The accelerated bridge construction (ABC) method has become increasingly popular in recent decades because it creates few traffic disruptions, minimal environmental impacts, and lower cycle costs. The self-propelled modular transporter (SPMT) is an ABC method. In the SPMT method, the support position is a key factor during transportation because the support position changes the boundary conditions and consequently changes the stress distribution of the original bridge. Unreasonable stress distribution may cause a collapse of the demolished bridge and permanent damage to the new built bridge during the transportation process. In the present study, an overpass bridge is demolished and replaced due to the expansion of an expressway. The SPMT method is adopted for rapid demolition and construction because it can greatly reduce traffic interruptions and costs. An optimization strategy of SPMT support positions is proposed by introducing a safety factor. The influence of the support positions of the SPMT on the internal force, stress, deflection, and resistance to overturning of both the demolished and new built bridges during the transport process is considered in the safety factor. Finally, an overpass bridge is taken as a case study. The optimal support positions of both demolished and new built bridges are obtained, and the demolition and rebuilding of the bridge are successfully completed using the SPMT method.

At present, there are few research results on the seismic response of the track system on railway suspension bridges, and relevant research has not yet formed a certain standard. In order to provide a certain reference for the development of industry standards and the design of seamless lines on railway suspension bridges, based on the large-mass method based on multi-point excitation, taking China’s longest high-speed railway suspension bridge-Wufengshan Yangtze River Bridge as the engineering background, a beam–rail integrated dynamic calculation space model was established with ANSYS, and the influence of traveling wave effect on the beam-rail interaction of large span suspension bridges was studied. The study shows that: the traveling wave effect will increase the relative displacement of the beam and rail, and then increase the stress of the rail; the traveling wave effect will cause the stress of the rail far from the source measurement to lag behind the stress of the rail near the source side, and the lag phenomenon gradually disappears with the increase of the apparent wave speed; the traveling wave effect has a greater effect on the displacement of the main bridge end than that of the approach bridge end; the longitudinal displacement of the main bridge end on the north and south side keeps changing synchronously under high apparent wave speed and consistent excitation, and no longer keeps changing synchronously under low apparent wave speed. The longitudinal displacement of the north-south side of the main bridge end keeps changing synchronously at high apparent wave speed and consistent excitation, but no longer at low apparent wave speed.