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Numerical modelling of bond behaviour of FRP bar reinforced concrete beam under high strain rate impact load

Heidarzadeh, G. (2022). Numerical modelling of bond behaviour of FRP bar reinforced concrete beam under high strain rate impact load. (Unpublished Doctoral thesis, City, University of London)


Since 1980s, the use of fibre-reinforced polymer (FRP) has been introduced as reinforcement or retrofitting measures to concrete structures. The FRP material features in high strength to weight ratio, high flexibility, ease of installation and energy absorption, higher corrosion resistance, made this material a viable option for strengthening RC members in high strain rate events such as impact and blast.

One of the most dominant failure modes in FRP reinforced concrete structures is the debonding failure, which happens near or at FRP interface to concrete. Extensive research has been made on the bond behaviour of FRP RC structures under static loading. However, the influence of high strain rate on bond behaviour of FRP reinforced concrete under dynamic load is still not well understood as limited studies are investigated on the influence of high velocity impact load on bond of FRP to concrete. In addition, the results do not represent the real bond behaviour of FRP to concrete as factors such as strain rate was not included in the investigations.

This thesis undertakes an exploration into the bond behaviour of reinforced concrete beams, specifically reinforced with Fiber Reinforced Polymer (FRP) bars, when subjected to high-velocity impact loads characterized by varying strain rates. Employing ABAQUS, a commercially available finite element software, a comprehensive three-dimensional finite element model was meticulously constructed. The reliability of this model was meticulously ascertained for both static and dynamic scenarios, with a particular focus on the local reinforcement strain distribution. The initial stage of this investigation involved a thorough analysis of variables influencing the bond between FRP and the concrete interface. These variables encompassed concrete compressive strength, bar diameter, the type of fibres utilized, and the variation in applied impact loads, which were collectively examined using a dataset of 255 distinct beam models. It was conclusively determined that both the diameter of the FRP bars and the strength of the concrete matrix exert a significant influence on the bond behaviour exhibited by FRP-reinforced concrete beams. Notably, this study unveiled a groundbreaking revelation, demonstrating that the strain rate directly impacts the bond mechanism governing the behaviour of beams subjected to impact loading.

Furthermore, this research effort culminated in the identification and reporting of optimized parameters for FRP bar diameter, concrete strength, and the type of fibre, all tailored to the specific requirements of reinforced concrete beams exposed to high-impact loading conditions. These findings represent a valuable contribution to the body of knowledge in the field of structural engineering and materials science.

In the subsequent phase of the study, an innovative multi-way regression analysis was undertaken, marking the first instance in which equations were derived through a parametric study to forecast slip, maximum bond strength, and mid-deflection in Fiber Reinforced Polymer (FRP) reinforced concrete beams. To assess the accuracy of these prognostic equations, validation was carried out through the creation of novel models.

This research effort yielded significant outcomes, notably the formulation of a concrete Dynamic Increase Factor (DIF) model, which exhibited a strain rate dependency. This development stemmed from an exhaustive numerical examination of bond slip behaviour between FRP bars and the adjacent concrete matrix under varying loading rates. Additionally, a dynamic slip rate-dependent model for FRP-reinforced concrete beams was introduced for the first time. The finite element predictions stemming from the bond-slip DIF model were accurately compared and corroborated against established guideline codes, founding their reliability and applicability in engineering practice.

Publication Type: Thesis (Doctoral)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Departments: School of Science & Technology > Engineering
School of Science & Technology > School of Science & Technology Doctoral Theses
Doctoral Theses
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