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Endurance time analysis of skewed slab-on-girder bridges: the significance of the excitation angle
, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2276-2285 ; 10263098 (ISSN) ; Ghaffari, E ; Haghani Baei, A ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
In this paper, the influence of the excitation angle on the Endurance Time (TCT) analysis of skewed slab-on-girdcr bridges is studied. The excitation of the structure due to the critical angle produces maximum seismic responses that are sometimes significantly higher than the average. The modeled bridges are of slab-on-girder type that are typically used as highway bridges. The bridge models have skew angles of 0, 15, 30, 45, and CO degrees. The ET excitations exerted on structures cover a broad range of hazard levels. The results provide some insight with regard to choosing multiple excitation angles so as to balance computational costs and retain acceptable accuracy for practical design...
A practical approach to networked control design for robust H∞ performance in the presence of uncertainties in both communication and system
, Article Applied Mathematics and Computation ; Volume 381 , 2020 ; Tavassoli, B ; Farhadi, A ; Sharif University of Technology
Elsevier Inc
2020
Abstract
This work presents results on the development of robust H∞ control strategy for Networked Control Systems (NCSs) by involving uncertainties in both communication and controlled plant subsystems. The network-induced delays in both communication links (to and from the controller) are assumed to behave as Markov chains. An analytical approach is presented to calculate the transition probabilities of the Markovian network-induced delays. By employing the augmentation method, the resultant system is converted into a delay-free uncertain singular Markovian jump system with bounded transition probabilities. New conditions are established to assure that the uncertain NCS satisfies an H∞ performance...
An intelligent search technique for solving train scheduling problems: Simulated annealing and constraint satisfaction
, Article Scientia Iranica ; Volume 14, Issue 5 , 2007 , Pages 442-449 ; 10263098 (ISSN) ; Sharif University of Technology
Sharif University of Technology
2007
Abstract
This paper presents a hybrid scheduling technique for generating the predictive schedules of passenger trains. The algorithm, which represents a combination of simulated annealing and a constraint-based heuristic, has been designed using an object-oriented methodology and is suitable for a primarily single-track railway with some double-track sections. The search process gets started from a good initial solution created by the scheduling heuristic and continues, according to the simulated annealing search control strategy. The heuristic is also used in the neighborhood exploration process. This hybrid approach solves the problem in a short span of time. Simulation experiments, with the real...
Numerical modeling of interaction between flexible retaining wall and saturated clayey soil in undrained and drained conditions
, Article 4th International Conference on Soft Soil Engineering - Soft Soil Engineering, Vancouver, BC, 4 October 2006 through 6 October 2006 ; 2007 , Pages 493-498 ; 0415422809 (ISBN); 9780415422802 (ISBN) ; Pak, A ; Sharif University of Technology
2007
Abstract
In this article, behavior of cantilever retaining walls with various flexibilities, which retain saturated cohesive soil behind, is studied using numerical modeling. Generally, pattern of lateral earth pressure behind retaining walls is complex and this complexity becomes greater for clayey soils. In this investigation, effects of different wall bending stiffnesses, and backfill drainage conditions on the failure height and on the lateral earth pressure are investigated using finite elements. Comparison between the obtained results from numerical simulation and those based on empirical or conventional design methods indicate that soil-structure interaction and c drainage conditions play...
A comprehensive FE study for design of anchored wall systems for deep excavations
, Article Tunnelling and Underground Space Technology ; Volume 122 , 2022 ; 08867798 (ISSN) ; Pak, A ; Yousefi, M ; Aghakhani, N ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Anchored wall system is one of the common methods used for deep excavation stabilization adjacent to sensitive structures in urban areas. A key aspect of the stability analysis of deep excavations is the amount of deformations occurring on the facing wall and the adjacent structures. In this research, a large number of parametric studies considering all aspects of soil-structure interaction is carried out for different excavation geometries to find the optimal design, and the outcome is shown in the form of design tables and charts. Also, by a GA-PSO algorithm and using the large database obtained from the numerical simulations, a simple equation is developed that can predict the deflections...
Optimal tuning of linear controllers for power electronics/power systems applications
, Article Electric Power Systems Research ; Volume 81, Issue 12 , 2011 , Pages 2188-2197 ; 03787796 (ISSN) ; Edrington, C. S ; Mokhtari, H ; Sharif University of Technology
2011
Abstract
This paper presents a new method for tuning various linear controllers such as Proportional-Integral (PI), Proportional-Integral-Derivative (PID) and Proportional-Resonant (PR) structures which are frequently used in power electronics and power system applications. The linear controllers maintain a general structure defined by the Internal Model Principle (IMP) of control theory. The proposed method in this paper is twofold. The first perspective uses the well-known concept of the Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. The Q matrix of the LQR design is then finely adjusted in order to assure the desired transient response for the system. The second...
A GIS-google earth based approach to estimating the flood damage function in large river basins
, Article World Environmental and Water Resources Congress 2011: Bearing Knowledge for Sustainability - Proceedings of the 2011 World Environmental and Water Resources Congress, 22 May 2011 through 26 May 2011 ; May , 2011 , Pages 3811-3821 ; 9780784411735 (ISBN) ; Dashti, M ; Alamdari, N ; Salavitabar, A ; Sharif University of Technology
2011
Abstract
Flood as a natural disaster causes heavy human and economic losses and social unrests in most areas of the world. As flood control cost and flood damage compensation is a heavy burden over countries' budget, traditional flood design methods are being replaced by more reliable risk-based methods employing comprehensive risk analysis. In this respect, flood damage estimation is an important step in flood control systems design and analysis. In large river basins with complex reservoir systems and various land uses, flood damage estimation is complex, data-intensive, time demanding, and uncertain task requiring an intensive hydrologic and hydraulic analysis. In this study a simple approach is...
Application of ozone treatment and pinch technology in cooling water systems design for water and energy conservation
, Article International Journal of Energy Research ; Volume 34, Issue 6 , 2010 , Pages 494-506 ; 0363907X (ISSN) ; Gharaie, M ; Parand, R ; Panjeshahi, E ; Sharif University of Technology
2010
Abstract
Re-circulating cooling water systems offer the means to remove heat from a wide variety of industrial processes that generate excess heat. Such systems consist of a cooling tower and a heat-exchanger network that conventionally has a parallel configuration. However, reuse of water between different cooling duties allows cooling water networks to be designed in a series arrangement. This results in performance improvement and increased cooling tower capacity. In addition, by the integration of ozone treatment into the cooling tower, the cycle of concentration can be increased. The ozone treatment also dramatically reduces the blow-down that, in turn, is environmentally constructive. In this...
Design and comparison of quasi continuous sliding mode control with feedback linearization for a large scale wind turbine with wind speed estimation
, Article Renewable Energy ; Volume 127 , 2018 , Pages 495-508 ; 09601481 (ISSN) ; Moradi, H ; Sharif University of Technology
Abstract
In this paper, dynamic modelling and control of WindPACT 1.5 MW wind turbine in Region 2 for extracting the maximum energy from wind is investigated (where the wind velocity is greater than ‘cut in’ and below ‘rated’ wind speeds). In this region, the generator torque must regulate the rotor speed in its optimal value while the blade pitch angle is considered constant in its optimal value. To achieve a more accurate model, wind turbine is modeled as an electromechanical system with two masses dynamics. A new method based on adaptive neuro fuzzy inference system (ANFIS) is considered for wind speed estimation; where rotor speed, output power and pitch angle are inputs of such system and...
Directional dependence of extreme metocean conditions for analysis and design of marine structures
, Article Applied Ocean Research ; Volume 100 , 2020 ; Imani, H ; Karimirad, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Marine structures are typically sensitive to the direction of wind and waves, especially in extreme metocean conditions. The extreme metocean conditions and their associated predicted directions are not easily reachable from traditional design methodologies. In this research, the most probable combinations of different extreme metocean conditions along with their associated direction are predicted for the HyWind Scotland wind farm, Scotland. To achieve this, the Hierarchical Bayesian Modeling approach is applied to define the Joint Probability Distribution Function (JPDF) of four combinations of metocean parameters, including wave direction, wind direction and wind-wave misalignment. The...