Effective Topology of Bolted Connections for Detecting Damage Using Guided Wave Ultrasonics

AbstractStructures will eventually develop defects due to aging or overloading, which negatively affect the load-bearing capacity. In certain design details, defects are hidden and difficult to inspect with conventional inspection methods. It is important to introduce damage detection concepts into the earliest stage of structural design. Bolted connections in steel structures form the weakest link due to the risk of stress concentration, stress corrosion cracking, or galvanic corrosion between the connected elements, which cannot be seen visually. In conventional practice, bolts are placed based on the minimum and maximum spacing requirements guided by the American Institute of Steel Construction. In this paper, the periodic placement of bolts instead of irregular distribution was studied as improving the detectability of defects using guided wave ultrasonics. The periodic arrangement of bolts led to a unique frequency response that was utilized in the evaluation of connections based on the hypothesis that the periodic response was influenced by the presence of cracks or section loss. The frequency response curves depending on the bolt layout and topology were obtained numerically. The vibration mode influenced by the presence of defects was identified. The numerical results were validated with the scaled experiments. It was shown that the spatial distribution of bolts assists the damage detection ability, which can be considered as a design criterion of bolt distribution.