Size Effect Hidden in Excessive Dead Load Factor

Abstract

The paper shows that the excessive value of the dead load factor in the ultimate load requirements of the current structural design code implies a size effect. The size effect implied, however, does not have a rational form; it cannot distinguish among various types of failure in which very different size effects apply. This size effect partly compensates for the absence of the actual size effect, primarily the size effect due to energy release, from the current code specifications. Therefore, it would be dangerous to reduce the dead load factor without simultaneously introducing size effect provisions into the code. The question of a possible reduction in the dead load factor cannot be separated from the question of size effect, and so the fracture experts and reliability experts must collaborate. Further it is shown that a possible size effect is hidden in a reliability-based code due to the fact that the reliability implied in the code increases with the contribution of the dead load effect to the overall gravity load effect. The overreliability ratio defined in this study may be used to quantify the additional size effect that can be hidden in a reliability-based code.