Nguyen LAM
Study on the Measure of Marine Salt around the Bridge Section and the Numerical Simulation of its Behavior
Eiji IWASAKI, Masatsugu NAGAI
In recent years, reduction of life cycle cost of infrastructure such as bridge, improving the resource productivity with earth-friendly technology has become an important problem. The defect of steel material is corrosion, and painting cost makes maintenance cost push up the LCC. To solve this problem, the using of unpainted weathering steel is increased. The weathering steel restrains corrosion by generating the rust layer that is called protective rust on the surface of steel. The corrosion of weathering steel is influenced by many factors of environment such as marine salt, the anti-freezing agent, rain, moisture, humidity (wet time), the temperature on the surface of the steel material, the temperature around the bridge construction region etc. Generating of the protective rust is strongly affected by marine salt. The following condition of unpainted weathering steel should be satisfied: maximum amount of marine salts density is less than 0.05mdd (mg/dm2/day). However, the corrosion is not same at the entire bridge, and a state of corrosion is different in the part of it. It is possible to understand the amount of marine salt in the bridge construction area by site investigation before construct the bridge. However, because of the interaction of a bridge and its surrounding geographical features set the amount of the marine salt, wet time around bridge section, it is difficult to evaluation for these amounts before built the bridge, and estimation technique is necessary. Therefore, it is thought that if the amount of marine salt around bridge section is presumable, the state of corrosion on weathering steel is known before construction of the bridge. This thesis discusses an estimation of marine salt around section of the bridge by comparison between numerical result with measurement of marine salt and rust”Ēs salt content measured by Doken-type Tank method and Gauze method.
The results are as follows:
”¦The satisfactory results are obtained from the numerical simulation, but the difference in the upper outside part of the upstream side web is large, and it requires calculation with three dimensional analyses.
”¦The amount of salt content in rust and the numerical values have the same trend, it is thought that the numerical simulation could simulate the real phenomena
”¦In case of which the space under bridge is modeled as infinitely, the amount of marine salt increase but keep the same distribution.
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