JOURNAL OF COMPUTATIONAL METHODS IN ENGINEERING (ESTEGHLAL)
Year:2009 | Volume:28 | Issue:2|Papers Count:6

Ureter reflux is one of the prevalent factors causing pyelonefrit and sistit syndromes. Dilatation of ureter, renal pelves and calyx are normally detectable with reflux. An axisymmetric model using the fluid-structure interactions (FSI) method is introduced and solved to perform the ureter flow and stress analysis. The Navier-Stokes equations were solved for the fluid and a linear elastic model wass used for ureter. Our results indicate that the fluid shear stresses on the wall and the pressure gradient magnitude along the ureter wall as well as the symmetry line are high around the throat of motion contracted wall which decreases while peristalsis propagates toward the bladder. Reflux is more probable to occur at the startup of the wall peristaltic motion.

The Tuned Liquid Damper (TLD) is nowadays increasingly being used as an economical and effective passive vibration absorber. This research focuses on modeling tall buildings equipped with Tuned Liquid Dampers (TLDs) subjected to strong ground motions. Strong excitation can lead to the wave breaking phenomenon and make turbulence in shallow rectangular tanks which could, in turn, contribute to additional damping due to TLD’s. Wire screens placed inside the liquid tank can play an important role in reducing the structural response due to increased inherent damping of the structure. In this study, a simple method is introduced for modeling this type of Tuned Liquid Damper by using Equivalent Amplitude Dependent Tuned Mass Damper. The method is based on equalizing dissipated energies in both devices. Equations of motion for shear-type buildings equipped with nonlinear Amplitude Dependent Tuned Mass Dampers are developed. A complex modal analysis procedure is used to solve the governing equations. Coupling of TMD properties and structural response is solved with iteration on structural response and updating TMD’s properties. Performing a set of parametric studies on a practical 10-storey building equipped with TLDs subjected to different ground excitations showed that the TLD significantly reduced the seismic response (displacement and base shear) of the structures when the Tuned Liquid Damper was tuned to the natural frequency of the structure considering the hardening behavior of TLD.

In traditional methods of Performance-Based Design (PBD), the structure is usually designed to satisfy the performance criteria in an iterative manner. The objective of this research is to define and formulate the PBD problem as an optimization model and to develop a computer-based method for finding Optimal Performance-Based Design (OPBD) of Reinforced Concrete (RC) Frames. First, a definition of the optimization model is provided and explicit relations are then derived for the objective function and constraints of the problem utilizing a nonlinear sensitivity analysis with respect to design variables and the convex approximation method. To solve the optimization problem thus obtained, the dual method is utilized. Some numerical examples are provided to illustrate the capabilities of the proposed method.

Placing column lap splice at possible nonlinear deformation locations may adversely affect the structure’s response to strong ground motions. Localization of damage in the splice zone may change the structural response and prevent the load redistribution and development of a uniform pattern of nonlinear excursions among various members. Using laboratory.experiments, this study aims to present a model that can be used for predicting the behavior of lap spliced columns. The model is able to include the effects of longitudinal bar arrangement, bar yield stress, and the amount and spacing of transverse bars. It is shown that there is a good correlation between model and experimental results. Also, it is shown that the method of FEMA 356 to evaluate the effect of lap splice on column behavior is conservative. Finally, the results of nonlinear static and dynamic analyses of an ordinary moment resisting frame are presented. This case study indicates large damage localization due to deterioration of lap splice in column sections with nonlinear deformation.

Occurrence of special events such as overloads, load shedding, interruptions and faults, and shortcomings of operators in an error free manual recording of data are the main sources of anomalous load profiles imposing errors in Artificial Neural Network based Short-Term Load Forecasting (ANNSTLF) systems. In this paper, an ANNSTLF system is properly designed for the real power system of Isfahan Province and used to compare the impacts of filtering out the anomalous data by expert experience, statistical analysis, and a new algorithm based on the Principal Component Analysis (PCA). The results show that filtering out anomalous load-profiles before ANNSTLF can reduce the forecasting error efficiently. It is also shown that the proposed PCA filtering method is simpler in application and faster in response, yielding accurate forecasting results.

In this study, the integral method has been employed in order to calculate the non-uniform residual stresses in various composite laminates. The integral method is a well established technique for isotropic materials. In this research, the method is extended and examined for composite materials. In the integral method, the residual stresses in each lamina are determined by consecutive drilling at the center of the rosette which is mounted on the surface of the laminated composites and recording the strains in each layer afterwards. The calibration coefficients for each stage of drilling are determined by simulating the incremental hole drilling process. The calibration coefficients of the integral method separate the residual strains of each layer from the strains measured in each stage of the drilling and, hence, increase the accuracy of calculating the residual stresses in each layer. In this study, samples of symmetric and un-symmetric cross ply and quasi isotropic laminated composite are examined. The residual stresses in each layer of composite samples are determined through measuring the released strains in consecutive steps of the drilling. The experimental measurements are then compared with the predictions of the classical laminate theory. The agreements between the two results validate the integral method for calculating the residual stresses in laminated composite materials.