Fatigue crack arrest in steel beams using FRP composites

Seyed Mahdi Hosseini,Jakob Melchior,Mohammadreza Izadi,Elyas Ghafoori

doi:10.1016/j.engfailanal.2021.105397

Seyed Mahdi Hosseini, Jakob Melchior + Show 2 more

Open Access

https://doi.org/10.1016/j.engfailanal.2021.105397

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Abstract

Previous studies have demonstrated the effectiveness of strengthening with pre-stressed carbon-fiber reinforced polymer (CFRP) composites to increase the lifetime of cracked steel members. In some cases, complete crack arrest has been observed. This study aims to present a method that can estimate the minimum required prestressing that would result in a complete crack arrest in steel I-beams. Analytical and numerical models based on linear elastic fracture mechanics (LEFM) were developed and verified using a set of experimental results. Three steel I-beams with different crack lengths were strengthened with pre-stressed CFRP composites and later tested under a high-cycle fatigue loading regime. It was shown that the pre-stressed CFRP composites could result in a crack closure mechanism, in which the crack surfaces remained closed even under large external loads. Furthermore, it was shown that by considering the stiffness of the CFRP in the analytical formulation, the amount of prestressing required to arrest the fatigue crack growth can be reduced.

Highlights

Aging is becoming a worldwide concern for existing steel bridges
Discussion on specimen B1 B1 is the specimen with a short crack of 3 mm from the tip of the notch and is strengthened with a carbon-fiber reinforced polymer (CFRP) pre-stressed to 10% of the ultimate tensile stress
Discussion on specimen B2 B2 was the specimen with a medium length crack of 20 mm from the tip of the notch and was strengthened with a CFRP pre-stressed to 20% of the ultimate tensile stress

Summary

Introduction

Aging is becoming a worldwide concern for existing steel bridges. Approximately 22% of the bridges in Europe are made of steel, and they are prone to aging-related problems such as fatigue cracking and require constant inspections and repairs [1]. The damage is so advanced that the entire structure needs to be replaced This often requires a huge financial investment and may lead to traffic congestion; a repair seems to be a profitable alternative whenever possible [2,3,4]. Among the CFRPstrengthening techniques (with bonded and un-bonded anchorages), the most efficient solution has been achieved by pre-stressing the CFRP composites [7,9,10].

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Discussion

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