Sharif Digital Repository

Stratified flows are common in natural systems such as the oceans and the atmosphere. The hydraulics of two-layer flow over an obstacle, which helps with understanding and control of these flows, has been studied by many researchers. However, a type of two-layer flow, called the Approach-controlled flow, has not yet been fully understood, and there are ambiguities about it. Having considerable nonhydrostatic pressure in the so-called supercritical leap region, this flow type cannot be explained even qualitatively without accounting for the nonhydrostatic pressure. Also, the composite Froude number which is defined based on the hydrostatic pressure assumption for two-layer flows, is not... 

This study has been carried out for investigating the need for an appropriate and fast seismic analysis method to be applied in performance based design (PBD), and show the application of Endurance Time (ET) method and its advantages in PBD. The major goal of this project is analysis and study of behavior of concrete frames with retrofitted shear walls with FRP by ET method with acceleration functions which are compatible with actual earthquake and comparation with time history analysis, forand comparation of whole results with shear wall frames that are not retrofitted. Performance criteria of FEMA code were used fore comparation of two frame categories (retrofitted and not retrofitted).... 

The AISC Seismic Design Provisions include capacity design requirements for steel plate shear walls since 2005. This system consist of thin web plates that infill frame panels with steel beams as horizontal boundary elements (HBEs), and columns as vertical boundary elements (VBEs). The thin unstiffened web plates are expected to buckle in shear at low load levels and develop tension field action, providing ductility and energy dissipation through tension yielding of the web plate. HBEs are designed for stiffness and strength requirements and are expected to anchor the tension field formation in the web plates. VBEs are designed for yielding of web plates and plastic hinge formation at the... 

In recent years, by development of computer and analytical software, engineers intended to do complicated and delicate dynamic analysis instead of static ones. This cause reduction in uncertainty in structures analysis and designing, that improves environmental, economical, and safety performance. Currently there are two common methods which are accepted in major building codes, they are spectral and time history dynamic analysis which the former analyzes structures by using design code spectra based on determination of structures’ dynamic haracteristics, and the latest do it by imposing ground motions on the structure. The spectral dynamic analysis method has some errors and causes... 

Endurance Time (ET) is a fairly comprehensive analytical method based on time history analysis applied for evaluating structural systems excited by dynamic loading of earthquake. In such evaluation assessment measure is based on endurance time of structure versus applied accelerogram function and parameters such as stiffness, lateral resistance, period of vibration and dynamic characteristics are not used directly. In this research nonlinear dynamic analysis of elevated steel tanks with laterally braced framed tower under the loading of earthquake records and ET accelerograms was studied and effectivity of ET method in analyzing such elevated tanks was verified. Due to complication of... 

In the earthquake conditions, the collapse of cooling towers can stop power station activities and heavy financial losses that can be led increasing disaster dimentions finally. In this thesis for analysis of concrete hyperbolic cooling towers and generally for analysis of shell structures, the endurance time (ET) method benefits are used. Also with comparision between ET and standard time history method (THA), accuracy and probable errors of ET method are discussed. It should be noted that ET method is a new time history based method of seismic analysis expect that in this method, structure is imposed under specific intensifying acceleration functions. ET method is capabable for nonlinear... 

Nowadays using traditional hollow clay brick in buildings to make walls and partitionsisvery common. Non-load-bearing walls in buildings are used as architectural elements for design purposes and protecting the people that are inside the building from cold , heat and sound pollution .Due to the new technologies and developing building codes interms of structure , non-load-bearing walls behaviour that is always neglected seems necessary to be considered. In this research we have investigated the static and dynamic behaviour of a patented non-load-bearing wall made up of a claybrick system with specially-designed-precision grooved faces that eliminates conventional cement mortar and results... 

With improvement of design and analysis techniques, use of irregular bridges has been expanded. These improve the aesthetics of urban spaces as well as providing shorter highways in impassables. Horizontally curved bridges are among the type of structures, which needs to be designed based on three-dimensional analysis. In this thesis, three-dimensional nonlinear analysis was performed by Endurance Time Method (ET) on horizontally curved bridges. Nonlinear models have been analyzed under ET acceleration functions. Comparing ET results in DBE level with earthquake responses, the difference between these two methods were determined. ET estimated earthquake responses with good accuracy;... 

The aim of this research is the utilization of seismic life cycle cost estimation procedures and their implementation in optimal structural design. The costs include initial costs of constructing and life cycle costs. The weight of structural components and seismic consequences during the lifetime of structure are used as a criterion to assess initial costs and life cycle costs, respectively. In this research, seismic losses are determined based on ATC13, FEMA-P58 and FEMA-NIBS frameworks. Also, according to the high computational time of required dynamic analyses, the Endurance Time method is used which decreases the computational time simultaneously the dynamic predicted responses are... 

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... 

Modified Fish-Bone (MFB) Model and Consistent Generic (CG) Model are simplified Multi-Degrees-of-Freedom (MDOF) models, proven to be valuable tools in estimating seismic demands of moment-resisting frames, aimed to reduce the computational costs by decreasing the number of degrees of freedom. The preliminary expansion of these simplified models for steel moment resisting frames (SMRFs) were proposed by considering elastoplastic behavior and is not able to take into account stiffness and strength deteriorations in nonlinear dynamic behavior of structures. However, behavior deterioration affects seismic demands of SMRFs under intense earthquakes. For this reason, the present study is done to... 

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... 

Bridge is one of the most important structure that are used in urban transportation system. In recent decade, international standards and codes have introduced “Performance Based Design” for structure design criteria. Large and complex dynamic and time history analyzes are obstacles against this method; especially in finding optimum design that requires repeated analyzes. In this research, application of Endurance Time (ET) method in seismic design of urban concrete bridges has been evaluated and value based design of them has been presented. In ET method, seismic performance of structures under artificial intensifying accelerograms is investigated. Performance of structure in... 

Endurance Time Method (ET) is a dynamic analysis based on the Time History Analysis in which a predefined intensifying excitation would be applied to the structure and then the performance of the structure would be assessed based on the maximum time that the structure could fulfill the predefined criteria. This method has less complications than the other ordinary Time History methods and decreases the calculations. This method could be applied to Seismic Isolated Structures. Seismic Isolation is a method for decreasing seismic response of structures without increasing strength and ductility of the structure. In this Method all or parts of the structure would be separated from the ground... 

So far, several studies have been conducted on the endurance time method. In general, these studies can be categorized into two categories. The first group of studies are based on the theoretical foundations of this methodology and the second group of researches that use the method of endurance time in different engineering issues of earthquake and engineering, and also compare the results of this method with other conventional methods of seismic analysis.The purpose of this study, which is more in the first category of research, is to optimize the acceleration functions using various Transform, such as Fourier and Wavelet, as well as the use of various optimization algorithms. In optimizing... 

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... 

In recent years, due to the economical concerns in the structural design, many researches are devoted to introduce new frameworks for optimization of the construction cost as well as maintenance and rehabilitation costs in the life time. The bridges are the most crucial components of the transportation networks and their appropriate performances assures the flow in the transportation network. Hence, the reliability and response of such infrastructures especially in the emergency conditions and the state of servicibality after the hazards like earthquake play a key role in the social life. So far the design procedure of such infrastructures are only limited to the serviceability conditions as... 

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...