Sharif Digital Repository

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... 

The parallel combination of friction damper with shape memory alloys has been proposed as a self-centering friction damper (SFDB) in the past. The aim of this study is to improve the performance of the SFDB as M-SFDB and investigate its effect on seismic responses of steel moment resisting structures. The basic idea used in the proposed M-SFDB damper is to create sloped surfaces and using SMA bolts to change the slip load of friction during the loading and unloading cycles. In order to evaluate the effect of the proposed mechanism, four types of 4, 8 and 12-story structures located on site classes B and D are designed using ASCE_7-10 and AISC_360-10 codes. These structural models include... 

The necessity of providing synthetic acceleration records suitable for seismic assessment of the structures in the regions whose seismological history has not enough instrumental recordings has become one of the main concerns of the earthquake engineers. Despite being accurate in estimating earthquake ground motion, physics-based methods involve complicated procedures and need the detailed information about source, path and the site conditions of the scenario event which is not available for lots of engineering problems. The main goal of this dissertation is to introduce a novel stochastic method for the simulation of the non-stationary earthquake acceleration records compatible enough with... 

The irregularity in structures is divided into two categories of irregularity in vertical and irregularity in plan. The irregularity in vertical can be caused by ultra-change in dynamic properties of the structure such as mass, stiffness or strength. Research studies indicate that this irregularity leads to intensify the applied damages to structures in severe earthquakes. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). That is due to consideration of higher modes effects and the shifts in inertia load pattern as the structural system experiences nonlinear behavior. Nowadays, due to complexity of nonlinear dynamic... 

Project Management has clearly designed to achieve a successful outcome of the projects. However, without a proper practicing, it might convey a different result. Companies are increasingly using organizational project management in their work to achieve company goals. The purpose of this study is to identify the challenges in Iran for successful implementation of directorial patterns based on the PMBoK (Project Management Body of Knowledge) and PRINCE2 (PRojects IN Controlled Environment-2nd Version). This paper presents the results of a study aiming at investigating the impacts of implementing project management processes of PMBOK and PRINCE2 and themes within Iranian construction... 

Shape memory alloys (SMA) are materials with shape memory effect and high recentering capacity. Recently, application of SMAs in building structures and for the purpose of structure control during earthquake has been considered by many researchers. Researchers have tried to reduce the residual displacement of the structure after earthquake and also increase the dissipated energy by using this material in different forms such as wire, spring, bolt, etc.. In this research the seismic performance of steel structures equipped with SMA connection has been studied, considering the soil and structure interaction. The purpose of this research is to investigate the amount of required SMA bolts in... 

In this study, the changes in the mean vector and the covariance matrix of engineering demand parameter (EDP) distributions for different intensity measures and ground motion selections is evaluated. Although, the changes in the mean distribution of EDPs have been extensively studied in the literature, but the changes in the covariance matrix of EDPs distributions caused by ground motion selections has not been paid the due attention. In other words, no study has specifically looked into the effect of intensity measure changes on the covariance matrix; therefore, for the purpose of this study, several steel frame models were considered with perimeter special moment resisting frames (SMRF).... 

Progressive collapse occurs when the loading path of a structure is changed so that the other structural elements loaded beyond their capacity and fail. Generally, structural progressive collapse is categorized in different types based on the failure progress mechanism. Most dramatic progressive collapse occurred in 1968 at the Ronan Point residential apartment through an internal gas explosion. The type of progressive collapse of the aforementioned building was the Pancake collapse. Widespread efforts have been put to introduce a simplified static procedure to simulate the removal column phenomenon as in the Pancake collapse, which is a dynamic event involving vibration of building... 

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... 

With the advent of virtual memory machines and parallel processing, there has been a considerable shift toward computer-aided design and nonlinear analysis of structures. But increasing the size of computer memory or increasing the number of processing units are not the only ways to achieve a satisfactory solution to a large, complex problem. Another useful method is to reduce the size of the problem so that the reduced model is small enough to be solved at an appropriate processing level, and yet the important engineering behavior of the model is preserved in the reduced problem.Reduced models as an alternative, have gained considerable attention throughout the years in order to meet the... 

Existing structural irregularities (in plan and elevation) has always been among the important causes of structural failures under strong earthquakes. The torsional related damages have especially been very important in multi-story buildings as the torsional behavior of structures changes their uniform translational vibration and causes concentration of demands in the elements at the perimeter of the buildings. On the other hand, the Tuned Mass Dampers (TMD) have in general been accepted as an effective passive structural control device to suppress the structural vibration. In this study, Three 3-D, irregular (in plan) steel structural models with 4, 8 and 15 number of floors are considered... 

The importance of the liquid storage tanks in this era is as much as their contained liquid that we use in our daily lives. Many studies have been carried out on these influential structures considering various aspects. The major damages inflicted to the liquid storage tanks in Loma Prieta, Lozan, Hokaido, Arzinkan, Northridge, Kobe, Izmit & Haiti Earthquakes, has led the researchers to perform various experimental and analytical studies on this regard in the last few decades. The most important part of a safe design of a storage tank is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Moreover,... 

Principal component analysis (PCA) is a conventional tool for dynamic system analysis. In this paper, a new damage diagnosis method is presented based on sensitivities of principal components obtained from PCA of Frequency response functions (FRFs). Damage identification, determination of its location and estimation of the damage severity are conducted by an innovative well established sensitivity relation of PCA results. Then, sensitivity matrix is obtained by using measured frequency of damaged structure, and comparison of PCA of the intact structure with PCA from FRFs which are measured at sensors locations. Damage location and its severity are calculated by model updating procedure. This... 

Recent studies regarding the damage assessment of structures under severe earthquakes have shown that vertical irregularity of structures have considerable effects on the severity of the induced damages. In these cases, structure enters into its nonlinear behavior, and both structural and nonstructural elements sustain large forces and deformations. In general, nonlinear dynamic procedure (NDP) can provide more realistic results than nonlinear static procedures (NSPs). This is due to consideration of higher modes effects and the shifts in inertial load patterns as the structural system experiences nonlinear behavior. Nowadays, due to the complication of nonlinear dynamic analyses in... 

The seismic behavior of the non-structural components and their effect on the overall performance of the building structures is among the important issue that should be thoroughly investigated from different aspects such as the resiliency, and the replacing cost. On the other hand, in analysis and design of structures, assuming a rigid under-laying soil is not always right and the effect of soil-structure interaction should be taken into account in certain cases. A flexible support could affect the dynamic characteristics of the structures through elongating their natural vibrating periods as well as increasing their damping ratios, thus should not be ignored. If the period of a... 

On Grade steel tanks are widely used in petroleum complexes, refineries, power plants and many urban facilities. Increasing the number of attacks, incident reports and operational events happening in refineries proves the sensitivity of these strategic facilities against various Hazards such as explosion. So, the damage assessment of tanks after the explosion is important for their maintenance and repair.Since some of the tanks containing flammable materials, quick action to estimate the possible damage and required strengthening and retrofitting or disconnecting the input to a plant lifeline is of utmost importance. Therefore, special attention to study the blast loading and the study of... 

During the last few decades, the seismic codes have allowed the building structures to behave nonlinearly under the strong ground motions to dissipate the input seismic energy. That usually takes place by formation of plastic hinges in the structural elements which in turn leads to some permanent deformation, such as residual drifts, in these structural members. Repairing these damages are both time and cost consuming. Rocking frames are among the newly introduced re-centering lateral resistance systems which in combination with some dissipating devices (fuse) prevents the formation of plastic hinge in the main frame by concentrating the plastic deformation in these energy dissipating fuse,... 

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... 

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...