Cables are always a critical and vulnerable type of structural components in a long-span cable-stayed bridge in normal operation conditions. This paper presents the surface characteristics and mechanical performance of high-strength steel wires in simulated corrosive conditions. Four stress level (0MPa, 300MPa, 400MPa and 500MPa) steel wires were placed under nine different corrosive exposure periods based on the Salt Spray Test Standards ISO 9227:1990. The geometric feathers of the corroded steel wire surface were illustrated by using fractal dimension analysis. The mechanical performance index including yielding strength, ultimate strength and elastic modulus at different periods and stress levels were tested. The uniform and pitting corrosion depth prediction model, strength degradation prediction model as well as the relationship between strength degradation probability distribution and corrosion crack depth would be established in this study.
KEYWORDS: Bridges, Reliability, Structural health monitoring, Sensors, Finite element methods, Fiber Bragg gratings, Data modeling, Stochastic processes, Calibration, Temperature metrology
This paper presents the reliability estimation studies based on structural health monitoring data for long span cable
stayed bridges. The data collected by structural health monitoring system can be used to update the assumptions or
probability models of random load effects, which would give potential for accurate reliability estimation. The reliability
analysis is based on the estimated distribution for Dead, Live, Wind and Temperature Load effects. For the components
with FBG strain sensors, the Dead, Live and unit Temperature Load effects can be determined by the strain
measurements. For components without FBG strain sensors, the Dead and unit Temperature Load and Wind Load effects
of the bridge can be evaluated by the finite element model, updated and calibrated by monitoring data. By applying
measured truck loads and axle spacing data from weight in motion (WIM) system to the calibrated finite element model,
the Live Load effects of components without FBG sensors can be generated. The stochastic process of Live Load effects
can be described approximately by a Filtered Poisson Process and the extreme value distribution of Live Load effects can
be calculated by Filtered Poisson Process theory. Then first order reliability method (FORM) is employed to estimate the
reliability index of main components of the bridge (i.e. stiffening girder).
This paper presents an improved finite element (FE) model updating method for Binzhou Yellow River Highway Bridge
and its associated uncertainties by utilizing measured dynamic response data. The dynamic characteristics of the bridge
have been studied through both three dimensional finite element prediction and field vibration previously. A
comprehensive sensitivity study to demonstrate the effects of structural parameters (including the connections and
boundary conditions) on the modes concern is first performed, according with a set of structural parameters are then
selected for adjustment. According to the eigenequation considering uncertainties, the proposed methodology transforms
model updating problem for Binzhou Yellow River Highway Bridge into two deterministic constrained optimization
problems regarding the predictable part and uncertainties of structural parameters. Both the predictable part and
associated uncertainties of the structural parameters could be obtained in iterative fashions so as to minimize the
difference between the predicted and the measured natural frequencies. The final updated model for Binzhou Yellow
River Highway Bridge is able to produce natural frequencies and associated frequency uncertainties in good agreement
with measured ones, and can be helpful for a more precise dynamic response prediction.
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