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Elementele compuse realizate din profile de otel formate la rece sunt elemente structurale eficiente, atractive din punct de vedere al consumului de material dar si pentru usurinta de punere in opera. Mai mult, astfel de elemente compuse mai prezinta si avantajul unei manipulari usoare datorita greutatii reduse a componentelor. Imbinarea dintre componentele grinzii compuse poate fi usor realizata cu suruburi autoforante, insa dezvoltarea proceselor de sudare a condus la alte solutii de imbinare eficienta precum sudarea electrica prin presiune in puncte. In cadrul Departamentului de Constructii Metalice si Mecanica Constructiilor al Universitatii Politehnica Timisoara, s-a studiat experimental o solutie tehnologica noua pentru grinzi cu inima din tabla cutata, constand din profile C formate la rece, tabla cutata pentru inima, si tabla plana la ambele capete cu rol de panouri de forfecare. Partile componente au fost imbinate initial prin intermediul suruburilor autoforante, ulterior, solutia initiala fiind imbunatatita prin utilizarea sudurii electrice prin presiune in puncte, care elimina suruburile si reduce cantitatea de manopera. Lucrarea prezinta modelul numeric calibrat pe baza rezultatelor experimentale precum si un studiu pentru a identifica influenta parametrilor care guverneaza capacitatea acestor elemente, si anume: (1) imperfectiuni initiale, (2) numarul si distanta dintre punctele de sudura, (3) grosimea talpilor, (4) grosimea inimii cutate, (5) grosimea panourilor de forfecare. Rezultatele studiului parametric au aratat ca grinda compusa cu inima din tabla cutata are o capacitate portanta influentata major de stabilitatea componentelor si mai putin afectata de configuratia si numarul punctelor de sudura. Din punctul de vedere al rigiditatii, comportarea favorabila a grinzii a fost data de pozitia punctelor de sudura.

Steel-Earth project aims at distributing among technicians, engineers, design companies and standardization bodies the results of three past RFCS projects (Steel-Retro [3], Opus [2] and PrecaSteel [1]), providing useful tools for the design and for the retrofit of existing buildings. Technical documents and practical applications to case studies, regarding design of steel and composite steel/concrete buildings and innovative steel-based techniques for the retrofit of existing r.c. and masonry constructions, have been elaborated and collected into a volume distributed during the final workshop of the dissemination project. Pre-normative and background documents concerning the design of steel and composite structures and the rehabilitation of existing constructions have been prepared. A lot of attention has been paid to the analysis of the influence of overstrength factors on the seismic design of steel and composite structures. The prepared documents have been distributed to the attending people and to the members of WG 2 (CEN/TC 250/SC 8/WG 2 “Steel and Composite Structures”) during the final workshop of the project. Technical sheets, working examples and background documents have been translated into several languages (German, French, Italian, Romanian and Greek) and are free available on the website of the project (https://www.steelconstruct. com/site/), where information regarding Steel-Earth are also presented. 11 Workshops in Italy, Greece, Germany, Belgium, Portugal, Spain and Romania and 5 conferences in Emilia-Romagna have been organized, as well as 2 practical courses for engineers and academic people in Pavia (Italy). Flash-drives with the technical documents and applications elaborated in Steel-Earth have been distributed to the attending people.

To perform geometrically and materially nonlinear analyses including imperfec-tions for steel beam lateral torsional buckling, the size and shape of the geometric imperfec-tion can be obtained from EN 1993-1-1. The shape is prescribed as an initial bow along the weak axis of the section, excluding torsion of the cross-section. The shape of the imperfection can alternatively be taken equal to the lateral torsional buckling mode, including torsion. Sev-eral tables and formulas exist to determine the size of the imperfection. Different imperfection approaches were applied in finite element simulations to evaluate the lateral torsional nonlin-ear buckling resistances and to compare them to the results obtained with design rules.

Clause 6.2.8 of EN 1993-1-1 covers the design rules on bending-shear resistance, taking presence of shear into account by a reduced yield stress for the shear area. Numerical research on bending-shear interaction by means of the Abaqus Finite Element modelling software is presented. The numerical model is validated against the experimental results. A material model based on various tensile test coupons was used incorporating the actual mate-rial properties within the tested cross-section. Strong axis three-point bending tests were simulated by means of continuum solid elements. Good agreement was achieved between numerical and experimental result, both are compared with the EN 1993-1-1 design rule.

Conventional seismic design philosophy is based on dissipative structural response, which implicitly accepts damage of the structure under the design earthquake and leads to significant economic losses. Repair of the structure is often impeded by the permanent (residual) drifts of the structure. The repair costs and downtime of a structure hit by an earthquake can be significantly reduced by adopting removable dissipative members and providing the structure with re-centring capability. These two concepts were implemented in a dual structure, obtained by combining steel eccentrically braced frames (with removable bolted links) and moment resisting frames. The bolted links provide the energy dissipation capacity and are easily replaceable, while the more flexible moment resisting frames provide the necessary re-centring capability. The paper presents the results of a large scale experimental program on a dual eccentrically braced frame with replaceable links performed at the European Laboratory for Structural Assessment (ELSA) at the Joint Research Centre in Ispra within the framework of Transnational Access of the SERIES Project. The objectives were to validate the re-centring capability of dual structures with removable dissipative members, assess overall seismic performance of dual eccentrically braced frames and obtain information on the interaction between the steel frame and the reinforced concrete slab in the link region. Pre-test numerical simulations were performed in order to assess the response of the structure under different levels of the seismic input, as well as to establish the optimal sequence of link removal and replacement. The general set-up of the experimental mock-up, instrumentation, the test sequence, and preliminary test results are presented., JRC.G.4-European laboratory for structural assessment

Different strategies can be employed in order to reduce damage to structures under moderate to strong earthquakes. The most radical solutions are base isolation and various implementations of active and semi-active structural control. Other strategies rely on supplemental damping conferred to the structure through various devices based on viscous, friction, or yielding dampers. More or less efficient for reduction of structural damage, all these solutions have the disadvantage of requiring specialised knowledge at the design stage and during erection, need for careful maintenance and high initial cost., JRC.G.4-European laboratory for structural assessment

Conventional seismic design philosophy is based on dissipative structural response, which implicitly accepts structural damage under the design earthquake load thus leading to significant economic losses. Different strategies can be employed in order to reduce damage to structures under moderate to strong earthquakes such as base isolation and various implementations of active and semi-active structural control. Other strategies rely on supplemental damping conferred to the structure through various devices. These solutions require specialized knowledge at the design stage and during erection, careful maintenance and high initial cost. Another option constitutes a conventional design with replaceable dissipative members, easy to substitute even after strong earthquake, and thus reducing the repair costs. A system with removable dissipative elements has to fulfil two requirements to be efficient. Firstly, inelastic deformations should occur in removable elements only. Secondly, the damaged dissipative elements must be replaceable. Replacing the elements is more efficient if the structure does not have large permanent deformations. These two concepts were implemented in a dual structure, obtained by combining steel eccentrically braced frames (with removable bolted links) and moment resisting frames. The bolted links provide the energy dissipation capacity, while the moment resisting frames provide the necessary re-centering capability, JRC.G.4-European laboratory for structural assessment

Structural systems that aim at reducing structural damage by isolating plastic deformations in removable or "repairable" elements, and have the ability to return to the initial undeformed shape after an earthquake have received much attention recently. One of the solutions applicable to steel moment-resisting frames relies on post-tensioned beam to column joints [1] and column bases [2]. Other solutions having the same performance objectives use beam to column joints assembled with shape memory alloy connecting devices [3]. Vargas and Bruneau [4] investigated a design approach aiming to concentrate damage on removable and easy to repair structural elements ("structural fuses"), with the main structure designed to remain elastic or with minor inelastic deformations. A systematic procedure was proposed to design buildings with metallic structural fuses. Kiggins and Uang [5] showed that even if buckling restrained braced frames exhibit a favourable energydissipating mechanism, the low post-yield stiffness of the braces leave the system vulnerable to unfavourable behavioural characteristics such as large permanent drift. The potential benefit of using buckling-restrained braces in a dual system to minimize permanent deformations was investigated and shown to reduce significantly residual story drifts., JRC.G.4-European laboratory for structural assessment

The repair costs and downtime of a structure hit by an earthquake can be significantly reduced by adopting removable dissipative members and providing the structure with re-centring capability. These two concepts were implemented in a dual structure, obtained by combining steel eccentrically braced frames (with removable bolted links) and moment resisting frames. The bolted links provide the energy dissipation capacity and are easily replaceable, while the more flexible moment resisting frames provide the necessary re-centring capability. The solution will be validated by full-scale pseudo-dynamic test of a three-storey model of a steel structure with re-centring capability at the European Laboratory for Structural Assessment (ELSA) at the Joint Research Centre in Ispra within the framework of Transnational Access of the SERIES Project financed by the European Commission. The paper presents pre-test numerical simulations performed on a dual eccentrically braced frame with replaceable links. Both local performance of bolted links and overall system performance were investigated., JRC.G.4-European laboratory for structural assessment

Previous studies (Dubina et al., 2010; Nagy, 2006) reported the results of experimental and numerical simulation programs carried out in research centre of “Politehnica” University of Timişoara on joints and full-scale pitched roof cold-formed steel portal frames of back-to-back lipped channel sections with bolted joints, in order to evaluate the joint performance and the structural stability performance of these structures. Further research have been started to study the possibility to extend the obtained results for low rise multi storey cold-formed steel framed structures. The study will focus on particular structural solutions and joint typologies, suitable for such a type of structures. The paper summarizes the state of the art on application of cold-formed steel structural solutions for low and medium rise buildings and the preliminary study performed by one of the authors, in order to find adequate structural solutions for different Romanian seismic regions, using cold-formed steel sections. Based on these results, the proposed research program will use finite element modeling to calibrate virtual models, to evaluate the structural performance of proposed bolted joints, suitable for multi storey cold formed steel framed structures.

In recent years important research activity was undertaken to determine the earthquake performance of light gauge steel house structures. Usually, studies approach the problem of earthquake performance trough experiments on wall panels conducted either under monotonic or cyclic loads. All studies underline the overwhelming importance that the behavior of the connections has in determining the overall performance of the wall panels. However, these studies focused on the global behavior of the panel and did not try to characterize the behavior and provide design criteria for connections, as components of the structural system. The present paper attempts to fulfill this gap.