WELCOME: EXCEL ENGINE FOR SHIP CARGO ACCELERATIONS

Transcription

1 WELCOME: EXCEL ENGINE FOR SHIP CARGO ACCELERATIONS What this Excel Sheet does This excel sheet calculates the accelerations on a Cargo being carried by a ship a. Accelerations due to ship motions: It calculates the accelerations due to the ship's roll,pitch and heave, depending on the size of the cargo and size of the Vessel, in accordance with Nobledenton Guidelines b. Wind Loads: It also calculates the wind loads coming onto the Cargo in accordance with the ABS Rules for MODU b. Final Accelerations: It also calculates the final accelerations due to motions + wind loads and reports the accelerations in Longitudinal, Transverse and Vertical Directions in terms of 'g' Directions for Use 1. All the cells which require input are in the Worksheet 'Inputs' and have blue background. Please fill only input cells, i.e., ones with blue background. Leave the other cells untouched, as they are output cells 2. Fill in the inputs in the Worksheet 'Inputs' 3. Once the 'Inputs' sheet is completed, accelerations will be automatically calculated in the Worksheets 'Motion Forces' and 'Windloads' and reported in the 'Final Accelerations' worksheet. Assumptions 1. Cargo areas are taken considering it as a rectangular box 2. The standard motion criteria of Nobledenton are assumed to apply 3. Unrestricted Operation is assumed (Open Sea Condition) 4. The cargo's own moment of inertia is ignored. Cargo is considered as a point mass. Thus this spreadsheet should be used carefully with cargo of big sizes which may have substantial self moment of inertia 5. Phase differences between forces are ignored. This leads to conservative results 6. The forces are resolved in the following directions : Vertical - perpendicular to deck. Transverse- parallel to deck in transverse direction, Longitudinal - parallel to deck in longitudinal direction References 1. Nobledenton Guidelines for Marine Transportation (0030-ND)Rev 5, June ABS RULES FOR BUILDING AND CLASSING MOBILE OFFSHORE DRILLING UNITS, 2001, C 3-1-2/

2 Page 2 of 9 CARGO FORCES AND ACCELERATIONS General Particulars Cargo Particulars Particular Value Units Particular Value Units Spherical 0.40 Acceleration due to Gravity g m/s 2 ITEM Name Cargo 1 Cylindrical Shapes (all sizes) used for crane pedestals, booms, helidecks, etc Density of air ρ air 1.23 kg/m 3 Weight M MT Hull, based on block projected area 1.00 Vessel Particulars Weight Contingencies(factor) f 1 - Deck houses 1.25 Shape Shape factors for wind calculations Length l 28.4 m Clusters of deck houses and other structures, based on block projected area 1.20 Particular Value Units Width w 27.8 m Isolated structural shapes (e.g., cranes, angle channel beams, etc.) 1.30 Vessel Name Barge 1 Height h 72.5 m Under deck areas (smooth) Overall Length L m Longitudinal Distance of Cargo COG from Midship Xcg 0 m Under deck surface (exposed beams and girders) 1.40 Transverse Distance of Cargo COG from Overall Breadth B m Vessel Centerline Ycg 0 m Rig derrick, each face, assuming fabricated from angle Overall Depth D 5.50 m Vertical Distance of Cargo COG from Vessel Deck Zd 40 m Table 1: Cargo Shape Coefficients 1 Draft (Motion Centre)* T 2.10 m Cargo Shape Coefficient(Front)** Csf 1 Block Coefficient C B Cargo Shape Coefficient(Side)** Css 1 1 Source: ABS Rules for Building and Classing Environment Criteria ** See Table 1 on the right for Shape Coefficients Mobile Offshore Drilling Units, 2012, C 3-1-2/1.3.2 Cs Particular Value Units Wind Speed V wind 8.20 m/s *Motion Centre is assumed at the height of Waterline vertically

3 Page 3 of 9 Motion Forces Calculation Cargo Details Parameter Nomenclature Value Units Cargo Name Cargo 1 Design Weight W = M x f MT Distance of CoG from Centre of Rotation* Longitudinal Distance from Centre of Rotation Xcg 0.00 m Transverse Distance from Centre of Rotation Ycg 0.00 m Vertical Distance from Centre of Rotation Zcg = Zd + D - T m *The Centre of Rotation is assumed located at Midship Longitudinally, Centreline Transversely and Waterline Vertically Design Conditions (from Nobledenton) 1 Vessel L/B Ratio R LB Roll Angle Фroll 20 deg. Time Period Troll 10 s Pitch Angle Фpitch 12.5 deg. Time Period Tpitch 10 s Heave Period Theave 10 s Heave acceleration a heave 1.96 m/s 2 1 Source: Nobledenton Guidelines for Marine Transportation (0030-ND), Rev 5, June 2013, Sec 7.9.1

4 Page 4 of 9 FORCES A. STATIC FORCES A.1 ROLL FORCES 1. Vertical Force = WCosФroll 1. Vertical Roll Force (Static) F ZRS WCosФroll = MT 2. Horizontal Roll Force (Static) F YRS WSinФroll = MT A.2 PITCH FORCES 1. Vertical Force (Static) F ZPS WCosФpitch = MT 2. Horizontal Force (Static) F XPS WSinФpitch = MT B. DYNAMIC FORCES B.1 ROLL FORCES 1. Vertical Force F ZRD W*4*π 2 *Ycg*Фroll/(Troll 2 *g) = 0.00 MT 2. Horizontal Force F YRD W*4*π 2 *Zcg*Фroll/(Troll 2 *g) = MT B.2 PITCH FORCES 1. Vertical Force F ZPD W*4*π 2 *Xcg*Фpitch/(Tpitch 2 *g) = 0.00 MT 2. Horizontal Force F XPD W*4*π 2 *Zcg*Фpitch/(Tpitch 2 *g) = T B.3 HEAVE-ROLL FORCES 1. Vertical Force F ZHRD W*a heave *Cos(Фroll)/g) = T 2. Horizontal Force F YHRD W*a heave *Sin(Фroll)/g) = T B.4 HEAVE-PITCH FORCES 1. Vertical Force F ZHPD W*a heave *Cos(Фpitch)/g) = T 2. Horizontal Force F XHPD W*a heave *Sin(Фpitch)/g) = T

5 Longitudinal Transverse Company Name: Page 5 of 9 Maximum Motion Forces in Longitudinal and Transverse Directions Direction Formula Force Units Transverse, F TM F YRS +F YRD +F YHRD MT Longitudinal, F LM F XPS +F XPD +F XHPD MT Combined Vertical Forces Direction Case Heave Direction Formula Force Units Roll to Starboard Heave Down F ZRS + F ZRD + F ZHRD MT Roll to Starboard Heave Up F ZRS + F ZRD - F ZHRD MT Roll to Port Heave Down F ZRS - F ZRD + F ZHRD MT Roll to Port Heave Up F ZRS - F ZRD - F ZHRD MT Pitch to Fwd Heave Down F ZPS + F ZPD + F ZHPD MT Pitch to Fwd Heave Up F ZPS + F ZPD - F ZHPD MT Pitch to Aft Heave Down F ZPS - F ZPD + F ZHPD MT Pitch to Aft Heave Up F ZPS - F ZPD - F ZHPD MT

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7 * Source: ABS Rules for Building and Classing Mobile Offshore Drilling Units, 2012, C 3-1-2/ Windload Calculation* Page 7 of 9 Cargo Length = 28.4 m Cargo Width = 27.8 SIDE Cargo Height 72.5 m FRONT Vessel Depth 5.5 m Vessel Length OA = 86 m Vessel Width = 27.5 F WX = 1/2*ρ*V wind 2 *Σ (A T *C SF *Ch) (Wind Force in Longitudinal direction) F WY = 1/2*ρ*V wind 2 *Σ (A L *C SS *Ch) (Wind Force in Transverse direction) ρ = Density of Air, V wind = Wind Speed, A T = Cargo Transverse area exposed to Wind, A L = Cargo Longitudinal area exposed to Wind, Cs = Cargo Shape Coefficient, Ch = Cargo Height Coefficient* Ch is different for the parts of cargo falling in different height zones as per Table 1 below Basic Parameters Particulars Notation Value Units Cargo Name Cargo 1 Cargo Length l 28.4 m Cargo Width w 27.8 m Height of Cargo Bottom from BL H1 5.5 m Height of Cargo Top from BL H m Cargo Shape Coefficient (Front) C SF 1 *Please see Table 1 in Worksheet "Input" for shape coefficient Cargo Shape Coefficient (Side) C SS 1 Density of Air ρ MT/m 3 Wind Speed V wind 8.2 m/s Cargo Height Coefficients (Based on Height from Vessel Baseline) Zone Height from (m) Height to (m) Ch (Height Coefficient) Zone Zone Zone Zone Zone Zone A T (Cargo Transverse Area Exposed to Wind) F WX (Wind Force in Longitudinal Direction) CARGO A L (Cargo Longitudinal Area Exposed to Wind) F WY (Wind Force in Transverse Direction) DECK Area Height from Height to Ch Area Transverse, A T Area Longitudinal, A L A T *Ch*C SF A L *Ch*C SS Item (m) (m) (-/-) (m2) (m2) (m2) (m2) Zone Zone Cargo Height Coefficients ( Based on Height from Waterline) Zone Zone Height from (mheight to (m) Ch (Height Coefficient) Zone Zone Zone Zone Zone Zone Zone Total Factored Windage Area Σ (A T *Ch*C SF ) Σ (A L *Ch*C SS ) Zone Zone Table 1: Wind Pressure Height Coefficients 1 Wind Force in Longitudinal direction Wind Force in Transverse direction Cargo Areas in Transverse and Longitudinal Direction Factored for Height Coefficient Ch WINDLOAD F WX = 1/2*ρ*V 2 wind *Σ (A T *C SF *Ch) F WY = 1/2*ρ*V wind 2 *Σ (A L *C SS *Ch) MT MT 1 Source: ABS Rules for Building and Classing Mobile Offshore Drilling Units, 2012, C 3-1-2/1.3.2

8 Final Forces and Accelerations FORCES ACCELERATIONS Forces - Transverse Direction Final Accelerations(Motion + Wind) Force Value Units Direction Value Units Transverse Motion Force, F TM MT Longitudinal (Max.), a Lmax g Transverse Wind Load, F TW MT Transverse (Max.),a Tmax g Total Transverse Force, F T MT Vertical (Max.),a Vmax g Vertical (Min.),a Vmin g Forces - Longitudinal Direction Force Value Units Longitudinal Motion Force, F LM MT Longitudinal Wind Load, F LW MT Total Longitudinal Force, F L MT Forces - Vertical Direction Force Value Units Maximum Vertical Force, F VMAX MT Minimum Vertical Force, F VMAX MT Page 8 of 9

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