354-F399-01_Rev_4_Analysis_Report_112559977_112099023.pdf

USACE ESSAYONS

PEDESTAL CRANE INSTALLATION ANALYSIS

REVISIONS

REV SHEET DESCRIPTION DATE APPROVED

‐ ALL INITIAL ISSUE 2/19/19

1 ALL CHANGES PER MDC COMMENTS 3/19/19

2 ALL CHANGES PER MDC COMMENTS 4/4/19

3 ALL CHANGES PER ABS COMMENTS 4/30/19

4 ALL CHANGES PER ABS COMMENTS 5/10/19

DRAWING NO. REV SHEET NO.

354‐F399‐01 4 1

For Load Line Only

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USACE Essayons Pedestal Crane Installation Analysis

Table of Contents

Section: Page

1.0 References

2.0 Background

3.0 Method/Assumptions

4.0 Loads and Safety Factors

5.0 Results

6.0 Conclusion

Figures:

Figure 1 - Crane FE Model

Figure 2 - Crane FE Model � Under Deck Figure 3 � Fixed End Restraints on Model

Figure 4 � Crane Reaction Loads

Figure 5 � Crane Loads (lbs. and in.-lbs.) on Model Figure 6 � Buckling Output

Figure 7 - Von Mises Stress Contours � OSS

Figure 8 - Von Mises Stress 26.5 ksi Criteria � OSS Figure 9 - Von Mises Stress 26.5 ksi Criteria � OSS � Close

Figure 10 - Von Mises Stress Contours � AH36

Figure 11 - Von Mises Stress 36.2 ksi Criteria � AH36 Figure 12 - Von Mises Stress 36.2 ksi Criteria � AH36 � Access Opening

Figure 13 - Von Mises Stress Contours � COR-TEN O Figure 14 - Von Mises Stress Contours � COR-TEN B

Tables:

Table 1 - Allowable Stresses

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1.0 References:

1.1 Dwg. 354-F330-01 Pedestal Crane Foundation and Boom Rest

1.2 ABS Guide for Certification of Lifting Appliances

1.3 ABS Steel Vessel Rules 2019

1.4 NPCC GA-2218 � General Arrangement Drawing For Model: MCF-9583

1.5 Sun Dwg. 681-3291-102 � Pedestal Crane Fdn & Supporting Structure

2.0 Background:

A new main pedestal crane is being installed on the hopper dredge Essayons to replace the existing crane. The new crane is manufactured by North Pacific Crane Company (NPCC), model MCF-9583. The existing crane and ancillary equipment are located on the hopper top

(46�-6� ABL) on centerline between frames 74 and 78 with a boom rest at frame 49. The new crane and boom rest will be installed in the same location. The existing crane pedestal will be removed to below the deck and replaced with a new pedestal. This report addresses the structural requirements necessary for the installation of the new pedestal crane.

The crane pedestal is analyzed using four different load cases offset by 45 degrees to create a diagonal-aft lift, side lift, diagonal-forward lift, and forward lift. Loads in all cases are those provided in the �Crane Reaction Loads� section of Reference 1.4.

A separate analysis is used to evaluate the boom rest that supports the boom while it is stowed.

This analysis is to ensure that the structure of the boom rest is sufficient to handle the loads on the boom and ships motions. This analysis is included in Appendix A.

3.0 Method/Assumptions:

A finite element model (FEM) of the pedestal and surrounding area was developed based on Ref. 1.1 and 1.5. The structure was modeled in FEMAP Version 12.0.0, copyright © 2018

Siemens Product Lifecycle Management Software, Inc. The solver is Autodesk Nastran

Version 10.3.0.716, copyright © 2016 Autodesk, Inc. NASTRAN is a large-scale structural Finite Element Analysis package that is widely-used by industry for a variety of FEA solutions. The model is solved with a linear static analysis.

3.1 Model: The model consists of a section of deck with stiffeners between frames 74 and

78, and both the new pedestal above the deck and existing pedestal below the deck. The model consists of 2D PLATE elements representing the deck, stiffeners, frames, and pedestal. The mesh size is generally 4.6 inches (1/5th frame spacing) throughout the model. The model contains approximately 19,800 nodes and 19,200 elements. The coordinate system used throughout the modeling process matches the coordinate system used in the structural drawing. The X-axis is oriented longitudinally with positive forward, the Y-axis is oriented transversely with positive to port and the Z-axis is oriented vertically with positive upward from baseline. All units in the model are US units (in, lbs, sec, psi). Figure 1 and 2 show the crane pedestal structure.

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Figure 1 - Crane FE Model

Figure 2 - Crane FE Model � Under Deck

3.2 Boundary Conditions: In this FE model, nodes are constrained at the fore and aft extents (hopper ends) as well as port and starboard extents (18� OCL Bhd.). The bottom of the under-deck pedestal is also constrained.

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Figure 3 � Fixed End Restraints on Model

4.0 Loads and Safety Factors:

4.1 Loads: The crane pedestal is analyzed using four different load cases. The loading for all load cases are provided by the crane manufacturer (Ref 1.4). During analysis it was determined that each load case creates different areas of maximum stress; therefore, all four cases are investigated in each section of this analysis. The loads the crane puts on the pedestal are listed in Figure 4, below. Axial Thrust is in the negative Z direction and

Torque is about the positive Z direction. The orientation of the Radial Load is dependent the load case (forward, diagonal-forward, side, and diagonal-aft) and Overturning Moment offset 90° from the Radial Load in order to provide maximum total overturning moment.

Figure 4 � Crane Reaction Loads

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Figure 5 � Crane Loads (lbs. and in.-lbs.) on Model

4.2 Allowable Stress: The structure in the area of concern consists of four different materials. Allowable stress for all materials is 78% of yield per Reference 1.3. An additional 0.908 strength reduction is applied to the three high tensile steels used per

Reference 1.3. Maximum allowable stresses are shown in Table 1.

Table 1 - Allowable Stresses

Material Allowable Stress (PSI)

OSS 26,500

AH36 36,200

Existing COR-TEN O 33,300

New COR-TEN B 35,400

The stresses of concern in this analysis are von Mises stresses, which arise from distortion energy theory. The use of von Mises stresses is quite accurate in predicting failure of steel parts. Von Mises stresses shown throughout the report indicate the maximum of surface stresses on either side of the plate elements. The von Mises stress is defined as:

σ

Where σ1 and σ2 are the principal stresses.

All steel is modeled with a modulus of Elasticity (E) of 29,000 ksi, a Poisson�s Ratio

(ѵ) of 0.29, and a density (ρ) of 7.324 x 10-7 kips-s2/in4.

4.3 Buckling: An eigenvalue analysis was performed for each of the four load cases to find the factor of safety on the critical load for the first buckling mode of the

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Figure 6 � Buckling Output

5.0 Results:

The following stress plots show the von Mises stress results from the finite element analyses of the crane pedestal. For each material, only the highest stress load case is shown.

5.1 OSS Structure (Existing and New): The analysis model contains both existing and new

OSS. Figures 7, 8 and 9 show the von Mises stress plots of the crane pedestal and ship�s structure constructed of OSS. The stress contour scale ranges from 0 psi (magenta) to the OSS allowable stress of 26,500 psi (red).

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Figure 7 - Von Mises Stress Contours � OSS

Figure 8 - Von Mises Stress 26.5 ksi Criteria � OSS

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Figure 9 - Von Mises Stress 26.5 ksi Criteria � OSS � Close

There is one element above the allowable stress. While the stress in this element exceeds the general OSS stress allowable, it is a single element at a structural discontinuity and under the yield stress; therefore, the stresses are acceptable.

5.2 AH36 Structure (Existing and New): The analysis model contains both existing and new

AH36. Figures 10, 11, and 12 show the von Mises stress plots of the crane pedestal and ship�s structure constructed of AH36. The stress contour scale ranges from 0 psi

(magenta) to the AH36 allowable stress of 36,200 psi (red).

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Figure 10 - Von Mises Stress Contours � AH36

Figure 11 - Von Mises Stress 36.2 ksi Criteria � AH36

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Figure 12 - Von Mises Stress 36.2 ksi Criteria � AH36 � Access Opening

There is one element above the allowable stress. While the stress in this element exceeds the general OSS stress allowable, it is a single element at a structural discontinuity and under the yield stress; therefore, the stresses are acceptable.

5.3 COR-TEN O Structure (Existing): The analysis model contains existing COR-TEN O.

Figure 13 shows the von Mises stress plots of the existing ship�s structure constructed of COR-TEN O. The stress contour scale ranges from 0 psi (magenta) to the COR-TEN O allowable stress of 33,300 psi (red).

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Figure 13 - Von Mises Stress Contours � COR-TEN O

There are no elements that exceed the allowable stress; therefore, the stresses are acceptable.

5.4 COR-TEN B Structure (New): The analysis model contains both existing and new

COR-TEN B. Figure 14 shows the von Mises stress plots of the new foundation brackets constructed of COR-TEN B. The stress contour scale ranges from 0 psi (magenta) to the

COR-TEN B allowable stress of 35,400 psi (red).

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Figure 14 - Von Mises Stress Contours � COR-TEN B

There are no elements that exceed the allowable stress; therefore, the stresses are acceptable.

6.0 Conclusions:

This analysis demonstrates that the structural modifications detailed in Reference 1.1 are adequate to support the crane described in Reference 1.4 based on the guidance provided in

Reference 1.2. The structural stresses are less than the allowable for each variety of steel in both new and existing structure. There are a total of two individual elements that do not meet the stress criteria. Each case is a single element at a structural discontinuity and is deemed acceptable for those reasons.

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APPENDIX A: Boom Rest

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Wind Loads of Stowed Crane for Boom Rest Design

U.S. Army Corps of Engineers

Essayons Pedestal Crane

Chapter 2 Guide for Certification of Cranes

Section 2 Structural Requirements

5.19 Loads due to Wind

For crane wind area see Ref. 1.1.

Wind Velocity 100 kn 5.19.1

5.19.2 Provides a formula for calculation of wind pressure:

f is a constant given as 296

V is our wind velocity in knots 100 kn

C is a shape coefficient 1

C for a flat surface is from 2Ͳ2/Table 4

Wind load shall be calculated in accordance with ABS GUIDE FOR CERTIFICATION OF LIFTING

APPLIANCES 2018

For calculation of forces applied to the boom rest, we shall look at crane outͲofͲservice, boom stowed.

For added conservative modeling, the projected area will be taken as shown, outide of the actual area.

In order to be conservative, 1.0 will be used for all projected area of the crane rather than modeling cables, cylinders, and small parts seperately.

Figure A1 Ͳ Pedestal Crane Wind Area Model

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5.19.2 provides wind pressure, P, to be:

P 33.78 PSF

5.19.3 Provides an equation for the calculation of Horizontal wind force

We will assume that there is no additional live load, as the crane is stowed

A 142,158 Sq in

987 sq ft

HLwind 33,352 lbf

This is the horizontal wind load for the whole crane distance to centroid 411.36 in distance to boom rest 649 in

These distances are taken relative to the crane pedestal (pivot axis)

Wind moment about pedestal 13,719,626 inͲlbf

Horizonatal wind force on boom rest 21,140 lbf

5.21 Provides an equation for the calcuclation of loads due to list and trim

The manufacturer specifies 5 degrees of list and 2 degrees of trim

HLSIA 10,327 lbf

This is the horizontal list & trim load for the whole crane

Dwg. BRͲ22247 locates the COG of the crane assembly distance to centroid 205 in distance to boom rest 649 in

These distances are taken relative to the crane pedestal (pivot axis)

A is area which has been taken from the dashed line in the AutoCad model slightly outside of all objects

The AutoCad polyline has a centroid where the load is applied and a moment can be taken to the boom rest

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List & trim moment about pedestal 2,117,071 inͲlbf

Loads due to list & trim on boom rest 3,262 lbf

Total horizonatal force on boom rest HL 24,402 lbf

Though not required by ABS, ships motions are added to the wind load for the total load

Length between Perp. (LBP) = 333 ft

Breadth (B)

Depth (D)

Freeboard

Draft (d) = 28.5 ft

Frame Spacing

References:

DODͲSTDͲ1399 Section 301A, 1986

681Ͳ700Ͳ201 General Arrangement

354ͲC155Ͳ01 Trim and Stability Book

Ship Motion Loads Calculations at Sea State 8:

Accelerations based on Section 301A of DOD Interface Standard 1399 Ͳ Ship Motion and Attitude

GM = 5.87 ft Operational Lightship

Roll Period (Tr) = 10.67 sec Tr = (C x B) / (GM) 1/ ²

Pitch Period (Tp) Table

Max Roll Angle (Ɍ) = 0.785398 radians

Max Pitch Angle (ɽ) = 0.174533 radians

Acceleration due to Gravity (g) = 32.15 ft/sec²

Equipment Location:

X = Longitudinal Distance from Ship C.G.

Y = Transverse Distance from Ship C.G. (assume CL)

Z = Vertical Distance from Ship C.G. (assume Draft)

Calculation of Loading Factors

Ax = Loading Factor In Longitudinal Direction (Fore & Aft)

Ax = g sin(ɽ) + s g + 4ʋ²/Tp² * ɽ²X + 4 ʋ²/Tp² * ɽZ

Ay = Loading Factor In Transverse Direction (Athwartship)

Ay = g sin(Ɍ) + ½ * 4ʋ²/Tp² * ɽX + 4ʋ²/Tr² * Ɍ²Y + 4ʋ²/Tr² * ɌZ

Az = Loading Factor In Vertical Direction

Az = g ± (h g + 4ʋ²/Tp² * ɽX + 4ʋ²/Tr² * ɌY)

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Loading Factors

Equipment Locations Weight Mass X Y Z lbs lbsͲ

Boom Rest 2359 6.1 42.81 0 26.2

F(i) = W/g * A(i)

Equipment Loads Ax Fx Ay Fy Az Fz ft/sec² lbs ft/sec² lbs ft/sec² lbs

Boom Rest 14.9 1091.0 35.8 2625.3 32.2 2359

Allowable stress in OSS (Ref. 1.2) 25,600 psi

Figure A2 Ͳ Von Mises Stress Contour Ͳ ABS Horizontal + DOD Ship's Motions

The highest stresses element is the model sees 23,386 psi, which is less than the OSS allowable stress of 25,600 psi. There are no elements that exceed the allowable stress; therefore, the stresses are acceptable.

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Figure A3 Ͳ Buckling Output Ͳ ABS Horizontal + DOD Ship's Motions

An eigenvalue analysis was performed to find the factor of safety on the critical load for the first buckling mode of the structure. The factor of safety on the critical load is 8.0; therefore, buckling is not a concern for this structure.

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