Truss-type maintenance devices and corresponding pipeline lifting control strategies

For new submarine pipeline maintenance lifting equipment, a specialized analysis model is constructed in this study. A pipeline can be divided into the lifted portion and the touch-down portion that lies on the seabed, and each of these portions can be analyzed separately by converting the continuity conditions at the touch-down points to boundary conditions. The typical two-point sequence secant iterative technique is used to obtain the unknown lifted length and determine pipeline lifting configurations. The BVP4C module in MATLAB software is used to solve this multiple-point boundary value problem issued from first-order differential equations. Also, the triple-point lifting mode of truncated maintenance and the two-point lifting mode of online maintenance are discussed. When the lifted heights at truss positions are shown, the lifting deformation, lifting forces, bending moment distribution, and axial force distribution can be analyzed using a dedicated analysis program. Numerical results can then be used to design a lifting strategy to protect the pipeline.