Sharif Digital Repository

Seismic base isolation is the most effective method of protecting and strengthening structures against seismic damage caused by large to small earthquakes and aftershocks. Providing damping and energy absorption of the seismic isolation at the structure's base level can significantly reduce the cost of repairing and strengthening the structure in addition to reducing seismic damage. However, besides these advantages, due to their high cost, seismic isolations in major infrastructure projects, hospitals, and crisis management centers should have economic and social justification. In this regard, a value-based seismic design approach can justify this important issue. In recent years of... 

The aim of this study is to develop the value-based design approach using the endurance time method as a comprehensive and efficient framework in optimal seismic design of structures. Optimal resource allocation is an interesting and important subject in the seismic design of structures from the theoretical and practical viewpoint. Finding optimal solutions requires the use of a trial and error process that is accompanied by repetitive structural performance evaluation. The seismic design process will be efficient when it provides a comprehensive and reliable estimation of the earthquake effects and be cost-efficient in terms of computational demand. In this regard, the value-based design... 

The wind phenomenon has always caused significant damage to structures. Suffering from extensive damage and loss over the years has led researchers to establish the novel science of wind engineering. Wind engineering references introduce wind as an intricate dynamic and random phenomenon and encourage engineers to familiarize themselves with its exact effects on structures by utilizing the latest methods of structural analysis, such as time history analysis. In this research, the idea of a new method for time history analysis of tall buildings against the wind is proposed. In this method, the purpose is to determine the responses of the structure against any wind of any intensity and return... 

This research has been performed with the aim of gaining familiarity with various types of seismic isolation systems, their unique features and numerous advantages, factors affecting their performance and finally their modelling and design. Despite the advantages of seismic isolation systems as control instruments, but where there is not enough information on the involved parameters in the performance of these systems, there is possibility of unpredictable behavior of the structures. Hence, considering the extent and influence of each parameter involved in the performance of the isolators, a parametric study is performed utilizing the 3D models under multi-directional excitations, using the... 

Vertical addition of existing buildings provides more living space without the need for more land use. Also adding a story on an existing building is one of the common needs in metropolitans. However, the structure may bear high risk due to vertical addition. This study aims to model conventional concrete structures built in Tehran and then assess and compare the seismic performance of base structure and extended structure. Seismic performance of a system is defined as their efficiency in providing enough safety and reducing the Life-Cycle Cost. For this purpose, seven archetypes as base structures and eight extended structures corresponding to base structures, that had residential... 

Highway bridges are one of the key components of transportation network and play a significciant role in the recovery of societies after extreme events such as flood and earthquake. The dysfunction or failure of bridges significantly impacts commerce and services and cause direct and indirect costs. Thus, the recovery of theses components immediately after extreme events is vital issue. In this study, a framework developed to evaluate the life-cycle resilience of bridges using the Endurance Time method. At the first part, the effect of deterioration due to corrosion on the seimic vulnerability and resilience of RC bridge investigated by ET method. To this aim, a procedure described to... 

Disorders with creating the localized states, which are the states with limited spatial distribution, cause carriers of these states become limited to small part of space and cannot participate in the transport. If energy of these states is near the Fermi energy, the Anderson metal-insulator phase transition occurs. In this thesis,we studied type of disorders and determining their Hamiltonian and by studying definition of localization from different aspects, we attained a better explanation of disorders effects on materials. With studying the localization scaling theory, we ex-amined conditions of localization in different dimensions. Then for determining the green function and therefor the... 

In this study, first nano structure powders of Fe3AL / Al2o3 by different percentages of reinforcement phases (10, 20 and 50 percent of volume) based on mechanical milling procedure was created. To do so, iron, Al and iron oxide (hematite) pure powder based on special weight percentages mixed with each other and milled in 20 to 100 hour periods based on two different weights of ball toward powder: 10 and 20. Morphological variations, particles sizes and powder densities, lattice strain and phase variations in different timing periods of mechanical milling process was studied by Scanning Electron Microscopy(SEM) , analyzing apparatus of particles sizes by laser , gaseous picnometer and X-ray... 

Structural optimization has always been one of the concerns of engineers. Usually, engineers decide to optimize the structure with its weight. Nowadays we know that the best solution in weight optimization is not good for the structural damage and performance of the structure due to risk analysis.In this study, using the genetic algorithm to reduce construction cost, Loss and damaged cost and total cost of the structure by calculating structural damage based on FEMA-P58 guidelines according to two types of connections (rigid or hinge) and their elements (beams and columns) in two types of structures 4 and 8 story has been investigated.At each stage of increment in algorithms, first, the... 

In the field of estimating the expected performance of structures under the excitation of earthquakes of different magnitudes, the Endurance time method has been introduced as a fast method in recent years. What is needed now in this method is to study the assumptions and definitions used in this method, to choose more logical definitions, to unify them, and to prove the statistics of this method in the overlapping and generalizable range of different structures. For this purpose, in this dissertation, different definitions have been evaluated in the process of using the Endurance time method and IDA. The results of different definitions for the target time equivalent to each earthquake... 

Electrical substations and its vital components such as switchgears, have experienced severe damage during recent earthquakes, followed by widespread blackouts around the world. To improve the seismic resiliency of power grids and use probabilistic decision-making frameworks, comprehensive fragility data for the different equipment is needed. The purpose of this study is to assess the vulnerability of equipment in substations and to develop fragility curves for this equipment. For this purpose, four main equipment of switchgear, namely circuit breaker, disconnect switch, current transformer and surge arrester, have been modeled in three dimensions and verified. After examining the different... 

In this thesis , we consider nonnegative (continuous) weak solutions of the porous medium equation with source , u_t-∆u^m=u^p, and p>m>1 .
Assume that, m>1 and 1< p/m u_t-∆u^m=u^p,xϵR^n ,tϵR
has no nontrivial, bounded radial solutions u≥0 .
In one space-dimensional, the conclusion of the result mentioned above remains true without the assumption of the radial symmetry. The proof is based on the intersection-comparison arguments , zero number argum- ents and a key step is to show the... 

Although laws vary in the competitive business world of today and the changing supply and demand parameters show that the process of delivering new products to market is very important.Most organizations today have found that spending more than ever on trusting in traditional competitive levers such as quality, cost reduction and differentiation in selling more products and services are not enough to be successful in market, instead notions such as speed, flexibility andagility can have a significant trend toward offering new products and services. There aresome good reasons for knew that organizations need new ways to develop their new products to survival, compete with its competitors and... 

This study focuses on the risk assessment of reinforced concrete tall buildings subjected to ground motion excitation. In order to assess the vulnerability of tall buildings, twelve-, and twenty-four-story four-bay reinforced concrete moment resisting frames are studied. This evaluation is done through developing fragility curves. These fragility curves provide the probability of exceeding the multiple damage states for a given intensity (e.g. CAV) of ground motion excitation. To develop the fragility curves, a great number of nonlinear dynamic analyses were conducted in the open-source platform OpenSees. Since the PEER Guidelines for Performance-Based Seismic Design of tall buildings (PEER,... 

Technology scaling allows integrating multiple cores onto a single chip to make the mainstream for advanced embedded systems. However, technology scaling is envisaged to aggravate the reliability of on-chip systems due to increasing transient fault rate due to lower voltages and shrinking transistor dimensions that lead to smaller critical charges. Transient faults are typically resulted due to high-energy particle strikes in hardware and manifest as bit flips. Multi-core systems provide a great opportunity to implement reliability mechanisms such as redundant multithreading (RMT) and process level redundancy. Task replication (e.g. RMT) is a well-established technique to achieve high... 

Snaking Vibration and buckling of drill string in the horizontal well was investigated in this research. Sinusoidal and helical critical buckling load are obtained for a specific drill string.
Drill string is modeled both analytically and numerically (finite element method). Drill pipes are considered as a clamped-clamped beam with constant cross section and the well is considered as a hollow cylinder. The thickness of cylinder was large enough to model the surrounding soil of the well. Buckling is a complex deformation and is somehow a random phenomenon. In addition, the length and the continuous contact between drill pipes and the well make the finite element model very huge and the...