Comparative Study of a Conventional Bridge and a Cable-Stayed Bridge Using STAAD.Pro

•            Both STAAD.Pro models were verified at an equal overall length of 541.8 m, allowing structural differences to be attributed to load-transfer mechanism rather than length mismatch. •            The RCC bridge, arranged as seven 72.914 m spans plus one 31.5 m span, produced a maximum bending moment of 14,890 kN·m, maximum shear of 2,180 kN, and total vertical reaction of 16,860 kN. •            The cable-stayed bridge, with a 285.6 m main span and two 128.1 m side spans, produced a maximum bending moment of 67,356.56 kN·m, maximum shear of 5,778.45 kN, and a self-weight vertical reaction of approximately 181,000 kN. •            Raw percentage differences of 352.36% (bending moment), 165.07% (shear), and 973.55% (reaction) are consequences of the cable-stayed bridge's much larger tributary deck area concentrated at fewer support points, not evidence of structural inefficiency. •            Modal results show the RCC bridge is a stiff, short-period system (first mode 1.295 Hz, 0.772 s) while the cable-stayed bridge is a flexible, long-period system (first mode 0.09 Hz, 11.16 s), consistent with the general dynamic character of cable-supported long-span structures reported in the literature. •            The RCC bridge's reported mid-span deflection of 32.5 mm remains within its stated 50 mm serviceability limit; an equivalent cable-stayed deflection value could not be obtained from the source data. •            Global load-reaction equilibrium was independently verified for the cable-stayed self-weight case, confirming model stability for that load case. •            The RCC bridge is the structurally and economically rational choice for a medium-span, multiply-supported crossing of this type, while the cable-stayed configuration is justified specifically where a single, unobstructed 285-290 m span is a governing requirement (navigation clearance, obstacle-free crossing). •            No single "optimum" system emerges from raw force comparison alone; bridge-type selection must weigh span requirement, foundation conditions, construction capability, and life-cycle maintenance alongside the force magnitudes reported here. •            From a sustainability and material-use standpoint, the cable-stayed system achieves a substantially longer unsupported span per unit of foundation footprint, which is significant where minimising in-water or in-ground disturbance is a design priority, although a formal material-quantity or embodied-carbon comparison was outside the scope of the available data.

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