Excessive load

Abstract

Sometimes structural loads are excessively high, and a decision must be made if intervention, either removal of the excess load or strengthening of the structure, is needed. This issue was addressed previously in the retrofitting literature. However, equations for excess load calculation were not presented. This article includes equations based on the full probabilistic reliability model for the failure probability of excessive load of three materials: steel, timber, and concrete. Failure probabilities are given as a function of the load designed for full capacity according to the Eurocodes. Safe excessive loads, i.e., loads with a failure probability less than 1/1500, are given, too. The load combination is a critical issue in this study. There are many options for load combination, which vary regarding the dependent vs. independent load combination, dependent vs. independent reliability calculation, the reference time, and the reference reliability. The conclusion is that the loads should be combined dependently, reliability should be calculated dependently, the reference time is 50 years, and the reliability is 50 years. We stress that the reliability of steel structures is questionably low in the current Eurocodes.