Abstract
Stringer-to-floor beam web-to-web double-angle connections are among the most fatigue-prone elements in old riveted bridges. These connections are often designed to carry only shear loads. However, in these elements, fatigue damage occurs because of the out-of-plane deformation of the connections, which is ignored in the original design. In this study, a new retrofitting system is developed to reduce the out-of-plane deformation of the connections using prestressed carbon fiber-reinforced polymer (CFRP) rods. The proposed system consists of a mechanical wedge-barrel anchor to hold the prestressed CFRP rod and a clamping system to attach to the parent structure and to transmit forces via friction. A series of finite-element (FE) simulations was conducted to optimize the size and performance of the retrofit system. Laboratory static pull-off tests were conducted and different failure modes were studied and discussed. A novel test setup (with four supports) was designed for testing the steel connections. The effect of the geometrical imperfections during the installation of the connection was carefully investigated using the FE models and was verified through laboratory the tests. Laboratory fatigue tests were conducted on steel connections with the same dimensions as those in a railway bridge. The designed retrofit system was found to be capable of reducing the stresses at the angle connections by more than 40%. The results of the fatigue tests demonstrated that the designed system could survive more than load cycles without any fatigue damage or any indication of a loss in the CFRP prestressing level.
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Data Availability Statement
Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.
Acknowledgments
This work has been funded primarily by the Innosuisse Swiss Innovation Agency (Grant ID 19240.1 PFIW-IW). The authors would also like to acknowledge the financial and technical support from S&P Clever Reinforcement Company AG, Switzerland; the Swiss Federal Railways (SBB) AG, Bern; and dsp Ingenieure + Planer AG Engineering Office, Uster, Switzerland, for this project. They also thank the technicians from the Structural Engineering Research Laboratory of Empa for their outstanding collaborations during the experiments. Finally, the scientific and technical support from Dr. Ardalan Hosseini, postdoctoral scholar at the University of California, Davis, in different stages of the design of the strengthening system is highly appreciated.
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Published In
Journal of Structural Engineering
Volume 147 • Issue 3 • March 2021
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© 2020 American Society of Civil Engineers.
History
Received: May 6, 2020
Accepted: Sep 18, 2020
Published online: Dec 23, 2020
Published in print: Mar 1, 2021
Discussion open until: May 23, 2021
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