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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 direction, 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 longitud
