一.超靜定結(jié)構(gòu)的靜力特征和幾何特征The static and geometrical features of statically independent structures (SIS)
幾何特征:有多余約束的幾何不變體系。Geometrical features: stable systems with redundant restraints.
靜力特征:僅由靜力平衡方程不能求出所有內(nèi)力和反力. Static features: Internal forces and reactions can not be determined only by Static equilibrium conditions
超靜定問(wèn)題的求解要同時(shí)考慮結(jié)構(gòu)的“變形、本構(gòu)、平衡”.Deformation and equilibrium must be considered simultaneously
二.超靜定結(jié)構(gòu)的性質(zhì)The properties of SIS
1.內(nèi)力與材料的物理性質(zhì)、截面的幾何形狀和尺寸有關(guān)。
The internal forces are related with the properties of materials, the
Geometrical form and sizes of the cross-section of the members
2.溫度變化、支座移動(dòng)一般會(huì)產(chǎn)生內(nèi)力。Temperature change, movements of supports usually cause internal forces.
與靜定結(jié)構(gòu)相比, 超靜定結(jié)構(gòu)的優(yōu)點(diǎn)為T(mén)he advantages of SIS :
1.內(nèi)力分布均勻the distribution of internal forces are distributed more uniformly;
2.抵抗破壞的能力強(qiáng)More resistance to fracture
三.超靜定結(jié)構(gòu)的計(jì)算方法Computation methods
1.力法force method----以多余約束力作為基本未知量
Take redundant forces as primary unknowns。
2.位移法displacement method-以結(jié)點(diǎn)位移作為基本未
知量. Take joint displacements as primary unknowns。
3.混合法combined method----以結(jié)點(diǎn)位移和多余約束力作為基本未知量.
4.力矩分配法moment distribution method----
近似計(jì)算方法approximation method.
5.矩陣位移法matrix displacement method----
結(jié)構(gòu)矩陣分析法之一.
力法等方法的基本思想the idea of force method:
1.找出未知問(wèn)題不能求解的原因find the reasons why
we can not solve the problem,
2.將其化成會(huì)求解的問(wèn)題 transform it into solvable
problem,
3.找出改造后的問(wèn)題與原問(wèn)題的差別find the difference
between the transformed and original problems,
4.消除差別后,改造后的問(wèn)題的解即為原問(wèn)題的解
removing the difference, the transformed problem becomes
solvable.
