In recent decades, low-yielding seismic devices based on the use of friction dampers have emerged as an excellent solution for the development of building structures with improved reparability and ...resilience. Achieving an optimal design for such low-yielding seismic devices requires precise control of bolt preloading levels and predictability of the friction coefficient (CoF) between the damper interfaces. While various types of friction devices exist that are capable of providing significant energy dissipation, ongoing research is focused on the development of novel friction materials that exhibit a stable hysteretic response, high CoF values, minimal differences between static and dynamic CoF, and predictable slip resistance. In this context, an experimental campaign was conducted at the STRENGTH Laboratory of the University of Salerno to evaluate the behaviour of new friction shims employing specially developed metal alloys. Specifically, the influence of the characteristics of the contact surfaces in the sliding area on the behaviour and performance of the friction device was analysed. The tests followed the loading protocol recommended by EN12159 for seismic device qualification. Monitored parameters included preloading force values and the evolution of slip resistance. The friction value was determined, along with its degradation over time. Finally, the material's performance in terms of hysteretic behaviour was assessed, providing a comparison of the tested specimens in terms of slip force degradation and energy dissipation capacity.
One recent solution to reduce the building repairing costs, in case of exceptional or destructive seismic events, is represented by the Sliding Hinge Joint (SHJ), initially proposed by the research ...group of the University of Auckland in 2005. This connection typology, using slotted bolted connections in beam-to-column joints of Moment Resisting Steel Frames (MRFs), ensures a large energy dissipation capacity with negligible damage. The slip resistance of the SHJ is usually provided by Asymmetrical or Symmetrical Friction Connections (AFCs or SFCs), whose response depends on the friction coefficient of the shims and on the bolt preloading. Since the bolt forces directly affect the resistance, the control of preloading during the life-time of the connection represents a key issue for the proper functioning of the device.
Within this framework, considering the lack of previous experimental works specifically devoted to the long-term response of SHJs, this paper presents the results of an experimental activity on subassemblies of friction dampers, assessing the loss of preload under service loading conditions, examining the possibility to limit the loss through different conical washer layouts (Belleville disk springs). Short-, mid- and long-term tests have been carried out in a joint experimental program carried out at the Universities of Liege and Salerno. The experimental results have been exploited to calibrate an analytical model able to predict the loss of preload over time, accounting for the influence of the external loads. The adoption of pre-set disk springs, reducing the stiffness of 1/10, shows a substantial reduction of the loss.
•The results of short-, mid- and long term tests on Symmetric friction dampers are presented and the results are used to calculate the loss of preload in different time steps;•The loss of preload with different washer configurations is evaluated;•The influence of the application of an external load on the loss of preload is investigated;•The difference in terms of loss reduction given by the considered washer configurations are highlighted;•An analytical model able to estimate the loss of preload is derived and validated;
The component method is a powerful tool for designing and modelling steel beam-to-column connections. Its widespread use is ensured by several formulations currently included in Eurocode 3 part 1.8 ...for welded and bolted joints. However, the recent use of 3D Laser Cutting Technology (3D-LCT) in the construction market has enlarged the range of solutions, allowing the realisation of tubular columns with passing-through elements. Given the recent development, no design formulations are currently provided for this typology. At this moment, only a few research studies have developed to fill this knowledge gap. At the University of Salerno, since some years, research efforts are ongoing to characterise the flexural strength of connections between Circular Hollow Section columns and passing double-tee beams, suggesting methodologies to predict the behaviour of the resistance and stiffness of this typology and some of its elementary joint components. Within this framework, this paper aims to examine the strength and stiffness of one of the main components of this joint, which was never examined previously, that is the so-called tube under localised transverse tension/compression. Design formulations are derived from a parametric study carried out through numerical simulations of several geometric configurations.
Double-tee profiles are the most popular members in Europe and the USA for steel structures. However, more efficient cross-sections, such as circular hollow sections (CHSs), could be adopted, since ...they can provide higher aesthetic, economic and mechanical benefits, with the only drawback of more complex connections such as in the case of I-beams welded to the external surface of circular hollow profiles. Based on the ring model theory, developed by Togo, a rule to design the flexural resistance of such a connection has been included in the Eurocode 3 part 1.8, while no formulations are provided to predict the corresponding initial stiffness. The present work aims at filling this knowledge gap, adopting an approach based on experimental, numerical and analytical work. A monotonic and a cyclic test have been performed on two beam-to-column sub-assemblies; the experimental outcomes have been exploited to validate a finite element (FE) model developed in Abaqus and used to numerically perform the monotonic loading simulations of 30 joints. Afterwards, starting from the extracted information about stiffness, a regression analysis was carried out to define the coefficient of a design equation analytically derived applying the component method approach. The regression analysis is characterized by a coefficient of variation equal to 0.19.
The behavior of steel structures is significantly affected by the connections between the steel members. For this reason, special attention to the prediction of the joint rotational behavior is ...devoted by Eurocode 3 which provides the well-known component method. In EC3, starting from the results of several researches, the formulations for the characterization of the behavior of T-stubs with two bolts per row are given, but with reference to T-stubs with four bolts per row, even though they are present in many actual structural situations, the limited number of experimental tests and analytical models has not led yet to the codification of this component in the code. In this work, starting from the results of three experimental tests on T-stub with four bolts per row, carried out at the laboratory on materials and structures of the University of Coimbra, a FE model in ABAQUS has been set up in order to analyze the yield line patterns corresponding to the different collapse mechanisms. Subsequently, with reference to the yield line shape different from that of T-stub with two bolts per row, the effective lengths have been revaluated applying an energy approach. The definition of the effective width for all the possible collapse mechanisms allowed to set up a proposal for determining the resistance of T-stubs with 4 bolts per row consistent with the approach provided by Eurocode 3. The model accuracy has been verified by means of a comparison with the results provided by a numerical analysis.
•The results of three tests on T-stubs with four bolts per row are presented.•A finite element model of the tests is developed in ABAQUS software.•The yield line method is applied to define the values of the effective lengths.•Equations able to predict the resistance of four-bolts T-stubs are provided.•The accuracy of the model is verified on the results of a parametric analysis.
This paper presents a dataset of cyclic tests and FE simulations of T-joints with Circular-Hollow-Section (CHS) chords and passing-through plates. These specimens were designed to be representative ...of components of beam-to-column joints between CHS columns and passing-through IPE beams, subjected to the cyclic load protocol proposed by AISC 341. Specifically, cyclic displacement histories were applied at the ends of the plates using a hydraulic actuator. The provided dataset includes the displacement histories recorded through a potentiometric transducer during the tests and the reaction forces recorded using the actuator's load cell.
Subsequently, Finite Element (FE) models of the specimens were developed and validated against the experimental results. The FE models accurately replicate the geometrical and mechanical properties of the tested specimens, and the displacement histories experienced by the specimens were applied.
Starting from the validated FE models, a parametric analysis explored the behaviour of a more extensive dataset comprising 44 geometric configurations of the analysed connection. Key geometric parameters influencing the connection's response were varied, including the ratio between plate width and tube diameter (β, ranging between 0.44 and 0.74), the ratio between tube diameter and twice its thickness (γ, ranging between 15.28 and 27.39), and the ratio between plate and tube thicknesses (τ, ranging between 2 and 8.75). For each of the 44 cases, cyclic simulations were performed, adopting the same protocol applied to the tested specimens and elaborating the force-displacement response.
The significance of this dataset lies in its derivation from numerical simulations based on FE models validated against experimental results, making it a reliable resource for researchers aiming to develop mathematical and mechanical models for predicting the cyclic response of T-joints between CHS chord members and passing-through plates.
This manuscript explores the stiffness and strength of Square Hollow Section (SHS) tubes subjected to localised transverse actions applied to the open side of a rectangular hole created using 3D ...laser cutting technology (3D-LCT). Understanding the behaviour of this specific detail is crucial as it is a key component in the connections between SHS columns and passing-through IPE beams. The methodology employed in this manuscript involved developing analytical equations to predict both stiffness and strength of this structural element. The provided equations are presented in a straightforward manner and were deduced by applying elasticity principles to structural components. To validate these equations, a parametric analysis was conducted, simulating the response of 27 distinct geometric configurations of the analysed structural detail thanks to the Finite Element (FE) software. Their accuracy was confirmed by comparing the results of these simulations with the outcomes derived from the formulated equations. The primary findings indicated that the proposed equations could predict the stiffness and strength of the studied detail with an average ratio close to 1 when comparing predicted and numerical results, and a coefficient of variation of approximately 10%.
In the last few decades, increasing efforts have been devoted to the development of beam-to-column connections able to accommodate the local ductility demand dissipating, contemporaneously, the ...seismic input energy. Among the typologies proposed, the so-called RBS (Reduced Beam Section) has gained wide acceptance in the construction market, leading to easy-to-construct and cost-effective solutions. As an alternative, new proposals based on the inclusion of friction devices in beam-to-column joints have recently been made. Such a practice has the merit, in case of destructive events, of exhibiting wide and stable hysteretic cycles concentrating damage in elements that undergo only minor yielding. Both RBS and friction joints have been widely studied, carrying out experimental tests on sub-assemblies investigating their cyclic rotational response. Nevertheless, the available experimental results on full-scale structures equipped with these connections are still quite limited. This is the reason why two experimental campaigns aimed at performing pseudo-dynamic testing of a full-scale two-storey steel building equipped with RBS and friction connections have been planned at the STRENGTH (STRuctural ENGineering Test Hall) Laboratory of the University of Salerno. The first experimental campaign with the structure equipped with RBSs has already been performed; the connections showed higher resistance than expected, and exhibited brittle fracture due to cyclic fatigue. The second campaign has not yet been carried out, but in this paper the blind analysis of the supposed behavior is reported. It is expected that the friction joints allow to dissipate the seismic input energy without any structural damage in the members, but only through the friction pads of the devices, which can be easily replaced at the end of a severe seismic event.
An innovative, simplified, and accurate model is proposed and developed to enable simplified yet realistic time history analysis of multi-storey buildings with moment resisting connections using ...friction energy dissipaters in the commonly used structural analysis and design program, SAP2000. The analyses are rapid to undertake, thereby enabling detailed study of the influence of many building system effects on the overall response. This paper presents the outcome of dynamic analysis of a complete 13-storey moment resisting steel building with Sliding Hinge Joints as the beam-column connections, considering the influential self-centring factors such as MRF and gravity columns continuity as well as column base and diaphragm flexibilities. The building is one of the Te-Puni towers, which are structural steel apartment buildings with steel-concrete composite floors, designed according to the low damage design philosophy, built in Wellington, New Zealand in 2008 and which have already been subjected to two significant earthquakes. The key objectives of the research have been to take the design of the 13-storey building and convert that into the proposed simplified model required for time history seismic analysis, to undertake analysis under scaled El-Centro earthquake record, investigate the peak inter-storey drift and the residual drift of the building, and determine the influence of column base rotational stiffness, floor slab out of horizontal plane displacement, type of friction damper, and MRF and gravity column continuity. It is concluded that the response of the building is stable and predictable, as expected, and that the post-earthquake state of the building, particularly from the self-centring point of view, is well within the limits for maintaining operational continuity following an ULS level design earthquake.
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