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21.
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 impact on behavior of structures isolated on general bilinear isolators. However, testing of triple friction pendulum (TFP) sliding bearings has not been done dynamically or incorporated into a building system. Here, one‐third scale laboratory tests were conducted to on a 2‐story 2‐bay TFP‐isolated structure. Input motions were increasingly scaled until failure occurred at the isolation level. As the superstructure was designed with a yield force equivalent to the force of the bearing just at their ultimate displacement capacity, there was minimal yielding. A numerical model is presented to simulate the isolated building up to and including bearing failure. Forces transferred to the superstructure in extreme motions are examined using both experimental and numerical data. Additionally, the effect of the hardening stage of the TFP bearing is evaluated using the numerical model, finding slight benefits. 相似文献
22.
Laura Sandri Gill Jolly Jan Lindsay Tracy Howe Warner Marzocchi 《Bulletin of Volcanology》2012,74(3):705-723
By using BET_VH, we propose a quantitative probabilistic hazard assessment for base surge impact in Auckland, New Zealand.
Base surges resulting from phreatomagmatic eruptions are among the most dangerous phenomena likely to be associated with the
initial phase of a future eruption in the Auckland Volcanic Field. The assessment is done both in the long-term and in a specific
short-term case study, i.e. the simulated pre-eruptive unrest episode during Exercise Ruaumoko, a national civil defence exercise.
The most important factors to account for are the uncertainties in the vent location (expected for a volcanic field) and in
the run-out distance of base surges. Here, we propose a statistical model of base surge run-out distance based on deposits
from past eruptions in Auckland and in analogous volcanoes. We then combine our hazard assessment with an analysis of the
costs and benefits of evacuating people (on a 1 × 1-km cell grid). In addition to stressing the practical importance of a
cost-benefit analysis in creating a bridge between volcanologists and decision makers, our study highlights some important
points. First, in the Exercise Ruaumoko application, the evacuation call seems to be required as soon as the unrest phase
is clear; additionally, the evacuation area is much larger than what is recommended in the current contingency plan. Secondly,
the evacuation area changes in size with time, due to a reduction in the uncertainty in the vent location and increase in
the probability of eruption. It is the tradeoff between these two factors that dictates which cells must be evacuated, and
when, thus determining the ultimate size and shape of the area to be evacuated. 相似文献
23.
Sachi Furukawa Eiji Sato Yundong Shi Tracy Becker Masayoshi Nakashima 《地震工程与结构动力学》2013,42(13):1931-1949
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 the effects of vertical response on building contents and nonstructural components, a series of full‐scale shaking table tests were conducted at the E‐Defense facility in Japan. A four‐story base‐isolated reinforced concrete building was outfitted as a medical facility with a wide variety of contents, and the behavior of the contents was observed. The rubber base isolation system was found to significantly amplify vertical accelerations in some cases. However, the damage caused by the vertical ground motions was not detrimental when peak vertical floor accelerations remained below 2 g with three exceptions: (1) small items placed on shelves slid or toppled; (2) objects jumped when placed on nonrigid furniture, which tended to increase the response; and (3) equipment with vertical eccentricities rocked and jumped. In these tests, all equipment and nonstructural components remained functional after shaking. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
24.
25.
Fiona?V.?FoleyEmail author Simon?Turner Tracy?Rushmer John?T.?Caulfield Nathan?R.?Daczko Paul?Bierman Matthew?Robertson Craig?D.?Barrie Adrian?J.?Boyce 《Contributions to Mineralogy and Petrology》2014,168(3):1048
Subduction-related Quaternary volcanic rocks from Solander and Little Solander Islands, south of mainland New Zealand, are porphyritic trachyandesites and andesites (58.20–62.19 wt% SiO2) with phenocrysts of amphibole, plagioclase and biotite. The Solander and Little Solander rocks are incompatible element enriched (e.g. Sr ~931–2,270 ppm, Ba ~619–798 ppm, Th ~8.7–21.4 ppm and La ~24.3–97.2 ppm) with MORB-like Sr and Nd isotopic signatures. Isotopically similar quench-textured enclaves reflect mixing with intermediate (basaltic-andesite) magmas. The Solander rocks have geochemical affinities with adakites (e.g. high Sr/Y and low Y), whose origin is often attributed to partial melting of subducted oceanic crust. Solander sits on isotopically distinct continental crust, thus excluding partial melting of the lower crust in the genesis of the magmas. Furthermore, the incompatible element enrichments of the Solander rocks are inconsistent with partial melting of newly underplated mafic lower crust; reproduction of their major element compositions would require unrealistically high degrees of partial melting. A similar argument precludes partial melting of the subducting oceanic crust and the inability to match the observed trace element patterns in the presence of residual garnet or plagioclase. Alternatively, an enriched end member of depleted MORB mantle source is inferred from Sr, Nd and Pb isotopic compositions, trace element enrichments and εHf ? 0 CHUR in detrital zircons, sourced from the volcanics. 10Be and Sr, Nd and Pb isotopic systematics are inconsistent with significant sediment involvement in the source region. The trace element enrichments and MORB-like Sr and Nd isotopic characteristics of the Solander rocks require a strong fractionation mechanism to impart the high incompatible element concentrations and subduction-related (e.g. high LILE/HFSE) geochemical signatures of the Solander magmas. Trace element modelling shows that this can be achieved by very low degrees of melting of a peridotitic source enriched by the addition of a slab-derived melt. Subsequent open-system fractionation, involving a key role for mafic magma recharge, resulted in the evolved andesitic adakites. 相似文献
26.
27.
Katharine McKinnon Melissa Kennedy Jo Barraket Tracy DeCotta 《The Australian geographer》2020,51(3):361-375
ABSTRACT Work Integration Social Enterprises (WISE) offer supported work environments for people experiencing disadvantage, including people with disability. This paper reflects on a research project that is mapping the ways in which social enterprises in regional Australian cities produce wellbeing for their employees. Through supported employment programs, these organisations are transforming individual lives, helping to build a sense of self-worth and purpose, and increase individuals’ social skills and capacities. Many of the perceived benefits are associated with a belief in the innate good of paid work. Based upon interviews with employees in the social enterprises, it is apparent that the hopes attached to providing ‘meaningful work’ are considerable. At the same time social enterprises are taking on social responsibilities that were once provided by the state, while also selling their services as employers of disabled and disadvantaged members of society and maintaining commercial viability of the enterprise. Using feminist political economy alongside discussion of the distributive economy, this paper explores how contemporary policy conditions, productivist biases and normative discourses about the value of wage work inflect the forms of wellbeing that can be experienced by WISE workers. 相似文献
28.
J.R. Thigpen R.D. Law C.L. Loehn R. A. Strachan R.J. Tracy G.E. Lloyd B.L. Roth S.J. Brown 《Journal of Metamorphic Geology》2013,31(8):813-842
In the Caledonides of northwest Scotland, two independent geothermometers (Fe‐Mg exchange and quartz c‐axis fabric opening angle) are used to characterize the thermal structure of the lower part of the Scandian (435–420 Ma) orogenic wedge within the Moine, Ben Hope and Naver‐Sgurr Beag thrust sheets. Traced from west (foreland) to east (hinterland), Fe‐Mg exchange thermometry yields peak or near‐peak temperatures ranging from 484 ± 50 °C to 524 ± 50 °C in the immediate hangingwall of the Moine thrust to 601 ± 50 °C in the immediate hangingwall of the Ben Hope thrust, to 630 ± 50 °C in the Naver thrust sheet. Preserved metamorphic facies and textural relationships are consistent with thermometric estimates. Deformation temperatures calculated from quartz c‐axis fabric opening angles across two similar orogen‐perpendicular transects also yield systematic increases (Glen Golly – Ben Klibreck, 520–630 °C; Ullapool‐Contin, 465–632 °C) traced towards the Naver and Sgurr Beag thrusts. In addition, deformation temperatures show a pronounced increase along the leading edge of the Moine thrust sheet moving south towards the Assynt window, which is interpreted to reflect deeper exhumation of the thrust plane above the Assynt footwall imbricate stack. Because temperatures calculated from metamorphic assemblages are within error of the quartz fabric‐derived deformation temperatures that are of demonstrably Scandian age, the metamorphic sequence between the Moine and Naver‐Sgurr Beag thrusts is interpreted to have developed during the Scandian orogeny. Integration of our results with previous 2D thermal‐mechanical studies allows development of new conceptual thermal‐kinematic models of Scandian orogenesis that may be broadly applicable to other collisional systems. Furthermore, it highlights the critical nature of coupling between orogen kinematic and thermal evolution. 相似文献
29.
Improvements to Griggs-type apparatus for mechanical testing at high pressures and temperatures 总被引:2,自引:0,他引:2
Tracy N. Tingle Harry W. Green Jr. Thomas E. Young Ted A. Koczynski 《Pure and Applied Geophysics》1993,141(2-4):523-543
New and improved techniques and apparatus for testing the mechanical properties of materials at high presures and temperatures are described. These include an improved Griggs-type deformation apparatus designed to operate to 5 GPa and associated servo-controlled hydraulic drive and electronics, the design of hydrostatic (molten alkali halide mixtures) pressure assemblies to measure flow stresses as low as a few MPa, the characterization of temperature gradients and friction in such assemblies, measurement of the melting curve of an alkali halide mixture used as a confining pressure medium, and the measurement of acoustic emissions. 相似文献
30.
Elisabeth A. Parfitt Tracy K. P. Gregg Deborah K. Smith 《Journal of Volcanology and Geothermal Research》2002,113(1-2)
Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and volumes of eruptions on the Puna Ridge, which is the submarine extension of the ERZ. Eruptions on the Puna Ridge fall into the same five classes as, and are of comparable volume to, those on the subaerial ERZ. Evidence is presented which suggests that feeder dikes for Puna Ridge eruptions are more thermally viable than those feeding subaerial eruptions, and this difference causes long-lived, large-volume eruptions to be more common on the Puna Ridge than on the subaerial ERZ. This systematic variation in thermal viability may be due to increased dike width for Puna Ridge dikes or increased pressure gradients driving magma flow. Lateral dike emplacement is common to many basaltic systems including on other Hawaiian volcanoes, in Iceland and at mid-ocean ridges. The systematic trend inferred for the ERZ of Kilauea implies that in the other systems large-volume eruptions may also be more common at great distances than they are close to the magma centre. 相似文献