Reinforcement of Fatigue Damaged Steel Structures Using Adhesively Bonded CFRP Lamellas - Part 1: Basics and Materials

The condition grades published by the Federal Highway Research Institute, show a considerable need for rehabilitation of German road bridges. Steel bridges often show fatigue cracks at points of increased stress concentrations. Due to the high volume of traffic and the enormous importance of a well functioning infrastructure for the German economy, reconstruction is often not possible due to time restrictions. Therefore, effective and reliable methods of rehabilitation are required. The currently applied repair and reinforcement measures have significant disadvantages. A large number of these disadvantages can be avoided by means of an adhesive reinforcement, in which adhesively bonded CFRP lamellas are applied on the fatigue cracked steel structure. In the context of a research project the potential of bonded CFRP lamellas with or without pretension to increase the remaining service life is being investigated. Based on defined requirements, potential adhesives are preselected and characterized experimentally by means of short and long-term tests on modified thick tensile shear specimens. On the basis of quasi-static tests on CFRP steel overlap specimens, a calculation approach is verified to estimate the load carrying capacity and the minimum bond length for two selected adhesives. On the basis of the static tests, fatigue tests are carried out on the CFRP steel overlap joint and Wohler diagrams are derived which can serve as a basis for fatigue strength design.