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Tribological investigation on metal mating surfaces to explore real use conditions of a novel friction damper for seismic applications

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... Starting conceptually from a simple RFD, and using a movable plate geometry, a Bidirectional Rotational Friction Damper (BRFD) is created producing a relevant damping effect in two main directions. Section 2 describes the BRFD structural layout and briefly highlights the findings of a preliminary tribological investigation performed at the Metallurgy Laboratory (Engineering Department, University of Ferrara, Italy) [29,30] defining the investigated friction interfaces. Section 3 shows the real-scale BRFD prototype, the experimental setup, and the adopted testing protocols, considering the guidelines of EN15129 [31] during the early mechanical investigation carried out at the Structural Integrity Laboratory (Engineering Department, University of Ferrara, Italy), Section 4 shows the results and comments of the mechanical tests, while a final Section 5 collects the main remarks. ...
... To perform the mechanical testing, the design of the BRFD prototype first requested the selection of proper coupling surfaces able to develop a reliable and steady friction coefficient μ. A preliminary tribological investigation has been performed at the Metallurgy Laboratory (Engineering Department, University of Ferrara, Italy) [29,30], to compare the effects on μ steadiness of different surfaces finishing and treatments. ...
... However, several studies (among the others see [33,38,39]) show how the performance of friction devices can be significantly influenced by the sliding velocity and the variation of bolt axial load. In addition, the tribological investigation previously performed for the BRFD development highlighted how the overall μ steadiness increases significantly after performing running-in stages [29,30]. ...
... Based on the outcomes of the above-reported literature, the present study analyzes the effect of the surface topography on the dry-sliding wear behavior of a structural steel under self-mating test conditions. The investigation is driven by the development of a novel passive energy dissipation device for seismic applications whose characteristics were explored in previous works [21,22]. Specifically, previous analyses [21] were devoted to analyzing the tribological behavior of the S355JR structural steel preliminarily treated by different mechanical and galvanic processes, i.e., electrolytic nickel plating, white electrolytic zinc plating, and two shot-peening treatments. ...
... The above-mentioned turned and milled disks were 165 mm in diameter, while the flat-ended pins were 6 mm in diameter. According to [22], tests were conducted under an applied load of 50 N and at 1 Hz and 2 Hz oscillatory frequencies (i.e., linear sliding speeds of 0.111 m/s and 0.222 m/s, respectively) to reproduce the actual condition of the friction damper device. Before the wear tests, the specimens were cleaned in an ultrasonic bath with isopropanol. ...
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This work investigates the tribological behavior of a machined S355JR structural steel in dry sliding conditions for the development of an innovative seismic dissipation system. Flat-ended pins and disks were made of the same structural steel to simulate the conformal contact of different device parts. Pins were machined by turning, while disks were milled and turned to obtain a nominal average surface Ra roughness ranging from 0.8 µm to 6.3 µm. The influence of the surface roughness on the coefficient of friction (COF), specific wear rate (SWR), and time to steady-state (TSS) was investigated. Tribological tests were conducted reciprocating motion in dry sliding conditions to simulate the operating conditions of the device, with 1 Hz and 2 Hz reciprocating frequencies and an applied normal load of 50 N. The Rsk and Rku roughness parameters helped to better understand the tribological response of milled and turned disks, having an influence on the TSS and SWR.
... In the context of developing an innovative seismic dissipation system, which aims to compromise the steadiness of COF and process costs [26], this work deals with the tribological characterization of a structural steel preliminarily treated by different mechanical and galvanic processes. PoD tests have been performed and set to reproduce the actual condition of the device in development, taking into account the pv parameter and the typical earthquake duration. ...
... The setting was calibrated to reproduce the actual condition of the FD device and assume disk rotation frequencies typical of the structural system in which a FD is usually installed. In the real use conditions, the typical values of the pv parameter for the FD (pv FD ) under development range between 0.10 and 0.20 [26]. Setting a circular arc pin track with an average of 54 mm arc length and considering oscillatory frequencies of 1 Hz and 2 Hz, the associated maximum linear speed equals 0.111 m/s and 0.222 m/s, respectively. ...
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In the context of developing an innovative seismic dissipation system, which aims to compromise on the steadiness of friction and processes costs, this work deals with the tribological characterization of an S355JR structural steel, whose surface has been preliminarily treated by different mechanical and galvanic processes. Tribological tests were performed in a pin-on-disk configuration and in reciprocating motion, using values of 1 Hz and 2 Hz as the motion inversion frequency, a constant normal load of 50 N, and variable test duration, according to the most frequent seismic events. The tribological system was composed of S355JR structural steel pins and disks of the same steel, which were alternatively treated by electrolytic nickel plating, electrolytic zinc plating, and two different shot peening processes. The results highlight that while electrolytic nickel increments the overall steadiness of the coefficient of friction (COF), electrolytic zinc plating guarantees the longest first steady-state stage and a COF lower than the one guaranteed by the coupling of untreated pins and disk.
... Fig. 18 shows the results of the importance analysis in terms of performance level from "Really good" (white colours) to "Really bad" (red colours) with an additional area associated with "BRFD unfeasible" (black region). This additional area is obtained considering BRFDs with maximum length of 90 cm with μ equal to 0.45, according to previous authors findings [43][44][45], and the F act,x values that are effectively obtainable from the geometry associated with each K x . In fact, lower values of K x are associated with smaller BRFD's plate width and a smaller range of available studs' diameters and applicable torque. ...
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Precast RC structures have been widely used in industrial and commercial buildings since the 60 s in the most developed areas. However, during those decades of economic growth, most buildings were constructed without seismic design criteria, accounting for gravity loads only. For this reason, this structural typology often faces a significant seismic risk in earthquake-prone areas due to the lack of effective connection between structural elements. As a result, the seismic retrofit of precast RC structures is essential to prolong their service life and mitigate seismic losses. The present work shows the conceptualisation study of an innovative seismic protection device called Bidirectional Rotational Friction Damper (BRFD) for precast RC structures that behave simultaneously as a beam-to-column joint and damper. This device unifies the concepts of rotational friction dampers and a movable plate system, producing a damping effect along two main directions. Furthermore, the device’s ability to dissipate energy through friction enables it to remain undamaged during multiple seismic events while maintaining its damping capacity. After defining a simplified analytical model, to evaluate the influence of the BRFD on a structure’s behaviour during a seismic event, a case study was conducted on a single-story, single-bay precast reinforced concrete structure made of plane parallel frames, i.e. that lacks secondary frames. Quasi-static and nonlinear time history analyses were performed to evaluate the BRFD efficacy in reducing seismic forces and displacements, and an importance analysis was carried out using a multi-criteria decision-making (MCDM) approach to identify the optimal configuration of the BRFD for the case study. The main results highlight that introducing the BRFD positively influences the dynamic performance of the structure, producing a significant reduction of interstorey drift and total base shear and preventing structural and non-structural damage.
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There is a strong need for surfaces with a high coefficient of static friction to meet the demands for increasing performance and lightweight construction strategies, especially regarding friction-locked connections. An auspicious turn-milling process used to generate protruding surface structures which lead to a high coefficient of static friction is investigated. The influence of the corner geometry on the surface structure is examined by machining end faces of specimens of the steel 42CrMo4+QT (1.7225). Experimental tests for the identification of the coefficient of static friction show a significant increase up to 275% (μ0.1° = 0.55) for turn-milled surfaces in comparison to unstructured specimens (μ0.1 ≈ 0.2).
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This paper describes the development process of a new low-steel composite friction material and the experiments to investigate its frictional behavior. Automotive braking technology was adapted to derive an optimal friction damper for buildings, and a high friction coefficient and stable behavior were set as the primary targets for performance. To improve performance, clamping details which incorporated load washers were also proposed. In order to evaluate the performance of the friction system, pseudo-dynamic tests were conducted. In the experiments, the proposed friction dampers showed repeatable, predictable, and very stable behavior without significant fading of frictional resistance, even under hundreds of repetitive sliding excursions. The friction load tended to be proportional to the initial clamping force regardless of the real-time clamping force, thus confirming that the behavior of the proposed dampers could be predicted using the idealized Coulomb friction model. It was also verified that frictional performance could be remarkably increased through the use of conical shaped load washers, when applied correctly. Furthermore, nonlinear time history analysis was performed on a five-story example building with and without friction dampers. Based on the results, the friction damped system demonstrated effectiveness in reducing structural responses such as roof displacement, base shear force, and story drift ratio compared to the original undamped frame system.
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The friction between two solids depends on contact conditions. The knowledge of the surface microtopography is very important for study of tribological processes in contact zone. The coefficient of static friction depends on many factors: the mechanical properties of material, the surface roughness, the mutual dissolution of materials, the contact time, the lubricant film properties, the elasticity of tribosystem, etc. The influence of the contact surface roughness on static friction coefficient was studied in this paper. Today, an engineer has large possibilities for identification of form and size of surface roughness with modern measuring equipment. The complex roughness parameter describes successfully the surface roughness and it is suitable for the static friction coefficient investigation. For experimental investigation of the static friction coefficient, the model with surfaces contact between samples was established. The experimental results are presented in this paper.
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Slotted Bolted Connections (SBCs) are modified bolted connections designed to dissipate energy through friction during rectilinear tension and compression loading cycles. Experimental results on two types of SBCs are reported. In one type, friction occurs between clean mill scale steel surfaces; in the other, friction is between clean mill scale steel and brass surfaces. The behavior of connections with brass on steel frictional surfaces is found to be more uniform and simpler to model analytically than that with steel on steel surfaces. These connections maintain essentially constant slip force, and unlike those with steel on steel surfaces, require minimal overstrength of the system in design. The frictional mechanisms giving rise to the observed behavior are explained. As an example of application a one story diagonally braced frame was designed and its behavior determined for four different earthquakes. Experimental results are presented for the fabricated SBC for this frame subjected consecu...
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A new concept of aseismic design for steel framed buildings is proposed. By providing sliding friction devices in the bracing system of the framed buildings, their earthquake resistance and damage control potential can be considerably enhanced. During severe earthquake excitations, the friction device slips and a large portion of the vibrational energy is dissipated mechanically in friction rather than inelastic yielding of the main structural components. Results of inelastic time-history dynamic analysis show superior performance of the friction damped braced steel frames when compared to computed responses of other structural framing systems. The proposed friction devices act, in effect, both as safety valves and structural dampers. The device may also be conveniently incorporated in existing framed buildings to upgrade their earthquake resistance.
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There is a need for coatings to resist not only wear but also chemical attack and excessive heat. Alumina coatings were applied to type 304 stainless steel using detonation gun method with high energy ball milled powder having an 83 nm average crystallite size. Coatings with varying amounts of partially melted (PM) and re-solidified (RS) alumina were obtained by adjusting the heat input and the gun-substrate distance. Deposition conditions which enhance the formation of thinner splats and nano particulate alumina were found to improve the sliding wear resistance of the coatings when mated with an alumina ball under reciprocating test conditions. The observed lower wear rate of the coatings was due to the absence of brittle deformation of the layers and a lower friction coefficient. The deformation mechanism of the coatings was correlated with their microstructures and with hardness data from polished cross-sections.
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A review of the evolution of energy dissipation devices of hysteretic type is presented. Both friction and yielding devices are included in the paper covering a worldwide range of applications. Due to the increasingly large number of available devices, the paper does not attempt to present a state-of-the-art on the subject, but to focus on discussing the main original research efforts that have paved the way of the current technology of energy dissipation devices. Relevant past applications of devices are briefly described making particular emphasis on important issues such as experimental assessment, effectiveness of their modeling by nonlinear analysis techniques, materials and constructability. Devices selected for discussion in the paper are presented in a historical perspective and are considered pioneer original steps or research efforts directed towards an efficient and rational use of energy dissipation technology.
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A new connection for steel moment-resisting frames that incorporates posttensioning elements to provide a self-centering capacity along with friction mechanisms to dissipate energy is proposed and experimentally validated. The restoring force from the posttensioning elements in the connection makes the structure return to its undeformed state, even after experiencing large inelastic drifts. A bolt-prestressed friction mechanism with a frictional interface consisting of stainless steel and new nonasbestos organic break lining pads dissipates seismic input energy as the system undergoes lateral deformations. Cyclic tests were conducted to investigate the efficiency of the proposed friction interface and its performance under loading conditions that are expected during seismic loading. The test results showed that the frictional behavior is stable, repeatable, and predictable, although its friction coefficient is relatively low. Exterior and interior self-centering moment connections equipped with the proposed friction dampers were tested to study their structural behavior under cyclic loading. The results confirmed that friction damped posttensioned self-centering connections are capable of developing similar stiffness and strength characteristics to welded connections. They are also capable of undergoing large deformations with good energy dissipation characteristics, but without introducing inelastic deformations in the beams or the columns and without residual story drifts. Even at the ultimate stage, i.e., beyond the self-centering limit, the proposed connections can be detailed to exhibit a ductile response with the formation of flexural hinges in the beam sections, thus avoiding the sudden loss of strength and stiffness that occurs when the posttensioning elements are overloaded or when the beams buckle under excessive combined axial loads and bending moments.
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In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken to develop the structural control concept into a workable technology, and today we have many such devices installed in a wide variety of structures. The focus of this state-of-the-art paper is on passive and active structural control systems. Passive systems encompass a range of materials and devices for enhancing structural damping, stiffness and strength. Active systems, which include active, hybrid and semi-active systems, employ controllable force devices integrated with sensors, controllers and real-time information processing. This paper includes a brief historical outline of their development and an assessment of the state-of-the-art and state-of-the-practice of this exciting, and still evolving, technology. Also included in the discussion are their advantages and limitations in the context of seismic design and retrofit of civil engineering structures.
Principles of passive supplemental damping and seismic isolation
  • C Christopoulos
  • A Filatrault
Christopoulos C, Filatrault A. Principles of passive supplemental damping and seismic isolation. Pavia, Italy: IUSS Press; 2006.