EI
Flexural rigidity 抗弯刚度
It is important to note that this ratio should be calculated using some global distance measures, and not based on individual element dimensions. The following graphic provides an estimate of transverse shear deformation in a cantilever beam subjected to a tip load. Although the results cannot be extrapolated to any other application, the example serves well as a general guideline. We recommend that the slenderness ratio should be greater than 30.
需要注意的是这个比例的计算需要用一些全局距离尺寸，不是基于独立的单元尺度。下面这个图提供了受端部集中荷载的悬臂梁的横向剪切变形的例子，这个例子可以作为一个很好的大致的指导。我们推荐长细比要大于30。
Figure 188.2: Transverse-Shear Deformation Estimation
图188.2：横向剪切变形的评估示意
Slenderness Ratio (GAL2/(EI)) 长细比 25 50 100 1000 δ Timoshenko / δ Euler-Bernoulli 位移：铁木辛哥/欧拉－伯努力 1.120 1.060 1.030 1.003 These elements support an elastic relationship between transverse shear forces and transverse shear strains. You can override default values of transverse shear stiffnesses using the SECCONTROLS command.
这些单元支持横向剪切力和横向剪切变应力的弹性关系。你可以用seccontrols 命令重新定义默认的横向剪切刚度值。
The St. Venant warping functions for torsional behavior are determined in the undeformed state, and are used to define shear strain even after yielding. ANSYS does not provide options to recalculate in deformed configuration the torsional shear distribution on cross-sections during the analysis and possible partial plastic yielding
of cross-sections. As such, large inelastic deformation due to torsional loading should be treated and verified with caution. Under such circumstances, alternative modeling using solid or shell elements is recommended.
无形变的状态决定了扭转作用引起的圣维南翘曲变形，可以用来定义屈服后的剪应力。Ansys 没有提供选项使不成型的结构重新计算，这种结构是由分析过程中的扭转剪切对横截面的作用以及部分截面塑性屈服引起的。正因为此，由扭转作用引起的非弹性大变形需要小心的来处理和校核。在这样的情况下，推荐使用solid 或者shell 单元来替换。
BEAM188 elements support “restrained warping” analysis by making available a seventh degree of freedom at each beam node. By default, BEAM188 elements assume that the warping of a cross-section is small enough that it may be neglected (KEYOPT(1) = 0). You can activate the warping degree of freedom by using
KEYOPT(1) = 1. With the warping degree of freedom activated, each node has seven degrees of freedom: UX, UY, UZ, ROTX, ROTY, ROTZ, and WARP. With KEYOPT(1) = 1, bimoment and bicurvature are output.
Beam188单元支持“约束扭转”分析，通过定义梁节点的第七个自由度来实现。Beam188 单元默认的假设是截面的扭转是足够小的以至于可以忽略（KEYOPT（1）＝0）。你可以激活它的扭转自由度通过定义KEYOPT（1）＝1。当激活节点的扭转自由度的时候，每个节点有七个自由度：UX，UY，UZ，ROTX, ROTY, ROTZ, 和WARP。当KEYOPT(1) = 1，双力矩和双弧线将被输出。
In practice, when two elements with “restrained warping” come together at a sharp angle, you need to couple the displacements and rotations, but leave the out-of-plane warping decoupled. This is normally accomplished by having two nodes at a physical location and using appropriate constraints. This process is made easier (or automated) by the ENDRELEASE command, which decouples the out-of plane warping for any adjacent elements with cross-sections intersecting at an angle greater than 20 degrees.
实际上，当两个“约束扭转”的单元以一个锐角组合在一起的时候，你需要耦合他们的唯一合转角，使它们平面外的自由度解藕。一般通过用两个节点在物理位置和运用合适的约束可以实现。这个过程通过ENDRELEASE命令很容易的（自动的）实现，命令将两个临近横截面相交角度大于20度的单元的平面外扭转解耦。
BEAM188 allows change in cross-sectional inertia properties as a function of axial elongation. By default, the cross-sectional area changes such that the volume of the element is preserved after deformation. The default is suitable for elastoplastic applications. By using KEYOPT(2), you can choose to keep the cross-section constant or rigid. Scaling is not an option for nonlinear general beam sections (SECTYPE,,GENB).
Beam188 允许改变横截面惯性属性来实现轴向伸长的功能。默认的，截面面积改变而使得单元的体积变形后不变化。这种默认的值对于弹塑性应用是适用的。通过运用KEYOPT（2）选项,你可以选择横截面是恒定的或者刚性的。Scaling命令不适用于一般的非线性梁截面。
Element output is available at element integration stations and at section integration points.
单元的输出在单元积分位置和截面的积分点可以使用。
Integration stations (Gauss points) along the length of the beam are shown in Figure 188.3: \.
沿着梁长度的积分点（高斯点）如图Figure 188.3所示：
Figure 188.3 BEAM188 Element Integration Stations
图188.3：Beam188单元积分点
The section strains and forces (including bending moments) may be obtained at these integration stations. The element supports output options to extrapolate such quantities to the nodes of the element.
截面的应变和力（包括弯距）可以在这些积分点上得到。单元支持输出选项来外推这些数值到单元的节点。
BEAM188 can be associated with either of these cross section types:
Beam188可以设置各种截面形式：
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Generalized beam cross sections (SECTYPE,,GENB), where the relationships of generalized stresses to generalized strains are input directly.
可直接输入材料广义应力应变关系生成广义梁截面(SECTYPE,,GENB)。
Standard library section types or user meshes which define the geometry of the beam cross section (SECTYPE,,BEAM). The material of the beam is defined either as an element attribute (MAT), or as part of section buildup (for multi-material cross sections).
可生成既有的或者用户指定的截面形式(SECTYPE,,BEAM)，梁元材料可以由MAT命令生成，也可以由多种材料的截面形式组成。
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Generalized Beam Cross Sections 广义的梁横截面
When using nonlinear general beam sections, neither the geometric properties nor the material is explicitly specified. Generalized stress implies the axial force, bending moments, torque, and transverse shear forces. Similarly, generalized strain implies the axial strain, bending curvatures, twisting curvature, and transverse shear strains. (For more information, see Using Nonlinear General Beam Sections.) This is an
abstract method for representing cross section behavior; therefore, input often consists of experimental data or the results of other analyses.
当使用非线性梁截面时，几何特征和材料属性均明确指定。广义应力包括轴力，弯矩，扭矩以及横向切应力。同样，广义应变包括轴向应变，弯曲应变，扭转应变以及横向剪切应变（更多信息详见Using Nonlinear General Beam Sections.）这是一个抽象方法反映截面的行为，因此输入的数据常常由试验或者其他分析构成。
The BEAM188 elements, in general, support an elastic relationship between
transverse shear forces and transverse shear strains. You can override default values of transverse shear stiffnesses via the SECCONTROLS command.
Beam188一般支持横向切应力和横向切应变之间的弹性关系，可通过SECCONTROLS 命令改写默认的应力应变关系。
When the beam element is associated with a generalized beam (SECTYPE,,GENB) cross section type, the relationship of transverse shear force to the transverse shear strain can be nonlinear elastic or plastic, an especially useful capability when flexible spot welds are modeled. In such a case, the SECCONTROLS command does not apply.
当梁单元采用广义梁截面时，横向切应力和横向切应变之间的关系为非弹性或者塑性，会生成一个可用的屈服点。这种情况下，SECCONTROLS命令不再适用。
Standard Library Sections 标准截面形式：
BEAM188 are provided with section-relevant quantities (area of integration, position, Poisson function, function derivatives, etc.) automatically at a number of section points using SECTYPE and SECDATA. Each section is assumed to be an assembly of a predetermined number of 9-node cells. The following graphic illustrates models using the rectangular section subtype and the channel section subtype. Each cross-section cell has 4 integration points and each may be associated with an independent material type.