Strengthening of steel bridge components with externally bonded ultra-high modulus CFRP

Abstract

The application of the externally bonded (EB) carbon fiber reinforced polymer (CFRP) technique for retrofitting civil infrastructure has been increasingly gaining acceptance and market share. However, investigations on the performance of steel components strengthened or rehabilitated with EB CFRP are rather limited and most of the studies have been dedicated to concrete structures retrofitted with EB CFRP. In recent years, new research opportunities have opened with the emergence of ultra-high modulus (UHM) CFRP to evaluate the performance of UHM CFRP retrofitting technique in steel structural elements. The performance of the retrofitted steel elements is highly influenced by the bond between CFRP and steel interface. Indeed, debonding failure can lead to premature failure of the CFRP retrofitting technique. In this regard, the study of the bond behavior of the CFRP/steel joints is of paramount importance. This study aims to fully understand the behavior of steel components rehabilitated with CFRP and thereby highlighting the influential parameters. To that end, a comprehensive literature review is initially carried out to identify the key parameters that influence the bond behavior of the CFRP/steel interface, and thereby the flexural behavior of the retrofitted elements. In the second phase, a thorough experimental investigation is conducted to fill the existing gaps in the literature. Firstly, a series of double strap CFRP/steel joints are tested under static loading to evaluate various parameters, including the adhesive type, CFRP length, and surface preparation. Additionally, the effect of CFRP elastic modulus on the rehabilitation technique is examined by comparing Normal Modulus (NM) and Ultra-High Modulus (UHM) CFRP with approximately the same tensile capacity. Secondly, the flexural behavior of the CFRP rehabilitated notched steel beams are examined under static loading. The parameters considered in this phase include CFRP type, CFRP configuration, notch depth, anchorage system, and adhesive type. The results reveal that the effect of adhesive type plays a crucial role on the bond behavior of CFRP/steel joints. However, when it comes to the anchored rehabilitated beams, the adhesive impact is negligible on the flexural performance of the beams due to the anchorage mechanisms. The effect of surface preparation type has also been found trivial on the bond behavior of the CFRP/steel joints. Moreover, it is found that UHM CFRP has a shorter effective bond length compared to its NM CFRP counterpart and it generally outperforms NM CFRP in terms of load-carrying capacity.

Date	21 Nov 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Omar Chaallal (Supervisor)