弧长法中初始荷载增量参数符号确定准则的改进

在结构非线性全过程跟踪分析中，弧长控制类方法由于其概念简单明了、计算方便可靠，目前已成为一种最主要的跟踪技术。在该方法的使用过程中，初始荷载增量参数符号的确定非常重要，它决定了当前跟踪分析是向前还是返回(Tracing-back)。本文在比较现有准则的基础上，提出了一种依据当前刚度参数进行判定的新准则，并以两个经典算例为例进行考证，其中一个算例同时存在跳跃(Snap-Through)及跳回(Snap-Back)现象且具有分枝路径。分析结果表明，该准则简单实用，在跟踪复杂失稳过程中是非常有效的，具有很好的适用性。

DISCUSSION ON THE CRITERIA FOR DETERMINATION OF INITIAL LOADING PARAMETER IN ARC-LENGTH METHODS

At present, the arc-length methods are dominant tolls in structural nonlinear analysis to trace the complete paths due to its clarity in conception, convenience and reliability in calculation. During the implementation of the arc-length methods, the sign of initial loading increment parameter determines the path direction of the current tracing analysis. In this paper, the criteria for determining the sign of initial loading increment parameter are reviewed and compared, and a new criterion is presented based on the current stiffness parameter. Two examples are used to check the efficiency of the criterion, The snapping-through, snapping-back phenomena and bifurcation paths are included in one of the examples. Results show that the new criterion is simple and effective to trace the complex unstable equilibrium paths.