Sharif Digital Repository

This paper proposes probabilistic damage and collapse models for reinforced concrete poles in electric power distribution networks and investigates the damage and collapse pattern of poles under earthquake excitations. To this end, detailed finite element models of the H-type reinforced concrete poles are developed and verified using past experimental studies as well as the observed damage in previous earthquakes. The models are then subjected to nonlinear static analyses to study the effect of the loading pattern, loading direction, concrete strength, and failure criteria on the capacity and the collapse pattern of the pole. Next, incremental dynamic analysis is carried out to investigate... 

A new procedure is proposed to quantify uncertainties involved in the seismic response of structures including ground motion and modeling variability. The advent of performance-based earthquake engineering (PBEE) and probabilistic seismic risk analysis necessitates consideration of uncertainties in predicting seismic responses. However, the high computational cost of conventional methods restricts their application to only simple numerical models. The present study employs the endurance time (ET) method concept to predict the response distribution which requires much less computational efforts than conventional methods. The proposed procedure for the quantification of record-to-record... 

In this paper, a novel temperature-dependent multi-scale method is developed to investigate the role of temperature on surface effects in the analysis of nano-scale materials. In order to evaluate the temperature effect in the micro-scale (atomic) level, the temperature related Cauchy–Born hypothesis is implemented by employing the Helmholtz free energy, as the energy density of equivalent continua relating to the inter-atomic potential. The multi-scale technique is applied in atomistic level (nano-scale) to exhibit the temperature related characteristics. The first Piola–Kirchhoff stress and tangential stiffness tensor are computed, as the first and second derivatives of the free energy... 

In this work, steady state and dynamic performances of quaternary distillation column sequences designed based on steady state and dynamic cost functions have been investigated. To quantify the dynamic performance, product losses due to disturbances have been considered in the objective function. In addition, variations of operating costs such as utilities have been considered in the objective function. To separate a quaternary mixture into four products, 22 configurations have been used. It has been observed that the feed composition, disturbance frequency and magnitude affect the dynamic behavior strongly. To decrease the optimization computational load, a scheme that provides a suboptimal... 

The present paper studies the impact of dynamic interaction between high-voltage substation equipment on the response and vulnerability of substation equipment. The 3D numerical model is developed for four types of vulnerable equipment in the both unconnected and connected conditions. The bus slider-rigid bus assembly is utilized to establish the connection between the equipment. The incremental dynamic analysis is carried out in the developed systems to produce the fragility function for each equipment. Also, the Monte Carlo approach is employed to evaluate the accuracy of the generated functions. It is concluded that the incorporation of connection parts in the model can significantly... 

This paper develops the seismic damage models of brick masonry veneer attached to the masonry infill without metal ties and assesses the life cycle cost of veneers subjected to earthquake excitation. Even though anchoring veneers to the backup wall has been prescribed in recent building codes, most of the existing brick veneers in seismic prone areas around the world lack the anchoring details. Besides, the damage and consequence models of masonry façades have not been presented in the FEMA-P58 database restricting detailed performance evaluation of buildings with unanchored masonry veneers. This study develops detailed finite element models to simulate various failure modes of the masonry... 

One of the most basic, longstanding open problems in the theory of dynamical systems is whether reachability is decidable for one-dimensional piecewise affine maps with two intervals. In this paper we prove that for injective maps, it is decidable.We also study various related problems, in each case either establishing decidability, or showing that they are closely connected to Diophantine properties of certain transcendental numbers, analogous to the positivity problem for linear recurrence sequences. Lastly, we consider topological properties of orbits of one-dimensional piecewise affine maps, not necessarily with two intervals, and negatively answer a question of Bournez, Kurganskyy, and... 

This paper proposes a risk analysis framework for substation structures based on reliability methods. Even though several risk assessment approaches have been developed for buildings, detailed risk analysis procedures for infrastructure components have been lacking in prior studies. The proposed framework is showcased by its application to a system of interconnected structures at a power substation in Tehran. Finite element models of structures are developed and validated in accordance with previous experiments. The uncertainties in the material, mass, and geometric properties of structures are described by random variables that are input to the finite element model. An artificial ground... 

Supersonic turbulent high-pressure jet flows, which are discharging in low-pressure quiescent ambient, are recognized as imperfectly expanded turbulent jet. Steady-state imperfectly expanded jet flow has been already studied analytically; however, the transient flow has not been thoroughly studied. In the present study, the transient imperfectly expanded jet flow with focus on fuel spray in combustion is investigated analytically employing two-step separation of variables method and Fourier-Bessel expansion. The results are validated using available experimental data. The effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied. Results... 

A semi-analytical method is presented to calculate the dynamic responses of a rectangular plate due to a moving oscillator. In previous analytical solutions of the moving oscillator problem, the elastic distributed structure has usually been modeled by an elastic beam structure. This restrictive assumption is removed in this study by assuming a general plate as two-dimensional elastic distributed structure. The method can be applied for any arbitrary path on the plate. A combination of the Fourier and Laplace transformation as well as the convolution theorem is used to solve the governing differential equations of the problem. A modified integration technique is then presented to solve the... 

Double-inlet pulse tube refrigerators are one of the most common types of cryocoolers. There are several advantages of double-inlet pulse tube refrigerators, such as not having moving parts, reliability, and long life. Double-inlet pulse tube refrigerators have been used in several applications such as cooling the semiconductors, infrared sensors, and astronomical detectors. In the recent decade, several research efforts have been performed to investigate double-inlet pulse tube refrigerators. Generally, most of them are experimental or numerical, and the recent literature survey shows there is not an analytical solution for the complete system of a double-inlet pulse tube refrigerator,... 

In this article a double-inlet pulse-tube refrigerator (DIPTR) is modeled using the nodal analysis technique. The main complexity of the problem is oscillatory and unsteady characteristics of the flow. Solving the flow field in the regenerator section of the system as a porous medium with nonlocal thermal equilibrium is challenging. Governing equations are developed applying mass, energy, and momentum equations to different finite volumes in each component of DIPTR. A numerical code (SharifPTR), with graphical user interface, has been developed to investigate the influence of geometrical and working parameters on performance. The governing equations are a system of boundary value problems....