建立了分段成形桥梁任意施工过程的力学平衡方程，由力学平衡方程推演出分阶段施工桥梁过程控制的核心是构件单元的无应力状态量。通过单元的无应力状态量的控制和调整解决了分阶段施工桥梁的安装计算问题；利用无应力状态量一定的前提下，内力和位移与施工过程无关的原理，实现了施工中多工序并行作业，解决了施工中临时荷载和温度影响的自动过滤问题。

This paper establishes a mechanical equilibrium equation for structure in any construction process of bridge formed by stages, and thus concludes that the core of process control for stage-constructed bridge is the quantity of unstressed state of structural elements. The control and adjustment of quantity of unstressed state of the structural elements provides a solution to the problem of rection calculation for bridge constructed by stages. Based on the principle that internal force and displacement have nothing to do with the construction process on the premise of a constant quantity of unstressed state, parallel operation of multiple working procedures can be put into practice, and the automatic filtration of influences from temporary load and temperature during construction can be therefore well realized.