Sharif Digital Repository

The purposeof this study isto findthe propertiesof an equivalent linear Multiple Degrees of Freedom (MDOF) system, or so-called substitute structure, that its response is an approximation ofthe target actualnonlinearMDOF structure’s response (Shodja, 2013). In that regard,thestiffness anddampingmatricesofthe substitutestructure are considered as functions ofthe stiffnessand dampingmatrices ofthe actualnonlinear structure. Inthisway,the substitute structurescan be constructedthroughtrial and errorfor structures with different fundamentalperiods, damping ratios and number of floors.Inthat regard, a number of multi-story steel moment resisting frames are considered. The ductilities of these... 

In this study, seismic performance of steel diagrid structures is investigated using far-field earthquake records and their seismic performance factors, such as overstrength factor (Ω_0), ductility ratio (µ_T) and response modification coefficient (R) are evaluated according to the FEMA P695. To meet this objective, 12 archetype 3-D models of diagrid structure with two different height of 8 and 12 stories and three different diagonal angles of 45, 63.4 and 71.5 degrees are designed according to the ASCE 7-10 and using response modification factor R=3.6. With regard to the main horizontal beam connections with the diagrid system, equal number of models with pin and rigid type of connections... 

Ultrafast signal processing in time-domain with high resolution and reconfigura-bility is a challenging task. This paper, for the first time, introduces a time-varying metasurface consisting of graphene microribbon array for implementing time-lens in the terahertz domain. Given that the surface conductivity of graphene is proportional to the Fermi energy level in the THz regime, it is possible to change the phase property of the incident electromagnetic pulse by changing the Fermi level while the Fermi level itself is a function of voltage. Upon this fact, a quadratic temporal phase modulator, namely time-lens has been realized. This phase modulation is applied to the impinging signal in the... 

In today's era, metal nanoparticles play an important role in technologies emerging from different sciences, such as chemistry, physics, optics, material science, due to their unique characteristics. In the development of nanooptics science, it can be said that metal nanoparticles play an important role. The ability of conductive electrons collective oscillation causes surface charge density fluctuations in nanoparticles, this phenomenon is known as surface plasmons. Surface plasmons are surprisingly coupled with light and cause the significant increase in the intensity of optical fields induced in nanoparticles. Therefore, with the presence of localized surface plasmons or plasmon... 

Understanding of the Molecules is the main purpose of the chemistry. Ab-initio molecular dynamics (AIMD) as a branch of the computational chemistry, tries to give us a deep comprehension of the molecule, and its chemical, physical and optical activities. This comprehension, relies on the accuracy of quantum mechanics, in addition to the speed of the classical mechanics. The mixing of the quantum mechanics and the classical mechanics could simulate activities of the atoms in the time-domain, provided the mixing is done with precaution. This, in turn, helps us to forecast the response of a molecule in different situations, and also translating the macroscopic phenomena in a nanoscopic... 

To date, the plasmonic properties of many metallic and semi-conducting materials have been investigated and used in various industries. One of the plasmonic material categories that have always been considered is polycyclic aromatic hydrocarbon or PAH, whose plasmonic resonance energy depends on the charge state of the molecule. In this regard, it is easy to change the plasmonic resonance energy via changing the induced charge, which is a unique feature of the mentioned materials. In addition, plasmonic structures with excitations in the infrared region are able to enhance the vibration intensity of absorbed molecules by increasing the electric field around themselves. Therefore, they have... 

In this research, the problem of locating fire stations and allocating equipment has been studied and a simulation-optimization approach has been presented to solve the problem. The mathematical models of this research were developed based on the idea of the randomness of the covered demand and the maximum expected coverage model. In these models, the issue of non-availability of equipment to cover accidents, the random nature of accidents, various fire incidents and the equipment needed to cover them are considered. Two mathematical models with deterministic and non-deterministic approach with different scenarios for demand are proposed. The non-deterministic model is developed with the aim... 

One of the main concerns of industrial companies’ managers is providing an efficient logistics system. To achieve an efficient logistics system, the fleet planning problem is studied by many researchers in recent years. This problem consists of multiple sub-problems at three levels: operational, tactical, and strategic. These sub-problems are closely related to each other and need to be studied and addressed in an integrated manner. In this research, an attempt is made to provide an integrated framework to solve the vehicle routing problem (operational), outsourcing problem (tactical), and fleet composition problem (strategic). These problems have various uncertainties, including customer... 

Reducing the seismic response of structures under dynamic loads has been highly considered by many researchers in the past few decades. Among them, Tuned Mass Dampers (TMD) have been studied extensively and used as a mean to control the response of structures under earthquake and wind loadings. In the majority of these studies, it is assumed that the structural models are located on rigid base and only their linear response has been considered. Soil-Structure Interaction (SSI) and nonlinear response of structures could have significant effect on the dynamic characteristics of structures that could results in detuning of TMDs. In this study, a number of 3-D nonlinear steel structural models... 

In this study, the change in friction damper’s optimal slip load in 3-D structures due to soil-structure interaction was evaluated. Using AISC-LRFD code, an 8 story shear building has been designed considering gravitational and equivalent static lateral loads. Then, the changes in friction damper’s optimal slip load due to PGA and soil type variation were studied. In this part two PGAs and two soil types were considered. Seven strong ground motions, recorded on soil types E and D was used for each of the two soil types. After normalizing the PGAs of selected records, these records were used for dynamic time history analyses. In the next step, the soil-structure interaction effect has been... 

Viscoelastic(VE) dampers are among the most practical passive control devices that are used to reduce the seismic-induced response of the structures. In this regard, extensive parametric studies have been conducted so far to investigate the performance of these dampers in reducing the seismic response of the structures under various types of ground motions and site soils. In most of these researches, the effect of soil-structure interaction (SSI) is neglected which is acceptable only for the structures located on stiff soils. In present research, the effect of the soil-structure interaction on the performance of VE dampers in reducing the seismic structural response is investigated. Also,... 

In the present study, the performance of Viscoelastic Dampers in reducing the seismic response of the structures was investigated. For this purpose, first the effect of added damping to the system was studied. Number of 3-D steel structural models, with and without eccentricity which are designed with the 2800 code (first edition) and 519 code provisions that is not satisfied the provisions of the code-2800(third edition) is considered. It is assume that this system is located on a relatively stiff soil (soil type II based on Iranian Seismic Standard Code - 2800), a number of compatible earthquake records also considered to be used in the parametric studies. The results indicate that in... 

Tuned Mass Dampers(TMD) are among the most studied passive or active control devices that have been used around the world to control the lateral vibration of different building structures. On the other hand, since 2-D structural models are not appropriate for estimating the true response of the eccentric structures, application of 3-D models have been considered for determining their seismic-induced coupled lateral-torsional behavior. In this research, the performance of the Active Tuned Mass Dampers (ATMD) in controlling the seismic response of 3-D structural models was investigated. Three structural models with 4, 8 and 15 number of stories and 3 different eccentricities (0, 10% and 15%)... 

In recent years there has been a huge amount of attention in the application of the base isolation system as a passive procedure to limit seismic response of structures. A number of international codes including UBC97, ASCE07-2005, and ASCE-2010 have devoted a special part for the Seismic analysis and design of base-isolated structures. The present work investigates the vertical distribution of the lateral seismic force, for base-isolated structures suggested by the ASCE07_05 code under near field earthquakes. Near field earthquakes have attracted so much interest among the researchers and engineers due to their disastrous effects on structures. According to the recorded data, it is... 

In existing societies, transportation of water, oil, gas and other liquids in great amounts between distant locations is economically feasible only through pipelines. Design of buried pipelines against static loads is an established and straight forward process. On the other hand, because of difficulties in predicting the behavior of buried pipelines under seismic loads and also lack of sufficient studies in this field, there is no specific code oriented approach for performance analysis of buried pipelines under seismic loads. Due to insufficient three dimensional numerical analyses on the behavior of buried pipelines crossing active normal and normal-oblique faults for different dip angles... 

Buried pipelines are among the most important elements of lifelines that are used for distribution of water, gas, petroleum, etc. Previous studies indicate that the severe damages that resulted in complete disruption of pipelines, is mainly due to permanent ground displacement caused by faulting. Previous studies on this subject have mostly focused on strike-slip and normal faulting. Since it is reported that damages due to reverse faulting can be more severe than damages caused by normal faulting, a comprehensive study on the behavior of buried pipelines subjected to reverse faulting is needed. In this thesis, the effect of various parameters including burial depth, pipe diameter, pipe wall... 

Recent studies in the area of damage assessment of structures under severe earthquakes have shown that plan asymmetry of structures have considerable effects on the severity of the induced damages. In these cases, structure enters into its nonlinear behaviour, and both structural and nonstructural elements sustain large forces and deformations. Nowadays, due to the complication of nonlinear dynamic analyses in estimating these forces and deformations in case of seismic ground motion, the use of nonlinear static analysis methods has increased. These procedures expose the structures to monotonically increasing lateral forces with an invariant height-wise distribution until a predetermined... 

A large number of bridges in Iran are deteriorating under long and heavy traffic loadings, while getting closer to the end of their design life time. Therefore, many of them have been exhibiting various problems such as excessive vibration or large deflection under the normal service loadings. So, mitigating traffic-induced bridge vibration and damages is necessary to extend their efficient period of serviceability. On the other hand, application of active and passive control devices in structural retrofitting have absorbed the attention of many engineers and researchers. In this work, the performance of an active control system made of piezoelectric actuators is investigated in reducing the...