Sharif Digital Repository

Launch vehicle must overcome gravity and place its payload on determined orbit. Multi-staging of launch vehicles causes that the ratio of length to diameter become large and then launch vehicle behave elastically. In this study, the equations of motion using the Lagrangian approach drive at pitch plane. By adding elastic terms to control equations, the launch vehicle modeling is completed. Predictive model controller choose for control system.This controller is based on neural network. In this paper, the main concepts and neural network approach in this controller structure is introduced.Finally implementation of this method in Simulink environment for pitch control of a flexible launch... 

Choosing and designing a suitable lateral force resisting system in areas with high seismicity has always been one of the main challenges of structural engineers. Therefore, many systems have been developed and implemented over the past decades. Among them, we can mention reinforced concrete and steel moment frames, concrete and steel shear walls, bracing systems and even their combination under the title of dual systems. The choice of each of the above depends on many factors such as the importance of the building, the seismicity of the region, height of the building, architectural restrictions and also cost. Although the evidence of past earthquakes shows that, for a well-designed... 

Ribbed Bracing System (RBS) is an innovative structural system designed to eliminate the buckling of braces and enhance the behavior of structures under seismic loads. In this study, a collaborative performance of two RBS devices bracing a frame was assessed numerically and experimentally. In the numerical phase, the collaboration of ribbed braces at various stages of reversal loading was elaborated mathematically and was used for representing the system using finite element modeling. In the next phase, the numerically observed behavior was validated experimentally by conducting cyclic quasi-static tests of the proposed configurations. Two alternative RBS configurations—called Completely... 

The main purpose of this research is to investigate the possibility of using piezoelectric patches for active control of a number of steel moment resisting frames (MRF) structures under seismic loading. For this purpose, the response parameters of 3 structural models with different numbers of stories and bays are considered. Piezoelectric patches which are connected to different parts of beams and columns are used to apply the calculated control forces. For this purpose, Sap2000 software is used for preparing the structural models and the MATLAB software is utilized to compute the required control forces and optimal placement of the piezoelectric patches. Furthermore, the nonlinear behavior... 

This research studies behavior and implementing of telescopic lead shear damper in structures. Telescopic lead shear damper (TLSD) is a type of metallic yielding dampers that can dissipated energy with usage of shear yielding of lead. TLSD is made from behind act of two lead shear damper (LSD) like a telescope. Lead shear damper composed of two coaxial steel pipes where their interfacial gap is filled with pure lead. The interface of lead and steel pipes are roughened in a threaded form to guarantee the no-slip condition across the interface. Due to stable and fat force displacement hysteresis loops of TLSD, this device can be used in structures subjected to wind, seismic, and other dynamic... 

In this study, a new type of yielding metal dampers is proposed and evaluated numerically in finite element software. The damper consists of three main components, the core, the surrounding shell and the shear plates. These three components are interconnected in parallel and They are designed in such a way that when the system is under axial loading, the plates are much weaker than the shell and the core to remain in operation and elastic behavior until the end of the system and only the plates absorb the energy of the incident with their inertial shear behavior. This damper can be installed at the end of the Chevron braces, crossbar and diagonal. The use of the damper at the end of the... 

In this research, an investigation on application of parametric low amplitude high frequency vibrations In controlling the seismic response of structures is conducted. Evaluation of the influence of proposed control method on reduction of seismic response of structures, determination of stability map for the proposed structural control system and methods to use this control algorithm in a state needless to monitoring of instantaneous state of system (semiactive control) and a state needful to monitoring of instantaneous state of system (active control), is presented. in beginning chapters, the theory of method by extracting the equation of motion, considering oscillatory term in stiffness... 

Use of high-rise structures has become very common in recent decades for different purposes. Since, these structures are vulnerable to the wind and earthquake loads, many ways have been proposed to reduce or dissipate the input wind or seismic energy to the building structures. In this study, the effect of the tuned mass damper (TMD) with high mass ratio for high-rise structures is investigated. The proper functioning of the TMD to limit the vibrations of a structure is depended on the appropriate adjustment of its mass, stiffness and damping characteristics according to the load and structural specifications. The vibrational characteristics of the structures could change during sever... 

This study proposes a new metallic yielding damper for seismic applications. First, considering the damper proposed by curadelli in 2009 a simple lead yielding damper was manufactured to determine its maximum allowable axial deformation showing that it cannot tolerate suitable axial deformations. To solve this problem a telescopic damper with curadelli damper’s descriptions was manufactured and tested which increased the last damper’s allowable deformation 100%. Although new damper’s allowable deformation is twofold the old one, it was not enough for seismic applications. In the next step 6 dampers called lead shear dampers (LSD) with modified lead section were tested. LSD deformation... 

In this thesis, three new metallic-yielding dampers for dissipation of energy in structures are introduced and studied. The advantages of dissipation of energy from torsional yielding in comparison to tensile yielding is verified by performing both monotonic and cyclic tests on three aluminum alloys specimens and a mild steel specimen. The experiments confirm that the energy absorption of steel in torsion is much higher than that in tension. Three different mechanisms are introduced to transform the axial movement into the torsional rotation. Each mechanism is studied in details. The first two mechanisms can be mounted at the end of bracings and the third one is installed at the... 

Tuned Mass Damper (TMD) is one of the most popular device implemented in structures in order to control the motion induced by wind. The performance of TMD has correlation with its design, which is depending on the Structure dynamic properties as well as the specifications of lateral loading. During the earthquake since the both of the mentioned parameters will be uncertain, hence, the reduction of TMD’s sensitivity to its design parameters is vital. In this regard, in 2012, Maurizio De Angelis et al. tested the unconventional TMD – it has a large mass ratio – and corroborated its merit. The results were limited to short structures with linear behavior. This research not only verified... 

Preventing critical damages to structures and hence saving the lives and money is an inevitable work which a designer has to do. During the earthquake, huge amount of energy applies to the structure and finding a way to reduce transfer of this energy to main structure is crucial. For this purpose, Structural Control systems may be used. Metallic Dampers are one of those systems which absorb the earthquake input energy by having nonlinear deformations. In this Thesis, one type of this dampers which is innovated by Estekanchi, have been studied .Indeed, this damper is a connection between bracing and main frame. In this damper a U shape part acts as a sacrificing portion and absorbs energy by... 

Determining nonlinear dynamic behavior of structures is always one of the main goals of structure and earthquake engineers. The Modal Incremental Dynamic Analysis (MIDA) is one of the newest methods for analyzing the seismic behavior of structures. Indeed, this method has superseded the exact IDA method which is too complicated and prolix. Although, this method represents approximate results, high accuracy, fastness and low cost procedure made it an efficient and useful technique. Many researchers have used this method and investigated the accuracy of that and achieved proper results. Up to now no one has applied this method on structures which are equipped with dampers. In the procedure of... 

One of the most common failure modes of structures in earthquakes is soft story failure which causes by discontinuity of lateral force resisting elements like braces. so the ground floor acts as a soft floor. In this case columns are imposed to large deformation and plastic hinges are formed at top and bottom of the columns. This case is named as story mechanism (severe drift of the story). In most of this case building collapsed or going to collapse. To resolve this problem, different solutions are presented. One of the strategies under section (2-10) 2800 code is increase of designed load in columns of the soft floor. This measure cause to Significant increases in the sections of the... 

Taking into consideration of optimization methods has been increased recently. Optimization methods in engineering that consumes a lot of time and cost have been developed. Optimal design of structures is a matter that grabbed the attention of civil engineers and due to the deficiency of classical methods the modern approaches are being developed. One of the most important structures that are constructed for industrial and transportation purposes are truss structures.Structural control under support excitation is constraining the structure to some structural limitations. The final target in this paper is to apply the modern methods to get the optimal weight of structure under seismic loads.... 

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 this thesis, a new method is proposed to find the class of stabilizing control structures for interconnected systems from a graphtheoretic
perspective. The objective is to classify all possible control structures (static or dynamic), capable of stabilizing the closedloop system. The method can be formulated by using the characteristics of fixed modes of the system for arbitrary control structures.To this end, first, a method is proposed based on solving a set of discrete linear programming to determine whether a system is stabilizable via a decentralized controller. Subsequently, by solving a set of discrete linear feasibility problems, all possible stabilizing controller structures... 

Recently, there has been a surge of research activities in the area of networks in the systems and control community. One foundational class of questions on networked systems pertains to their controllability. While there are classical tests to check the controllability of linear time-invariant (LTI) systems, their applications to large-scale networks is numerically infeasible. Indeed, finding a minimum cardinality set of input nodes that ensure the controllability of a network is NP-hard. Moreover, when the interaction strengths along the edges of a network are unknown, the classical controllability test cannot be applied. To overcome these issues, an alternative set of approaches involves... 

In this thesis, a new method for the design and Control Performance Assessment (CPA) of the Rrestricted-Structure (R-S) PID controllers family (P, I, PI, PD …) is proposed. The proposed method is capable of a systematic analysis of the tradeoff between the structural complexity of the controller and its performance.During the past two decades, control performance assessment has attracted much at- tention from academic and the industrial researchers. One of the most recent tools is the RS-CPA, proposed by Grimble in which restricted structure controllers such as the PID are assessed against optimal LQG measures. When one is able to impose a specific structure onto the controller, such as a... 

Decentralized control is a typical method for the design of industrial MIMO control systems. However, in most multivariable systems, the existence of large interactions limit the achievable performance of such controllers. In the Nyquist Array design method proposed by Rosenbrock, the system interactions can be reduced using a precompensator, such that a decentralized controller may be used with acceptable performance. A well designed pre-compensator will effectively decouple the system and the multivariable systems may be considered as a set of SISO systems. It is therefore obvious that the key element in the Nyquist Array design method is the design of the pre-compensator. There are two...