Evaluation of seismic performance of existing steel structures considering histories of corrosion and repair

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Recently decrepit structures are increasing in number in Japan, because a lot of civil engineering structures that were constructed during the so-called high growth period have become 35-55 years old. Therefore, it is a strong necessity to ensure the seismic safety of these structures by carrying out proper maintenance and upgrading. So far as steel structures are concerned, the corrosion loss of material and the repair of structural members will cause changes of residual stresses and deformations due to redistribution of stresses. These changes of imperfections may have a large influence on the seismic performance of structures. In addition, asymmetry of corrosion and repair in structures will result in 3D. behavior, even if the structures have symmetry at the initial stage. Taking all the above facts into mind, we herein propose a method to evaluate the 3D ultimate behaviors of corroded and repaired structures caused by plasticity, ductile fracture and local buckling. In this method, … More a history of loss and gain of material by corrosion and repair is precisely considered. First, applicability of CFD is examined concerning corrosion environment that causes specific corrosion pattern and magnitude. Second, a new and accurate method is proposed to measure the detailed surface roughness of corroded members. Based on the detailed geometrical data of surface roughness, a prediction method based on the nonlinear FEM analysis is presented to predict the ductile fracture of corroded members. Third, a FEM-based 3D numerical method is proposed to evaluate the seismic performance of corroded and repaired steel structures, where the corrosion and repair processes including jacking up process under dead load can be precisely simulated. Finally, the aforementioned numerical methods are applied to some practical problems, such as the change of welding residual stresses due to the corrosion loss of material and its effect on the strength of thin-walled columns, residual strength of pre-stressed concrete beam with corroded PC steel bars and seismic.performance of corroded steel pipe piles used for -pile piers Less