As the response of structures to impact loads has gained considerable interest during the last few years, it is an attractive challenge to develop thin TRC composites for the strengthening of structural elements subjected to such loads. The energy absorption and failure mechanisms of thin TRC composites depend primarily on the bonding mechanisms between the textile reinforcement and the fine-grained concrete matrix as well as on the interactions between filaments within individual fiber rovings. In TRC-strengthened concrete structures, the interfacial bond between TRC and reinforced concrete should also be modeled properly. Due to these complex mechanisms, existing models for conventional reinforced concrete, fiber reinforced concrete, and other fibrous composites are not directly applicable to thin TRC composites.

Furthermore, the high strain rate effects of impact loads complicate the damage and failure mechanisms, and may call for micromechanics-based models which are capable of reflecting the heterogeneous nature of TRC composites. A thorough analysis of structural components with complex mechanisms and dynamic effects is bound to require large computational efforts. Therefore, a reasonable multi-scale modeling approach is required to reduce those computational requirements as well as to understand the fundamental behavior characteristics and mechanisms of TRC composites, and to arrive at appropriate mathematical models to simulate the dynamic response of structures reinforced with such thin composites.

In order to develop such multi-scale model of TRC-strengthened structures considering high strain rates, different damage mechanisms and strain rate effects should be considered at each modeling scale. A fiber roving consists of a number of filaments, which can be divided into core and sleeve filaments. Since the sleeve filaments are stressed more than the core ones due to the partial impregnation of the roving with cement, a micro-scale model should include the interaction between the filaments as well as the strain-rate dependent fiber behavior. In the meso-scale modeling, the damage of a quasi-brittle material such as TRC composite is generally governed by two mechanisms, which are the interfacial debonding between fiber rovings and fine-grained cement matrix and the subsequent crack evolution. Thus, the meso-scale model can simulate both the mechanisms of the interfacial fiber debonding and crack growth. With an appropriate meso-scale model, the effective material properties of TRC composites can be obtained within the framework of micromechanics and fracture mechanics. Regarding macro-scale applications, the interfacial behavior between conventional reinforced concrete panels and thin TRC sheets under impact loadings is of particular interest. Therefore, an interface debonding model of TRC-strengthened reinforced concrete should be developed, which is capable of simulating energy absorption/dissipation and failure mechanisms.

Figure 1: Multi-scale Modeling of TRC-strengthened structure