CHRISTIAN ALEJANDRO MENDOZA IBARRA

Analytical study on the evaluation of axial stress on corroded high strength bolts

Eiji Iwasaki

In recent years, the maintenance of civil engineering structures has turned into a problem in Japan due to the aging of the structures constructed during the period of high economic growth. 
Corrosion degradation is the most usual problem in steel bridges. The primary cause of corrosion of steel bridges is the exposure of steel to atmospheric conditions like marine exposures and industrial environments. 
In steel bridges the reduction produced by corrosion its more usual in structural members such as bolted connections, the complicated shape in these structural members promotes the accumulation of oxidizing agents. 
For that reason, is important to consider the effects of corrosion degradation in these structural members to carry out a maintenance works. 
The decrease in axial force due to corrosion itfs one of the biggest problems that exists, because it causes a decrease in the slip resistance of the joint, which can cause a possible collapse in the structure. 
The previous researches that used a FEM analysis to determine the residual axial force, they have the particularity of not considering the part of the thread in detail. 
For that reason, in this study, the research objectives are to determine if the consideration of thread in detail has an important role in the determination of the axial residual stress when the reduction by corrosion occurs. 
In addition, the effect of the location of corrosion thinning is also examined.
The analytical results revealed that the proposed model obtained similar values to the experimental model. 
In addition, it was possible to identify that the factors that affect the decrease in axial stress are the properties of the type of steel, the thickness of the plates and the amount of plastic strain generated in the members.
It was also revealed that corrosion location near the washer can promote greater reduction of axial stress.