Saint-Aubin-lès-Elbeuf, France
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Kanyilmaz A.,Polytechnic of Milan | Castiglioni C.A.,Polytechnic of Milan | Degee H.,Hasselt University | Martin P.-O.,CTICM
COMPDYN 2015 - 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering | Year: 2015

Concentrically braced frames (CBF) represent a very effective structural form against horizontal loading. They provide high lateral resistance at the same time limiting lateral displacements. Thanks to their simpler connection details and smaller cross sections, they are economic alternatives to the costly moment resisting frames. Nevertheless, concerning the seismic design, current Eurocode 8 provisions require a quite high level of complexity for the dissipative design of CBF structures. The global aim of this research is to find an optimal balance between safety and economy for the design of CBF structures, located in low-to-moderate seismic regions. New design rules will be proposed which will have less stringent local ductility and structural homogeneity requirements than current medium ductility class (DCM), and provide necessary safety level limiting the complexity and costs associated with anti-seismic design. This paper presents the results of the preliminary numerical analysis that has been realized thanks to the research fund received from European commission with the contract MEAKADO RFSR-CT-2013-00022.

Pak D.,RWTH Aachen | Hechler O.,ArcelorMittal | Martin P.-O.,CTICM
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2011

Integral abutment bridges (IABs) are an economical option to design appealing single-span bridges. However, more experience is needed, as the main difference in the design of IAB compared with conventional bridges is the restraint of the frame corner, caused by the fact that the supe rstructure and the abutments are one monolithic structure. This requires modification in design regarding the internal forces and deformations as well as the detailing of the frame corner itself. IABs are generally designed as frames us ing grid models with idealised superstructure. This calculation involves sophisticated models and is considered to be time consuming. Also conventional single-spa n bridges are designed with the help of grid models, for which experience and various design software tools exist, especially when simply supported structures are considered. Main problem in the transfer of frame systems into simply supported structures are the interactions between superstructure and sub-structure. By separating the superstructure from the sub-structure, the implementation of IAB design through existing software tools is possible. However, to take into account the superstructure- abutment interaction, the superstructure needs to be restrained by rotational springs. As a result of sway effects in the original frame, the boundary conditions (horizontal position of the frame corner) for the determination of the rotational spring stiffness vary. Therefore these springs have to be non-linear, and do not comply with the demand for load case superposition. This paper presents a new approach to separate the superstructure from the sub-structure with p rovision for possible superposition of the load cases. The approach is based on the division of the non-linear springs into two linear springs, one for symmetric loading and the other for antimetric loading, from which a modification factor kmgk has been derived. This factor is defined as adjusting the single-span model with a single rotational linear spring to the original grid model system. On the basis of this approach and the kmgk factor, the use of conventional design tools for IABs has been made possible. To further close the gap in experience on IAB, design and detailing recommendations are given.

Vassart O.,ArcelorMittal | Bailey C.G.,University of Manchester | Hawes M.,ASDWestok Ltd | Nadjai A.,University of Ulster | And 4 more authors.
Proceedings of the Institution of Civil Engineers: Structures and Buildings | Year: 2012

This paper describes a full-scale fire test performed recently on a composite floor for analysing the possibility for tensile membrane action to develop when unprotected steel beams in the central part of the floor are made of cellular beams. The natural fire was created by a wood crib fire load of 700 MJ/m2 and the 9 m × 15 m floor survived the fire, which peaked at 1000°C and lasted for about 90 min. Blind predictions of the air temperature development by the software 'Ozone' and of the structural behaviour by the software 'Safir', which proved quite satisfactory, are also described.

The fatigue behaviour of aluminium shows not only many similarities, but also some differences with the fatigue behaviour of steel. There exist separate Eurocodes for the fatigue design of steel and of aluminium structures, EN1993-1-9 and EN1999-1-3, respectively. The latter standard was developed after the draft version of the first one was available. However, a number of aspects are considered in a different way in the two standards. Are these differences justified and desired? What can we learn from the two standards for future improvement of the documents? This paper presents and discusses the agreements and differences between the two Eurocodes. The paper evaluates the advantages and disadvantages of the approaches adopted in one or another of the two standards. It may serve as a starting point for future harmonization of the two standards. © 2013 The Authors. Published by Elsevier Ltd.

Zhao B.,CTICM | Roosefid M.,CTICM
Structures in Fire - Proceedings of the Sixth International Conference, SiF'10 | Year: 2010

The very positive membrane action of steel and concrete composite floor systems (concrete slabs connected to steel beams by means of headed studs) has been clearly demonstrated through various Cardington real fire tests. However, little evidence is established for fire performance of such structural system exposed to ISO fire condition, the lack of which still constitutes an obstacle for certain national authorities to accept totally the application of the design concept derived from above real fire tests, in particular for long duration ISO fire. On the basis of above situation and in order to enlarge the application of the design concept based on membrane action to all types of fire, CTICM, within the scope of two different research projects FRACOF and COSSFIRE, performed successively two full scale ISO fire tests, both of which lasted for more than 120 minutes, with two different steel and concrete composite floor systems designed according to Eurocode. The observed fire performance of these floor systems during the tests was extremely satisfactory and revealed a solid robustness of such type of structure systems in fire situation. Considering the fact that the fire test of FRACOF project has been already presented in detail during previous SIF conference, this paper is focused especially on the comparison of above two tests with regard to structural configuration, loading condition, structural behaviour and the failure modes. In addition, these tests have been subjected to a specific numerical investigation with help of a 3D hybrid structural FE model. It is illustrated through this numerical investigation that the actual advanced modelling technique is accurate enough to reproduce precisely the fire behaviour of complex structural systems and may be applied to fire safety engineering with high level of confidence.1.

Franssen J.-M.,University of Liège | Zhao B.,C.T.I.C.M. | Gernay T.,University of Liège
Journal of Structural Fire Engineering | Year: 2016

Purpose-The purpose of this paper is to gain from experimental tests an insight into the failure mode of slender steel columns subjected to fre. The tests will also be used to validate a numerical model. Design/methodology/approach-A series of experimental fre tests were conducted on eight full-scale steel columns made of slender I-shaped Class 4 sections. Six columns were made of welded sections (some prismatic and some tapered members), and two columns were made of hot rolled sections. The nominal length of the columns was 2.7 meters with the whole length being heated. The load was applied at ambient temperature after which the temperature was increased under constant load. The load was applied concentrically on some tests and with an eccentricity in other tests. Heating was applied by electrical resistances enclosed in ceramic pads. Numerical simulations were performed with the software SAFIR® using shell elements. Findings-The tests have allowed determining the appropriate method of application of the electrical heating system for obtaining a uniform temperature distribution in the members. Failure of the columns during the tests occurred by combination of local and global buckling. The numerical model reproduced correctly the failure modes as well as the critical temperatures. Originality/value-The numerical model that has been validated has been used in subsequent parametric analyses performed to derive design equations to be used in practice. This series of test results can be used by the scientifc community to validate their own numerical or analytical models for the fre resistance of slender steel columns. © Emerald Group Publishing Limited.

Thiebaud R.,Ecole Polytechnique Federale de Lausanne | Lebet J.-P.,Ecole Polytechnique Federale de Lausanne | Beyer A.,CTICM | Boissonnade N.,University of Applied Sciences and Arts Western Switzerland
Structural Stability Research Council Annual Stability Conference 2016, SSRC 2016 | Year: 2016

The Lateral Torsional Buckling (L.T.B.) design of beams in buildings has received considerable attention over the last decades, and relatively similar improved design rules are now implemented in major design standards. On the contrary, it may be shown that the various available design specifications for the L.T.B. design check of bridge girders still lead to significant discrepancies regarding the reduction curve to be used. Furthermore, the resistance to L.T.B. of steel bridges depends on several specific parameters such as cross-bracings, geometric imperfections and residual stresses. The present paper investigates both experimentally and numerically the influence of these parameters on the resistance to L.T.B., and proposes improved design rules.

Bihina G.,CTICM | Zhao B.,CTICM | Bouchair A.,CNRS Pascal Institute
Journal of Structural Fire Engineering | Year: 2014

The main results from a numerical investigation on a composite floor made of cellular beams at elevated temperatures are presented. From a full-scale natural fire test, a 3D finite element model has been developed under ANSYS code to simulate the thermo-mechanical behaviour of a composite floor with cellular beams. The calibration of this numerical model is based on the measured material properties and temperatures. A good correlation between the test and the numerical simulation is observed, in terms of temperatures, deformed shape and deflections. The finite element model is then used in a parametric study varying bay size, mechanical load and fire resistance rate. The results from this parametric study are compared to those from an analytical method, highlighting the conservativeness of the latter.

Bihina G.,CTICM | Zhao B.,CTICM | Bouchair A.,CNRS Pascal Institute
Engineering Structures | Year: 2013

The main results from an experimental and numerical investigation on cellular beams at elevated temperatures are presented. Full-scale fire tests on four specimens are presented and used to analyse the behaviour of composite steel and concrete cellular beams with evenly spaced circular and/or elongated web holes. The four beams were made of European hot-rolled sections. They were applied a two-point mechanical load. The beams were not fire protected and they were tested with an ISO fire or a bilinear thermal curve representing the behaviour of a protected beam. The results were then used to calibrate a non-linear 3D finite element model. The behaviour of the tested beams was simulated using two FEM codes (Cast3M and ANSYS). The first code was used for the thermal analysis and the second for the thermo-mechanical analysis. A comparison between the experimental and numerical results highlights the good accuracy of the model. The validated model was used in a parametric study varying geometry (span, steel cross-section depth, diameter and pitch of the openings, concrete or composite slab), mechanical properties and loading conditions (line load only or combined to point-load). The results were then compared to those from an analytical design method to check its validity. The results show that the analytical design method is conservative, with little discrepancy when compared to the numerical model. © 2013 Elsevier Ltd.

Beyer A.,CTICM | Galea Y.,CTICM | Bureau A.,CTICM | Boissonnade N.,University of Applied Sciences and Arts Western Switzerland
Structural Stability Research Council Annual Stability Conference 2015, SSRC 2015 | Year: 2015

The elastic stability of tapered beams has been investigated many times in the past. However, most of these studies consider beams subjected to bending moments only and therefore they do not consider the influence of axial force on the stability of the member. Consequently, flexural and torsional buckling modes under pure compression or combined compression and bending cannot be represented. The present paper presents-To the authors' knowledge-The first freely available program, LTBeamN, that allows designers to assess the-out-of plane elastic stability of beam columns considering the combined influences of the taper of the beam, intermediate lateral restraints and interaction of axial force and bending moments. First, the theoretical background of LTBeamN is presented. The linear and geometrical element stiffness matrices of the beam elements are derived on the basis of the energy method. In particular, the influence of the taper on the torsional behavior of the beam is pointed out. Numerical examples are then given to illustrate and validate the calculation of the critical load amplifier. Finally, a practical example shows how LTBeamN can simplify the verification of a tapered member with intermediate lateral restraints, by means of the global slenderness concept as proposed by the European standard Eurocode 3 (CEN 2005). Copyright © 2015 by the Structural Stability Research Council.

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