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Seismic fragility estimates for corroded reinforced concrete bridge structures with two-column bentsZhong, Jinquan 15 May 2009 (has links)
To assess the losses associated with future earthquakes, seismic vulnerability
functions are commonly used to correlate the damage or loss of a structure to the level of
seismic intensity. A common procedure in seismic vulnerability assessment is to
estimate the seismic fragility, which is defined as the conditional probability that a
structure fails to meet the specific performance level for given level of seismic intensity.
This dissertation proposes a methodology to estimate the fragility of corroded
reinforced concrete (RC) bridges with two-column bents subject to seismic excitation.
Seismic fragility functions are first developed for the RC bridges with two-column bents.
All available information from science/engineering laws, numerical analysis, laboratory
experiments, and field measurements has been used to construct the proper form of the
fragility functions. The fragility functions are formulated, at the individual column,
bent, and bridge levels, in terms of the spectral acceleration and the ratio between the
peak ground velocity and the peak ground acceleration. The developed fragility
functions properly account for the prevailing uncertainties in fragility estimation. The probabilistic capacity and demand models are then combined with the probabilistic
models for chloride-induced corrosion and the time-dependent corrosion rate. The
fragility estimates for corroded RC bridges incorporates the uncertainties in the
parameters of capacity and demand models, and the inexactness (or model error) in
modeling the material deterioration, structural capacity, and seismic demands. The
proposed methodology is illustrated by developing the fragility functions for an example
RC bridge with 11 two-column bents representing current construction in California.
The developed fragility functions provide valuable information to allocate and
spend available funds for the design, maintenance, and retrofitting of structures and
networks. This study regarding the vulnerability of corroding RC bridges will be of
direct value to those making decisions about the condition assessment, residual life, and
the ability of lifeline structures to withstand future seismic demands.
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Adaptive Reliability Analysis of Reinforced Concrete Bridges Using Nondestructive TestingHuang, Qindan 2010 May 1900 (has links)
There has been increasing interest in evaluating the performance of existing
reinforced concrete (RC) bridges just after natural disasters or man-made events
especially when the defects are invisible, or in quantifying the improvement after
rehabilitations. In order to obtain an accurate assessment of the reliability of a RC
bridge, it is critical to incorporate information about its current structural properties,
which reflects the possible aging and deterioration. This dissertation proposes to
develop an adaptive reliability analysis of RC bridges incorporating the damage
detection information obtained from nondestructive testing (NDT).
In this study, seismic fragility is used to describe the reliability of a structure
withstanding future seismic demand. It is defined as the conditional probability that a
seismic demand quantity attains or exceeds a specified capacity level for given values of
earthquake intensity. The dissertation first develops a probabilistic capacity model for
RC columns and the capacity model can be used when the flexural stiffness decays nonuniformly
over a column height. Then, a general methodology to construct probabilistic seismic demand models for RC highway bridges with one single-column bent is
presented. Next, a combination of global and local NDT methods is proposed to identify
in-place structural properties. The global NDT uses the dynamic responses of a structure
to assess its global/equivalent structural properties and detect potential damage locations.
The local NDT uses local measurements to identify the local characteristics of the
structure. Measurement and modeling errors are considered in the application of the
NDT methods and the analysis of the NDT data. Then, the information obtained from
NDT is used in the probabilistic capacity and demand models to estimate the seismic
fragility of the bridge. As an illustration, the proposed probabilistic framework is
applied to a reinforced concrete bridge with a one-column bent. The result of the
illustration shows that the proposed framework can successfully provide the up-to-date
structural properties and accurate fragility estimates.
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