319 research outputs found

    STR-875: PREDICTING FAILURE IN SLIDING ISOLATION BEARINGS UNDER LONG-PERIOD MOTIONS

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    For the majority of structural systems, there has been a push to understand collapse behaviour and to quantify collapse margin ratios. However, for seismic isolation there is still significant work to be done in this area, especially for sliding bearings, for which little research on failure has been investigated. While it may be the goal of the designer that isolation bearing capacity is not reached, for performance based design it is essential to understand how and under what levels the bearing will fail. To investigate failure, a model based on the theory of rigid body kinematics, rigid body dynamics and contact mechanics is employed with an added parallel non-linear damper to explicitly consider the energy dissipation. Ricker pulses are extracted from long period motions and used to predict whether the bearing impacts and if that impact results in failure. The research finds that these pulses are good predictors providing that the extracted pulse periods are sufficiently long (greater than 0.5 s); otherwise the pulse does not dominate the response of the bearing. Generalized graphs are produced for use in predicting bearing performance and collapse margin ratio (assuming a rigid superstructure) at initial stages of design

    NDM-518: EFFECTS OF NON-TRADITIONAL ISOLATOR PLACEMENT FOR SEISMIC RETROFIT

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    Seismic isolation delivers improved performance by means of a flexible layer at which lateral deformation is concentrated. However, for seismic retrofit applications base isolation systems can be of considerable expense, in significant part because of major alterations required at the base of the structure. The cost of introducing an additional diaphragm, constructing a seismic gap, and modifying the foundation causes the initial cost of isolation to be significantly higher than traditional non-isolation retrofit methods. To minimize initial costs, isolators may be placed directly at the top of the column level, without an additional diaphragm, instead of at the base of the building. To investigate the effects of this placement and the limits of applicability, experiments were conducted at McMaster University of a column-bearing subassembly. These experiments tested bearings on increasing flexible steel columns, investigating the effect of allowing end rotations on the bearing behaviour and the effect of large displacements on the overall stability of the beam-column system. This research looks at developing clear strength and stiffness requirements for the sub-isolation system with the aim of increasing the number of existing buildings that are candidates for retrofit with isolation

    Photoabsorption and photoion spectroscopy of atomic uranium in the region of 6p and 5d excitations

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    The photoabsorption process in atomic uranium has been investigated experimentally and theoretically in the 15–150-eV region. Using the dual laser plasma technique, the 6p photoabsorption spectrum has been recorded while for the first time the 5d region has been remeasured photoelectrically using both photoabsorption and photoion spectroscopy. Interpretation of the photoabsorption spectra is supported by Hartree-Fock calculations which take into account spin-flip decay and the interaction of many discrete states with many continua. The 6p spectrum is entirely dominated by spin-orbit split 6p⃗6d transitions. The 5d-subshell photoabsorption is shown to consist predominantly of discrete 5d⃗5f excitations; here the electrostatic and spin-orbit interactions are comparable in strength

    The Baryon Oscillation Spectroscopic Survey of SDSS-III

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    The Baryon Oscillation Spectroscopic Survey (BOSS) is designed to measure the scale of baryon acoustic oscillations (BAO) in the clustering of matter over a larger volume than the combined efforts of all previous spectroscopic surveys of large scale structure. BOSS uses 1.5 million luminous galaxies as faint as i=19.9 over 10,000 square degrees to measure BAO to redshifts z<0.7. Observations of neutral hydrogen in the Lyman alpha forest in more than 150,000 quasar spectra (g<22) will constrain BAO over the redshift range 2.15<z<3.5. Early results from BOSS include the first detection of the large-scale three-dimensional clustering of the Lyman alpha forest and a strong detection from the Data Release 9 data set of the BAO in the clustering of massive galaxies at an effective redshift z = 0.57. We project that BOSS will yield measurements of the angular diameter distance D_A to an accuracy of 1.0% at redshifts z=0.3 and z=0.57 and measurements of H(z) to 1.8% and 1.7% at the same redshifts. Forecasts for Lyman alpha forest constraints predict a measurement of an overall dilation factor that scales the highly degenerate D_A(z) and H^{-1}(z) parameters to an accuracy of 1.9% at z~2.5 when the survey is complete. Here, we provide an overview of the selection of spectroscopic targets, planning of observations, and analysis of data and data quality of BOSS.Comment: 49 pages, 16 figures, accepted by A

    A large scale hearing loss screen reveals an extensive unexplored genetic landscape for auditory dysfunction

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    The developmental and physiological complexity of the auditory system is likely reflected in the underlying set of genes involved in auditory function. In humans, over 150 non-syndromic loci have been identified, and there are more than 400 human genetic syndromes with a hearing loss component. Over 100 non-syndromic hearing loss genes have been identified in mouse and human, but we remain ignorant of the full extent of the genetic landscape involved in auditory dysfunction. As part of the International Mouse Phenotyping Consortium, we undertook a hearing loss screen in a cohort of 3006 mouse knockout strains. In total, we identify 67 candidate hearing loss genes. We detect known hearing loss genes, but the vast majority, 52, of the candidate genes were novel. Our analysis reveals a large and unexplored genetic landscape involved with auditory function
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