Experimental Evaluation of Tearout in Eccentrically Loaded Bolt Groups

The limit state of tearout can limit the strength of eccentrically loaded bolt groups. A common approach to design eccentrically loaded bolt groups is the instantaneous center of rotation (IC) method. This method has been validated against test results of specimens failing in bolt shear, bearing, or slip, where all the bolts in the group can be assumed to have the same strength. The bolts in an eccentrically loaded bolt group will have different strengths when tearout controls. Consequently, the applicability of the IC method for bolt groups experiencing tearout failure is uncertain. As a result, designers often make conservative assumptions regarding tearout, leading to inefficient designs. A modified version of the IC method that accounts for the limit state of tearout was proposed in previous research but lacks experimental validation. This thesis describes physical experiments on eccentrically loaded bolt groups with small edge distances where tearout occurs. Experiments were conducted on two series of bolted connections with varying eccentricities, bolt configurations and edge distances. The results provide unique data on the behavior of the eccentrically loaded bolt groups. The data was used to evaluate both current and proposed methods for designing the eccentrically loaded bolt groups. The findings indicate that neglecting tearout is unconservative, a common approach to consider tearout known as the poison bolt method is conservative, and the modified IC method is more accurate while still being conservative. With this experimental validation, the modified IC method will allow more accurate and design of the eccentrically loaded bolt groups with small edge distances.