An Experimental and Numerical Study on the Lateral Stiffness Limits of Straddle-type Monorail Tour-transit Systems

The development of straddle-type monorail tour-transit systems (MTTSs) has received keen attention, raising the need for revisions on related design codes. This work presents a comprehensive assessment of the lateral stiffness limit of steel substructures in MTTSs. Firstly, a wind‒vehicle‒bridge coupling model was established, integrating multibody dynamics and finite element methods. This model was then validated against field test results, considering measured track irregularities as the excitation. Afterwards, a trend analysis and a variance-based sensitivity analysis was performed to investigate the effect of various factors on the dynamic response of MTTS. Referring to existing specifications, an evaluation index for the lateral stiffness of pier columns and track beams was proposed. Results indicate that the pier height significantly impacts the lateral displacement of the pier top, accounting for 87% of the first-order sensitivity index and 75% of the total sensitivity index. In comparison, the lateral stiffness of track beams contributes over 70% to the maximum lateral acceleration and displacement at the mid-span. Finally, the lateral limited values for the displacement at the pier top and the deflection–span ratio of the track beam were determined as 8.04 mm and L/4200, respectively. These findings can serve as valuable references for future research and designs in this field.