基于主S-N曲線法的典型鋼橋焊接節(jié)點疲勞壽命評估
發(fā)布時間:2019-01-01 16:20
【摘要】:鋼橋由于長期受到交通荷載和環(huán)境因素的綜合作用,承受大量不同應(yīng)力幅值的應(yīng)力循環(huán),容易導(dǎo)致疲勞損傷和破壞,而焊接節(jié)點的疲勞破壞是鋼橋斷裂失效的主要原因之一。因此,及時準確地進行鋼橋焊接節(jié)點疲勞壽命評估尤為重要。 名義應(yīng)力法是最簡單和最常用的鋼橋焊接構(gòu)件疲勞評估方法,普遍存在于各國及協(xié)會的鋼橋疲勞設(shè)計規(guī)范,如我國鋼結(jié)構(gòu)設(shè)計規(guī)范GB50017、英國規(guī)范BS5400、歐洲規(guī)范Eurocode3.美國國家公路與運輸協(xié)會(AASHTO)標準、國際焊接學(xué)會(ⅡW)標準等。然而,限于疲勞試驗數(shù)據(jù)的有限性,現(xiàn)有規(guī)范難以涵蓋所有焊接類型,導(dǎo)致疲勞壽命評估過程具有一定的主觀性。此外,由于名義應(yīng)力法沒有考慮焊接構(gòu)件的應(yīng)力集中效應(yīng),評估結(jié)果往往過于保守。研究者又提出了表面外推的熱點應(yīng)力法,熱點應(yīng)力法考慮了焊接部位的應(yīng)力集中,減少了選擇S-N曲線的難度,從而提高了焊接構(gòu)件的疲勞壽命評估精度。但是,大量的研究表明,在焊接構(gòu)件的有限元應(yīng)力分析過程中,基于表面外推確定的結(jié)構(gòu)熱點應(yīng)力表現(xiàn)出較大的網(wǎng)格敏感性。基于上述考慮,Dong根據(jù)基本的力學(xué)原理,結(jié)合熱點應(yīng)力法,并考慮應(yīng)力沿焊接構(gòu)件厚度方向分布特點,提出了一種網(wǎng)格不敏感的結(jié)構(gòu)應(yīng)力確定方法;诰W(wǎng)格不敏感的結(jié)構(gòu)應(yīng)力計算方法和斷裂力學(xué)理論,發(fā)展了主S-N曲線疲勞模型,并已成功應(yīng)用于海洋平臺管道、壓力容器等結(jié)構(gòu)的焊接節(jié)點疲勞壽命評估。主S-N曲線法綜合考慮了應(yīng)力集中、構(gòu)件厚度、荷載模式等的綜合作用,所有鋼結(jié)構(gòu)焊接構(gòu)件都適用于同一條主S-N曲線,有效解決了焊接構(gòu)件疲勞壽命評估現(xiàn)存的結(jié)構(gòu)熱點應(yīng)力確定隨機性和S-N曲線選擇受限性的問題。 本文基于主S-N曲線法,利用有限元分析軟件ANSYS,通過有限元分析及相應(yīng)的后處理,對典型的鋼橋焊接構(gòu)件進行疲勞壽命評估,對主S-N曲線法在鋼橋典型焊接構(gòu)件疲勞壽命評估中的適用性、單元類型選擇、單元尺寸的劃分、焊縫的模擬方法、計算精度等進行了比較分析研究。對在規(guī)范中分類不同、長度分別為200mm和60mn的縱向角接節(jié)點疲勞壽命評估過程中,著重研究了同一主S-N曲線對分類不同的兩個焊接節(jié)點的適用性,以及實體單元和殼單元兩種單元類型對疲勞評估結(jié)果的影響。利用主S-N曲線法對帶有開口肋的正交異性鋼橋面板焊接節(jié)點進行疲勞壽命評估時,對采用不同焊縫模擬方法的模型均劃分四種單元尺寸,研究重點在于不同的單元尺寸以及不同焊縫的模擬方法對疲勞評估結(jié)果的影響。 研究結(jié)果表明,結(jié)構(gòu)應(yīng)力的計算具有很好的網(wǎng)格不敏感性,后續(xù)的疲勞壽命評估結(jié)果也具有較穩(wěn)定的結(jié)果;同一條主S-N曲線可用于不同分類的鋼橋焊接節(jié)點的疲勞壽命評估:綜合考慮各有限元模擬方法的精度及可行性,運用主S-N曲線法對鋼橋焊接節(jié)點的疲勞壽命時,傾斜的殼單元模擬焊縫是一種較適合的模擬方法。
[Abstract]:Because of the comprehensive action of the traffic load and the environmental factors for a long time, the steel bridge can bear a large number of stress cycles with different stress amplitude values, which can lead to fatigue damage and damage, and the fatigue failure of the welding joints is one of the main causes of the failure of the steel bridge. Therefore, it is very important to evaluate the fatigue life of the steel bridge welding joints in a timely and accurate manner. The nominal stress method is the most simple and most commonly used steel bridge welding component fatigue assessment method, which is widely used in the steel bridge fatigue design specifications of countries and associations, such as the Code for Design of Steel Structures of China (GB50017), the British Standard BS5400, and the European Specification Eurocode. 3. American National Highway and Transportation Association (AASHTO) standard, International Welding Society (鈪,
本文編號:2397807
[Abstract]:Because of the comprehensive action of the traffic load and the environmental factors for a long time, the steel bridge can bear a large number of stress cycles with different stress amplitude values, which can lead to fatigue damage and damage, and the fatigue failure of the welding joints is one of the main causes of the failure of the steel bridge. Therefore, it is very important to evaluate the fatigue life of the steel bridge welding joints in a timely and accurate manner. The nominal stress method is the most simple and most commonly used steel bridge welding component fatigue assessment method, which is widely used in the steel bridge fatigue design specifications of countries and associations, such as the Code for Design of Steel Structures of China (GB50017), the British Standard BS5400, and the European Specification Eurocode. 3. American National Highway and Transportation Association (AASHTO) standard, International Welding Society (鈪,
本文編號:2397807
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