船舶工程外文翻譯---船舶結(jié)構(gòu)安全性和可靠性

1、<p>　　中文3800字,2300單詞，1.3萬(wàn)英文字符</p><p>　　出處：Paik J K, Frieze P A. Ship structural safety and reliability[J]. Progress in Structural Engineering and Materials, 2001, 3(2):198–204.</p><p><b

2、>　　外文翻譯</b></p><p>　　Ship structural safety and reliability</p><p>　　J K Paik 1 and P A Frieze 2</p><p>　　1 Pusan National University, South Korea</p><p>　　2 P

3、AFA Consulting Engineers, UK</p><p><b>　　Summary</b></p><p>　　Recent research and development in the area of design methodologies related to safety and reliability of ship structures

4、 is reviewed, focusing on some relevant probabilistic approaches used for the load and resistance factor design (LRFD) of ship hulls against collapse. Important insights and findings previously obtained in the literature

5、 are summarized, and recommendations are made with respect to both technologically improved design procedures and those needed for future development.</p><p>　　Key words: </p><p>　　ship structur

6、al safety; ship structural reliability; load and resistance factor design; ship hull collapse; probability-based ship structural design; hull girder load; hull girder strength; ultimate limit state; ultimate strength; ta

7、rget reliability.</p><p>　　Hull girder collapse accident</p><p>　　Overall collapse of ships’ hulls rarely occurs in still water or in waves. Fig. 1 shows a Cape size bulk carrier that recently c

8、ollapsed during discharge in port of her 126 000 t of iron ore cargo. While the 23-year-old 139 800 dwt ship has not broken in two, her mid-section is reportedly lying on the seabed, indicating that the hull girder has,

9、in fact, completely collapsed. After having emptied the bow and aft holds among five cargo holds, buckling collapse took place in the vessel’s deck whil</p><p>　　Fig. 1 A ship hull collapse during unloading

10、of cargo at port</p><p>　　(Courtesy of Lloyds List)</p><p>　　A ship hull in the intact condition will clearly sustain applied loads smaller than the design loads, and in normal sea and loading c

11、onditions it will not suffer structural failure such as buckling and collapse, except for possible localized yielding. However, the loads acting on the ship hull are uncertain, owing to rough seas or unusual loading/unlo

12、ading of cargo. In these cases, applied loads may exceed design loads and the ship hull may collapse globally. Furthermore, since aging ships may s</p><p>　　Probability-based structural design procedure</

13、p><p>　　The main steps for probability-based ship structural</p><p>　　design are normally as follows:</p><p>　　● establish a target reliability;</p><p>　　● identify all

14、unfavorable failure modes of the structure;</p><p>　　● formulate the limit state function for each failure mode identified above;</p><p>　　● identify the probabilistic characteristics (mean, v

15、ariance, distribution) of the random variables in the limit state function;</p><p>　　● calculate the reliability against the limit state with respect to each failure mode of the structure;</p><p&

16、gt;　　● assess if the predicted reliability is greater than the target reliability, and redesign the structure otherwise;</p><p>　　● evaluate the reliability analysis results with respect to parametric sens

17、itivity considerations.</p><p>　　Modelling of hull girder strength</p><p>　　Four types of limit state can be considered: namely, serviceability limit state, ultimate limit state, fatigue limit s

18、tate and accidental limit state . The serviceability limit state involves deterioration of less vital functions including:</p><p>　　● local damage which may reduce the durability of the structure or affect

19、the efficiency of structural or non-structural elements;</p><p>　　● unacceptable deformations which affect the efficient use of structural or non-structural elements, or the functioning of equipment;</p&

20、gt;<p>　　● excessive vibrations which cause discomfort to people or affect non-structural elements, or the functioning of equipment. </p><p>　　The ultimate limit state represents the collapse of the

21、structure, from factors such as:</p><p>　　● loss of equilibrium of the structure or part of the structure, considered as a rigid body (e.g. over turning or capsizing);</p><p>　　● attainment of

22、the maximum resistance capacity of sections, members or connections by gross yielding, rupture or fracture;</p><p>　　● instability of the structure or part thereof, such as by buckling of columns, plates, s

23、hells and stiffened panels.</p><p>　　The fatigue limit state results from damage accumulation under the action of cyclic loads and the accidental limit state is due to accidents such as collisions or groundi

24、ng.</p><p>　　Overall failure of ship hull girders, which rarely occurs, is normally governed by buckling and plastic collapse of the deck, bottom or sometimes the side shell stiffened panels. Failure of deck

25、, bottom or side shell stiffened panels can then lead to progressive collapse and ultimate hull girder failure. For many years, ship structural researchers have been working towards the goal of reliability-based limit st

26、ate design of ship structures. However, reliability-based design requires calculation </p><p>　　A number of studies on the ultimate collapse strength of ships’ hulls have been undertaken theoretically, numer

27、ically and experimentally . Some of the results have been reviewed by the ISSC Technical Committee III.1 on ‘Ultimate Strength’. The ultimate strength reliability of ships’ hulls, considering existing local damage relate

28、d to corrosion, fatigue and collision/grounding, has also been studied.</p><p>　　Previous studies on the development of a formulation for ultimate hull strength prediction may be classified into three groups

29、. The first is a linear approach, where the behaviour of the hull up to failure of the compression flange is assumed to be linear elastic, i.e. ignoring buckling, and the ultimate moment capacity of the hull is basically

30、 expressed as the ultimate strength of the compression flange multiplied by the elastic section modulus, with a simple correction for buckling and yieldin</p><p>　　The first approach is quite simple, but its

31、 accuracy is usually wanting because, after buckling of the compression flange, the behaviour of the hull is no longer linear, and the neutral axis changes position. Empirical formulations (the second approach) may provi

32、de reasonable solutions for conventional hulls, but one has to be careful in using empirical formulations for new and general-type hulls, since they are usually derived on the basis of limited data, or for a particular h

33、ull form, using a</p><p>　　The ship hull ultimate strength formula is eventually expressed as a function of design parameters related to geometric and material properties including plate thickness, yield str

34、ength and Young’s modulus. When time-variant structural degradation (e.g. corrosion) is considered, the value of member thickness at any particular time is a function of such damage. In probability-based design methods,

35、all the design parameters are treated as the random variables. The hull ultimate strength formula fo</p><p>　　Limit state function</p><p>　　Mathematically, the limit state function for structura

36、l failure can be given as a function of the random variables, as follows:</p><p>　　f（X）=f（，，………） （1）</p><p>　　where f (X) is the limit state function representing t

37、he margin between structural capacity and demand (i.e. loads or load effects); x i represents the design</p><p>　　parameters. The limit state function f (X) characterizes the condition of the structure and d

38、efines two domains of safety with regard to the limit surface (envelope), as follows:</p><p>　　f（X）>0 in the safe domain</p><p>　　f（X）=0 on the limit surface

39、 （2）</p><p>　　f（X）<0 in the unsafe domain</p><p>　　With two independent random variables, the ultimate limit state function f (X) for ship hull collapse is usually taken as the margin bet

40、ween ship hull ultimate strength and total bending moment , as follows:</p><p>　　f（X）=- （3）</p><p>　　whereand are functions of the design variables

41、.</p><p>　　Methods of reliability analysis</p><p>　　The methods for structural reliability analysis are usually classified into four types, namely level I, level II, level III and level IV . The

42、 level I method corresponds to the deterministic or partial safety factor method, using only one characteristic mean value for each variable. A relevant allowable usage factor for each variable that may be determined by

43、calibration of a higher level reliability method-based results is applied in the level I reliability analysis to approximately supplement </p><p>　　The ship structural reliability analysis is usually underta

44、ken by the level III method. Since the theory ofreliability analysis is discussed in many references, e.g. Mansour and Ditlevsen & Madsen , only a very brief description for the level III method is given here. Gene

45、rally the probability of failure P f can be calculated as follows:</p><p>　　=P（X）dx （4）</p><p>　　where p(X) is the joint probability density function of the r

46、andom variables X=，，………associated with loading, material properties, geometric characteristics, etc. and</p><p>　　f (X) is the limit state function, defined such that negative values imply failure. Since f (

47、X) is usually a complicated nonlinear function, it is not easy to perform the integration of eq. (4) directly. Therefore, the equation is normally solved by use of approximate procedures . </p><p>　　With the

48、se approximations, as indicated in Fig. 2, the limit state surface is usually approximated at the design (failure) point by either a tangent hyper-plane or a hyper-parabola, which simplifies the mathematics related to th

49、e calculation of the failure probability. The first type of approximation results in the use of a so-called first-order reliability method (FORM) and the second type of approximation is central to the so-called second-or

50、der reliability method (SORM). Such methods facilita</p><p>　　= （5）</p><p>　　where is the standard normal distribution function.</p><p>&

51、lt;b>　　Fig. 2</b></p><p>　　Further considerations</p><p>　　While a number of useful methodologies for analyzing the safety and reliability of ship structures have been developed over th

52、e past decades, further developments are needed. Some further considerations in probability-based design of ship structures are as follows:</p><p>　　● geometric parameters may be treated as deterministic, a

53、lthough this may need to be confirmed in the case of deck and bottom plating thickness;</p><p>　　● elastic modulus may be taken as deterministic, but yield stress needs to be treated as a random variable wi

54、th a mean value based on a fuller assessment of strain-rate effects on yield in large-scale representative ship-type structures than presented here. In the first instance, yield stress values could be based on tensile co

55、upon test results when wave-induced bending moments dominate, and similarly derived static values of yield stress for dominant still water load conditions.</p><p>　　● hull girder and stiffened panel ultimat

56、e strength models require benchmarking against realistic mechanical collapse test data so that the distribution parameters for their associated modelling errors can be evaluated;</p><p>　　● when time-varian

57、t structural degradation, e.g. due to corrosion and fatigue, is considered, the probabilistic characteristics of such damage at any particular time should be quantified. While some work continues in this area, there exis

58、t probabilistic corrosion rate estimation models for tanker structures and for bulk carrier structures;</p><p>　　● consensus is required about the preferred methodology for determining an appropriate return

59、 period of response for ship design and how this might be achieved given the current status of environmental parameters and data records;</p><p>　　● the load factor methodology promoted in the literature is

60、 extremely promising, particularly because its form is compatible with limit state (LRFD) design code formats. Consensus is required concerning its generality and any further development. Classification Society and naval

61、 experiences should be helpful in identifying load combinations to be addressed. However, in identifying a safety format, account should be taken of relevant ISO codes (e.g. ISO 2394) in this area;</p><p>　　

62、● target safety and reliability initially requires a calibration approach to determine appropriate values, followed by adjustments based on judgments concerning successful designs and target reliabilities in other indus

63、tries, whilst recognizing that floating structures probably need one order of magnitude (in probability of failure terms) more reliability than comparable bottom-founded structures, and an expectation that component and

64、system reliabilities should differ by about one order in pro</p><p>　　● partial factor determination will require some form of simplified modelling of strength, loading or the reliability process in order t

65、hat such determination can proceed efficiently. Curve- or surface- fitting can be applied in all cases.</p><p>　　船舶結(jié)構(gòu)安全性和可靠性</p><p>　　J K 帕克[1] P A 普萊斯[2]</p><p>　　1.韓國(guó)釜山國(guó)家大學(xué) 2.英國(guó)

66、FAFA工程師顧問</p><p><b>　　摘 要</b></p><p>　　最近在研究和發(fā)展對(duì)該地區(qū)船舶結(jié)構(gòu)的設(shè)計(jì)方法，安全性和可靠性的評(píng)估，將阻力、負(fù)荷作為因子運(yùn)用概率的方法來(lái)對(duì)船體的抗損毀能力進(jìn)行設(shè)計(jì)。一些重要的發(fā)現(xiàn)和見解在以前的一些文獻(xiàn)中有過總結(jié)，并且建議通過技術(shù)和設(shè)計(jì)的改進(jìn)來(lái)達(dá)到將來(lái)發(fā)展的需要。</p><p>　　【關(guān)鍵詞】

67、船舶結(jié)構(gòu)安全；船舶結(jié)構(gòu)可靠性；負(fù)荷和阻力因子設(shè)計(jì)；船體損壞的幾率的結(jié)構(gòu)設(shè)計(jì)；主船體梁負(fù)荷；船體梁極限狀態(tài)；極限強(qiáng)度；船舶可靠性。</p><p><b>　　船體梁倒塌事故</b></p><p>　　全面破損的船體很少發(fā)生在靜水或較小波浪中。圖1顯示最近一艘散貨船損毀，在港口排放出 126000噸的鐵礦石貨物。不過這艘服役23年的139800載重噸的船并未折成兩段，

68、有報(bào)道稱它的中間分段沉入海底，這表明船體梁全部損毀。清空后船艏和船艉之間有5個(gè)貨艙，屈曲發(fā)生在船的甲板上，盡管船體的中間部位還是完整的。一般都認(rèn)為發(fā)生這個(gè)事故主要是因?yàn)椴划?dāng)?shù)貜拇闲敦?，但是毫無(wú)疑問會(huì)有關(guān)于船體極限狀態(tài)以及檢驗(yàn)和維護(hù)方面的猜測(cè)。</p><p>　　確保船體的完整性顯然是要求維持所施加的載荷要小于設(shè)計(jì)載荷，在普通海域和加載條件下它將不會(huì)遭受結(jié)構(gòu)失效，比如屈曲和崩潰，除了可能的局部屈服。然而，由于大

69、波浪或不當(dāng)?shù)难b卸貨物作用，在船舶表面載荷是不確定的。在這種情況下，外加載荷有可能超過設(shè)計(jì)荷并且船體表面會(huì)破損。此外，由腐蝕引起的疲勞老化可能會(huì)導(dǎo)致結(jié)構(gòu)減弱，疲勞和局部損壞會(huì)引起結(jié)構(gòu)抵抗能力的減弱，船體結(jié)構(gòu)在外加負(fù)荷下甚至在小于設(shè)計(jì)負(fù)載的時(shí)候可能破損。</p><p>　　圖1，一船舶在港口卸貨的時(shí)候斷裂（由勞埃德提供）</p><p><b>　　粗糙結(jié)構(gòu)設(shè)計(jì)程序</b&g

70、t;</p><p>　　粗糙的船舶結(jié)構(gòu)設(shè)計(jì)通常如下：</p><p>　　建立一個(gè)可靠度目標(biāo)；</p><p>　　確認(rèn)所有不利結(jié)構(gòu)的失效模式；</p><p>　　為上文提到的每個(gè)失效模式制定極限狀態(tài)方程；</p><p>　　識(shí)別概率特征（平均方差分析、分布）隨機(jī)變量的極限狀態(tài)方程；</p><

71、;p>　　對(duì)各個(gè)結(jié)構(gòu)的失效模式進(jìn)行極限狀態(tài)的可靠性計(jì)算；</p><p>　　如果預(yù)測(cè)的可靠性評(píng)估大于目標(biāo)可靠度，要對(duì)其他結(jié)構(gòu)重新設(shè)計(jì)；</p><p>　　進(jìn)行參數(shù)對(duì)可靠性分析結(jié)果敏感性的考慮；</p><p><b>　　船體梁結(jié)構(gòu)強(qiáng)度</b></p><p>　　四種類型的極限狀態(tài)可以被分為：使用極限狀態(tài)，最

72、終極限狀態(tài)、疲勞極限狀態(tài)及意外極限狀態(tài)，使用極限狀態(tài)退化的有以下幾個(gè)方面，包括：</p><p>　　局部損壞發(fā)生在那些耐用性可能減弱，結(jié)構(gòu)或非結(jié)構(gòu)要素受影響的結(jié)構(gòu)；</p><p>　　影響那些結(jié)構(gòu)或非結(jié)構(gòu)要素，或運(yùn)行設(shè)備的不可接受的變形；</p><p>　　過度的振動(dòng)引起人的不舒適或者影響非結(jié)構(gòu)要素和運(yùn)行設(shè)備。</p><p>　　極限

73、狀態(tài)表示的結(jié)構(gòu)的損壞，從以下方面表示，如：</p><p>　　結(jié)構(gòu)或部分結(jié)構(gòu)的失衡被認(rèn)為是一個(gè)剛體的（傾覆）；</p><p>　　當(dāng)截面達(dá)到最大的負(fù)載能力，組織連接將達(dá)到屈服，將斷裂或破裂；</p><p>　　不穩(wěn)定的結(jié)構(gòu)或部分結(jié)構(gòu)，例如屈曲圓柱、板材、船殼和加強(qiáng)筋等。</p><p>　　疲勞極限狀態(tài)結(jié)果形成是因?yàn)殚L(zhǎng)期在負(fù)載的條件下，

74、意外極限狀態(tài)是由于事故，比如碰撞或擱淺。</p><p>　　所有不經(jīng)常發(fā)生船體梁的失效，一般都是由于甲板、船底或有時(shí)舷側(cè)外板的加強(qiáng)筋的屈曲和塑性變形。失效的甲板、船底或舷側(cè)外板的加強(qiáng)筋會(huì)導(dǎo)致進(jìn)一步的破壞并最終使船體梁完全失效。多年來(lái)，船舶結(jié)構(gòu)研究人員一直朝著船舶結(jié)構(gòu)可靠性極限設(shè)計(jì)的目標(biāo)努力。然而，可靠性設(shè)計(jì)要求最終極限狀態(tài)的計(jì)算，不僅是船體梁，還有所有的結(jié)構(gòu)面板和其他的結(jié)構(gòu)。同時(shí)，這些計(jì)算必須需要大量的時(shí)間。因

75、此將這些計(jì)算應(yīng)用有限元分析并不太實(shí)際，對(duì)于結(jié)構(gòu)零件和完整的船體梁要有效地進(jìn)行極限強(qiáng)度的計(jì)算必須要發(fā)展通用的表達(dá)式。</p><p>　　大量的從事人員已經(jīng)從理論上、數(shù)學(xué)上和實(shí)驗(yàn)上對(duì)船體的極限的破裂強(qiáng)度進(jìn)行了研究。有些關(guān)于極限強(qiáng)度的研究成果已經(jīng)通過了船舶技術(shù)委員會(huì)的審核。關(guān)于船體極限強(qiáng)度可靠性目前已經(jīng)研究過的有與腐蝕、疲勞和碰撞有關(guān)的局部損壞。</p><p>　　以往關(guān)于發(fā)展船體極限強(qiáng)度預(yù)

76、測(cè)構(gòu)想的研究分為三個(gè)部分。首先是線性的方法，船體的抗壓凸緣在船體上的失效現(xiàn)象被看做是線性且具有彈性的，忽略屈曲。且最終船體的極限強(qiáng)度相當(dāng)于抗壓凸緣的極限強(qiáng)度乘以彈性結(jié)構(gòu)的剖面模數(shù)，加上對(duì)屈曲和屈服的簡(jiǎn)單的修正。第二種是用實(shí)證研究方法，在通過實(shí)驗(yàn)的方法和從縮放圖像或真實(shí)模型中提取出的數(shù)據(jù)資料的基礎(chǔ)上得到的表達(dá)式。第三是一種分析方法，從船體受載荷的瞬間的理論計(jì)算值推算出船體截面的應(yīng)力分布，重點(diǎn)考慮抗壓凸緣的張力屈服。</p>

77、<p>　　第一種方法是很簡(jiǎn)單的，但通常其準(zhǔn)確性不足，因?yàn)榭箟和咕壥艿綇澢螅w并沒有表現(xiàn)出線性，并且中和軸的位置發(fā)生了變化。實(shí)證研究法（第二種方法）可以為常規(guī)船體提供合理的解決方案，但是在新型和常規(guī)船體表達(dá)式的使用中必須要很小心，因?yàn)榻?jīng)驗(yàn)公式通常是通過有限的數(shù)據(jù)或個(gè)別特殊的船型推算出來(lái)的。另一種分析方法（第三種方法）能應(yīng)用于新型的和常規(guī)的船型因?yàn)樗鼈儼ǖ钠拭嫘问礁_。</p><p>　　船體極

78、限強(qiáng)度的公式最終表示成一種與幾何、材料的性質(zhì)包括板厚、屈服強(qiáng)度、彈性模量有關(guān)的設(shè)計(jì)。當(dāng)隨時(shí)間變化結(jié)構(gòu)的減弱（例如腐蝕），一直都認(rèn)為對(duì)于這種損害有特別研究的價(jià)值。在粗糙的設(shè)計(jì)方法中，所有的設(shè)計(jì)參數(shù)都被當(dāng)做隨機(jī)變量。船體扭曲的極限強(qiáng)度與一般的下垂是不同的。</p><p><b>　　極限狀態(tài)方程</b></p><p>　　數(shù)學(xué)上，對(duì)于失效的結(jié)構(gòu)會(huì)根據(jù)隨機(jī)變量給予極限狀

79、態(tài)方程，如下：</p><p>　　f（X）=f（，，………） （1）</p><p>　　f（X）是極限狀態(tài)方程，代表結(jié)構(gòu)承載能力和需求大?。捶匣蚍闲Ч┑牟钪担硎驹O(shè)計(jì)參數(shù)，極限狀態(tài)方程f(X)把與限制表面的安全性有關(guān)的結(jié)構(gòu)和定義兩個(gè)方面的特征表示出來(lái)，如下：</p><p>　　f（X）>0 在安

80、全區(qū)域</p><p>　　f（X）=0 在限制表面上 （2）</p><p>　　f（X）<0 在不安全區(qū)域</p><p>　　兩個(gè)獨(dú)立的隨機(jī)變量，它的極限狀態(tài)方程f（X）通常表示船體破壞時(shí)被看作是船體極限強(qiáng)度和彎矩總和的差，如下</p><p>　　f（X）=-

81、 （3）</p><p>　　其中和是方程的設(shè)計(jì)變量。</p><p><b>　　可靠性分析的方法</b></p><p>　　結(jié)構(gòu)可靠性分析方法通常被分成4類，就是一級(jí)、二級(jí)、三級(jí)、四級(jí)。一級(jí)水平方法相當(dāng)于是確定局部安全因素的方法，對(duì)每個(gè)變量運(yùn)用唯一的特征平均

82、值。有關(guān)對(duì)每個(gè)變量允許的使用因素可能取決于更高水平可靠性分析方法的校核標(biāo)準(zhǔn)，應(yīng)用在一級(jí)水平的可靠性分析方法可能是與不確定因素有關(guān)的補(bǔ)充。二級(jí)水平方法是使用兩個(gè)標(biāo)準(zhǔn)，即均值和標(biāo)準(zhǔn)偏差，描述每個(gè)隨機(jī)變量的特征?？煽啃灾笖?shù)方法，例如一階、二階力矩法是二級(jí)水平方法中一種典型的例子。二級(jí)水平方法采用聯(lián)合概率密度函數(shù)的特征來(lái)描述隨機(jī)變量。運(yùn)用三級(jí)水平的可靠性分析方法要么采用近似分析法（例如一階或二階的可靠性分析方法），要么采用數(shù)值模擬方法（例如蒙特

83、卡羅模擬或者方向取樣分析都被應(yīng)用）。四級(jí)水平方法是通過工程經(jīng)濟(jì)分析比較目標(biāo)結(jié)構(gòu)和參考結(jié)構(gòu)的完整性和前景，考慮到結(jié)構(gòu)失效和維護(hù)與花費(fèi)和獲利有關(guān)。四級(jí)水平方法被用在目標(biāo)的可靠性上。</p><p>　　這艘船結(jié)構(gòu)可靠性分析通常用三級(jí)水平方法，理論分析在很多的文獻(xiàn)中被研究，例如曼蘇爾和麥迪森，三級(jí)方法僅是在這里有非常簡(jiǎn)短的描述。一般失效的概率的計(jì)算方式如下：</p><p>　　=P（X）dx

84、 （4）</p><p>　　在p(X)是聯(lián)合概率密度函數(shù)隨機(jī)變量X=，，………與加載條件、材料特性、幾何特征等有關(guān)，f(X)是極限狀態(tài)方程，定義為取到負(fù)值時(shí)即為失效。因?yàn)閒(X)通常含有比較復(fù)雜的非線性的功能，它不能直接地應(yīng)用公式（4）整合完成，因此方程式通常運(yùn)用近似的程序來(lái)解決。</p><p>　　運(yùn)用近似的方法，

85、就像圖2表明，極限狀態(tài)船體表面通常接近于設(shè)計(jì)（失效）點(diǎn)要么高于切線要么高于拋物線，利用簡(jiǎn)化數(shù)學(xué)運(yùn)算來(lái)計(jì)算有關(guān)的失效概率。第一種近似結(jié)果使用在所謂的一階的可靠性方法，第二種近似方法是主要用在所謂的二階的可靠性方法。這種方法通過廣泛應(yīng)用的標(biāo)準(zhǔn)軟件能方便快速計(jì)算失效概率。除了一些個(gè)別的有關(guān)隨機(jī)變量的概率分布，對(duì)這種運(yùn)算的聯(lián)系很容易做出解釋，還要考慮各種不相關(guān)的隨機(jī)變量?？煽啃詷?biāo)準(zhǔn)的結(jié)果是可靠性指數(shù)與失效概率的關(guān)系：</p>&l

86、t;p>　　= （5）</p><p>　　這是函數(shù)的標(biāo)準(zhǔn)正態(tài)分布。</p><p><b>　　圖2</b></p><p><b>　　將來(lái)規(guī)劃</b></p><p>　　然而船舶結(jié)構(gòu)安全性和可靠性的

87、一些分析方法在過去使用了幾十年，進(jìn)一步的發(fā)展是非常必要的。一些關(guān)于船舶結(jié)構(gòu)可能性設(shè)計(jì)的進(jìn)一步發(fā)展規(guī)劃如下：</p><p>　　幾何參數(shù)可以被看做是確定的，盡管它們可能要在甲板和船底板厚度上要進(jìn)一步的</p><p><b>　　確認(rèn)；</b></p><p>　　2. 彈性模量可以當(dāng)作是確定的，但是屈服應(yīng)力的平均值要被當(dāng)作是一個(gè)隨機(jī)變量，以

88、</p><p>　　這里提出的常規(guī)船型為代表，評(píng)估屈曲對(duì)結(jié)構(gòu)的影響。在這個(gè)例子中，波浪引起的彎矩在屈服應(yīng)力的試驗(yàn)結(jié)果中起著重要的作用，同樣在靜水中的負(fù)載狀態(tài)在屈服應(yīng)力中也明顯起著重要作用；</p><p>　　3. 船體梁和加強(qiáng)板材的極限強(qiáng)度需要真實(shí)船模的機(jī)械破壞性試驗(yàn)的數(shù)據(jù)作為標(biāo)準(zhǔn)，所以他們建模的誤差的參數(shù)分布是可以估算的；</p><p>　　4. 隨著使

89、用時(shí)間增加結(jié)構(gòu)減弱，如由于腐蝕和疲勞，認(rèn)為這些損害在特定時(shí)間的特征概率分布應(yīng)該被量化，同時(shí)很多繼續(xù)從事這方面的工作，現(xiàn)在有油船和散貨船模型結(jié)構(gòu)的腐蝕率的概率分布的估算；</p><p>　　5. 考慮到當(dāng)前狀況的環(huán)境參數(shù)和數(shù)據(jù)記錄，一致認(rèn)為選擇適當(dāng)母型船來(lái)設(shè)計(jì)船舶的決定是非常正確的；</p><p>　　6. 這種負(fù)荷系數(shù)的方法對(duì)促進(jìn)理論發(fā)展非常有前景，特別是因?yàn)樗男问脚c極限狀態(tài)（系

90、數(shù)設(shè)計(jì)法）設(shè)計(jì)規(guī)范格式相一致。普遍認(rèn)為對(duì)于它的普遍性的進(jìn)一步發(fā)展非常有必要。船級(jí)社和船廠的經(jīng)驗(yàn)對(duì)負(fù)載組合的處理非常有幫助，不過，識(shí)別格式是否安全，還要考慮到這個(gè)地區(qū)的相關(guān)的國(guó)際標(biāo)準(zhǔn)組織有關(guān)的規(guī)定（比如國(guó)際標(biāo)準(zhǔn)組織2394）；</p><p>　　7. 目標(biāo)的安全性和可靠性最初需要校核的方法來(lái)確定標(biāo)準(zhǔn)，然后通過調(diào)整有關(guān)成功的設(shè)計(jì)來(lái)判斷目標(biāo)的可靠性，同時(shí)從其他方面認(rèn)識(shí)到流動(dòng)結(jié)構(gòu)可能需要一個(gè)（按失效概率）或更多來(lái)比較