Base isolation can be used both to protect the structure and simultaneously to reduce the response of internal equipment. The seismic response of a base-isolated structure has been studied through the shaking table test or numerical calculation before. The object of this paper is to analyse a base-isolated structure by a different analytical approach—perturbation analysis. Recognizing that the horizontal stiffness of an isolation system is much smaller than that of the superstructure, the mathematical expressions of the modal properties of base-isolated structures are derived by the perturbation method in terms of the modal properties of the superstructure and used to study the dynamic response of superstructure and attached equipment in the base-isolated building. This study shows that the first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. The contribution of higher modes to the response of base-isolated structures, which is proportional to the horizontal stiffness of isolation system, is very small. 相似文献
The idea that a building can be uncoupled from the damaging effects of the ground movement produced by a strong earthquake has appealed to inventors and engineers for more than a century. Many ingenious devices have been proposed to achieve this result, but very few have been tried and the concept now generally referred to as base isolation or seismic isolation has yet to become acceptable to the engineering profession as a whole. Although most of the proposed systems are unacceptably complicated, in recent years a few practical systems have emerged and have been implemented. While some of these systems have been tested on large-scale shaking tables, none has to date been tested as built by a strong earth tremor. The shake testing and related static testing of full-scale components such as isolation bearings, however, has led to a certain degree of acceptance by the profession and it is possible that the number of practical implementations of base isolation will increase quite dramatically in the next few years.
This review summarizes much of the literature on theoretical aspects of seismic isolation, describes testing programmes and enumerates those isolation systems which have been used in buildings completed or under construction. It describes the characteristics of the various implemented systems with an indication of their range of applicability and some assessment of their development as backed by research. A bibliography of all papers published on the topic from 1900 to 1984 is included. The bibliography is as complete as possible, but, due to the rapid increase in research interest in the topic in the past few years, there may be a substantial degree of omission in the later years. 相似文献
The groundwater system in northern Perry Township in Lake County, Ohio, is a shallow, unconfined aquifer consisting of periglacial
lake beach deposits and less permeable lacustrine plain deposits. Groundwater flow is generally toward Lake Erie from south
to north and is controlled by the top of the Ashtabula Till, but strong, local variations are caused by northward flowing
streams During the study period, water levels in most wells exhibited a seasonal fluctuation of less than 0 3 m from their
mean values. The areal distributions of chloride and nitrate concentrations indicate that road salt runoff easily infiltrates
the aquifer and that nitrate may be sourced from fertilizer application. Ground-water flow and solute transport models indicate
that in excess of 27 years are required to obtain chemical steady-state under hydrologic steady-state conditions. The simulations
also demonstrate that nitrate loading must occur in more than one cultivated field in order to obtain the observed wide-spread
nitrate distribution. 相似文献
This investigation was designed to estimate the mass loading of nitrate (NO3−) and herbicides in spring water discharging from groundwater basins in an agriculturally dominated, mantled karst terrain. The loading was normalized to land use and NO3− and herbicide losses were compared to estimated losses in other agricultural areas of the Midwestern USA. Our study area consisted of two large karst springs that drain two adjoining groundwater basins (total area of 37.7 km2) in southwestern Illinois' sinkhole plain, USA. The springs and stream that they form were monitored for almost 2 years. Nitrate–nitrogen (NO3–N) concentrations at three monitoring sites were almost always above the background concentration (1.9 mg/l). NO3–N concentrations at the two springs ranged from 1.08 to 6.08 with a median concentration of 3.61 mg/l. Atrazine and alachlor concentrations ranged from <0.01 to 34 μg/l and <0.01 to 0.98 μg/l, respectively, with median concentrations of 0.48 and 0.12 μg/l, respectively. Approximately 100,000 kg/yr of NO3–N, 39 kg/yr of atrazine, and 2.8 kg/yr of alachlor were discharged from the two springs. Slightly more than half of the discharged NO3− came from background sources and most of the remainder probably came from fertilizer. This represents a 21–31% loss of fertilizer N from the groundwater basins. The pesticide losses were 3.8–5.8% of the applied atrazine, and 0.05–0.08% of the applied alachlor. The loss of atrazine adsorbed to the suspended solid fraction was about 2 kg/yr, only about 5% of the total mass of atrazine discharged from the springs. 相似文献
ABSTRACTThis article situates the 2015 rebranding of Zuckerberg San Francisco General within San Francisco’s technopolitical landscape. After Facebook’s CEO Mark Zuckerberg donated to the hospital, thereby acquiring naming rights, local toponymical tension percolated. This was in part due to Facebook’s gentrifying role in the city and the racial violence such processes constitute, as well as ongoing practices data colonialism. The latter includes Facebook’s attempt at pairing hospital data with user data in order to augment its scope into intimate and bodily geographies. In exploring the intertwining of gentrification and data colonialism, here I forge the concept of techno-imperialism as an analytic and as a point of departure in understanding Facebook’s multi-scalar impacts. As I suggest, the transformation of “The General” to “The Zuckerberg” indexes the company's techno-imperiality, as well as its efforts to mask its dispossessive impacts. 相似文献
Geographic citizen science has much potential to assist in wildlife research and conservation, but the quality of observation data is a key concern. We examined the effects of sampling design on the quality of spatial data collected for a koala citizen science project in Australia. Data were collected from three samples—volunteers (n = 454), an Internet panel (n = 103), and landowners (n = 35)—to assess spatial data quality, a dimension of citizen science projects rarely considered. The locational accuracy of koala observations among the samples was similar when benchmarked against authoritative data (i.e., an expert‐derived koala distribution model), but there were differences in the quantity of data generated. Fewer koala location data were generated per participant by the Internet panel sample than the volunteer or landowner samples. Spatial preferences for land uses affecting koala conservation were also mapped, with landowners more likely to map locations for residential and tourism development and volunteers less likely. These spatial preferences have the potential to influence the social acceptability of future koala conservation proposals. With careful sampling design, both citizen observations and land use preferences can be included within the same project to augment scientific assessments and identify conservation opportunities and constraints. 相似文献
Ocean Science Journal - A minimum 19 year tidal prediction dataset covering nodal (satellite) modulation effects is required to determine the Lowest Astronomical Tide (LAT) and Highest Astronomical... 相似文献