Determining the Capacity of Deteriorated Reinforced Concrete Bridge Structures Under Seismic Loading

Determining the Capacity of Deteriorated Reinforced Concrete Bridge Structures Under Seismic Loading
Author:
Publisher:
Total Pages: 50
Release: 2013
Genre: Dissertations, Academic
ISBN:
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With the continual deterioration of the US infrastructures, the matter of safety is consistently in question. Records show that 80% of the entire US transportation infrastructure, such as bridges, roads, railways, etc. is either deficient or functionally obsolete. This thesis focuses specifically on the seismic capacity and demand of bridge structures at different levels of deterioration that may occur over time. This thesis also relates the design demand and capacity of the original and deteriorated bridges. The purpose is to show that the existing conditions of deteriorated bridges are more critical under earthquake loading than expected. A simple bridge design was constructed using design guidelines from Caltrans. Accelerograms were taken from recorded earthquakes within the state of California. The model was developed in SAP2000 and nonlinear time-history analyses where performed for multiple earthquake motions to demonstrate the demand and the capacity of the bridge. Deterioration was predetermined as a 10, 25, and 50 percent reduction in the diameter of the longitudinal reinforcement bars and therefore, 15, 37.5, and 75 percent reduction in the diameter of the lateral reinforcement bars. The results did confirm that with deterioration, even as little as ten percent, the bridge was no longer able to provide the displacement capacity that it was originally designed for and failed when the displacement demands were larger than this reduced capacity. Current methods utilize only dead and live loads to determine the maximum load-carrying capacity of a structure; deterioration is not explicitly accounted for. The contribution of this thesis is a set of first-of-a-kind nonlinear time-history analyses that examine the two dimensional behavior of columns at critical sections, such that evaluation of the columns' reduction in rotation capacity due to deterioration under seismic loading can be formalized.

Seismic Design Aids for Nonlinear Pushover Analysis of Reinforced Concrete and Steel Bridges

Seismic Design Aids for Nonlinear Pushover Analysis of Reinforced Concrete and Steel Bridges
Author: Jeffrey Ger
Publisher: CRC Press
Total Pages: 396
Release: 2016-04-19
Genre: Technology & Engineering
ISBN: 1439837759
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Nonlinear static monotonic (pushover) analysis has become a common practice in performance-based bridge seismic design. The popularity of pushover analysis is due to its ability to identify the failure modes and the design limit states of bridge piers and to provide the progressive collapse sequence of damaged bridges when subjected to major earthq

Seismic Fragility Estimates and Sensitivity Analyses for Corroding Reinforced Concrete Bridges

Seismic Fragility Estimates and Sensitivity Analyses for Corroding Reinforced Concrete Bridges
Author: Do-Eun Choe
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:
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The objective of this study is to develop methodologies to estimate and predict the fragility of deteriorating reinforced concrete (RC) bridges, and to identify the effect of design and construction parameters on the reliability of RC bridges over time to assist in the design and construction process. To accurately estimate the fragility of deteriorating bridge, probabilistic capacity and demand models are developed. In addition, to simplify the calculation cost maintaining accuracy, fragility increment functions are developed. The proposed fragilities account for model uncertainties in the structural capacity, demand models, corrosion models. Furthermore, proper account is made of the uncertainties in the environmental conditions, material properties, and structural geometry. To identify the effect of design and construction parameters on the reliability of RC bridges, a sensitivity and importance analysis is conducted. Sensitivity analysis for an example bridge subject to corrosion is carried out to identify which parameters have the largest impact on the reliability over time. This dissertation considers different combinations of chloride exposure condition, environmental oxygen availability, water-to-cement ratios, and curing conditions, which affect the reliability of bridges over time. The developed models are applicable to both existing and new RC bridges and may be employed for the prediction of service-life and life-cycle cost analysis of RC bridges.

Seismic Fragility Estimates for Corroded Reinforced Concrete Bridge Structures with Two-column Bents

Seismic Fragility Estimates for Corroded Reinforced Concrete Bridge Structures with Two-column Bents
Author: Jinquan Zhong
Publisher:
Total Pages:
Release: 2010
Genre:
ISBN:
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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.