Research On Improving The Performance Of Simply-Supported Girder Bridges With Continuous Slab-decks

To satisfy the need of constructing Changtianwan Bridge on "Chongqing-Linshui Expressway", the author has conducted research on the continuous technique and performance enhancement of simple-supported girder bridges with continuous slab-decks and focused on the linear elastic analysis and spatial nonlinear analysis of the mechanical behavior and deformation of the slab-deck continuous structure caused by live load, secondary dead load, as well as environmental temperature variation. Though the analysis, it is found that the structure of simple-supported girder bridges with continuous slab-decks which will result in highly complicated mechanical behavior for it is just situated exactly of the part of the maximum deflection (girder toe rotation and shaft expansion and shrinkage) of the main beam, along with the stagger deflection of two neighboring bridge-holes caused by asynchronously contracting the elastic plastic bearing. The tensile stress of this structure under any construction condition has exceeded the strength of the ultimate against tension of concrete. Hence, after a short period, irregular cracks will appear in the continuous cracks and the surrounding concrete after the structure being put in use. When time passes by, those parts with early stage damages will gradually turn into crushes and pits which not only influence the safety of traffic and also shorten the service life of the bridge.In view of this fact, in the point of how to actively adjust the mechanical behavior of the structure, and deduce the maximum stress formula under all the construction environment of simple-supported girder bridges with continuous slab-decks according to linear elasticity theory, the author tries to provide theoretical basis for the improvement of the simple-supported girder bridge with continuous slab-decks.Through investigation, analysis and comparison, three methods are finally employed. They are "Polyacrylonitrile fibre concrete", "modified epoxy concrete of the low module of elasticity" and "sticking GFRP sheet on the top-fringe of the structure. These three methods are used respectively combining with the method of strengthening connection steel.By means of spatial nonlinear simulation analysis and fatigue test on the members, the improved structure, compared with the unimproved, has got great elongation in terms of the time of first-crack and its fatigue life. Among those three methods, the time of first-crack appearance is the latest by way of "Putting GFRP sheets on the region of negative bending moment", and the fatigue life is the longest. With GERP, the reflective cracks on the asphalt concert surfacing are also avoided.The second method which is not convenient for construction is highly costly and susceptible by seasons while the other two methods are on the contrary. In order to make clear the actual behavior of different kinds of continuous slabs, these methods have been conducted in Changtianwan Bridge.