Steel bridges with orthotropic roadway decks are a common construction method for long-span bridges. The construction method was developed in the 1960s, and the early structures especially show increasing crack damage. On the one hand this is due to construction errors; on the other hand it is due to massively increased traffic loads. There is already a demand for rehabilitation methods that do not weaken the cross-section such as bolted solutions or exert thermal influence such as welding seams, but there are no reliable and economical alternatives so far. Here, rehabilitation methods with bonded steel patches using structural, cold-curing epoxy resin or polyurethane adhesives seem to be the method of choice, for which solutions are being developed in a German research project. Extensive results on adhesive selection and mechanical properties as well as on surface treatment with regard to the manufacturing process are presented here. Analytical calculations are used to identify the main factors determining the load-bearing behavior of bonded steel patches. The calculations were validated by means of extensive small-scale and component tests on four different notch details as well as with the aid of numerical calculations, which are, however, presented in a separate publication. However, in addition to bridge construction, this type of patch rehabilitation is also of interest to other branches of the steel construction industry, such as offshore structures, crane construction, or rail vehicles. The promising results are currently being continued and transferred to a follow-up project.