Effect of Non-uniform Thickness and Material Property on the Evaluation of Plastic Collapse Moment of Pipe Elbows

In this study, three-dimensional finite element analysis (FEA) was performed by inputting material properties and thicknesses measured at different locations in three commercial elbows, and the plastic collapse moment (PCM) was evaluated for each input condition. Notably, the plastic collapse moments varied by up to 39% and 42% with the input material properties and thickness, respectively. Furthermore, the variation in the PCM according to the input material property was larger in closing mode bending than in opening mode bending, but the variation with the input thickness was larger in closing mode bending than in opening mode bending. A comparison of the bending test and FEA results on elbow specimens showed that the plastic collapse behavior was appropriately predicted when the average of the material properties and thicknesses measured at extrados, intrados, and crown of the elbow were inputted. The use of the nominal thickness in the FEA conservatively predicted the plastic collapse behavior of the elbow.