Seismic Integrity of High-Strain Cold Bend in Lateral Spreading Zone

Excellent workability of the stress-strain curve controlled high strain line pipe on cold bending with a bending angle of 10 degrees is presented. The high-strain line pipe has a round-house type s-s curve with the stress ratio σ2.0/σ1.0 of 1.030, where σ1.0 and σ2.0 are 1.0% and 2.0% yield stress, respectively. A standard yield-plateau type line pipe was also employed for comparison. FEA was conducted to investigate the cold bending behaviors of X65, 24″ line pipe. The longitudinal strain induced in the high-strain pipe at peak load and unloaded steps are small compared to those in the standard pipe.Effects of residual strain on local buckling behaviors of the high-strain cold bends are investigated. The effect of residual strain on the strain capacity of cold bend subjected to closing and opening mode bending is small when the cold bend is not pressurized. FEA tends to overestimate the strain capacity in bending when the bend is pressurized. However FEA well predicts the locations of the shell wrinkle of the pressurized bend subjected to opening mode bending when residual strain is taken into account. Seismic integrity of the 24″ high-strain cold bend in a lateral spreading zone is demonstrated.Copyright © 2014 by ASME