bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhancing Oxygen Storage Capability and Catalytic Activity of Lanthanum Oxysulfide (La2O2S) Nanocatalysts by Sodium and Iron/Sodium Doping
Authors: Tan Shuai , Li Dongmei
Published: September 2017

We report the enhanced oxygen storage capability (OSC) and activity of lanthanum oxysulfide (La2O2S) nanocatalysts, derived from the introduction of oxygen vacancies by sodium (Na) doping. Additionally, iron/sodium (Fe/Na) co‐doping further increased the OSC by three times, with an additional 15–20 % increase in CO conversion for the water‐gas shift (WGS) reaction, compared with the best CO conversion rate among Na‐doped La2O2S catalysts. The significant enhancement in OSC and activity after Fe/Na co‐doping may be attributed to the presence of Fe2+↔Fe3+ redox couple. Finally, the Fe/Na co‐doped nanocatalyst alleviated the high temperature requirement of La2O2S catalysts without compromising stability.
Hydrogen/Deuterium‐Exchange Reactions of Methane with Aromatics and Cyclohexane Catalyzed by a Nanoscopic Aluminum Chlorofluoride
Authors: Calvo Beatriz , Braun Thomas , Kemnitz Erhard
Published: September 2017

H/D‐exchange reactions between methane and deuterated solvents such as [D6]benzene and [D12]cyclohexane were heterogeneously catalyzed by nanoscopic aluminum chlorofluoride (ACF=AlClxF3−x, x≈0.05–0.3) under very mild conditions. 13C NMR spectroscopy experiments at labeled methane revealed the formation of all isotopologues. AlCl3, AlBr3, HS‐AlF3, γ‐Al2O3, and γ‐Al2O3 preheated at 700 °C did not show any H/D‐exchange reaction of methane or [D6]benzene. Mechanistically, electrophilic activation of methane was suggested at the ACF surface.
03.15: Experimental tests and model study on self‐drilling screws connections subjected to shear
Authors: Gryniewicz Marcin , Szlendak Jerzy Kazimierz
Published: September 2017

Research on shear resistance of the steel sheeting plates with thickness from 0,50 to 1,50 mm connected by self‐drilling screws is undertaken and presented in this paper. One screw type with one diameter has been used. This kind of the single lap fastening is commonly used in a steel sheeting. Experimental and theoretical data about a connections slip and shear stiffness is a one of most important issue in case of a stressed skin diaphragm action problems. At the present practice the linear model of connections is effectively used however for more advanced analyses, the non‐linear models have to be taken into consideration. These are necessary in case of the advanced design and implementation of the stressed skin action in the steel structures covered by the corrugated metal sheeting. Such a model study is presented herein which intend to investigate the general connection behaviour where the main selected variable is the plate thickness. The test are performed according to the current standards EN 1990 and ECCS handbooks. It leads to a statistical evaluation of proposed functions for the design slip of fasteners and its limits. The theoretical basis of experimental tests under the shear load is presented.
03.17: Design of haunches in structural steel joints
Authors: Kurejková Marta , Wald František , Šabatka Lubomír , Kabeláč Jaromír
Published: September 2017

The paper presents research into the advanced design of stiffeners in structural steel joints. Experimental results of six specimens of haunches with and without flanges are presented. Three specimens are without flanges and three specimens are supported by additional flanges. Flanges differ in stiffness to observe the increase of haunch resistances and its effect on buckling shapes.

Haunches with and without flanges are validated by numerical model to tests and resistances are calculated and evaluated. The research finite element model (RFEM) is studied by material and geometrical nonlinear finite element analysis with imperfections under the actual stress conditions and validated on the measured experimental data. The quality of prediction is demonstrated on the comparison of load‐deflection curves and failure modes. The stability analysis of a joint with a haunch is used for design Component Based Finite Element Models (CBFEM) of complex joints. RFEM allows verifying the design FEM model (DFEM) and component based FEM model (CBFEM) developed for the design of complex joints in steel structures. To avoid local buckling of slender plates in CBFEM a design procedure is proposed and verified on research finite element model (RFEM). It is proposed to use a combination of material nonlinear analysis without imperfections with buckling analysis in CBFEM. The verification is shown on an example of a haunch in a welded portal frame joint. The stiffener is studied by numerical analysis, resistances and critical loads are determined in RFEM and CBFEM and results are compared. A numerical study illustrates the effect of the haunch's thickness on the joint's resistance.
03.20: Experimental tests on beam‐end connectors of cold‐formed steel storage pallet racks
Authors: Giordano Saverio , Gusella Federico , Lavacchini Giovanni , Orlando Maurizio , Spinelli Paolo
Published: September 2017

The key role of beam‐column joints in the seismic response of moment resisting frames (MRF) has been fully recognized. In the performance‐based seismic design of steel storage pallet racks, many researches have highlighted the need to take into account the inelastic response of beam‐column joints. Pallet racks are characterized by boltless beam‐column connections and the extensive use of thin‐walled cold‐formed steel members. Due to the great number of beam‐end connector types and member geometries, specific tests are required to evaluate the structural behavior of these structures. In particular, their seismic analysis requires a thorough modeling of the behavior of beam‐column joints, which has been investigated by the authors through experimental tests under monotonic and cyclic loads. Tested connectors have exhibited different values of the bending stiffness and the ultimate bending moment, depending on structural details of each joint's type, like the number of tabs. Cyclic tests have shown a pinching in the hysteresis curve, underlining that the cyclic response of tested joints is significantly different from joints of traditional steel framed buildings. Experimental results confirmed the importance of cyclic tests on beam‐end connectors to correctly identify their moment‐rotation curve, which is required to perform reliable seismic analyses of steel pallet racks.
03.30: Connection classification for a space structure jointing system
Authors: Chenaghlou Mohammad Reza , Hamed Arash Akbari
Published: September 2017

A crucial consideration in the analysis of space structures is the decision of how the connections are to be modelled. This depends on the configuration and dimensions of the structure to be analysed as well as the material and the type of connections employed. A number of attempts for connection classification have been reported and among these two classification systems i.e. classification system in Eurocode 3 and classification system by Bjorhovde et al. have received more attention. These two classification systems have been developed for beam‐to‐column connections. In order to appraise the two classification systems for a space structure jointing system, a parametric study has been carried out on the effects of connections on compression member behaviour. Based on the obtained results, a methodology for the classification of connections in space structures has been proposed. The proposed classification method uses floating boundaries that give more flexibility to the classification.
04.03: Buckling behaviour of axially compressed cylindrical shells made of stainless steel
Authors: Gorbachov Anna , Stranghöner Natalie , Rotter J. Michael
Published: September 2017

Cylindrical shells made of stainless steels are widely used, e.g. in tanks and biogas plants [1]. Whereas austenitic stainless steels were commonly used in the past, austenitic‐ferritic and lean duplex stainless steels are more frequently used nowadays. By contrast with structural steels, stainless steels exhibit a significantly nonlinear stress‐strain behaviour which must be considered in the buckling analysis of these shells because the reduced material stiffness below the proof stress may cause premature buckling. For this reason, EN 1993‐1‐6 [2] indicates the use of either a reduced value of elastic modulus Ered or the secant modulus at the 0.2% proof stress when assessing the buckling resistance of shells with nonlinear stress‐strain curves. These provisions may produce over‐conservative low buckling strengths for stainless steel shells at both low and high slendernesses. Only stainless steel shells with medium slenderness are covered by this rule.

For this reason, additional temperature‐ and slenderness‐dependent buckling strength correction factors for austenitic stainless steel axially loaded cylindrical shells were developed by Hautala and Schmidt (1999) [3,4] which were described in the ECCS Design Recommendations [5] for buckling of steel shells but are not yet implemented into EN 1993‐1‐6. Recent experimental, numerical and theoretical research, carried out within the European RFCS research project BiogaSS on austenitic‐ferritic and ferritic stainless steels has investigated the potential to apply these buckling strength correction factors to austenitic‐ferritic and ferritic stainless steels. This paper shows that shells made of austenitic‐ferritic and ferritic stainless steels have a less serious deviation from the reference mild steel than austenitic stainless steel, permitting less significant buckling strength correction factors.

The results obtained for all families of stainless steels should be transformed into the generalized design verification format of EN 1993‐1‐6, in which a parameterized capacity curve [6,7] is used. This paper also shows how the correction factors devised for axially loaded shells made of austenitic stainless steel can be better represented by an appropriate characterisation using the capacity curve alone. The outcome should be relevant to austenitic, austenitic‐ferritic and ferritic stainless steels when sufficient data is available. The paper also illustrates how behaviours of considerable complexity in some shell buckling situations can still be represented by the unaltered universal capacity curve [6,8].
04.05: Analysis type influence on the durability prognosis for a steel tank corroded shell
Authors: Maslak Mariusz , Pazdanowski Michal , Siudut Janusz , Tarsa Krzysztof
Published: September 2017

An original approach to the evaluation of remaining service time of a corroded on the ground steel shell of a tank used to store liquid petroleum products is presented and discussed. A typical steel tank equipped with floating roof is analysed. The limit state for such structure is determined by the tensile hoop stress at the completely filled tank reaching the bearing capacity of steel plating. It is assumed, that in the foreseeable future the tank will not be modernized nor strengthened in any manner. The service mode of the tank will not change as well. The future progress of corrosion is forecast by the extrapolation of trends, which have appeared until now, and identified during the cyclical obligatory examinations of the tank technical condition. Detailed map of the corrosion reach and intensity determined in this way is superimposed over the numerical tank model, replicating its real imperfect geometry measured by geodetic methods. In this paper two alternative methods of analysis are compared. The first one is geometrically nonlinear (GNA), while the second one is geometrically linear (LA). The obtained results are compared with the analogous results obtained under the assumption of perfect tank geometry. It turns out that the quantitative differences with respect to the forecast tank shell life, due only to the numerical approach recommended for analysis, are substantially bigger than those generated by monotonically progressing, but locally varying corrosion progress. In the case considered in this paper, the linear analysis (LA) yields the most restrictive estimate of authoritative hoop stresses. The application of nonlinear analysis (GNA) proves to be the less restrictive approach in this field, as it takes into the account the smoothing of possible local folds in the deformed shell, and thus as a consequence making it closer to the shell with perfect geometry.
04.07: On the axial buckling of very thin‐walled cylindrical shells
Authors: Jäger‐Cañás Andreas , Pasternak Hartmut
Published: September 2017

Major advances in the buckling analysis of cylindrical shells have been achieved in the last two decades. Eurocode nowadays provides rules for tanks up to r/t = 5000. However, since only few literature has become available in the past, dealing specifically with very thin walled shells in the range between r/t = 1500 and r/t = 10000, code provisions either are quite conservative or, in case of r/t > 5000, do barely exist. Employing modern construction methods, close‐to perfect, very thin‐walled shells can be built that are out of the scope of the design codes. Therefore, to achieve more economical designs and a better sustainability, sophisticated design tools have to be used.

In this paper, modifications and extensions of the current design procedure are proposed to overcome current limitations and drawbacks. A review of experiments with a special focus on cylinders with high r/t‐ratios was conducted and modified lower bound approximation curves for the knock‐down factor α deduced. They were checked against representative experiments from literature. Test results recalculated using an axisymmetric imperfection to explore their equivalent imperfection depth, proved that even small imperfections drastically reduce the buckling strength. Using a parametric study, the result range of α was extended up to r/t = 10000. The design proposal could be approved and an equation for the determination of an equivalent imperfection depth that relates the dependence of α to the imperfection depth and the r/t‐ratio is proposed.
05.01: Lattice girders with I‐sections and slotted gusset plates: Load carrying behaviour and ultimate capacity of compression members based on full scale girder tests
Authors: Unterweger Harald , Kampleitner Andreas
Published: September 2017

Nowadays trusses are often designed with I‐sections only and no direct connection between the diagonal members and the chords. For the truss joints, gusset plates – welded to the chords – are used, which are slotted for the welding connection to the diagonal member.

The main focus of the paper is the specific stability behaviour of such diagonal members in compression, leading to an interaction behaviour of member buckling out of plane and local buckling of the gusset plates. Within a comprehensive study a lot of different compression members and joint configurations were studied in detail, based on nonlinear numerical analyses.

The results of four full scale tests on a lattice girder are presented in detail. In the four tests different I‐sections with different gusset plate geometries were investigated. The most interesting fact is the comparison of the load carrying behaviour of the compressed diagonal members with increasing free length of the gusset plates. The member capacity of the tests is compared with the numerical results of a FE‐model, considering the measured geometric imperfections and the measured material parameters.

The overall load carrying behaviour of the truss in the test is analysed and compared with simplified models for global analyses, both for the load – deformation behaviour and for the relationship between load and member axial force.

Finally a simple design model for the prediction of the ultimate capacity of the compression members is presented, which consists of a buckling verification based on the equivalent member with increased buckling length (section capacity near midspan is verified) and of an additional verification of the section capacity of the gusset plate. For the latter one the interaction of local and global buckling effect is important, leading to a simplified engineering model with all the relevant sources of geometric imperfections considered. It ends up with a check of the section capacity of the gusset plate, based on 2nd order internal forces (N&M). For slender gusset plates and also diagonal members with small slenderness, the section capacity of the gusset plates limits the load carrying capacity of the member and the buckling verification of the equivalent member may be on the unsafe side.
05.04: Combined loading of slender stainless steel SHS/RHS members
Authors: Židlický Břetislav , Jandera Michal
Published: September 2017

The presented research shows behaviour of slender stainless steel members loaded by compression and bending which is demonstrated on square and rectangular hollow sections (SHS/RHS) made of austenitic stainless steel. An initial numerical parametric study in FE software Abaqus is given and its results are compared to the existing design procedures and design standard rules. The investigated parameters are mainly the column slenderness, section slenderness, ratio between the applied bending moment and the axial compressive force. The necessity of having additional design rules for stainless steels is firstly demonstrated on the values of interaction factors ky which are significantly higher for stainless steel members due to the material non‐linearity with decreased stiffness even at lower stress levels. As an alternative, the General Method is used for comparison to the Abaqus GMNIA model results. The limitation of the method when used for members of non‐linear material behaviour is shown and a simple and safe modification of global analysis method is suggested.
05.09: Experiment study on square steel tubular columns: Under compressive axial force with monotonic antisymmetric bending moment
Authors: Aoyama Masahiro , Mitsui Kazuya , Sato Atsushi
Published: September 2017

In Japan, square steel tubular columns are widely used. When the building is subjected to a lateral force, columns will subject axial force with antisymmetric bending moment simultaneously. Therefore, it is important to design the column under these combined loading in the ultimate limit state to guarantee the safety. Recommendation for Limit State Design of Steel Structure (LSD) [1] specifies the requirements for columns to guarantee sufficient strength and ductility. The plastic deformation capacity of the columns that are subjected to the compressive axial force with one end monotonic bending moment are ensured more than 3 by LSD. However, specific deformation capacity of the column that are subjected to the compressive axial force with monotonic antisymmetric bending moment is hardly shown in experimental test. Therefore, it is necessary to gather more data of maximum strength, deformation capacity, and elasto‐plastic behaviour of square steel tubular columns by testing. Moreover, second‐order effects is needed to take into account because high compressive axial force leads to elasto‐plastic instability.

In this study, testing where axial force with monotonic antisymmetric bending moment are applied to the columns simultaneously are conducted. Maximum bending moment, deformation capacity, and second‐order effect that will be caused by Pδ moment were evaluated from the test results. Comparison between LSD requirements and test results were also shown.

From the test results, followings are found.

1) The plastic deformation capacity of the square steel tubular column will be determined by either local buckling or Pδ moment.

2) When second‐order effects determined the plastic deformation capacity, the plastic deformation capacity R of the columns had a linear relation between N/Ny.λc02. When the value of N/Ny.λc02 is smaller than 0.25, a plastic hinge was formed at the end of the column, and the plastic hinge determined the collapse mechanism.

3) The current LSD limitation provided conservative results, and the plastic deformation capacity greater than 3 was observed even if the limitation was not satisfied.
05.14: Lateral torsional buckling of steel beams: Effect of discrete flexible intermediate supports at the upper flange
Authors: Unterweger Harald , Kettler Markus , Loschan Sarah
Published: September 2017

To avoid lateral torsional buckling in steel constructions, beams are often stiffened with discrete flexible intermediate supports (e.g. purlins in roof structures with bracings), which reduce lateral deformations of the flanges out of plane. Very often, these intermediate lateral supports can't be assumed as fully rigid and only restrain one of the flanges (i.e. no torsional restraint available), leading to a design situation that is only insufficiently reflected in EN 1993‐1‐1. Neither commonly used interaction formulae, derived on the basis of free single span members with fork end conditions and for members supported laterally and torsionally by intermediate rigid restraints, nor the simplified assessment method for beams with restraints in buildings (clause 6.3.2.4), based on a lateral buckling check of the compression flange, lead to an appropriate solution.

In this paper, the results of an extensive numerical parametric study on beams with intermediate flexible lateral supports at the upper flange are presented.

In the first part of the paper the focus is on the appropriate selection of the relevant buckling mode for the geometric imperfections, to obtain the minimum load carrying capacity within a numerical nonlinear calculation. As expected, a decrease of the spring stiffness always leads to a reduced elastic critical buckling load. Nevertheless, when assuming geometric imperfections based on the 1st buckling mode, this may lead to a higher ultimate load than for the system with rigid intermediate supports, when identical imperfection amplitudes are used.

In the second part of the paper a first design proposal is presented, valid for different moment distributions and number and stiffness of intermediate supports.
05.15: Development of circular tube slenderness classifications under axial and bending actions
Authors: Rotter John Michael , Sadowski Adam Jan
Published: September 2017

Local buckling in circular tubes differs from that in cross‐sections formed from flat plate elements (I, H, RHS etc.) because the latter retain their original shape up to the point of local buckling and plates are not very sensitive to minor geometric imperfections. By contrast, the curved form of the circular tube or cylindrical shell is very sensitive to minor imperfections and under bending is also strongly affected by geometric nonlinearity when the tube is significantly long. The classification of circular hollow tubular sections (CHS) into Classes 2, 3 and 4 is thus more complicated than for flat plate sections. It may be also noted that the “effective section” treatment of flat plates in Class 4 cannot be used for cylindrical shells. These differences, often ignored, have led to a very wide discrepancy in the classification rules for tubes in different international standards.

This paper sets out a clear description of the factors behind the development of new classification rules for CHS designed for adoption into EN 1993‐1‐1 [1]. The effects of length, full and partial plasticity, imperfections and cross‐section distortion are all included using individual provisions. It is also believed that these are the first rules to attempt a rigorous treatment of the resistance of Class 3 CHS subject to both bending and axial compression. The fully plastic resistance of tubes under axial force and bending is also treated with great precision. The formulation is novel, so may prove interesting to others who seek to develop similar rules for other structural shapes.
05.28: Deformation capacity of steel column under combined loading: Compressive axial force with double curvature bending moment
Authors: Sato Atsushi , Ono Tetsuro
Published: September 2017

Horizontal forces subjected to the moment resisting frame will be essentially resisted by the flexural manner of the columns. Horizontal forces are significant under seismic action; combined loading condition have a possibility to destabilize the columns. In ultimate limit state design, formation of the plastic hinge at the columns are allowed; however, it not permitted to lose its resistance. Moreover, sufficient deformation capacity at the plastic hinge should be guaranteed to fulfill the collapse mechanism of the structure. Following failure modes can occur in the column; 1) local buckling, 2) lateral torsional buckling for the open section subjected to strong axis bending, and 3) in‐plane second‐order effect instability. These failure modes should be prevented to guarantee the ductility of the plastic hinge which is formed in the column.

In this paper, column instability due to second‐order effect introduced by compressive axial force is studied. Numerical simulation is used to clarify this issue and in‐plane behaviour is evaluated. Parameters selected for the analysis are cross‐section shape, slenderness ratio, compressive axial force, bending moment distribution, material strength, and initial imperfection. From the results, it was found that material strength is not a significant parameter for column instability which is caused by the second‐order effect. Finally, the formula which can guarantee a sufficient deformation capacity to the column was proposed. Proposed formula was composed by the information of cross‐section shape, slenderness ratio, bending moment distribution, and force level subjected to the column.
05.31: Experiments and fem‐simulations of local buckling of sand‐filled tubular piles
Authors: Winkel Jort , Kostis Nikolaos , Peters Dirk Jan , van Es Sjors Harry Jan
Published: September 2017

Thin‐walled large‐diameter tubular piles loaded in bending are susceptible to local buckling. Depending on the bending moment distribution over the length of the pile, this local buckling failure may occur in the part of the pile that is embedded in the soil. In large‐diameter piles, soil is also present at the inside of the pile. The soil mass inside and outside of the pile may influence the bending behaviour and local buckling behaviour of the piles.

In case the internal soil plug consists of granular material and is sufficiently stiff and resistant, the soil influences the buckling shape and the critical stress and strain at which local buckling occurs.

Experiments that were performed in 2012 on empty and fully sand‐filled tubes loaded in pure bending showed a significant effect of the sand‐fill. The experiments were verified with finite element analyses to better understand the occurring failure mechanisms in tube and soil and the effects of parameter variations.

In 2014, new experiments were carried out in the port of Rotterdam on 914 mm diameter piles installed in the harbour bed. After installation, the embedded part the piles remained predominantly filled with soil, whereas the upper part was empty. Eight piles were installed and were loaded with a lateral force up to excessive yielding and local buckling failure. These experiments were analysed with FEM calculations. These analyses included effects of the soil plug and the soil around the pile.

The outcomes of the FEM model calculations confirm the experimental findings of a change in buckling shape as a result of the presence of sand inside the pile. The experiments and finite element analyses show that there is an evident contribution of the inside sand with certain properties to the resistance to local buckling. For the piles that are not completely filled with sand but have a plug at a certain level, design rules for the effect of the sand plug were derived.
05.33: LTB resistance of rolled I‐section beams: FEM verification of Eurocode's buckling curve formulation
Authors: Giżejowski Marian Antoni , Szczerba Radosław Bronisław , Gajewski Marcin Daniel
Published: September 2017

This paper attempts to verify the Eurocode's buckling resistance criteria in case of rolled I‐ and H‐sections in monoaxial bending about their major axis using finite element simulations and two imperfection modelling techniques, namely a) using the equivalent geometric imperfection concept in which the effect of material and geometrical imperfections is represented by an equivalent minor axis bow amplitude and the lowest eigenmode imperfection profile, and b) the separate inclusion of material and geometrical imperfections. In the latter approach, material imperfections are based on the standard rolled residual stress patterns consisting of compression/tension peak values dependent upon the h/b ratio. Moreover, the geometric imperfections are included as the tolerance limit of steel I‐section rolled products. Common and higher grades of steel products are considered. The finite element shell model is utilized and built within the ABAQUS software. The Eurocode's resistance criteria are verified by using the results of FEM simulations. An impact of the moment gradient on the member buckling resistance as well as the plateau limit evaluation and the resistance increase as a result of large twist rotations accounted for are assessed. Remarks in relation to analytical formulations presented in Eurocode 3 are drawn.
05.34: Influence of temporary bridge decks on continuously welded rails
Authors: De Backer Hans , Mys Jan , Van Puymbroeck Evy
Published: September 2017

The possibility of omitting rail expansion devices from the track configuration, when continuously welded rail is continued over temporary bridge decks, is investigated in detail. More specifically, the related rail track to temporary bridge interaction phenomena are analysed using finite element modelling. A parametric analysis assesses the additional rail stresses due to moving trainloads and temperature variations, based on stipulations provided in the unit identification code 774‐3R. In addition, the model is expanded to a more complex structure that is able to simulate the buckling behaviour of the rail track using non‐linear methods. It can be concluded that, depending on the magnitude of two main factors, the lateral ballast resistance and the amplitude of the initial track misalignment, a considerable reduction of the track stability might arise.
05.37: On stability of unbraced steel frames with semi‐rigid joints
Authors: Krystosik Przemysław
Published: September 2017

The paper presents the issue of unbraced and semi‐rigid steel frames stability with special attention paid to the problem of determining buckling length Lcr of columns in these frames.

The paper discusses ways of buckling length determination in frames columns with the use of selected, simplified procedure, as well as numerical method of stability analysis. The presented procedures and the analysis methods were used in calculations of certain steel frames. On the basis of presented results, it has been shown that in many practical cases, the simplified procedure of buckling length determination can give error‐prone results.

The issues presented in the paper are important from the practical point of view, and therefore, they should be taken into account in the design process of such frames.
05.38: Design procedure development of light gauge built‐up beam to ensuer yield bending strength: Antisymmetric bending moment
Authors: Yoshimoto Shun , Sato Atsushi
Published: September 2017

American Iron and Steel Institute (AISI) stipulates a lateral force resisting system called CFS‐SBMF. In this system, built‐up beams are connected to hollow section columns by bolts to compose moment frame.

Structural system proposed in previous study used built‐up beam in shape of rectangular section. Built‐up beams are composed by double channels toe‐to‐toe. When the beam is subjected to loads, 4 pattern of collapse mechanisms can be expected.

1) Yielding;

2) Lateral torsional buckling (LTB) of built‐up member;

3) LTB of individual channel between the connecting plates;

4) LTB of individual channel due to lack of the connecting plates stiffness and strength.

Yielding, full capacity of the member, is expected in seismic design to maximize the performance of the structural system; therefore, it is necessary to prevent collapse mechanisms from No.2 to No.4.

To prevent the collapse mechanism No.2, following shall be fulfilled. Assuming that the section of the beam is rectangular steel tubular member. Then the length of the beam will be checked with this length; it is fulfilled when the beam is shorter or equal to the computed allowable length.

To prevent the collapse mechanism No.3, following numerical simulation shall be conducted to propose design procedure. Length between connecting plates is set as parameter; connecting location was distributed equally in the longitudinal direction of built‐up member.

To prevent the collapse mechanism No.4, following design procedure is proposed. It was assumed that failure at the connecting plate, i.e., yielding, will not occur when it is designed to be stronger than the connected channel flange out‐of‐plane strength.

Finally, design procedure that can prevent unexpected collapse modes was verified by numerical simulation. Proposed design procedure is applicable to design appropriate built‐up beam in an economical manner.
05.41: A unified catastrophe theory approach for the in‐plane buckling of steel arches under point gravitational loading
Authors: Pantazi Vasiliki S. , Sophianopoulos Dimitrios S.
Published: September 2017

The problem of the buckling response of various types of steel arches has been the subject of a vast number of earlier as well as recent papers and chapters of books. Namely, the majority of all these works aimed – via analytical and/or computational approaches – to establish the nature of the postbuckling response of the foregoing structures. It has been found over the years that two types of loss of in‐plane stability are dominant: (a) snap‐through, a characteristic of shallow (flat) arches (low height to span ratio), in a symmetric or asymmetric mode (limit point or bifurcation), and (b) sideways buckling (deep arches). In the latter situation, the axial inextensibility (being a justified simplifying assumption) becomes dominant and in the case of radial load and circular arch configuration the whole analysis is rather easy and convenient, using equilibrium considerations. On the other hand, low arches (with unavoidable shortening of their center line) can be thought of as curved beams; hence their buckling analysis may be performed from the viewpoint of energy. However, there not seems to be a unified approach overall, especially since the geometry of arches may be significantly varying, from circular to elliptical, parabolic, sinusoidal and catenary, and hence the height at the crown and the span are not the only parameters this geometry is dependent on. Moreover, if one considers a point gravitational loading acting on the arch, a case scarcely reported, then the whole analysis is multiparametric, since it involves (a) the value of the load and its position, (b) the cross‐sectional and material characteristics and (c) the geometrical configuration parameters. This work aims to provide a unified approach for the foregoing problem based on the Theory of Catastrophes. The total potential energy function involving all the parameters is firstly established, and furthermore all restrictions related to boundary conditions, geometry, material and cross‐sectional properties. Using an approximate 4th order polynomial postbuckling shape, it was found that the problem at hand is governed by a singularity that strongly resembles the butterfly. The work is ongoing and will hopefully reveal interesting future results for structural design purposes.
05.43: Lateral‐torsional buckling of beams of double symmetrical and mono‐symmetrical cross‐sections loaded perpendicularly to the axis of symmetry: Experimental verification
Authors: Horáček Martin , Melcher Jindřich
Published: September 2017

The current design procedures listed in the European standards provide general rules for the calculation of the effects of lateral torsional buckling of steel members. The buckling resistance of the ideal beam (without any imperfections) is represented by the elastic critical moment, which is used for the determination of the relative slenderness. In the general document of Eurocode 3 are no analytical solutions for the calculation of the elastic critical moments. The Czech and Slovak National Annex of EN 1993‐1‐1 provide the procedures for the elastic critical moment calculation for at least mono‐symmetrical profiles loaded in the plane perpendicular to the axis of symmetry. There are no comments in the national annexes of the other European Countries related to the determination of elastic critical moment by analytical way.

This paper focuses on the experimental verification performed in the laboratory conditions in order to prove the save and efficient design of bended beams with respect to lateral torsional buckling based on the procedures listed in the Czech or Slovak National Annex. Freely supported beams are loaded in the 1/3 of the beam with 2 point loads. The special attention is given to the method of loading, which allows free lateral torsional buckling of the beam without any restraints to the horizontal displacement and rotation of the beam. In order to examine the pure effects of lateral torsional buckling the effects of local instabilities such as for example local buckling or web crushing under the concentrated load, the test specimens are supplemented by suitably located stiffeners.
07.03: Distortional‐global interaction in lipped channel beams: Part II: Strength, relevance and DSM design
Authors: Martins André Dias , Camotim Dinar , Dinis Pedro Borges
Published: September 2017

This work aims at presenting and discussing numerical results concerning the post‐buckling behaviour, strength and design of two types of simply supported lipped channel (LC) beams under uniform major‐axis bending and undergoing distortional‐global (D‐G) interaction. The relevance of the interaction effects is assessed by determining the beams whose ultimate strength and/or failure mode are visibly affected by them. Distinct (i) global‐to‐distortional critical buckling moment ratios (RGD) and (ii) yield‐to‐non critical buckling (distortional or global) moment ratios (Ry) are considered and, thus, different failure mode natures (global, distortional or interactive) are expected. For each beam type, combinations of 41 geometries and 11 yield stresses are dealt with, in order to (i) characterise the beams experiencing “true D‐G interaction” (RGD≈1.0) and “secondary global‐bifurcation D‐G interaction” (RGD >1.0 + high Ry) and (ii) investigate the possible occurrence of “secondary distortional‐bifurcation D‐G interaction” (RGD <1.0 + high Ry). The results presented consist of (i) relevant non‐linear equilibrium paths, (ii) deformed configuration evolutions along those paths and (iii) figures providing the failure mode characterisation. Then, the numerical failure moments obtained are compared with their predictions by (i) the currently codified DSM (Direct Strength Method) beam global and distortional strength curves, and (ii) proposed DSM‐based design approaches, specifically developed to handle D‐G interactive failures.
07.09: Trapezoidal sheet hangers and concentrated or linear load distribution in profiled sheeting
Authors: Šorf Marek , Jandera Michal
Published: September 2017

With increasing depth and load‐bearing capacity of cold‐formed trapezoidal sheeting, they are used more often with hangers bolted to the webs of the sheeting. Several tests of the hangers resistance are shown for various type profile, sheet thickness and possible perforation of the web which are the main variable factors affecting the load capacity of the hanger connections. A simple and safe design procedure is given. More importantly, the distribution of the load applied by the hangers to the profiled sheeting ribs as concentrated load per the rib is often critical for the profile resistance in bending or to satisfy the deflection limit however the distribution of the load between the ribs is not known. Therefore an advanced numerical study (GMNIA) in software Abaqus was carried out for several section types and loading conditions. The model used for the analytical study was again validated by tests. The main conclusion of the paper is a developed design procedure allowing the possible redistribution of concentrated load between the ribs in case of simply supported members whose design is governed by deflection or bending resistance.
07.14: Rack uprights under combined compression and bi‐axial bending: Experimental testing, numerical analysis and European standard approach
Authors: Pastor Ma Magdalena , Bonada Jordi , Roure Francesc , Casafont Miquel , Somalo Ma Rosa
Published: September 2017

Pallet rack uprights are thin‐walled mono‐symmetric perforated open steel cross‐sections subject to combined axial compression and bending. Loads (pallets of goods to be stored) are transmitted to uprights through the beams and the beam‐upright connections. Bending about the major axis (cross aisle direction) is induced to the upright by the eccentricity of the beam end plate and the moment transmitted by the semi‐rigid beam to upright connection. The bending about the minor axis (down‐aisle direction) is induced by eccentricity of the axis of the beam and the axis of the upright. The nature of these components, with perforations and buckling failure modes, together with combined actions, is a challenge in structural design.

The main objective of this investigation is to provide a comprehensive empirical, numerical and analytical analysis of how bending combined with axial compression influences in the design load of pallet rack uprights.

This paper presents experimental tests performed on uprights under combined compression and bending, and the FEA including nonlinear geometric and material behaviour. Both results are compared to the current European Standard, EN 15512, for Steel static storage systems.

One type of cross section has been analysed, with a length that can produce different type of failure modes, mainly local and distortional buckling. The uprights have been analysed with different axial – bending combinations, which cover the field of combinations possible in the real load conditions of the rack.
07.23: Effect of loading rate on the pull‐through capacities of cold‐formed steel roof battens
Authors: Kathekeyan Myuran , Mahendran Mahen , Sivapathasundaram Mayooran
Published: September 2017

Localised connection failure is the main shortcoming of cold‐formed steel roofing systems subjected to high wind suction loads. Pull‐through failure in the vicinity of roof batten to rafter connection is the major connection failure observed during recent high wind events. Both static and fatigue pull‐through failures occur based on the type of wind loads (static or cyclic loads). The loading rate to be used in the static and cyclic pull‐through failure tests is a moot point as the wind loading frequency can vary during wind events such as storms and cyclones. Therefore, it is necessary to understand the effect of wind loading frequency/rate on the pull‐through failures of steel roof battens. This paper investigates the influence of loading rate on both static and fatigue pull‐through capacities of steel roof battens by means of a series of static and cyclic tests conducted at various loading rates/frequencies. Initially, tests were conducted on roof battens made of two steel grades (G300 and G550) and two thicknesses (0.8 and 1 mm). The results showed a significant improvement in the pull‐through capacities during tests using higher loading rates. They also showed that the current static and cyclic pull‐through design rules/guidelines do not include the effect of loading rate. Secondly, to understand the influence of loading rate on the pull‐through capacity of battens, the effect of loading rate on the mechanical properties of steels was investigated using 40 tensile coupon tests. The effect of loading rate on both the tensile strength of steel used and the pull‐through capacity of roof batten was then compared. Using the results of comparison, the reasons for the increase in the static pull‐through capacity of roof battens with loading rate are discussed and, a recommendation is made in relation to the loading rate to be used with the new Low High Low (LHL) cyclic test. This paper presents the details and results of this study.
07.27: Experimental and theoretical investigation on the local collapse of liner trays
Authors: Georgescu Mircea , Ungureanu Viorel , Gruin Aurelian , Floricel Andra
Published: September 2017

Liner trays are thin‐walled cold‐formed steel sections of large channel‐type with two narrow flanges, two webs and one wide flange, very frequently used in practice both to resist perpendicular uniformly distributed loading from the wind and create a diaphragm effect at the level of industrial building cladding. When trying to evaluate the resistance of such elements by experiment, the specific constructional details play a major role and create quite complex problems in establishing a correct experimental setup, as close to reality as possible. Testing one single liner tray thus imposes correct simulation of real boundary conditions both on liner support and at mid‐span. Global collapse modes are not possible in such liner trays assembly while local modes are expected and impose the final value of experimentally measured resistance to perpendicular load. The correct introduction of real boundary conditions into the experimental setup will thus facilitate a measured value reasonably close to the one determined to code provisions. The paper describes the experimental and numerical investigations on liner trays. Aspects related to the experimental test setup and test results are emphasised.
07.28: Fastening to face sheets of sandwich panels
Authors: Misiek Thomas , Käpplein Saskia
Published: September 2017

In several applications the need to anchor loads in sandwich panels arises. This is normally done by introducing the load into one face, using mechanical fasteners such as screws or rivets for tensile and shear forces or contact for compression forces. Nowadays the most common example for these applications are fastening of solar cells (PV‐modules) on sandwich roof panels or fastening of additional façade layers on sandwich wall panels.

The paper deals with the different possibilities of introducing forces into the panels, covering both flat or lightly profiled faces used for walls and profiled faces used for roofs. Special attention is paid to design, including verification of fastenings, web crippling of profiled faces and effect on global load‐bearing behaviour of the sandwich panels.

In a second step, delamination caused by tensile forces is investigated in more detail: Pull‐out failure is generally the acceptable failure mode and can be achieved by keeping a minimum edge distance. But if repeated loads such as wind loads are acting on the fasteners, the governing failure mode tends to be delamination at lower load levels. Small cracks in the bond layer grow until final failure of the connection or even of the complete sandwich panel by reducing the wrinkling strength of the face. To study both, the influence of the edge distance and the effect of repeated loads, experimental tests and numerical investigations were performed. The results are presented and discussed.

ECCS TC7 TWG7.9 and CIB W056 are currently working on a document dealing with point and line loads acting on sandwich panels. Fastening to face sheets of sandwich panels is one of several topics. Thus the present paper may be regarded as a position paper, showing the state of the art related to a specific single item of the document and giving additional references related to this topic.