This paper examines the optimization problem of cable force in the construction phase of single-tower cable-stayed bridges, transforming it into an unconstrained problem that aims to control the vertical displacement of main beam nodes and the horizontal displacement of tower nodes. By introducing penalty terms, the constrained optimization problem is converted into an unconstrained one. The conjugate gradient algorithm is adopted to solve the unconstrained problem due to its simplicity, low storage requirement, and effectiveness in various engineering applications such as image restoration and financial modeling. However, under the Wolfe-Powell inexact line search, the global convergence of this algorithm usually depends on a Lipschitz continuity condition for convex/nonconvex functions. This paper investigates whether this condition can be relaxed, and analyzes the direction suggested by Yuan and Zhang (JCAM, 2005) for unconstrained problems. The paper features a designed conjugate gradient algorithm, iteration directions that guarantee sufficient descent and trust region properties, and proof of global convergence without the Lipschitz continuity condition. Numerical experiments are performed for optimization problems, image restoration, and the Muskingum model.