found in a visual inspection of the structure. For this reason, the remaining cyclic lifetime based on fracture mechanics is determined assuming a start length of the crack beyond the rivet head.

This paper reports investigations using thermoelastic stimulated Lock‐In‐Thermography as a NDT method for detection of hidden cracks in riveted joints. The results have shown that cracks below rivet heads can be detected. This is possible despite the presence of a corrosion protection coating. The detectable crack length depends mainly on the level of stress and the loading frequency.
Fatigue Life Prediction of Welded Girders with Flange Thickness Transitions and Cope Hole
Authors: Röscher Stefanie , Knobloch Markus
Published: September 2021

The paper presents an analytical and numerical approach for the fatigue life prediction using local concepts. A Two‐Stage‐Model is applied to a welded girder with thickness transition and cope hole to determine its fatigue life. The model follows the distinction between crack initiation and crack propagation according to the phenomenological background. Using the Strain‐Life‐Approach and the Crack Propagation Approach the local geometry and likely failure position influence the determined fatigue life for the initiation and propagation phase individually. The results are presented in terms of S‐N curves for initiation, propagation, and total fatigue life.
Numerical‐experimental analysis of a braced steel frame subjected to fire following earthquake
Authors: Covi Patrick , Tondini Nicola , Korzen Manfred , Tsionis Georgios
Published: September 2021

Many historical events have shown that, after an earthquake, fire may be triggered by seismic‐induced rupture of gas piping, failure of electrical systems, etc. The current engineering design methods still ignores many aspects of multi‐hazard and in particular fire following earthquake (FFE) analysis. In this respect, the aim of this paper is to study the behaviour of a braced steel frame subjected to seismic‐induced fire. In particular, FFE numerical analyses were conducted on a four‐storey three‐bay braced steel frame with concentric bracings. The results of the numerical analyses served to design the FFE tests performed on unprotected and protected columns belonging to the bracing system. The fire tests after the seismic event were carried out by considering the effects of the surrounding seismically damaged structure. Results of the FFE tests on unprotected columns are reported along with the numerical model calibration.
Dissipative joints under impact loadings
Authors: D'Antimo Marina , Latour Massimo , Demonceau Jean‐François
Published: September 2021

Unforeseen and unpredictable exceptional events can lead to abnormal loading distribution in the structures; however, in such situation, structures have to withstand additional loadings to avoid disproportionate damage and progressive collapse. Impact loadings are among the exceptional events that a structure can experience during its lifetime. In order to give a contribution to the research on impulsive loading on structural joints, this work focuses on the behavior of slide hinge joints (SHJ) with a Symmetric Friction Damper (SFD) under drop weight impact tests. Six drop weight impact tests on a double‐sided beam‐to‐column joints were performed and a 3D finite element model was created and validated in ABAQUS/CAE Explicit. The model includes the calibration of material damage, correlating the equivalent plastic strain to the stress triaxiality, damping of the system, calibrated on elastic impact tests using Rayleigh's classical damping and strain rate sensitivity through the Johnson Cook model. Furthermore, a parametric analysis was performed in order to investigate the influence of three parameters on the joint behavior: the impact velocity, the impact mass and the impact energy. The energy is used to estimate the dissipation rate of the joint, which can be considered as a reliable parameter to quantify the joint behavior under drop weight impact.
Investigation of residual stresses on the fire resistance of unrestrained cellular beams
Authors: Oribi Sabrina Benyettou , Kada Abdelhak , Lamri Belkacem , Mesquita Luis MR
Published: September 2021

It is being a common engineering practice to use steel beams with web openings in buildings requiring long spans, besides giving an important additional advantage of allowing services through instead of underneath the beams. The presence of these openings is penalizing the carrying capacity at ambient temperature and in the case of fire due to large cells and double nonlinearity geometric and material a complex behaviour take place. In this study, numerical models for beams having closely spaced large openings are simulated with ISO834 fire loading including both nonlinearities cited above in the primal investigation. Followed as a second investigation, is the effect of residual imperfections added to the numerical model mentioned above and simulated for different diagrams as presented within updated literature. All simulations were done using the finite element software ANSYS, to analyse the results captured for lateral torsional buckling (LTB) behaviour in terms of vertical and lateral displacement, von Mises stresses for different sections at ambient and fire conditions. For this parametric study, the change in cross‐section geometries, opening spacing, beam length on the LTB of cellular beams is analysed.
Post‐fire ductility of reinforcing steel
Authors: Lapuebla‐Ferri Andrés , Pons David , Romero Manuel L.
Published: September 2021

In this work, the post‐fire ductility of steel reinforcements in reinforced concrete structures was studied experimentally. Specimens were subjected simultaneously to a constant tensile load and a heating up to a target temperature, which was a percentage of the ‘critical temperature’ for the load level applied. After that, the specimen was left to cool to room temperature and submitted to tensile testing in order to evaluate its residual ductility. Critical temperatures for each load level tested were obtained by performing transient‐state tests. In addition, unloaded specimens were subjected to the same thermal cycle of heating and cooling for comparison purposes.

Results indicated that the residual ductility of a reinforcement depends on the maximum temperature reached and the load level it was bearing during the heating and cooling thermal cycle. It was demonstrated that ductility properties were not always recovered after cooling down, and the current code requirements for the ductility class of a reinforcement bar were not fulfilled. The obtained information can be relevant when deciding on the eventual reinstatement of a reinforced concrete structure in a post‐fire scenario.
Attempts to improve on the V‐hull structural design for air‐blast loading applications
Authors: Langdon Genevieve , Curry Andrew , Shekhar Vinay , Siddiqui Aashir , Murray Christopher , von Klemperer Chris
Published: September 2021

Mine resistant ambush protected vehicles often use mono‐V structures in the design of their hulls for blast protection purposes. These hulls deflect blast waves laterally in the event of a landmine detonation directly beneath the vehicle. Lower internal angles offer greater deflection capability, reducing the impulse transfer to the vehicles, but at the cost of increased ride height. This paper reports results of attempts to improve on V‐hull structural designs for air‐blast loading applications, where scaled blast tests are performed to evaluate the designs in terms of structural deformation, rupture and impulse transfer characteristics. Structures with double V and W profiles are compared to mono V structures with a 120° internal angle, such that the proposed designs do not increase the ride height. Results showed that the double V‐structures limit the central deformation, but some designs have severe deformation at the interface of the central V plate and the shallow base angle structure. W structures seem to be susceptible to rupture at low charge masses. There is no single answer to improved blast protection of vehicle hulls, as design choices must be driven by the anticipated threat range, the important performance metrics and other operational considerations.
Simplified and advanced design for stainless steel members under concentrated transverse loading
Authors: dos Santos Gabriel , Gardner Leroy
Published: September 2021

A comprehensive investigation into the behaviour of structural stainless steel members under concentrated transverse loading is presented in this paper. A total of 34 member tests and over 500 finite element simulations have been performed covering three types of concentrated transverse loading – internal one‐flange, internal two‐flange and end one‐flange loading, three stainless steel grades – austenitic, duplex and ferritic and key influential parameters such as bearing length, web slenderness and beam span. The results have shown that existing design recommendations are conservative and that there is considerable scope for the development of more economical design guidance. New design equations are proposed that offer 10% to 20% improvements in capacity predictions over the current design formulae in EN 1993‐1‐4. These proposed design equations are to be included in the next revision of the European standards. An alternative design approach based on numerically generated reference loads – i.e. the plastic collapse and elastic buckling loads – in conjunction with strength curves, has also been proposed. This advanced FE‐based design approach allows the extension of the design scope to non‐standard cases, such as webs with partial depth stiffeners and members with web holes. The reliability of both design approaches has been successfully verified by statistical analysis.
Economic benefit of high strength steel sections for steel structures
Authors: Saufnay Loris , Jaspart Jean‐Pierre , Demonceau Jean‐François
Published: September 2021

The present work aims at studying the field of interest of high strength steel rolled sections (fy>460 MPa) for steel structures from an economic point of view. Whilst these high strength steel profiles do not exist yet, steelmakers are able to produce more resistant steels through more efficient production processes and a future emerging of these particular steel profiles is likely to occur. The use of this kind of steels can lead to a significant material saving. So, the use of high strength steel leads to lighter structures requiring smaller foundations, lower transportation and construction costs but also emitting less CO2. However, buckling, fatigue or deflection requirements often reduce the advantage of high strength steels. It is for this reason that the designer is sometimes reluctant to use them. A study establishing the areas of economic benefit of high strength steel tubes in steel and composite structures had already been carried out at the University of Liège [8]. The goal of the present is to extend this study to rolled sections (H‐shape and I‐shape). It therefore consists in providing methods in order to help the designer determining the economic benefit of high strength steel for structural elements subjected to different loadings. These ones are then used to determinate the areas of economic benefit of the high strength steels in comparison to regular steel, depending on their relative costs.
Numerical and Theoretical Modelling of the Web‐Post Buckling of Stainless Steel Cellular Beams
Authors: Shamass Rabee , Guarracino Federico
Published: September 2021

Cellular steel beams are widely used in modern constructions to achieve long spans and to provide passage for service installations such as ducts and cables. The present paper is concerned with the use of stainless steel in cellular beams. In fact, available design methods to calculate the shear strength of web‐post are applicable only to carbon steel that exhibits a linearly‐elastic behaviour with a clear yield point followed by plastic deformation with little amount of strain hardening. Conversely, stainless steel exhibits a non‐linear stress‐strain relationship with high level of strain hardening. Consequently, new design provisions for the web‐post buckling of cellular beams made from stainless steel capable of exploiting the material strain hardening are highly desirable. Since no experimental investigations are available in literature for cellular beams made from stainless steel, finite‐element models have been developed and validated against tests conducted for carbon steel cellular beams. The structural behaviour of stainless steel cellular beams with various geometries and material characteristics is investigated through a large number of finite element analyses and a simple mechanical model for the Web‐Post Buckling (WPB) failure is developed and calibrated against the numerical results to provide the basis of a reliable design method.
Experimental and numerical investigations on the rotation capacity of high strength steel beams
Authors: Bartsch Helen , Pauli Gesa , Eyben Felix , Schaffrath Simon , Feldmann Markus
Published: September 2021

In order to design efficient and highly utilised sections, the plastic/plastic design approach depicts a valuable tool. Concerning plastic design, Eurocode 3 requires only Class 1 cross‐sections and material grades up to S460, depicting conventional strength steels (CSS), to be used. High strength steels (HSS) with yield strengths up to 700 MPa are not considered appropriate for plastic design due to their lower ductility. However, the exclusion of HSS appears to be unnecessary in the light of recent test results. Experimental investigations on 20 homogeneous and hybrid high strength double symmetric I‐section beams have been conducted comprising various slenderness characteristics of flange and web and different span lengths. The results show that the rotation capacity value of R = 3, currently required by EC3 regulations, can actually be achieved by high strength steel beams depending on their cross‐sectional characteristics. Additionally, the experimental tests have been recalculated numerically. The material characteristics of the models have been defined by flow curves, which have firstly been calibrated on the basis of small‐scale tensile tests and furthermore slightly fitted to the full‐scale test results. Ductile material failure in terms of crack initiation and evolution is considered by incorporating a damage mechanics model. It can be shown that experimental and numerical results show very good accordance.