Low cycle fatigue life prediction using a four-bolt extended unstiffened end plate moment connection

The end plate moment connection (EPMC) has been studied using various design concepts. However, after the Northridge, California earthquake in 1994, low cycle fatigue (LCF) analysis became the focus of investigation for EPMCs because the existing design code could not explain the brittle steel moment frame connection failures that occurred in numerous structures as a result of that earthquake. This paper provides a LCF life estimation procedure using a four-bolt extended unstiffened EPMC. In this research, four full-scale experimental tests are conducted to develop the LCF model and to estimate the LCF life of each connection. The experimental test failure mode is LCF fracture in the end plate. The LCF model is developed from three constant peak displacement cyclic load test results, and results from a fourth (and last) test performed with random cyclic loading. From these test results, the life of the structure is predicted using the LCF model. Finite element model (FEM) analysis and theoretical calculations (verified in the companion paper, Preanalysis of the Low Cycle Fatigue Behavior of a Reduced End Plate Moment Connection (T-stub) [1]) are used to predict the structural behavior. The results show reasonable relationships to each other.