Tracy Becker

University of California, Berkeley | UCB

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 th...

Base isolation of high-rise buildings has been growing in popularity in Japan, yet it is uncommon in most of the world. While tall buildings already have long periods and thus lower input accelerations, the addition of isolation can decrease inter-story drifts and greatly decrease floor acceleration, protecting building content. By protecting build...

Base isolation is an effective method for mitigating seismic hazards and improving seismic performance under design-level ground motions. Previous studies have typically focused on comparing the performance of isolated and fixed-base buildings under design level or maximum considered level earthquakes without modeling the failure of the isolation b...

A 2 m by 6 m unidirectional shake table was constructed at the University of California, Berkeley and combined with a real-time hybrid simulation system creating a hybrid shake table. A series of tests were carried out to examine the viability of real-time hybrid simulation techniques to perform experimental simulations of buildings with midlevel s...

While base isolation provides enhanced structural and non-structural seismic performance, there are still concerns regarding large horizontal displacements in extreme earthquakes. Excessive horizontal displacements may induce detrimental pounding of base-isolated structures against the moat wall or the restraining rim of friction pendulum bearings,...

The life expectancy of bridge bearings is not well understood or predicted, and bearing replacement is primarily determined through field inspection and engineering judgement. An improved estimate of the time line for bearing replacement would aid in maintenance scheduling and budgets. As a first step in determining the age for replacement, the ann...

Gusset plates for high seismic regions are designed to allow brace buckling while minimizing damage to the beam or column by having large rotational capacity. The conventional approach is to use linear fold lines to permit the rotation, which can result in overly large plates. A more compact design uses elliptical fold lines, but both designs can l...

Gusset plates play an important role in the performance of braced frames in earthquakes. They typically are designed to bend as the brace buckles without fracture or causing damage to the beam or column. This has been achieved by other researchers by proposing various geometries for gusset plates with linear or elliptical fold lines. In this paper,...

Sliding isolation bearings can provide enhanced seismic performance for both structural and non-structural components under design level earthquakes. However, the ultimate performance once the physical displacement limit is reached or exceeded has received little attention. One major difference in sliding isolation bearing designs around the world...

While isolation can provide significantly enhanced performance compared to fixed-base counter parts in design level or even maximum considered level earthquakes, there is still uncertainty over the performance of isolation systems in extreme events. Researchers have looked at component level stability of rubber bearings and on the effect of moat im...

In an effort to mitigate major costs associated with isolation systems, especially in retrofit applications, isolation bearings may be placed on the tops of columns. In this configuration, a seismic gap and additional rigid diaphragm are no longer necessary, and excavation and foundation work may potentially be avoided in retrofit applications; how...

Although the behavior of friction sliding bearings is well understood, the failure behavior has not been thoroughly investigated. However, predicting and understanding the failure of bearings is an important key in designing isolated structures to minimize their collapse in extreme events, and thus, this study is critical. Because of its relative s...

This paper presents a rehabilitation technique developed under a design and construction scheme, termed minimal-disturbance seismic rehabilitation. This scheme pursues enhancing the seismic performance of buildings with the intention of improving the continuity of business while minimizing obstruction of the visual and physical space of building us...

While base isolation successfully decreases the accelerations transmitted to a structure, a tradeoff is large unfavorable displacements in the isolation layer. This study investigates an innovative system, termed ‘dual isolation’, which applies two layers of isolation at the base and at mid-story to resolve this issue. A linear analytical solution...

A design and construction scheme termed Minimal-Disturbance seismic retrofit pursues “Elegance” with the intention of improving the continuity of business while minimizing obstruction of the visual and physical space of building users. This paper presents the concept and verification tests of a damper device for steel moment-resisting frames, which...

Floor isolation is an alternative to base isolation for protecting a specific group of equipment installed on a single floor or room in a fixed‐base structure. The acceleration of the isolated floor should be mitigated to protect the equipment, and the displacement needs to be suppressed, especially under long‐period motions, to save more space for...

A unidirectional hybrid control shake table was constructed at the NEES lab at the University of California Berkeley. The 2 m by 6 m table is controlled using an MTS 493 Real-Time Controller. The control system provides PID closed loop control. The ability to have real-time hybrid shake table control is especially important for systems that have st...

The March 11th, 2011 Tohoku earthquake and subsequent tsunami caused great damage over a large region of North-Eastern portion of Japan. The magnitude of the event was not predicted and thus found Japan unprepared, especially for the effects of the tsunami. This article is a summary of observation of damage and disruption based primarily on the inf...

Base isolation practice has flourished in Japan, especially after the 1995 Kobe Earthquake. Its widespread acceptance has allowed its use to spread to more nonconventional applications such as in high-rise (taller than 60m) buildings. While only a handful of tall isolated buildings exist in the rest of the world, almost 200 isolated high-rises have...

SUMMARY Base isolation is a well known technology that has been proven to reduce structural response to horizontal ground accelerations. However, vertical response still remains a topic of concern for base-isolated buildings, perhaps more so than in fixed-base buildings as isolation is often used when high performance is required. To investigate th...

Although the ability to simulate accurately the detailed behavior of nonlinear isolation bearings and the effects of this nonlinearity on dynamic response of the isolated building is desirable, such detailed analyses are not feasible during initial design stages when bearing properties are being selected. However, it would be very beneficial to be...

This paper presents numerical modeling techniques to capture the behavior of the triple friction pendulum (TFP) isolation bearing when rotation is permitted about the horizontal axes of the top and bottom components. This paper builds on a previous model for the TFP bearing presented by the authors that is based on the kinematic and constitutive re...

A floor isolation system installed in a single floor or room in a fixed base structure is designed to protect equipment. With this configuration, the input motions to the floor isolation from the ground motions are filtered by the structure, leaving the majority of the frequency content of the input motion lower than the predominant frequency of th...

This paper addresses the treatment of the rotation of the internal components of the triple friction pendulum (TFP) isolation bearing in a numerical model previously presented by the authors. The numerical model is based on the kinematic behavior of the individual sliding surfaces and the constitutive relationships between them. The modification su...

This paper presents a non‐linear, kinematic model for triple friction pendulum isolation bearings. The model, which incorporates coupled plasticity and circular restraining surfaces for all sliding surfaces, is capable of capturing bi‐directional behavior and is able to explicitly track the movement of each internal component. The model is general...

The number of base isolated building in Asian countries, especially Japan, far outstrips the number in the United States. Base isolated buildings in Japan number in the thousands while the number in the U.S. remains around one hundred. Unlike its use in Japan, isolation technology in the U.S. has remained within mainly essential, public buildings s...