دانلود رایگان مقاله انگلیسی روش ارزیابی آسیب وارد شده به ستون های فولادی توسط کمانش موضعی - اشپرینگر 2018

Abstract

In this study the process by which a steel column subjected to strong and repeated loading undergoes failure is investigated. Furthermore, a damage index is developed by using factors related to damage along with a relevant analysis method. A cantilevertype box-type steel member, which is assumed to undergo buckling deformation, is used for the analysis. A nonlinear analysis with repeated displacement control is conducted by applying a compressive load that leads to failure along with a predetermined compressive load to the steel member. The main variables considered in this analysis are the load stock pattern and the type of steel (SS400, SM570, and Posten 80). The influence of each variable on the failure mode, deformation capacity, and damaging process is described. The failure processes for each type of steel are compared. The results indicate that the failure of a steel member under strong repeated loading is governed by local buckling and that the failure of a steel member is directly related to the local strain.

5. Conclusions

The process by which a box-type steel member subjected to strong and repeated loading undergoes failure and the factors relevant to damage were used to develop a new damage assessment method using a nonlinear analysis. The major conclusions of this study are as follows.

1. By using the dimensionless local stress-ratio–strain-ratio envelope curve, a new damage index was proposed. This damage index is an area ratio of the stress ratio and the strain ratio corresponding to the cumulative plastic strain of each load step and the ultimate load state, and the cumulative damage to the member can be taken into account when evaluating the damage capability.

2. The results of a damage assessment using the damage index for a box-type steel member indicated that the position where local buckling occurred was the most severely damaged. This indicates that damage is closely related to the local buckling and plastic strain.

3. The boundary conditions of the model in this study were set as one end fixed and one hinged end. For this reason, local buckling, when occurring concentrically, occurred at lower positions when the strength of the steel member is higher. On the other hand, when repetitive loading is applied, buckling occurred around the edge where stress could be easily concentrated owing to cumulative plastic deformation, regardless of the strength of the steel member.

4. Although the strength of Posten 80, which is the highly tensile, is 1.5 times higher than that of SM 570, the strain restoration of Posten 80 was not lower than that of SM 570.