bluuebunny/crossref_metadata_2025_split huggingface dataset:
08.46: Local buckling of thin‐walled tubes encased in concrete
Authors: Albareda‐Valls Albert , Carreras Jordi Maristany , Carrera David Garcia 
Published: September 2017

ABSTRACTLocal buckling of concrete‐filled tubes has been studied by several researchers these recent years, due to the evidence that the limits provided by the Eurocode for considering local buckling in steel tubular sections are clearly non‐conservative when taking the confinement effect of concrete into account. Lateral pressure coming from concrete when loading both components at the same time in CFT sections leads to reduce the stability of the cylindrical shell in terms of local buckling, since it is subjected to a vertical and lateral pressure at the same time. However, this phenomenon has exactly the opposite effect when the encased component is the steel tube; this is the case of the concrete‐encased tubes, a very interesting typology for its mechanical and fire response. In these sections, the encased tube is subjected to a uniform compressive pressure from outside that clearly enhances the stability of the shell. This study presents a numerical and analytical approach to local buckling in these sections, by using a complex numerical model calibrated with real thick‐walled previous experiments. The conclusions of this text pretend to describe the efficiency of these sections in terms of local buckling, and to fix the base for a wide experimental and numerical campaign to determine how each parameter influences to the mechanical response.
08.53: Integral analysis of steel concrete beams, Regarding creep of concrete according EC2, versus (AAEMM) of bažant
Authors: Partov Doncho , Kantchev Vesselin 
Published: September 2017

ABSTRACTThe paper presents analysis of the stress‐strain behaviour due to creep in statically determinate composite steel‐concrete beam according to AAEM method of Bažant in comparison with numerical method. The analysis is based on the results obtained by numerical solution with Volterra integral equations derived for determining the redistribution of stresses in beam section between concrete plate and steel beam with respect to time “t” and creep of concrete according EC2 provisions. On the basis of the theory of the viscoelastic body of Arutyunian–Trost‐Bažant it is analysed the migration of stresses from concrete plate to steel beam using two independent Volterra integral equations of the second kind and two independent algebraic equations, during the period of 70 years. The closeness of the results obtained by the two methods is shown with an example from the bridge practice.
08.58: Ultimate behaviour and design of hybrid flat slabs with steel shear heads
Authors: Bompa Dan V. , Elghazouli Ahmed Y. 
Published: September 2017

ABSTRACTThis investigation examines the performance of hybrid reinforced concrete flat slabs, incorporating fully‐integrated shear‐heads at connections to steel columns, through a series of numerical simulations and parametric studies. Validations of the adopted nonlinear finite element procedures, which employ concrete damage plasticity constitutive models, are carried out against experimental results on hybrid members. Comparison of the numerical simulations against the test results shows close correlations in terms of ultimate strength, deformations and stress levels in the constituent elements of hybrid members. This is followed by a series of parametric assessments on key structural parameters for hybrid flat slabs with steel shear heads. The results of these investigations enable the identification of three modes of failure as a function of the interaction between the shear‐head and surrounding concrete. The findings permit the development of improved analytical models for predicting the rotational response as well as ultimate strength of such members. In addition, recommendations are given for the determination of shear‐head dependent parameters, which are required for practical design purposes, with particular focus on the embedment length and section size of the shear‐head elements. The suggested expressions for assessing the shear‐head characteristics offer a more reliable design approach in comparison with existing methods and are suitable for effective practical application and implementation in codified procedures.
08.59: Shear behavior of concrete walls reinforced by multiple steel profiles Calibration of numerical model
Authors: Dragan Dan , Plumier Andre , Degée Hervé 
Published: September 2017

ABSTRACTThe current state of EN 1994 and EN 1992 does not provide correlated solutions related to the design of concrete walls reinforced by multiple steel profiles. Explicitly, Eurocode 4 is setting clear boundaries in the design of composite walls by limiting the possibilities to elements reinforced by a single profile or multiple connected profiles. A number of previous studies have shown that the method proposed by Eurocode 2 regarding classical reinforced walls provides a good prediction of the bending capacity of the wall; however limited information regarding their shear capacity can be found. The current paper is having as starting point a theoretical approach for determining the shear performances of RC wall reinforced by multiple steel profiles, coupled with an experimental campaign. The experimental campaign comprises 6 walls, ranging from a classic RC wall taken as a reference to configurations with multiple profiles with studs or plate stiffeners to ensure the transfer of the longitudinal shear at the steel‐concrete interface. The FE model is going to try to reproduce the behavior showed by the walls. The objective of the present paper is to present a comparative analysis between results obtained using a FE software and results from the experimental campaign carried out in the frame of the European research program SmartCoCo. The obtained results will be used to confirm once again the design method based on theoretical reasoning, proposed by the authors and presented in previous papers. This contribution contains a brief description of the test specimens, presents a selection of the most relevant experimental results in parallel with the FE results and a set of conclusions regarding the results. It can be concluded from this set of tests that the new design method is able to predict the shear capacity with a good accuracy and can therefore be considered as a suitable solution for designing practical cases.
09.01: Numerical methods for the fatigue assessment of welded joints – influence of misalignment and geometric weld imperfections
Authors: Taras Andreas , Unterweger Harald 
Published: September 2017

ABSTRACTThe fatigue design life of welded joints is increasingly assessed by using numerical methods, such as the structural (hot‐spot) stress method and the effective notch stress method. When compared to the classical design approach using nominal stress S‐N design curves, these methods offer the advantage of flexibility and a wider scope of application. However, a number of questions arise when these methods are used to assess geometrically imperfect welded joints, such as joints with plate misalignments or excessive weld convexity or concavity. In these cases, the classical S‐N curves are known to cover imperfections up to the common tolerance classes for fatigue‐prone welded joints (e.g. in accordance with ISO 5817 class B). For the numerical methods, differing and conflicting recommendations exist on how to account for the geometric imperfections in the welded joints, with little or no background to these recommendations available. In this paper, a study is presented in which two standard welded joints (butt welds between plates of equal and unequal thickness; T‐joints with fillet welds) are analysed with the help of the structural hot‐spot and the effective notch stress approach. Various levels of geometric imperfection up to tolerance limits, and the resulting fatigue life predictions, are compared to the nominal stress approach predictions and the underlying test results from the literature. Since the nominal stress approach curves are based on reliable statistical data and desired survival probabilities for these known, standard cases, this methodology allows one to determine the correct application of the numerical methods to cases with geometric imperfections. This information may be used for a pertinent refinement of design recommendations for these methods, as well as for cases where these methods are applied to fitness‐for‐purpose assessments.
09.02: Effects of laser cutting on the cut‐edge properties of structural steel S355N subjected to high‐cycle fatigue
Authors: Zanon Gabriele , Bursi Oreste S. , Scardi Paolo , D'incau Mirco , Raso Sergio 
Published: September 2017

ABSTRACTLaser cutting is a relatively new technology in the steel structures field if compared with other process like welding. The complexity of physical mechanisms dominant the laser cutting process plays a fundamental role on the alteration of material properties of the heat affected zone and consequently on the structural response of elements subjected to high‐cycle fatigue applications. Moreover, in the last years an important evolution was observed in steel structures execution through the standard EN 1090 that introduced both the concept of execution class and minimum requirements for structural elements. The limitations of the local hardness HV10 on the cutting surface, imposed by the standard EN 1090 for high‐cycle fatigue applications, certainly is an important parameter but it is not enough to explain the behaviour of structural elements.The proposed study is focused on the investigation of correlations between relevant material properties altered by laser cutting process and the response of both material and structural joints subjected to high‐cycle fatigue loadings. In order to analyse the performances of the laser cutting we compared several properties of the cutting surface machined by mechanical and laser cutting. In detail, microstructures and material properties in terms of microhardness, hardness and residual stresses were investigated for steel elements of S355N. In addition, to correlate material properties and structural response, high‐cycle fatigue tests were carried out both on material test coupons and on structural details by elemental bolted connections. The main results observed through the tests confirm that specimens made with mechanical cutting exhibit a better behaviour than specimens treated with laser cutting, though all specimens satisfied EN1090‐2 requirements. The microstructures and material properties of laser cutting resulted to be favourable. Code requirements were also met for high‐cycle fatigue applications. More precisely, the fatigue category proposed by Eurocode 3 for drilled holes, i.e. FAT90, resulted to be adequate for realistic elemental bolted connections made with laser cut.
09.06: Continuous fatigue test of welded joint taken from SBHS700 girder specimen
Authors: Ono Yuki , kinoshita Koji , Ceballos Sean 
Published: September 2017

ABSTRACTSteels for bridge high performance structures (SBHS) have high strength, good weldability and workability. SBHS700 of 780MPa class must particularly clarify with respect to fatigue problems. At the previous study, the fatigue test with the SBHS700 girder specimen was carried out and fatigue strength improvement methods to introduce compressive residual stress were used on its out of plane gusset welded joints. However, the previous study did not quantitatively show the fatigue strength improvement because these out of plane gussets have not failed.In this study, in order to clarify the effects of the fatigue strength improvement methods, these out of plane gussets are taken from the girder by gas fusion cutting and made as small fatigue specimens. If there is enough compressive residual stress left at the weld toe, the fatigue tests are carried out.Before the fatigue tests, residual stress at 2mm from treatment edge of centre gusset was measured by the X‐ray diffraction method and compared with previous studies. The target of fatigue test was UIT (Ultrasonic impact treatment). At first, nominal stress range is 100MPa under the same condition of the previous study. If fatigue crack does not appear after 2 million cycles, nominal stress range is increased, such as 150MPa, 180MPa, 200MPa.As a result, enough compressive residual stress was confirmed at the weld toe from the X‐ray diffraction method. UIT specimens reached 2 million cycles in 200MPa stress range. Fatigue test results were considered based on an equation which modified Goodman's diagram applies to the weld toe due to estimate the fatigue limit. Therefore, high fatigue strength can be expected.
09.07: Observations on fracture toughness measurement: At the corners of G450 cold‐formed steel channel sections subjected to Tension
Authors: DIAS‐DA‐COSTA Daniel , PHAM Tien Dat , TU John , PHAM Cao Hung , HANCOCK Gregory J. , PROUST Gwenaelle 
Published: September 2017

ABSTRACTHigh strength G450 steel sheets are manufactured from hot‐rolled coil steel using a cold‐reduction process which involves cold‐rolling the steel under a series of rollers until a suitable thickness is achieved. Cold‐formed sections are subsequently manufactured by bending flat sheets at ambient temperature to achieve desired shapes. The plastic deformation associated with bending process results in strain hardening of the material and this in turn affects the properties. Due to the small difference between the yield point and tensile strength, fracture toughness becomes an important parameter in ultimate strength analysis as cold‐reduced steels are more brittle compared with hot‐rolled steels. Recent work to investigate the fracture behaviour of G450 sheet steels to AS1397 subjected to tension at ambient temperature (approximately 22°C) has been performed for different thicknesses (1.9, 2.4 and 3.0 mm). This paper describes the experimental investigation and observations of the corner effect on the fracture toughness of G450 steel. A series of six corner coupon tests of each thickness was cyclically loaded to produce a fatigue crack and then monotonically loaded in tension (ASTM E399) until fracture. A combined image processing technique was used to monitor the test from the two sides of the corner, where a grid of targets was initially marked at the surface and used for scaling and orientating all images. A digital correlation procedure was then applied to track the displacement of the tips of the notch of each crack and quantify the opening during the test. By correlating load with the different stages of propagation, the critical moments could be identified together with the fracture toughness. Results are thoroughly presented and discussed.
09.08: Structural behaviour of steel seismic links under strong cyclic loading
Authors: Papatheocharis Theocharis , Chatzopoulou Giannoula , Karamanos Spyros A. , Perdikaris Philip C. 
Published: September 2017

ABSTRACTThe work presented in this paper is part of an extensive European research project on horizontal seismic links subjected to strong full‐reversing cyclic loading. Both experimental testing and numerical simulations were conducted. The link specimens were subjected to combined shear and bending, representing the actual conditions acting on a seismic link during severe earthquake action. Large‐scale tests were performed under constant and increasing amplitude schemes, and parameters studied included steel material grade, length and cross‐section type of the link. The experimental setup employed consisted of a special two‐part steel loading frame that imposed on the steel link specimen a combined bending and shear type deformation. The experiments are supported by finite element model analysis. Three dimensional models have been employed for the simulation of the tests, and the numerical results agree well with the experimental results.
10.01: Analytical methods for the prediction of fire resistance of “reinforced” slim floor beams
Authors: Hanus François , Zaganelli Dario , Cajot Louis‐Guy , Braun Matthias 
Published: September 2017

ABSTRACTThe present paper describes a new analytical method for the prediction of temperature in longitudinal reinforcement bars of slim floor beams subjected to fire. This method is based on the isotherms of EN 1992‐1‐2 Annex A developed for concrete beams and slabs and is consequently applicable only to slim floor beams subjected to standard ISO fire curve. In addition to vertical heat fluxes, this method also considers 2D temperature field induced by the hot part of the beam web and by the lateral heating in case of long span composite flooring systems. An adaptation is proposed for reinforcement bars when situated close to the beam web.This new method leads to very good temperature predictions for R60, R90 and R120 fire resistance requirements. For less severe requirements, the reinforcement usually remains below 400°C and the resistance of hot‐rolled reinforcement bars is not reduced for this range of temperatures. The better predictions of the sagging bending moment of the section under ISO fire by use of this new method have also been demonstrated within the present paper.
10.06: Fire performance of CFS walls with web‐perforated studs–A numerical investigation
Authors: Xu Lei , Yang Shijun , Cui Jia 
Published: September 2017

ABSTRACTPresented in this paper is a study on the performance of load‐bearing cold‐formed steel (CFS) walls with web‐perforated studs subjected to standard fire evaluated with use of sequentially uncoupled 3D finite element (FE) thermal‐stress analysis. The walls are sheathed with double layers of MgO board, Type C gypsum board, or mixed Type X and MgO board. The predicted failure times obtained from finite element analysis (FEA) are compared with those of full‐scale fire tests of load‐bearing CFS walls. The FEA results indicate that simulating CFS wall fire tests using a single stud model is acceptable. The difference between failure times predicted by the single stud model and fire tests is not significant. To account for possible force and stiffness interactions among the wall studs, modelling the load‐bearing fire wall tests using a CFS wall frame to obtain the system‐level response is also discussed. The FEA results obtained from the CFS wall frame model indicate that the middle interior studs may experience considerably higher loads than that applied to an equivalent single stud model. Consequently, the single stud model may overestimate failure time. Thus, interactions among the CFS wall studs should be considered in FEA to evaluate the performance of the wall system in fire.
10.08: Application of advanced materials for enhancing the fire performance of slim‐floors
Authors: Espinós Ana , Albero Vicente , Romero Manuel L. , Hospitaler Antonio , Ibáñez Carmen 
Published: September 2017

ABSTRACTComposite steel‐concrete beams embedded in floors (slim‐floors) are increasingly used in new construction proposals for residential, industrial and commercial floors, which motivates the need for assessing their fire behaviour. However, EN 1994‐1‐2 does not provide simplified methods to obtain the temperature distribution in the cross‐section, which is available for other types of composite solutions such as partially encased composite beams. As a consequence, this paper presents an advanced finite element thermal model to evaluate the temperature distribution in slim‐floors, calibrated against tests from bibliography, specifically for commercially available slim‐floor configurations such as Shallow Floor Beams (SFB). This thermal model will help to assess the fire behaviour of slim‐floors.Additionally, the usage of advanced materials such as High Strength Steel (HSS), and lightweight concrete for slim‐floors is evaluated through the developed finite element thermal model, in order to provide design recommendations on the most favourable configurations. This paper presents a first approach to evaluate the benefits of the application of these innovative materials to slim‐floors.
10.09: Critical temperatures of members with class 4 cross‐section
Authors: Maia Élio , Couto Carlos , Real Paulo Vila , Lopes Nuno 
Published: September 2017

ABSTRACTThis paper describes a numerical investigation on the critical temperatures of members with Class 4 cross‐sections according to Eurocode 3 design. For such sections, the norm suggests the use of a default critical temperature of 350 °C irrespective of the load level conditions if no other calculation is made. On that regard, the authors have previously demonstrated that this temperature might be too conservative for certain conditions, especially if different degrees of utilization are taken into account. As a consequence, the authors recommended and validated new default critical temperatures for Class 4 cross‐sections subjected to compression and bending about the major axis, for different reduction factors for the design load level under fire conditions.Building up on said studies regarding slender cross‐sections, the present work aims at extending and establishing the groundwork for future studies on the critical temperature of members subjected to fire with the ultimate goal of achieving and validating a wide‐reaching proposal of more appropriate default critical temperatures for steel members and cross‐sections subjected to fire.From this study it was observed that the critical temperatures for laterally restrained members (in‐plane) are in agreement with those proposed in previous research by the authors. The out‐of‐plane simulations, however, displayed similar patterns to those of their in‐plane counterparts up until a certain slenderness threshold, after which a noticeable loss of resistance seems to occur, likely due to the higher influence of second‐order effects in the out‐of‐plane direction.
10.10: Influence of beam‐end buckling on adjacent beam‐column connections in fire
Authors: Quan Guan , Huang Shan‐Shan , Burgess Ian 
Published: September 2017

ABSTRACTAn analytical model to simulate the beam‐end buckling phenomenon, which occurs particularly in the fire context, has been developed. In this research, a component‐based beam‐end buckling element has for the first time been created for beams of Classes 1 and 2. The component‐based buckling element is composed of nonlinear springs, which can deal with loading‐unloading‐reloading paths. A significant challenge is to enable the flange‐buckling component to deal with a descending post‐buckling path simultaneously with deformation‐reversal, because more than one solution can be found at a single force level in the solution process. The buckling element has been implemented in the structural fire engineering software Vulcan, so that it can be used adjacent to existing connection elements in frame modelling. The effects of the buckling element have been investigated in frame analysis using Vulcan. It has been shown that, in most cases, the stresses within the connection's bolt rows tend to decrease when the buckling element is taken into consideration. By ignoring the buckling element near to the beam‐to‐column connections in structural fire analysis, the results tend to be on the safe side regarding the connection forces.