International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 03 | Mar -2017
p-ISSN: 2395-0072
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A REVIEW ON EARTHQUAKE VULNERABILITY ASSESSMENT Nalina Kishore1, CK Prasad Varma Thampan 2 1PG
Student, Department of Civil Engineering, NSS College of Engineering, Palakkad, Kerala, India Department of Civil Engineering, NSS College of Engineering, Palakkad, Kerala, India ---------------------------------------------------------------------***--------------------------------------------------------------------2Professer,
Abstract – Majority of human beings live in earthquake
prone areas. Earthquake causes significant loss of life and damage of property every year. It is required to identify the damage of a structure caused due to varying ground motion intensities. This identification results will help an engineer to take necessary action against the after-effects of an earthquake. The vulnerability of a structure has to be found out under various ground motion intensity measures (IM) such as Peak Ground Acceleration (PGA). From this, fragility curves can be developed. Fragility analysis is a probabilistic approach, which is commonly used now-a-days. As per this method, different Damage states (DS) have to be defined and then probable damage of the structure in connection with the IM can be found. Fragility curves are generated from multiple Incremental Dynamic Analysis or IDA curves with the help of traditional curve fitting technique. Key Words: Fragility curve, Incremental Dynamic Analysis, Base isolation, Non linear dynamic analysis, Damage state.
assessment and it gives the probability of building damage level under different ground motion intensities. This assessment is generally used in disaster mitigation fields. The main objective of this paper is to review the development of fragility curve, especially analytical, to study earthquake vulnerability of a structure. Also this paper gives an overview about IDA which is used to analyze the behavior of structure under various ground motion intensities.
2. THEORETICAL BACKGROUND Earthquake effects of general type buildings are predicted with the help of some functions such as loss and damage functions. But these functions may not be useful for some kind of specific buildings. The development of the above mentioned functions are easy only if the user is an engineer experienced in non- linear analysis field. In disaster mitigation field, user must create various functions that can be used for both specific and individual type buildings. 2.1 Fragility Curve
1. INTRODUCTION Earthquakes are one of the most hazardous natural disasters that attack human and cause large damages especially in regions which is defined as high-seismic zone by geologists. Majority of human beings live in earthquake prone areas. Various seismic analysis approaches were proposed including both static and dynamic methods. Although seismology has been continuously advancing during the century, it is impossible to predict future earthquakes’ severity and time of attacking. Therefore previous earthquake data are still widely used to analyze buildings resulting in buildings for future earthquakes. Already constructed buildings may collapse under future earthquakes. Due to the difficulties in predicting earthquakes and its random nature, various probabilistic analyses were proposed in analyzing building seismic responses. In addition to uncertainties in seismic loads, uncertainties associated with building material, design process, building geometry, and construction will also lead to the use of probability to predict building responses. Fragility analysis is a probabilistic method which shows the probability of exceeding a certain damage level. This technique is commonly used in order to evaluate the earthquake vulnerability assessment of various structures. Fragility curve is a statistical tool used for the vulnerability © 2017, IRJET
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A fragility analysis is widely used for hazard assessment and earthquake vulnerability assessment of various structures . The fragility curve is a statistical tool showing the probability of exceeding certain damage state as a function of intensity measure(IM). It is developed from multiple IDA curves. Commonly used IMs are Spectral acceleration (Sa), Spectral displacement (Sd), Peak Ground Acceleration (PGA), Peak Ground Velocity (PGV) etc. Figure 1 shows a typical fragility curve with PGA along x-axis and probability of failure along y-axis. A point in the curve represents the exceeding probability of damage state at a given intensity measure. These damage states can be lateral drift, base shear, story drift etc. The function, which is used to generate fragility curve for a building, is generally found to be log-normal functions. 2.2 Incremental Dynamic Analysis (IDA) IDA is a computational analysis method of earthquake engineering to study the behavior of structure under seismic loads. Simulated building seismic responses obtained from IDA are represented by IDA curves that require a series of non- linear time history analysis with a suite of ground motions, during which the ground motion
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