A probabilistic approach for a T-stub ultimate strength assessment using response-surface approximation

The main goal of the study is to examine and demonstrate the application of a developed probabilistic framework to the analysis of a chosen general type of steel connection component in order to obtain the basic characteristics of its mechanical behaviour with regard to the chosen type of the input geometry and material properties. Accordingly, as a typical representative of the component method proposed by the Eurocode the equivalent T-stub was chosen as a subject of the study. This type of structural element has the capability to address the behaviour of several parts of the connection: column flange in bending, end plate in bending and flange cleat in bending. A method is proposed to determine the probability density function of the ultimate strength using a response-surface approach coupled with FEM applied to a stochastic structural model. The results of a study were processed by means of sensitivity analysis to determine the importance level of the input variables

Validation of an analytical model for curved and tapered cellular beams at normal and fire conditions

The growing use of cellular beams in steel construction leads to the development of various configurations such as curved and tapered cellular beams. In order to provide a tool predicting the behavior of those beams for design applications, the CTICM developed a software based on analytical formulas with adaptation to the curved and tapered cellular beams. Recently, the analytical formulas were adapted to fire conditions. In this paper, a nonlinear numerical model is developed and performed to validate the analytical approach. The model is applied to curved and tapered beams considering various opening and support configurations in normal and fire conditions. The comparison between the numerical and the analytical results validates and shows the possibilities of the analytical model and its limits

Caractérisation expérimentale d'assemblages de plaques boulonnées par mesures de champs sans contact

International audienceLes assemblages de plaques boulonnées sont largement utilisés en construction métallique. Ils permettent le transfertde différents efforts internes tels que flexion, efforts axiaux et de cisaillement. Le comportement mécanique de ces assemblagesest complexe à cause du transfert d'efforts entre boulons et plaques. Cela est dû à la fois à la nature hyperstatique de la liaison,à l'évolution du contact entre les boulons et leurs trous et au comportement élastoplastique des plats métalliques constituantsl'assemblage. L'interaction entre les trous d'une même plaque est aussi très importante au regard des différentes configurationsdes liaisons et des positions des trous. Les différents modes de ruine sont la rupture de section nette, la déformation plastiquedes sections brutes, le cisaillement des boulons et la pression diamétrale sur le trou de la plaque. Parmi ces modes, la pressiondiamétrale est la plus difficile à prédire car elle combine compression locale des trous par les boulons et cisaillement de lazone chargée située entre le trou et le bord de la plaque. De nombreuses études analysent le comportement d'assemblages deplaques en combinant des calculs par éléments finis avec des expérimentations instrumentées par un nombre limité de jauges dedéformation pour estimer la distribution des déformations dans les composants des joints. Dans le présent travail, la méthodede la grille est utilisée pour analyser en détail la distribution des déformations des plaques pour différentes configurations depositions de trous chargés ou non par des boulons. Cette approche permet d'observer les champs de déformations dans unelarge zone autour des boulons dans les phases élastiques et plastiques. Les résultats sont utiles pour comprendre à la fois lelien entre les zones affectées par la ruine et le mode de ruine par pression diamétrale. Cette méthode peut également servir deréférence pour calibrer des modèles complexes d'éléments finis.</p

Evaluating the Behaviour Factor of Medium Ductile SMRF Structures

In seismic codes, the capacity of structures is calculated using capacity design procedure based on the concept of base shear. The critical parameter in this procedure is the behaviour factor (q-factor), which allows designing the structures at the ultimate limit state accounting for their ductility and reserve strength. In this paper, the q-factor is evaluated for medium ductile steel moment-resisting frames (SMRF) using pushover analysis. The influence of specific parameters, such as the stories number, the “Column/Beam” capacity and the local response of structural members, is studied. The results show that the most important parameter that affects the q-factor is the local response of first-storey columns, while the “Column/Beam” capacity has a less effect on this factor. Furthermore, it is observed that the q-factor value assigned to the studied frames in Eurocode-8 is systematically underestimated for low-rise frame, while the use of this value for high-rise frame is potentially unsafe

Behavior of beam web panel under opposite patch loading

International audienceElastic buckling is studied for a panel with various boundary conditions including simple supports, fixed supports and elastic restraints. The panel is subjected to opposite patch loading. Following a review of existing work on the effects of localized compression, also known as patch loading, a study is conducted to take into account the restraints provided by the flanges of the I beam in a realistic manner. This study is based on a finite element model implemented in the CAST3M software. A new equation is proposed to calculate the buckling critical coefficient for a beam web panel considering the rotational stiffness provided by the flanges. The model is then applied to longitudinally stiffened web panels which are subjected to opposite patch loading.A parametric analysis is performed to determine the transition from a global buckling mode to a local buckling mode where the sub-panels on each side of the stiffener behave separately. The numerical results show that the flexural rigidity of the stiffener is the appropriate parameter that governs the buckling mode. From these results, a formula is proposed to calculate the buckling critical coefficient of stiffened web panels

EXPERIMENTAL STUDIES OF UNPROTECTED AND PROTECTED STEEL STRUCTURES UNDER FIRE

Preliminary fire experimental tests have been carried out on steel plates protected with intumescent coating.The tests evaluated and measured the heating of steel plates with various geometrical configurations: shape, size. A first test on an equal leg angle section showed interesting results with different coating expansion on the faces of the section.The second test campaign is done with different protections to compare behaviors of four steel plates. The first objective is to set up an experimental protocol for future tests. Those results are used to evaluate analytical prevision of steel plate temperature with and without fire protection

Pull-out performance of densified wood dowels embedded into glued laminated timber

International audienceDue to the corrosion of fasteners by water-based preservatives, the preserved timber in outdoor environments can decrease the service life of the metal fasteners. In addition, the segregation of timber members and metal fasteners is also difficult during the demolition of timber structures. Wooden fasteners can be a promising alternative to metal fasteners because they have favorable resistance against corrosion and are more naturally harmonized with timber members. This paper studied the pull-out performance of dried densified wood (DW) dowels embedded into glued laminated timber (glulam) parallel to the grain with three different embedded lengths in two ambient environments with a temperature of 20°C and relative humidity (RH) of 65% and with a temperature of 20°C and relative humidity of 85%. The hygro- scopic swelling of the dried DW dowels with a long embedded length can provide the favorable friction locking to transfer the axial load

Seismic assessment of a heavy-timber frame structure with ring-doweled moment-resisting connections

The performance of heavy-timber structures in earthquakes depends strongly on the inelastic behavior of the mechanical connections. Nevertheless, the nonlinear behavior of timber structures is only considered in the design phase indirectly through the use of an R-factor or a q-factor, which reduces the seismic elastic response spectrum. To improve the estimation of this, the seismic performance of a three-story building designed with ring-doweled moment resisting connections is analyzed here. Connections and members were designed to fulfill the seismic detailing requirements present in Eurocode 5 and Eurocode 8 for high ductility class structures. The performance of the structure is evaluated through a probabilistic approach, which accounts for uncertainties in mechanical properties of members and connections. Nonlinear static analyses and multi-record incremental dynamic analyses were performed to characterize the q-factor and develop fragility curves for different damage levels. The results indicate that the detailing requirements of Eurocode 5 and Eurocode 8 are sufficient to achieve the required performance, even though they also indicate that these requirements may be optimized to achieve more cost-effective connections and members. From the obtained fragility curves, it was verified that neglecting modeling uncertainties may lead to overestimation of the collapse capacity