1 / 18

Eng. 6002 Ship Structures 1 Hull Girder Response Analysis

Eng. 6002 Ship Structures 1 Hull Girder Response Analysis. Lecture 3: Estimation of weight distribution and still water bending moment. Overview. A method for determining the distribution of buoyant forces was described in the previous lecture.

vito
Download Presentation

Eng. 6002 Ship Structures 1 Hull Girder Response Analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Eng. 6002 Ship Structures 1Hull Girder Response Analysis Lecture 3: Estimation of weight distribution and still water bending moment

  2. Overview • A method for determining the distribution of buoyant forces was described in the previous lecture. • Today we will look at a method for estimating the distribution of weight along the ship. • We will also discuss still water bending moments

  3. Estimation of Weight Distribution For ships with parallel middle body (cargo ships) • If the weight distribution is unknown and we need to estimate the distribution, the Prohaska method can be used • The weight distribution is a trapezoid on top of a uniform distribution

  4. Estimation of Weight Distribution cont. The weights are distributed as shown, with:

  5. Estimation of Weight Distribution cont. • Note that since a and b average to we can say:

  6. Estimation of Weight Distribution cont. • To move the lcg, the fore and aft ends of the load diagram must be adjusted by equal and opposite amounts

  7. Longitudinal Strength of Ships:Murray’s Method for SWBM Although computer methods have emerged as a practical way of calculating the still water bending moment, it makes sense to discuss Murray’s Method for hand calculations • Based on the idea that forces and moments in a ship are self balancing (no net forces transferred to world)

  8. Longitudinal Strength of Ships:Murray’s Method for SWBM • He proposed that any set of weight and buoyancy forces are in balance

  9. Longitudinal Strength of Ships:Murray’s Method for SWBM • Furthermore, for any cut at x, the moment at the cut can be determined by:

  10. Longitudinal Strength of Ships:Murray’s Method for SWBM • Applying this idea to a ship

  11. Longitudinal Strength of Ships:Murray’s Method for SWBM • The bending moment at amidships is: • The estimate of max bending moment can be improved by averaging these

  12. Longitudinal Strength of Ships:Murray’s Method for SWBM • The bending moment at amidships is: • We can simplify the buoyancy part by:

  13. Longitudinal Strength of Ships:Murray’s Method for SWBM • Murray suggested a set of values for the average moment arm, as a function of ship length,CB, and the ratio of draft to length

  14. Example using Murray’s Method • Tanker with L = 278m, B=37m, CB=0.8

  15. Example using Murray’s Method • To find BMB we need the draft • So T/L = 16.68/278 = 0.06

  16. Example using Murray’s Method • Murray’s table gives a=0.179 and b=0.063 • And the buoyancy bending moment is

  17. Example using Murray’s Method • The still water bending moment is then • Assuming the wave bending moments are: WBMsag=583800 t-m and WBMhog=520440 t-m

  18. Example using Murray’s Method • The total bending moment is

More Related