Concrete is one of the most commonly utilized building materials and has a significant en- vironmental footprint due to its production process. Over the past decades, considerable progress has been made in developing high-performance and ultra-high-performance concretes and incorporating fiber…
Concrete is one of the most commonly utilized building materials and has a significant en- vironmental footprint due to its production process. Over the past decades, considerable progress has been made in developing high-performance and ultra-high-performance concretes and incorporating fiber reinforcements in structural concrete, resulting in improved strength and durability, and opening the possibility of creating slenderer structures leading to significant material savings. However, ad- equate models and design approaches must accompany these material improvements to fully realize the potential benefits, especially considering the effects of the long-term sustained loads. This work focuses on material behavior aspect of plain and fiber-reinforced high-performance con- crete, investigating damageprocessesandmechanismsoccurringatsmallscales,whicharenotreadily observable during loading tests. To this end, it presents a framework for generating mesoscale con- crete models based on virtually created aggregate and fiber distributions [1] and Computational To- mography(CT)images. Afinite element model utilizing zero-thickness interface elements is applied to simulate the fracture of concrete specimens on the laboratory scale. The zero-thickness interface elements are equipped with a cohesive-frictional traction-separation law a model for hysteresis oc- curring due to incomplete crack closure during loading-unloading cycles [2]. The steel fibers are considered explicitly and modeled as elastoplastic Timoshenko beam elements. The 3D elastoplastic constitutive law with isotropic is adapted for beam elements by iterative solution of zero stress con- straints via Newton’s method [3]. The embedment of fibers into the cement matrix is facilitated via a penalty-based frictional tying algorithm that enables flexible placement of fibers without needing to conform with the background mesh. The bond between the cement matrix and fibers is modeled via an elastoplastic bond-slip law proposed in [4], whose parameters are calibrated based on single-fiber pullout experiments. All model components are implemented into the open-source Finite Element program “Kratos Multi-physics” [5]. The capabilities of the proposed model are demonstrated by re- analyzingseveralexperimentalscenarios, suchasnotchedprismaticspecimensunderuniaxialtension [6] and comparing results with the available experimental data.