Safety assessment for capacity design of bolted steel connections in tension

Capacity design for bolted connections in tension means that yielding of the gross cross-section is decisive over the ultimate resistance of the net cross-section. If the requirement for capacity design is met, ductile connection behavior is achieved, and brittle failure is avoided. However, in many practical cases the bolt holes are too large to satisfy the current capacity design requirement of EN 1993-1-1. In this capacity design requirement, both failure criteria involved, plastic resistance of the gross cross-section and ultimate resistance of the net cross-section, are considered independently with their own partial factors. This may be overly conservative. The goal of the research is to determine an improved capacity design requirement such that bigger bolt holes can be allowed without hampering safety. Both partial factors and the factor 0,9 in the net cross-section resistance are combined in one factor. With the use of a Monte Carlo simulation a new capacity design requirement with its own combined factor is developed. Several distributions for dimensions and steel properties are used as input for the Monte Carlo simulation. The correlation between the yield stress and the ultimate strength is considered as well. In the Monte Carlo simulation, also a model factor is used. The current combined factor for the capacity design requirement is 1.39. Based on the research performed, it can be concluded that this is very conservative and that the value of the combined factor can be lowered to 1.05.