IT-RI stage tests transition time, steady COF values, and COF's coefficient of variation.

IT-RI stage tests transition time, steady COF values, and COF's coefficient of variation.

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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...

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... 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.
... 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 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 experimental findings reveal the limitations of electrolytic nickel plating and shot-peening treatments in terms of steady-state stage, reaching COFst values similar to that of the TR reference condition in less than two minutes. ...
... The Vickers hardness of the S355JR steel was measured and reported in the previous work from the authors and resulted equal to 228 ± 45 [21]. Wear tests were performed at room temperature by a TR-20LE tribometer (Ducom Instruments, Bangalore, India) in pinon-disks configuration (ASTM G99-17 standard [24]), with reciprocating sliding condition. ...
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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.
... 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]. ...
... The use of coatings as a surface modification technique plays an essential role in the restoration of components that have experienced failures during their time in production and in the prevention of potential future failures. This is particularly crucial in applications where these components are subjected to aggressive conditions, such as mechanical stresses that may weaken the properties of the original material, as well as exposure to corrosive environments [1][2][3][4][5][6][7]. ...
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Within the drilling, petrochemical, construction, and related industries, coatings are used to recover components that failed during service or to prevent potential failures. Due to high stresses, such as wear and corrosion, which the materials are subjected to, industries require the application of coating between dissimilar materials, such as carbon steels and stainless steels, through arc welding processes. In this work, an austenitic stainless steel (ER308) coating was applied to an H13 tool steel substrate using the gas metal arc welding (GMAW) robotic process. The heat input during the process was calculated to establish a relationship between the geometry obtained in the coating and its dilution percentage. Furthermore, the evolution of the microstructure of the coating, interface, and substrate was evaluated using XRD and SEM techniques. Notably, the presence of martensite at the interface was observed. The mechanical behavior of the welded assembly was analyzed through Vickers microhardness, and a pin-on-disk wear test was employed to assess its wear resistance. It was found that the dilution percentage is around 18% at high heat input (0.813 kJ/mm) but decreases to about 14% with reduced heat input. Microhardness tests revealed that at the interface, the maximum value is reached at about 625 HV due to the presence of quenched martensite. Moreover, increasing the heat input favors wear resistance.
Chapter
Precast RC structures are commonly adopted for industrial and commercial buildings, to build huge spaces with limited costs and construction times. Due to the lack of efficient seismic regulations until recent times, and adequate assessments of seismic hazard, a huge number of seismically inadequate precast RC buildings are spread through Southern Europe territories. Workers’ and users’ safety requirements, and the preservation of high-value facilities and stocks, demand the adoption of effective retrofit techniques for earthquake risk mitigation.For this structural typology, connections between structural elements are often crucial for carrying lateral loads, such as earthquakes. This study presents an innovative device that acts as beam-to-column joint and as damper at once, with bidirectional dissipative capacity. Very easy to install, low cost and reusable after the main shock, this novel Bidirectional Rotation Friction Damper (BRFD) has been conceptualized and designed to improve the seismic performance of such structures by excluding the brittle failure of structural and non-structural elements. Preliminary experimental tests performed at the University of Ferrara, Italy, have proved the high-damping capacity of this novel device.BRFD effectiveness on a precast structure has been explored using nonlinear time-history analysis accounting both low- and high-intensity Italian earthquakes. Numerical modelling has shown that no beam’s slippage on column top section and no column crisis can occur in both building directions when BRFD are properly implemented. The designed devices provide a global improvement of the seismic performance of the building, preventing any structural and non-structural damage even for the more critical Near-Field events.Keywordsbeam-to-columns connectionsbidirectional dampingrotational friction dampersRC precast structures