Single-Axis Weighing Method for Horizontal Swivel Construction of Wide Bridges

Wide swivel bridges can develop large transverse unbalanced moments, whereas conventional direction-specific weighing requires two tests. This study proposes a single-axis method based on supporting-leg displacements. A rigid body equilibrium model links the post-release supporting-leg-to-slideway gaps to the location of the unbalanced load. The deck is divided into 16 fan-shaped regions; gap patterns identify the active region, and one moment projection measured along a regional boundary bounds the total moment; the sector bisector gives an approximate estimate. A scaled concrete girder model with eight supporting-leg groups was tested under eight counterweight cases. In all eight prescribed model cases, the displacement pattern correctly identified the applied-load region, and the theoretical counterweight moment lay within the interval calculated from the single weighing test. The method was then applied to a 60 m + 60 m, 44 m wide prestressed concrete T-shaped rigid-frame bridge with a flat-hinge bearing. A 25 t counterweight placed 36 m from the rotation center reduced the calculated eccentricity from about 134 mm to about 99 mm. Together, the model cases and engineering example support the feasibility of gap-guided single-axis weighing under the stated conditions.