bluuebunny/crossref_metadata_2025 huggingface dataset:
07.31: Fire performance of LSF walls with web stiffened channel sections using finite element analysis
Authors: Dias Yomal , Keerthan Poologanathan , Mahendran Mahen
Published: September 2017

Light‐gauge steel framed (LSF) walls with plasterboard lining are increasingly used in modern building construction due to their numerous advantages. Their fire performance has been investigated using both numerical and experimental studies in the past for lipped channel section (LCS) and welded hollow flange section (HFC) studs. A new riveted HFC stud was also considered. However, no attempt was made to use a structurally and economically optimum stud section in the wall configurations. This paper investigates the fire performance of a new stiffened channel section (SCS) as LSF wall studs. The proposed section succeeds in delaying both local and distortional buckling modes. At ambient temperature, the member compression capacity of each stud section, normalized to its squash capacity, was used to compare the performance of the three sections. It was found that the performance of SCS is equivalent to the LSB and superior to the LCS. The fire performance of LSF wall studs made of LCS, LSB, and the proposed section has also been assessed for three common wall configurations using finite element (FE) analyses. The walls were exposed to the standard ISO 834‐1 fire curve on one side. Stud time‐temperature profiles were developed for the three wall configurations using finite element thermal analyses and validated using available full‐scale fire test data. Fire Resistance Levels (FRL) of load bearing and non‐load bearing walls were determined and validated using previous experimental and numerical results. For the same load ratio, the three stud sections perform similarly, giving close FRL values for each of the configurations considered. Due to the elimination of the necessity for welding or riveting, it is proposed that SCS is used to develop structurally and economically optimum LSF walls compared to those made using LCS and welded or riveted HFC sections. FRL versus Load Ratio curves were developed for the full range of load ratio using both steady and transient state FE analyses. Using them, the susceptibility of cavity insulated, non‐load bearing LSF walls to failure due to structural inadequacy was also identified.
07.36: Strength of combined sigma cold formed section columns
Authors: Aghoury M. El. , Hanna M.T. , Amoush E.A.
Published: September 2017

The high strength‐to‐weight ratios of cold‐formed steel framing systems make them competitive in modern construction markets. Generally, Cold‐formed steel sections are shaped to suit the particular application. Lipped channel sections are the most used sections, however, sigma sections need more effort in fabrication but they have high strength‐weight ratios compared with the lipped channel sections. In this paper, the strength of pined‐pined columns composed of combined back to back sigma cold formed sections is studied numerically by a non‐linear finite element analysis. Four nodes isoparametric shell element that allows both geometric and material non‐linarites is used. The effect of geometric imperfections is included in the model. The boundary conditions considered allow the columns ends to rotate about the major and minor axis. The parameters studied include, the cross section proportions such as the flange, web, and lip dimensions as well as the connectors spacing. The two sections are assumed to be connected through their webs. Further, several columns heights are considered to study the different modes of failure. The numerical model is validated by experimental study carried out by the authors. Findings reflect that sectional (local/distortional) buckling governs the failure shape of short columns. Finally, the results have been compared with the predicted strengths determined by the Eurocode‐3 and the American specifications (AISI, DSM).
08.05: Design of high strength concrete filled tubular columns
Authors: Liew J Y Richard , Xiong Mingxiang , Wang Yan‐Bo
Published: September 2017

This article is not available for publication.
08.14: Behaviour of innovative demountable shear connectors subjected to combined shear and axial tension
Authors: Varsani Harshad , Tan Ee Loon , Singh Balbir
Published: September 2017

Composite steel‐concrete beams are being used increasingly in construction due to its benefits over beams consisting of the steel component alone. Composite steel‐concrete beams comprise of a steel component which is under tension and a concrete component which is under compression. Shear connectors at the steel‐concrete interface connect the two components together as well as resist shear forces. However, in some applications such as in composite coupling beams and infill walls, these shear connectors have to resist uplift forces in addition to shear forces. Therefore, there is a need to carry out experimental testing to investigate the performance of shear connectors under combined loading. Furthermore, the steel and concrete components of a composite beam cannot be separated without destroying the components since the shear connectors are welded to the steel beam and embedded in concrete. If the steel is to be reused, it has to be remelted which requires energy that usually comes from unsustainable sources. Hence research has been carried out on demountable shear connectors as they allow demounting and easy separation of the steel and concrete components. The performance of three types of innovative shear connectors subjected to combined shear and tensile loading was investigated experimentally. A pull‐out test was first being carried out with each type of shear connector to determine the tensile capacity of each type of shear connector. This was then followed by a series of modified push tests that were carried out to determine the interaction between shear and tension loading on each type of shear connector. Tensile capacity which had been determined from pull‐out tests was applied in increments of 25 % to each group followed by shear loading until failure of the shear connector was observed. A comparison of the results was carried out with shear‐tension relationships for traditional headed studs proposed by other researchers. Based on the experiment investigation carried out, significant reduction in shear strength was observed when tensile force was applied. Demountable headed studs had a much higher ductility than AJAX Oneside and Hollo bolts.
08.17: Experimental behaviour of high‐strength thin‐walled concrete filled steel tubular stub columns
Authors: Lume Gavin , Rasmussen Kim J. R. , Tao Zhong , Han Lin‐Hai
Published: September 2017

Developed more than 80 years ago, the design procedure of concrete filled steel tubes (CFST) has several limitations that can still be found in most current international design standards. The two main limitations that present themselves are the lack of ability to achieve material enhancement when using high strength materials and restrictions on the geometry of the steel tube thickness to the overall column diameter. This geometric limitation is placed on the design to ensure that the steel tube remains ‘compact’. In complying with these constraints it is assumed in the design equations that local buckling of the steel tube will not take place before the ultimate global buckling load is achieved.

With the introduction of higher strength materials, specifically when dealing with steel, the strength increase leads to the design of sections with increased slenderness. As the section becomes more slender, the ability to maintain the compact section limitations in the design codes becomes increasingly difficult. This paper looks at an experimental study on very thin‐walled steel tubes filled with high‐strength concrete and how localised buckling affects their compressive capacity.

Adopting a diameter to thickness ratio of 200, 24 circular tubes were constructed using a high‐strength cold‐formed steel sheet, with yield stresses above 500MPa and filled with 100MPa concrete. Employing both thin‐walled sections and high strength materials, the effects of localised buckling in these composite members when subjected to compression has been studied. The experimental programme explored four main conditions; when both the steel and concrete were loaded and bonded together, when the concrete core inside the CFST was loaded, when the steel tube in the CFST was loaded and when the concrete core without the steel tube was tested.

By studying the failure modes of both the concrete and the steel tube when acting compositely and individually, the experimental work shows that there is valid evidence to support the theory that even when using high strength materials in slender sections, confinement to the concrete core is provided. Finally, the results of the experimental work have been compared to the compressive design capacities predicted by current international design codes, showing that these provisions are conservative.
08.18: Influence of composite beams on the seismic behaviour of EBF
Authors: Vătăman Adina , Ciutina Adrian , Grecea Daniel
Published: September 2017

The Eccentrically Braced Frames (EBF) represents a structural typology largely used in case of steel structures located in seismic zones due to their possibility to dissipate the seismic input energy through plastic hinges formed in the dissipative “link” element. In case of seismic‐resistant eccentrically braced frames with composite beams, the current design practice suggests avoiding the disposition of shear connectors in the expected plastic areas, thus taking into consideration shear plastic hinges that occur only in the steel beam or link element. The existing experimental results show however that this consideration is not realistic, as the behaviour of full‐composite beam with connectors disposed over the link is closer to the case in which the beam is disconnected over the link element as suggested by the modern seismic norms: the response characteristics (resistance, stiffness and ductility) of composite beams with or without connection over the link length are very in fact close and different from the case of pure steel link element.

The paper presents the results of a parametrical numerical study based on experimental results, with the main purpose of investigating the extent of the composite behaviour of EBFs with short links subjected to lateral seismic loads.
08.22: Axially compressive behaviours of steel tubes filled with post‐pouring concrete and precast segments containing DCLs and FC
Authors: WU Bo , PENG Chengwei
Published: September 2017

To improve the construction efficiency of steel tubes filled with demolished concrete lumps (DCLs) and fresh concrete (FC) at construction site, a new fabrication method is proposed in this paper, and the axially compressive behaviours of four columns prepared using this method have been experimentally investigated and compared with those of the control column. According to the proposed fabrication method, the segments containing DCLs and FC are precast first, and then are placed into the steel tube. Finally, post‐pouring concrete is employed to fill the space between the steel tube and precast segments. In this way, the processing of DCLs is not involved at the construction site, and thus the efficiency of construction can be enhanced significantly. The parameters considered in the compressive tests included the number of the precast segments in the steel tube (S1=one segment, S2=two segments, and S3=three segments), and the cross‐sectional dimensions of the precast segment (C1=331 mm×331 mm, and C2=303 mm×303 mm). The outer diameter and thickness of the steel tubes were, respectively, 500 mm and 5.7 mm. The 150 mm cubic compressive strength of the post‐pouring concrete was 32.8 MPa. The replacement ratio of DCLs in the precast segments was 40%, and the 150 mm cubic compressive strengths of the demolished concrete and fresh concrete used in the precast segments were 31.5 MPa and 47.4 MPa, respectively. The control column was a steel tube filled with DCLs and the post‐pouring concrete simultaneously. The five columns had the same height as 1800 mm, and the weight of DCLs adopted in the control column was the same as that employed in other four columns. In this paper, failure patterns of the five specimens are presented, and influences of the aforementioned parameters on the specimens’ axially compressive behaviours have been discussed. It is found that the columns prepared using the new fabrication method have similar failure modes as compared with the control column, and the number and sectional size of the precast segments have different impacts on the column's axially compressive performance.
08.23: Performance and design of shear‐keys in hybid RC beam and steel column systems
Authors: Moharram Moustafa I. , Bompa Dan V. , Elghazouli Ahmed Y.
Published: September 2017

This study describes experimental and numerical investigations into the inelastic performance of hybrid structural configurations consisting of reinforced concrete (RC) beams connected to steel columns by means of fully‐embedded structural steel profiles (shear‐keys). Experimental observations from a series of fourteen full‐scale hybrid steel/RC specimens are presented. To provide further insights into the key response characteristics, detailed numerical analyses for the tested configurations are also carried out. The numerical studies are undertaken using nonlinear finite element procedures which are validated against the experimental results from the hybrid tests presented in this paper. The ability of the numerical models to provide faithful predictions, using a consistent set of material parameters, provides a high level of confidence in the reliability of the simulation techniques. Data from the numerical models are then sutilised to evaluate the shear‐force distribution along the length of the shear‐key. The contribution from the shear‐key to the overall vertical force transferred to the column is comparatively assessed amongst the various configurations presented. For more simplified design considerations, an idealised distribution of the effective shear forces along the shear‐key is also proposed in the current study. Bases on the findings, recommendations for the practical design of shear‐keys in hybrid specimens are suggested and discussed.
08.28: Push out tests of a novel shear connection mechanism for use in demountable precast composite beams
Authors: Feidaki Eliza , Vasdravellis George
Published: September 2017

The production of steel and concrete is responsible for the 15% of CO2 emissions worldwide, whereas demolition of buildings produces a significant amount of waste that goes to landfill. Steel‐concrete composite floors are currently constructed using a monolithic connection between the concrete slab and the shear studs. This practice makes the deconstruction of composite floors problematic. More sustainable solutions can be achieved by developing composite floor systems that offer the advantages of easy and rapid deconstruction and reuse of structural components. This paper presents a novel steel‐concrete composite floor system using precast hollow‐core slabs and a demountable yielding shear connection mechanism. Horizontal pushout tests were performed aiming at: a) studying the physical behaviour of the proposed shear connection; and b) evaluating the construction and deconstruction procedures by disassembling and reassembling one push out specimen. The experimental results showed that increased ductility and strength can be achieved by altering the geometrical characteristics of the yielding mechanism. All the component parts of the connection were undamaged and reusable apart from the yielding mechanism. Numerical models for push out tests were created using the Abaqus software. Comparison of the experimental with the numerical solution showed that the strength of the steel yielding mechanism can be reasonably predicted.
08.41: Renewal method for aged steel bridges with polymer cement mortar
Authors: Taniguchi Nozomu , Satake Shinya , Lin Weiwei , Hiroe Masaaki , Kubo Takeaki
Published: September 2017

This research offers a new composite‐revamping method for railway bridges by assuming composite remodelling process of existing steel bridges having no specific fissure damages or serious corrosions and effectively making use of relatively new materials to it. Effects of noise reduction and improved stiffness were further confirmed through Impact tests (vibration and noise measurement tests) in order to prove the efficacy of the composite remodelling. By the tests, it can be confirmed that the composite structuring work tended to reduce the vibration level by around 10 to 35 dB and the all pass (AP) value by about 30 dB. In addition, the stiffness increases from the bridges of only steel members. The remainder life of the structure is extended by this effect. These effects are confirmed by the experiments for railway bridges.
08.46: Local buckling of thin‐walled tubes encased in concrete
Authors: Albareda‐Valls Albert , Carreras Jordi Maristany , Carrera David Garcia
Published: September 2017

Local 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

The 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

This 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

The 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

The 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

Laser 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

Steels 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

High 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

The 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

The 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

Presented 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

Composite 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

This 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

An 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.
10.12: Numerical modelling of steel sheathed LSF walls under fire conditions
Authors: Dias Yomal , Keerthan Poologanathan , Mahendran Mahen
Published: September 2017

Fire performance of light gauge steel framed (LSF) walls sheathed with gypsum plasterboards has been investigated using experimental and numerical studies by many researchers in the past. Provision of cavity or external insulation, improving the thermal‐mechanical properties of plasterboard, and changing the stud geometry are several options previously employed to enhance the Fire Resistance Level (FRL) of such wall systems. Past studies of steel sheathed cold‐formed steel (CFS) framed walls have shown that the use of steel sheathing improves the shear strength of LSF walls. However, such studies have not investigated the possible improvements to the fire performance of LSF walls due to the use of steel sheathing in addition to plasterboards. This numerical study investigates the thermal performance of three common LSF wall configurations sheathed with steel sheets on both sides under fire conditions. Three steel sheathing configurations (internal and/or external sheathing) were considered for each LSF wall. Thermal Finite Element (FE) models were developed and used to simulate the heat progression across the walls, following validation using previous experimental studies. The walls were exposed to ISO 834‐1 standard fire curve on one side. Results were then compared with those from LSF walls sheathed only with plasterboards. Internal steel sheathing was found to be capable of reducing the ambient side temperatures compared to plasterboard only walls due to the lower emissivity of steel, whereas external steel sheathing increased them further. Although the stud hot flange (HF) temperatures are generally increased with the addition of steel sheets, provision of back‐blocking was able to eliminate this deficiency. A novel arrangement is proposed for back‐blocking which is found to significantly delay the stud temperature rise and improve the FRL. The use of corrugated steel sheet profiles is found to reduce both the stud and ambient side plasterboard temperatures. The results from this study give useful information to develop load bearing and non‐load bearing LSF walls with superior fire performance. This paper presents the details of this numerical study and the results.
10.15: Thermal modelling of LSF floor systems made of lipped channel and hollow flange channel section joists
Authors: Steau Edward , Keerthan Poologanathan , Mahendran Mahen
Published: September 2017

Buildings that are not designed to have fire safety measures are not able to endure the extreme conditions in a fire event. Hence considerably more attention is being placed on the fire safety of buildings in recent times. Light gauge steel framed (LSF) floor systems are commonly used in buildings as they provide significant benefit by reducing weight and cost while increasing construction efficiencies. To obtain a satisfactory fire resistance level, floor systems must comply with a number of requirements specified in codes relating to fire resistance level. However, to understand the heat transfer process within LSF floor systems usually requires numerous complex fire tests. These tests are extremely expensive and time consuming. Therefore three‐dimensional finite element models were developed and used in this study to investigate the heat transfer in LSF floor systems made of different joist sections such as Lipped Channel and Hollow Flange Channel beam sections. Standard fire curve was defined as an amplitude curve following a time‐temperature profile based on ISO 834 standard fire curve. The time‐temperature curves obtained from the finite element analyses were compared with available experimental results to determine their accuracy in predicting the heat transfer in LSF floor systems made of the two chosen joist sections. Results showed that the proposed three‐dimensional finite element models can accurately predict the heat transfer of LSF floor systems made with lipped channel and hollow flange channel section joists. They also highlighted the differences in the thermal performance when different joist types are used. This paper presents the details of a three‐dimensional thermal modelling study of LSF floor systems made of lipped Channel and hollow flange channel section joists and the results. Innovative LSF floor systems were also proposed using the validated thermal models to enhance the fire resistant rating.
10.21: Post‐fire response of slender concrete‐filled steel tubular columns
Authors: Ibañez Carmen , Albero Vicente , Espinos Ana , Romero Manuel L. , Hospitaler Antonio
Published: September 2017

In this paper, a fiber beam model for the simulation of the post‐fire response of slender concrete‐filled steel tubular (CFST) columns is presented. First, the model is validated against experimental results and subsequently it is employed to analyse the post‐fire response of circular CFST columns. Actually, when a fire takes place in a building, the columns are supporting load even while the fire is being extinguished. For that reason, it is important to take into account this loading condition when trying to predict their post‐fire behaviour. Therefore, in this research, the analysis is initiated when a constant load is applied to the column and, simultaneously, the specimen starts to be heated following an established heating regime (ISO 834). Maintaining the applied load constant, the cooling stage prolongs until the column reaches the room temperature. The post‐fire response of the CFST columns is studied by means of a mechanical analysis where the applied load increases progressively up to the column failure. The model considers realistic features typical from the fire response of CFST columns, such as the existence of a gap conductance at the steel‐concrete interface or the sliding and separation between the steel tube and the concrete. Finally, the post‐fire response of CFST columns is studied in depth taking as reference experimental results used in validation. The variation of the residual strength with load level for realistic fire resistance times is calculated and analysed.
10.27: Contribution from the flanges to the shear buckling resistance of steel plate girders at normal and elevated temperatures
Authors: Reis André , Lopes Nuno , Real Paulo Vila
Published: September 2017

This article is not available for publication.
10.32: Experimental study on high temperature elastic modulus of China made high strength structural steel
Authors: Li Guo‐Qiang , Huang Lei , Zhang Chao
Published: September 2017

High strength structural steel (HSSS) has better economic and environmental benefits than mild structural steel, and becomes more popular in the building construction projects. The current codes for fire safety design of steel structures is mainly developed based on the test data from mild structural steel and might be not applicable to the high strength structural steel. This paper reports an experimental study on the high temperature elastic modulus of China made high strength structural steel. Both static and dynamic test methods were used to determine the elastic modulus of Q550, Q690 and Q890 China grade steel at temperatures ranging from 20 °C to 800 °C. Suspended coupling bending resonance method was used to measure the dynamic elastic modulus. The reduction factors of elastic modulus from test data were compared with the reduction factors determined by current codes, including the Chinese code CECS200, the Eurocode 3, the American code AISC and the Austrian code AS4100, and by other researchers. The study found that unlike the static reduction factors (reduction factors determined by the static method) the dynamic reduction factors are not sensitive to the steel grade. The static elastic modulus is greater than the dynamic elastic modulus at low temperatures and is less than the dynamic modulus at high temperatures. Both the static and dynamic reduction factors of HSSS are greater than the elastic modulus reduction factors employed by the current codes. Design equation for dynamic elastic modulus of HSSS was derived from curve‐fitting of the test data.