Fatigue life estimation of tubular joints – a comparative study

Abstract

In fatigue analysis, the structural detail of tubular joint has taken great attention among engineers. The DNV/GL‐RP‐0005 is covering this topic quite well for simple and clear joint cases. For complex joint and geometry, where joint classification is not available and there is limitation on validity range of non‐dimensional geometric parameters, the challenges become a fact among engineers. The classification of joint is an important factor to consider in fatigue analysis. These joint configurations are identified by the connectivity and the load distribution of tubular joints. To overcome these problems to some extent, this paper compares the fatigue life of tubular joints in offshore jacket according to the stress concentration factors (SCF) in DNV/GL‐RP‐0005 and finite element method employed in Abaqus/CAE. The paper presents the geometric details, material properties and load history of the considered jacket structure. It then describes the global structural analysis and identification of critical tubular joints for fatigue life estimation. Hence, fatigue life is determined based on the guidelines provided in design codes. Fatigue analysis of tubular joints is conducted using the finite element employed in Abaqus/CAE as the next major step. Finally, predicted SCFs and fatigue lives are compared, and these observations tend to conclude that even though the fatigue life, which is calculated based on code given SCFs, provides more realistic prediction to the simple uniplanar joints, there is a doubt for complex joints and geometry, where joint classification is not available. Also, the study emphasized that it is very important to preciously investigate SCFs by considering accurate geometry of complex tubular joints for a good judgement of fatigue life.

Determination of stress concentration factors in offshore wind welded structures through a hybrid experimental and numerical approach

“…(Christiansen and Tang, 2016) have employed neural networks for tubular joint optimization in offshore jacket structures where influence factors (INF) and SCFs were applied to simplified models of relevant tubular joints in global models in order to achieve a realistic force flow in the structure. (Maheswaran and Siriwardane, 2016) have presented a comparative study of the fatigue life of tubular joints in offshore jackets according to the SCFs in DNV/GL-RP-0005 and FEA modelling. (Yang et al, 2015) studied SCFs of negative large eccentricity tubular Njoints under axial compressive loading in vertical brace through a combination of experiments and FEA simulations.…”

A numerical framework for determination of stress concentration factor distributions in tubular joints

“…The addition of the weld geometry to the finite element model results in a 10.2% decrease of the maximal SCF at the weld toe on the chord for IPB. Although the overall influence observed in this case study is limited, other researchers report larger discrepancies [23,39]. For example, Lozano-Minguez et al [23] studied the effects of the weld geometry on the SCFs at the crown and saddle…”

Analisis Hotspot Stress Pada Sambungan Tubular Brace T Dengan Simulasi Pembebanan Tarik Pada Struktur Bangunan Lepas Pantai Tipe Jacket Platform.

“…Kerusakan akibat kelelahan telah menjadi salah satu sebab yang paling umum dari kegagalan yang terjadi pada tubular joint struktur lepas pantai [9]. kelelahan merupakan fenomena penting yang menyebabkan kegagalan kerusakan di sekitar las pada sambungan [10] dimana kelelahan sering terjadi di daerah persimpangan brace struktur lepas pantai yang disebabkan adanya pembebanan siklik oleh gelombang dan angin [11]. Analisis fatigue pada anjungan lepas pantai secara umum merupakan suatu prosedur perhitungan yang dimulai dengan analisis gaya gelombang yang menimbulkan range tegangan pada wilayah hot-spot dan diakhiri dengan estimasi kerusakan akibat fatigue [12] A. Sambungan Tubular Sambungan tubular merupakan bagian dari bracing jacket platform dengan bagian utama disebut chord dan bagian cabang disebut brace, keduanya dihubungkan dengan sambungan yang dikenal dengan tubular joint.…”