Search

Spatial truss beams are an extremely efficient typological solution for covering large spans, especially in the cases where members do not have lateral restraints capable of preventing flexural–torsional buckling phenomena In this study the structural behaviour of innovative steel 3D lattice beams in combination with structural glass slabs, used as roof decks, is investigated for protection of historical assets and archaeological sites. After a brief description of the novel structural system, the attention is focused on the experimental activities carried out for the mechanical characterization of both material and structure. In particular, four-point bending tests are carried out on full-scale prototypes in order to both validate the design procedure and calibrate numerical models useful to extend the achieved results through Geometrically and Materially Nonlinear Analysis with Imperfections (GMNIA analysis). • Four-points bending tests on innovative 3D built-up lattice beams were performed under monotonic loads. • The prototypes showed a ductile behaviour with full yielding of the bottom chord. • The experimental response evidenced the robustness of the design criteria developed by the authors for sizing purposes. • The experimental study allowed for the evaluation of the reliability of some capacity models implemented in Eurocode 3 to predict the elastic and plastic behaviours of systems like those under investigation. [ABSTRACT FROM AUTHOR]

The catastrophic effects of recent earthquakes around the world have highlighted the vulnerability of civil buildings; in Europe, most of the existing buildings were built after World War II and since they have largely exceeded their useful life, are characterized by a high vulnerability linked both to the durability of the materials and to the lack of seismic provisions in design. The current trend in constructional field is to design interventions aimed at the seismic and energy improvement of these structures jointly, in order to achieve a sustainable and integrated retrofit intervention. To this aim, the use of 2D orthogonal steel exoskeletons for the seismic strengthening represents a suitable solution, providing at the same time an enhancement in thermal insulation, through a 'double-skin' solution. Due to the growing interest in the design of steel exoskeleton interventions, a detailed dynamic characterization of this external strengthening solution is needed. In this framework, the present work, aims to investigate the effectiveness of the investigated strengthening solution by means of bi-directional non-linear dynamic analyses. Extensive numerical analysis was carried out. The selected case-study is an Italian existing pre-1980 s RC frame building located in Mugnano di Napoli (NA, Italy), which is a medium-high seismic hazard site in Italy (peak ground acceleration equal to 0.156 g). Two alternative strengthening solutions were numerically investigated by means of non-linear time-history and incremental dynamic analyses performed applying fifteen bidirectional ground motions on three-dimensional numerical models. The results of the dynamic non-linear analyses allow to quantify more appropriate performance indicators, both in terms of expected demand and overall collapse capacity, useful for the development of optimization strategy and design of exoskeleton system. The results highlighted that both the investigated strengthening scenarios allow to increase the stiffness of the existing building and allow it to meet the current code safety requirements reducing also the residual inter-storey drift. The obtained results are not strictly related to the investigated case study, but can be extended to all the structures retrofitted that follows the presented design procedure. • The catastrophic effects of recent earthquakes around the world have highlighted the vulnerability of civil buildings. • Due to the interest in the design of exoskeleton, a dynamic characterization of this strengthening solution is needed. • The strengthening of an existing RC structure with EXO-S-2D placed orthogonally to the building façade is presented. • The efficiency of a displacement-based design procedure is validated by means of static and dynamic non-linear analyses. • The results of the dynamic non-linear analyses allow to quantifyperformance indicators of the strengthened intervention. [ABSTRACT FROM AUTHOR]