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11.
A retrofit procedure for existing buildings called the "weakening and damping technique" (WED) is presented in this paper. Weakening of structures can limit the maximum response accelerations during severe ground motions, but leads to an increase in the displacements or inter-story drifts. Added damping by using viscous dampers, on the other hand, reduces the inter-story drifts and has no significant effect on total accelerations, when structures behave inelastically. The weakening and damping technique addresses the two main causes for both structural and nonstructural damage in structures. The weakening retrofit is particularly suitable for structures that have overstressed components and weak brittle components. In this paper, the advantages of the WeD are verified by nonlinear dynamic analysis and simplified spectral approach that has been modified to fit structures with additional damping devices. A hospital structure located in the San Femando Valley in California is selected as a case study. The results from both analyses show that the retrofit solution is feasible to reduce both structural acceleration and displacement. A sensitivity analysis is also carried out to evaluate the effectiveness of the retrofitting method using different combinations of performance thresholds in accelerations and displacements through fragility analysis. 相似文献
12.
High spatial resolution observations (approximately 5") were made for the 3 mm transitions of methanol (CH3OH), methyl formate (HCOOCH3), and dimethyl ether [(CH3)2O] toward Orion-KL using the Nobeyama Millimeter Array. The 15(3)-14(4) A- CH3OH emission appears to be elongated along the line connecting IRc2 and "the southern condensation (SC)", which may suggest a relation between methanol and the outflow from IRc2. The HCOOCH3 (7(1,6)-6(1,5)) and (CH3)2O (15(2,13)-15(1,14)) emissions appear to be well concentrated toward SC with an angular size of approximately 6".5 (at the 2 sigma level). There also exists another oxygen-rich condensation to the west of IRc2 (angular size approximately 4".5) having column densities of HCOOCH3 and (CH3)2O comparable to those of SC. We derive the total column densities 6.8 x 10(16) cm-2, 1.4 x 10(16) cm-2 and 2.7 x 10(16) cm-2 for CH3OH, HCOOCH3, and (CH3)2O, respectively, at the core of SC. 相似文献
13.
Acta Geotechnica - The results of an experimental investigation on Malaysian kaolin under monotonic and cyclic loading are presented. In the tests, a wide range of initial conditions was varied in... 相似文献
14.
Modeling and cyclic behavior of segmental bridge column connected with shape memory alloy bars 总被引：1，自引：1，他引：0
This paper examines the quasi-static cyclic behavior,lateral strength and equivalent damping capacities of a system of post-tensioned segmental bridge columns tied with large diameter martensitic Shape Memory Alloy(SMA) link-bars.Moment-curvature constitutive relationships are formulated and analysis tools are developed for the PT column,including a modified four-spring model prepared for the SMA bars.The suggested system is exemplified using a column with an aspect ratio of 7.5 and twelve 36.5 mm diameter NiTi martensitic SMA bars.A post-tensioning force of 40% to 60% of the tendon yield strength is applied in order to obtain a self re-centering system,considering the residual stress of the martensitic SMA bars.The cyclic response results show that the lateral strength remains consistently around 10% of the total vertical load and the equivalent viscous damping ratios reach 10%-12% of critical.When large diameter NiTi superelastic SMA bars are incorporated into the column system,the cyclic response varies substantially.The creep behavior of the superelastic SMA bar is accounted for since it affects the re-centering capability of the column.Two examples are presented to emphasize the modeling sensitivities for these special bars and quantify their cyclic behavior effects within the column assembly. 相似文献
15.
Hitoshi Tanaka Kosuke Kayane Mohammad Bagus Adityawan Min Roh Mohammad Farid 《Ocean Dynamics》2014,64(9):1319-1332
The relations of river morphology and tsunami propagation in rivers were studied at several rivers in the Tohoku region during The Great Chilean Tsunami of 2010 and The Great East Japan Tsunami of 2011. It was found that river mouth morphological features play an important role in the intrusion of low magnitude tsunamis in which the geological and geographical conditions are an important factor. Nevertheless, the effects of these features were not found in the case of an extreme tsunami wave. As the wave enters the river, the propagation depends on other factors. It was found that the intrusion distance correlates well to the riverbed slope. The measurements of water level and riverbed slope were analyzed to propose an empirical method for estimating the damping coefficient for the tsunami propagation in rivers based on the tsunami of 2011. The proposed empirical method was used to approximate the length of the tsunami intrusion into a river by assuming that the furthest distance is given for the ratio of local tsunami wave height to the tsunami wave height at the river entrance of 0.05 (5 %). The estimated intrusion length from the proposed method in this study shows a good comparison with measurement data. 相似文献
16.
The impact of geochemical processes and microbial activity has been a major concern for the long-term performance of reactive
iron barriers because corrosion products and precipitates during the water treatment with reactive materials will decrease
the reactivity and permeability of the iron bed. This study characterizes corrosion products in reactive iron barrier as well
as evaluates the effect of the iron corrosion products and precipitates on iron wall performance during contaminated-water
treatment under varying conditions. Major phases in the reactive iron barrier include iron oxides, carbonates, iron sulfides,
and elemental sulfur, depending on the degree of iron oxidation, groundwater chemistry, and microbial activity. Detailed geochemical
and mineralogical characteristics are imperative for long-range predictions of the reactive iron wall performance on water
treatment because the surface coating materials reduce the effectiveness of the zero-valent iron media.
Received: 17 September 1999 · Accepted: 11 April 2000 相似文献
17.
18.
Owen A. Anfinson Martin G. Lockley Sam Hyang Kim Kyung Soo Kim Jeong Yul Kim 《Cretaceous Research》2009,30(4):885-894
Although body fossils of shorebirds and shorebird-like species are extremely rare from the Cretaceous, rapid increase in the discovery of bird footprint sites provides valuable alternate evidence to help fill gaps in the story of the early evolution of shorebird-like species. Newly discovered bird tracks from the Albian-Cenomanian Dakota Formation in northeastern Utah represent the first report of the ichnogenus Koreanaornis from North America and only the second report of bird tracks from this formation. These tracks are not attributable to Aquatilavipes as previously claimed. Three well-preserved trackways are described and provisionally referred to Koreanaornis cf. hamanensis (Kim). However, a review of the ichnotaxonomy of shorebird ichnites reveals that this ichnotaxon also closely resembles the Miocene ichnospecies Avipeda sirin (Vyalov). This latter comparison points to the need for a thorough evaluation of the similarity between Mesozoic and Cenozoic avian ichnotaxa, which may be over-split in some cases and under-differentiated in others.The new material helps distinguish ichnogenus Koreanaornis from the larger bird track Aquatilavipes, which is more abundant and widespread in North America. In some cases Aquatilavipes has been incorrectly used as a catch-all ichnogenus both in North America and Asia. The Dakota Formation stratigraphy at the tracksite indicates that the track makers lived in a marginal marine paleoenvironment. However, despite the widespread distribution of such facies, often replete with dinosaur tracks, the bird track record of the Dakota Formation, and the Cretaceous of the western USA remains relatively sparse in comparison with other areas such as east Asia. 相似文献
19.
The Field Research Center (FRC) including five contaminated sites and a clean background area was established in Oak Ridge,
Tennessee, as a part of the U.S. Department of Energy’s Natural and Accelerated Bioremediation Research (NABIR) program. This
study investigates the mineralogy and mineralogical pathways of saprolite at the FRC background site to provide a fundamental
basis for the remediation strategy for contaminated sites. The background site is underlain interbedded shales, siltstones,
and limestones with nearly identical characteristics to the contaminated sites. Bulk samples of saprolite were collected by
hand picking approximately at 1 m depth (C horizon) from the soil surface. The soil pH of 4.3 and cation exchange capacity
(CEC) of 10.5 cmol/kg measured are in the range of the typical shallow depth saprolite layer in this area. Total Fe by citrate-bicarbonate-dithionate
(CBD) and ammonium oxalate extractable (amorphous) were 17.6 and 0.61 g/kg, respectively. Total Mn extracted by NH2OH·HCl was 0.17 g/kg. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses indicate that quartz, illite,
and microcline (K-feldspar) are the dominant minerals, occupying 95% of mineral composition. The saprolite samples analyzed
have shown characteristics of oxic conditions overall, and the degrees of weathering for three sampling locations were various,
most for S1 and least for S3, likely influenced either by the flow channels developed through saprolite or by seasonal fluctuation
of the groundwater table. The source of the manganese oxide that observed from the site is likely to be Mn-rich muscovite
in the shale or Mn-rich biotite in the blackish band in the limestone. The results such as abundant Mn and Fe contents identified
encouraging prospects for conducting remediation projects in FRC sites. 相似文献
20.
In previous research, winter weather conditions like precipitation and cold were recognized as factors affecting the change in traffic volume, and a simulation has been conducted to model the effect of weather factor on variations in traffic flow. A winter weather hazard model considering natural chronic hazards in the winter season has been proposed. To achieve this purpose, this research formulated a dummy variable winter weather traffic model while considering explanatory variables such as expected daily volume, snowfall, and temperature. This model was derived using six-year traffic data that were collected on a weigh-in-motion site on Highway 44, in Alberta, Canada. Precipitation and cold data collected from a weather station were linked with traffic data to model traffic variations caused by weather factors. The performance of the model, on the ground of temporal transferability and model specification, was tested using data from different years. The temporal transferability test confirmed that the model can be successfully applied regardless of the year. It was also revealed that each vehicle class prefers a different model specification in estimating correct traffic volume.
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