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The increasing demand on the performance of existing structures, together with their degradation, is among the main drivers towards the development of innovative strengthening solutions. While such solutions are generally aimed at increasing the load-bearing capacity of structural elements, serviceability limit states also play an important role in ensuring the performance and durability of the structure. An experimental campaign was performed to assess the cracking behaviour of reinforced concrete beams strengthened with different typologies of Textile-Reinforced Concrete. The specimens were monitored using Digital Image Correlation (DIC) technology in order to obtain a quantitative evaluation of the evolution of the crack pattern throughout the whole test. Results show the beneficial effects of this retrofitting strategy both at ultimate limit states and serviceability limit states, provide detailed insights on the progression of damage in the specimens and highlight how different parameters impact the cracking behaviour of the tested elements.

Austrian Federal Railways ÖBB, Austrian motorway operator ASFINAG Strengthening methods for shear-deficient bridges were developed and tested in cooperation with the HILTI Corporation and SIKA Austria. In order to identify the strengthening effect in shear, a number of 12 T-shaped RC-beams with a length of 5.38 m were designed. In the experimental campaign two different types of strengthening systems were applied and subjected to shear loading until failure. The successful use of a modern digital image correlation system provided the basis for an in-depth analysis of failure mode and crack pattern as well as shear degradation at each load stage. Finally, the applicability of existing shear design models with consideration of the strengthening elements analogously to cast-in shear reinforcement was evaluated.anchorage, carbon fiber, FRP, postinstalled, shear, shear test, strengthening, undercut anchor 1 | INTRODUCTION Subsequent strengthening of existing structures has gained in importance over the last decades due to the decreasing number of new structures and the ever-growing number of existing ones. The ongoing increase in traffic loads, continuous updating of design codes, and also paradigm shifts lead to the fact that a number of existing bridge structures do not fulfill the required safety level concerning the shearbearing capacity as required by codes of practice such as Eurocode 2. 1 Meanwhile, there exist refined methods for the verification of the shear load-bearing capacity 2-7 , developed from more consistent mechanical models. MC2010 8 provides advanced design approaches allowing for a better utilization of the real structural resistance. Nevertheless, the need for sound technical solutions in the subsequent shear strengthening of existing reinforced concrete (RC) structures is constantly increasing.While the flexural strengthening of RC members has become a routine task, the retrofitting of shear-deficient members is still a challenging issue for the following reasons:• Local shear retrofitting requires the introduction of forces over very short distances. In comparison, flexural strengthening is oriented in the longitudinal direction of a structural member and usually applied over larger sections. Therefore, adequate stiffness and proper anchorage solutions are needed when strengthening in shear. • The strengthening system must be reliably activated without the necessity of large additional live loads or deformations of the structure. • Currently, there are no harmonized recommendations for RC shear design itself available; therefore, the rather complex design of shear strengthening is even more disputable.A few established methods to strengthen RC structures in shear already exist (see e.g., overview in Reference 9). Selected popular methods for shear strengthening are discussed and compared on the basis of experimental investigations in Reference 10. With respect to the affected sections of a structure and the impact on the overall structural behavior, such strengthening solutions can generally be...

When producing a Textile Reinforced Concrete structure or element, joining separate textile layers might be a necessity, driven for example by the limited dimensions of commercially available fabrics. A possible way of producing such joints is by overlapping different textile sheets. Overlapped joints, however, need to be cast with particular attention since they might represents weak elements of the structure, leading to premature failure. An experimental campaign was performed, aimed at identifying the effects of a symmetric vs non-symmetric arrangement of the textile fabrics within the overlapping length and tensile characteristics of the matrix on such type of joints. Fifteen specimens, produced using a fully epoxy impregnated carbon textile fabric and an Ultra High Performance Concrete (UHPC) matrix, were tested under tension in a uniaxial setup and measurements were performed using a Digital Image Correlation system. The in-plane and out-of-plane behaviour of each specimen was studied. The results highlight the importance of producing symmetric elements as well as the beneficial effects that the admixture of short dispersed steel fibres to the cementitious matrix provide to such kind of joints