TECHNICAL MEMO 060217-01-Seatel 5012 Installation-Okeanos Explorer--REV-..._101930706_101944382.pdf

GFOE TECHNICAL MEMO 060217-01

REVISION HISTORY

REV Description of Change Author Date

0 Initial release T.Gregory June 2, 2017

1 GFOE review by D.Lovalvo and K.McLetchie T.Gregory June 5, 2017

2 Revisions to FEA Model. Addendum added, Interaction with ABS

T.Gregory July 17, 2017

REFERENCE DOCUMENTS

Document Number Document Title

Seatel 138222 REV-A Installation Manual for Seatel 5012-33 KU-Band Broadband-At-Sea

VSAT Antenna System

Seatel 97-146742 Ver-A Installation Arrangement, Mid-Sized Radomes with External Air

Conditioner

Seatel 130040 REV-A Antenna Installation Guideline

Seatel 132705 REV-A Antenna Installation Guideline

Glosten 05056.036 VSAT Antenna Failure Analysis

GFOE-2070 VSAT Locations, Okeanos Explorer

GFOE-2065 VSAT Install Assembly

OE-150-101 NOAA Drawing, Structural Mods, Mission Deck and Above

SEATEL 5012 VSAT

Installation on NOAA Ship

Okeanos Explorer

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Global Foundation for Ocean Exploration 2

1. Purpose

The purpose of this document is to summarize the design for mounting an OMAO provided

Seatel 5012 satellite antenna system on the NOAA ship Okeanos Explorer. The chosen location for the antenna and a description of the structural design will be presented.

2. Background

Presently, there is a GFOE 2.4m Seatel 9711 satellite system mounted on top of an existing mast platform, approximately at midships. This antenna was a new install in 2015. The antenna's platform is 58' above ship baseline. This antenna's primary purpose is to support communications, data transfer, and video streaming of the ship mission: ROV dives and

Multibeam seafloor mapping.

Currently, the 2.4m antenna also supports ship communications in addition to its primary purpose of serving the ship Mission. It is the desire of NOAA to add a second, smaller dish intended strictly for ship usage. The 2.4m antenna will remain onboard in its current location to continue supporting the ship Mission.

Note that the Seatel 5012 system is offered with an integrated Air-Conditioning system and pedestal. This package is strongly recommended for heating/cooling and dehumidifying the radome enclosure. The structural design offered by GFOE assumes that Seatel's air-conditioner and its associated pedestal will be employed. See reference "Seatel 97-146742 Ver-A, Installation Arrangement, Mid-Sized Radomes with External Air Conditioner."

3. Antenna Location

The new antenna, a Seatel 5012, will be mounted on the Upper Deck (02 Deck), on a new mast-structure directly above the aft Control Console. The base plate of the antenna will be 46' above ship baseline, and centered 16.7' to port. Seatel provides a guideline for locating an antenna, included in reference document "Seatel 130040 REV-A, Antenna Installation Guideline." The location was selected for a number of reasons, in keeping with Seatel's guidance:

• Clear view of the sky with minimal occlusions

• Short cable-runs to the ship electronics rack room

• Ready access to adequate ship structure for interfacing the new antenna mast

• Location does not interfere with deck-crane operating envelopes

• The new structure offers the ability to construct a weather cover for operators standing at the aft Control Console.

The location of the new antenna is depicted in reference drawing GFOE-2070. Portions of that drawing are included below in Figures 1 and 2. These views demonstrate the expected occlusions. Below an antenna elevation angle of 21 degrees, the existing 2.4m antenna radome will occlude the view of the new antenna through an azimuth angle of 12 degrees. Otherwise, the only other occlusion is the radar and signal-mast above the Bridge Deck, which interferes below an elevation angle of 13 degrees. In summary, the only situations when the new Seatel

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5012 antenna will have an occluded view of the sky will be at low elevation angles, and then only through limited azimuth angles.

Figure 1: Profile View, Seatel 5012 and 9711

Figure 2: Plan View, Seatel 5012 and 9711

4. Design of Structure

The structure for mounting the Seatel 5012 antenna system emulates similar designs used in the

NOAA fleet. Plans of a similar antenna mast on the NOAA ship Thomas Jefferson were provided to GFOE for review. For the Okeanos Explorer, the structure is centered over the Aft

Control Console, such that it provides some cover and shade to the operators. The four primary legs of the mast structure will tie into existing ship structure: the port side-shell, the aft bulkhead of the ROV Hangar, and a heavy longitudinal girder under the decking. Figure 3 shows an isometric view of the CAD model. The view is looking aft and outboard towards the port-side.

There are four legs, made of 6" schedule 80 pipe. Each leg lands on existing ship structure, either adjacent to structural bulkheads, or on top of a longitudinal deck girder. The upper platform is comprised primarily of 6" I-beams, surrounded by a 39" tall railing. The platform decking is fiberglass grating.

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Global Foundation for Ocean Exploration 4

Figure 3: Isometric View of Mast Structure, looking aft and outboard to port

The view from the aft Control Console will be minimally obstructed by the addition of the structure. Note the integrated ladder providing access to the platform.

As outlined in Seatel's reference document "Seatel 130040 REV-A, Antenna Installation

Guideline," the structure must be stiff enough to avoid unwanted harmonic vibrations that could hinder the function of the antenna's tracking system. Rather than optimizing the structural design for minimal weight, the scantlings of the structure will ensure a stiff platform. Optimizing the structure to reduce a modest amount of weight, potentially a few hundred pounds, would risk making the platform less rigid.

The structure is designed to withstand a Category 5 hurricane wind loading and combined acceleration loading along the three cardinal axes. Further discussion of the structural analysis is included in Section 5.

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4. Summary of Weights

A summary of additions to the ship mass is compiled in Table 1, showing the mass of the individual components and their centers. The total additional mass is 3,050 lb. The Longitudinal

Center of Gravity (LCG) is measured from the ship's Forward Perpendicular. The Vertical

Center of Gravity (VCG) is measured from ship Base Line. The Transverse Center of Gravity

(TCG) is measured to port from ship Center Line. Masses of the antenna equipment are provided by Seatel, and masses of structure are modeled from the 3D CAD program, Solidworks.

Component Mass Center of Mass

LCG VCG TCG

lb ft ft ft

Seatel 5012 Antenna 400 169 49.8 16.7

Seatel A/C and Pedestal 200 169 46.9 16.7

Upper Structure with Grating and Railing

1,150 169 45.8 16.7

Lower 4-leg Structure 1,300 169 41.1 16.7

Total Additions 3,050 169 44.4 16.7

Table 1: Weights and Centers of Additions to Ship

5. Discussion of Structural Analysis

In keeping with the guidance from Seatel, the antenna mast is designed to be structurally robust.

A determination of the design loads of the structure was conservative. Extreme wind loading and extreme acceleration loading was used to prove the survivability of the structure.

Seatel reference documents "Seatel 130040 REV-A" and "Seatel 132705 REV-A," provide useful guidance for determining the dynamic loading due to ship motions. One empirical method outlined in the reference documents employs Germanischer Lloyds (GL) rules for estimating acceleration loading at a specific location on a vessel: Rules for Classification and Construction, Chapter III - Naval Ship Technology, Volume 1, Part 1, Section 5B. This method was used to predict dynamic loading of the new location, and was also used to compare the loading at the larger antenna's location near mid-ship.

In 2010, Glosten Associates performed a study of the acceleration loading of the Okeanos

Explorer's original VSAT antenna's mounting location, see reference document ”Glosten

05056.036, VSAT Antenna Failure Analysis." The original vertical position of the larger Seatel

Antenna was substantially higher than its present location, and the antenna and its mounting platform suffered premature failure. Glosten demonstrated that by reducing the vertical position of the antenna, a substantial reduction in tangential accelerations, due to pitch and roll, could be

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Global Foundation for Ocean Exploration 6 achieved. Table 2 shows an excerpt from their document, in which they summarize the acceleration loading at various vertical positions. At the time of the study, the antenna was mounted at Location #1, labeled "current" in the below excerpt. The present location of the

Seatel 9711 antenna is centered slightly below Location #2 in Table 2.

Table 2: Excerpt from 2010 Glosten Study 05056.036

This document combined observed ship motions data and theoretical motions as predicted by a strip-theory ship motions program. They provided statistical analysis of lifetime extreme accelerations at the proposed antenna locations, as reported in Table 2. Glosten's reported accelerations can be treated as realistic lifetime extreme values. The GL method is an estimation based on a ship's principle characteristics.

The longitudinal and transverse locations of the new Seatel 5012 antenna do not match the midship location from the Glosten study, so their values cannot be applied without adjustment.

In order to compensate for the different antenna locations, the GL method was applied at

"Location 2" presented in the Glosten report. By comparing the various results, a design loading can be inferred. Table 3 summarizes the results of these methods. Compared with the Glosten values, it is clear that the GL method over-estimates dynamic loading in two of the three axes, most notably in the transverse (lateral) direction.

Method and Location Height Accelerations

Longitudinal

Acceleration

Lateral

Acceleration

Vertical

Acceleration

Ft above BL g g g

Glosten Study

Seatel 9711 at Location 2 71 1.01 1.45 0.61

GL method

Seatel 9711 at Location 2 71 0.49 4.51 0.98

GL method

Seatel 5012 above Aft

Control Console

50 0.32 2.83 1.35

Design Accelerations 50 1.0 1.5 1.0

Table 3: Comparison of Accelerations

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Global Foundation for Ocean Exploration 7

The GL method under-predicts the longitudinal acceleration, severely over-predicts the lateral acceleration, and somewhat over-predicts the vertical acceleration. It can be inferred that the aft-ward location of the Seatel 5012 antenna will increase the vertical component of acceleration compared with the Seatel 9711 location, as the new location is further away from the ship's center. The lower vertical position of the new antenna will result in lower longitudinal and lateral accelerations, as the mounting location is lower than the larger antenna. To be conservative, we are using the same accelerations that Glosten determined in the longitudinal and lateral directions, but increasing the vertical component to account for the new antenna's location aft of midship.

To prove the survivability of the new structure under extreme conditions, the author has applied a combined loading due to wind and accelerations. Wind is 150 knots, and applied to the Seatel radome with a coefficient of drag equal to 0.54. Accelerations are applied simultaneously along the three cardinal axes, as outlined in Table 3. This is a conservative load case, as the application of all loads simultaneously is highly unlikely. This extreme combined loading is unlikely to occur during the life of the ship, but acts as a stringent test of the survivability of the structure.

An FEA model was developed for the new mast and the surrounding ship structure. Multiple studies were performed to determine the most adverse loading scenario. The worst load case was determined by iterative analysis, and occurs when the inboard/forward Mast Leg exerts a downward load on the Longitudinal Girder on which it sits, putting the member in bending.

Wind loading is applied to the antenna radome from the port side. Vertical acceleration is applied to the antenna and structure downward (1 g + gravitation = 2 g). Longitudinal acceleration (1 g) is applied in the forward direction. Transverse acceleration (1.5 g) is applied towards the starboard side. The Radome is not included in the FEA Mesh, but its acceleration and wind loads are applied to the Radome's mounting flange via a Remote Load with Rigid

Connection, and the loads are applied at the Dome's center.

In addition to the Acceleration and Wind loading, a uniform pressure is applied to the 02 deck, equivalent to 4.6 ft of hydrostatic head (2.0 psi). This deck head is specified in the ABS rules:

Vessels Under 90m, Part 3, Chapter 2, Section 3; 3.1.4.

The extent of the meshed structure extends to the nearest rigid members of the existing ship structure. The transverse bulkhead and side-shell are terminated with fixed-supports at the Main-

Deck Level. The 02 deck is terminated at its forward end, at the intersection with a transverse bulkhead. The inboard edge of the 02 deck and frames are terminated with the nearest longitudinal girder. The solid mesh has 410,866 elements, each 1" maximum length. Figure 4 shows the meshed model, with fixed supports at the edges of the model which are attached to rigid structure. The portion of the transverse bulkhead cutout for a garage-door is not supported at its edges.

The combined loading scenario puts the Forward / Inboard leg of the mast structure in compression, and thus puts the existing Longitudinal Deck Girder and Transverse Frame in bending. Loading of the other three legs is adjacent to nearby bulkheads and is well supported without inducing significant stresses. Note that the Aft / Outboard leg lands adjacent to the

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Global Foundation for Ocean Exploration 8 nearby bulkheads, but on soft-plate. The deck plating should be supported below-deck with a stiffener, and is so noted in Drawing GFOE-2065.

The bending stress in the Longitudinal Girder is the primary focus of the structural analysis, both in the FEA model runs and in the hand-calculations. Stress induced in the existing structure adjacent to the other three legs is not significant.

Figure 4: FEA Mesh of Structure and Fixtures

Figures 5 and 6 show plots of Von Mises stress in the new and existing structure. The scale of stress in the images is from blue (zero) to red (18,000 psi). Yield strength of A36 steel is 36,000 psi, with a maximum allowable stress of 24,000 psi. The maximum stress in isolated locations is

16,000 psi, providing a minimum Factor of Safety of 2.25 with respect to the minimum yield strength of A36 steel. The one area of interest is in the transverse frame under the deck, below the forward / inboard leg of the mast structure. There is a bending stress induced in the deck's transverse frame due to the combined loading of inboard acceleration and wind. Aside from local stress concentrations, the magnitude of stress in the new mast structure and existing ship structure is low, well below the allowable stress of 24,000 psi.

Figure 7 shows the Reaction Loads at the Mast-Deck interface. Vertical load at the inboard/forward leg is downward at 5,200 lbf. Vertical loads at the other three corners is significantly less and is actually negative (upward), 398 lbf at the Forward / Outboard corner in this load-case. Inverting the wind direction and the directions of acceleration loading will switch the locations and magnitudes of upward/downward loading among the four legs. The load case presented herein represents the worst case downward loading for the forward/inboard leg.

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Global Foundation for Ocean Exploration 9

Figure 5: Von Mises Stress, Mast Structure and Ship Structure

Figure 6: Von Mises Stresses Under Deck

16,000 psi

Max Stress

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Figure 7: Reaction Loads at Mast-Deck Interface.

Figure 8 shows a validation of bending stress in the Longitudinal Girder by means of a beam-theory hand calculation. The calculation is somewhat simplified, as it does not include a distributed load due to accelerated self-mass, as the load due to self-mass is insignificant even when adding 1*g vertical acceleration loading to 1*g gravitation (totaling 2.6 lb per inch). The calculation is further simplified, as the end conditions are considered free to rotate, not-fixed.

The latter simplification results in a conservative calculation, predicting bending stress much greater than if the end conditions of the beam were considered fixed. The member is a WT

8x15.5 Tee and the decking is 3/8" plate. The hand calculations predict a bending stress of 13.7 ksi in the Girder. The FEA model predicts a stress substantially lower, likely due to the significant supporting structure at the beam's ends. In either case, the predicted stress is substantially lower than the material's allowable stress of 24 ksi.

5,200 lbf Force

Acting Downward onto

Existing Structure ee

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Global Foundation for Ocean Exploration 11

FIGURE 8: Hand Calculation of Bending Stress in Longitudinal Girder

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Global Foundation for Ocean Exploration 12

6. Conclusions

The location for the Seatel 5012 antenna meets Seatel guidelines, provides a nearly uninterrupted view of the sky, and ties into existing ship structure. Appended to this document are plans prepared by GFOE engineers for the construction of the structure: "GFOE-2065-VSAT Install

Assembly." Installation of the Antenna, and routing cabling to the antenna and its air-conditioner should follow Seatel's document "Seatel 138222 REV-A, Installation Manual for

Seatel 5012-33 KU-Band Broadband-At-Sea VSAT Antenna System," or a later revision of that document if available at the time of installation.

Appended below is a discussion between ABS and the authors. Several points were questioned by ABS and the authors are providing answers and/or justification. Additional information has been added to REVISION-2 of this document in response to ABS' inquiry. Other notes are included below in direct response to their questions.

7. Addendum: Response to American Bureau of Shipping

The following is an email from Daniel Lamere of ABS, to Hank Malcolm of NOAA OMAO.

GFOE's responses are included in-line with the original text, in red lettering.

From: Daniel Lamere [mailto:DLamere@eagle.org] Sent: Friday, June 23, 2017 1:29 PM To: Hank Malcolm - NOAA Federal; Michael Roa; Geoffrey Wilkie - NOAA Federal Cc: Caren Amaya; Donald Jones - NOAA Federal Subject: RE: EX VSAT ABS Package Submission (NOAA OKEANOS EXPLORER, ABSCN 8901987)

Hank, In response:

1) Did you receive the attached design summary including a definition of design loads?

Yes, we received the design summary.

The above document has been modified and augmented with additional discussion as requested by ABS.

2) Does ABS require more or different calculations?

a. The calculation method appears adequate; additional information regarding results is requested. Please provide the maximum downward and upward forces induced by each of the four legs upon the existing ship structure as produced by various considered load cases. i.e., for every load case analyzed, a force at each leg is produced, either downward or upward, and the maximum upward and downward forces for each leg can be extracted from the results. Therefore, please submit details showing the stress value and contour of each of these maximum occurrences. There should potentially be a total of eight conditions shown, 4 legs times (1 maximum upward force plus 1 maximum

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Global Foundation for Ocean Exploration 13 downward force). A summary of results that specifies the resulting maximum stress for each condition at each leg is requested.

Please see Figure 7 in the text above. The Mast Leg of primary concern is the Inboard / Forward leg, as this location imposes a bending stress into the Longitudinal Girder and Transverse Frame

#83 below-deck. The vertical reaction load at this location is 5,200 lb downward, in the load case examined herein. If the loading scenario were altered, such as wind from a different direction or the acceleration load vectors reversed, it would be possible to exert a similar downward force at any of the four corners. Upward force at any of the four corners will never exceed the maximum downward loading, due to gravitation force on the ~3,000 lb mast and antenna.

Loading the other three mast legs is less of a concern, as each lands adjacent to stiff structure

(bulkheads). With the exception of the Aft / Outboard Leg, each leg lands above either the

Longitudinal Girder or a Transverse Frame. The Aft / Outboard Leg lands adjacent to the corner of two bulkheads, but on top of un-stiffened deck plating. Please note that the construction drawings (GFOE-2065) have been modified by adding a flat-bar stiffener below-deck which will stiffen the soft-plate.

Please see the hand-calculations provided in Figure 8. This conservative beam-theory calculation provides a validation that bending stress in the Longitudinal Girder under the

Forward/ Inboard mast leg is well below the allowable stress for Grade A steel. A simple calculation, assuming free-ends, results in a bending stress of 13.7 ksi. As the ends of this girder are substantially bracketed, the bending stress will be much lower, as evidenced in results of the

FEA model.

b. Also, please submit detail of the global model that was constructed including the boundary conditions and summary of the elements used.

We have included more detail concerning the FEA model in the document above. We also altered the extent of the model as requested. The inboard edge of the 02 deck is now bounded by a heavy Longitudinal Girder. Please see pgs 7-8 above.

c. It should be noted that the upper deck in the considered area also provides foundation for the traction winch. The loads from the traction winch should be included in your analysis as a combined load which will induce additional stress on the ship structure. The design deck head should also be included as a combined load as well as any other potential occasional combined load due to ROV hangar ops.

There is a Markey CTD winch located to Starboard of the region of interest. The winch is bounded by heavy structure. While it is possible that some bending stress could be introduced into Frame 83 while operating the winch, this would never occur at the lifetime-extreme loading condition that is studied in the above document. Operation of the winch is limited to fair weather conditions. Most loading in the deck from the winch would be transmitted through the

Longitudinal Girder to Port of the winch, and the Longitudinal Bulkhead to Starboard of the winch. Below is a snip from OE-150-101, Sheet 3, Plan 19-B. The area of interest is highlighted.

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Global Foundation for Ocean Exploration 14

There are no other significant activities in this region of the 02 Deck resulting from ROV operations. Below the deck, a platform with two small hydraulic oil storage tanks is located adjacent to a small hydraulic power unit. Above deck, the ship's "Aft Control Console" is located with controls for operating the ship DP system and the ROV traction winch. The control console is situated between the two new Aft Mast Legs. See Figure 3 in the document above.

d. It is also noted that the aft port leg appears to land on the soft plate corner of the upper deck. This should be avoided without adding either an insert plate or underdeck stiffeners in order to avoid cracking due to cyclic fatigue loading.

This issue has been noted and an additional stiffener below the Mast-Leg has been added to

Drawing GFOE-2065. There is a 3 x 3/8" Flat bar and threaded deck-socket (OE-150-101, Detail

29-D), in close proximity to the soft decking. Adding a flat-bar stiffener under the deck will support the otherwise unsupported decking.

e. On a final note, although ABS does not publish design criteria for ship structure vibration, the natural frequency of the upper deck should be determined and the excitation frequency of the propeller and engine should be identified such that in can be concluded that resonance does not occur for the new installation.

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Global Foundation for Ocean Exploration 15

This issue was discussed by telephone on 7/13/17 with GFOE team (David Lovalvo, Karl

McLetchie, Todd Gregory), OMAO Project Manager (Hank Malcolm), and ABS Principle Engineer

(Daniel Lamere). The GFOE team agrees that the Okeanos Explorer does not exhibit any notable vibrations in the 02 deck region in any sea-state, at any ship speed, or at any heading relative to weather. We noted that the class of ship was built purposely for acoustic silence, so most machinery is well isolated from the hull. There does not appear to be any substantial resonance coupled with propeller RPM.

3) Is there a specific section of the ABS rules that we need to apply? If so, can ABS please guide us in the right direction?

a. No, there is not a specific section of the Rules that you need to apply. ABS is focused on the strength adequacy of the existing and/or modified ship structure to withstand the worst case loading of the mission equipment antenna. Adequacy is demonstrated by presenting the maximum resulting stresses in the ship structure from all considered load cases; each of these stresses are to be less than the allowable stress for the material under consideration.

b. The upper deck was reviewed by ABS during new construction for the intended design conditions at the time of construction and would have been reviewed again by

ABS each time the mission of the deck was changed if additional loading was incurred due to the change in mission.

Finally, as initially requested, the scantlings of the existing ship structure (bulkhead and deck plate and stiffeners) should be included in the assembly drawing showing the connection of the new mast to the upper deck. Alternatively, please submit the new construction drawings that show the scantlings of the upper deck plate and stiffeners iwo the new mast.

The scantlings of the existing ship structure are shown in drawing OE-150-101, which can be provided to ABS by NOAA OMAO. Additionally, the scantlings have been added to drawing

GFOE-2065

Please feel free to contact me if you have any questions or require additional clarification.

VR/ Daniel.

Daniel A. LaMere

ABS

Principal Engineer – Government Projects 1421 Prince St., Suite 100 | Alexandria, VA 22314 USA

Tel: 703-519-9236 | Fax: 703-519-9895 Email: dlamere@eagle.org | www.eagle.org

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