Novel Approaches in Constitutive Modelling and Serviceability Analysis of Reinforced Concrete Structures: Strain Compliance Crack Model

The respective key-note presentation will highlight the results recently obtained by the research group on predicting the serviceability behaviour of RC members. The presentation will consist of three main parts: 1) A new bond-slip model. 2) A new deflection model for concrete bending members reinforced with steel or FRP bars and steel fibres. 3) A novel crack model termed the Strain Compliance Crack (SCC) model. The current paper will be limited to the description of the latter crack model. It accounts for the specifics of primary and secondary crack spacing and width analyses in RC beams, as demonstrated by testing. The reinforcement strain profile is used to predict crack spacing, which is the primary emphasis of the model. The model includes a novel concept of the limit effective depth, d_lim, to classify crack types. For small beams (d ≤ d_lim), only primary bending cracks are examined, whereas secondary cracks are addressed for large beams (d > d_lim). Parameter d_lim is influenced by the reinforcement ratio, modular ratio, cover, and bar diameter. Although the model may estimate the mean spacing between primary and secondary cracks, only primary cracks are used for calculating crack width. For small beams, the crack width profile is a straight line. It is presumed that the width profile of major cracks in large beams is bilinear (including fish-shaped). The proposed model accurately predicted crack spacing and width, which corresponded with experimental findings.