Development and Supercomputing-Based Simulation Optimization of a Rotation System for Long-Cantilever Cap Beams Supported by Double-Column Piers in Urban Expressway Viaducts

Conventional methods for constructing long-cantilever cap beams supported by double-column piers in urban expressway viaducts lead to substantial traffic disruption, inefficient use of constrained urban space, and high temporary construction costs. To address this, we propose a modular reusable rotation system together with a corresponding construction method. A five-stage construction procedure was developed, comprising system installation, offset casting, rotational construction, connection-segment construction, and system dismantling. Using the eastward extension of the Gongye North Road Expressway in Jinan as the engineering case, finite element models of the split and integrated systems were established using the DonSys supercomputing simulation platform to investigate the static responses at different construction stages. The stresses and deformations of the rotation system were compared before and after introducing auxiliary supports comprising dual-purpose reaction supports and sand jacks. The results indicate that, under the specified loads and boundary conditions, the load-bearing rigid frame exhibits higher stresses and vertical displacements under the split system condition than under the integrated system condition. With the auxiliary supports installed, part of the vertical load is transferred through the bottom formwork and sand jacks to the reaction supports, reducing the load carried by the rigid frame. Consequently, the maximum tensile and compressive stresses decrease from 188.20 and 202.61 MPa to 67.56 and 71.14 MPa, respectively, while the maximum vertical displacement decreases from 7.54 to 2.60 mm, corresponding to a reduction of 65.52%. These findings provide a reference for the structural design and construction deformation control of similar cap beam rotation systems under constrained site conditions. The actual construction response and reusability of the system require further validation through testing and field monitoring.