结构力学英文PPT学习教案

1、会计学1 结构力学英文结构力学英文 第1页/共14页 (2)Geometrically unstable system Under the action of the loads, the system will change its shape and its location if the small deformations of the members are neglected as shown in fig,2.2 Corresponding to geometrically stable and unstable system, there are internally stab

2、le and unstable systems as well. A structure is considered to be internally stable, or rigid, if it maintains its shape and remains a rigid body when detached from the supports 第2页/共14页 Conversely , a structure is termed internally unstable if it cannot maintain its shape and may undergo large displ

3、acements under small disturbances when not supported externally. Purpose of analyzing geometric construction of structures is as following: (1) To estimate whether or not a system is geometrically stable, so as to determine whether the system can be used as a structure or not; (2) To discuss geometr

4、ic construction rules of stable systems. 第3页/共14页 第4页/共14页 第5页/共14页 第6页/共14页 第7页/共14页 The hinged support can restrict the translation of joint A in verticar and horizontal directions but cannot prevent the rotation about joint A, i.e., one hinged support reduces two degrees of freedom and is equival

5、ent to two restraints Restrict in vertical and horizontal directions and the rotation about A three restraints (2 )Connecting restraints between rigid bodies we will pay more attention to connecting restraints between two rigid bodies. One rigid body has three degrees of freedom and two independent rigid bodies have six degrees of freedom in a planar coordinate system, when connecting them together, their degrees of freedom would be reduced. Now we will discuss the equivalent restraints of a few kinds