Stress and deformation response analysis of multi tower continuous span suspension bridge deck pavement under stochastic traffic loads

Multi tower continuous span suspension bridges are an emerging bridge type. The middle tower effect and continuous span effect lead to stiffness distributions substantially different from those of conventional two-tower bridges. The mechanical behavior of steel deck pavement becomes more complex, and systematic investigations under realistic stochastic traffic are lacking. This study takes the Taizhou Yangtze River Bridge as a case study. A full bridge finite element model is established, and the Monte Carlo method is used to simulate actual traffic flow. The amplification effect of stochastic eccentric loading on the torsional response of the main girder is quantified for the first time. Results show that, under stochastic traffic, the most significant displacement responses occur within the 1/4-span to 3/4-span region. The middle tower zone experiences the largest negative bending moment and torsional moment, making it a high-risk area for pavement fatigue cracking. Compared with the Highway Class I code load, the code is generally conservative for bending moment design by about 30%, but it underestimates the torsional effect by approximately 38%. This discrepancy arises from the coupled effects of bridge flexibility, code simplification of eccentric loading, and the spatial clustering of stochastic traffic. It is recommended to increase diaphragm stiffness near the middle tower and optimize the pavement system to enhance torsional and fatigue performance.