The topic of this project was the definition of a new effective repair and/or reinforcement method for large steel structures with defects. Two basic steel structural types were dealt with in the CO-PATCH project, namely marine structures (mainly ships) and steel civil engineering structures (e.g. bridges). Many of the major problems that these structures face during their operational life are common, with fatigue playing a predominant role among them.

Repeated loading is a very common loading condition for these structures. In areas of stress concentrations, this leads to the initiation and growth of fatigue cracks. If not detected and properly repaired in time, cracks can grow to critical lengths and result in structural failures. An additional structural problem of steel structures is corrosion. Corroded plating or corroded beams jeopardise the strength and stiffness of the structure. Measures are required to reinstate the original structural characteristics.

Besides repairing fatigue cracks and corrosion, there is often the need for upgrading the strength and/or the stiffness of a structure to enable new (higher) loading conditions or helping in mitigating initial design deficiencies.

Welding and replacement are the traditional ways to deal with these problems and to reinforce a structural part. However, there are circumstances when these repair or reinforcement approaches are either time-consuming and costly, or simply impossible to be followed. This obviates the need for investigating and assessing the effectiveness of new solutions that will help in overcoming currently existing problems.