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Numerical Investigation of Crack Propagation in Slab-Bridge System Main Beams Subjected to Moving Loads

Morafegh, Fatemeh | 2023

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 56037 (53)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Jahanshahi, Mohsen; Khoei, Amir Reza
  7. Abstract:
  8. Bridges play a vital role in road-related transport industries. Significant changes to contemporary bridge design specifications have also been mainly related to strength issues. The transitions from allowable stress design to load factor design, and more recently to load and resistance factor design (LRFD), reflect this line of thinking. It is important to note that in the early 1970s, bridge engineers developed criteria for steel bridge details to protect against fatigue and fracture failure. These were indeed service life design provisions. By industry growth and extensive need for goods transportation, there is a need for the construction of new bridges and renewal of older bridges plus repair and maintenance of existing bridges. Over the past few decades, failure mechanics has undoubtedly prevented a significant number of structural failures. This study investigates the propagation of cracks due to fatigue of steel in slab-beam bridges, using sap2000 and Abaqus software. Meanwhile, the actual truck load has been modeled and the truck crossed the bridge twice. Also, to have better contact between the tires and the bridge, Hyperelastic behavior has been selected for tires. The results reveal that the most critical zone in these bridges is around the support. The crack will initiate in the bottom beam flange and the Von Mises contours show an 11% increase in maximum stresses in flanges after the crack initiation. Also crossing the truck load after the initiation of the crack would raise the stresses in the cracked area. The results show that using hyperelastic material for tires provides a better interaction between the wheel and the surface and the 3-ring tire with multiple-point load has better load transfer due to an increase in the contact surface. It makes the body force more realistic and is in good agreement with the static load stated in the Iranian regulations. The maximum stress is at the junction of the web and bottom flange and the crack is going through the flange with almost 20 degrees of inclination in the XFEM analysis. Meanwhile, the boundary condition of support affects the maximum stress in the beams significantly; hence, When the flange and pile cap are restrained in all direction and the web is free of movement or rotation, the maximum Von Mises stress after crack initiation is less than that of any other condition. In the j-integral analysis, the absolute maximum Von Mises stress around the crack reaches 506 MPa in j-integral analysis, which is higher than the Yield strength of steel. The results reveal that whenever a truck crossed the bridge twice, the crack will propagate in the first and third directions significantly
  9. Keywords:
  10. ABAQUS Software ; Crack Propagation ; Finite Element Method ; SAP 2000 Software ; Extended Finite Element Method ; J-Integral Method ; Slab-Girder Bridge ; Moving Loads

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