Experimental and Finite Element Analysis of the Cyclic Behaviour of Linear Dissipative Devices

Abstract

In the past years, low-damage design of structures is becoming an efficient approach by engineers and researchers in order to mitigate the structural damage to buildings during a seismic event. To this aim, one of the most popular strategies is to endow framed structures with either viscous, hysteretic metallic, or viscoelastic devices. As an alternative to these systems, friction devices have been also studied, proving to be an effective solution. Steel braces endowed with linear dissipative devices based on friction can be used effectively both in the case of new and existing structures. Studies conducted on these devices stressed that their behaviour is mainly influenced by type of friction materials, loss of bolt preload and effect of disc springs. An experimental campaign has been performed at the Materials and Structures Laboratory of the University of Palermo on linear dissipative devices with different types of friction materials i.e., steel, thermal sprayed aluminium, and brass, to check their effectiveness. Finite element analysis using ABAQUS has been done to design, check the functionality, and get insight into the experimental results of the linear dissipative devices. An investigation has been done on the effectiveness of disc springs to limit the bolt preload variation in the device and the effect of thicknesses of plates on the functionality of linear friction dissipative device. The results showed that thermal sprayed aluminium, coupled with structural steel, is a good friction material as it provides stable hysteresis loops and high friction coefficient as compared to brass, and appropriately designed disc springs are able to limit bolt preload variation. The experimental results showed that the thermal sprayed aluminium provides a friction coefficient between 0.57 and 0.6 without significant variation even for a large number of cycles, while for the brass the friction coefficient at the beginning of the test was 0.25 and then it increased to 0.45 at the end of test, exhibiting large variation due to stick and slip phenomenon. The FEM analysis proved that the disc springs are able to minimize the variation of the contact pressure due to the Poisson effect and proper thickness of friction plates are important for the performance of friction device.

A Review of Friction Dissipative Beam-to-Column Connections for the Seismic Design of MRFs

“…Concerning experimental research, it should be noted that in many cases research using FEM models is preparatory to the design of the device, which will subsequently undergo experimental testing [22,61,62]; just as often, further extensive FEM research is conducted downstream of the experimental analysis, also used to validate the FEM model and to investigate the effects of variations in the geometric and mechanical parameters that characterize the model [22]. In the experimental approach, key research topics are the tribological behavior of the friction material used [63][64][65][66][67][68], the methods of application and control of the preload applied to the devices (generally by means of bolts) [64,[69][70][71][72], the design solutions used to create the device, the shape and stability of the resulting hysteresis loops, and the recentering capacity of the devices [22,[44][45][46]58,59,61,[73][74][75][76][77]. For friction devices for BCCs, of particular interest is the reliability with which the activation load of the device can be estimated, and its time evolution related to durability issues.…”

“…The steel angles were coated with thermal sprayed aluminum and used as friction pads, as shown in Figure 14c. Thermal sprayed aluminum was chosen as the friction material based on its excellent performance as tested by [69]. The connection between the vertical central plate and thermal sprayed aluminum steel angles was established by five M20 bolts Class 10.9 and the thermal sprayed aluminum steel angles were connected with the column with four M24 bolts Class 10.9.…”

“…The second part of the paper addresses the common factors affecting the performance of friction-based beam-to-column devices. Thus, firstly the emphasis is on the role of the friction materials (brass, steel, thermal sprayed aluminum, brake materials) [69]. Then, the factors affecting the performance of the devices, mainly the methods of application (torque wrench) and control (disc spring) of the bolt preload, are analyzed.…”

A Review of Friction Dissipative Beam to Column Connections for Seismic Design of MRFs

“…The second part of the paper addresses the common factors affecting the performance of frictionbased beam to column devices. Thus, firstly the emphasis is on the role of the friction materials (brass, steel, thermal sprayed aluminum) [35]. Then, the factors affecting the performance of the devices, mainly the methods of application (torque wrench) and control (disc spring) of the bolt preload are analyzed.…”

“…The steel angles were coated with thermal sprayed aluminum and used as friction pads, as shown in Figure 16c. Thermal sprayed aluminum was chosen as friction material based on its best performance as tested by [35]. The connection between the thermal sprayed aluminum steel angles and vertical central plate was made by five M20 bolts class 10.9 and the thermal sprayed aluminum steel angles were connected with column with four M24 bolts class 10.9.…”