Considerations on the slip demand of shear connectors in composite steel-concrete beams with solid slabs

The objective of this study is to provide insight into the expected slip demand in composite steel-concrete beams through numerical simulations. A wide parametric analysis is carried out evaluating the partial interaction performance of simply-supported beams designed considering a variety of floors, i.e. span length, slab thickness, shear connection strength, dead load to live load ratio and slab concrete strength. For each of these beams, the slip demand required to achieve the expected design capacity is evaluated. In this process, key parameters influencing the slip requirements are identified. These also include the construction sequence (propped or unpropped) and the shear connection distribution (uniform or non-uniform with different layouts)

Non-linear analysis of two-layer timber beams considering interlayer slip and uplift

A new mathematical model and its finite element formulation for the non-linear analysis of mechanical behaviour of a two-layer timber planar beam is presented. A modified principle of virtual work is employed in formulating the finite element method. The basic unknowns are strains. The following assumptions are adopted in the mathematical model: materials are taken to be non-linear and can differ from layer to layer; interacting shear and normal contact tractions between layers are derived from the non-linear shear contact traction-slip and the non-linear normal contact traction-uplift characteristics of the connectors; the geometrically linear and materially non-linear Bernoulli's beam theory is assumed for each layer. The formulation is found to be accurate, reliable and computationally effective. The suitability of the theory is validated by the comparison of the numerical solution and the experimental results of full-scale laboratory tests on a simply supported beam. An excellent agreement between measured and calculated results is observed for all load levels. The further objective of the paper is the analysis of the effect of different normal contact traction-uplift constitutive relationships on the kinematic and static quantities in a statically determined and undetermined structure. While the shear contact traction-slip constitutive relationship dictates the deformability of the composite beam and has a substantial influence on most of the static and kinematic quantities of the composite beam, a variable normal contact traction-uplift constitutive relationship is in most cases negligible

The role of thermophoretic effect in the formation of soot from liquid fuels

In order to rationalize soot formation in two-phase combustion, the related dynamics can be conveniently studied in simpler systems. In the latest twenty years, experimental activity in drop towers and in the outer space have allowed to investigate the combustion of isolated droplets in microgravity conditions, i.e. spherically symmetric systems where buoyancy effects and slip velocity are absent, yet still containing the major phenomena affecting real combustion (unsteady evolution, convection, gas and soot radiation, heterogeneous properties and so on). In such conditions, it had been speculated [1] that a key role in soot formation is played by thermophoretic effect, because of which solid particles are transported towards the droplet surface, thus increasing their residence times in the fuel-rich area, where soot growth is kinetically favoured. The spherical symmetry also allows to numerically study these systems with a relatively low computational weight. The importance of thermophoresis in the dynamics of soot formation can thus be investigated in a variety of operating conditions (droplet size, pressure, composition, etc.), which is the subject of this work. Starting from a description of the constitutive parts of the isolated-droplet model, the transient dynamics of soot formation in n-heptane droplets is analysed. The impact of the submodel describing thermophoresis is considered in detail, and indications about its possible refinements are provided

Exact slip-buckling analysis of two-layer composite columns

A mathematical model for slip-buckling has been proposed and its analytical solution has been found for the analysis of layered and geometrically perfect composite columns with inter-layer slip between the layers. The analytical study has been carried out to evaluate exact critical forces and to compare them to those in the literature. Particular emphasis has been placed on the influence of interface compliance on decreasing the bifurcation loads. For this purpose, a preliminary parametric study has been performed by which the influence of various material and geometric parameters on buckling forces have been investigated. (C) 2009 Elsevier Ltd. All rights reserved

A multi-century meteo-hydrological analysis for the Adda river basin (Central Alps). Part I: Gridded monthly precipitation (1800–2016) records

The 1800–2016 monthly precipitation record for the upper Adda river basin is presented. It is computed by applying the anomaly method to a quality-checked and homogenized observation database. The reconstruction accuracy and its evolution over the study period is evaluated at both station and grid-cell levels. The anomaly-based interpolation provides rather robust estimates even for the early years of sparse station coverage with basin precipitation reconstruction errors around 10%. The Theil-Sen trend analysis on the basin precipitation series shows significant (Mann-Kendall p value <.05) long-term tendencies of −3.8 ± 1.9% and −9.3 ± 3.8% century−1 for annual and autumn precipitation, respectively, even though the annual trend is not significant by excluding the first decades from the evaluation. As the basin precipitation record is expected to be underestimated due to the rain-gauge snow undercatch, the monthly precipitation fields are subjected to a correction procedure which allows to derive the multiplicative correcting constant to be applied to the basin annual precipitation series. The comparison between 1845 and 2016 yearly corrected precipitation and runoff records highlights current annual water losses of about 400 mm while the annual runoff coefficients exhibit a long-term significant decrease of −6.4 ± 1.0% century−1. This change in the hydrological cycle is mostly to be ascribed to the strong long-term reduction in annual runoff values (−11.8 ± 3.2% century−1) driven by increasing evapotranspiration due to both temperature increase and, likely, land-use changes

A Review of Exposure Assessment Methods in Epidemiological Studies on Incinerators

Incineration is a common technology for waste disposal, and there is public concern for the health impact deriving from incinerators. Poor exposure assessment has been claimed as one of the main causes of inconsistency in the epidemiological literature. We reviewed 41 studies on incinerators published between 1984 and January 2013 and classified them on the basis of exposure assessment approach. Moreover, we performed a simulation study to explore how the different exposure metrics may influence the exposure levels used in epidemiological studies. 19 studies used linear distance as a measure of exposure to incinerators, 11 studies atmospheric dispersion models, and the remaining 11 studies a qualitative variable such as presence/absence of the source. All reviewed studies utilized residence as a proxy for population exposure, although residence location was evaluated with different precision (e.g., municipality, census block, or exact address). Only one study reconstructed temporal variability in exposure. Our simulation study showed a notable degree of exposure misclassification caused by the use of distance compared to dispersion modelling. We suggest that future studies (i) make full use of pollution dispersion models; (ii) localize population on a fine-scale; and (iii) explicitly account for the presence of potential environmental and socioeconomic confounding

Novel coal gasification process: Improvement of syngas yield and reduction of emissions

This article is intended to propose and model an innovative process layout for coal gasification that improves the production of syngas and also reduces the sulfur and CO2emissions. The typical coal gasification process uses Sulfur Recovery Units to convert H2S to sulfur, but these have some disadvantage, e.g low sulfur price, coal charge with low sulfur flow rate, use of Tail Gas Treatment unit. Compared to the Claus process, this solution converts H2S and CO2into syngas (economically appealing), reduces emission of H2S and CO2and allows the use of coal charge with high sulfur flow rate, e.g. 9.5% mol/mol. The novel process takes advantage of a double amine wash, a thermal regenerative furnace and considers the recycle of the acid gases coming from the catalytic reactor to further promote the H2S conversion. In particular, the double amine wash is useful to purify the H2S stream to be sent to the thermal furnace from the syngas and CO2, in order to reduce the reactor inlet flow rate. The regenerative furnace is simulated using a large detailed kinetic scheme to appropriately describe the minor species (among them, pollutants like CS2 and COS). As a result, the recycle appears to substantially reduce the pollutant emissions. In addition, the conversion of the Claus process into the novel process doesn't require any change in the main equipment, just needing for a variation in the layout and the operating conditions

Devolatilization of organo-sulfur compounds in coal gasification

Coal gasification is a thermo-chemical process aiming at the production of high heating value syngas. The coal charges present, typically, a low quantity of sulfur compounds for prevent the formation of a large amount of sulfuric acid (H2S), that is a pollutant and a poison for catalysts, in syngas stream. However, in the world there are a lot of coals that cannot be used for gasification because of their high sulfur content (e.g. Sulcis Italian coal or Inner Mongolia Chinese coal). The interest on these types of coal is increasing due to a novel technology that allows to convert H2S and CO2into syngas (AG2S\u2122). The aim of this work is to propose a predictive kinetic model of the release of sulfur compounds (e.g H2S) from coal. This kinetic scheme is implement into GASDS, a package that includes a gasifier mathematical model, which accurately describes the inter-phase mass and heat transfer. The first complexity relies in the characterization of the coal, in particular the relative amount of the different forms of sulfur components (e.g. inorganic such as pyritic and sulfates, and organic sulfur such as aliphatic, aromatic and thiophenic) and their pyrolysis and devolatilization process. The kinetic model, with the related rate parameters, is validated through comparison with experimental data from the literature and obtained during several experimental campaigns at the Sotacarbo S.p.A. pilot platform. Finally, different operating conditions of gasification are analyzed in order to obtain the best yield in the downstream process, with special reference to the novel Acid Gas to Syngas (AG2STM) process

Uncertainty propagation for flood forecasting in the Alps: different views and impacts from MAP D-PHASE

D-PHASE was a Forecast Demonstration Project of theWorldWeather Research Programme (WWRP) related to the Mesoscale Alpine Programme (MAP). Its goal was to demonstrate the reliability and quality of operational forecasting of orographically influenced (determined) precipitation in the Alps and its consequences on the distribution of run-off characteristics. A special focus was, of course, on heavy-precipitation events. The D-PHASE Operations Period (DOP) ran from June to November 2007, during which an end-to-end forecasting system was operated covering many individual catchments in the Alps, with their water authorities, civil protection organizations or other end users. The forecasting system’s core piece was a Visualization Platform where precipitation and flood warnings from some 30 atmospheric and 7 hydrological models (both deterministic and probabilistic) and corresponding model fields were displayed in uniform and comparable formats. Also, meteograms, nowcasting information and end user communication was made available to all the forecasters, users and end users. D-PHASE information was assessed and used by some 50 different groups ranging from atmospheric forecasters to civil protection authorities or water management bodies. In the present contribution, D-PHASE is briefly presented along with its outstanding scientific results and, in particular, the lessons learnt with respect to uncertainty propagation. A focus is thereby on the transfer of ensemble prediction information into the hydrological community and its use with respect to other aspects of societal impact. Objective verification of forecast quality is contrasted to subjective quality assessments during the project (end user workshops, questionnaires) and some general conclusions concerning forecast demonstration projects are drawn

A CFD model for biomass flame-combustion analysis

The present work addresses the study of the combustion of individual biomass particle surrounded by a gas stream of N2/O2 under the operating conditions encountered in a drop tube reactor. The aim of this analysis is to give a better insight into the chemical and physical processes that occur both at particle and reactor scale where the volatiles, generated by the biomass pyrolysis, burn in a fuel particle enveloped flame. A comprehensive CFD model was developed within the open-source OpenFOAM® framework in order to properly handle the computational mesh and the discretization of the characteristic governing equations. At the reactor scale, the reactive flow was described by the equations for continuous, multicomponent, compressible and thermally-perfect mixtures of gases. At the particle scale, instead, the solid particle was considered as a porous media with isotropic and uniform morphological properties