887-B120-01_Towing and Resistance Calculations Report_Rev(-)_signed.pdf

NSF MCMURDO OFFLOAD INFRASTRUCTURE 9 June 2023 Towing and Resistance Calculations 1 Doc. 887-B120-01, Rev -

NSF MCMURDO OFFLOAD INFRASTRUCTURE

Towing and Resistance Calculations

PREPARED FOR:

Moffatt & Nichol Seattle, WA

BY:

Nate M. Seelig, PE

PROJECT ENGINEER

CHECKED:

Andrew L. Girdler, PE

NAVAL ARCHITECT

APPROVED:

Bradley G. Lamkin, PE

PRINCIPAL-IN-CHARGE

DOC. #:

887-B120-01

REV:

FILE:

22105.01

DATE:

9 June 2023

References

1. ABS, Rules for Building and Classing Steel Barges, January 2023.

2. DNV, Marine Operations and Marine Warranty, DNV-ST-N001, September 2021.

3. DNV, Modelling and Analysis of Marine Operations, DNV-RP-N103, September 2021.

4. Glosten, 887_ABS MVR & SBR Equipment Number Calculations_Rev(-).

5. Glosten, 887_DNV Towline and Equipment Calculations_Rev(-).

6. Glosten, Towing Arrangement, 887-B410-02.

Summary

This report presents the results of the Towing and Resistance calculations performed for the McMurdo Barge Pier (328'×100'×18'). The vessel is to be classed ✠A1, Deck Cargo Barge by the American Bureau of Shipping (ABS). The towline minimum breaking load (MBL) derived from the ABS Steel Barge Rules Equipment Number EN per Reference 1 was compared to that based on the DNV towline pull required per Reference 2. The maximum value will be adopted and will be used to inform recommended tug bollard pull (BP) capacity.

Approach

The ABS approach normalizes a barge’s displacement and side and frontal wind areas in the form of an equipment number EN, which has a corresponding towline MBL.

The DNV approach calculates the towline pull required (TPR) which considers the wind, wave drift, and current (relative speed between towed barge and water) forces. The “standard” (non-benign) climatology is adopted for unrestricted tow, which assumes the following: significant wave height, Hs = 5m, wind speed, Vw = 20 m/s, and current speed, Vc = 0.5 m/s.

The wind and current forces are calculated using a first principles approach of a flat plate in a flow, Equation 1 below, where A is the projected frontal area of the barge above and below waterline, respectively.

Equation 1 Drag Force

𝐹 𝐶 𝐴𝜌 𝑉

Towing and Resistance Calculations 2 Doc. 887-B120-01, Rev -

The wave drift is calculated using Equation 2 below, per Reference 3, where R is a wave reflection coefficient based on barge shape.

Equation 2 Wave Drift Force

𝐹 𝜌𝑔𝑅 𝐵𝐻

A continuous tug BP is calculated based on the assumed tug efficiency in a given seaway. The towline MBL is calculated using a formula that provides a factor of safety as a function of environment and tug BP (see Reference 2, Table 11-22).

Results

The resulting ABS EN is 470. The corresponding towline MBL per Reference 1, Table 3B is 62,300 lbs (28 tonnes). Detailed calculations are provided in Appendix A and Reference 4.

The DNV TPR (and effective BP) is calculated to be 111,400 lbs (51 tonnes). The corresponding static continuous BP per Reference 2, Figure 11-8, is approximately 78 tonnes, which yields a minimum towline MBL in ice of 270 tonnes. The resultant bridle and shackle capacities are 309 and 350 tonnes, respectively. The minimum deployable length of the towline as per the “European formula” as specified in Reference 2 is 650 m. Detailed calculations are provided in Appendix B and Reference 5.

The DNV method is more conservative by an order of magnitude as it considers an open ocean seaway and ice, therefore these minimum required values will be used to size the towing equipment and inform tug selection. The proposed towing arrangement is shown in Reference 6.

Towing and Resistance Calculations A-1 Doc. 887-B120-01, Rev -

Appendix A ABS Equipment Number Calculation

EN 469.8

Δ 3961 LT

B 100 ft h 0 ft a 10 ft

A 3280 ft2 b 0 ft h1 14.6 ft

ABS SBR EN

NSF MCMURDO OFFLOAD INFRASTRUCTURE

Towing and Resistance Calculations

A‐2

ABS Towing EN

9 June 2023

Doc. 887‐B120‐01, Rev ‐

Towing and Resistance Calculations B-1 Doc. 887-B120-01, Rev -

Appendix B DNV Towline and Equipment Calculations

Wind drag force

FD=CdAρV /2

A= 1948.65 ft includes containers across full breadth

A= 181.0 m2

Cd= 1.20 flat plate ρ= 1.23 kg/m air

V= 20.00 m/s wind speed

FD,w = 53,224 N

11,965 lbs

Wave drift force ρw= 1025 kg/m g= 9.81 m/s2

R= 0.67 barge with raked Bow

B= 100 ft breadth at waterline

B= 30.5 m

Hs= 5 m

Fwd = 429,940 N

96,654 lbs

Current drag force

FD=CdAρV 2/2

A= 496.95 ft

A= 46.2 m2

Cd= 2.10 for rectangular boss ρ= 1025.00 kg/m sea water

V= 0.50 m/s current speed

FD,c = 12,422 N

2,793 lbs

Towline pull required

FD,w = 11,965 lbs wind drag force

Fwd = 96,654 lbs wave drift force

FD,c = 2,793 lbs current drag force

TPR = 111,412 lbs sum of above forces

TPR = 50.6 tonnes

NSF MCMURDO OFFLOAD INFRASTRUCTURE

Towing and Resistance Calculations

B‐2

DNV ‐ Towline

Static continuous bollard pull

BP= 78 tonnes Figure 11‐8

Minimum towline MBL in ice

MBL= 268.9 tonnes Selectec wire rope `2‐3/8

265 LT EIPS 302 ton

296.313775 ST 2686.592 kN

2637.78415 kN 273.8626 tonnes

269.6429 LT

NSF MCMURDO OFFLOAD INFRASTRUCTURE

Towing and Resistance Calculations

B‐3

DNV ‐ Towline

MBL of Towline 268.9 tonnes

592,628 lbs

Tug Bollard Pull 78 tonnes

Bridle Load Capacity Taken to mean Breaking strength

ULC 308.9 tonnes

680,788 lbs

Towline Length

DTL 650.0 m

2,133 ft

Shackles

MBL 349.6 tonnes

770,416 lbs

Equipment selection:

Reference: Washington Chain and Supply Catalog Pg 55‐58

Tow Plate

No. 3 Proof load 624,000 lbs 283.1216

SF 1.5

Breaking Load 936,000 lbs 424.6824

Shackle

No. 211 Working Load 94 Tons

Size 3 SF 6

Breaking Load 564 Tons

1,128,000 lbs

NSF MCMURDO OFFLOAD INFRASTRUCTURE

Towing and Resistance Calculations

B‐4

Towline Equipment