Search

The evaluation of the response of Cold-formed Steel (CFS) drywall partitions under in-plane earthquake loading is one of the open tasks for understanding the impact of nonstructural elements on the seismic performance of constructions, especially when the implementation of performance-based earthquake criteria is required. In this context, the evaluation of the seismic demand on fasteners connecting drywall partitions with the surrounding structures has not been well covered. To overcome this gap, a specific experimental study devoted to evaluate the in-plane seismic demand on Power Actuated Fasteners (PAF) connecting CFS drywall partitions and concrete surrounding elements is presented in this paper. In particular, the experimental activity includes seven quasi-static reversed cyclic tests on full-scale drywall partitions. Parameters under investigation are: type of surrounding connections; type of sliding connection; spacing of PAFs. From global point of view, results showed that the main parameter affecting the seismic response of the drywall partitions was the type of surrounding connections. PAFs connecting both studs and tracks to concrete surrounding elements exhibited elastic behaviour without significant damage in all tested walls with seismic demand equal to 0.50 mm in terms of displacement, 1.9 kN in terms of force per single PAF, 4 kN/m in terms of force per unit length of the wall.

Groups of contiguous unreinforced stone masonry buildings are a common type of housing seen in old European downtowns. However, assessing their response to earthquakes poses several challenges to the analysts, especially when the housing units are laid out in compact configurations. In fact, in those circumstances a modeling technique that allows for the dynamic interaction of the units is required. The numerical study carried out in this paper makes use of a rigid block modeling approach implemented into in-house software tools to simulate the static behavior and dynamic response of an aggregate stone masonry building. Said approach is used to reproduce the results of bi-axial shake-table tests that were performed on a building prototype as part of the activities organized within the Adjacent Interacting Masonry Structures project, sponsored by the Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe. The experimental mock-up consisted of two adjacent interacting units with matching layout but different height. Two rigid block models are used to investigate the seismic response of the mock-up: a 3D model allowing for the limit analysis of the building on one hand, and a 2D model allowing for the non-linear static pushover and time-history analysis on the other. The 3D model was built for the blind prediction of the test results, as part of a competition organized to test different modeling approaches that are nowadays available to the analysts. The 2D model was implemented once the experimental data were made available, to deepen the investigation by non-linear static pushover and time-history analysis. In both models, the stonework is idealized into an assemblage of rigid blocks interacting via no-tension frictional interfaces, and mathematical programming is utilized to solve the optimization problems associated to the different types of analysis. Differences between numerical and experimental failure mechanisms, base shears, peak ground accelerations, and displacement histories are discussed. Potentialities and limitations of the adopted rigid block models for limit, pushover and time-history analyses are pointed out on the basis of their comparisons with the experimental results.

Steel moment resisting frames (MRFs) are drift-sensitive structures and their design is largely influenced by code requirements to limit the lateral displacements and to control the second order effects. Current and next generation of Eurocode 8 recommend different rules to verify the lateral rigidity and resistance of steel MRFs that lead to structures that are substantially different in terms of size of members and overall performance. In order to investigate the influence of the design rules on the seismic behaviour of ductile steel MRFs a parametric numerical study was carried out on 48 structures designed according to Eurocodes as well as US codes, the latter analysed as benchmark, varying the number of storeys, moment resisting spans and seismic intensity. The results of non-linear static and dynamic analyses show that the structures complaint with current Eurocode 8 are the most expensive and characterised by the greater lateral rigidity and resistance, while MRFs designed in accordance with ASCE7 rules have the smaller profiles and the lower overstrength. The frames designed with rules of the latest version of next generation of Eurocode 8 have an intermediate behaviour even if closer to ASCE7-compliant structures. These results are also confirmed by the probability of collapse that is smaller than the minimum value specified by EN1990 for the considered consequence class of the examined buildings.

In recent years, modular construction has been used in low-to medium rise multi-story and even high-rise buildings. Pre-fabrication by off-site manufacture leads to faster and safer construction, improved quality, reduced resources and waste. The research activity summarized in this paper is carried out within the European project INNO3DJOINTS and it aims at developing innovative plug-and-play joints which enable modularity, faster construction and deconstruction. The developed modular construction system is hybrid, whereby tubular columns are combined with cold-formed lightweight steel profiles using plug-and-play connections to provide an efficient structural system. The influence of the type of floor system, the horizontal and vertical load-bearing systems and the type of truss on the structural performance are investigated. The results obtained from numerical analyses allowed optimizing the geometry of the examined hybrid modular system. To highlight its effectiveness and versatility, a case study building was used to compare the proposed hybrid system with other conventional structural solutions.

In view of the development of heavy timber seismic-resistant structures, in the context of modern seismic design approach, a possible solution is to allow the timber structure to dissipate a part of the seismic energy. Since timber is a material with an elastic-fragile behaviour, the dissipative function should be delegated to connections, through plastic deformation of steel connectors. However, joints are primary structural elements, with a crucial role in bearing the design loads. Therefore, the role of seismic energy dissipation should be conveniently assumed by ad hoc devices. In this context, the paper deals with the application of fluid viscous dampers (FVD) to timber frames: FVDs dissipate seismic energy, while timber elements and steel connections remain elastic. Specifically, 2D single-storey structures with dissipative bracing systems, equipped with FVDs, in different configurations, are studied, assuming several rates of possible dampings. Non-linear dynamic time history analyses are performed (SAP2000, v18). Results are discussed showing significant reduction of the structural mass compared to the non-dissipative ones, recentering capability of the structures, high dissipative capacity, simpler elastic connections. The reduction of production and maintenance costs follows. All these involve the efficiency of the structural performance and sustainability under earthquakes.

The paper is related to the assessment of collapse mechanisms of historic masonry structures suffering settlements induced by ground movements. Two numerical strategies are adopted in order to study the influence of the settled zone on the cracking of masonry buildings: a discrete rigid block model and a continuous homogenized model. The first approach provides an estimate of the collapse load and failure pattern of masonry based on the lower bound theorem of limit analysis. The second approach is formulated in the framework of multi-surface plasticity and implemented in a FE code for the path-following non-linear analysis of masonry wall described as continuous anisotropic plate. Several settlement configurations, of masonry walls under moving ground support are investigated and the corresponding failure patterns resulting from the analysis are obtained resulting in local or global failure modes. The results of the two modeling formulations are compared and discussed in order to highlight the features of the two different approaches in the prediction of settlement-induced damage.

The present work is focused on seismic assessment and retrofit of the beam-to-column joints of an existing non-conforming steel building. Refined finite element analyses were performed to investigate the performance of the existing beam-to-column joints under monotonic and cyclic loading conditions as well as the effectiveness of different strengthening interventions. The main features of these joints are the continuity of beams and hollow square columns interrupted at each level and connected by a bolted flange that is strengthened by fillet welds to the tapered flanges of the beams. The results of the finite element simulations show that the existing joints of the examined building exhibit very poor seismic behaviour, mainly due to failure of the welds. On the contrary, the strengthened joints have enhanced response. The comparison between the response of the unreinforced and the various retrofitted joints is described, and the best solutions in terms of both cyclic behaviour and technological feasibility are subsequently identified.

The current edition of Eurocode 8 (EN 1998 (CEN (2004))) does not explicitly cover the earthquake-resistant design of the Lightweight steel (LWS) buildings made with cold-formed steel (CFS) frame. Extensive research has been carried out in the past decade on this topic that provides a solid background for an update of the current provisions and the development of a new edition of the code. As part of the revision process of Eurocode 8, several activities are currently under development. Within this framework, this paper presents a set of design rules for the seismic design of LWS buildings based on background studies carried out at the University of Naples ‘‘Federico II’’. A critical review of the provisions given by international design standards for the seismic design of LWS systems is also presented. The proposed design rules include a set of provisions for achieving the dissipative behaviour of Lateral Force Resisting System (LFRS) and predicting their design strength, together with behaviour factor values and geometrical and mechanical limitations. Different types of LFRS are analysed, namely CFS strap-braced walls and CFS shear walls with steel sheets, wood, or gypsum sheathing. Worked examples are also presented to show the applicability of the proposed design rules on a set of building archetypes. Validation numerical study is performed using both nonlinear static and incremental dynamic analysis approaches. Finally, the collapse performance of the archetypes is assessed following the seismic performance evaluation protocol of FEMA P695.

Nowadays it is known that the European building stock is energy-intensive and insecure: constructions need interventions both to solve performance and structural deficiencies and to reduce the current unsustainable energy waste. An intelligent retrofit for existing structures should offer an intervention integrating all the different performance requirements, such as structural safety, energy efficiency and architectural quality together with optimization of construction processes and costs. To this purpose, it is, therefore, essential to improve knowledge on the composition of the existing building stock . In this work, by analysing and processing the quantitative and qualitative data available from different countries, it has been possible to define an accurate building technologies map showing both the seismic-resistant structures and the envelope systems, the latter to evaluate also the environmental behaviour of buildings in terms of Life Cycle Assessment (LCA) and energetic consumptions. Afterwards, the seismic and climatic characteristics of all the European countries have been considered, so leading towards the definition of zones with different combined hazard conditions. Through all the possible combinations between these seismic and climatic zones, it has been conceived a hazard matrix, where different case studies can be placed aiming at showing potentialities of different retrofit solutions from seismic and energy viewpoints. The investigation of these case studies, which will be analysed in a companion paper, allows to cover all the possible constructions and hazards detected at European level, so to implement an analysis method to be used in every Countries in Europe.

A lightweight steel drywall facade (LWS) is one of the most widely used architectural non-structural components of a building. To account for their effect on the structural performance of buildings, simplified numerical models are proposed to simulate their in-plane response. The model can be easily integrated with building models and, when linked to information about their fragility, allows better estimation of damages in them. Models are calibrated exper-imentally using quasi-static cyclic test results obtained from recent research at the University of Naples "Federico II". Using OpenSees software, models are developed by utilizing a discre-tized spring to simulate the lumped behavior of the walls for each of the eight different con-figurations of the tested façades. A comparison of the experimental and numerical results based on the hysteretic response curves and the cumulative energy dissipated demonstrates the accuracy of the model.

The EC8 design rules and requirements for steel moment-resisting frames (MRFs) mainly address far-field seismic scenarios. However, there are specific issues to account for Near Fault (NF) strong motions that may increase inelastic demand on structural steel members and joints. The latter are usually designed or qualified for far-field earthquakes. Also, the drift displacement is often characterized by severe unidirectional concentration. Another aspect influencing the design of MRFs is the limitation of interstorey drifts, which is often rather restrictive, thus penalizing the design of steel MRFs. The use of ductile energy-efficient claddings can be beneficial to relax the drift limitations, thus allowing to optimize the structural design, reducing the constructional costs, and encouraging the use of more sustainable solutions. To investigate these aspects, an experimental testing program has been planned within the FUTURE project, funded in the framework of the H2020-INFRAIA SERA program. In this project, comprehensive shake table tests were carried out on a two-storey one-bay mock-up equipped with different types of beam-to-column joints and extra ductile non-structural components. This paper illustrates the preliminary experimental results obtained on the bare steel frame equipped with two different types of detachable joints.

Since the ‘80s the use of steel external additive structures is considered one of the most suitable techniques for seismic retrofit of existing RC structures with low dissipative capacity. This structural typology, called exoskeleton, made its first appearance in 2000s in the Japanese and American codes dealing with structural rehabilitation issues. Nowadays, exoskeletons can be implemented without interrupting the building use and they are also used for the integrated retrofit of the building systems. In the present work, after the typological classification of steel exoskeletons in families and the definition of their key project parameters, the application of these systems to the case study of the primary school P. Santini in Loro Piceno, a district of Macerata, has been shown for illustrative purpose.

This paper summarizes the results of experimental tests and finite element simulations aimed at investigating the buckling response of cold-formed square and rectangular hollow columns. The material stress–strain curves of the tested columns have been derived from testing 83 coupons sampled from the flat and corner parts of the cross-sections, along with coupons containing the weld in both longitudinal and perpendicular directions. The experimental stress–strain parameters have been statistically processed to calibrate the parameters of Ramberg-Osgood and Giuffrè-Menegotto-Pinto material models. The cross-sectional geometry and geometric imperfections have been also measured for all tested profiles. The buckling resistance of 21 different pin-ended columns has been experimentally measured in order to examine the influence of the steel grade (both S275 and S355), the normalized slenderness and the shape of cross-section. Finite element simulations of the tested members have been carried out to investigate the influence of residual stresses and out-of-straightness imperfections on the buckling resistance of hollow profiles. The buckling resistance evaluated on the basis of current EN1993-1–1 and the measured properties of the members are in very good agreement with the tested buckling resistances, even though slightly underestimating the resistance of stocky columns. The partial safety factor for flexural buckling has been evaluated using the method given by Annex D of EN 1990 and the results show that the computed average partial safety factor of curve “c” of EN1993-1–1 for cold-formed square and rectangular hollow columns is 0.92.

The Italian earthquakes of the last 15 years highlighted the significant seismic vulnerability of industrial buildings, which represent structural typologies at high risk due to their noteworthy exposure. The paper concerns a parametric study on a class of Italian existing industrial steel buildings designed before 1980 without anti-seismic criteria. The choice of the specific class of warehouses is based on field surveys carried out filling the CARTIS-GL form in the municipality of Cercola, within the district of Naples. These buildings, having different geometrical dimensions, represent one of the most common steel industrial structures widespread in the Italian territory in those years. Five families of structural models, placed into different geographical areas, are designed with the calculation methods of the reference time. The seismic behaviour of the investigated industrial buildings is investigated through non-linear static analyses. The results allow to plot vulnerability curves to be compared to seismic fragility curves derived from literature research. The comparison among curves is useful to estimate the effectiveness of the literature studies, as well as to evaluate the seismic damages suffered by investigated structures under different earthquake levels.

Nowadays, the development of rapid and low-impact structural rehabilitation strategies and techniques is very topical. These prerogatives are essential for the seismic retrofit of industrial buildings, for which the seismic retrofit solution should be selected also accounting for the impact of the interventions on the productive activities. Therefore, a retrofit solution that allows to increase the structural capacity without interfering with the industries production could be preferred with respect to canonical retrofit solutions. In this framework, the aim of the present work is to investigate the efficiency of orthogonal steel exoskeletons for the retrofitting of a steel single-storey industrial building. The investigated case study has poor lateral stiffness and strength. Following a specific design methodology, the various elements of the system were designed, and their efficiency was assessed by means of a non-linear static procedure. Moreover, a local retrofit of the truss to column connections of the MFRs was performed and investigated by means of FEM analysis.

Nowadays the design of seismic-resisting cold-formed steel (CFS) structures are not explicitly covered by European structural standards, even if extensive studies has been carried out in the past decades on this topic and a solid background has long been available. On this basis, with-in the ongoing revision process European structural standards, rules for the seismic design of CFS buildings based on available background studies have been incorporated in 2nd generation of Eurocode 8. Different types of Lateral Force Resisting System (LFRS) are covered, namely CFS strap-braced walls and CFS shear walls with steel sheets, wood, or gypsum sheathing. De-sign rules include a set of provisions for achieving the dissipative behaviour of LFRS, together with behaviour factor values and geometrical and mechanical limitations. A summary of de-sign rules for CFS structures incorporated in 2nd generation of Eurocode 8 and the reference to main background documents are presented in the manuscript.

A lightweight steel (LWS) drywall façade is one of the most widely used architectural non-structural components in a building. This paper presents the results of in-plane quasi-static reserved cyclic tests carried out on 14 different full-scale façades made with LWS framing. The main goal of the study is to investigate the effect of various construction details on the seismic response of the selected facades. The investigated parameters include single or double frame walls, type of sheathing panels, presence of finishing, variation in surrounding constructional elements, absence of track members, type of connection to the surrounding constructional elements, and presence of protrusion. The effect of the construction parameters on the lateral response of the façades was examined in terms of strength, stiffness, force-displacement force–displacement hysteretic response, and damage mechanisms. Therefore, the damage phenomena observed during the tests are reported, associating them with the three damage limit states based on the level of damage. For the definition of seismic vulnerability, the fragility curves for different façade typologies are also presented. Finally, based on the fragility data, the evaluation of seismic performance according to IDR limits for non-structural components given by Eurocode 8 is also performed.

Background: Corrosion propagation mainly occurs due to environmental conditions and to the absence of adequate maintenance. The corrosion propagation affects the structural performances of slender and thin structures, in particular in the case of structure very sensitive to the wind action and its dynamical phenomena, because commonly they are designed with a precise optimization of the stiffness/mass ratio. The static and dynamic wind action represent an immediate safety hazard in the case of structural stiffness and mass reduction due to the corrosion depth. Objective: This paper discusses the dynamics behavior variability due to the corrosion depth propagation for two significant examples of slender and thin structure (i.e. tower and truss roof). Methods: The structures assumed as case of study are made of mild carbon. The corrosion depth variability was estimated based on literature references. The structural natural frequencies and modal shapes are assumed as significant magnitudes to discuss the effect of the corrosion on the structural elements. Results: Results have shown that the corrosion depth gives a significant reduction of frequencies and modification of modal shapes. Conclusion: Results have shown that the corrosion depth affect the structural behavior long before a structural collapse. It suggests that a monitoring must be done to estimate the structure reliability for the Serviceability limit state under Characteristic design loads.

Earthquake standards around the globe are progressing towards adopting an advanced performance based seismic design approach, providing the guidelines for the newer innovative seismic force resisting systems and codifying the seismic performance of already in use structural systems. Gypsum board panels are among one of the many types of panels currently widely used in the Light Weight Steel (LWS) constructions made of the Cold Formed Steel (CFS) frames primarily for sheathing the studs to form an envelope of the building. Contrarily, there choice as the sheathing panel for shear walls resisting the seismic loads in LWS construction is rather limited due the lack of guidelines on their seismic performance in European standards. The work presented here in attempts to bridge this gap by evaluating a suitable value of their behaviour factor, which is one of the significant measures for quantifying the seismic response, through a numerical study performed following the procedures of FEMA P695. A set of fourteen archetypes, which represent a range of design parameters and the building configurations are designed following the capacity design approach and their response is idealized by the nonlinear models. The performance of archetype models is evaluated systematically through the static pushover and the incremental dynamic analysis under a suite of forty-four normalized and scaled earthquake records, representing the probable seismic hazard to the buildings. Finally, by calculating the collapse probability while also considering the uncertainties from various sources, the suitability of trial value of behaviour factor used in the design phase of archetypes is evaluated. Based on the results, it is concluded that a behaviour factor (q) of 2.0 for the CFS shear walls with gypsum board sheathing is appropriate.

The paper deals with the investigation of the seismic behaviour of a masonry church sited in Poggio Picenze (district of L’Aquila) and damaged by the L’Aquila seismic event occurred in Italy on 2009 April 6th. This earthquake, classified as an exceptional event, caused significant damages to about 15,000 buildings. Above all, many of the cultural sites of L’Aquila and the surrounding villages, including churches, palaces and other monuments dating from the Middle Ages and Renaissance, were harmed in a severe way or demolished. The current work is framed in the post-seismic scenario of Poggio Picenze, a small town located about 10 km to the South-East of L’Aquila, and it is aimed at the seismic response assessment of the St. Giuliano church by means of experimental dynamic testing and numerical analyses. Firstly, an experimental campaign based on Ambient Vibration Tests (AVTs), that are non-destructive tests especially applied to historical and monumental buildings for evaluating their modal response, has been performed on the selected construction in the framework of the COST C26 Action as a cooperation activity between the Ss. Cyril and Methodius University of Skopje and the University of Naples “Federico II”. As a result, the method has allowed to obtain the dynamic properties of the examined structure, namely natural frequencies, vibration mode shapes and damping coefficients. The experimental results have been subsequently used to implement a numerical FEM model of the church in the ABAQUS non linear code environment. Linear FEM analysis has been carried out to calibrate the experimental results and a suitable investigation in the nonlinear field has been conducted to predict the post-seismic structural behaviour of the church. Finally, the performed analyses have been of a fundamental importance for both detecting damages into the construction and programming effective retrofitting interventions.

This study aims to increase the knowledge of the seismic behaviour of low-to-medium rise structures, in which the seismic force-resisting system is provided by cold-formed steel strap-braced walls designed as non-energy-dissipating systems. The dynamic response of this system under seismic actions is analysed by performing shake table tests on two reduced-scale (1:3) three-storey two-bay prototypes, that differed in floor typology: steel–concrete floors (Type 1) or floors made of wood-based panels (Type 2). Main outcomes show that the seismic response can be considered as satisfactory, because the system seems to have inherent ductility even without a designated energy dissipating mechanism. In particular, the seismic response was approximately linear for tests having intensity not greater than that assumed for the design, whereas for tests having higher intensities the behaviour deviated from the linearity, with maximum interstorey drift angles greater than 2% without very extensive damage, and in-plane floor rigid behaviour for both prototypes according to the ASCE 7 definition.

Steel three-dimensional lattice trusses are highly efficient technical solutions to cover large spans, especially when single members are not provided with intermediate restraints able to prevent lateral-torsional buckling phenomena. In the present paper, a compound structure made of steel lattice beams and structural glass slabs is proposed for protection of monumental and archaeological sites. Due to both the risk exposure of monumental heritage to be protected and the use of structural glass, the definition of an appropriate design criterion is mandatory in order to avoid brittle collapse mechanisms. The attention is herein paid to the design procedure, with a brief description of basic ideas behind and the main focus on the parametric capacity design of the structure. The proposed procedure, whose validity is quite general, has been herein implemented by linear numerical analyses, which represent the basic step for further refined analysis aimed at erecting a full-scale prototype to be experimentally tested.