| 32921. |
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| 32922. |
- Zou, Zhongquan, et al.
(författare)
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Finite element analysis of small span reinforced concrete trough railway bridge
- 2009
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Ingår i: Key Engineering Materials. - 1013-9826 .- 1662-9795. ; 400-402, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- The static behavior of a reinforced concrete trough railway bridge is analyzed by finite element method. The influences of load distribution fashion, supporting width of the bearings and the additional support beneath the girder are investigated; and the spatial effect of the stress distribution is studied as well. To confirm the analysis accuracy, the results are calibrated with the field load test results. It is found that the influence of load distribution fashion is minor and negligible, while those of supporting width and additional support are not negligible; and the spatial effect is significant.
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| 32923. |
- Zounemat-Kermani, Mohammad, et al.
(författare)
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Towards a comprehensive assessment of statistical versus soft computing models in hydrology : Application to monthly pan evaporation prediction
- 2021
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Ingår i: Water. - : MDPI AG. - 2073-4441. ; 13:17
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Tidskriftsartikel (refereegranskat)abstract
- This paper evaluates six soft computational models along with three statistical data-driven models for the prediction of pan evaporation (EP). Accordingly, improved kriging—as a novel statistical model—is proposed for accurate predictions of EP for two meteorological stations in Turkey. In the standard kriging model, the input data nonlinearity effects are increased by using a nonlinear map and transferring input data from a polynomial to an exponential basic function. The accuracy, precision, and over/under prediction tendencies of the response surface method, kriging, improved kriging, multilayer perceptron neural network using the Levenberg–Marquardt (MLP-LM) as well as a conjugate gradient (MLP-CG), radial basis function neural network (RBFNN), multivariate adaptive regression spline (MARS), M5Tree and support vector regression (SVR) were compared. Overall, all the applied models were highly capable of predicting monthly EP in both stations with a mean absolute error (MAE) < 0.77 mm and a Willmott index (d) > 0.95. Considering periodicity as an input parameter, the MLP-LM provided better results than the other methods among the soft computing models (MAE = 0.492 mm and d = 0.981). However, the improved kriging method surpassed all the other models based on the statistical measures (MAE = 0.471 mm and d = 0.983). Finally, the outcomes of the Mann–Whitney test indicated that the applied soft computational models do not have significant superiority over the statistical ones (p-value > 0.65 at α = 0.01 and α = 0.05).
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| 32924. |
- Zuada Coelho, Bruno, et al.
(författare)
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The impact of soil variability on uncertainty in predictions of induced vibrations
- 2023
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Ingår i: Soil Dynamics and Earthquake Engineering. - : Elsevier BV. - 0267-7261. ; 169
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Tidskriftsartikel (refereegranskat)abstract
- Soil is by nature a variable, non-homogeneous material, which has implications for engineering problems involving wave propagation. This paper investigates the impact of the spatial heterogeneity of the stiffness of the soil on the three-dimensional wave propagation. A dynamic Random Finite Element Model is presented in which the soil variability is modelled by means of random fields, applied to the Young's modulus of the soil, following a Monte-Carlo approach. The results show the importance of accounting for soil variability when making predictions on the maximum vibration level. Deterministic analysis is demonstrated to be insufficient when quantifying the maximum vibration level, because no information on the expected variability of the maximum vibration level is obtained. Furthermore, the scale of fluctuation and anisotropy of the random field strongly impact the estimation of the maximum vibration level, and the time of occurrence.
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| 32925. |
- Zuada Coelho, Bruno, et al.
(författare)
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Viscoplastic cyclic degradation model for soft natural soils
- 2021
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Ingår i: Computers and Geotechnics. - : Elsevier BV. - 0266-352X .- 1873-7633. ; 135
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic loading affects the long-term response of geostructures build on natural soils. Soft soils are particularly susceptible to the development of large deformations, induced by the repetitive nature of loading. A new viscoplastic cyclic accumulation model is presented, which is an hierarchical extension of the Creep-SClay1S model, to model the long-term permanent deformation resulting from undrained cyclic loading of natural soft clays. The cyclic cumulative strains are incorporated by means of an additional viscoplastic multiplier. This cyclic viscoplastic multiplier adds four additional model parameters that are derived from undrained cyclic triaxial tests. The model is calibrated using experimental data from undrained cyclic triaxial tests performed on high quality block samples of natural Onsøy clay, at different average shear stresses, shear stress amplitudes and loading periods. The accuracy of the proposed model is demonstrated by comparing the element level simulations with the experimental data. The applicability of the proposed model is further illustrated with a boundary value problem, where an embankment submitted to cyclic loading is simulated. The use of the new model enables the simulation of the response of cyclic loaded foundations on soft soils, where the serviceability limit state over a long period of time is governing the design.
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| 32926. |
- Zubaidi, Salah L., et al.
(författare)
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Assessing the Benefits of Nature-Inspired Algorithms for the Parameterization of ANN in the Prediction of Water Demand
- 2023
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Ingår i: Journal of water resources planning and management. - : American Society of Civil Engineers (ASCE). - 0733-9496 .- 1943-5452. ; 149:1
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Tidskriftsartikel (refereegranskat)abstract
- Accurate forecasting techniques for a stochastic pattern of water demand are essential for any city that faces high variability in climate factors and a shortage of water resources. This study was the first research to assess the impact of climatic factors on urban water demand in Iraq, which is one of the hottest countries in the world. We developed a novel forecasting methodology that includes data preprocessing and an artificial neural network (ANN) model, which we integrated with a recent nature-inspired metaheuristic algorithm [marine predators algorithm (MPA)]. The MPA-ANN algorithm was compared with four nature-inspired metaheuristic algorithms. Nine climatic factors were examined with different scenarios to simulate the monthly stochastic urban water demand over 11 years for Baghdad City, Iraq. The results revealed that (1) precipitation, solar radiation, and dew point temperature are the most relevant factors; (2) the ANN model becomes more accurate when it is used in combination with the MPA; and (3) this methodology can accurately forecast water demand considering the variability in climatic factors. These findings are of considerable significance to water utilities in planning, reviewing, and comparing the availability of freshwater resources and increasing water requests (i.e., adaptation variability of climatic factors).
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| 32927. |
- Zubeck, Hannele, et al.
(författare)
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University of the Arctic's thematic network on Arctic engineering and science
- 2009
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Ingår i: Cold Regions Engineering 2009. - Reston, VA : American Society of Civil Engineers (ASCE). - 9780784410721
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Konferensbidrag (refereegranskat)abstract
- The Thematic Network in Arctic Engineering and Science (TN AES) was created In June 2008 when it was approved by the University of the Arctic's Council. The TN AES focuses on the development of sustainable technologies through engineering and science in the Arctic. The goals of the TN AES are twofold: The main goal is to improve the quality of life and allow the development of natural resources in the arctic through innovations in technologies used in the construction, maintenance and operation of infrastructure, housing, public/private facilities and equipment. The other goal is to assess the impact of climate change on these technologies. This paper introduces briefly the University of the Arctic to the engineering community and then describes current and planned network activities, such as joint education programs.
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| 32928. |
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| 32929. |
- Zubrowska-Sudol, Monika, et al.
(författare)
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Evaluation of deammonification process performance at different aeration strategies
- 2011
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Ingår i: Water Science and Technology. - : IWA Publishing. - 0273-1223 .- 1996-9732. ; 63:6, s. 1168-1176
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Tidskriftsartikel (refereegranskat)abstract
- In a deammonification process applied in the moving bed biofilm reactor (MBBR) oxygen is a crucial parameter for the process performance and efficiency. The objective of this study was to investigate different aeration strategies, characterised by the ratio between non-aerated and aerated phase times (R) and dissolved oxygen concentrations (DO). The series of batch tests were conducted with variable DO concentrations (2, 3, 4 mg L-1) and R values (0-continuous aeration; 1/3, 1, 3-intermittent aeration) but with the same initial ammonium concentration, volume of the moving bed and temperature. It was found that the impact of DO on deammonification was dependent on the R value. At R=0 and R=1/3, an increase of DO caused a significant increase in nitrogen removal rate, whereas for R=1 and R=3 similar rates of the process were observed irrespectively of the DO. The highest nitrogen removal rate of 3.33 g N m(-2) d(-1) (efficiency equal to 69.5%) was obtained at R=1/3 and DO=4 mg L-1. Significantly lower nitrogen removal rates (1.17-1.58 g N m(-2) d(-1)) were observed at R=1 and R=3 for each examined DO. It was a consequence reduced aerated phase duration times and lesser amounts of residual nitrite in non-aerated phases as compared to R 1/3.
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| 32930. |
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