J3 — Round 1 Review Tracker¶
Journal: Ocean Engineering. Round: R1 (first round of revision). Submission: 2026-03-17 (original); R1 resubmission drafted 2026-04. Deadline: 2026-05-06. Reviewers: 3.
See Papers / J3 for the scientific summary of the paper itself.
Progress¶
Next steps — nothing outstanding on the review itself. Remaining before R1 submission on 2026-05-06:
- Author sign-off on
cover_letter_R1.mdandresponse_to_editor_R1.docx. - Final full-manuscript read-through and language pass on
manuscript_v8.qmd. - Submission packet assembly: revised manuscript (clean + track-changes) + cover letter + response document + four new figure files.
- CrossRef DOI re-check on the seven new references and the upgraded ISFOG entry (already in progress as part of the shared J2+J3 validator sweep).
Editor summary¶
The decision letter requested revisions in response to three reviewers' comments. Reviewer 1 provided 9 specific comments on methodology, figures, and physics interpretation. Reviewer 2 gave 2 comments focused on transition-mechanism analysis and high-frequency content. Reviewer 3 contributed 7 comments on permeability scaling, stress-history effects, literature coverage, and generalisation. All were numbered and tracked.
Reviewer 1 — methodology, figures, physics interpretation¶
| ID | Paraphrased concern | Target location | Action taken | Status |
|---|---|---|---|---|
| R1.1 | \(S/D \le 0.6\) upper bound needs justification (monopile literature uses \(S/D\) up to 2). | §2.1 new paragraph | Explicit justification based on Gunsan-site bathymetric envelope + Jalbi (2018) tripod sensitivity ratio (tripods are ~ 5× less sensitive to scour than equivalent monopiles). | Closed |
| R1.2 | Schematic of scour-hole shape around the tripod bucket is needed. | §2.1 new fig-scour-geometry |
Two-panel figure: cross-section with 45° frustum side slope + plan view of bucket with scour annulus. Maximum \(S/D = 0.58\) annotated. | Closed |
| R1.3 | Clarify local vs. global scour. | §2.1 new paragraph | Explicit statement that all scour events in this programme are local (concentric per-bucket excavation, inter-bucket seabed undisturbed). Global scour flagged as future work. | Closed |
| R1.4 | Three excitation types (impulse, sinusoidal, square-wave) — why arranged this way, and are frequency calculations cross-compared? | §2.3 rewrite | Rewrite clarifies impulse free-decay is the primary quantitative method; sinusoidal sweep and square-wave serve as calibration. Cross-method comparison cited to the ISFOG 2025 companion paper (clustering 10.5–11 Hz, ±2.3 % spread, smaller than the 6 % per-stage scour decrement). | Closed |
| R1.5 | Supplement particle-size distribution curve for SNU silica sand. | §2.4 new fig-grain-size |
Grain-size distribution curves for SNU No. 5, 7, and 8 sands with USCS subdivisions and \(d_{10}\), \(d_{50}\) values drawn. | Closed |
| R1.6 Part A | Fig 1 and Fig 7 plan-view clarification: in Fig 1 buckets B and C appear vertically aligned; the description of Fig 7 says B and C experienced different settlements. | §2.1 new fig-plan-view (Fig 1 panel c) |
New standalone plan-view panel showing actual 3-fold tripod symmetry at 120°, shake direction aligned to A–B axis. Caption clarifies that Fig 1a is a cross-section through the A–B axis, so bucket C is geometrically hidden behind B on the line of sight (not aligned with B in plan). | Closed |
| R1.6 Part B | Even with the symmetry clarified, B vs. C settlement difference needs quantitative attribution. | §3.4 new paragraph | Cumulative \(\Delta s_{BC} = 4.2\) mm model (294 mm prototype) quantified and attributed to: (1) APA actuator-vector misalignment (\(\pm 2°\)–\(5°\)) projecting up to 8.7 % of push–pull amplitude onto B–C axis; (2) out-of-plane tilt during the bending-to-tilting mechanism transition; (3) centrifuge sand-bed preparation scatter. | Closed |
| R1.7 | Push–pull couple produces vertical displacement per bucket, but individual buckets also generate horizontal displacement component under overall rotation — how is this accounted for? | §4.1 new paragraph | Tilt angle \(\theta \approx 2.59°\) at \(S/D = 0.58\) derived from measured \(\Delta s_{AB}\). Horizontal bucket-cap translation \(\approx 7.5\) mm model (525 mm prototype) from \(r \sin \theta\). Height-graded LVDT ratios (5.8× mudline vs. 1.2× nacelle) confirm rigid-body tilt kinematics. | Closed |
| R1.8 | Saturated-vs-dry frequency variation (saturated smaller) needs fundamental explanation. | §4.3 new lead paragraph + new fig-stress-scour |
Three-panel effective-stress and \(G_{\max}\) schematic pre- and post-scour for dry and submerged conditions. Analytical prediction \(\sqrt{\gamma_d / \gamma'} = 1.23\) matches observed T2/T5 sensitivity ratio of 1.25 within 2 %. | Closed |
| R1.9 | Add summary of scour impact on multi-bucket / multi-pile wind turbine structures in the introduction; two specific references suggested. | §1 new paragraph | Five jacket-dynamics references added (Li 2022 Ocean Eng 111848, Hong 2026 SDEE 110004, Wang 2024 Ocean Eng 119716, Zhang 2024 sloping-bed scour, Katsanos 2025 repowering). | Closed |
Reviewer 2 — transition mechanism, higher-frequency content¶
| ID | Paraphrased concern | Target location | Action taken | Status |
|---|---|---|---|---|
| R2.1 | "The transition was abrupt rather than gradual" — analyse the reasons; add supplementary raw-data graphs. | §3.4 new paragraph | Three-mechanism explanation: (1) nonlinear demand-to-capacity ratio crosses 50–70 % threshold over \(\Delta(S/D) \approx 0.2\); (2) post-yield effective base reduction accelerates strain increment; (3) asymmetric kinematic locking prohibits intermediate regime. Raw-data archive path cited. | Closed |
| R2.2 | Was higher-frequency content considered? Is its change sensitive? | §2.3 new paragraph | \(f_2 \approx 110\) Hz model (\(\approx 1.57\) Hz prototype) tracked across all tests. Fractional variation is smaller than \(f_1\) as expected from second-mode curvature distribution. Reported as cross-check, not primary indicator. | Closed |
Reviewer 3 — permeability scaling, stress history, literature, generalisation, references¶
| ID | Paraphrased concern | Target location | Action taken | Status |
|---|---|---|---|---|
| R3.1 | Water-pore-fluid permeability scaling issue not discussed; may affect pore-pressure predictions. | §2.4 expanded paragraph | Four-point argument: (i) \(G_0\) dominance over pore-pressure response; (ii) sub-threshold strain amplitudes \(\gamma < 10^{-5}\) confirmed by PPT records; (iii) ~seconds consolidation time at 70 g prevents cumulative build-up; (iv) reported \(f_1\) trends unbiased. Two consequences explicitly disclosed. | Closed |
| R3.2 | 1 g scour → 70 g reconsolidation may overestimate post-scour stiffness; limitation deserves deeper treatment. | §7 restructured Limitations | Direction of bias (overestimates stiffness, underestimates \(\Delta f_1\) and cumulative response), quantitative bound \(\approx 2\)–3 % at \(S/D = 0.58\), cancellation in relative \(f/f_0\), implications for monitoring (conservative early-warning). | Closed |
| R3.3 | Literature review lacks focused discussion on jacket-structure dynamic performance under practical offshore conditions; four references suggested. | §1 new paragraph | Same five-reference paragraph as R1.9 (shared response). | Closed |
| R3.4 | Real-turbine to simplified centrifuge-model conversion needs more detail. | §2.2.1 new #sec-idealisation |
Prototype-to-model error budget explicitly disclosed: RNA over-representation \(+9.5\) % (bias cancels in relative \(f/f_0\)); \(EI_{\text{eq}}\) under-match \(-2.3\) % (below measurement scatter). Cross-paper consistency with J2 stated (J2 narrow-RNA 280.5 t vs. J3 inclusive 338 t reconciled by APA mounting-hardware prototype-equivalent). | Closed |
| R3.5 | Conclusions should emphasise that findings may not generalise to deeper scour, asymmetric scour, layered seabed, or field-scale conditions without further validation. | §7 Limitations Generality paragraph | Explicit generalisation caveat added. | Closed |
| R3.6 | Some references have formatting errors; two recent papers suggested. | references.bib | CrossRef validator sweep. New additions: Wang 2024 Transportation Geotechnics 101433 (AI-flume for local scour); Wang 2025 Construction and Building Materials 140858 (solidified-soil scour mitigation). | Closed |
| R3.7 | Highlight innovation of this work vs. companion numerical paper; add practical "Design Recommendations" to Conclusions. | §6.1 new #sec-innovation + §7.3 new #sec-design-recs |
Innovation subsection states threefold innovation. §7.3 provides six practical Design Recommendations covering saturation-corrected calibration, multi-sensor monitoring, backfill grade selection, early-warning triggers, precision requirements, numerical-twin cross-check. | Closed |
Change log — 20 manuscript-level items keyed to reviewer comments¶
| # | Location in R1 manuscript | Change | Driving comment |
|---|---|---|---|
| 1 | §1 new paragraph | Five jacket-dynamics references | R1.9 + R3.3 |
| 2 | §1 scour-remediation paragraph | Two new scour-mitigation citations | R3.6 |
| 3 | §2.1 line 113 | Updated Fig 1 caption with three-panel layout and section-plane-vs-plan-view clarification | R1.6 Part A |
| 4 | §2.1 line 115 | New standalone plan-view figure | R1.6 Part A |
| 5 | §2.1 new paragraph | \(S/D\) rationale (Gunsan envelope + Jalbi 2018 tripod scaling) | R1.1 |
| 6 | §2.1 new paragraph | Local-vs-global scour clarification | R1.3 |
| 7 | §2.1 new figure | Two-panel scour-hole schematic | R1.2 |
| 8 | §2.2.1 new subsection | Prototype-to-model error budget + cross-paper consistency with J2 | R3.4 |
| 9 | §2.3 rewrite | Excitation-methods: impulse primary, sweep/square-wave calibration, cross-method cite | R1.4 |
| 10 | §2.3 new paragraph | Higher-mode \(f_2\) cross-check | R2.2 |
| 11 | §2.3 Table 3 footnote | Pointer to §idealisation for inclusive-target explanation | R3.4 |
| 12 | §2.4 new figure | Grain-size distribution for SNU No. 5, 7, 8 sands | R1.5 |
| 13 | §2.4 expanded paragraph | 4-point permeability-scaling argument + 2 consequences | R3.1 |
| 14 | §3.4 new paragraph | Abrupt-transition 3-mechanism explanation + raw-data archive pointer | R2.1 |
| 15 | §4.1 new paragraph | Tilt-angle horizontal coupling; height-graded LVDT confirmation | R1.7 |
| 16 | §4.3 new lead paragraph | Direct Fig 12 explanation + stress-release schematic pointer | R1.8 |
| 17 | §4.3 new figure | Three-panel effective-stress and \(G_{\max}\) schematic | R1.8 |
| 18 | §6 new subsection | Innovation vs. companion numerical paper + joint-use recommendation | R3.7 |
| 19 | §7 restructured Limitations | Reconsolidation bias direction/bound/implications; Generality paragraph | R3.2 + R3.5 |
| 20 | §7.3 new subsection | Six practical Design Recommendations | R3.7 |
Bibliography changes¶
Seven new entries added, each CrossRef-verified before insertion:
- Li et al. (2022) — Ocean Engineering 259:111848 (multi-bucket jacket bearing capacity under scour) — R1.9.
- Hong et al. (2026) — Soil Dynamics and Earthquake Engineering 203:110004 (seismic response of tetrapod piled jacket in clay) — R3.3.
- Wang et al. (2024) — Ocean Engineering 314:119716 (tetrapod jacket with semi-rigid vs. flexible piles) — R3.3.
- Zhang et al. (2024) — local scour on sloping beds — R3.3.
- Katsanos et al. (2025) — recommissioned OWT dynamic performance — R3.3.
- Wang et al. (2024) — Transportation Geotechnics 49:101433 (AI-flume for local scour) — R3.6.
- Wang et al. (2025) — Construction and Building Materials 472:140858 (solidified-soil scour mitigation) — R3.6.
One existing entry (Kim et al. 2025 ISFOG companion) was upgraded with full publication metadata.
New reproducibility scripts¶
generate_fig1_plan_view.py(R1.6 Part A).generate_fig_scour_schematic.py(R1.2).generate_fig_grain_size.py(R1.5).generate_fig_stress_scour.py(R1.8).
Each produces PNG + SVG deterministically with fixed seeds; metadata embedded per the figure_generator convention.
What did NOT change from original submission¶
- Core experimental programme (22 centrifuge test cases across T1–T5, in-flight CPT, APA440MML excitation, KAIST 70 g beam centrifuge).
- Reported natural-frequency values and their sensitivity (T4: 0.85 %, T5: 2.58 % at \(S/D = 0.58\)).
- Bending-to-tilting transition finding (displacement amplification 4.27×, strain reversal +21 % → −11 %, asymmetric settlement 13.2 mm vs. 0.3 mm in T5 at \(S/D = 0.58\)).
- Authorship, affiliations, funding acknowledgements.
Companion-paper coordination¶
J3 is the experimental companion to J2 (the numerical-modelling paper, currently under R2 revision). The two papers use the same 4.2 MW Gunsan turbine geometry and share the same three-bucket tripod foundation. Key coordination in the R1 response:
- Prototype-to-model error budget in J3 §2.2.1 explicitly reconciles J2's narrow-RNA 280.5 t with J3's inclusive 338 t.
- Jacket-dynamics citations (R1.9 / R3.3 here) are the same block used in J2's R2 response.
- AI-disclosure boilerplate text shared.
- CrossRef validator sweep covers both bibliographies in one pass.
Raw reviewer comments (verbatim from decision letter, 2026-03-17 / OE-D-26-02685)¶
The text below is the journal's decision letter and the three reviewer reports exactly as received.
Editor's decision letter
Title: Centrifuge assessment of saturation and backfill effects on scour-induced response of offshore wind turbine with tripod suction bucket foundations
Editor: Prof. Tiago Ferradosa, Deputy Editor, Ocean Engineering
Dear Professor Kim,
The reviewers have commented on your above paper submitted to Ocean Engineering. I would be grateful if you could address the comments by the reviewers given below and resubmit your revised manuscript by May 06, 2026. Please carefully address the issues raised in the comments.
Reviewer #1 — verbatim
This study presents centrifuge tests at 70g on an offshore wind turbine with a tripod suction bucket foundation under saturated sand conditions, extending previously published dry-sand results. The experiment focused on investigating the effect of scour on the natural frequency of the tripod bucket foundation-supported offshore wind turbine structure. The experimental steps and results introduction are generally clear. The article is also well organized. However, before accepting the paper, there are the following issues that need to be clarified.
(1) Line 55 on Page 3, three to four progressively deeper scour stages were applied up to S/D≈0.5-0.6. For a monopile, the scour depth can reach 2D. Why was such a range of values selected? In actual marine environments, what is the scour depth typically achieved for the tripod bucket foundation? It is recommended to verify the rationality of S/D selection in the text.
(2) Suggest adding a schematic diagram to show the shape of the scour hole around the tripod bucket foundation.
(3) Is the experiment simulating local scour or global scour, or both? Please make it clear in the text.
(4) Lines 15-19 on page 8: The three types of excitation, including impulse release, sinusoidal sweeps, and square-wave pulses, are all used to measure the natural frequencies of the structure? If so, why are they arranged in this way? The frequency calculation results obtained from the three types of waves should be compared and presented.
(5) In section 2.4, it is recommended to supplement the particle size distribution curve for SNU silica sand.
(6) Compare the plan layout of the three buckets in Fig. 1 and Fig. 7. In Fig. 1, it seems that buckets B and C are vertically aligned (so only one is visible), and the earthquake shaking direction is perpendicular to the line connecting B and C. If so, the bearing behavior of the two should be identical. However, the description of Fig. 7 indicates that B and C experienced different settlements. The plan layout of the three buckets in the experiment still confuses me. Please clarify it.
(7) Line 39 Page 20, Under tripod moment loading, each bucket experiences cyclic vertical compression and tension through the push-pull couple. As shown in Figure 8b, when the tripod bucket foundation rotates as a whole, the individual bucket not only undergoes vertical displacement but also generates a horizontal displacement component. How do you account for this?
(8) As shown in Figure 12, compared to dry sand, the frequency variation of saturated sand is smaller. Please explain the reason fundamentally.
(9) Suggest adding a summary of the impact of scour on the mechanical properties of multi-bucket or multi pile wind turbine structures in the introduction, such as the following references:
- Scour effects on the bearing capacity of multi-bucket jacket foundation for offshore wind turbines, Ocean Engineering 259 (2022) 111848.
- Seismic response of offshore wind turbine supported by tetrapod piled jacket foundations in clays considering scour, Soil Dynamics and Earthquake Engineering, 2026, 203, 110004.
Reviewer #2 — verbatim
This paper presents centrifuge tests at 70g on an offshore wind turbine with a tripod suction bucket foundation under saturated sand conditions, extending previously published dry-sand results. The research results are helpful for the monitoring of TSB foundations. The following are the opinions.
1. In page 18, line 3, "The transition was abrupt rather than gradual." It is suggested to analyze the reasons. Add supplementary test original data graphs.
2. Was the higher frequency components taken into account in the data analysis? Is the change in high-frequency values sensitive?
Reviewer #3 — verbatim
This manuscript investigates the scour-induced dynamic response of offshore wind turbines supported by tripod suction bucket foundations. The centrifuge tests and the paper can provide useful experimental observations on frequency degradation, backfill recovery, and possible changes in structural response mechanism. Overall, the manuscript has potential for publication. Before final acceptance, there are still some issues that need to be addressed, the details are as follows:
1. The study uses water as the pore fluid, but the scaling issue associated with water permeability is not considered. This may introduce errors in the prediction of pore pressure accumulation and dissipation during the tests. Although the manuscript assumes that time-scaling conflict and partial drainage effects can be neglected, the authors should explain this assumption more carefully and discuss how ignoring the permeability scaling issue may affect the interpretation of the pore pressure response and the applicability of the results.
2. Scour was excavated at 1g and then reconsolidated at 70g, and the authors acknowledge that this may overestimate post-scour stiffness. This limitation is important and could be discussed in greater depth. In particular, the manuscript would be strengthened by clarifying how this procedure may influence the measured frequency, displacement, and settlement responses, and whether it could lead to an underestimation of softening and cumulative damage associated with real in-situ scour evolution.
3. The literature review in the Introduction lacks a focused discussion on the dynamic response of jacket structures in practical offshore applications, including the effects of wind, wave and current loadings, also the seismic excitation. The following references are suggested for further consideration:
- Numerical evaluation of the dynamic performance of recommissioned offshore wind turbines under service life extension and repowering strategies;
- Seismic response of offshore tetrapod piled jacket foundations subjected to environmental loads in soft-over-stiff clay deposit;
- Experimental investigation on the mechanism of local scour around a cylindrical coastal pile foundation considering sloping bed conditions;
- Comparative study of seismic response of offshore tetrapod jacket systems with semi-rigid and flexible piles under environmental loads;
4. More details are needed on the turbine setup, the structural simplifications, and the selected geometric parameters for the tripod jacket structure. In particular, the conversion from the real turbine to the simplified centrifuge model should be explained more clearly.
5. The authors already note that the work is limited to uniform sand, symmetric scour, and a single model scale, with scour depths restricted to S/D ≤ 0.58. Given that the T5 series already shows strong nonlinearity and a clear mechanism transition at the maximum scour level, the conclusions should more explicitly emphasize that the present findings may not directly generalize to deeper scour, asymmetric scour, layered seabed, or field-scale offshore conditions without further validation.
6. Some references have formatting errors, please carefully check. In addition, to further portray the state-of-the-art of targeted problem in a up-to-date manner, the authors can considerer to add the latest closely related paper, such as "Establishment and implementation of an artificial intelligent flume for investigating local scour around underwater foundations. Transportation Geotechnics, 49: 101433" and "Investigation of the protection mechanism and failure modes of solidified soil utilized for scour mitigation. Construction and Building Materials, 472: 140858." to the references.
7. The authors need to highlight the innovation of this work, e.g., compared with 26-00984, while the limitations need to be addressed as well. It is recommended to add a set of practical "Design Recommendations" in the Conclusions.
Where this links in the rest of the portfolio¶
- Scientific page: Papers / J3.
- Workflow alignment: J3 methodology prototype — the seven-phase pass on J3's methodology section independently flagged three figure gaps (stress-scour schematic, grain-size, permeability/plan-view clarity). Several of those same gaps were called out by R1 reviewers; the workflow's ability to anticipate reviewer concerns was validated in practice.