第四章 固体力学有限单元法(续)§4—3 刚架分析 空间刚架单元是一个等截面的直杆,它能承受轴向力、对横截面两个主轴的弯矩和对轴线的扭矩,其相应的位移自由度共有12个,即φ_1、φ_2、φ_3… 、φ_(12),如图4—4。 其中,xyz为单元的局部坐标系,x轴为单元的轴线方向,y与z轴为横截面的主轴方向,由材料力学得知,轴向位移φ_1与φ_7,只依赖于 Chapter 4 Solid Mechanics Finite Element Method (cont.) §4-3 Rigid Frame Analysis The space frame unit is a straight rod with constant cross-section, which can bear the axial force. It can measure the bending moment of the two main axes and the Torque, the corresponding displacement of a total of 12 degrees of freedom, namely φ_1, φ_2, φ_3 ..., φ_ (12), as shown in Figure 4-4. Where xyz is the local coordinate system of the unit, x is the axial direction of the unit, and y and z are the major axis directions of the cross section. It is known from the material mechanics that the axial displacements φ_1 and φ_7 only depend on