Time filter

Source Type

North Richmond, CA, United States

Gilani A.S.J.,Miyamoto International Inc. | Takhirov S.,Pacific Earthquake Engineering Research Center | Reinhorn A.,State University of New York at Buffalo | Mahin S.A.,University of California at Berkeley
Structures Congress 2010

In recent years, three major ceiling grid manufacturers in the United States have conducted extensive earthquake simulator testing of suspended ceilings. The tests to date have followed the ICC-ES AC-156 protocol and have been performed on an elevated test frame of limited size. The test protocol was developed to be applicable for a wide array of nonstructural components and is referenced in the building codes as a standard when testing nonstructural components. The tests have provided researchers and engineers with invaluable data and have enabled manufacturers to assess the seismic performance of their components with a degree of reliability. However, the tests have also revealed shortcomings in the current experimental and evaluation procedures. It is proposed to develop a second-generation test protocol that takes into account the unique properties of suspended ceilings such as multiple attachment points and large floor plan, and to address evaluation questions including qualification levels and performance targets. © 2010 American Society of Civil Engineers. Source

Boore D.M.,U.S. Geological Survey | Goulet C.A.,Pacific Earthquake Engineering Research Center
Bulletin of Earthquake Engineering

The most commonly used intensity measure in ground-motion prediction equations is the pseudo-absolute response spectral acceleration (PSA), for response periods from 0.01 to 10 s (or frequencies from 0.1 to 100 Hz). PSAs are often derived from recorded ground motions, and these motions are usually filtered to remove high and low frequencies before the PSAs are computed. In this article we are only concerned with the removal of high frequencies. In modern digital recordings, this filtering corresponds at least to an anti-aliasing filter applied before conversion to digital values. Additional high-cut filtering is sometimes applied both to digital and to analog records to reduce high-frequency noise. Potential errors on the short-period (high-frequency) response spectral values are expected if the true ground motion has significant energy at frequencies above that of the anti-aliasing filter. This is especially important for areas where the instrumental sample rate and the associated anti-aliasing filter corner frequency (above which significant energy in the time series is removed) are low relative to the frequencies contained in the true ground motions. A ground-motion simulation study was conducted to investigate these effects and to develop guidance for defining the usable bandwidth for high-frequency PSA. The primary conclusion is that if the ratio of the maximum Fourier acceleration spectrum (FAS) to the FAS at a frequency fsaa corresponding to the start of the anti-aliasing filter is more than about 10, then PSA for frequencies above fsaa should be little affected by the recording process, because the ground-motion frequencies that control the response spectra will be less than fsaa. A second topic of this article concerns the resampling of the digital acceleration time series to a higher sample rate often used in the computation of short-period PSA. We confirm previous findings that sinc-function interpolation is preferred to the standard practice of using linear time interpolation for the resampling. © Springer Science+Business Media Dordrecht (outside the USA) 2013. Source

Trono W.,Exponent, Inc. | Jen G.,University of California at Berkeley | Panagiotou M.,University of California at Berkeley | Schoettler M.,Pacific Earthquake Engineering Research Center | Ostertag C.P.,University of California at Berkeley
Journal of Bridge Engineering

This paper presents the shake-table tests of a damage-resistant posttensioned bridge column designed to rock at the interface with its foundation. It compares the response to that of a conventional bridge column detailed to conform with current California seismic design criteria. The lower portion of the rocking column was built using hybrid fiber-reinforced concrete (HYFRC) and was armored with headed rebars; these features enhanced the compression damage resistance at the column base. Unbonded rebars that crossed the rocking plane provided hysteretic energy dissipation. Both columns were subjected to a sequence of scaled historical triaxial earthquake ground motions including near-fault pulse-like motions. The conventional column formed a flexural plastic hinge with extensive spalling. It accumulated a 6.8% residual drift ratio after a sequence of seven ground motions, which caused a peak drift ratio of 10.8%. The posttensioned-HYFRC column sustained only light damage and accumulated only a 0.4% residual drift ratio after the same seven ground motions, which caused a peak drift ratio of 8.0%. © 2014 American Society of Civil Engineers. Source

Stewart J.P.,University of California at Los Angeles | Abrahamson N.A.,Pacific Gas and Electric Company | Atkinson G.M.,University of Western Ontario | Baker J.W.,Stanford University | And 8 more authors.
Earthquake Spectra

The 2009 NEHRP Provisions modified the definition of horizontal ground motion from the geometric mean of spectral accelerations for two components to the peak response of a single lumped mass oscillator regardless of direction. These maximum-direction (MD) ground motions operate under the assumption that the dynamic properties of the structure (e.g., stiffness, strength) are identical in all directions. This assumption may be true for some in-plan symmetric structures, however, the response of most structures is dominated by modes of vibration along specific axes (e.g., longitudinal and transverse axes in a building), and often the dynamic properties (especially stiffness) along those axes are distinct. In order to achieve structural designs consistent with the collapse risk level given in the NEHRP documents, we argue that design spectra should be compatible with expectedlevels of ground motion along those principal response axes. The use of MD ground motionseffectively assumes that the azimuth of maximum ground motion coincides with the directions of principal structural response. Because this is unlikely, design ground motions havelower probability of occurrence than intended, with significant societal costs. We recommend adjustments to make design ground motions compatible with target risk levels. © 2011, Earthquake Engineering Research Institute. Source

McKenna F.,Pacific Earthquake Engineering Research Center
Computing in Science and Engineering

Structural engineers face many challenges in attempting to analyze and design structures that can withstand the devastating effects of earthquakes. The OpenSees software framework seeks to aid in this challenging task by letting earthquake engineers develop finite-element and finite-element-reliability applications for use in sequential, high-performance, and distributed processing environments. © 2011 IEEE. Source

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