A PARAMETRIC SURVEY OF THE INFLUENCE OF THE SEMI-RIGID CONNECTIONS ON THE SHAKEDOWN OF ELASTO-PLASTIC FRAMES

In the past it was generally assumed that the connection of the beams and columns of the steel-framed multistorey structures are either rigid or pinned. In the reality, however, they are semi-rigid. This circumstance influences significantly the behaviour of the entire structure, therefore, it has to be taken into consideration in the analysis and design. In this paper a parametric study is presented to analyse the influence of the semi-rigid connections on the shakedown of elasto-plastic steel framed structures under multi-parameter static loading. To control the plastic behaviour of the structure bound on the complementary strain energy of the residual forces is also applied. The semi-rigid behaviour is modelled by appropriate internal springs at the beam column-connections. The formulation of the problem yields to nonlinear mathematical programming which is solved by the use of an iterative procedure. The parametric study is illustrated by the solution of an example

Nonlinear Time-Dependent Behavior of Composite Steel-Concrete Beams

International audienceThis paper presents a mixed finite element (FE) model for the nonlinear time-dependent analysis of composite beams with partial shear connection. The key idea is to consider, as a first approach, a viscoelastic/plastic model for the concrete slab in order to simulate the interaction between the time effects of concrete, such as creep and shrinkage, and the concrete cracking. Creep is taken into account via linear aging viscoelasticity, while cracking is modeled using an elastoplastic model with softening. A nonlinear isotropic/kinematic hardening model is adopted for steel behavior and an appropriate nonlinear constitutive relationship is utilized for the shear stud. A consistent time integration is performed by adopting the Euler backward scheme. Finally, comparisons between the numerical results and experimental data available in the literature are undertaken to validate the accuracy of the model. It is shown that the interaction between cracking and time effects (creep and shrinkage) significantly increases the deflection

Existence of renormalized solutions for some degenerate and non-coercive elliptic equations

summary:This paper is devoted to the study of some nonlinear degenerated elliptic equations, whose prototype is given by \begin{aligned}t 2&-{\rm div}( b(|u|)|\nabla u|^{p-2}\nabla u) + d(|u|)|\nabla u|^{p} = f - {\rm div}(c(x)|u|^{\alpha }) &\quad &\mbox {in}\ \Omega ,\\ & u = 0 &\quad &\mbox {on}\ \partial \Omega , \end{aligned}t where $\Omega$ is a bounded open set of $\mathbb {R}^N$ ($N\geq 2$) with $1<p<N$ and $f \in L^{1}(\Omega ),$ under some growth conditions on the function $b(\cdot )$ and $d(\cdot ),$ where $c(\cdot )$ is assumed to be in $L^{\frac {N}{(p-1)}}(\Omega ).$ We show the existence of renormalized solutions for this non-coercive elliptic equation, also, some regularity results will be concluded

Experimental study on in-plane capacities of composite steel-concrete floor

[EN] In steel frame structures, composite floor is an important element that plays a significant role in contributing to lateral stability. Its working role in the in-plane action is to transfer lateral loads, such as wind loads and seismic loads, to vertical load-resisting members. Such load transferring process depends on the in-plane capacities of the floor, which can be reduced after being subjected to explosion. However, the remaining capacities have not been previously studied yet in the literature. This paper presents an experimental investigation on the initial and residual in-plane capacities of the composite steel-concrete floor after being subjected to explosion, which was made within the RFCS research project BASIS:“Blast Action on Structures In Steel”. Large-scale experimental tests on four composite floor specimens, consisting of a reinforced concrete panel casted on a profile steel sheet Comflor, are performed to determine the in-plane capacities. The initial damaging of the composite floor caused by the explosion is reproduced by a flexural test using a quasi-static loading. In the in-plane shear tests, special connections between the rigid frames of the shear rig and the embedded bolts in the concrete are used to ensure a good transferring of the applied load. The results from this experimental study are the first insights on the behavior of the composite floor with and without initial pre-damaging. They can also be useful for a preliminary recommendation to estimate residual in-plane capacities (stiffness and resistance) of the composite floor after being subjected explosion.Heng, P.; Somja, H.; Hjiaj, M. (2018). Experimental study on in-plane capacities of composite steel-concrete floor. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 881-887. https://doi.org/10.4995/ASCCS2018.2018.6987OCS88188

Effect of the steel material variability on the seismic capacity design of steel-concrete composite structures : a parametric study

International audienceModern seismic codes recommend the design of ductile structures able to absorb seismic energy through high plastic deformation. Since seismic ductile design relies on an accurate control of plastic hinges formation, which mainly depends on the distribution of plastic resistances of structural elements, efficiency of the design method strongly depends on the actual mechanical properties of materials. The objective of the present contribution is therefore to assess the impact of material variability on the performance of capacity-designed steel-concrete composite moment resisting frames

Existence of solutions in the sense of distributions of anisotropic nonlinear elliptic equations with variable exponent

The aim of this paper is to study the existence of solutions in the sense of distributions for a~strongly nonlinear elliptic problem where the second term of the equation $f$ is in $W^{-1,\overrightarrow{p}'(\,\cdot\,)}(\Omega)$ which is the dual space of the anisotropic Sobolev $W_{0}^{1,\overrightarrow{p}(\,\cdot\,)}(\Omega)$ and later $f$ will be in~$L^{1}(\Omega)$

The SMARTCOCO design guide for hybrid concrete-steel structures

[EN] Standard buildings in steel and in reinforced concrete are constructed by two different industrial sectors with little interaction. Even steel-concrete composite buildings remain designed as steel structures, with a limited benefit of the presence of concrete slabs. For some years however, a more integrated design between both materials is used, merely in high rise and heavy loaded structures. This new trend is not supported by actual standards that give little guidance for the specific arrangements that come from this new practice. The RFCS SMARTCOCO research project is intended to fill these gaps in knowledge and provide design guidance for some composite elements covered neither by Eurocode 2 nor by Eurocode 4 : composite columns or walls reinforced by several fully encased steel sections, reinforced concrete columns reinforced by one steel section over the height of one storey and concrete flat slabs or beams connected to columns or walls by means of steel shear keys. Gaps in knowledge are mostly related to force transmission between concrete and embedded steel profiles. A generic design approach has been developed and then used to design test specimens. The results have been used to calibrate the design proposals. The output is a design guide which complements Eurocode 2 and 4.This paper was developed in the frame of the SMARTCOCO project funded by RFCS, the Research Fund for Coal and Steel of the European Commission, Research grant agreement RFSR-CT-2012-00031 Smartcoco. The companies BESIX and ArcelorMittal are also acknowledged for their involvement in the project.Somja, H.; Hjiaj, M.; Nguyen, QH.; Plumier, A.; Degee, H. (2018). The SMARTCOCO design guide for hybrid concrete-steel structures. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 749-755. https://doi.org/10.4995/ASCCS2018.2018.7023OCS74975

Blurred maximal cyclically monotone sets and bipotentials

Let X be a reflexive Banach space and Y its dual. In this paper we find necessary and sufficient conditions for the existence of a bipotential for a blurred maximal cyclically monotone graph. Equivalently, we find a necessary and sufficient condition on $\phi \in \Gamma_{0}(X)$ for that the differential inclusion $y \in \bar{B}(\epsilon) + \partial \phi(x)$ can be put in the form $y \in \partial b(\cdot, y)(x)$, with $b$ a bipotential.Comment: Revised version, corrections in theorem 6.

Parabolic problems in non-standard Sobolev spaces of infinite order

This paper is devoted to the study of the existence of solutions for the strongly nonlinear $p(x)$-parabolic equation$$\frac{\partial u}{\partial t} + Au + g(x,t,u) = f(x,t),$$where $A$ is a Leray-Lions operator acted from $V^{\infty,p(x)}(a_\alpha,Q_{T})$ into its dual. The nonlinear term $\&gt;g(x,t,s)\&gt;$ satisfies growth and sign conditions and the datum $\&gt;f\&gt;$ is assumed to be in the dual space $V^{-\infty,p'(x)}(a_\alpha,Q_{T})\&gt;.

Efficient implementation of a component-based joint model

This paper deals with a nonlinear analysis of beam-to-column steel joint. The connection uses an end-plate welded to the steel cross-section of a steel-concrete composite beam and bolted to the column flange. The proposed model developed herein combines the knowledge of prior studies that used the component-based approach, on one hand and the Finite Element algorithmsin plasticity, on second hand. The originality of this work is to efficiently take into account possible gaps between the end-plate and the column flange in case of plastic deformation of some components of the joint during the cyclic loading. The numerical investigation aims topredict the behavior of this type of joint in presence of the gap during the cyclic loading