Assessment of different methods for characterization and simulation of post-cracking behavior of self-compacting steel fiber reinforced concrete

The post-cracking tensile properties of steel fiber reinforced concrete (SFRC) is one of the most important aspects that should be considered in design of SFRC structural members. The parameters that describe the post-cracking behavior of SFRC in tension are often derived using indirect methods combined with inverse analysis techniques applied to the results obtained from three- or four-point prism bending tests or from determinate round panel tests. However, there is still some uncertainty regarding the most reliable methodology for evaluating the post-cracking behavior of SFRC. In the present study a steel fiber reinforced self-compacting concrete (SFRSCC) was developed and its post-cracking behavior was investigated through an extensive experimental program composed of small determinate round panel and prism bending tests. Based on the results obtained from this experimental program, the constitutive tensile laws of the developed SFRSCC were obtained indirectly using two numerical approaches, as well as three available analytical approaches based on standards for estimating the stress versus crack width relationship (). The predictive performance of both the numerical and analytical approaches employed for estimating the relationship of the SFRSCC was assessed. The numerical simulations have provided a good prediction of the post-cracking behavior of the concrete. All the analytical formulations also demonstrated an acceptable accuracy for design purposes. Anyhow, among all the employed approaches, the one that considers the results of small determinate round panel tests (rather than that of prism bending tests) has predicted more accurately the constitutive tensile laws of the SFRSCCFEDER funds through the Operational Programme for Competitiveness and Internationalization - COMPETE and by national funds through FCT (Portuguese Foundation for Science and Technology) within the scope of the project InOlicTower, POCI-01-0145-FEDER520 016905 (PTDC/ECM-EST/2635/2014)

Comparing test methods for the mechanical characterization of fiber reinforced concrete

Different tests are proposed by international standards for the evaluation of the mechanical properties of fiber reinforced concrete (FRC); among them, either beams or round determinate panels are generally used. However, different tests are accepted by design codes if reliable correlation factors between standard parameters are provided (fib Model Code 2010). Within this context, a broad experimental program on both beams and round determinate panels was carried out in order to provide a critical discussion on material characterization and to evaluate possible correlation factors. Beam tests according to European (EN 14651), American (ASTM 1609), and Japanese (JCI-SF4) standard, as well as small round panels and large round panels (according to ASTM 1550) were studied within an experimental program comprising 189 beams and 90 round panels. Unlike previous researches, mainly focused on steel fibers, two types of macro-synthetic fibers were considered. Based on these experimental results, a comparison between test methods is presented, along with correlation approaches are proposed and critically discussed

Lattice discrete particle modeling of fiber reinforced concrete: Experiments and simulations

Naturally accounting for material heterogeneity, the Lattice Discrete Particle Model (LDPM) is a meso-scale model developed recently to simulate the meso-structure of quasi-brittle materials by a three-dimensional (3D) assemblage of polyhedral particles. A meso-scale constitutive law governs the interaction between adjacent particles and simulates various features of the meso-scale response, including cohesive fracturing, strain softening in tension, strain hardening in compression and material compaction due to pore collapse. LDPM has been extensively calibrated/validated, showing superior capabilities in predicting qualitative and quantitative behavior of concrete. As a natural extension for this discrete model to include the effect of dispersed fibers as discrete entities within the meso-structure, LDPM-F incorporates this effect by modeling individual fibers, randomly placed within the volume according to a given fiber volume fraction. In this investigation, the theoretical basis for LDPM-F is reviewed, and to calibrate/validate the numerical model, an extensive experimental study has been conducted to investigate the mechanical properties of various prismatic specimens containing different types (steel and synthetic) and dosages of fibers. Excellent predictive capability of LDPM-F is demonstrated through a rigorous calibration/validation procedure