| According to the problem of commonly existed cracks and the late excessive deflection in continuous steel truss-concrete bridge,which depends on the Ministry of transport project “ the basic theory research of constructing the extra-large-span steel truss-concrete composite continuous rigid frame bridge”.It is relied on the prefabricated steel truss-concrete composite continuous rigid frame bridge proposed by Professor Zhixiang Zhou,and this paper leads a system research to the mechanical behavior of bridge during the construction based on a prefabricated steel truss-concrete composite continuous rigid frame bridge with 386 m main span.The main research work includes:(1)Elaborated the fundamental conception and structural characteristics of the PSTC.Four construction methods have been discussed: synchronously construct the steel truss and deck panel by cantilever assembly method;weld deck panel on the steel truss after closure in multiple batches;weld deck panel on the steel truss after closure in small batches;weld deck panel on the steel truss after closure in one batch.(2)Considering the construction stage,the space member system element finite model of the 386 m main span bridge has been established.The strained condition,deformation regular and the difficulty in construction of four programs have been discussed.The strain of each bar has not achieved the bound during the whole construction phase and the serviceability limit stage,while the deck panel has been welded on the steel truss after closure in six batches.(3)According to the program that the weld deck panel on the steel truss in six batches,a simplified analysis model has been established to analyze whether the deck panel would warp during the pre-stressed stretching stage.The result shows the up-warpage caused by pre-stressing was significantly less than the down-warpage caused by gravity,i.e.the deck panel can automatically fit with the top surface of the steel truss under its own weight.(4)This paper has studied the impact of two assumed construction errors on the structural internal force,which are decreased 10% pre-stressing force and lost 50% welding seam efficacy.It suggests that each cross section compressive stress reserves have been reduced with pre-stressing force decreased 10%,especially near the edge of stressing with pre-stressing force;the strain of deck panel and top chord have changed obviously while other bars observed tiny change with welding seam lost 50% efficacy.(5)The linear stability analysis of the steel truss during three stages has been proposed as follows: the maximum hanging arm installation stage based on steel truss,the deck board installation stage and the POSTCS.The results have shown the lateral stiffness of the structure is far less than longitudinal stiffness,outside instability surface appeared at the firstly stage of each construction,while the structural stability safety factor corresponded with the requirement;added lateral coupling system in pier top of two pieces of the steel trusses and the four points respectively can obviously improve lateral stability of bridge during construction;when the height of piers are over 100 m,in order to ensure the stablility of structure,the horizontal linkages between the double thin-wall pier is recommended to be set. |
