From Benchmarked Beam Solver to Practical S-Lay Overbend Tool: An LLM-Assisted FEA Programming Case Study

Abstract

This paper presents an application-level case study in which an existing benchmarked nonlinear beam finite-element solver is adapted into a practical S-lay overbend analysis program for offshore pipelines and subsea inline components, using a large language model (LLM) as the main programming and software-structuring assistant. The mathematical development of the nonlinear beam solver and of its plasticity extension was completed in earlier work and is not revisited. The present study addresses the next engineering problem: how a validated solver kernel is converted into a usable domain-specific analysis tool by implementing geometry preparation, roller contact, lay tension, staged loading, component passage sweeps, result extraction, validation ledgers, plotting and machine-learning dataset generation. The central argument is that once a finite-element formulation has been established and benchmarked, many subsequent engineering software tasks become physics-implementation problems rather than new mathematical derivations. In such tasks a domain expert can specify the physical meaning of the model, the acceptance criteria and the benchmark comparisons, while an LLM performs most of the implementation, refactoring, documentation and regression-test generation. The case study is S-lay overbend analysis of plain pipe, thickened pipe components, offset shrouds and externally attached pipeline-mounted structures. The rebuilt program is compared against two published S-lay inline-structure studies over 57 published comparisons drawn from 50 published cases, every one produced by a single build of the program on a single date. The study shows that LLMs can substantially reduce the programming barrier for domain experts who need to customise validated numerical solvers into practical engineering tools. It also shows what that costs: of the five defects the benchmark campaign exposed, none was in the solver and none would have been found by a test the LLM could have written unprompted. The LLM can implement the engineering workflow; the domain expert must define and validate the physics.