中文摘要：

考虑几何非线性效应，计算大跨度公铁斜拉桥承载能力和正常使用极限状态下的结构变形和内力．采用分步迭代调索方法计算成桥索力，建立迭代修正Ernst公式，在索力计算和结构内力计算中考虑垂度效应，研究拉索垂度效应、梁柱效应和大位移效应对斜拉桥极限状态时内力的影响．研究结果表明，几何非线性对大跨度公铁斜拉桥的内力影响比较显著，线性计算结果与非线性计算结果相比偏不安全，在公铁斜拉桥结构设计中，必须计入几何非线性的影响．各种非线性因素中斜拉索的垂度效应最为显著，其影响效应随外荷载的增大而变大．

英文摘要：

Internal forces and deformation of long span highway and railway cable-stayed bridge in the ultimate limit state and serviceability limit state are calculated. Considering geometrical nonlinearity behavior, the cable force under dead load is calculated by step iterative algorithm. The iterative modified Ernst formula is established and used in calculation of rea- sonable cable force and the internal force of structure. The cable sag effect, the beam-column effect and the large displacement effect are taken into account in the study. The results indicate that geometrical nonlinearity significantly influences the internal force of long span highway and railway cable-stayed bridge, so the geometrical nonlinearity must be consid- ered in design. Among various nonlinear factors, the cable sag effect is the most significant, and the effect enhances with increasing load.