Today’s offshore wind turbine support structures market is largely dominated by steel structures, since steel monopiles account for the vast majority of installations in the last decade and new types of multi-leg steel structures have been developed in recent years. However, as wind turbines become bigger, and potential sites for offshore wind farms are located in ever deeper waters and ever further from the shore, the conditions for the design, transport, and installation of support structures are changing. In light of these facts, this paper identifies and categorizes the challenges and future trends related to the use of concrete for support structures of future offshore wind projects. To do so, recent advances and technologies still under development for both bottom-fixed and floating concrete support structures have been reviewed. It was found that these new developments meet the challenges associated with the use of concrete support structures, as they will allow the production costs to be lowered and transport and installation to be facilitated. New technologies for concrete support structures used at medium and great water depths are also being developed and are expected to become more common in future offshore wind installations. Therefore, the new developments identified in this paper show the likelihood of an increase in the use of concrete support structures in future offshore wind farms. These developments also indicate that the complexity of future support structures will increase due to the development of hybrid structures combining steel and concrete. These evolutions call for new knowledge and technical know-how in order to allow reliable structures to be built and risk-free offshore installation to be executed.

The quality of strain measurements using distributed fiber optic sensors (DFOS) depends largely on the bond between the host material and the optical fiber. Experimental investigations were carried out to test the suitability of five different DFOS types for crack monitoring. The DFOS were subsequently bonded to two 4 m long reinforced concrete (RC) beams, so that the influence of the application technique could be evaluated. DFOS measurements were verified by digital image correlation (DIC) and electrical strain gauges (SGs). For the different DFOS types, clear differences in the measured strain curves and determined crack widths were observed. The focus was on two robust DFOS, which can be deployed on construction sites. Compared to the layered sensing cable, a monolithic DFOS showed a clear strain distribution with pronounced strain peaks even for closely spaced cracks. The crack widths obtained by integrating the strain curves showed high agreement with DIC measurements.

The ability to measure strains quasi‐continuously with high spatial resolution makes distributed fiber optic sensing a promising technology for structural health monitoring as it allows to locate and measure damages in concrete structures, such as cracks. Depending on whether the distributed fiber optic sensor (DFOS) is embedded into the concrete matrix or bonded to the reinforcement, different approaches for crack width calculation exist. The high spatial resolution of DFOS quickly leads to a large amount of data, especially with time continuous monitoring. Scalable, automated analysis approaches are required to handle such big data and to derive a gain in knowledge from the measurements. Thus, in a first step, the Python framework fosanalysis is presented and made available to other researchers or monitoring specialists as free software. The most important input parameters for crack width calculation are discussed for concrete strain and steel strain DFOS. Accurate crack monitoring for a 4 m long reinforced concrete beam is demonstrated by using fosanalysis. The calculated crack widths are in good agreement with digital image correlation measurements.

The fatigue of concrete has been the subject of research for many years, and yet, there are still open questions. In particular, the fatigue‐induced damage evolution accompanied by a stress redistribution process propagating through the concrete structure is still not fully understood. So far, there are only few experimental studies addressing the fatigue propagation through a material zone occurring, for example, in beams with a pulsating, nonuniform stress profile. To investigate the influence of such stress configurations on the material and structural degradation process, a measuring concept has been developed combining digital image correlation, fiber optic sensors, and conventional strain gauges. The presented experiments visualize the propagating fatigue degradation in the compression zone of prestressed concrete beams subjected to fatigue loading. Based on the developed measurement concept, the quantitative foundation for a comprehensive validation of design rules and material models accounting for concrete fatigue can be significantly extended.