English：

Early design of half-through tied arch bridges in China inadequately addressed thereplaceability of tie rods, necessitating post-deterioration cutting and non-original-position replacementstrategies to maintain structural capacity. This paper investigates tie rod replacement and constructionmonitoring technologies based on the rehabilitation project of the Second Zhongshan Bridge,which is a（41+ 125 + 41） m three-span wind-bracing-free steel-concrete composite half-through tied arch bridge.Technical challenges, construction schemes, finite element analysis, monitoring parameters, and controlstrategies are comprehensively analyzed. A novel cross-construction protocol integrating graded tensioningof new tie rods with phased cutting of existing tie rods is proposed. A monitoring framework isestablished, prioritizing cable force control as the primary strategy, critical displacement monitoring asthe core mechanism, and structural stress verification as the auxiliary criterion. Finite element analysisand field implementation show that the proposed methodology achieves precise control over arch abutmenthorizontal displacement （≤1mm） and vertical displacements of arch ribs and bridge deck （≤10mm），with minimal stress variations in critical arch sections. The smooth force transfer between old and new tierods ensures structural safety throughout replacement operations.