Method for assessing detail fatigue crack propagation of steel bridge

Abstract

The invention discloses a method for assessing the detail fatigue crack propagation of a steel bridge. Aiming at a steel bridge which is widely used in a road bridge system and is severe in fatigue crack dangers, the method comprises the steps: firstly building a bridge model and a local zone crack submodel through finite elements, obtaining an existing bridge load according to the definition and sampling of a vehicle and other random variables, and obtaining the boundary conditions of the submodel based on the whole bridge finite element analysis and the submodel technology; secondly updating the submodel through employing local remeshing, and carrying out the crack propagation finite element analysis; thirdly extracting a stress intensity factor amplitude, calculating a mean crack propagation rate, a mean crack propagation angle, the circulating number of times of each crack propagation step, the mean number of the stress intensity factor amplitude caused by a single vehicle, and the fatigue life; finally achieving the simulation of the fatigue crack of the steel bridge and the assessment of the fatigue life, so as to guide the subsequent maintenance and reinforcing operation.

Description

technical field [0001] The invention belongs to the field of structural crack growth simulation and fatigue life prediction, and relates to a fatigue crack growth evaluation calculation method for steel bridge details. Background technique [0002] Due to the fatigue effect of tens of thousands of vehicle loads per day, material aging and environmental erosion, etc., the steel bridge will inevitably experience damage accumulation and resistance attenuation during its century-long service life. Fatigue damage can occur at lower levels. However, this kind of gradual damage is often concealed and will lead to serious consequences; when the damage inside the structure accumulates to a certain threshold, catastrophic accidents will often occur. Therefore, fatigue damage and crack propagation are one of the typical failure modes of steel bridge details. The initiation and propagation of fatigue cracks (seams) not only affect the safety of the structure, but also cause a lot of po...

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Problems solved by technology

However, this kind of gradual damage is often concealed and will lead to serious consequences; when the damage inside the structure accumulates to a certain threshold, catastrophic accidents will often occur

Therefore, fatigue damage and crack propagation are one of the typical failure modes of steel bridge details. The initiation and propagation of fatigue cracks (seams) not only affect the safety of the structure, but also cause a lot of post-maintenance costs

However, due to the randomness of the loading environment of the bridge in service, the interaction of the local performance of the crack growth and the whole bridge effect, and the complexity of the simulation of the composite crack growth, the current evaluation method for the detailed composite fatigue crack growth of the steel bridge in service rarely reported

Existing analysis of cracks and their propagation focuses on components or specimens, ignoring the interaction between local and global, and most of the constant amplitude loads fail to consider the actual load size and randomness of the bridge, making it difficult to accurately simulate the details of the actual steel bridge when it is in service. The fatigue and crack growth properties of

[0003] Due to the complexity of the actual structure and boundary conditions, the complex crack growth of in-service bridge details cannot be well studied by experiments and theoretical analysis

With the application of the finite element method in the analysis of engineering structures, people naturally link the finite element method and crack growth analysis together, thus forming the finite element method for simulating crack growth; however, due to the singularity of the crack tip (topology is not Continuous), structural geometric complexity, multi-dimensionality of crack self-propagation, overall and local interaction, randomness of load and other factors, so crack growth analysis is difficult and particular

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