Investigating the Effect of Parameters on Seismic Performance of I Girder Bridges
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Date
2021
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Addis Ababa University
Abstract
One of the major components of transportation systems and networks are bridge
structures, and earthquake is one of the natural effects which cause catastrophic damage to
bridge structures and leads to the transportation networks to be malfunctioned. Therefore,
bridge structures should be functional before and after earthquake because these bridges
serve for emergency during and after the earthquake.
Different parameters may have different effect under different seismic loadings;
therefore, their effect need to be assessed on seismic performance of the bridges. Undesired
failures can be prevented through a comprehensive understanding of dynamic load nature
and bridge’s structural response while keeping the cost-safety balance. Many structural
parameters such as geometry of the bridge and properties of the material of the bridge affect
the dynamic response of the bridges. Furthermore, the bridge structural response could be
significantly changed by characteristics of dynamic load. In most cases, involvement of
numerous parameter and complexity require the designer to investigate the bridge response
via numerical study.
Parametric studies were carried out using probabilistic approach for 2-span
prestressed I girder bridges. The effects of bridge deck thickness (superstructure mass),
concrete compressive strength, reinforcement steel yield strength of and skew angle on the
bridges seismic response were studied using nonlinear time history analyses (probabilistic
approach). The effect of the variation of these four parameters on the response of the
structure is analyzed to determine their effect on seismic performance of the bridge.
Computer software, CsiBridge 20 is used to analyze the bridge.
For this thesis, a 2-span prestressed I girder bridges with integral abutments is
selected and a detailed inelastic three-dimensional model is created for bridges with
different parameters. A set of nonlinear time history analysis (NTHA) for a ground motion
suite has been performed using these created models to compute the fragility analysis of
the bridges. Modified bridges of the original bridge are modeled by varying one of each
parameter and simulated repeatedly for pushover analysis and assessment of seismic
fragility of modified models. The above parameters affecting fragility curves and seismic
demands of these bridges have been examined using the outcomes from fragility analysis.In probabilistic seismic evaluation one of the popular tools is fragility curves. For a
given seismic intensity level the probability of bridge reaching or exceeding a particular
damage level is given by fragility curves which are conditional probability statements. In
this study, different parameters of a two-span continuous prestressed girder concrete bridge
have been assessed for seismic performance analysis. Results of dynamic analysis of the
prestressed girder bridge subjected to suit of ground motions is used to develop analytical
fragility curves.
It is observed that some parameters significantly affect fragilities, but not others; the
skew angle and yield strength of reinforcement steel are the most influence parameters
affecting the system fragility while the concrete compressive strength and bridge slab deck
thickness (superstructure mass) have a very small influence on the bridge.
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Keywords
Seismic Performance of I Girder Bridges