Browsing by Author "Chun, P"

Now showing 1 - 4 of 4

item: Conference-Full-text
Deterioration prediction of bridge by Markov chain model and Bayesian theory
(2013-11-08) Seto, D; Ohga, M; Chun, P
This manuscript presents a bridge deterioration prediction method by using Markov chain model and Bayesian theory. Markov chain model works by defining discrete condition states and accumulating the probability of transition from one condition state to another over discrete time intervals. The probability of transition is generally expressed by the matrix. Though the previous studies have predicted the bridge deterioration by developing deterioration curves by using the Markov chain model, the predicted value will not be necessarily suitable for the measured value in the future. Therefore, this study demonstrates a method to predict deterioration progress as a prediction interval by taking account of the uncertainty by the Monte Carlo simulation. In addition, the method to update the prediction interval after the inspection is developed by Bayesian theory. This research was developed by using inspection results of existing bridges in Japan, and the proposed mechanism is convenient for bridge engineers to take rational decisions on the maintenance management plan of steel bridge infrastructures.
item: Conference-Full-text
Effects of corrosion on degradation of tensile strength of steel bridge members
(2013-11-30) Appuhamy, JMRS; Ohga, M; Chun, P; Furukawa, S; Dissanayake, PBR
Evaluation of existing steel bridges becomes vital due to natural aging, increasing load spectra, deterioration caused by corrosion, increasing seismic demand, and other problems. In the result, bridge structures exposed to aggressive environmental conditions are subjected to time-variant changes of resistance. Corrosion becomes one of the major causes of deterioration of steel bridges and there have been many damage examples of older steel bridge structures due to corrosion around the world during past few decades. Controlling corrosion on bridge structures can prevent premature failure and lengthen their useful service life, both of which save money and natural resources, and promote public safety. Therefore, understanding of the influence of damage due to corrosion on the remaining load-carrying capacities is a vital task for the maintenance management of steel highway infrastructures. But at the moment, number of steel railway and highway bridge infrastructures in the world is steadily increasing as a result of building new steel structures and extending the life of older structures. Therefore, it would be an exigent task to measure several thousands of points, to accurately reproduce the corroded surface by numerical methods and to predict the behaviour of that corroded member more precisely. So, there is a need of more brisk and accurate assessment method which can be used to make reliable decisions affecting the cost and safety. Therefore, this paper presents the analytical results of many actual corroded steel members and comparison of them with their respective experimental results. Further, a simple and reliable analytical method by measuring only the maximum corroded depth (tc,max) is proposed, in order to predict the residual strength capacities of corroded steel plates more accurately.
item: Conference-Full-text
Enhanced effective thickness for remaining strength estimation of corroded steel bridge members
(2013-11-07) Appuhamy, JMRS; Ohga, M; Chun, P; Dissanayake, PBR
Infrastructure plays a major role in the economy of a country. Bridges are a major component of any infrastructure and the failure of a bridge will affect the economy of any country. Over the past decades there have been many damage examples of older steel bridge structures due to corrosion around the world. Exposure of a steel structure to the natural environment and inadequate maintenance will cause corrosion and leads to impairment of its operation. Efficient maintenance, repair and rehabilitation of existing bridges require the development of a methodology that allows for an accurate evaluation of load carrying capacity and prediction of remaining life. Therefore, careful evaluation of remaining load-carrying capacities of corroded steel bridge structures is of high importance in transportation and maintenance engineering. Even though there are some published methods to assess the strength reduction due to corrosion of bridges, all of them were developed by using specimens with about 30mm width. However during the preliminary investigation, it was found that many corrosion pits with more than 30mm diameters exist in actual severe corroded members. So, the influence of such corroded conditions could have been neglected and hence their actual remaining strengths might be different than those were obtained from those experimental studies. Therefore, this paper investigates the effect of actual corroded conditions on their remaining strength capacities and proposes a simple, efficient and accurate residual strength estimation method by using an enhanced effective thickness parameter with the correlation of maximum corroded depth, which can be used for the maintenance management of aged steel bridge infrastructures.
item: Conference-Abstract
Finite element analysis for bridge due to corrosion
Karina, CNN; Chun, P
Bridge inspection is an essential element to maintain existing deteriorated bridges followed by using efficient and effective method to acknowledge the remaining internal strength in the structure. Simple and quick method is considered to be most applicable approach to observe the structure rapidly. Thus, by referring to AASHTO LRFD standard, live load distribution factor (LLDF) is taken into account as a facility to develop simple numerical equation to predict reaction force and internal moment values for damaged-structure. There are eighty one finite element models (FEM) were created using commercial package finite element analysis software. One is non-damage model, eighty corroded models with particular corrosion conditions. The eighty one models were then analysed using LLDF approach. It resulted that the larger amount of corrosion, the higher change of LLDF values occurred while the reaction force values generally became lower. By utilizing LLDF equation for non-damage structure and exponential equation obtained from the relationship between reaction force values and corrosion cases, reaction force equation for damaged structure can be developed. As for internal moment equation, instead of using exponential equation, polynomial equation was used. With the proposed numerical equations to predict residual strength for damaged-structure, commercial analytical software usage can be eliminated to reduce inspection budget and complexity