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1、Ships Longitudinal Strength,船舶纵向强度 longitudinal经度的；纵向的 lgtju:dnl,船体结构必须具有抵抗各种内外力作用使之发生极度变形和破坏的能力，这种能力称为船体强度(strength of ships)。 纵向强度(longitudinal strength)是指船体结构抵抗因垂向受力沿纵向分布变化造成的总纵弯曲和剪切变形导致结构极度变形和破坏的能力。,1,U7L2纵向强度,II Text,When a ship is floating or moving through the water, there are many forces act
2、ing on作用于 its hull. 当船舶漂浮或对水移动时，有许多种力作用在船体上。 How forces act is largely determined by the kind of ship. 这些力是如何作用的很大程度上由船舶类型决定。 Types of forces that occur are the same for every ship, but the magnitudes大小 and points of action depend on the shape of the ships hull. 产生的力的类型对每条船来讲是相同的，但力的大小和作用点取决于船体形状。,2
3、,U7L2纵向强度,1. Types of forces that occur are for every ship when floating or moving through the water. A. different 不同的 B. identical 完全相同的 C. similar相似的 D. not mentioned没有提到 答案：B,3,U7L2纵向强度,The pattern of forces on a ships hull is largely depends (dependent) on the following parameters: 船体所受力的形式很大程度上
4、取决于以下参数： the weight of the empty ship (light ship weight), the weight and distribution分布 of the cargo, fuel, ballast, provisions, fresh water etc., hydro-static pressure on the hull applied by the water, hydro-dynamic forces resulting from起因于 the movement of the ship on the waves, etc. 空船重量，货物、燃料、压载
5、水、食物、淡水等的重量及分布，海水施加在船体的静水压力，由船舶在水上移动产生的水动力等。 These and other forces cause the ship to deflect. 这些力导致船舶弯曲变形。,4,U7L2纵向强度,When the force disappears, the ship will regain its original shape due to ships hull flexibility. 当这些力消失时，基于船体弹性，船舶会恢复原样。 In some case the forces exceed a certain limit, permanent d
6、eformation变形 can occur. 在某些情况下，力超出一定限制，船体可能发生永久性的变形。 Length of very large carrier exceeds 300 m, and especially forces with high magnitudes acting on its hull in longitudinal direction. 长度超过300米的大型船舶，尤其高强度的力会作用在船体纵向。,5,U7L2纵向强度,5. When the forces disappears, the ship will its original shape due to s
7、hips hull flexibility. A. deflect挠曲 B. regain恢复 C. maintain保持 D. alter改变 答案：B,6,U7L2纵向强度,Ship strength generally represents表示 the ships structural ability to resist the effects of outside forces. 一般来讲，船舶强度代表船舶结构上抵抗外力作用的能力。 When a ship is in calm water, the total upward force (buoyant forces) will eq
8、ual the total weight of the ship (displacement of the ship) as the first law of flotation states. (See Note 1)根据浮力第一定律，静水中船舶所受的浮力等于其重量（排水量）。,7,U7L2纵向强度,Locally局部地 this equilibrium will not be realized because the ship is not a rectangular homogeneous object. 由于船舶不是箱型均匀体，这种平衡在局部上是达不到的。 The local diff
9、erences between upward pressure of buoyancy and the ships local weight give rise to shearing forces, Qx that lead to longitudinal tensions and the bending moment, Mx. 船舶局部浮力和重量的差值造成可导致纵向应力的剪力Qx和弯矩Mx的产生。 The greatest forces moments and stresses that affect the ship hull are expressed as bending and b
10、uckling in the longitudinal vertical plane. 影响船体的最大力矩和应力表示为纵向垂面上的弯曲变形。,8,U7L2纵向强度,7. The local differences between upward pressure of buoyancy and the ships local weight give rise to . A. twisting forces扭变力 (torsional force) B. racking forces歪变力 C. shearing forces剪切力 D. transversal forces横向力 答案：C,9,
11、U7L2纵向强度,Transverse force Qx has a positive sign value if its direction from upward to downward, and respectively 分别地Qx has a negative sign value in case of a direction contrary to与相反 that previously mentioned. 如果剪力Qx方向从上向下，则取正值，相应的，如果剪力方向与前述相反，Qx取负值。 At the ship ends (as sate at first law of flotat
12、ion) transversal forces are equal to zero. 在船舶两端，剪力等于零（满足浮力第一定律）。 注：剪力绝对值的最大值一般出现在距船舶首尾1/4船长处。,10,U7L2纵向强度,The bending moment on still water (SWBM) indicates how loading weight distribution affects on longitudinal strength. 静水中弯矩指示载重量分布如何影响纵向强度。 Bending moments value are also different over the part
13、icular cross section横截面, because besides the difference between buoyancy and weight force itself, there is also the difference between the center of gravity of the ships mass at cross section and center of gravity of submerged part cross section. 弯矩值在特定横截面也有不同，因为除了浮力与重力有差值外，船舶质量在横截面的重心与水下部分横截面的重心也有差
14、别。 注：重力对剖面的力矩不等于该侧浮力对剖面的力矩，即产生弯矩。,11,U7L2纵向强度,2. on still water indicates how loading weight distribution affects on longitudinal strength. A. Bending moment弯矩 B. Longitudinal strength纵向强度 C. Shear force剪力 D. Displacement排水量 答案：A,12,U7L2纵向强度,Bending moment can be expressed as hogging or sagging defl
15、ection depending on its acting direction. 弯矩由其作用方向可表示为中拱和中垂。 Hogging indicate that the vertical deflection of a ships hull, in longitudinal direction, where the hull midships is bent upwards, as a result of cargo distribution and/ or the way the ship is supported by a wave at sea. 中拱表明由于货物分布和/或船舶受波浪
16、承载的形式而导致的船体纵向垂直变形，船体中央部分向上拱起。,13,U7L2纵向强度,8. can be expressed as hogging or sagging deflection depending on its acting direction. A. Local strength局部强度 B. Bending moment弯矩 C. Shear forces剪力 D. Deck load甲板载荷 答案：B,14,U7L2纵向强度,3. indicate that the vertical deflection of a ships hull, in longitudinal di
17、rection, where the hull midships is bent upwards. A. Shearing B. Sagging C. Hogging D. Buckling 答案：C,15,U7L2纵向强度,Respectively, sagging indicate that the vertical deflection of a ships hull in longitudinal direction, where the hull midships is bent downwards, as a result of cargo distribution and/ or
18、 the way the ship is supported at sea. 相应的，中垂表明由于货物分布和/或船舶受波浪承载方式引起的船体纵向垂直变形，船舶中央部分向下凹陷。 注：弯矩绝对值的最大值通常出现在船中处。,16,U7L2纵向强度,The direct evaluation procedure requires, for a given loading condition, a derivation求导, section by section, of vertical resultants合力 of gravitational (weight) and buoyancy force
19、s, applied along the longitudinal axis of the beam. (See Note 2)评估程序要求对于每一装载状态，沿纵向梁分段求出其上重力和浮力。 To obtain the weight distribution W(x), the ship length is subdivided into portions: for each of them, the total weight and center of gravity is determined summing up总计 contributions from all items presen
20、t on board between the two bounding sections. 为获得船舶重量分布W(x),船舶长度细分为许多部分：对于每一部分，总重量和重心由处在两边界之间的所有物件的总和决定。,17,U7L2纵向强度,The distribution for W(x) is then usually approximated by a linear (trapezoidal) curve for the considered ship portion. 所考虑的船舶部分的重量分布W(x)通常近似于线性（梯形）曲线。 The procedure is usually applie
21、d separately for different types of weight items, grouping together 集合the weights of the ship in lightweight conditions and those (cargo, ballast, consumables) typical of a loading condition. 这种程序通常分别应用于不同类型的重量成分，将空载船舶重量和典型装载物（货物、压载、消耗品）的重量结合在一起。,18,U7L2纵向强度,The prediction of the behavior of the shi
22、p in waves represents a key point in the quantification量化 of both global整体 and local局部 loads acting on the ships hull. (See Note 3)正确估计船舶在波浪中的响应特征是量化作用在船体上的整体结构受力和局部受力的关键。 The action of waves modifies修改 the pressure distribution along the hull surface. 波浪作用可改变沿船体表面的压力分布。 注：波浪会使浮力沿纵向分布发生变化。波浪中剪力与静水中剪
23、力的差值称为波浪剪力(wave shear force)。波浪中弯矩与静水中弯矩的差值称为波浪弯矩(wave bending moment)。,19,U7L2纵向强度,The differential pressure between the situation in waves and in calm water (weight distribution of the ship is unchanging and unequal buoyancy distribution) generates产生 on the transverse section additional bending mo
24、ment. 船舶在波浪中和静水中的压差（船舶重量分布不变，浮力分布不规则）在横截面产生额外的弯矩。 differential ,dfren()l n. 微分；差别 transverse section=cross section （截面）,20,U7L2纵向强度,The ship is positioned on a statical wave of given characteristics in a condition of equilibrium between weight and static buoyancy. 船舶处在具有给定特性的静水当中，重量和静浮力达到平衡。 static
25、wave= still water Numerous researches have determined that the biggest wave load appears when a wave length is approximately equal to the ships length. The ship course has to match the wave direction. 许多研究断定，当波长约等于船长，会出现最大的波浪载荷。船舶航向必须与波浪方向相同。,21,U7L2纵向强度,6. The ship is positioned on a statical wave
26、of given characteristics in a condition of ? between weight and static buoyancy. A. equilibrium平衡 B. uniform统一 C. distortion变形 D. undulation起伏 答案：A,22,U7L2纵向强度,4. Numerous researches have determined that the biggest wave load appears when a wave length is the ships length. A. greatly larger than B.
27、much smaller than C. approximately equal to D. not related to 答案：C,23,U7L2纵向强度,Among all groups of approaches方法 on determination ships longitudinal strength (closed-form formulae, simplified analytical methods and nonlinear simulations), the above consider simplified analytical methods are favored b
28、y most analysts. 在所有判定船舶纵向强度的方法当中（详算法、简化解析法和非线性模拟法），上述简化解析法得到大多数分析人员的青睐。 These approaches save modeling time and provide reliable results. 这种方法可节省建模时间并提供可靠结果。,24,U7L2纵向强度,A simplified method has been placed as the first choice in extensive广泛的 related research of determination ultimate hull girder st
29、rength. 在判定最终船体总强度的广泛相关研究中，简化解析法被作为第一选择。,25,U7L2纵向强度,The continuous improvement of knowledge regarding the behavior of ships hull at various conditions has led to引起 the development of various new methods in determination hull girder strength. 关于船体在不同状况中响应的知识不断发展，引起判定船体总强度的各种新方法的产生。 In recent few yea
30、rs, there has been a growing interest in implementing optical fiber sensors on ships. 在近几年，船上实施光纤传感器的方法逐渐引起人们的兴趣。 Optical fiber sensors also can be used on ships hull structural monitoring system. 光纤传感器也可用于船体结构监控系统。,26,U7L2纵向强度,We aim to旨在 obtain a possibility to determine hull girder strength using
31、 optical fiber sensors, which may be used as handy便利的 to verification of transverse, longitudinal and local strength for a momentary loading condition and to help make timely decision in the event of an emergency which has been arising from accident. 我们致力于获得使用光纤传感器判定船体总强度的可能性，光纤传感器能便利验证船舶瞬时受力情况下的横向、
32、纵向和局部强度并有助于在由事故引致的紧急情况下作出及时决定。,27,U7L2纵向强度,Task 1. Reading Comprehension 1. What factors is the pattern of forces affected by? The weight of the empty ship, the weight and distribution of the cargo, fuel, ballast, provisions, fresh water, hydrostatic pressure, hydrodynamic forces, etc. 2. How will t
33、he ship act when the forces cease to exist? Regain its original shape. 3. What is the ship strength? It represents the ships structural ability to resist the effects of outside forces. 4. What is the first law of flotation? When a ship is in calm sea, buoyant force will equal the total weight of the
34、 ship.,28,U7L2纵向强度,5. What does ship hogging mean? Hogging indicate that the vertical deflection of a ships hull, in longitudinal direction, where the hull midships is bent upwards. 6. How is ship sagging caused? Cargo distribution & the way the ship is supported at sea. 7. How does direct evaluatio
35、n procedure work out? It requires for a given loading condition, a derivation section by section of vertical resultants of gravitational and buoyancy forces, applied along the longitudinal axis of the beam.,29,U7L2纵向强度,8. When does the biggest wave load exist? When a wave length is approximately equ
36、al to the ships length. 9. What is the best method on determination ships longitudinal strength? Simplified analytical method. 10. What function does the optical fiber sensor act? It may be used as handy to verification of transverse, longitudinal and local strength for a momentary loading condition
37、. It can also be used on ships hull structural monitoring system.,30,U7L2纵向强度,Task 2 Sagging中垂 Deck load甲板载荷 Strength deck强力甲板 Longitudinal bulkhead纵向舱壁 Weight distribution重量分布 Buoyancy force浮力 Cross section横截面 SWBM=static/still water bending moment静水弯矩 Shear force剪力 Slamming砰击，波击 Strength member强力构
38、件,31,U7L2纵向强度,1. 由船底延伸到甲板的舱壁，它通过前后的横向舱壁连接到船舶两舷。(longitudinal bulkhead) 2. 静水中的弯矩。(SWBM) 3. 船壳平坦的区域与水以锐角接触，发出巨响并且船体剧烈震动。(slamming) 4. 船舶露天甲板装载的货物。(deck load) 5. 船舶承受载荷的部件。(strength member) 6. 能够抵抗纵向弯曲的最上层连续甲板。(strength deck) 7. 船体中心向下弯曲。(sagging) 8. 船舶内部重量分布。(weight distribution) 9. 流体施加的力，该力与船舶重量相反。
39、(buoyancy force) 10. 在船舶长度上的任一位置，趋向于把一部分相对于邻近部分垂向移动的力。(shear force) 11. 三维物体与平面相交。(cross section),32,U7L2纵向强度,Task 3 Translation Exercises,1. In some case the forces exceed a certain limit, permanent deformation can occur. 在某些情况下，力超出一定限制，船体可能发生永久性的变形。 2. Sagging indicate that the vertical deflection
40、 of a ships hull in longitudinal direction, where the hull midships is bent downwards, as a result of cargo distribution and/ or the way the ship is supported at sea. 中垂表明由于货物分布和/或船舶受波浪承载方式引起的船体纵向垂直变形，船舶中央部分向下凹陷。,33,U7L2纵向强度,3. The ship is positioned on a statical wave of given characteristics in a
41、condition of equilibrium between weight and static buoyancy. 船舶处在具有给定特性的静水当中，重量和静浮力达到平衡。 4. The continuous improvement of knowledge regarding the behavior of ships hull at various conditions has led to the development of various new methods in determination hull girder strength. 关于船体在不同状况中响应的知识不断发展，引起判定船体总强度的各种新方法的产生。,34,U7L2纵向强度,