rss_2.0Modelling in civil and environmental engineering FeedSciendo RSS Feed for Modelling in civil and environmental engineering in civil and environmental engineering 's Cover Platform for the Analysis and Design of Tall Buildings for Wind Loads<abstract><title style='display:none'>Abstract</title><p>The Romanian, as well as other wind design codes for building structures, provides with limited degree of accuracy, the aerodynamic loads distribution on buildings up to 200 meters tall in an equivalent static approach (ESWL). For tall wind-sensitive building structures, especially for those with irregular shapes, most of the codes or standards recommend for design to use pressure data recorded in the wind tunnel. The ESWL approach is however used as reference estimation and structural first phase design. Advances on experimental and computational capabilities, led in the past decade to a significant development of time-domain analysis framework, both for seismic and wind loads. While the major outcome for earthquake engineering practitioners is to select appropriate design input ground motions at a particular site, the wind engineering practitioners are facing numerical difficulties to handle large wind loading durations, especially dealing with nonlinear-induced effects.</p><p>The paper presents a real-time integrated framework for the analysis and design of tall buildings to wind loads, based on the time-domain analysis tool, as a prerequisite for higher level modules as vulnerability, risk and loss estimation, and optimization analyses.</p></abstract>ARTICLE2020-02-27T00:00:00.000+00:00Modelling the Unsteady Flow of Water into a Partly Saturated Soil<abstract><title style='display:none'>Abstract</title><p>Flows in unsaturated medium are frequent in the field of civil engineering and more particularly in geotechnics. The study undertaken here tries to solve the unsaturated transient flow equation in porous media using the finite element method. Numerical solution of a finite element discretization is used along with an implicit integration scheme of the time stepping. A functional one that makes it possible to find the distribution of the hydraulic load has been proposed and a calculation program has been developed. The results obtained by this program called TFAP (Transient Flow Analysis Program) are compared to other previous work in the subject. The authors show the importance of this study through two real examples. Liakopoulos conducted several experiments on the water drainage through a vertical column filled with Del Monte sand. One of these experiments was chosen to perform a simulation by the model. The results of the calculation are compared with the experimental data as well.</p></abstract>ARTICLE2020-02-27T00:00:00.000+00:00Numerical Study on Temporal Domain Discretizing for Hydrogeological Modeling Practices<abstract><title style='display:none'>Abstract</title><p>One of the key operations in the construction of hydrogeological models is the transformation of continuous physical systems into discrete models while conserving the aimed model performance level and optimizing the available resources. Such operation is called discretization, and it has to be applied to both spatial and temporal domains in hydrogeology. The present paper deals with the temporal domain discretization. A literature review is given first, and then a parametric study (using 1D flow modeling) is conducted to assess the effects induced by boundary conditions (specified head or specified recharge rate), data temporal resolution and model simulation time step on hydrogeological flow model performances. It was found that the effect induced by the dynamic comportment of a recharge rate boundary condition type is more important than that due to a specified head. For the recharge rate, the time step must be smaller or equal to the data resolution when using Modflow. As for a specified head boundary condition type, it was recommended to take a time step satisfying Δt<sub/>∞1/(K × Δh).</p></abstract>ARTICLE2013-04-12T00:00:00.000+00:00Structural analisys of concrete pre-stressed reservoirs for sludge fermentation – water waste treatment plant bucharest – glina. numerical fem assessment of the structural response for static in-duty loads<abstract><title style='display:none'>Abstract</title><p>The paper refers to a structural finite element analysis on the reservoirs for sludge fermentation subjected to static in-duty loads, at Glina Water Waste Treatment Plant. The purpose was to assess the stress and deformation states in subsequent erection and service conditions, to verify the design provisions and to emphasize the sensitivities, for a structure which was designed in the ‘80s based on analytical procedures. The results obtained on the numerical models highlight the importance of the soil-structure interaction, in peculiar the one influenced by the soil mass deformability, on the overall structural response. Based on the calculated stresses, all structural components were verified according to the actual design codes at the ultimate limit state and the service limit state (water tightness/crack emergence).</p></abstract>ARTICLE2013-04-12T00:00:00.000+00:00Bayes Signification Tests in Linear Regression and Economic Applications<abstract><title style='display:none'>Abstract</title><p>In this paper we will use the statistical inference, in particular the Bayes tests for the signification of the parameters of linear regression. We will consider the cases of known variance, and unknown variance respectively. Because we replace the Student tests by the Z tests in practice if the involved number of degrees of freedom is at least 30 , we can replace the case of unknown variance with that of known variance in our paper, if the above number of degrees of freedom is at least 30 . Because in economics we generally know the signs of the involved parameters, in practice the one-sided parametric tests are used. However, in this paper we will refer also to the two-sided Bayes test.</p></abstract>ARTICLE2013-04-12T00:00:00.000+00:00Comparative Study of Codes for Seismic Design of Structures<abstract><title style='display:none'>Abstract</title><p>This paper presents a comparative evaluation among some international, European and American, seismic design standards. The study considers the criteria for the analysis of conventional (residential and commercial) buildings. The study is focused on some critical topics: definition of the recurrence periods for establishing the seismic input; definition of the seismic zonation and shape of the design response spectra; consideration of local soil conditions; definition of the seismic force-resisting systems and respective response modification coefficients; definition of the allowable procedures for the seismic analysis. A model for a standard reinforced concrete building (“Model Building”) has been developed to permit the comparison among codes. This building has been modelled with two different computer programs, SAP2000 and SOFiSTiK and subjected to seismic input according to the several seismic codes. The obtained results compared are leading to some important conclusions.</p></abstract>ARTICLE2013-04-12T00:00:00.000+00:00NUMERICAL RESULTS FOR LOTKA-VOLTERRA MODEL USING APPROXIMATE INERTIAL MANIFOLDS<p>A numerical study on the classical Lotka-Volterra model is performed, using approximate inertial manifolds. An analytical study consisting in the inertial form of the system is made. The construction of the approximate inertial manifolds is based on the identification of the absorbing domains using the graphical representations of the phase portraits. The hypotheses of the Jolly-Rosa-Temam algorithm are verified for certain values of parameters and the approximate inertial manifolds are constructed. Errors of approximation are computed.</p>ARTICLE2013-12-31T00:00:00.000+00:00MODELLING METHODS FOR SOIL-STRUCTURE INTERACTION APPLIED IN WIND TURBINE FOUNDATION DESIGN<p>The article presents a case study on soil-structure interaction modelling for Wind turbines. After a brief presentation on the history of wind turbines and their potential in Romania, the authors take on the task of modelling the soil-structure interaction for the raft and piles. Three models are chosen: in the first model the piles are fixed at foundation depth; in the second, elastic supports are modelled on the raft and the piles and in the third model both elastic supports and fixed supports are modelled. Several comparisons are made between the three cases referring to displacements, efforts and necessary reinforcement. Based on these comparisons, the most important conclusion drawn is that the modelling of the soil-structure interaction has an important effect on the final reinforcement of the raft and the piles, considering that the difference between the models reaches almost 18%, which in the case of really large foundations can draw the line between economic and non-economic design.</p>ARTICLE2013-12-31T00:00:00.000+00:00STUDY ON RELATION BETWEEN INELASTIC AND ELASTIC DISPLACEMENT FOR VRANCEA EARTHQUAKES<p>At present, Romanian code for seismic design P100 is in a process of assimilation of the requirements from the equivalent European code, EN-1998-1. However, the unique characteristics of the Vrancea earthquakes require additional adjustment for some relations. One of these relations regards the simplified calculation of inelastic displacements and represents the main objective of this article. The paper uses dynamic nonlinear analysis performed on single degree of freedom systems as the main investigation tool. For all the analyses, two hysteretic models are used: Takeda and kinematic hardening. In the beginning, the paper presents the influence of overstrength on inelastic displacements for several behaviour factors. Next, the overstrength-period diagram is proposed based on a case study. Finally, the spectrum of c, the ratio between inelastic and elastic displacement is calculated. The main result of the study is the simplified equations proposed for c factor, relations that can be successfully used in current design.</p>ARTICLE2013-12-31T00:00:00.000+00:00STRUCTURAL ANALISYS OF CONCRETE PRE-STRESSED RESERVOIRS FOR SLUDGE FERMENTATION – WASTE WATER TREATMENT PLANT BUCHAREST – GLINA.<p>The paper refers to a structural finite element analysis on the reservoirs for sludge fermentation at Glina Waste Water Treatment Plant. The purpose was to assess the dynamic response of the structure, the stress and deformation states due to the design earthquake. A linearelastic analysis was performed, according to the Romanian actual codes, in order to verify the design provisions and to emphasize the sensitivities, for a structure which was designed by analytical procedures. The results obtained on the numerical models highlight the importance of the soil-structure interaction, in peculiar the one influenced by the soil mass deformability, on the overall structural response. Based on the results of the analysis, an in-situ measurement campaign for structural dynamic characteristics was initiated, taking advantage of the ongoing repair works with subsequent exhaustion and re-filling of reservoir No. 4.</p>ARTICLE2013-12-31T00:00:00.000+00:00Urban Ozone Concentration Forecasting with Artificial Neural Network in Corsica<p>Atmospheric pollutants concentration forecasting is an important issue in air quality monitoring. Qualitair Corse, the organization responsible for monitoring air quality in Corsica (France), needs to develop a short-term prediction model to lead its mission of information towards the public. Various deterministic models exist for local forecasting, but need important computing resources, a good knowledge of atmospheric processes and can be inaccurate because of local climatical or geographical particularities, as observed in Corsica, a mountainous island located in the Mediterranean Sea. As a result, we focus in this study on statistical models, and particularly Artificial Neural Networks (ANNs) that have shown good results in the prediction of ozone concentration one hour ahead with data measured locally. The purpose of this study is to build a predictor realizing predictions of ozone 24 hours ahead in Corsica in order to be able to anticipate pollution peaks formation and to take appropriate preventive measures. Specific meteorological conditions are known to lead to particular pollution event in Corsica (e.g. Saharan dust events). Therefore, an ANN model will be used with pollutant and meteorological data for operational forecasting. Index of agreement of this model was calculated with a one year test dataset and reached 0.88.</p>ARTICLE2014-04-12T00:00:00.000+00:00Seismic Design Of Low-Rise Office Buildings According To Romanian Seismic Codes. Case Study.<p>The paper presents a study case and highlights the changes made by the new, in force, seismic Code P100-1/2013 in comparison with the former P100-1/2006, concerning the reinforced concrete frame structural systems design. Different seismic designed RC frames systems, compatible with modern office requirements, were studied. The influence of the earthquake codes provisions on design of regular buildings, having openings fitted for open spaces, with a story height of 3.50m, was assessed. The benefits of tubular structures, with rigid frames made of closely spaced columns on the building perimeter, were analyzed as well. The results of the study case are presented emphasizing the consequences of the application of the new seismic Code on the computation of the reinforced concrete frame structures.</p>ARTICLE2015-07-10T00:00:00.000+00:00The Experimental Analysis Of An Innovative Yielding Metallic Damper<p>One of the most destructive natural phenomena is the earthquake. These events destroy lives, goods and disrupt human activities. For this reason the anti-seismic protection of buildings is a very important and of interest subject in Civil Engineering. In the case of structures with a low seismic energy dissipation capacity (for example steel frame structures with Slimdek composite floors), this problem becomes more complicated due to the requirement of dampers. In this paper an experimental study is presented regarding an innovative yielding metallic energy dissipation device, proposed by the author. An experiment is carried out on a shake table. By studying the results from the experiments and from the previous carried out numerical analysis we can conclude that this device provides a high anti-seismic protection for this type of structures.</p>ARTICLE2015-07-10T00:00:00.000+00:00Thermal Comfort Analyses in Naturally Ventilated Buildings<p>Global current requirement is to increase thermal comfort in residential and non residential buildings. A field survey was accomplished in a naturally ventilated university classroom in Bucharest, Romania, in winter and spring. Comfort parameters were measured and comfort questionnaires were distributed to the students. Questions were related to thermal sensation of the occupants. This paper compares the experimental results with the occupant’s response. It analyzes the variation of Predicted Mean Vote (PMV) and Predicted Percent of Dissatisfied (PPD) with temperature. It is made a comparison between PMV and thermal sensation vote. The results show PMV values different from Thermal Sensation Vote (TSV) values which means there is a poor approximation of indoor comfort. In conclusion the comfort parameters should be reviewed and should be proposed other evaluation methods. Possible explanations are discussed in relation with thermal regime of the buildings.</p>ARTICLE2014-12-30T00:00:00.000+00:00Update of the P100-1 Concrete Provisions<p>In an effort to improve the harmonization of the Romanian design codes with the Eurocodes, the revision of the Seismic Design Code, P100-1, started in April 2010 and ended in September 2013. The main issues addressed during the revision process are presented in this paper. They include re-outlining the fundamental requirements for seismic design, revision of the seismic action, improvement of the specific provisions for the design of reinforced concrete, steel, composite, wood and masonry structures and non-structural components. This paper focuses on the specific provisions for reinforced concrete structures but general information about the fundamental requirements and the seismic action are presented as well.</p>ARTICLE2014-12-30T00:00:00.000+00:00Benefit of Wind Tunnels with Large Test Sections for Wind Engineering Applications<p>Atmospheric Boundary layer wind tunnels (ABLWT) dedicated to building safety and comfort have been operated by CSTB in Nantes since 1971. Because ABLWT only deal with reduced scale models of real structures, the necessity of a larger wind tunnel, the Jules Verne Climatic wind tunnel (CWT), able to reproduce extreme wind loads on real scale structures arose in the years 80. Hence, it became a major European facility operating for improvement of the safety, quality and environmental impact of buildings and civil engineering works as well as products from industrial fields (transportation, energy…) with respect to strong winds and other climatic hazards. Both wind tunnel types, the ABLWT and the CWT are complementary and used for studying the effect of wind on the same structures at two different scales, when the effect of wind scaling is important. During the 2018 year, several modifications were made to the CWT facility. The atmospheric test section of the existing facility was elongated preserving the initial advantages, very large test section (approximately 120 m<sup>2</sup>) with wind velocity performance compatible with many applications (up to 90 km/h). This new test section makes it possible to simulate turbulent wind and driving rain testing. The sand winds capabilities have been maintained in the new design, despite the closed loop configuration, by fitting a filtering. The modifications of the wind tunnel geometry now offer a long test section upstream the turning vanes where a whole set of new tests can be carried out, as windmill field, natural ventilation of urban environments, slender structures (large bridges, pylons, cable transport systems,)</p>ARTICLE2019-08-02T00:00:00.000+00:00On the Use of the Cubic Translation to Model Bimodal Wind Pressures<p>The cubic translation model is a well know tool in wind engineering, which provides a mathematical description of a non-Gaussian pressure as a cubic transformation of a Gaussian process. This simple model is widely used in practice since it offers a direct evaluation of the peak factors as a function of the statistics of the wind pressure data. This transformation is rather versatile but limited to processes which are said to be in the monotonic region. For processes falling outside this domain, this paper describes an alternative which is based on the physics of the wind flow. First, it is shown, with a classical example of a flow involving corner vortices on a flat roof, that the pressure data which does not meet the monotonic criterion is in fact associated with a bimodal distribution. Then, the proposed approach is to decompose this data into the two governing modes (slow background turbulence and fast corner vortices) and apply the usual translation model to each of them.</p>ARTICLE2019-08-02T00:00:00.000+00:00Mathematical Determination of Thermal Load for Fluidised Bed Furnaces Using Sawdust<p> For technical applications, a physical model capable of predicting the particle evolution in the burning process along its trajectory through the furnace is very useful. There are two major demands: all the thermo-dynamic processes that describe the particle burning process must be accounted and the model must be written in such equation terms to allow the intervention for parameter settings and particle definition. The computations were performed for the following parameters: furnace average temperature between 700 and 1200 °C, size of the sawdust particle from 4 to 6 mm and fix carbon ignition between 500 and 900 °C. The values obtained for the characteristic parameters of the burning process ranged from 30 to 60 [kg/(h·m<sup>3</sup>)] for the gravimetrical burning speed W<sub>Gh</sub> and from 150 to 280 [kW/m<sup>3</sup>] for the volumetric thermal load of the furnace Q<sub>V</sub>. The main conclusion was that the calculus results are in good agreement with the experimental data from the pilot installations and the real-case measurements in the sawdust working boiler furnaces or pre-burning chambers. Another very important conclusion is that the process speed variation, when the furnace temperature changes, confirms the thermo-kinetic predictions, namely that the burning process speed decreases when the furnace temperature increases.</p>ARTICLE2014-07-10T00:00:00.000+00:00Water Quality Improvement Using Renewable Energies<p> To reduce the negative effects of eutrophication processes in water bodies it is necessary to improve water quality by ensuring the necessary oxygen concentration. The paper proposes a new innovative solution for the improvement of lake water quality. The premises for the implementation of the experimental floating platform which will aerate the lake waters will be presented. To give a specific view over the oxygen dispersion into the lake, numerical simulations in CFD software will be presented in different cases. </p>ARTICLE2014-07-10T00:00:00.000+00:00The Tuning of the Fuzzy Controllers Used in the Pervasive Systems<p> This paper intends to present the differences appearing between the pervasive systems and other usual systems regarding the tuning of the fuzzy controllers. For the pervasive systems used in the intelligent buildings, the emphasize is on the building’s occupant and the used equipment is to be engineered so that the occupant will be as less perturbed by its presence or settings. For the fuzzy controllers used in non-pervasive systems - although the occupants are not working with physical quantities, but with language described variables, the definition of the inputs’ and outputs’ domain values can be modified only by reprogramming. </p>ARTICLE2014-07-10T00:00:00.000+00:00en-us-1