<![CDATA[Plain concrete arch bridges (PCABs) remain an important component of transportation infrastructure because of their structural efficiency and durability. However, many existing PCABs have exceeded their intended service life, highlighting the need for reliable methods to evaluate their load-bearing capacity (LBC). This study investigates the LBC and structural behavior of PCABs through integrated experimental and numerical analyses. Two PCAB specimens were tested under one-point and two-point loading conditions, while the ultimate load, vertical displacement, lateral concrete strain, and failure modes were recorded. A three-dimensional finite element model was developed in ABAQUS using the Concrete Damaged Plasticity (CDP) model and validated against the experimental results. The numerical predictions closely matched the experimental observations, with deviations of less than 2.2% in the ultimate load, confirming the accuracy and reliability of the proposed model. A comprehensive parametric study was subsequently performed to evaluate the influence of arch thickness, rise, and loading configuration on structural performance. The experimental results showed that two-point loading increased the ultimate load-bearing capacity by approximately 154% compared with one-point loading. Increasing the arch thickness enhanced the load-bearing capacity by up to 39.1% under one-point loading and 57.1% under two-point loading. The proposed experimentally validated framework provides a practical and reliable tool for the structural assessment and design optimization of existing plain concrete arch bridges.]]>
