What is the concept of fragility curve and how is it obtained? What is its application in designing procedures?
fragility curves are nothing but finding out the vulnerability of building. It is the graph of peak ground acceleration(PGA on X axis) and % of damage on Y axis.
Fragility curves is a statistical tool representing the probability of exceeding a given damage state (or performance) as a function of an engineering demand parameter that represents the ground motion (preferably spectral displacement at a given frequency).
In the area of hydraulic engineering, a fragility curve shows the performance (for instance the probability of the failure) of the flood defence as a function of the water level.
Fragility curves express the probability of structural damage due to earthquakes as a function of ground motion indices, eg, PGA, PGV.
is the cumulative distribution function (CDF) of the logarith of the EDPs (EDP=Engneering Demand Parameter accordingn to PEER framework)
Dear Arman Kamalzadeh
Please follow these links:
https://www.ideals.illinois.edu/bitstream/handle/2142/46584/Xinyuan_Yang.pdf?sequence=1
https://hal-brgm.archives-ouvertes.fr/hal-00558781/document
http://www.sparisk.com/pubs/Porter-beginners-guide.pdf
Article Fragility curves for R/C structures in Skopje (Macedonia) region
http://shinozuka.eng.uci.edu/Pdf/RepFrag.pdf
https://hal-brgm.archives-ouvertes.fr/hal-00558781/document
https://www.eccomas2016.org/proceedings/pdf/10028.pdf
Fragility curves are defined as the probability of reaching or exceeding a specific damage state under earthquake excitation. Various researchers have proposed different formulae for evaluation of fragility curves.
The fragility curves are established to provide a prediction of potential damage during an earthquake. These curves represent the seismic risk assessment and are used as an indicator to identify the physical damage in the strongest mainshock. Apart from the mainshock, probability aftershock must also be investigated to decide whether or when to permit re-occupancy of a building. The fragility function is also directly used to reduce damage cost and loss of life during a seismic event. Therefore, fragility curves can be used as a decision-making tool for both pre- and post-earthquake situations. Moreover, these curves may help develop future local code provisions. More detailed explanation on the fragility curves can be found in HAZUS manual.
This is also a good read: http://www.frontiersin.org/Journal/10.3389/fbuil.2017.00036/abstract
I am currently reading this right now. Hope it helps.
The fragility curve is a common type of damage function that evaluates the expected damage as a result of earthquake events.
The fragility curve expresses the probability that the structure will exceed a specific damage state of severe as a function of an earthquake’s intensity-measure parameter (e.g., PGA, PGV, S_a )
The fragility curves represent a useful tool for assessing the seismic vulnerability of underground structures. The seismic vulnerability of a structure can be defined as its susceptibility to being damaged by a ground-shaking of a given intensity (Crowley et al., 2006).
The fragility curve represents the relation between the probability of achieving a specified level of damage for a prescribed level of seismic hazard (ALA, 2001).
Different ways of estimating fragility curves:
1) Judgemental Fragility Curves
2) Numerical Fragility Curves
2) Empirical Fragility Curves
4) Closed-Form Solutions or Analytical Fragility Curves
5) Hybrid Vulnerability Fragility Curves
I agree with the definition for the fragility curve proposed by all answered or not answered the question.
But the approximately all fragility curves in the open literature are incorrect! This conclusion is the result of invention of my research team in the past more than 2 decades. As soon as the first failure occurred in one point of structure the structure is no longer the original one! Moreover in the method used for construction of this curve coefficients of the gravity acceleration Is used which have no correlation with the earthquake! Consequently the result curve has no relation with the structure!
Our certain result is as follows:
The collapse prevention curve is actually 1 minus the capacity curve. The horizontal axis is between 0 and 3 but is relative slenderness in place of PGA!
This great mistake is made and is continued!
I recommend all researchers pay attention, and try to contribute to solve this epistemic uncertainty for the human era?
Conventional fragility is defined as probability of failure versus a hazard measure index such as PGA of the earthquake. For construction of a conventional curve one have to do hundreds of thousands of Incremental Dynamic Analysis to obtain raw data. Then best fit a lognormal probability distribution on the data to obtain the fragility curve.
According to our research team investigation, the fragility curve is a function of the slenderness ratio of the structure, and shows the fled capacity of the structure. You may refer to my research documents on research gate.
Consider a simply supported column with a cross section (A), length (L), Yield stress (FY), radius of gyration (r). The maximum capacity is (CT=A*FY). The column design (effective or survive) capacity is (CS=SR*CT). The ineffective (fled fragile) capacity is (CF=FR*CT). Note that (SR+FR=1). A diagram of the (FR) versus a selected parameter (SP) is called the fragility curve. The same is true for any structure. In open literature the selected parameter is a measure index (IM=PGA, SA & etc.) of the hazard (earthquake), which is wrong! In reality the selected parameter is the equivalent slenderness ratio (L*L*FY/r*r*A*E*Pi*Pi).
Our research shown that, fragility (FR) is the complement of the capacity or survive (SR). I.e. SR+FR=1.
Fragility curves are essential tools for assessing the seismic vulnerability of civil engineering structures (Nuclear industry, Bridges, Buildings, etc.). These curves describe the probability of reaching or exceeding a specific damage state (Dk) as a function of a chosen ground motion intensity measure (IM).
Consider an upper bound for the capacity, under consideration. of the system (km). A ratio of the capacity upper bound that can be relayed (SR*km) on is called capacity , where the (SR) is survivor curve. On the other hand, the ratio of the upper bound that is not reliable and lost (FR*km) is fled or fragility capacity. The ratio (FR) is equivalent of the classical fragility curve. The (FR & SR) where (FR+SR=1) are inherent properties of systems. Look for Persian Curve in the literature, for more infs. and simple method of construction of these curves.
You may find a brief summary of the concept of fragility curve in the paper below. If you may have questions related to the paper, please do not hesitate to contact.Article Fragility functions for reinforced concrete columns incorpor...
Fragility curves define the degree of vulnerability of buildings to earthquakes by means of several damage levels, ranging from no damage to collapse. They can also determine the limits of each damage level for any type of structure. This determination is done either analytically or experimentally.
if i want to summarize it
it is going be the probability of exceedance of damage under specific loading condition
it helps you as a designer to forward think on the effects of threats on the structural systems you want to design.
It shows the probability of failure/exceeding a certain limit of the considered structure. Its design seems to be complex for me. I am also trying and working on it. If there are any relevant/suitable ways I am also very much interested to know.
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