Influence of the characteristics of isolation and mitigation devices on the response of single‐degree‐of‐freedom vibro‐impact systems with two‐sided bumpers and gaps via shaking table tests

Abstract

Summary During strong earthquakes, structural pounding may occur between structures (buildings, bridges, strategic facilities, critical equipment, etc.) and the surrounding moat wall because of the limited separation distance and the deformations of the isolator. An arrangement that favors the solution of this problem is the interposition of shock absorbers. Thus, the influence of geometrical and mechanical characteristics of isolation and mitigation devices on nonlinear, nonsmooth response of vibro‐impact systems is experimentally investigated in this paper on the basis of a laboratory campaign of experimental tests. Shaking table tests were carried out under a harmonic excitation in order to investigate two different configurations: the absence and the presence of bumpers. Three different values of the table acceleration peak were applied, four different amplitude values of the total gap between mass and bumpers were considered, and also four different types of bumpers were employed; moreover, two problems were addressed, namely, control of excessive displacements and control of excessive accelerations, and hence, two types of normalization were adopted in order to better interpret experimental results. Suitable choices of pairs of bumpers and gaps were suggested as a trade‐off between conflicting objectives. Furthermore, a numerical model was proposed, and its governing parameters identified in order to simulate the experimental results.

Scenarios in the experimental response of a vibro-impact single-degree-of-freedom system and numerical simulations

“…The influence of geometrical and mechanical characteristics of isolation and mitigation devices on the nonlinear non-smooth response of vibro-impact systems was experimentally and numerically investigated in [56]. Suitable choices of pairs of bumpers and gaps, that allows to reach a trade-off between two conflicting objectives, namely, control of excessive displacements and control of excessive accelerations were suggested in [57] and a numerical model was proposed in order to simulate the experimental results. In [58] Stefani et al focused the attention on the experimental pseudo-resonance curves of maximum absolute acceleration and excursion of the SDOF oscillator and characterized the hysteresis zone between the jumps.…”

The effect of the presence of obstacles on the dynamic response of single-degree-of-freedom systems: Study of the scenarios aimed at vibration control

“…To prevent the damage of the isolation system and avoid the occurrence of pounding against adjacent structures, the horizontal displacements can be limited by inserting suitable obstacles, which can be placed at a certain distance (gap) from the structure to be protected (outer pounding [38]) or can be incorporated into the isolation system (inner J o u r n a l P r e -p r o o f Journal Pre-proof can be eliminated for both hardening and softening primary isolators. Furthermore, the end-stop can effectively also attenuate the absolute acceleration response for a hardening primary isolator, while more damping is needed to attenuate that for a softening primary isolator.…”

Numerical study on the response scenarios in a vibro-impact single-degree-of-freedom oscillator with two unilateral dissipative and deformable constraints

“…The practical problem of base-isolated structures impacting against moat-walls inspired several works of the authors, of both numerical and experimental nature, in which the response of these structures was simulated using a single-degree-of-freedom (SDOF) oscillator, consisting of a mass and a damper, impacting against two deformable and dissipative constraints (bumpers), symmetrically arranged on both sides [61][62][63][64][65][66][67][68][69]. Some of the scenarios that can occur within the system response were first investigated in the theoretical-numerical work presented in [61].…”