为便于两岸接线线形，部分大跨度板桁组合梁斜拉桥采用了横向非对称的车道布置形式。然而，偏心布载会引起主梁显著的扭转效应，传统索力优化方法难以有效考虑这一影响。为减小横向非对称性布置引起的不利效应，本文基于左右对称截面竖向弯曲与横向弯扭相互解耦的特性，提出了一种考虑横向非对称性的斜拉桥成桥索力分步优化策略，该策略依次进行平均索力优化与索力差优化。具体而言，本文首先讨论板桁组合梁与单梁模型的等效策略以便进行索力优化分析，随后利用B样条曲线替代原有的密集斜拉索索力变量，以最小应变能为优化目标，使用梯度优化算法对样条曲线控制点进行优化。优化结果表明，索力差优化能够有效平衡主梁自重引起的偏心扭矩并显著减小主梁扭转角，使桥梁符合预期的合理成桥内力状态和位形。同时，分步优化策略通过问题的解耦和降维有效降低了分析开销，并兼顾了优化精度与收敛稳定性。

To accommodate the alignment of approach roads on both sides, some long-span cable-stayed bridges with truss-deck composite girders adopt an asymmetric cross-sectional arrangement of traffic lanes. This eccentric distribution of dead load induces significant torsional effects that conventional cable-force-optimization methods fail to address adequately. To overcome this limitation, this study proposes a novel stepwise cable force optimization framework to mitigate the adverse impacts of dead-load eccentricity. The proposed strategy exploits the decoupled characteristics of vertical bending and lateral bending-torsion in left-right symmetric cross-sections, sequentially performing average cable force optimization followed by differential cable force optimization. Specifically, this work investigates the equivalence principle that allows the plate–truss composite girder to be represented by a single-beam model for efficient analysis. Then, a B-spline curve is employed to approximate the dense cable force distribution using a limited number of control points, and a gradient-based algorithm is utilized to minimize the structural strain energy. The results demonstrate that the proposed method effectively reduces the torsional moment and deformation angle induced by eccentric dead loads, leading to a more rational internal force distribution and desired configuration. Moreover, the stepwise optimization strategy significantly reduces computational cost through problem decoupling and dimensionality reduction, while maintaining optimization accuracy and convergence stability.