結構：由桿件、結點和支座組成的桿件體系Structure consists of members, joints and supports.
結構必須是在不考慮材料變形的條件下能保持幾何形狀和位置不變的桿件體系。
Structure must maintain its geometric shape and positions without consideration of the deformation of materials.
在不考慮材料變形的條件下，桿件體系可分為如下兩種類型
If the deformation of materials is neglected, then framed systems can be classified into two categories：
幾何不變體系 ( geometrically stable system )
幾何可變體系( geometrically unstable system )
幾何不變體系 ( geometrically stable system )
在任意荷載作用下，幾何形狀及位置均
保持不變的體系。（不考慮材料的變形）
Under the action of any loads, the system still maintain its shape and remains its location if the deformations of the members are neglected.
幾何可變體系( geometrically unstable system )
在一般荷載作用下，幾何形狀及位置將發(fā)生改變的體系。（不考慮材料的變形） Under the action of any loads, the system will change its shape and its location if the deformations of the members are neglected.
體系組成分析的目的
The purpose of geometric Construction analysis：
1.判定體系是否幾何
不變to estimate whether or not a system is geometrically stable；
2.研究幾何不變體系的組成規(guī)則to discuss the geometric construction rules of stable systems；3. 區(qū)分靜定和超靜定的組成distinguish statically determinate structures and statically indeterminate structures 。
