Experimental study of the effect of restraining rim design on the extreme behavior of pendulum sliding bearings

Abstract

Summary While the performance of sliding isolators has been extensively validated under typical levels of ground motion, there have been very few experimental studies on the extreme behavior of sliding isolation bearings when the displacement limit is reached. However, to appropriately design isolated systems, from selecting the displacement capacity of the bearing to sizing the superstructure members, the behavior of the bearing as it reaches, and in some cases exceeds, the displacement limit should be well understood. A series of shake table tests to investigate the extreme behavior of double pendulum sliding bearings under strong ground motions were conducted at McMaster University. One major difference in sliding bearings around the world is how the motion of the bearing is restrained at the bearing's displacement capacity. Scaled bearings with four different types of restraining rim designs were included, representing typical sliding restraining rims found in Europe, Japan, and the United States. Experimental observation shows that the restraining rim has a significant influence on the extreme behavior of sliding isolation bearing. Key response parameters such as impact force and uplift are evaluated and compared between the different sliding bearing designs. While the bearing with no rim bearing imparts the lowest forces to the superstructure, it loses its functionality at a lower amplitude input than all the other rim types. For the other rim designs, the impact forces are significantly higher but they remained operational although damaged.

Estudio experimental en mesa vibradora de una estructura de madera de 3 pisos de entramado ligero con aisladores sísmicos friccionales resilientes a impacto

“…Considerando que el impacto puede ser uno de los causantes de colapso (Bao et al, 2017;Becker et al, 2017) y que la construcción del moat wall podría evitarse, Auad y Almazán (2021) desarrollaron un dispositivo denominado IR-DCFP (Impact Resilient Double Concave Frictional Pendulum), el cual es capaz de reducir las fuerzas producidas por impacto. El dispositivo tiene dos interfaces de roce, la primera interfaz llamada de bajo roce o exterior se produce debido al roce producido entre una placa polimérica y el acero inoxidable de la superficie de deslizamiento.…”

Retrofitting of R.C. Frame Buildings With Double Con-Cave Curved Surface Isolator Sliders Characterized by Over-Stroke Displacement Capacity

“…The CSS bearings can be further divided in two main groups: devices with or without a displacement restrainer, such as displacement restraining rings, which prevent the inner slider to slide past a certain point which usually is the perimeter of the housing pad. The displacement restraining rings are made of the same material of the housing plate and can be welded, bolted to it or even form a single block with the pad itself [6] and are widely used in America [7] in order to control displacements and to avoid the isolator disassembly when displacements higher than the design ones occur. Nevertheless, the impact against such restraining end-stroke element may induce significantly high acceleration to the superstructure.…”

“…Usually in Europe, the gap separating the superstructure from the retaining wall is much larger than the displacement capacity of the isolators, and consequently, the inner slider can run on the edge of the sliding surfaces for earthquakes producing displacement larger than the isolators capacity. When displacement end-stroke elements are not employed, and concave plates feature a flat rim [6], the inner slider movement beyond the geometric capacity displacement d c of the isolator is allowed entering in the so-called over-stroke displacement regime. The slider running in the over-stroke displacement regime can provide the DCCSS device with an increased displacement capacity dlim and sliding force.…”

Base Isolated Buildings With Curved Surface Sliders Including Displacement Restraints

“…On the contrary, the European Standard does not allow the presence of restraining element and only approves the use of structural joints separating the superstructure from the surrounding constructions, in order to safely accommodate the seismic movement. Retaining elements impact has not been widely observed and studied in the past, except for the studies of Masroor and Mosqueda in 2012 [9] and Bao and Becker in 2017 [10]. In [9] an impact element considering moat wall flexibility is proposed based on theoretical observations and experimental simulations to better understand the consequences on the superstructure of the impact.…”

“…In [9] an impact element considering moat wall flexibility is proposed based on theoretical observations and experimental simulations to better understand the consequences on the superstructure of the impact. In [10] an extended experimental campaign to investigate the extreme behaviour of double pendulum sliding bearings under strong ground motions was conducted, considering scaled bearings with four different types of restraining elements representing typical devices found in Europe, Japan, and the United States.…”