63 research outputs found
Semi-empirical relationships to assess the seismic performance of slopes from an updated version of the Italian seismic database
Funder: Dipartimento della Protezione Civile, Presidenza del Consiglio dei Ministri; doi: http://dx.doi.org/10.13039/100012783; Grant(s): ReLUIS research project - Working Pachage 16: Geotechnical Engineering - Task Group 2: Slope stabilityAbstractSeismic performance of slopes can be assessed through displacement-based procedures where earthquake-induced displacements are usually computed following Newmark-type calculations. These can be adopted to perform a parametric integration of earthquake records to evaluate permanent displacements for different slope characteristics and seismic input properties. Several semi-empirical relationships can be obtained for different purposes: obtaining site-specific displacement hazard curves following a fully-probabilistic approach, to assess the seismic risk associated with the slope; providing semi-empirical models within a deterministic framework, where the seismic-induced permanent displacement is compared with threshold values related to different levels of seismic performance; calibrating the seismic coefficient to be used in pseudo-static calculations, where a safety factor against limit conditions is computed. In this paper, semi-empirical relationships are obtained as a result of a parametric integration of an updated version of the Italian strong-motion database, that, in turn, is described and compared to older versions of the database and to well-known ground motion prediction equations. Permanent displacement is expressed as a function of either ground motion parameters, for a given yield seismic coefficient of the slope, or of both ground motion parameters and the seismic coefficient. The first are meant to be used as a tool to develop site-specific displacement hazard curves, while the last can be used to evaluate earthquake-induced slope displacements, as well as to calibrate the seismic coefficient to be used in a pseudo-static analysis. Influence of the vertical component of seismic motion on these semi-empirical relationships is also assessed.</jats:p
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Scaling the weak-swirl burner from 15 kW to 1 MW
With the passage of SCAQMD 1146.2, low NO{sub x} regulations will be enforced for new water heaters and boilers from 22 to 585 kW starting January 1, 2000; less than two years away. This has given an added impetus to develop a burner capable of producing NO{sub x} < 30 ppm and CO < 400 ppm without substantial manufacturing costs or complexity. Developed at the Berkeley Lab, the Weak-Swirl Burner (WSB) operates in the lean premixed combustion mode over a wide firing and equivalence ratio range. This work investigated scaling issues (e.g. swirl rates and stability limits) of the WSB when fired at higher rates useful to industry. Three test configurations which varied the ratio of furnace area to burner area were utilized to understand the effects of burner chamber coupling on emissions and stability. Preliminary tests from 12 to 18 kW of a WSB in a commercial heat exchanger were undertaken at LBNL, with further testing from 18 to 105 kW completed at UCI Combustion Laboratory in an octagonal enclosure. After scaling the small (5 cm diameter) to a 10 cm WSB, the larger burner was fired from 150 to 600 kW within a 1.2 MW furnace simulator at UCICL. Test results demonstrate that NO{sub x} emissions (15 ppm at 3% O{sub 2} at equivalence ratio {phi} = 0.80) were invariant with firing rate and chamber/burner ratio. However, the data indicates that CO and UHC are dependent on system parameters, such that a minimum firing rate exists below which CO and UHC rise from lower limits of 25 ppm and 0 ppm respectively
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