Construction Control of Temporary Steel Arch Falsework for a Long-Span Box Arch Bridge in a V-Shaped Canyon

Construction of a long-span concrete arch in a V-shaped canyon requires coordinated control of the temporary falsework, erection stays and closure geometry. This study examines the temporary angle-steel truss falsework used for the Nujiang River reinforced-concrete box arch bridge, which has a 100 m clear span. A towerless rear-anchorage arrangement, construction-stage finite element analysis and a BIM-assisted geometric-control framework are presented. The preloading calculation uses a maximum design water-bag mass of 2480.6 t and gives a maximum displacement magnitude of 101 mm and a peak model stress magnitude of 218.4 MPa. Separately, preloading survey records at 20 points show downward elevation changes of 23–136 mm after three days and unloading recoveries of 14–71 mm. A nominal anchorage comparison is formulated using the adopted pile geometry and shaft-resistance parameters. Numerical closure-length cases illustrate the influence of geometric compatibility on the formed falsework, while three initial-tension histories illustrate the redistribution of erection-stay forces and final deflection profiles. The proposed control framework relates measurements to construction-stage targets through explicit reference states and local force–geometry sensitivities. The study provides a case-based procedure for organising geometric control and the associated structural checks during segmental falsework erection.