Collapse performance of High Frequency Welded steel pipes for offshore applications: experiments and numerical simulations

Abstract The present paper investigates the collapse performance of steel pipes fabricated by the High Frequency Welding (HFW) method. Two 16-inch outer diameter HFW line pipe specimens are subjected to full-scale external pressure testing in order to determine their collapse pressure and propagation pressure. Prior to testing, one of the pipes has been externally coated, which introduced a mild heat treatment to the pipe, while the other pipe remained intact (non coated). The full-scale test procedure is modelled with a computationally efficient finite element methodology, which accounts for the actual geometry and material properties, and employs a simple and efficient technique for simulating pipe collapse and buckle propagation. The numerical results compare very well with the full-scale experimental results, in terms of the values of collapse and propagation pressure, the collapsed shape and history of local strains at critical locations. Both experimental and numerical results show a very good performance of HFW pipes against collapse, indicating that those pipes can be strong candidates for offshore applications. The analytical procedure for predicting the collapse and propagation pressure in DNV-ST-F101 is also evaluated and shows that its conservative predictions are improved if an appropriate value of fabrication factor is used.