| Steel structures damaged by corrosion not only have significantly reduced load-bearing capacity but also experience stress concentration effects due to pitting corrosion pits,which reduce the strength and stiffness of the steel and can even cause cracks and fractures.This study aims to examine how corrosion affects the bearing capacity of steel structures.Thus,H-shaped steel which is widely used in service was employed in the artificially accelerated corrosion test to obtain 4 groups of corroded specimens with varying corrosion ages.Then,the surface morphology of the corroded specimens was analyzed using morphology measurement instruments to determine the comprehensive evolution characteristics of the corrosion surface.After that,Tensile tests were performed on corroded steel plates cut from the H-shaped steel beam specimens to investigate the influence of corrosion surface morphology on the properties of steel.Finally,corroded H-shaped beams were subjected to bending tests,and a stochastic finite element modeling approach was developed to simulate random pitting damage in corroded steel structures.Using a combination of experimental research and finite element analysis,the influence of corrosion on the failure modes,bearing capacity,and deformation capacity of H-shaped beams were investigated.Moreover,a calculation method for the reduction coefficient of internal forces in corroded steel beams is proposed,aiming to provide a theoretical basis for performance evaluation and strengthening design of existing steel structures subjected to bending.The main contents and results are included in this paper as follows:(1)Based on the measurement results of the corroded surface morphology,the evolution characteristics of the corroded surface and the distribution of corrosion pit parameters were analyzed.The results show that the depth of corrosion pits and the ratio of corrosion pit diameter to depth with different corrosion degrees follow a logarithmic normal distribution;The evolutionary characteristics of the adjacent corrosion pits are led to connect and merge and the nucleation of new pits are continuously repeated on the corroded steel surface,and then more complex stepwise corrosion pits will appear.The morphology of these pits is comprehensively analyzed to clarify their morphology types and size ranges.(2)According to the morphological characteristics of the stepwise corrosion pit,a simplified model of it was proposed.Based on the statistical results of pit parameters,and with the aid of the finite element method,the influence of the inclination angle,step width ratio and aspect ratio of step on the stress concentration effect of corroded steel plates is systematically analyzed,and a comprehensive calculation model for the stress concentration coefficient of stepwise corrosion pits is also established.(3)Based on the tensile test results and corrosion surface measurement results of Q235 steel plates with different corrosion degrees,the correlation between the characteristics of corroded surface morphology and steel fracture mode,as well as the impact of corrosion on the mechanical properties of the steel were studied.The localized analysis of the fracture zone was then conducted to clarify the effect of critical pit parameters on the yield and ultimate load of the corroded steel plate and the variation of steel plate elongation with the average thickness of the fracture zone.(4)By conducting bending tests on H-shaped beams with varying degrees of corrosion,the deterioration patterns of yield load,buckling load,ultimate load,deformation capacity,and stiffness of beams were examined.Additionally,the deformation features and failure modes of H-shaped steel beams were analyzed by examining the laws of strain variation and the statistical results of bearing performance indicators of corroded H-shaped beams.(5)Based on the statistical analysis of corrosion pits and secondary development of ABAQUS by using Python,a modeling method for finite element analysis of corroded steel structure with random pitting damage,which accurately captures the characteristics of corroded surfaces and produces high-quality elements,was proposed.The validity of the method was verified by error analysis of the results between the simulation and the bending tests of H-shaped beams.In addition,the stress distribution characteristics of corroded Hshaped beams and their bending and shear resistance are analyzed,and a calculation method for the bending moment and shear reduction coefficient of corroded H-shaped steel beams is proposed. |
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