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Lu J.,University of California at San Diego | Elgamal A.,University of California at San Diego | Yan L.,Tobolski Watkins Engineering Inc. | Law K.H.,Stanford University | Conte J.P.,University of California at San Diego
International Journal of Geomechanics | Year: 2012

Calibration, on the basis of data from centrifuge and shake table experiments, continues to promote the development of more accurate computational models. Capabilities such as coupled solid-fluid formulations and nonlinear incremental-plasticity approaches allow for more realistic representations of the involved static and dynamic/seismic responses. In addition, contemporary high-performance parallel computing environments are permitting new insights, gained from analyses of entire ground-foundation-structural systems. On this basis, the horizon is expanding for large-scale numerical simulations to further contribute toward the evolution of more accurate analysis and design strategies. The studies presented in this paper address this issue through recently conducted three-dimensional (3D) representative research efforts that simulate the seismic response of (1) a shallow-foundation liquefaction countermeasure, (2) a pile-supported wharf, and (3) a full bridge-ground system. A discussion of enabling tools for routine usage of such 3D simulation environments is also presented, as an important element in support of wider adoption and practical applications. In this regard, graphical user interfaces and visualization approaches can play a critical role. © 2011 American Society of Civil Engineers. Source


Watkins D.A.,Tobolski Watkins Engineering Inc. | Watkins D.A.,University of California at San Diego | Hutchinson T.C.,University of California at San Diego | Hoehler M.S.,Fastening and Applications for Hilti Corporation
ACI Structural Journal | Year: 2012

The seismic performance of anchors in cracked concrete has historically been investigated under load and boundary conditions that do not fully represent the dynamic environment encountered when a structure is subjected to earthquake loads. Few investigations have considered the complex interplay between anchor behavior and the components they connect. This paper presents a new methodology and associated experimental setup for studying the seismic behavior of anchored components. This study aims at capturing the salient features of boundary and loading conditions of anchored components within building systems, whereby the component is subjected to seismic-induced inertial loading, while the anchor is embedded in cracks that cycle between opened and closed. Although the emphasis is on testing anchored nonstructural components and systems, the methodology and test equipment are versatile enough to accommodate structural components as well. The experimental results demonstrate the fidelity of the system across a broad frequency range and under a variety of dynamic loading conditions. Copyright © 2012, American Concrete Institute. All rights reserved. Source


Hutchinson T.C.,University of California at San Diego | Zhang J.,Nanjing Southeast University | Eva C.,Tobolski Watkins Engineering Inc.
Earthquake Spectra | Year: 2011

In this paper, two new protocols are proposed, developed based on cycle counting and forward ordering of interstory drift time histories for representative mid- and low-rise building structures. The proposed drift protocols involve: (i) ground motion selection and scaling, (ii) representative building selection and modeling, (iii) nonlinear structural dynamic response calculations, and (iv) modified simple range counting to derive amplitude count information. In this work, demand sequencing is considered. This aspect is important, as excursions with the same amplitude occurring at different times will contribute differently to structural damage; therefore, they are sequenced and weighted differently. For this purpose, a damage index concept is used to evaluate each excursion and define instantaneous weight factors. The protocols are applied to a series of in-plane racking tests on window systems. Damage modes and associated drift limits are compared for the proposed protocols as well as several others, namely; a monotonic (static) push, the "Crescendo" (dynamic) loading protocol, and the FEMA 461 (quasistatic) loading protocol. © 2011, Earthquake Engineering Research Institute. Source


Reigles D.G.,EngNoveX Inc. | Brachmann I.,Bechtel Corporation | Johnson W.H.,Bechtel Corporation | Gurbuz O.,Tobolski Watkins Engineering Inc.
Nuclear Engineering and Design | Year: 2016

Nuclear power plant safety-related cable tray support systems subjected to seismic loadings were originally understood and designed to behave as linear elastic systems. This behavioral paradigm persisted until the early 1980s when, due to evolution of regulatory criteria, some as-installed systems needed to be qualified to higher seismic motions than originally designed for. This requirement prompted a more in-depth consideration of the true seismic response behavior of support systems. Several utilities initiated extensive test programs, which demonstrated that trapeze strut-type cable tray support systems exhibited inelastic and nonlinear response behaviors with plastic hinging at the connections together with high damping due to bouncing of cables in the trays. These observations were used to demonstrate and justify the seismic adequacy of the aforementioned as-installed systems. However, no formalized design methodology or criteria were ever established to facilitate use of these test data for future evaluations. This paper assimilates and reviews the various test data and conclusions for the purpose of developing a design methodology for the seismic qualification of safety-related cable tray support systems. © 2016 Elsevier B.V. All rights reserved. Source

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