A performance-based adaptive methodology for the seismic assessment of highway bridges is proposed. The proposed methodology
is based on an Inverse (I), Adaptive (A) application of the Capacity Spectrum Method (CSM), with the capacity curve of the
bridge derived through a Displacement-based Adaptive Pushover (DAP) analysis. For this reason, the acronym IACSM is used to
identify the proposed methodology. A number of Performance Levels (PLs), for which the seismic vulnerability and seismic risk
of the bridge shall be evaluated, are identified. Each PL is associated to a number of Damage States (DSs) of the critical
members of the bridge (piers, abutments, joints and bearing devices). The IACSM provides the earthquake intensity level (PGA)
corresponding to the attainment of the selected DSs, using over-damped elastic response spectra as demand curves. The seismic
vulnerability of the bridge is described by means of fragility curves, derived based on the PGA values associated to each
DS. The seismic risk of the bridge is evaluated as convolution integral of the product between the fragility curves and the
seismic hazard curve of the bridge site. In this paper, the key aspects and basic assumptions of the proposed methodology
are presented first. The IACSM is then applied to nine existing simply supported deck bridges, characterized by different
types of piers and bearing devices. Finally, the IACSM predictions are compared with the results of nonlinear response time-history
analysis, carried out using a set of seven ground motions scaled to the expected PGA values. 相似文献
Papandayan is a stratovolcano situated in West Java, Indonesia. Since the last magmatic eruption in 1772, only few hydrothermal explosions have occurred. An explosive eruption occurred in November 2002 and ejected ash and altered rocks. The altered rocks show that an advanced argillic alteration took place in the hydrothermal system by interaction between acid fluids and rocks. Four zones of alteration have been defined and are limited in extension and shape along faults or across permeable structures at different levels beneath the active crater of the volcano. 相似文献
Phosphorus (P) is an essential nutrient required for plant growth and at the same time a costly pollutant, which can cause eutrophication of water bodies. Modern agriculture relies heavily on mineral fertilisers, which contain phosphorus derived from phosphate rock, because, without regular applications, crop yields would be limited. Since phosphate rock is a non-renewable resource, there are growing concerns regarding future phosphorus scarcity and the sustainability of modern agriculture. For many farmers, animal manure was once a means of maintaining soil fertility, but now it presents a major operational problem. This study evaluated the possibility of recycling phosphorus on a national and regional scale in Italy, using major sources of manure and wastewater. These results were successively compared with an estimate of the agricultural demand for phosphorus. Considering the quantity of phosphorus fertilizer that was applied to the soil–plant system, for the years 2001–2010, the annual phosphorus requirement of Italian crops was about 101,000 t of P. Therefore, the phosphorus source comprising animal manure and civil/industrial waste (117,500 t of P and 40,000 t of P, respectively) could potentially satisfy the average annual agronomic phosphorus demand. Regarding the geographical distribution of phosphorus supply and demand on a regional scale, areas with a large deficit of phosphorus included Calabria, Puglia and Marche. However, when only livestock waste was considered, Sicily, Umbria and Friuli could also be considered to be regions experiencing a phosphorus deficit.
The Late Pleistocene/Holocene Tiber delta succession represents the most recent and one of the best preserved, high‐frequency/low‐rank depositional sequences developed along the Latium continental margin of the Italian peninsula. Several previous studies have established a robust data set from which it has been possible to describe the stratigraphic architecture of the entire Tiber depositional sequence from the landward to seaward sectors and over a distance of 60 km. The Tiber depositional sequence shows many characteristics found in other Late Pleistocene to Holocene deltaic and coastal successions of the Mediterranean area. The stratigraphic architecture of the Tiber depositional sequence is controlled mainly by glacioeustasy, although factors such as tectonic uplift, volcanism and subsidence, exert an influence at a local scale. The resulting depositional model allowed discussion of some important points such as: (1) the genesis of the Tiber mixed bedrock‐alluvial valley, extending from the coastal plain to the innermost portion of the shelf, recording (i) multiple episodes of incision during relative sea‐level fall, and (ii) a downstream increase of depth and width of the valley during the base‐level fall and the subsequent base‐level rise; (2) the different physical expression of the Tiber depositional sequence boundary from landward to seaward, and its diachronous and composite character; (3) the maximum depth reached by the Tiber early lowstand delta at the end of the sea‐level fall is estimated at ca 90 m below the present sea‐level and not at 120 m as suggested by previous works; (4) the backward position of the Tiber late lowstand delta relative to the deposit of early lowstand; (5) the change of the channel pattern and of the stacking pattern of fluvial deposits within the Lowstand Systems Tract, Transgressive Systems Tract and Highstand Systems Tract. All of these features indicate that the Late Pleistocene/Holocene Tiber delta succession, even if deposited in a short period of time from a geological point of view, represents the result of the close interaction among many autogenic and allogenic factors. However, global eustatic variations and sediment supply under the control of climatic changes can be considered the main factors responsible for the stratigraphic architecture of this sedimentary succession, which has been heavily modified by human activity only in the last 3000 years. 相似文献