The invention relates to a method of weakening the combined action of a
bridge deck system participating in a main truss. The method comprises the steps that main truss rod pieces and cross beams are manufactured and assembled; the prestress is symmetrically applied to two ends of main truss chord members, so that the main truss chord members are compressed and deformed;
bridge deck longitudinal beams are manufactured according to the distance of the shortened main truss; after the
bridge deck longitudinal beams are mounted, the prestress which is applied to the two ends of the main truss chord members is removed; the main truss chord members recover the
compressive deformation to drive the bridge
deck cross beams to deform simultaneously; the deformation of the bridge
deck cross beams is subjected to the restraint of the bridge
deck longitudinal beams, the bridge deck cross beams produce the bending moments, and the directions of the bending moments are opposite to the directions of bending moments of the bridge deck cross beams, which are produced when the bridge deck
system participates into the mutual stress of the main truss chord members; when the bridge deck
system participates into the combined action of the main truss chord members, the produced internal force is offset by the internal force which is produced by the prestress in an earlier stage, the combined action of bridge deck system participating in the main truss is weakened, and the stress performance of the longitudinal beams and the cross beams is improved. Due to the adoption of the method, the cross sections of the bridge deck cross beams are reduced and simplified, the connection structures of the cross beams and the main truss chord members are simple, steel is saved, the used amount is small, and the later maintenance
workload is little.