Study On Static And Dynamic Performance Of Long-span Continuous Rigid Frame Bridge With Stiffened Steel Truss

The continuous rigid frame bridge is widely used for its large spanning capacity and convenient construction.Diseases of excessive vertical deflection and cracking of girders are common in continuous rigid frame bridges.To solve These problems,a new structural form,the stiffened steel truss continuous rigid frame bridge is proposed,and the combined structure is composed of a stiffened steel truss and a concrete box girder.The paper relies on a proposed trans-Yellow River Bridge as project.The width of the main bridge is106m+192m+106m.The Spatial Finite Element Model of Full Bridge is established by Using Finite Element Software Midas Civil.The influence of steel truss on the static and dynamic performance of continuous rigid frame bridge is optimized,and the influence parameters of stiffened steel truss are optimized.The main work and results are as follows.(1)The three-dimensional finite element model of stiffened steel continuous rigid frame bridge and continuous rigid frame bridge is established,and the displacement,internal force and stress state of the model under dead load,live load and shrinkage creep are calculated respectively.Comparing with the continuous rigid frame bridge,the displacement and internal force of the composite structure decrease,and the creep displacement in the middle span decreases by 24.12 mm,and the change amplitude reaches 49.33%.The bending moment of mid-span decreases by 67706.16 kN.m,and the change amplitude reaches 102.80%.The stress difference between upper and lower edges of main girder in mid-span decreases by 2.60 MPa,and the change amplitude reaches 117.65%.the rigidity of the continuous rigid frame bridge and structural stress are improved by stiffened steel truss,but the structural creep is effectively reduced.(2)Several groups of finite element models are established to analyze the influence of parameters such as truss form,stiffening range and truss height on the displacement and internal force of concrete girder.The stiffening length of 120 m and the arrangement of triangular web members without vertical bars are the most reasonable,effective and economical stiffening steel trusses.(3)The models of stiffened steel truss continuous rigid frame bridge and continuous rigid frame bridge are established.The natural vibration period and mode shapes of the bridge structure are calculated by multiple Ritz vector method.The displacement and internal force of the structure under earthquake are analyzed and calculated by response spectrum analysis method and time history analysis method.Under the action of transverse seismic force,the vertical displacement of the middle span of the stiffened steel truss continuous rigid frame bridge decreases by 19.67 mm,the change amplitude is 25.6%,and the horizontal displacement of the main pier decreases by 9.44 mm,the change amplitude is 24.8%.The research of this paper provides a reference and basis for the application of the new stiffened steel truss continuous rigid frame bridge in the design of new bridges and the reinforcement of old bridges in China.