臺灣博碩士論文加值系統

箱型梁橋為國內常見之鋼橋型式為了解鋼箱型梁橋常見細部之疲勞特性，本研究首先利用SAP2000對國內一座既有橋梁鋼箱型梁橋進行活載重數值模擬，並將模擬結果與規範比較。接著，依據日常車流下之現地應力量測數據針對翼板對接銲道、拉力側腹板豎向加勁板端部銲趾處及腹板縱向加勁板端部等不同等級之疲勞細部進行疲勞壽命評估。此外，亦利用ANSYS針對腹板縱向加勁板進行局部應力數值模擬，探討長度、寬度及厚度等幾何條件對縱向加勁板端部應力集中係數之影響。
利用數值模擬進行活載重橫向分佈研究結果顯示，數值模擬與採用現行AASHTO LRFD鋼箱外梁活載重分佈係數之差異為107%、55.3%、36.8%；若將鋼箱梁轉換為兩支等效之I型梁進行數值模擬與AASHTO LRFD I型外梁活載重分佈係數的差異為39%、15.9%、12.2%。表示以極限設計法設計活載重分佈係數時，採用數值模擬較保守。
疲勞壽命評估結果中顯示，拉力側翼板對接銲道、拉力側腹板豎向加勁板端部銲趾及腹板縱向加勁板端部此三處中，僅腹板縱向加勁板端部有較明顯的應力集中現象，且三處細部評估結果皆屬於「無限疲勞壽命」，表示在無裂縫發生時，並無疲勞疑慮。
腹板縱向加勁板端部數值模擬結果顯示，腹板縱向加勁板之長、寬、厚等幾何因子中，影響應力集中係數最顯著者為加勁板長度，接著依序為厚度及寬度。此外，數值模型之網格劃分採用固定網格尺寸的方式得到之分析結果較採用在加勁板厚度方向固定網格數量更接近規範對於縱向加勁板端部疲勞等級之定義。

關鍵字:鋼橋、疲勞、應力集中

The box girder bridge is a common type of steel bridge in Taiwan. To realize fatigue characteristics of details in steel box girder bridges, the on-site stress measurement under normal traffic and finite element analysis are carried out in this study. First, SAP2000 numerical bridge model for understanding the lateral distribution of live load is established, and the result of simulation is compared with code. Second, according to on-site stress measurement data, the evaluate of fatigue life in butt weld of flange, weld toe of web transverse stiffener and end of longitudinal stiffener are also studied in this research. In addition, we investigate the impact of longitudinal stiffener geometry such as length, width and thickness on the stress concentration factor with ANSYS finite element model.
The research result of the live load distribution factor using numerical simulation show that difference between numerical simulation and AASHTO LRFD live load distribution factor is 107%, 55.3%, 36.8%. If the steel box girder is convert into two equivalent I beam for numerical simulation and compare to the ASHTO LRFD live load distribution factor of the I beam, the difference is 39%, 15.9%, 12.2%. It mean that when designing live load distribution factor with AASHTO LRFD, the use of numerical simulation is more conservative.
The fatigue life evaluation result indicates that among butt weld of flange, weld toe of web transverse stiffener and end of longitudinal stiffener, the stress concentration has only more obvious in the weld toe of cross beam stiffener. However, these three places all are evaluated as Infinite Remaining Life, which means that has no immediate danger, and only needs regular inspection in the follow-up.
The simulation result of ANSYS model reveals that the length of longitudinal stiffener has the most significant influence on stress concentration factor compared with thickness and width. Furthermore, the simulation result of the numerical model's using fixed size of mesh than fixed amount of mesh close specification.

Keywords: Steel bridge, Fatigue, Stress concentration

摘要 I
Abstract II
致謝 IV
目錄 V
圖目錄 VII
表目錄 X
第一章、前言 1
1.1研究動機與目的 1
1.2研究方法及內容 3
第二章、活載重橫向分佈 4
2.1橋梁設計規範回顧 4
2.2橋梁基本資料 7
2.3數值模擬 8
2.3.1分析模型之建立 8
2.3.2箱型梁橋分析模型之驗證 12
2.4活載重橫向分佈係數比較 14
第三章、鋼橋疲勞壽命評估 25
3.1鋼橋疲勞細部分類 25
3.2疲勞評估規範 30
3.3鋼橋疲勞壽命評估 34
3.4數值分析 57
3.4.1網格劃分對應力集中係數之影響 59
3.4.2加勁板幾何形狀對應力集中係數之影響 72
3.4.3主要構件厚度隊應力集中係數之影響 87
第四章、結論與建議 96
參考文獻 98
附錄A 99
附錄B 104
 

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