Shear fatigue of prestressed I-beams with shear reinforcement

TECHNICAL PAPER Shear fatigue of prestressed I-beams with shear reinforcement Matthias Hillebrand 1 | Frederik Teworte 2 | Josef Hegger 1 1 RWTH Aachen University/Institute of Structural Concrete, Aachen, Germany 2 H+P Ingenieure GmbH, Aachen, Germany Correspondence Matthias Hillebrand, RWTH Aachen University/Institute of Structural Concrete, Mies-van-der-Rohe-Str. 1, 52074 Aachen, Germany. Email: [email protected] Funding information Hessian State Office for Road and Traffic Affairs; German Research Foundation, Grant/Award Numbers: HE 2637/25-1, HE 2637/12-1 Abstract In the last decades, increasing traffic loads have led to higher requirements on the bearing capacity of existing and also new bridges. In particular, many bridge structures built in the 1960s and 1970s often contain less web reinforcement than the nowadays required minimum web reinforcement. In this context, the shear resistance under cyclic loading is of special interest. For this reason, experimental tests were conducted on prestressed concrete beams with and without shear reinforcement at the Institute of Structural Concrete of RWTH Aachen University within the last years to investigate the shear fatigue strength. The specimens were able to resist more load cycles than predicted by the approaches implemented in the Eurocodes for bridges. Based on the test results, design models for shear under cyclic loading should be reviewed and improved, especially with regard to the assessment of existing structures. This paper describes the recent tests on 20 I-shaped prestressed beams with web reinforcement. KEYWORDS bridges, experimental investigations, fatigue, prestressed concrete, reinforced concrete, shear reinforcement, stirrup 1 | INTRODUCTION Bridges are an important part of the German federal highway system. The requirements on bridge structures have increased significantly in the recent years due to higher traffic volume, especially concerning heavy load traffic. 1–4 A large number of bridges were designed and built in the 1960s and 1970s for lower load classes. 5 In addition, the calculated static shear load capacity was reduced in the course of further development of the design standards 6,7 accounting for more durability and robustness. Therefore, many German bridges exhibit a deficit in shear strength applying the current standards (e.g. Eurocode 2 8–11 ) because of the lower required shear reinforcement of previous design rules. 6,12 The verification of shear resistance under cyclic loading has been required for concrete bridges in Germany since 2003 by introducing the DIN Fachbericht 102, 7 which is based on Eurocode 2. 13 Hence, a guideline to assess the load bearing capacity of existing bridges 14,15 was introduced and has been continuously refined, for example, in Reference 16–22. The second amendment is already in progress. 23 The key element of this assessment guideline is a step- wise verification procedure, which is similar to the level-of-approximation approach of fib Model Code Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors’ closure, if any, approximately nine months after the print publication. Received: 28 March 2020 Revised: 29 June 2020 Accepted: 25 July 2020 DOI: 10.1002/suco.202000187 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2020 The Authors. Structural Concrete published by John Wiley & Sons Ltd on behalf of International Federation for Structural Concrete Structural Concrete. 2020;1–15. wileyonlinelibrary.com/journal/suco 1