CN-121999893-A - Method and system for predicting corrosion fatigue life of steel box girder bridge

CN121999893ACN 121999893 ACN121999893 ACN 121999893ACN-121999893-A

Abstract

A method and a system for predicting corrosion fatigue life of a steel box girder bridge relate to the technical field of steel structure bridge life prediction. The method comprises the steps of establishing a corrosion pit initiation time calculation model considering a cyclic load acceleration effect, establishing a short crack propagation time calculation model representing corrosion environment strength based on measured corrosion current and coupling the influence of stress level, establishing a long crack propagation time calculation model representing corrosion environment strength based on measured corrosion current and coupling the influence of stress level, and adding the corrosion pit initiation time, the short crack propagation time and the long crack propagation time to obtain the total corrosion fatigue life of the steel box girder bridge in the corrosion environment. The invention can solve the problem that the synergism of corrosion and fatigue is difficult to quantify in the prior art.

Inventors

LIU YI
YOU CHUNHUA
PENG JIANXIN
GUO FANBO
XU BINLIN
LUO JIANGHUA

Assignees

湖南工学院

Dates

Publication Date: 20260508
Application Date: 20260119

Claims (8)

1. The method for predicting the corrosion fatigue life of the steel box girder bridge is characterized by comprising the following steps of: s1, establishing a calculation model of pit sprouting time considering a cyclic load acceleration effect; S2, establishing a short crack propagation time calculation model, wherein the model represents corrosion environment intensity based on actually measured corrosion current and couples the influence of stress level, the initial length of a short crack is the critical length of the conversion from a corrosion pit to a crack, and the termination length is the critical length of the conversion from the short crack to a long crack; S3, establishing a long crack extension time calculation model, wherein the model represents corrosion environment intensity based on actually measured corrosion current and couples the influence of stress level, the initial length of a long crack is the critical length of transition from a short crack to a long crack, and the termination length is the critical length of extension of the long crack to failure; S4, adding the pit initiation time, the short crack extension time and the long crack extension time to obtain the total corrosion fatigue life of the steel box girder bridge in the corrosion environment.
2. The method for predicting corrosion fatigue life of steel box girder bridge according to claim 1, wherein, The etch pit germination time calculation model is based on Faraday's law and is combined with normalized stress amplitude to represent the acceleration effect of cyclic load on corrosion rate.
3. The method for predicting corrosion fatigue life of steel box girder bridge according to claim 1, wherein, The short crack extension time calculation model is based on Paris's law, and takes parameters obtained by non-dimensionalization treatment of corrosion current as measurable input quantity, and determines the short crack extension rate together with the stress intensity factor range.
4. The method for predicting corrosion fatigue life of steel box girder bridge according to claim 1, wherein, The long crack extension time calculation model is based on Paris's law, and takes parameters obtained by non-dimensionalization treatment of corrosion current as measurable input quantity, and determines the long crack extension rate together with the stress intensity factor range.
5. The method for predicting corrosion fatigue life of steel box girder bridge according to claim 1 or 2, wherein, The etch pit germination time calculation model is that In the formula, Indicating the time of the pit initiation stage; Indicating the depth of the etch pit; indicating the number of electrons released; representing the Faraday constant; Representing the density of the steel; An acceleration factor indicative of cyclic loading versus corrosion rate; Representing a normalized stress amplitude; Represents the molar mass of iron; Current coefficient indicating corrosion; Represents activation energy; representing a universal gas constant; absolute temperature is indicated.
6. A steel box girder bridge corrosion fatigue life prediction method according to claim 1 or 3, wherein, The short crack growth time calculation model is that In the formula, Time representing short crack propagation phase; a critical length representing the transition from a short crack to a long crack; Indicating the critical length of the transition of the etch pit to the crack; A loading frequency representing fatigue load; Indicating the depth of the etch pit; An acceleration factor indicative of cyclic loading versus corrosion rate; representing the sensitivity coefficient of the stress amplitude to the corrosion acceleration factor; Representing a normalized stress amplitude; representing the corrosion current; representing a unit corrosion current; fatigue coefficients representing short cracks; Representing a range of stress intensity factors; indicating fatigue index of the short crack.
7. The method for predicting corrosion fatigue life of steel box girder bridge according to claim 1 or 4, wherein, The long crack growth time calculation model is that In the formula, Time indicating long crack propagation phase; indicating the critical length at which a long crack propagates to failure; a critical length representing the transition from a short crack to a long crack; A loading frequency representing fatigue load; Indicating the depth of the etch pit; An acceleration factor indicative of cyclic loading versus corrosion rate; representing the sensitivity coefficient of the stress amplitude to the corrosion acceleration factor; Representing a normalized stress amplitude; representing the corrosion current; representing a unit corrosion current; Fatigue coefficients representing long cracks; Representing a range of stress intensity factors; indicating fatigue index of long cracks.
8. The steel box girder bridge corrosion fatigue life prediction system comprises a storage unit and an operation unit, wherein the storage unit stores a steel box girder bridge corrosion fatigue life prediction program, and the steel box girder bridge corrosion fatigue life prediction program is operated by the operation unit to execute the steps in the steel box girder bridge corrosion fatigue life prediction method according to any one of claims 1 to 7.

Description

Method and system for predicting corrosion fatigue life of steel box girder bridge Technical Field The invention relates to the technical field of steel structure bridge life prediction, in particular to a method and a system for predicting corrosion fatigue life of a steel box girder bridge. Background The steel box girder bridge (simply referred to as a steel bridge) is widely applied to severe corrosion environments such as cross sea and river because of the advantages of light weight, high strength, convenient construction and the like. However, steel bridges exposed to the ocean atmosphere for a long time are easy to generate corrosion fatigue damage under the coupling action of chloride ion corrosion, acid rain corrosion and circulating traffic load, the service life is obviously shortened, and even catastrophic accidents (such as bridge collapse caused by stress corrosion of a boom of a Yibin small south gate Jinshajiang bridge) are caused. The corrosion fatigue of the steel bridge is a complex process of mutual promotion of electrochemical corrosion and mechanical fatigue, namely, a corrosion medium breaks a passivation film on the surface of steel to induce pitting corrosion, a corrosion pit causes stress concentration to accelerate the initiation of fatigue cracks, and the propagation of the fatigue cracks also provides a penetration channel for the corrosion medium, especially the local corrosion is aggravated at the crack tip, so that corrosion products are accumulated and electrochemical reaction is enhanced, the strength of the crack tip is further weakened, a vicious circle of corrosion and fatigue interaction acceleration is formed, and the structural fatigue life is greatly shortened. At present, the fatigue life evaluation of the steel bridge mainly adopts an S-N curve method, a fracture mechanics method or a probability evaluation method based on a reliability theory. The fracture mechanics method can predict the crack propagation life, but usually assumes the existence of initial cracks, and ignores the contribution of the corrosion pits to the total life from no to some initiation stages. More importantly, the existing models generally fail to explicitly introduce the corrosive environment in a measurable electrochemical parameter during the crack propagation stage, and it is difficult to effectively quantify the corrosion-fatigue coupling effect. Although studies have been conducted to investigate corrosion fatigue behavior through experimentation or numerical modeling, no unified calculation theory has been developed that covers the entire process of "etch pit initiation-short crack propagation-long crack propagation". The existing bridge design specifications do not consider the corrosion-fatigue coupling effect, so that the fatigue life is overestimated, and the service safety of the structure is insufficient. Therefore, it is highly desirable to combine electrochemical corrosion and fracture mechanics theory and establish a method for predicting the corrosion fatigue life of a steel bridge by considering the pit initiation and crack propagation stages. Disclosure of Invention The invention aims to provide a method for predicting corrosion fatigue life of a steel box girder bridge, which aims to solve the problem that the synergy of corrosion and fatigue (namely corrosion-fatigue coupling effect) is difficult to quantify in the prior art. In order to achieve the purpose, the invention uses the electrochemical parameter which can be measured, namely the corrosion current, as the key input quantity for representing the corrosion environment intensity, and couples the key input quantity with the mechanical parameter to construct a corrosion fatigue life prediction model for covering the whole process of pit initiation, short crack propagation and long crack propagation, thereby improving the applicability and prediction precision of the corrosion fatigue life prediction method under different corrosion environments. Specifically, the invention adopts the following technical scheme: a method for predicting corrosion fatigue life of a steel box girder bridge comprises the following steps: s1, establishing a calculation model of pit sprouting time considering a cyclic load acceleration effect; s2, establishing a short crack propagation time calculation model, wherein the model represents the corrosion environment intensity based on the actually measured corrosion current and couples the influence of the stress level, the initial length of the short crack is the critical length (namely the initial crack length) of the transition from the corrosion pit to the crack, and the termination length is the critical length of the transition from the short crack to the long crack; S3, establishing a long crack extension time calculation model, wherein the model represents corrosion environment intensity based on actually measured corrosion current and couples the influence of stress level, wherein t