温度改变时的超静定结构内力计算.pptx

超静定结构在非荷载因素作用下产生的内力称为自内力 (self-internal forces ).,基本体系 基本未知量 基本结构, 0,2,1 0,变形协调条件：,力法方程：, 0,111122, 2t 0,1t,21 X1 22 X 2,XX,1t ? 2t ?,基本体系,X1,X2, 1t,2t,计算图示刚架由于温度变化产生的内力. 已知刚架内侧升温 10 ，各杆件的线膨胀系数均为 , 杆件横截面高度 h 和杆 件抗弯刚度 EI 均为常量， L/h=3。,基本结构,基本未知量 基本体系,基本方程:,L,L,10,已知刚架温度变化如图所示，计算图示刚架内力。各杆线膨胀 系数 ，抗弯刚度 EI 均为常数. 截面高度 h=0.4m.,B,C,4m,A 4m,-15 25,25,-15,()The primary equations are symbolically the same as the case of loads, but the meaning of free term is different;,荷载及非荷载因素作用下，结构力法方程形式相同，仅自 由项意义不同。 ()All of the internal forces of a statically indeterminate structure are caused by its redundant constraints; 内力全部由多余未知力产生： M M i Xi,（3）The magnitude of the internal forces due to temperature changes is in direct proportion to the absolute value of the flexural rigidity EI of the members; 温度改变时超静定结构中引起内力, 且内力与刚度绝对值成 正比； Increasing rigidity of cross section for the members will not enhance its stress condition caused by its temperature changes; 增加截面刚度不能提高结构抵抗温度变化的能力； The tensile stress due to temperature changes occurs on the side of the member where the temperature rise is lower. 拉应力出现在(超静定结构中)温度较低一侧；,