Assessing the accuracy of the design code and empirical equations for predicting the shear capacity of FRP-reinforced concrete beams.

Abstract

Research on the use of Fibre Reinforced Polymers (FRP) in structural concrete elements has started several decades ago. Over the past few years, this research has further intensified due to the needs in the construction industry to shift to a more sustainable and durable construction material. Yet, a comprehensive understanding of the behaviour of FRP reinforced concrete structures is still far from complete due to the limited nature of their applicability and usage in general civil and structural engineering applications. While the emphasis over the past two decades has been made mainly on the flexural behaviour of FRPs reinforced concrete elements, in recent years, attention had shifted towards the investigation of the shear behaviour of FRP reinforced concrete elements, provided that shear failure may occur and if does occur, it is very brittle and hence dangerous. Attempts have been specifically made to gain an extensive and comprehensive understanding of the behaviour of structural members reinforced with different types of FRPs. Several design specifications have established a series of equations that can be used to predict the shear capacity of FRP reinforced concrete beams. To date, a number of studies have been done to verify the applicability and accuracy of these equations and guidelines for calculating the shear strength of FRP reinforced concrete beams. Normally this is done through the use of a regression analysis, by comparing the predicted shear capacity against experimental data of concrete beams reinforced with different types of FRPs. Certain modifications to the available design code equations are also available. The scope in the majority of the studies is quite limited, however. This dissertation aims to fill this gap and assess the existing design code and empirical equations in terms of their accuracy in predicting the shear capacity of beams reinforced with FRP bars with and without stirrups. A database was developed by gathering beam test data available in the literature. In the database, the beams were classified into deep and slender beams, and this was done to investigate whether the equations are influenced by the 𝑎/𝑑 factor, and to assess whether certain equations are valid for both beam types. Furthermore, this work investigates the relation between the accuracy of the equations and the different key factors incorporated in the equations. The work shows that although some factors could be crucial in determining the shear strength of FRP-reinforced beams, it remains difficult to justify the significance of each factor in determining the overall shear capacity, when incorporated into the design equations. From the work presented, the most accurate four equations for predicting the shear capacity of FRP reinforced deep and slender beams with and without stirrups are identified.