Fatigue behavior of orthotropic bridge decks with two types of cutout geometry based on field monitoring and FEM analysis

• Published in: Engineering structures Vol. 209; p. 109926
• Main Authors: Zhu, Zhiwen, Xiang, Ze, Li, Jianpeng, Huang, Yan, Ruan, Shipeng
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.04.2020; Elsevier BV
• Subjects: Box girder bridges; Bridge decks; Diaphragms; Fabrication; Fatigue cracks; Fatigue life; Fatigue strength; Field tests; Finite element method; Finite-element analysis; Floorbeam cutout; Geometry; Girder bridges; Mathematical models; Monitoring; Orthotropic bridges; Orthotropic steel deck; Plane stress; Random traffic flows; Retrofitting; Rib-to-floorbeam weld connection; Steel bridge; Steel bridges; Stress concentration; Stress measurement; Suspension bridges; Fatigue life; Steel bridge; Finite-element analysis; Orthotropic steel deck; Field tests; Random traffic flows; Floorbeam cutout; Rib-to-floorbeam weld connection
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2019.109926

•Fatigue behavior on two types of cutout in two closely spaced floorbeams is first studied via field monitoring.•A large radius curve can increase the stress level at the floorbeam cutout.•In-plane stress dominates the total stress at the floorbeam cutout.•Fatigue category at the floorbeam cutout need to be reduced for poor fabrication.•Floorbeam thickness should be increased for the bridge under overloaded traffic. This paper provides comparative results on stress behavior and fatigue performance of two types of cutout geometry on orthotropic bridge decks based on simultaneous field monitoring and finite-element method (FEM) analysis. The two types of cutout are incorporated in two closely spaced diaphragms with distance of 6 m and at the same transverse location on a real bridge, allowing simultaneous stress measurement under random traffic flows. The research was conducted on the Pingsheng Bridge in Southern China, a self-anchored suspension bridge with a main span of 350 m and a steel box girder with orthotropic steel bridge decks (OSBD). Results of the study reveal that the two types of cutout geometry present high stress response and severe stress concentration at the floorbeam (FB) cutout, and that the excessively large stress at the original FB cutout contributes greatly to the early cracks of this detail. Compared to the original cutout geometry, the new cutout geometry with large radius increases the stress level at the FB cutout, resulting in a further low fatigue life at this detail. Meanwhile, the new cutout geometry also deteriorates the fatigue resistance at the rib-to-floorbeam (RF) weld connection, particularly at the detail of rib wall at cutout, where the stress level is significantly increased and its fatigue life becomes substantially lower than the design life of 100 years. In addition, the new cutout geometry only slightly improves the out-of-plane distortion under direct wheel loading, and the in-plane stress still dominates the total stress at the FB cutout. Since the new cutout geometry weakens the FB web, the total stress at FB cutout will increase due to the increased in-plane stress. The research also finds that if the free edge of cutout did not satisfy the fabrication requirement per the AASHTO LRFD, category B is suggested for fatigue evaluation at the FB cutout, which is confirmed by the observed fatigue life of the original FB cutout on the real bridge. It is concluded that the new cutout geometry lowers the fatigue resistance both at the FB cutout and at the RF weld connection, hence it will no longer be recommended to retrofit the present bridge in the future.