Experimental and numerical investigation on transverse impact resistance behaviour of pipe-in-pipe submarine pipelines after service time

Abstract

The transverse impact resistance behaviour of pipe-in-pipe submarine pipelines after 15 years of service is studied experimentally and numerically. From drop hammer impact tests of 4 full-scale specimens, the influence of specimens’ span, corrosion and dent defect on the transverse impact resistance is studied in terms of failure mode, impact force-time history curves, displacement-time history curves, strain-time history curves and impact force-displacement curves. The experimental results indicate that the dynamic failure process consists of four stages, including primary vibration stage, secondary vibration stage, stable stage and unloading stage. As the suspension span of the specimen increases, the primary failure mode changes from local indentation to global bending deformation. The corrosion and the dent defect impair the impact resistance. Finite element (FE) models are then established and verified through comparison with experimental results. Numerical analyses indicate that the total impact energy is mainly dissipated by the outer pipe and the inner pipe according to the energy dissipation analysis for each component of the pipe-in-pipe specimens under transverse impact load. Parametric study is implemented finally to disclose the influence of the dimensions of pre-existing corrosion and dent defect on the transverse impact behavior of pipe-in-pipe submarine pipelines.