G. De Matteis

Seismic response of MR steel frames with low-yield steel shear panels

Non-linear dynamic analyses examining the seismic response of moment resisting (MR) steel frames enhanced with low-yield steel shear panels are presented. Shear panels, which act as damping and stiffening devices, are schematised as equivalent bracing elements having a suitable hysteretic behaviour. For this purpose, an analytical model is set up and calibrated on the basis of available experimental tests. A parametric analysis is therefore carried out varying several parameters of shear panels, namely strength, stiffness, ductility and hysteretic behaviour, aiming at determining those factors having the major impact on the seismic response of the frame. Obtained results show that the considered design procedure is really effective and convenient, low-yield steel shear panels providing an apparent reduction of storey deflection and damage level of the primary structure.

Low yield metal shear panels as an alternative for the seismic upgrading of concrete structures

The paper addresses the problem of seismic retrofitting of existing concrete structures through an innovative methodology based on low yield metallic shear panels. These panels are introduced in specific places in the concrete structure enhancing its strength and stiffness. However, the most important improvement concerns the energy dissipation capacity of the retrofitted structure. The paper presents a preliminary design methodology within the performance based design framework and details for the realization of the intervention. Elaborated non-linear finite element models are used in order to verify the quality of the results obtained from more simple models used in everyday engineering practice.

T-stub aluminium joints: influence of behavioural parameters

Abstract This paper is focused on the behaviour of aluminium alloy T-stub joints. The analysis is developed by means of finite element method simulation carried out with the non-linear code ABAQUS. The procedure has been accurately calibrated on the basis of some existing experimental results. The analysis, which has been referred to several behavioural parameters, has shown that, contrary to steel joints, the collapse mechanisms cannot be clearly defined, owing to a more gradual transition observed between each other. This is mainly a consequence of the stronger influence of the alloy hardening features.

Seismic analysis of MR steel frames based on refined hysteretic models of connections

Abstract Evaluation of seismic performance of moment-resisting (MR) steel frames is usually carried out assuming the elastic-perfectly-plastic type of hysteresis model for plastic zones (in particular for beam-to-column connections). This type of model is associated with a conventional available ductility, giving an indication of the maximum deformation beyond which strength degradation is likely to occur. This methodology leads to conservative results and the elastic-perfectly-plastic type of hysteresis model is certainly adequate in obtaining reliable information on deformation when the above ductility limits are not exceeded. However, the safety of the frame at ‘collapse’ remains unknown. The analyses presented in this paper show that safety margins against global collapse of the structure can be predicted only by considering more realistic hysteresis behaviour, i.e. using mathematical models able to take account of strength degradation and pinching phenomena. Moreover, it is shown that the design of conventional steel building systems according to the European seismic code may lead to over-resistant structures, due to the limitation on inter-storey drift angles for non-structural damage control under frequent earthquakes. It is also noticed that this result is inevitable, owing to the indications provided by Eurocode 8 in terms of both prescribed inter-storey drift limits and assumed base shear-force demand under frequent earthquakes.

Seismic Analysis of Mr Steel Frames Based on Refined Hysteretic Models of Connections

Publisher Summary Evaluation of the seismic performance of moment resisting steel frames is usually carried out assuming the elastic-perfectly-plastic type of hysteresis model for plastic zones. This type of model is associated with conventional ultimate plastic rotations giving indication of the maximum deformation beyond which strength degradation is likely to occur. This methodology leads to conservative results, and the elastic-perfectly-plastic type of hysteresis model is definitely adequate to obtain reliable information on deformation demands when the maximum values presented in this chapter are not exceeded. However, the safety of the frame at collapse remains unknown. The analyses presented in the chapter show that safety margins on the global collapse of the structure can be predicted only by considering more realistic hysteresis behaviors. Finally, aiming at obtaining more rational structures—that is, structures satisfying both the serviceability and ultimate limit states with the same level of confidence, some possible solutions are proposed and discussed in the chapter.

Experimental response of top and seat angle semi-rigid steel frame connections

The current study is concerned with the structural response of typical semi-rigid steel beam-to-column joints. In particular, the behaviour of bolted cleat angle connections is investigated under different loading conditions, both monotonic and cyclic loading being considered. Besides, aiming at assessing the susceptibility of the analysed connection typology to low-cycle fatigue, the latter has been referred to both constant and variable amplitude deformations. Therefore, 15 full-scale tests have been carried out by comparing the performance of specimens with reference to three different sizes of column member as well. Obtained results are provided in terms of moment-rotation relationship, dissipated energy and strength degradation per cycle. As expected, outcomes show that the main sources of inelastic deformation are located into cleat angles, which constitute the most influential component. As a consequence, the column size has a limited effect on the whole hysteretic response of the joint, while results appear to be strongly dependent on the applied deformation history.RésuméDans cet article, on étudie le comportement structurel d’un type de liaisons poutre-poteau semi-rigides. La poutre et le poteau sont liés par des cornières. Les procédures de chargement que l’on a suivies incluent plusieurs cas de chargements monotones et cycliques. Pour déterminer le comportement de ces liaisons à la fatigue (petit nombre de cycles et grandes déformations plastiques), on a adopté plusieurs procédures de déplacements à amplitude constante. L’étude a été appliquée à trois types de poteaux. Comme on a considéré cinq liaisons différentes pour chaque type de poteau, un total de quinze liaisons ont été essayées. Les comportements étudiés ont été représentés sous forme de diagrammes moment—rotation, de l’énergie dissipée et de la dégradation de rigidité, et ont été comparés entre eux. Comme prévu, la déformation plastique a eu lieu surtout dans les cornières, lesquelles sont donc les éléments les plus importants de la liaison. La dimension de la section du poteau influence très peu le comportement histérétique de la liaison, lequel, d’autre part, dépend des déplacements précédemment appliqués.

Experimental and Numerical Modal Identification of the Fossanova Gothic Cathedral

This paper focuses on the dynamic behaviour of the Fossanova cathedral (Latina, ITALY), which represents a magnificent example of pre-Gothic style church, whose structural typology is largely present in the Mediterranean area, especially in many Countries characterised by a High-Medium seismic hazard. In particular, within the European research project PROHITECH, aiming at investigating the seismic vulnerability of such a structural typology, experimental and numerical analyses have been carried out. Firstly, detailed investigations have been devoted to the identification of the geometry of the main constructional parts as well as of the mechanical features of the constituting materials of the cathedral. Then, both Ambient Vibration Tests (AVT) and Numerical Modal Identification analyses by Finite Element Method (FEM) have been applied, allowing the detection of the main dynamic features. Finally, a refined FEM model reproducing the dynamic behaviour of the cathedral by using scaled physical quantities according to the Buckingham theorem has been developed. In fact, the present study has to be intended as a preliminary activity devoted to se up a shaking table test on a reduced scale physical model of Fossanova cathedral, which will be shortly carried out at the IZIIS laboratory (Skopje, Macedonia).

RC structures strengthened by metal shear panels: experimental and numerical analysis

Metal shear panels (MSPs) may be effectively used as a lateral load resisting system for framed structures. In the present paper, such a technique is applied for the seismic protection of existing RC buildings, by setting up a specific design procedure, which has been developed on the basis of preliminary full‐scale experimental tests. The obtained results allowed the development of both simplified and advanced numerical models of both the upgraded structure and the applied shear panels. Also, the proposed design methodology, which is framed in the performance base design philosophy, has been implemented for the structural upgrading of a real Greek existing multi‐storey RC building. The results of the numerical analysis confirmed the effectiveness of the proposed technique, also emphasising the efficiency of the implemented design methodology.

Contributing Effect of Cladding Panels in the Seismic Design of Mr Steel Frames

Publisher Summary This chapter deals with the influence of lightweight cladding panels on the seismic design of multistory steel moment resisting frames. To this purpose, the possibility to profit of the contributing effect of shear walls on the serviceability limit state of the structure is analyzed. A new design procedure is discussed. It is essentially based on the separation between strength and drift requirements. Therefore, the stiffening diaphragm action provided by cladding panels is taken into account to increase the lateral stiffness of the bare frame, once the latter has been designed according to resistance and ductility requirements only. The chapter also discusses three different structural typologies—namely, two-, five- and seven-story frames. ; Different strategies to choose cladding panels characteristics are considered. Obtained results show that the proposed procedure leads to more rational and economic solutions, allowing for an important reduction of structural member sizes. Besides, it is noticed that obtained requirements for cladding panels in terms of both strength and stiffness are never prohibitive, their being in the same range of those provided by commercial products.

Influence of Welding on the Stability of Aluminium Thin Plates

The effect of welding on the local buckling of aluminium thin-walled sections is focused in this paper. With regard to a round-house type law material and by considering different hardening parameters as well as plate slenderness, the effect of welding in terms of geometrical imperfections, residual stresses and heat affected zones are analysed by means of a finite element analysis. The obtained results emphasise the influence of welding on the strength of slender plates, which has been only partially evidenced by experimental analyses. Besides, the comparison with the new EC9 approach allows to check the reliability of the design curves with respect to such a phenomenon.