| An innovative light-weight steel-UHPC(Ultra-high performance concrete) composite bridge girder which can be applied to long span bridges was proposed by Prof. SHAO Xudong to deal with the problems of prestressed concrete girders, steel girders, steel-concrete composite bridge girders, which was caused by traditional material and the structure itself. The light-weight composite girder has the advantages of high strength, low self-weight, structure simple, convenient and accelerated construction, and remarkable life-cycle economic benefit, as well as it's great application prospects. This paper conducted preliminary investigations on the mechanical performance of UHPC deck from aspects of finite element analysis, practical calculation, and full-scale strip model test.South Dongting Lake Bridge of Yiyang-Nanxian Expressway in Hunan Province, which is a cable-stayed bridge with double pylons and double cable planes, uses light-weight steel-UHPC composite bridge girder for the first time. Three kinds of bridge deck design including rectangular slab, thinner rectangular slab with longitudinal ribs and Waffle deck panel are proposed. Establishing analysis model of Standard segment of cable-stayed bridge respectively which is based on three kinds of bridge deck structure, result comparison indicates that Waffle deck panel has better mechanical performance than others. Under vehicle load, Waffle deck has the maximum overall stiffness and local stiffness; when compared to rectangular slab, the longitudinal stress in bridge deck's lower margin increases slightly, the longitudinal and transversal stress in bridge deck panel's upper and lower margin decreases remarkably; Waffle deck has the minimum high stress area, and the longitudinal connections are under low stress state; during crack resistance design, rectangular slab needs dense reinforcement along bridge transverse direction, while deck panel with longitudinal ribs only needs reinforcement in the ribs. Under fatigue load, Waffle deck has the best fatigue property, the longitudinal and transversal stress amplitude in deck panel's upper margin decreases remarkably. Therefore, deck of the South Dongting Lake Bridge with light-weight steel-UHPC composite girder is suggested to adopt the Waffle deck panel system, average thick 14cm.Stress in multi-span continuous unidirectional UHPC bridge deck's lower margin is calculated based on elementary beam theory, results show that, when the span of simply supported bridge deck is assigned 0.577L, influence line of loads transverse distribution in terms of rigid connected beam method is basically the same as which's got from Finite Element Analysis; after that load vehicle in the most disadvantageous position, calculate transverse distribution coefficient, and the maximum tensile stress of simply supported deck, then get corresponding stress of continuous deck based on the support condition between hinged joint and rigid joint. Comparison result of practical calculation with finite element analysis, results of deck panel with longitudinal ribs has higher accuracy with a maximum deviation of 10% on the safe side, although results of rectangular slab have relatively larger deviations, the calculation method needs improvement.Based on UHPC deck panel,10 full size stripe test specimens were designed to process static tests, research show that, tensile reinforcement ratios, steel bar diameter, diameter and length of linear fiber have little effect on crack stress, while steel fiber with hooked end significantly increases the crack stress, crack stress of reinforced UHPC beam with hooked fiber and linear fiber under positive moment are respectively 19.4MPa,10.6MPa, the former is 83% higher than the latter, crack stress of reinforced UHPC beam with hooked fiber and linear fiber under negative moment are respectively 13.8MPa,8.4MPa, the former is 64% higher than the latter, crack stress of steel-hooked fibre UHPC composite slab is up to 44.0MPa, which is 2.29 times of reinforced UHPC beam. In positive bending moment test, crack stress of reinforced UHPC beam with hooked fiber are 1.45 times of design tensile stress of Waffle deck panel, ultimate positive bending moment of reinforced UHPC beam with hooked fiber is 2.8 times of design moment of Waffle deck panel. In negative bending moment test, crack stress of reinforced UHPC beam with hooked fiber are 1.66 times of design tensile stress of Waffle deck panel, ultimate positive bending moment of reinforced UHPC beam with linear fiber is 5.9 times of design moment of Waffle deck panel. Calculation flexural capacity of reinforced UHPC beam agree well with the experimental results, which can meet the design moment of Waffle deck panel under ultimate limit state, calculation shear capacity of steel-UHPC composite slab agree well with the experimental results, while calculation flexural capacity is under estimated. And the forecast fatigue life of UHPC Waffle deck panel is much greater than 2 million cycles based on S-N curve. Waffle deck panel System based on the reinforced UHPC beam with hooked fibre can bear the allowable force under both serviceability limit state and ultimate limit state load combination. |
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