Special joint systems for aluminium structures: experimental tests and numerical models

The wide choice of cross-sectional shapes obtainable by extrusion provides the possibility to individuate new joining solution for aluminium profiles. These joints, named “special” or “non-conventional” joints, are very competitive with respect to conventional solutions because of the possibility of rapid execution, optimization of parent material, treatments and machining reduction. For these reasons, the aluminium industry is very interested to enhance the knowledge about the structural behaviour of this joint typology. The work is focused on two different special joint systems: screw ports and bolt-channel joints. In particular, the first joint typology consists in a screw engaged in an open or closed slot of an extruded profile. The latter system consists in a track or channel section profile in which a bolt head, nuts or plates with threaded holes can be located. Special joints are used in several structural and non applications under low and moderate loads such as façades, door and window fixtures. But, in the last years, other structural applications like staircases, floors, pedestrian bridge, industrial furniture and shelves have been developed involving special joints. Nevertheless, very little literature is available for this system and no specifications are provided by aluminium structures codes. The main objective of this work is to overcome the lack of information about the mechanical behaviour of special joints. In order to evaluate the structural behaviour of such joint, a wide experimental campaign has been carried out. In addition, on the basis of experimental results, non-linear finite element models have been developed and calibrated

Evaluation of the Seismic Performance of Light Gauge Steel Walls Braced with Flat Straps

The development of light weight steel structures in seismic area as Italy requires the upgrading of National Codes. To this end, in the last years a theoretical and experimental study was carried out at the University of Naples within the research project RELUIS-DPC 2010-2013. The study focused on all steel design solutions and investigated the seismic behaviour of strap braced stud shear walls. Three wall configurations were defined according to both elastic and dissipative design criteria for three different seismic scenarios. The lateral in-plane behavior of these systems were evaluated by 12 tests performed on full-scale CFS strap-braced stud wall specimens with dimensions 2.4 m x 2.7 m subjected to monotonic and reversed cyclic loading protocols. The experimental campaign was completed with 17 tests on materials, 8 shear tests on elementary steel connections and 28 shear tests on strap-framing connection systems. On the basis of the experimental results, and taking into account the AISI S213 provisions, behaviour factors were evaluated. This paper provides the main outcomes of the experimental tests on walls and behaviour factors evaluation

Experimental Tests for the Seismic Response Evaluation of Cold-Formed Steel Shear Walls Sheathed with Nailed Gypsum Boards

The European project named Energy Efficient LIghtweight-Sustainable-SAfe- Steel Construction (Project acronym: ELISSA) is devoted to the development and demonstration of cold-formed steel (CFS) modular systems. In particular, these systems are nano-enhanced prefabricated lightweight steel skeleton/dry wall construction with improved thermal, vibration/seismic and fire performance, resulting from the inherent thermal, damping and fire spread prevention properties. The different building performances are studied and improved by means of experimental and numerical activities organized on three scale levels: micro-scale, meso-scale and macro-scale. In particular, the evaluation of the seismic performance is carried out at the University of Naples by means tests on connections (micro), seismic-resistant systems (meso) and full-scale two stories house prototype (macro). From a structural point of view, the system is a sheathed-braced CFS solution, in which the seismic resistant elements are made of CFS stud shear walls laterally braced by gypsum-based panels. In the adopted solution, the sheathing panels are attached to the CFS frame by means of ballistic nails, whereas clinching points are used for steel-to-steel connections. The present paper illustrates the results of meso-scale tests performed on four full scale shear walls, in which the influence of the aspect ratio, the type of loading and the effect of finishing was investigated

Assessment of the design criteria for concentric V-braced steel structures according to Italian and European codes

The critical review of design methodologies provided by the NTC2008, in agreement with the European seismic code (Eurocode 8) for steel Concentrically Braced Frames with chevron (or inverted V) diagonals (CBF-V), carried out by deepening the seismic behaviour of such typical steel seismic resistant structures, aims to provide more efficient design criteria able to ensure adequate safety levels under seism. As reference case studies, common structural configurations of CBF-V are designed according to the NTC2008 provisions. Each case study is designed through both the Linear Static (LS) and Dynamic (LD) analysis. For braces either Circular Hollow Sections (CHS) or HE profiles are used. General critical issues have been evidenced in the design process. The seismic performance of investigated structures is evaluated by non-linear static analyses, in order to appraise the most relevant behavioural issues, like the behaviour factor, the failure modes and the effectiveness of the capacity design criteria. A discussion on the obtained results has allowed to point out the pros and cons of the current design approach

Seismic response of Cfs strap-braced stud walls: Experimental investigation

The development of light weight steel structures in seismic area as Italy requires the upgrading of National Codes. To this end, in the last years a theoretical and experimental study was undertaken at the University of Naples within the Italian research project RELUIS-DPC 2010–2013. The study focused on “all-steel design” solutions and investigated the seismic behavior of strap-braced stud walls. Three typical wall configurations were defined according to both elastic and dissipative design criteria for three different seismic scenarios. The lateral in-plane inelastic behavior of these systems was evaluated by twelve tests performed on full-scale Cold-formed strap-braced stud wall specimens with dimensions 2400×2700 m2 subjected to monotonic and reversed cyclic loading protocols. The experimental campaign was completed with seventeen tests on materials, eight shear tests on elementary steel connections and twenty-eight shear tests on strap-framing connection systems. This paper provides the main outcomes of the experimental investigation. Furthermore, the design prescriptions, with particular reference to the behavior factor and the capacity design rules for these systems, have been proved on the basis of experimental results

Seismic response of Cfs strap-braced stud walls: Theoretical study

The use of cold-formed steel (CFS) profiles in low-rise residential buildings has increased in European construction sector. The reason of this interest is related to potentialities offered by this constructive system, which are the high structural performance, lightness, short construction time, durability and eco-efficiency. Nevertheless, the current structural codes, such as Eurocodes, do not provide enough information about the seismic design of this structural typology. In an effort to investigate the seismic response of CFS structures, a theoretical and experimental research has been carried out at University of Naples Federico II, with the main aim to support the spreading of these systems in seismic areas. This study focuses on an “all-steel design” solution in which strap-braced stud walls are the main lateral resisting system. In the present paper the outcomes of theoretical phase are shown with the aim of defining the criteria for the seismic design of such structures. In particular, a critical analysis of the requirements for CFS systems provided by the American code AISI S213 has been carried out by comparing it with those given by Eurocodes for traditional braced steel frames

Seismic response assessment of architectural non-structural LWS drywall components through experimental tests

A research project was conducted at University of Naples “Federico II” over the last few years with the aim to give a contribute to overcome the lack of information on seismic behaviour of architectural non-structural lightweight steel (LWS) drywall components, i.e. indoor partition walls, outdoor façades and suspended continuous ceilings. The tested non-structural components were made of LWS frames sheathed with gypsum-based or cement-based boards. The research activity was organized in three levels: ancilliary tests, component tests and assembly tests. Ancilliary tests were carried out for evaluating the local behaviour of partitions, façades and ceilings. Component tests involved out-of-plane quasi-static monotonic and dynamic identification tests and in-plane quasi-static reversed cyclic tests on partitions. Finally, the dynamic behaviour was investigated through shake table tests on different assemblages of partitions, façades and ceilings. The study demonstrated that the tested architectural non-structural LWS drywall components are able to exhibit a very good seismic behaviour with respect to the damage limit states according to the IDR limits given by Eurocode 8 Part 1. The current paper describes the complete experimental activity within the project

Shake table tests of a full-scale two-story sheathing-braced cold-formed steel building

Shake table tests are particularly indicative to assess dynamic properties and seismic response under earthquakes in the case of a new building structure. In last years the University of Naples was involved in the research project named ‘‘Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction” (Project acronym: ELISSA), which was devoted to the development and demonstration of enhanced prefabricated lightweight CFS skeleton/dry wall constructions with improved antiseismic properties. Within the ELISSA project, in order to evaluate the global building seismic response, shake table tests on a fullscale two-storey building, named ‘‘ELISSA mockup”, were carried out. The mockup was tested in two different conditions. In the first condition the mockup included mainly structural components of walls, floors and roof, whereas in the second condition it was completed with all nonstructural components. This paper presents the testing program and the obtained results in terms of dynamic identification (fundamental period and damping ratio) and earthquake performance (global lateral response, building drift, acceleration amplification, diaphragm response, and observed damage)

Seismic response of CFS shear walls sheathed with nailed gypsum panels: Experimental tests

Among the several available building systems, constructions involving cold-formed steel (CFS) profiles represent an efficient and reliable solution. These systems are very suitable to be used in pre-fabricated modular constructions, thanks to their lightness and possibility to automate the building process. In a framework of the European project ELISSA (Energy Efficient LIghtweight-Sustainable-SAfe-Steel Construction), which was devoted to the development and demonstration of CFS modular systems, an experimental campaign aimed at investigating the seismic response of this system was carried out at University of Naples Federico II. Specifically, the studied system was a sheathing-braced CFS solution, in which the seismic resistant elements were made of CFS stud shear walls laterally braced with gypsum-based panels. The sheathing panels were attached to the CFS frame by means of ballistic nails, whereas clinching points were used for steel-to-steel connections. This paper shows the results of tests performed on shear walls and on the relevant ballistically nailed panel-to-steel connections. In particular, four full scale shear walls were tested, in which the influence of the aspect ratio, the type of loading and the effect of finishing was investigated