GANKHUYAG SARANGUA

Investigation of stress state of corroded truss lower chord member at the grid points.

Eiji IWASAKI

The upper surface of the lower chord material at the point of the truss bridge is a part where water logging such as snow and dust are likely to accumulate and local corrosion is likely to occur. Deterioration and corrosion of the intersection elements in a truss bridge lead to affecting multiple members and greatly affect the entire structure, so it is important to understand the stress distribution of the intersection elements.
The purpose of this study is to examine the stress state of the lower chord material intersection point where corrosion thinning has occurred, using FEM analysis software for the intersection point of the Warren type truss bridge.
The stress distribution of the lower chord material rating changes depending on the angle of the diagonal material and the insertion depth of the diagonal material into the gusset. Therefore, the diagonal member’s angle is divided into 4 patterns, and each model has 3 patterns of insertion depth (c) of the diagonal member into the gusset, all of which are 12 patterns.
The corrosion range is:
-When the entire floor on the upper surface surrounded by gussets on both sides is corroded.
- When the inside of 200mm from the left and right gussets and the end is corroded
The results obtained by conducting this research are shown below.
(1) When the same force is applied, stress bigger than the edge and center of the upper surface is generated in the gusset just above the lower chord.
(2) When tensile force and shear force are applied, the stress increases as the amount of corrosion increases.
(3) When a tensile force was applied, the stress increase showed a similar stress distribution in each model regardless of the change in the angle and the insertion depth into the gussetIn contrast, when a shear force is applied, the stress decreases as the angle increases, and the stress due to the insertion depth into the gusset is almost equal.