ABS 77-1995 Safehull System for Bulk Carriers Guide on Improvement for Structural Connections and Sample Structural Details - Service Experience and Modifications - for Bulk Carrie.pdf

1、ABS #77 95 m Ob51102 001121b 724 m AMERICAN BUREAU OF SHIPPING 8 AFFILIATED COMPANIES SAFEHULL SYSTEM FOR BULK CARRIERS GUIDE ON IMPROVEMENT FOR STRUCTURAL CONNECTIONS AND SAMPLE STRUCTURAL DETAILS FOR BULK CARRIERS QERVICE EXPERIENCE AND MODIFICATIONS- OCTOBER i995 SAFEPI OF SHIP STRUCTURES BY DYNA

2、MIC EASED DESIGN AND EVALUATION ABS #77 95 I Ob51102 0011217 660 = ABS #77 95 W Ob51102 001121B 5T7 W FOUNDED 1862 - AMERICAN BUREAU OF SHIPPING, I AFFILIATED COMPANIES Guide on Improvement for Structural Connections and Sample Structural Details - Service Experience and Modifications - for Bulk Car

3、riers October 1995 American Bureau of Shipping Incorporated by the Legislature of the State of New York 1862 Copyright Q 1995 American Bureau of Shipping Two World Trade Center, 106th Floor New York, NY 10048 U.S.A. ABS #77 95 M Ob51102 00112L9 433 M 1.0 GENERAL This Guide identifies the influential

4、 parameters and provides guidelines on improvement of structural connections. It also provides for reference illustrations of local structural failures experienced in some existing bulk carriers and the corrective measures as compiled by the IACS and from the American Bureau of Shippings data files.

5、 For structural details similar to those in tankers, reference illustrations are to be found in the “Guide on Improvement for Structural Connections and Sample Structural Details - Service Experience and Modifications - for Tankers”. 2.0 INFLUENTIAL PARAMETERS For design of structural details, due c

6、onsideration is to be given to the following influential parameters. 2.1 Loading Patterns and Nominal Stresses The load distribution among the connected structural members and the corresponding nominal stresses at the location considered should be examined for the combined load cases specified in 5/

7、3A3.5.2. It is important to consider the combined effects of all the simultaneously imposed load components, rather than only one selected dominating load component. The stress distribution may be obtained from a 3D structural analysis as specified in 5l3A5.3 or by other equivalent means. 2.2 Stress

8、 Concentration Due to load transmission and diffusion at a structural joint, it is inevitable that some form of stress concentration is going to occur in the loaded structure. Therefore, particular attention should be paid to structural notches, abrupt changes in structural properties and excessive

9、distortions and deformations; such as locations at bracket toes, cut-outs, terminations of heavily loaded members, connection of flexible elements with much stiffer members, ends of unbalanced structural members, just to name a few. For ship structures 1 ABS #77 95 Ob51102 O011220 155 = designed wit

10、h relatively low working stresses and high safety margins, the detrimental effects of such stress concentrations may not readily be apparent. On the other hand, for structures designed with high working stresses and low safety margins, damaging effects of such stress concentrations could appear soon

11、er than the anticipated period of time. Appropriate stress concentration factors (SCFs) obtained from either experimental data or structural analyses are required to evaluate the design of structural details. 2.3 Weld Effects and Fatigue Strength Another important factor to be considered is the effe

12、cts of welding on the properties of material (heating effects) and on structural continuity (profile of the weld deposit and under- cuts). This factor which highly depends on the welding methods, processes and workmanship is vital for assessing fatigue strength of the joint. To date, the welding eff

13、ects on fatigue strength are primarily determined by experimental data presented in the form of S-N curves and characteristics of the test specimens, as shown in Appendix 5/3AA of the Rules. 3.0 CONSIDERATIONS FOR DESIGN OF STRUCTURAL DETAILS In light of the discussions given in 5/3A5.4, it is appar

14、ent that the necessary criterion for the design of structural details is simply to offer a well balanced joint which is “compatible“ with the anticipated working stresses. To this end, the solution is to be tailored to a specific location of a specific design. In addition, there is no unique solutio

15、n to the problem. Many alternatives may exist. The designerdbuilder would have to exercise their judgment based on their fabrication facilities, techniques and experience. The information offered below is provided for reference. 3.1 Hold Frames and End Brackets When selecting and sizing brackets con

16、necting hold frames, due consideration should be given to the load transmission and relative stiffness of the members to be connected. A 2 ABS #77 95 I Ob5LL02 OOLL22L 091 I pattern of smooth load transmission is essential. The connecting bracket is to be of sufficient size to withstand the highly c

17、oncentrated loads and to relocate the critical spots (bracket toes) to lower stressed regions. Sample illustrations are shown in Figures i, 1 a and 1 b for damages experienced in existing bulk carriers with some recorded repairs. 3.2 Connection of Transverse Bulkhead Structures To prevent local frac

18、tures and to minimize the magnifying effects of structural notches, and misalignmentidiscontinuities consideration should be given to local reinforcements at the criiical areas. Sample illustrations are shown in Figures 2a thru 2f for local damages and some recorded repairs. 3.3 Connection of Double

19、 Bottom Structures Sample damaged structural details and connections are illustrated in Figures 3a thru 3h for double bottom structures. Attention should be paid to the weld connections of the slope longitudinal bulkhead and the inner bottom plating. 3.4 Connections of Lower Wing Tank Structures Sam

20、ple damages experienced in the existing bulk carriers are shown in Figures 4a and 4b. 3.5 Structures and Connections Within the Upper Wing Tanks Sample fractures and buckling of the transverse webs and brackets are shown in Figures 5a thru 5d. 3.6 Deck Structures Illustrations are given for cracks a

21、t hatch corners, buckling of the cross deck structures and hatch coaming in Figures 6a thru 6d. 3.7 Forepeak Structures Some structural damages are shown in Figures 7a and 7b for the supporting structures in the forepeak region. 3.8 Transition Region in the Foremost Cargo Hold Sample structural dama

22、ges and repairs are shown in Figures 8a thru 8d for connections of the panting stringers and hold frames. 3 ABS #77 95 Ob51102 O011222 T28 Side Frame Structure Typical Damages to Hold Frames opside tank w Separate Bracket Configuration (4 integral Bracket Configuration The type of bracket configurat

23、ion used will to a large extent dictate the location and extend of fracture. Where separate brackets are employed, the fracture location is normally at the bracket toe position on the frames, whereas with integral brackets the fracture location is at the toe position on the hopper and topside tank.

24、Figure 1 4 ABS #77 95 = 0653302 OOLL223 964 Oetaii of damage Fractures at brackets toe position on the frame Sketch of damage Side A shell J Separate Bracket Configuration Sketch of repair Modified brackets 0.3Y Y Figure lai 5 ABS #7 95 Oh53302 003122Li BTO = Detail of damage Side Frame Structure 7

25、Fractures on brackets at termination of frame I Sketch of damage Side A shell Fractutes + Y t Separate Bracket Configuration Sketch of repair 3x Side shell S = Smped end Modified brackets 0.3Y Y Figure la2 6 ABS #77 95 m Ob51102 0011225 737 m Side Framing - - Side Frame Structure Detail of damage Fr

26、actures and the Toe Position on the Side Tank Sloping Plating Sketch of damage Figure 1 b Sketch of repair 1 Main frame Detaii *As modied“ View “XX Hopper WeId throat 3 0.44 x 1.4t - ABS #77 95 W Ob51102 0011226 b73 Shedder i Fractures on web of corngation initiating at intersection of adjacent shed

27、der plates Fractures initiating at b. the comers of the shedder plate connections to the shelf plate and corrugations Fractures initiating at connections to side Fractures initiating at connections of stoohopper sloping plating Fractures initiating at the weld of corrugations to shelf plate and /or

28、stool sloping plating to shelf plate the connections of the stool sloping plating to the inner bottom (Similar damages may occur at the upper connections of the bulkhead to the deck structure) Figure 2 Typical Fracturing at the Connection of Transverse Bulkhead Structure 8 ABS #77 95 m Ob53302 00332

29、27 50T m Detail of damage Transverse Bulkhead Structure Fractures at weid connections to stoa1 chei plate 1 Sketch of damage Bulkhead COgatiOn Fr; in Fillet weid Shelf plate e Weld fracture / Stoolsloped I Fractures phting . Sketch of repair n Edges prepared and II full penetration welded, New shelf

30、 plate insert of increased iicknes 1 New phte of ir, is ndication of buckling X = extent of cdlar depending on mking direction Figure 2a 9 Transverse Bulkhead Structure Detail of damage Fractures at weld connections of stmi plating and corrugation flange to the shelf plate Sketch of damage 8ulkh.d m

31、aatm Figure 2b Sketch of repair Edges prepared and full penetration welded, using low hydrogen electrodes or equivalent / / Stmcture to be reieased and mdigment rectified Transverse Bulkhead Structure Detail of damage Fractures at the upper boundaries to topside tanks Sketch Of damage Fracture ) Top

32、side tank , - c Sketch of repair Continucus or intercostal reinforcement in be with flanges or diaphragms where not already fitted I Adjacent to the topside tank either a diaphragm oc a bulb plate stiffener may be incworated / Diaphragm (sirniiar diaphragms on the opposite side shown dotted) Figure

33、2c II ABS #77 95 m Ob5LL02 0011230 OT4 m 3etail of damage Transverse Bulkhead Structure Fractures on the web of corrugation initiating at intersection of adjacent shedder plates I Sketch of damage I: L Transverse bulkhead / / Side shell frame Tank top/ / inner bottom Sketch of repair 1 r-nQq I I-+,

34、I I Flat bar extension piece fitted at corrugations with overlap connections at ends Section *A-A* Figure 2d Transverse Bulkhead Structure I Detail of damage Fractures at welded connection of lower stool plating to tank top in way of duct keel I I Sketch of damage A Fracture Fractures Bulkhead stool

35、 Sketch of repair It may be necessary to crop and insert ia the tank tognner bottom phtulg Insert plate of increased thickness and/or enhanced grade# Duct keel bottom Full penetration YUS i U Fillet weld of DB OTM qirder to be made full Section penetraron over bgth of stool space section 8-8 Figure

36、2e 13 ABS #77 95 m 0653302 OOLl1232 977 m Transverse Bulkhead Structure Detail of damage Indentation and buckling of vertical corrugations Sketch of damage 51 I Bending or compressive buckling !I !I Sei etate Lower stool Tank tophm botlm sketch of repair Pbtjng part renewed I 1 !I !I jl Shelf plate

37、I Lower stool Tank top/inner bottom I Figure 2f 14 Figure 3 Typical Fractures in the Connection of Hopper Plating and Tan kto plln n er botto rn 15 ABS #77 95 W Ob51102 0011234 74T = Detail of damage Double Bottom Structure Fracture at weid connection of floors in way of hopper/ tank top / Floor or

38、transverse I interface I Fractures in the ffoodweb of hopper transverse ring I Sketchofdamage Side girder Figure 3a Sketch of repair Full cenetrathl wdd uea of high stress 12.3 represents sequence of welding /Tank top/iiner C k bottom plating Floor or Edge chamfered for full penetration weld Collar

39、plate web plating Reinforcement Additional StiffenH Section 6 -6 ABS # 75 m Ob53302 0033235 bBb m / Fk or transverse webpiating Double Bottom Structure Fractures in the floodweb of hopper transverse ring I Detail of damage fiaauring at weld connection of floors in way of hopper tank and tanktophner

40、bottom interface Sketch of damage sketch of repair hitar piate with iuii penetration weld mnection to tanktop/ rnner bottom, happer plating, and bottom girder secum A -* for full penetratiori WeM Reinforcement A Atematiiety, $ Intermediate brackets (ie my stop at between floors) longitudinais where

41、fed , Reinforcement B of transverse brackets =ma scarfing Web Figure 3b 17 ABS #i? 95 Ob53302 0011236 512 I Double Bottom Structure Edge chamfered for hull petration weld I I Detail of damage Fractures at Weld connections of ROWS in Way of Tank fop/inner bottom and side girder in Way of stool plates

42、 I Sketch of damage Ci. or side girder Sketch of repair Cequene of welding is important Stool plate d 1, 2and3 CL or side girder Floor View A represent welding Side eleva tion r View A Figure 3c 18 ABS #77 95 0651102 0033237 459 W Double Bottom Structure Detail of damage Fracturing of bottom shell a

43、nd tanktop/inner bottom longitudinals in way of tank top/inner bottom and bulkhead stool boundaries I Sketch of damage Sketch of repair Figure 3d 19 Double Bottom Structure Detail of damage - Fracturing of Longitudinais in Way of Bilge Well I Sketch of damage Tank top/rnner bottom Fracture Sketch of

44、 repair Tank topfinnef bottom Figure 3e ABS #77 95 Ob5LL02 0011239 221 Double Bottom Structure Detail of damage 1 Fractures at welded boundaries of the floor stiffener (heel) to both bottom shd and tank top longitudinals Sketch of damage Bottom shell Note : same damage may occur at simiiar annection

45、s on tank top Sketch of repair Bracket with soft Stiffener toes fitted (fiilet welded) it is recommended that the cutout for the purpose of fabrication (rathole) in the stiffener ts designed as shown cutout Figure 3f ABS #77 7.5 0651102 O011240 T43 Double Bottom Structure Detail of damage Fractures

46、at welded boundaries (toe) of the floor stiffener to both bottom sheii and inner bottom lonptudinals Sketch of damage II Stiffener I L- Bottom shell Note : same damage may occur at similar connections to inner bottom Sketch of repair Repair (a) ,d Where required the longitudinal to be cropped and pa

47、rt renewed Repair (b) + 50 mm ma. Notes on repairs Repair (b), where the stiffeners are unconnected to the longitudinais and offset from them, is to be incorporated after approval by the classification Soaety concerned. Lugs and/or coliars may be necessary at the cutouts in the floor for passage of

48、longitudinals. . Figure 39 22 Double Bottom Structure Fractures and budding in way of a cutout for the passage of a IongitudinaI through a transv- primay manber I Sketch of damage f Note : same damage may occur at similar connections on tank top Sketch of repair RepaVA Lug introduced New floor enhan

49、ced thickness plating of - n Repair B ,-il- I 1 ,- - -. CqT Full collar plate I I I I I I I I I I I I I I Figure 3h 23 ABS #77 95 D Ob51102 0011242 816 D Detail of hge Hopper Tank Structure Fracturing of hopper longitudinal at boundary with transverse web L I sketch of damage 7 h / F& sketch of repair Bracket partly renewed toincorpora te soft toe Figure 4a ABS #77 95 = 0653302 0033243 752 W Detail of damage Hopper Tank Structure Fractures at