TY - JOUR

T1 - Strengthening of Steel Connections in a 92-Year-Old Railway Bridge Using Prestressed CFRP Rods: Multiaxial Fatigue Design Criterion

AU - Heydarinouri, Hossein

AU - Nussbaumer, Alain

AU - Motavalli, Masoud

AU - Ghafoori, Elyas

N1 - Funding information: The authors acknowledge the Innosuisse Swiss Innovation Agency (Grant ID: 19240.1 PFIW-IW) for funding this research project. The authors also acknowledge the financial and technical support from the project partners, namely, S&P Clever Reinforcement Company AG, Switzerland; the Swiss Federal Railways (SBB) AG, Bern; and dsp Ingenieure + Planer AG Engineering Office, Uster, Switzerland.Special thanks go to Slavko Tudor, Giovanni Saragoni, Dimitri Ott, and Robert Widmann from the Structural Engineering Research Laboratory of Empa (Dübendorf, Switzerland), Martin Hüppi from S&P AG, Herbert Friedl, André von Aarburg, and Lukas Bodenmann from SBB, Ann Schumacher from dsp AG, and finally, Reinhard Bischoff, Jonas Meyer, and Khash-Erdene Jalsan from Decentlab GmbH (Dübendorf, Switzerland) for their support and help in this project.

PY - 2021/6

Y1 - 2021/6

N2 - This paper presented a new retrofit system for strengthening the stringer-to-floor-beam double-angle connections in a 92-year-old riveted railway bridge in Switzerland, using prestressed carbon fiber-reinforced polymer (CFRP) rods. The strengthening system transmitted the forces purely through friction, with minimum interference with bridge traffic. The system consisted of two components: a newly developed mechanical wedge-barrel anchor to hold the prestressed CFRP rod and a clamping system attaching the stringer flange. The strengthening system reduced the out-of-plane deformation of the connections, resulting in a reduction in the distortion-induced stresses in the connections. The short-term bridge measurements showed that the application of a total prestressing force of 100 kN reduced the dominant mean stress in the connection hotspot by 47% (from 22.9 to 10.9 MPa) under the passage of passenger trains, whereas the stress range remained unchanged. Using the modified Wöhler curve method (MWCM) as a critical plane-based multiaxial fatigue model, the strengthening system was observed to reduce the multiaxial mean stress parameter by 30% under the passenger train loads. The long-term monitoring of the strengthening system, using a wireless sensor network (WSN) system, indicated no prestress loss in the CFRP rods during the seven-month period since its installation.

AB - This paper presented a new retrofit system for strengthening the stringer-to-floor-beam double-angle connections in a 92-year-old riveted railway bridge in Switzerland, using prestressed carbon fiber-reinforced polymer (CFRP) rods. The strengthening system transmitted the forces purely through friction, with minimum interference with bridge traffic. The system consisted of two components: a newly developed mechanical wedge-barrel anchor to hold the prestressed CFRP rod and a clamping system attaching the stringer flange. The strengthening system reduced the out-of-plane deformation of the connections, resulting in a reduction in the distortion-induced stresses in the connections. The short-term bridge measurements showed that the application of a total prestressing force of 100 kN reduced the dominant mean stress in the connection hotspot by 47% (from 22.9 to 10.9 MPa) under the passage of passenger trains, whereas the stress range remained unchanged. Using the modified Wöhler curve method (MWCM) as a critical plane-based multiaxial fatigue model, the strengthening system was observed to reduce the multiaxial mean stress parameter by 30% under the passenger train loads. The long-term monitoring of the strengthening system, using a wireless sensor network (WSN) system, indicated no prestress loss in the CFRP rods during the seven-month period since its installation.

KW - Carbon fiber-reinforced polymer rod

KW - Multiaxial fatigue

KW - Post-tensioning

KW - Strengthening bridge connections

KW - Wedge-barrel anchor

UR - http://www.scopus.com/inward/record.url?scp=85102870361&partnerID=8YFLogxK

U2 - 10.1061/(ASCE)BE.1943-5592.0001714

DO - 10.1061/(ASCE)BE.1943-5592.0001714

M3 - Article

VL - 26

JO - Journal of bridge engineering

JF - Journal of bridge engineering

SN - 1084-0702

IS - 6

M1 - 04021023

ER -