Lateral Buckling Analysis in SIMLA – Zero-Radius Bend (ZRB) Triggers

Written by Martin Teigen.

This is a demonstration of Zero-Radius Bend (ZRB) triggers in the SIMLA finite element tool. I made this video as part of a case study I performed a few years back.

The finite element tool SIMLA is used in Norway, although I am using ABAQUS at the moment. When it comes to analysis of subsea pipelines, the underlying theory between the two tools are similar. Both are using pipe (beam) elements. The main difference is that SIMLA is specialised and limited to pipelines, whereas ABAQUS offers many element types and material models.

Similarly with ABAQUS, SIMLA takes input files. There is not GUI to prepare the model in SIMLA, however you can perform the post-processing in the Simvis module, which is demonstrated in the video below. Simvis also offers easy manipulation of the seabed, where you can simply click your way along the pipeline to fill in spans, or create trenches. It also contains a simplified FE-screening module with allows you to quickly calculate freespans based on the rectified seabed.

The video only demonstrates Simvis as a post-procesing tool for an analysis I performed in SIMLA. ZRB’s are commonly used in Australia, and they are based on a sleeper reducing the lateral resistance of the pipeline locally. There is also a vertical column around which the pipeline can be installed with a very small radius.

Similarly to RC, the advantage of the ZRB is high reliability because the critical buckling force is low. Differently from RC, the uncertainty represented by the pipe-soil interaction is avoided as the pipeline is lifted off the seabed. Also, ZRB’s may be superior for seabeds that are mobile. For example if the seabed features shifting sandwaves, the ZRB offers to lift the pipeline up from the seabed and thereby avoiding the high lateral resistances that may arise. The main disadvantage of the ZRB is the cost of manufacturing and installation. A single ZRB could easily cost 1 MUSD per unit. In comparison, the cost of a single sleeper on the seabed could be 0.2 – 0.5 MUSD.

I acquired the SIMLA license back in 2015 because I thought I could offer consultancy serviced having the tool at hand. That did not work, so I ended up performing many case studies, some of which turned into papers and material I have presented in various forums in the following years. SIMLA is about the same price as ABAQUS, but for a private person the cost is high, so I would not recommend renting these tools unless you have the job first. But little did I know back then, and if anything it did give me a lot of material that I have used in technical papers and also various presentations and webinars.