Event Combination Analysis for Design and Rehabilitation of U.S. Army Corps ofEngineers Navigation Structures

摘要

Event combinations for design or evaluation of navigation structures should beevaluated probabilistically, and design criteria can be developed to be consistent with a level of performance expressed in probabilistic terms. (a) The probability of a joint occurrence of common loads at their peak values is very small. Thus, when considering what loads should be combined, a significant reduction in the combined load from the sum of nominal design values is appropriate. A principal action-companion action format for combining structural actions is recommended for maintaining uniform reliability. (b) The illustration of the event combination methodology indicated the following: (1) The probability of a coincidence of operating loads and earthquake is on the order of 1 x 10 to the -10th. (2) The probability of a coincidence of earthquake and impact is on the order of 1 x 10 to the -15th. (3) The probability of a coincidence of earthquake and flood is on the order of 1 x 10 to the -11th. It appears as if combinations of these events are very rare and would not need to be considered in design or evaluation. However, further study of these recommendations would be desirable. (c) Load combinations for dealing with accidental events should be based on a conditional probability of about 0.01-0.1 that the combined load effect is exceeded, given that an accident occurs. The overall unconditional probability of structural failure using this design approach is estimated to be on the order of 0.00001/yr or less. (d) Research should be undertaken to develop a protocol for combining extreme events in design of navigation facilities.