Tubular joints are widely used in offshore and other tubular steel structures because of their efficient load-carrying behavior and suitability for demanding environments. Their strength and resistance are evaluated using dedicated design standards, with the applicable requirements depending on the project and design basis.
In SDC Verifier, tubular connection checks are available according to API RP 2A-LRFD (1st, 1993), ISO 19902 Connections (1st, 2007), and NORSOK N-004 Connections (Rev. 3, 2013).
This article describes the procedure of calculation according to the joint standards and explains the engineering logic behind tubular joint verification and the practical sequence for performing the checks. For all general FEA programs (Ansys, Simcenter 3D, Femap) the calculation procedure for a joint check is the same, so SDC Verifier provides a solution for all of these software solutions.
For the complete software workflow, the current implementation is covered in the ISO 19902 Connections Tutorial for SDC Verifier 2026 R1, including Connection Finder setup, connection classification, standard inputs, utilization tables, and criteria plots.
General requirements and nomenclature
A simple uniplanar tubular joint in SDC Verifier is represented by the following connection:
The following terminology is used:
Joint – a node where two or more inclined elements are connected;
Connection – a set of elements of the same plane around a joint node (or multiple joints in case of tiny mesh);
Chord – a set of non-welded elements that form a straight line (usually with a higher diameter);
Brace – a welded to a chord element;
For tubular joint verification, the connection geometry and the role of each brace must be established before the code check is evaluated. In particular, the recognized geometry must fall within the scope of the selected connection standard.
Each tubular brace should be classified according to the loading and connection joint geometry:
K – force is balanced between other braces of the connection from the same side of the chord;
T&Y – a force of the brace is acting as a shear force in a chord;
Cross – force is balanced between the braces from the other side of the chord.
Brace classification can be a mixture of the three types above.
This classification is important because the applicable resistance equations and factors depend on the way loads are transferred through the connection. In the ISO 19902 workflow, for example, Connection Finder Tool identifies the supported chord and brace configuration and the calculation uses the resulting connection geometry and loading information.
Tubular braces are checked on axial, in-plane and out-of-plane bending loads as other types of brace loading (torsion and shear) do not cause bending in a chord wall.
SDC Verifier solution for Tubular Joint Check
A tubular joint check starts with the FEA model and follows a defined engineering sequence:
Recognize the connection.
Verify the geometry and brace classification.
Define the standard and its required inputs.
Evaluate the governing utilization factors.
Review critical connections and load cases.
Document the results in tables, plots, and reports.
SDC Verifier supports this workflow by automatically recognizing supported connection geometry and extracting the chord and brace parameters required by the selected standard. For ISO 19902 Connections, Connection Finder identifies supported tubular connections and provides the geometry needed for the subsequent check.
Connection Finder is a broader recognition tool and can identify different types of structural components and geometries. However, recognition alone does not mean that every detected connection is eligible for the specific ISO 19902 tubular-joint verification. The recognized geometry must satisfy the requirements and validity range of the selected standard.
For the ISO 19902 implementation, the standard defines validity ranges for parameters such as β, γ, connection angle, τ, material strength, and gap conditions. These parameters should therefore be reviewed after recognition and before relying on the calculated utilization factors.
Load Input
Instead of describing all the load sets directly in the FEA software, SDC Verifier speeds up the calculation process by using base load cases (or individual loads) directly and combines these in load sets (linear combination of these base cases) and uses load groups to get the worst situation of all the load cases in 1 picture! Hereby all requiredload scenariosprescribed by the standard can be easily considered without extra efforts.
For a tubular joint assessment, the goal is not simply to calculate one utilization factor for one load case. The relevant load scenarios should be included so that the governing combination for each connection and brace can be identified.
In the following example a jacket model will be used loaded with wind and wave at 0°, 45°, 90° and 135° to the global X direction and the following load combinations:
Since the structure is symmetric and the area under the loading is equal in opposite directions, the results of the initial wind/wave loads can be transformed using the opposite factor -1 (e.g. combinations from 180° to 315°).
All loads sets are combined into 1 single load group.
Connections overview
After the FEA model and load scenarios are prepared, Connection Finder can be used to recognize the tubular connections in the model. The recognition results provide a connection table where the engineer can review the detected joints, chords, braces, and relevant geometric information.
The recognized connection should be reviewed before running the final check. This is where the engineer confirms that the chord and brace arrangement corresponds to the intended physical connection and that the connection falls within the scope of the selected standard.
The 2026 R1 workflow also provides a chord/brace preview, making it easier to inspect an individual connection and verify the geometry identified by the recognition tool.
Follow the ISO 19902 Connections tutorial for the complete SDC Verifier 2026 R1 workflow, including Connection Finder setup, standard inputs, utilization tables, and criteria plots.
Results of Joint Check
As an example, a joint check according to ISO 19902 is going to be shown. Besides, the joints members of the offshore structures should also be checked. See how SDC Verifier checks member strength on axial, bending, shear and hydrostatic loading according to ISO 19902
The dedicated ISO 19902 Connections implementation in SDC Verifier verifies tubular joint strength according to Chapter 14 of the first edition of ISO 19902 (2007). It evaluates recognized chords and braces for axial force, in-plane bending, out-of-plane bending, and their interaction.
Before running the check, the engineer defines the standard inputs and verifies the applicable resistance settings. The 2026 R1 workflow includes settings for the partial resistance factors used in the connection calculations.
Once the check is calculated, SDC Verifier presents the resulting utilization factors in a dedicated table. The table can be used to identify connections and braces with the highest utilization and therefore prioritize the engineering review.
The governing utilization should be evaluated together with the corresponding connection, brace, load case or load group, and calculation parameters. A high utilization factor identifies a critical result, but the engineer should still review the geometry, classification, loading, and applicable standard criteria before making a design decision.
For the load different from the load group, it is possible to see all the calculation parameters used for calculations of utilization factors and also plot original and projected axial forces, gap/overlap sizes, and brace classification with labels for selected connections.
The connection visualization is particularly useful for checking how the applied forces are transferred through the joint. For ISO 19902, the calculation accounts for parameters such as gap, overlap, chord force effects, and connection classification when determining the joint resistance.
Criteria plots provide another way to review the calculated results directly on the model and connect the numerical utilization factors with the physical location and geometry of the connection.
After the critical connections are identified, the engineer can review governing results across the relevant load combinations and use the results for design decisions, further analysis, or reporting.
This makes the practical decision sequence straightforward: recognize the connection → verify its geometry and classification → define the standard inputs → evaluate utilization → review the critical connections → report the governing results.
Besides the tables, it is also possible to preview results on your FEM Model.
The results can also be included in a customized simulation report, allowing the calculation inputs, governing results, and relevant engineering information to be documented in a traceable format.
Conclusion
Tubular joint verification is more than calculating a utilization factor. A reliable assessment requires the connection to be correctly recognized, its geometry and brace classification to be verified, the appropriate standard inputs to be defined, and the governing results to be reviewed in the context of the relevant load scenarios.
SDC Verifier simplifies this process by connecting FEA results with automated tubular connection recognition and code-based joint checks. The current connection implementations include API RP 2A-LRFD (1st, 1993), ISO 19902 Connections (1st, 2007), and NORSOK N-004 Connections (Rev. 3, 2013).
