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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.

This paper investigates the performance of extended stiffened end-plate bolted beam-to-column joints subjected a column loss scenario by means of finite element simulations. An advanced numerical model was developed, and its effectiveness was validated against the experimental results. The influence of the bolt strengthening on the column loss action was investigated changing the grade of bolts. The results showed that the joint performance under column loss scenario are deeply related to the development of the catenary action that depends from the connection ductility; therefore increasing the bolt material strength will provide beneficial effects on the joint capacity under the column loss.

Steel moment resisting frames (MRFs) compliant with EN1998-1 are generally overdesigned in order to satisfy the requirements for lateral deformability and P-Delta effects. On the contrary, the North American codes (e.g. ASCE7) give different rules for P-Delta effects. The current draft version of the amended EN1998-1-1 introduces a different methodology to account for the structural lateral displacements. In this paper static non-linear analyses were carried out to evaluate the effectiveness of the new EC8 provisions with respect to the former version of EC8 and the current ASCE7. The results show that the structures designed according to the latest draft version of the EN1998-1-1 and those compliant with the North American code exhibit similar behavior.

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 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.

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.

Different types of seismic dampers are available on the market of constructions. The more effective solutions are characterized by (i) stable and predictable response, (ii) localisation of demand into the dampers minimizing the post-earthquake damage in easily replaceable parts. Friction dampers typically satisfy both requirements. These dampers are very versatile since they can be equipped in different structural arrangements. One of the most promising solutions is their application in the moment-resisting beam-to-column joints where they can effectively dissipate the seismic energy and limit plastic deformations into easily replaceable elements. Furthermore, their resistance and deformation capacity can be easily designed without interfering with the structural geometry, thus allowing the standardisation of friction connections for a wide range of beam-to-column assemblies. The current work presents a parametric study based on finite element (FE) simulations of steel beam-to-column joints equipped with a set of five predefined friction dampers specifically conceived to cover the most representative range of profiles used in Eurocode-compliant multi-storey moment resisting frames. The FE models were calibrated against recent experimental tests performed by the authors in a former study. The analyses were aimed at extending these experimental results, investigating the local behaviour of the dampers and the connections as well as the influence of member scaling on the monotonic and hysteretic behaviour of each assembly. The results confirm that the non-linear performance of connections equipped with friction dampers is almost independent on the dimensions of the connected profiles, and it is fully replicable within a predefined range of geometries

Seismically pre-qualified beam-to-column joints guarantee large ductility in seismic scenarios thanks to the effectiveness of the design rules and technological requirements that are devoted to avoiding the failure of brittle components (i.e., bolts and welds). However, their performance under different severe actions like those induced by fire has not been properly investigated. Therefore, a parametric study based on finite element simulations has been carried out with the aim to verify the effectiveness of local details of seismically prequalified joints under fire. Finite element analyses were carried out on beam-to-column assemblies sub-structured from a reference archetype building accounting for both material and geometrical imperfections. The bolts&rsquo, internal actions were monitored in all the investigated specimens varying the applied vertical loads. The results show that the seismic design rules adopted to size the bolts are effective to resist the large increase in shear forces in the bolts occurring under fire. Thus, the investigated joints provide satisfactory ductility and rotation capacity at high temperature preventing the failure of bolts, further analysis could be conducted to investigated the fire performance of the investigated joints in a seismic scenario.

The bolts and their arrangement strongly influence stiffness, strength and ductility of T-Stub connections. Preloaded bolts are typically adopted to improve the stiffness and limit the opening of the connection under serviceability conditions. EN1993-1-8 allows using two types of high resistance preloaded bolts, namely the German HV (acronym of Hochfeste Bolzen mit Vorspannung, which is the German for High Resistance bolts for pretension and the British/French HR (acronym of High Resistance) without making any distinction. However, the tensile failure modes of these bolts are different (i.e. nut stripping for HV and shank necking for HR) and may affect the ultimate tensile response of the T-Stub connections with weak bolts (e.g. failure mode type 2 and 3). Furthermore, despite the effects of geometrical non-linearities at large deformations are not specifically addressed in current codes, the membrane action developing in the flange and the shear force and bending moment in the bolt may influence the reserve of ductility of the T-Stub that plays an important role in case of seismic and robustness scenarios. In addition, the presence of initial imperfections (e.g. the misalignment of the web as respect to the bolts and the flange bowing) can influence the non-linear behaviour of the connection. The influence of all these aspects on resistance and ductility of T-Stub connections are investigated by means of both experimental monotonic tests and parametric finite element analyses. On the basis of the obtained results, design rules are discussed with the aim to guarantee extra ductility of T-Stub connections.

The seismic response of steel moment resisting frames (MRFs) is influenced by the behavior of joints. Within the ongoing research project &ldquo, FUTURE&rdquo, (Full-scale experimental validation of steel moment frame with EU qualified joints and energy efficient claddings under Near fault seismic scenarios), shake table tests will be carried out on a two-story one bay MRF equipped with different types of prequalified beam-to-column joints. In order to design the experimental campaign, preliminary numerical simulations have been carried out to predict the seismic performance of the experimental mock-up in terms of distribution of damage, transient and residual interstory drifts. In this paper the main modeling assumptions and the results of the seismic analyses are shown and discussed. In particular, the response of joints was systematically investigated by refined finite element (FE) simulations and their behavior was taken into account in the global structural performance by means of both concentrated plastic hinge and distributed plasticity models. Both static and dynamic non-linear analyses show in which terms the type of models for plastic hinges influences the results. The modeling approach plays a key role only at very high seismic intensity where large ductility demand is imposed. In addition, changing the type of joints has less influence on the overall response of the frame.

The presence of rib stiffeners in extended end-plate joints influences the yield line distribution in the tensile zone of the connection, the depth of internal lever arm as well as the resistance of compression components of the joint. In addition, the stiffeners may affect the plastic rotation capacity of the connected beam in both monotonic and cyclic regime. The current EN1993:1–8 (2005) gives limited recommendations on these issues, while EN1998-1 (2005) does not provide any detailing rules to enforce ductile cyclic response when rib stiffeners are adopted in end-plate connections. In order to investigate these criticisms, extensive parametric finite element simulations were carried out and the obtained results are described and discussed in this paper. The main analyzed parameters are the thickness, the slope (i.e. the depth to width ratio), and the constructional imperfections of the rib stiffeners for different beam-to-column assemblies alternatively designed with full and partial strength connection. The monitored response from monotonic and cyclic analyses allows characterizing the yield line distribution and the variation of internal forces into the rib and the bolt rows. The evolution of the internal lever arm of the connection, the out-of-plane bending and torsional moments developing when the connected beam experiences large plastic rotations as well as the forces acting on lateral torsional restraints are also investigated.

Background: Steel beam-to-column joints are generally designed and analysed considering the response parame-ters in their main bending plane, disregarding the influence of the connections and the related beams in the transverse direction. However, the 3D response of the joint can be influenced by the presence of the transverse beams in the case of column loss scenario. Objective: The objective of the study is to investigate the influence both the influence of the transverse beams and the potential effectiveness of the design rules developed within the research project EQUALJOINTS in case of column loss scenarios. Method: A comprehensive set of parametric finite element analyses was carried out. Three external joints were selected, and two types of column loss scenarios were investigated for 2D and 3D joint configurations. Results: The obtained results show that the presence of the secondary beams is beneficial to arrest the progressive collapse since it increases the resistance of the joint assembly, reducing the plastic demand into the primary moment-resisting joint. Conclusion: The presence of the secondary beams improves the joint performance under column loss thanks to their torsional stiffness; when the dimensions of the double cleat connection are comparable with those of the primary moment resisting joint, they are also able to increase the stiffness of the entire joint. Severe plastic deformation can be observed in the double cleat connections in joints directly affected by the column loss. Therefore, these connections should be properly designed in order to guarantee adequate ductility.

Extended stiffened end-plate connections are widely used in seismic area due to their good performance in terms of both resistance and ductility. The most of existing studies focused on the all-steel behavior of these joints, disregarding the composite action of the concrete slab that is generally disconnected. However, the presence of the concrete slab can have beneficial effects on the structural stiffness for both gravity and lateral loads. Hence, most of the building frames are usually designed considering steel-concrete composite solution. However, the slab can strongly influence the hierarchy between beam and column and the ductility of the joint. In this paper the influence of composite deck on the response of extended stiffened end-plate joins has been investigated by means of finite element analyses (FEAs). In particular, the following details have been investigated: (i) all steel joints without slab; (ii) steel joint with disconnected slab; (iii) composite joint.

This paper presents a numerical study on the behavior of extended stiffened end plate bolted beam-to-column joints subjected to sudden column removal. To this aim, finite element analyses, validated against experimental tests available from literature, were carried out to investigate the response of the joints under catenary action. The influence of additional bolt rows, generally ineffective in case of design for pure bending response, was also examined and some practical design implications have been drawn up from the parametric study.

AISC358–16 provides seismic pre-qualification rules and design procedures for fully restrained extended stiffened end-plate bolted connections, while the cases of partially restrained connections are generally not considered for seismic applications. However, provided that the failure of both bolts and the welds is prevented, partially restrained joints may exhibit satisfactory ductile behavior, also accommodating interstory drift rotation larger than 0.04 rad. This performance can be achieved if the resistance of brittle zones of the connections is greater than the ultimate resistance of the ductile components, as experimentally proved in some recent European research projects. Therefore, the study presented in this article aims at proposing design rules for partially restrained connections in order to meet the prequalification limits given by AISC358–16. To achieve this purpose, a comprehensive parametric study based on finite element analysis (FEAs) was carried out. The numerical results show that the proposed AISC-compliant procedure can guarantee satisfactory performance of partially restrained connections, which exhibit good ductility and dissipation capacity.

In view of the development of heavy timber seismic resistant structures, in the context of modern seismic design approach based on the mechanical triad of strength, stiffness and ductility, the dissipative capabilities should be delegated to specific devices, considering that timber mechanical behavior is typically fragile. With reference to the structural type of Moment Resisting Frames (MRF), steel links located at the ends of the beams are very promising solutions. In this regards the paper focuses on a beam-column timber joint equipped with steel links for dissipative heavy timber seismic resistant MRF, inspired by a reference experimental campaign on timber beam-to column assemblages conducted at the University of Trento. A refined finite element numerical model of the joint is set-up through the Abaqus software (v. 6.14) and efficiently calibrated on the basis of the experimental evidences. A very good numerical simulation of monotonic tests carried out in Trento has been achieved. The FE model would be a powerful tool for carrying out parametrical analysis aiming at the characterization of the mechanical properties and the optimization of the system, for the application in seismic resistant timber MRF.

Recent research ventures focus on structural systems characterized either by low-damage or easily repairable solutions. In this context, moment resisting frames (MRFs) equipped with friction joints represent a viable option. Among the different types of friction beam-to-column connections, the arrangement with symmetric friction devices are very effective to provide stable and ductile friction hysteresis, thus reducing the damage in the structural members (beams and columns) to a minimum or even to zero. Numerical and experimental investigations on the beam-to-column assemblies within the RFCS FREEDAM project testify to the good seismic performance of the friction device when properly designed. However, within this research project full scale pseudo-dynamic tests will be performed for a better understanding of the influence of such joint on the overall structural behavior of MRFs. In this paper the results of preliminary numerical simulations are presented to give the first insights on the response of the experimental mockup as well as to validate the accuracy of two software with largely different capabilities. Static pushover and nonlinear dynamic analyses were performed and the results for the benchmark structure (frame equipped with reduced beam section joint) and for the structure equipped with the friction devices are presented.

Steel joints for moment resisting frames in seismic areas are designed in accordance with the capacity-based design principles This design philosophy can be also effectively implemented to enhance the robustness of structures against progressive collapse. In this article the effectiveness of seismic design criteria on the robustness of beam-to-column joints is investigated. The numerical investigation was carried out on a set of European beam-to-column assemblies equipped with extended stiffened end-plate connections. The beams in the analyzed models were axially-restrained and subjected to large rotational demands, characteristic of the column loss scenario. The results show that the joints designed in accordance with seismic requirements have an adequate performance, provided that the axial resistance of half of the connection is larger than the plastic resistance of the beam.

Solar neutrinos have played a central role in the discovery of the neutrino oscillation mechanism. They still are proving to be a unique tool to help investigate the fusion reactions that power stars and further probe basic neutrino properties. The Borexino neutrino observatory has been operationally acquiring data at Laboratori Nazionali del Gran Sasso in Italy since 2007. Its main goal is the real-time study of low energy neutrinos (solar or originated elsewhere, such as geo-neutrinos). The latest analysis of experimental data, taken during the so-called Borexino Phase-II (2011-present), will be showcased in this talk&mdash, yielding new high-precision, simultaneous wide band flux measurements of the four main solar neutrino components belonging to the &ldquo, pp&rdquo, fusion chain (pp, pep, 7 Be, 8 B), as well as upper limits on the remaining two solar neutrino fluxes (CNO and hep).

Extended stiffened end-plate bolted joints are widely used in seismic resistant steel frames. In the United States of America (USA) this type of joint is seismically pre-qualified according to AISC 358-16. At the present time, prequalification criteria for different types of bolted joints are also under development in Europe within the framework of the EQUALJOINTS (i.e. European pre-QUALified steel JOINTS) research project. The design criteria and detailing rules proposed by this European project for extended stiffened end-plate joints differ from AISC criteria in some respects. Therefore, the aim of this work is to verify and to compare the effectiveness of both design procedures through the results of a comprehensive parametric study based on finite element (FE) simulations. The FE results show that both AISC and European design procedures can guarantee the formation of a plastic hinge in the beam under cyclic loading. However, under column loss scenarios the European connections are more ductile than those designed according to both AISC 358-16 and AISC 341-16. In addition, it is investigated the possibility to use heavy columns satisfying the resistance requirements without stiffeners (i.e. continuity plates and supplementary web plates). The comparison between the response of the joints with and without stiffened columns shows that heavy unstiffened columns can be adopted without appreciably modifying the joint response.

Geo-neutrinos, electron anti-neutrinos produced in beta-decays of naturally occurring radioactive isotopes in the Earth, are a unique direct probe of our planet's interior. After a brief introduction of the geo-neutrinos' properties and of the main aims of their study, we discuss the features of a detector which has recently provided breakthrough achievements in the field, Borexino, a massive, calorimetric liquid scintillator detector installed at the underground Gran Sasso Laboratory. With its unprecedented radiopurity levels achieved in the core of the detection medium, it is the only experiment in operation able to study in real time solar neutrino interactions in the challenging sub-MeV energy region. Its superior technical properties allowed Borexino also to provide a clean detection of terrestrial neutrinos. Therefore, the description of the characteristics of the detected geo-neutrino signal and of the corresponding geological implications are the main core of the discussion contained in this work.

Bolted extended stiffened end-plate beam-to-column joints are widely used in seismic resistant steel frames. The flexural behaviour of this type of joints is crucial in order to guarantee an adequate seismic response. Eurocode 3 part 1–8 provides design rules and analytical models to predict the mechanical behaviour of the joints. Eurocode 8 provides additional design rules for seismic resistant joints, contradicting some requirements of Eurocode 3. In addition, in Eurocode 3 the influence of the rib stiffeners on the flexural response of this type of joints is not clearly accounted for. In this paper the criticisms of current versions of Eurocode 3 and Eurocode 8 are discussed and design criteria for seismic resistant extended stiffened end-plate beam-to-column joints are proposed. In addition, the results obtained from parametric finite element simulations are presented in order to support the discussion and to validate the design procedure.

Extended stiffened end-plate bolted joints are widely used in seismic resistant steel frames. In the United States (US) this type of joint is seismically pre-qualified according to AISC 358. In Europe within the framework of the ongoing EQUALJOINT research project, prequalification criteria for different types of bolted joints are under development. Differently from the US approach, in the EQUALJOINT procedure both full and partial strength joints are seismically qualified. The experimental tests carried out within the EQUALJOINT project confirmed the effectiveness of these intermediate strength levels. Therefore, the aim of this work is investigate the possibility to extend this design approach to US joints. The results of a comprehensive parametric finite element investigation are described and discussed, showing the effectiveness of the proposed design performance criteria

The Gran Sasso National Laboratory (LNGS) is the largest underground laboratory in the world. It has been realised explicitly for the experimental purposes in Nuclear Physics branch and it’s unique in this field: infact, all over the world similar underground labs are usually mines (operational and/or decommissioned). The LNGS lab is actually attended by 500 researchers and technicians coming from all over the world. The huge LNGS underground halls (100m long, 20m wide, 20m high) are strictly correlated to the highway-tunnel which connects L’Aquila and Teramo countries (a 10,5 Km tunnel).

In this paper the problem of volatile organic compounds control in the Gran Sasso nuclear physics underground experimental laboratory, Italy, is addressed. In particular the design and risk assessment of a carbon adsorption unit with stream recirculation for the removal of pseudocumene vapors in a nitrogen stream are discussed after a complete process characterization. The plant represents an unconventional installation in terms of required operational flexibility, materials compatibility, and safety level. The adopted technical solutions are described and the results of a Hazard Operability analysis are presented in order to identify design modifications which may contribute to further increasing system safety. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 37–46, 2004

This paper outlines a methodological approach utilizing quantitative risk analyses and cost–benefits evaluation in order to select the most cost-effective options for risk reduction in industrial plants including structural changes and preventive maintenance. The methodology is based on quantification of top events resorting to fault trees, a sensitivity analysis of the probability of occurrence of top events, and a comparison of corrective measures based on cost and effectiveness criteria. The method is applied to a case study represented by the pseudocumene purification plant of the Borexino experiment in order to show its capability. The experiment is located in the Gran Sasso National Laboratory operated by the Italian National Institute for Nuclear Physics. © 2004 American Institute of Chemical Engineers Process Saf Prog 23: 121–131, 2004