本文關鍵詞：斜拉索腐蝕損傷與安全性能評定方法研究　出處：《重慶交通大學》2014年碩士論文　論文類型：學位論文

  更多相關文章： 拉索損傷 腐蝕疲勞 銹蝕分級 圖像分析 破損安全評估

【摘要】：對于現(xiàn)代斜拉橋梁來說，拉索系統(tǒng)是其主要承重構件，舊有的斜拉橋結(jié)構在使用過程中由于不利作用，，受到應力和腐蝕等因素的影響，致使存在各種缺陷和損傷。大量事故表明，拉索的損傷通常會引起橋梁結(jié)構力學特性發(fā)生改變，進而影響到橋梁結(jié)構的安全性、耐久性以及使用壽命。故對損傷后的拉索進行安全性能評估尤為重要。 本文依托973計劃前期研究專項課題橋梁結(jié)構行為演化理論與安全監(jiān)測方法研究。本文首先介紹了拉索的損傷檢測評估及安全性能等方面的現(xiàn)狀，指出纜索氋強鋼絲破壞的主要形式是應力腐蝕及腐蝕疲勞破壞。對纜索高強鋼絲的無應力、靜態(tài)應力和交變應力三種受力方式進行酸性鹽霧試驗，研究受點蝕、應力腐蝕及腐蝕疲勞損傷后的拉索的損傷演化過程及安全性能。 ①根據(jù)三種損傷狀態(tài)，對鍍鋅鋼絲進行酸性鹽霧腐蝕試驗，把鋼絲損傷的過程描述為5個階段：鋼絲完好→鋼絲鍍鋅層銹蝕、鋼絲基質(zhì)均勻銹蝕→鋼絲基質(zhì)輕微點蝕→鋼絲基質(zhì)大量坑蝕→鋼絲發(fā)生應力腐蝕和腐蝕疲勞，并制定Ⅴ級腐蝕對應的腐蝕圖例。對各級鋼絲圖像進行灰度分析，提出一種基于表層圖像分析銹蝕拉索技術狀況的評定方法。根據(jù)鹽霧腐蝕試驗及拉伸試驗數(shù)據(jù)，選取數(shù)據(jù)相關性較好的腐蝕失重、抗拉強度及斷后伸長率為特征參量，給出各級鋼絲的級評定標準。 ②建立了半球形的點蝕坑模型，計算了不同失重下的蝕坑深度，給出了點蝕坑腐蝕速率的計算公式。根據(jù)實驗條件為參數(shù)，計算鋼絲材料的斷裂韌性KIC=117.6MPa m，通過斷裂韌性求得應力腐蝕強度因子閾值KISCC=46.8。最后根據(jù)損傷力學理論提出應力腐蝕損傷演化模型。根據(jù)應力強度因子準則，計算了當應力比R=0時的腐蝕疲勞裂紋擴展閾值K th3.64。 ③引入了等效裂紋深度的概念，根據(jù)等效裂紋深度計算等效應力強度因子。將鋼絲裂紋的三維模型巧妙的轉(zhuǎn)化為平面應變問題，采用直線外推法，用有限元軟件ANSYS模擬不同蝕坑深度下裂紋尖端的應力強度因子值。并與理論計算值相比較。提出基于斷裂韌性的剩余強度的計算方法，最后根據(jù)破損安全理論，給出腐蝕疲勞損傷的破損安全設計，并給出單根鋼絲進行安全破損的評估流程。 ④采用有限元模擬不同銹蝕程度下單根鋼絲和整根拉索的銹蝕模型。結(jié)果表明：蝕坑深度越大，深坑底部應力集中系數(shù)越大。把整根拉索的銹蝕分為5級來模擬不同銹蝕程度對拉索應力的影響，最大等效應力出現(xiàn)在最外層鋼絲之間的接觸區(qū)域；隨著腐蝕等級的提高，腐蝕拉索截面的應力整體提高。
[Abstract]:For the modern cable-stayed bridge, the cable system is the main load-bearing components, cable-stayed bridge structure of the old in use because of adverse effects, by the influence of stress corrosion and other factors, resulting in various defects and damage. Many accidents show that the cable damage often causes the bridge structure mechanical properties change, and affect the bridge safety, durability and service life. So the safety performance evaluation of cable injury is particularly important.
The research on evolution theory and safety monitoring method based on the 973 research program of special subject of bridge structure behavior. This paper introduces the present situation of the cable damage detection and evaluation of safety performance and other aspects, and points out that the main form of cable Meng strong steel wire breakage is stress corrosion and corrosion fatigue damage. The stress free cable of high-strength steel. Static stress and alternating stress three stress modes of acid salt spray test of pitting corrosion, stress corrosion and corrosion fatigue damage after the cable damage evolution process and safety performance.
According to the three kinds of damage state, acid salt spray corrosion test of galvanized steel wire, steel wire damage process is described as 5 stages: wire intact, galvanized layer of steel wire corrosion, steel wire, steel wire matrix matrix of uniform corrosion, mild pitting corrosion, large steel wire matrix occurred stress corrosion and corrosion fatigue, corrosion legend and make the V-grade corrosion. Corresponding gray image analysis for all levels of steel put forward a kind of evaluation method, surface image analysis technology based on cable corrosion condition. According to the salt spray corrosion test and tensile test data, select the better correlation of corrosion data loss, tensile strength and elongation parameters are given steel grade evaluation standard.
It has established a model of hemispherical pits, pit depth was calculated under different weight loss, gives the calculation formula of pitting corrosion rate. According to the experimental conditions for the parameter calculation of steel material fracture toughness of KIC=117.6MPa m, the fracture toughness obtained stress corrosion strength due to sub threshold KISCC=46.8. based on the theory of damage mechanics is put forward stress corrosion damage evolution model. According to the stress intensity factor criterion is calculated when the stress ratio of corrosion fatigue crack propagation threshold K th3.64. R=0
The concept of the equivalent crack depth, crack depth according to the equivalent calculation of equivalent stress intensity factor. The 3D model of wire crack transformation skillfully as a problem of plane strain, using linear extrapolation method, using finite element software ANSYS to simulate the stress intensity factor of the crack tip under different corrosion pit depth. And the calculated values are compared with the the theory. Put forward the calculation method of residual strength fracture toughness based, according to the failure safety theory, failure safety design gives corrosion fatigue damage, and gives a single wire breakage safety assessment process.
The corrosion model of single wire and the whole cable finite element simulation of different corrosion levels. The results showed that the greater the depth of corrosion pit, pit bottom stress concentration coefficient is big. The whole cable corrosion is divided into 5 levels to simulate the effects of different degrees of corrosion on the cable stress, contact area of maximum von Mises force appears in between the outermost layer of steel wire; with the increasing level of corrosion, stress corrosion of cable section of the overall improvement.

【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U448.27;U443.38

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