Ultimate bending strength of sandwich pipes with actual interlayer behavior

Sandwich pipe (SP), composed of two concentrically steel tubes with a strain-hardening cementitious composite (SHCC) filling core, is a new concept designed for oil and gas transportation in deep waters. Bending is a primary loading condition for the SP during the installation process. There is currently a lack of research on SPs' bending capacity, considering the actual interlayer behavior. The extreme adhesion conditions of fully bounded and unbounded layers have been commonly adopted in numerical simulations. This paper aims to study the actual interlayer behavior through push-out and self-stress tests and proposes an SP numerical model with a bond-slip layer, based on the finite element method. The results from experimental tests for bending on a rigid surface to simulate the reeling installation method are correlated with the results from the finite element model, presenting good agreement. A parametric study is then performed to investigate the influence of geometric parameters and the interlayer bond behavior on the ultimate bending strength. •Push-out and self-stress tests to study the actual interlayer behavior of sandwich pipes are presented.•A numerical model with a bond-slip layer for sandwich pipe is proposed.•Full-scale sandwich pipes bending tests are presented.•A correlation study between the experimental and numerical results is performed.•Influence of geometric parameters and initial ovality on the ultimate bending moments of sandwich pipe are analyzed.