Cold Pad has developed an innovative solution alternative to welding or bolting that relies on the use of adhesive bonding to connect mechanical fasteners to existing steel structures. This allows avoiding heavy on-site operations and is particularly well adapted to applications requiring cold working. In addition, such a process prevents from local steel material fragilization, residual stresses creation, or geometrical stress concentration that may decrease the structure's life expectancy. There is however a legitimate concern regarding the durability of structural adhesive bonding that needs to be studied. The presented investigations were carried out on one particular aspect of durability: the creep behavior of such connections. For the considered applications (constant load), it may indeed be one of the main issues that governs the connected fastener mechanical capacity.

In order to be able to investigate the creep behavior of the developed solution, both experimental and numerical investigations were carried out. The experimental investigations will first be described. Those were led on real scale assembly, at different stress levels, and under different load situations. The fastener may indeed be submitted by either predominant tension load, or shear load. The investigations allowed obtaining failure modes, repeatability, time to failure data, but also, local displacements evolution with time. The results revealed a non-linear evolution of those displacements closed to a Burger law. This model was thus chosen for the numerical modelling that will be presented in the second part. The law implementation will first be described, and the numerical results will be compared to the obtained experimental measurements. In addition, the evolution of the internal stress state inside the adhesive layer will be described and discussed.

The experimental investigations are still ongoing with different parameters that may affect the creep behavior of the adhesive. In addition, the modelling strategy is still under development in order to be able to describe the whole creep process and to better describe the assembly behavior.