Sharif Digital Repository

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 it’s advantages in PBD. Necessary theories were generated in hazard analysis, bi-directional seismic analysis, introduction of dynamic push-over curve and application. As a secondary goal, potential of this method in more complicated nonlinear domains is assessed. Application of ET and its advantages in PBD is shown with an example of SMF, NDCBF, CBF and BRBF building after modeling nonlinear interactional behavior of beams and columns, and also modeling buckling and... 

Recent studies show that irregular structures have been damaged more than regular ones during earthquakes. This proves importance of seismic response determination of this type of structures. Today, Codes define irregularity in structures and restrict seismic analysis and design of these types of structures. The Endurance Time (ET) method is a time-history based dynamic pushover procedure for seismic analysis and design of structures that has been recently proposed in Sharif University. This thesis illustrates ET capability in analysis and design of vertically irregular frames. Irregular frames with three, seven and twelve story high were designed with two types of mass and stiffness... 

Endurance Time Method (ET) is a type of dynamic pushover procedure in which the structure is analyzed under special series of accelerograms, called ET acceleration Functions (ETAF) and the response of structure is sketched versus time until the collapse state. With evaluating response curve and the time which damage in structure reach the expected value, the final assessment of structure can be made. In this dissertation, the application of ET method for Non-linear 3 dimensional seismic analysis of steel moment frames under earthquake multicomponent excitation is investigated. For this purpose, various patterns of ET loading are investigated and the most appropriate algorithm in... 

In recent decades, large economic losses and social impacts following earthquakes and hurricanes have revealed the need for improved design criteria intended to reduce consequences including economic impacts to an acceptable level along with life protection. So, it is tried to express the expected performance of structures as financial and social criteria. Any assessment on earthquake consequences requires estimations of structural responses to seismic excitations. Endurance Time (ET) method as a dynamic procedure requiring reasonably reduced computational effort compared to other common time-history based procedures, is used to estimate the response of the structure in all levels of hazard... 

The objective of this research is to evaluate the concept of a new design methodology based on the total value of the structure namely Value Based Design of structures (VBD) by the use of potential benefits of the ET method. While prescriptive and also performance based approaches of seismic design commonly try to find a structure with lower initial cost satisfying a number of requirements under seismic actions, a new design approach to incorporate directly the concept of value in design procedure have been formulated here to achieve an economical design with lower total cost in its life time. In this method the design sections of structural elements are considered as optimization parameters... 

The Energy Dissipating Restraint (EDR) is a friction device which can be used to dissipate the energy introduced to a structure by a seismic event.A special characteristic of this device is that it is self-centering, which makes it preeminent among other friction dampers. As a result of high nonlinearity associated with the behavior of the EDR, the analysis and performance assessment of the structures which are outfitted with EDR entail quite a few nonlinear time-history analyses. Regarding the substantial computational cost of this method, the existing provisions have authorized the use of more economical alternative methods for the analysis of the structures whose motions are controlled... 

In this research the appilication of a new method named Endurance Time (ET) analysis in seismic analysis of multi span bridges in linear and nonlinear ranges is investigated. Endurance Time is a time history based method of seismic analysis. In this method structure is subjected to an intensifying predefined acceleration function and different damage indices of the structure are evaluated through analysis time. The Endurance Time criterion and the Endurance Time acceleration functions have been generated in previous researchs of ET group. Using 7 earthquake records which are selected from hundred ones of PEER database based on FEMA p695 recommendations, several scaling methods are used to... 

The expansion of new analytical methods along with evolving computational tools has accelerated the recognition of obscured nonlinear behavior of structures. In this process, the innovative Endurance Time method is a great step which presents a comprehensive assessment of structural behavior with less computational cost. The accuracy of this method among the unpredictable nature of earthquake engineering, as well as its fastness and simplicity, has attracted the attention of researchers. This research is part of a project on introducing and assessing the capacities and restrictions of the Endurance Time method, which investigates its usage in analyzing performance of concrete structures with... 

The aim of this research is value based optimum design of structures to minimize the costs imposing on them during lifetime. For this purpose, an optimization procedure is used to get optimum solutions. Therefore, in this optimization problem, total costs are objective functions and required limits of codes are as the constraints. 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 the probabilistic seismic assessment framework, which depends... 

In this research the capability of a new method named Endurance Time analysis in seismic assessment of single and multi degree of freedom structures in nonlinear range is investigated. Endurance Time analysis is based on time history analysis but in this method structure is subjected to an intensifying acceleration function and different damage indices of the structure are evaluated through analysis time. This method can be a useful tool for executing Performance Based Design of structures. Firstly the Endurance Time criterion is defined and the progress of the generation of Endurance Time acceleration functions is described. Also the optimization procedure used for the generation of... 

In new method of performance-based design, the behavior of structure during earthquake is considered more realistically, and applying damage parameters like plastic ductility and inter-story drift to determine the seismic performance of structures is suggested. Damage indexes, the contribution of damage parameters to damage capacity of structural members, are defined to specify damage level of each element. In addition, damage spectrum which is the diagram of values of certain damage index versus natural period of single-degree-of-freedom system will be useful to seismic assessment of existing structures and seismic design of new ones. By the way, endurance time (ET) method can be... 

The actual value of structures should not be evaluated only based on initial cost, because failure cost and economical losses due to corrosion and natural hazards can be catastrophic. The aim of this research is Comparative study of life cycle cost of steel and concrete building systems designed based on standard 2800 by Endurance Time Method. These costs include initial cost and life cycle cost Due to the aftermath of the earthquake in the life of the structure. In this research, because it requires a lot nonlinear dynamic time history analysis, Endurance Time Method used which is both good accuracy and also drastically reduces the cost of computing-off. Selected models for the study, four,... 

Exact and safe structural analysis and design under various loadings is an important issue, which have engaged engineers for a long time. Till now, building design codes have suggested three main methods for seismic analysis of structures, which consist of: Static analysis, Pseudo-dynamic response spectrum analysis and Time history analysis. The first two methods are too approximate, especially in irregular structures which demand exact 3d analyses. The most reliable method is Time history method. With advance of computational tools, engineers tend toward using more reliable analysis methods and using old fashioned rough methods is becoming less popular. One of the issues, which is important... 

In recent decades, most of the codes have placed a high value on Performance Based Design of structures; however, these methods are computationally complex and time-consuming, and caused researchers to seek new and efficient methods to investigate performance of structures under different intensities of seismic loading. This issue is much more obvious when optimum design of structures, which requires repetitive analysis, is investigated. This investigation tries to provide better insights into the dynamic behavior of structures in continuous performance levels. As a first step, this research aims at analytical investigation of new type of metallic damper called Cartridge Damper, and in the... 

The structure performances during past earthquakes indicate the importance of predicting behaviors of irregular structures under earthquakes. If the irregularity exceeds an expected limit, a seismic analysis should be carried out by a dynamic analysis method. The Endurance Time (ET) is a time-history method, base on dynamic analysis for seismic analyzing and designing the structures, in which structures are subjected to intensifying accelerogram functions and their Endurance Time is measured. One of the most applicable methods for RCF analysis is the Concentrated Hinge Model which is used in this research too. The needed parameters for modeling plasticity in concentrated hinge are achieved... 

Based on special properties of metal dampers such as high energy dissipation, stable hysteric cycles and simple application, low cost, insensitivity to changes of temperature and ability to be substituted after occurring of earthquakes, they are being used for structures control. ADAS and SSD are two kinds of metal dampers which are connected to top of the chevron braces and under the middle of beams. When shear forces are applied, these dampers yield and enter the plastic zone. In Endurance Time (ET) method gradually intensifying acceleration functions are created in a manner that the linear and nonlinear response spectra of them, while being proportional to average of real earthquakes... 

Since the advent of earthquake engineering, several methods have been created to repel earthquake forces. One of these methods is to decrease lateral stiffness of structure at its base level. Some systems, such as base isolations which are installed at the base level of structures can provide this softness. In recent years a new kind of bracing system named geometrical (off-center) bracing system has been presented with three convergent members that can increase the main period of structure by applying high displacement at first floor in order to prevent high frequencies from entering structures. Despite of previous researches, in this study the mentioned bracing system has been assessed... 

In many urban and rural areas, steel frames are infilled by masonry materials such as bricks. The resulting structural system is commonly known as an infilled frame. Nonlinear analysis of infilled frames using conventional analysis methods, such as incremental dynamic analysis (IDA), requires high levels of modeling complexity and computational effort, therefore in most practical cases; the infill panel is often neglected. Such an approximation results in a high level of inconsistency in evaluation of the actual behavior (e.g. lateral strength and stiffness) of these frames. Introducing more simple and straightforward methods of analysis and design for these frames, can be a solution to this... 

With the transportation progress and appearance of transit industry, necessity of modern vehicles redounded to appearance of heavier trucks with higher speeds, moving on the roads. In addition, with the progress in mechanical engineering and automobile industry, appearance of such trucks is growing increasingly. So, bridges as one of the structures that civil engineers design and construct, nowadays are subjected to higher moving dynamic loads in comparison with the past. As a result, lots of investigation and researches in the universities and institutions all over the world are being conducting on the effects of the vehicle speeds on the dynamic stresses of the bridges. Bridge codes... 

In the countries with offshore oil field, Such as Iran, Offshore platforms are important. Hence seismic analysis of offshore platforms is important. Different methods for seismic assessment of these structures are presented. But these methods has own advantage and disadvantages. (Such as long analysis time and simplified assumptions of linear behavior), but by using Endurance Time method, the method had shown the ability to analyze complex structures, It is hoped that these problems can be resolved. In this study, providing a suitable model of soil and structures of a single pile and then an offshore platform using DEEPSOIL and Open SEES software and performance of these structures at...