钢螺旋楼梯结构因其特殊的异形结构，受力情况复杂，使得在进行稳定性设计时，尤其是在确定计算长度时，无法通过传统线性分析来准确预测其力学响应。引入直接分析法以克服这些限制，综合考虑结构整体性和构件初始缺陷，为此类结构的分析和设计提供一种高效且安全的解决方案。以一个具体工程为例，使用NIDA软件进行直接分析法的稳定性研究，并将所得结果与一阶线性分析的结果进行对比。研究考察了在全跨满载、左半侧满载、右半侧满载和不同扇形组合活荷载分布下楼梯结构的力学响应，以及不同支座条件对楼梯结构响应的影响。结果表明，直接分析法得到的最大构件应力比一阶线性分析结果高，应力比达到0.993，相应的竖向位移更为显著，最大为0.348 m，印证了二阶效应的重要性。在设计钢螺旋楼梯结构时，应特别考虑活荷载的不利分布，左半侧满载条件下的设计更为不利。对于活荷载的扇形分布，位于楼梯中跨的扇形区域3和4的影响最大。此外，顶部支座刚度的增加有助于降低应力比，但同时会导致二阶弯矩因二阶效应而增大。研究结果对于指导钢螺旋楼梯结构的分析和设计具有重要意义。

The complex structural behaviors in steel spiral staircases， due to their unique and irregular structures， render traditional linear analysis methods inadequate for accurate prediction of structural responses and stability design， particularly in determining effective lengths. This study employs the direct analysis method （DAM） to overcome these limitations， taking into account the overall structural and member initial imperfections， thus providing an efficient and safe approach for the analysis and design of such structures. A specific engineering project is presented as a case study， utilizing NIDA software to perform a stability investigation via DAM， with results compared against those obtained through linear analysis. The research examines the mechanical responses under full-span loading， left and right half-span loading， and various live load distributions across different sectors， as well as the impact of varying support conditions on the staircase structure. The findings indicate that the maximum component stress determined by DAM exceeds that of first-order linear analysis， with a maximum utilization factor reaching 0.993， and a corresponding vertical displacement that is even more significant， peaking at 0.348 m， confirming the importance of second-order effects. In the design of steel spiral staircases， adverse distributions of live loads， especially under left half-span loading conditions， should be given special consideration. For live load distributions， the impact is greatest in sectors 3 and 4， located at the mid-span of the staircase. Moreover， increasing the stiffness of the top support contributes to a reduced stress ratio while also leading to an increase in bending moments due to second-order effects. This research plays a significant role in guiding the analysis and design of steel spiral staircases.