Research On Fundamental Performance Of Lightweight Composite Bridge Deck With Large U-ribs

Nowadays,orthotropic steel decks have been widely used in bridge engineering.However,fatigue cracking in steel deck and damage in conventional asphalt concrete pavement occur frequently.In order to solve the problems above,a lightweight composite bridge deck that consists of an orthotropic steel deck stiffened with Super Toughness Concrete(called STC)was proposed by our team.As a component that works with steel deck,STC layer can increase the stiffness of deck,because of which an optimization for the deck system is taken into consideration.This paper proposed a lightweight composite bridge deck(called LCD)with large U-ribs replacing the traditional U-ribs.Compared to the LCD with traditional U-ribs,the one with big U-ribs has many advantages:the cost of steel is slightly changed,while the weld length is reduced by a large scale.The main works of this paper are shown as follows:(1)The dimension of LCD with large U-ribs is proposed.Taking a cable-stayed bridge as an example,the feasibility of using a lightweight composite deck deck with large U-ribs is investigated and its mechanical properties are analyzed.FEA software Midas-Civil is used to conduct the global analysis of the cable-stayed bridge whose bridge deck is lightweight composite deck deck with large U-ribs.The internal force and stress level of components under different loads combination are investigated,and the results show that both the internal force and stress level of components does not significantly vary.Finite element analyses of four different systems are conducted to investigate the local mechanical behavior of the new LCD.The results show that,the max vertical displacement of LCD with big U-ribs is close to that of LCD with traditional U-ribs.Meanwhile,stress value in roof of deck in both lcds is much lower than that in the orthotropic steel decks with conventional asphalt concrete pavement.(2)Using hot spot stress method,local finite element model of steel box girder is established by finite element analysis software ANSYS to investigate 6 typical fatigue details.The results show that max stress amplitude in LCD with large U-rib is close to that of LCD with traditional U-ribs,which can all meet the specifications.Stress amplitude of some details is lower than the constant fatigue limit.Finally,the fatigue performance of stud is evaluated using local finite element models,and the results show that the shear stress amplitude can meet the requirements of specification.(3)The fatigue life whose stress amplitude is higher than constant amplitude fatigue limit is calculated,and the numbers that deck can stand the vehicle load is got then.(4)Through the calculation using global and local FEA models,the LCD with large U-rib have a good lateral forcing performancethe.In order to investigate the flexural tensile strength of STC layer in LCD with big U-ribs,a negative bending test was conducted.The result shows that the crack stress is 24.1 MPa,which is much larger than the calculated tensile stress 10.9MPa.The above study implies that lightweight composite bridge deck with big U-ribs has a good fatigue and static behavior.