Abstract: This year marks the 110th anniversary of the birth of Academician Qian Lingxi. In commemoration of our esteemed teacher's achievements, this paper explores stories related to the Zhaozhou Bridge, from which the concept of “physical iteration" can be derived: using physical entities as the carrier, through a cyclic process of “trial-error—verification—correction," achieving structural evolution from repeated “destruction"—“basic safety"—“enhanced safety"—“optimality." This paper formally discusses physical iteration for the first time. As the precursor of numerical iteration, it addressed the challenges of human engineering structural safety before the advent of mechanics. However, physical iteration came at an extremely high cost. Today, mechanical numerical iteration has replaced physical iteration and become a necessary prerequisite for engineering structural design. Leveraging computational mechanics and structural optimization methods, through mathematical modeling, cyclic solving, and parameter iteration, it completes the rational design process of modern engineering structures.