Research Of Structural Prestress Synthetic Reinforcing Approach And Its Application In Bridge Engineering

Stress difference between old and new material (which might be stress lagging or stress preact of new material) is the most common technological problem but also must be considered. Many bridge reinforcing workers face a key problem that how to balance between old and new material to make structure (or section) reasonably bear stress, which aims to avoid stress difference. In this case, bridge reinforcing become active from passive, and become synthetical method (comprising various single method) from single reinforcing method. The following five achievements have been acquired in this article by means of model test, theoretical analysis and field experiment.1. In this article’Structure Prestress’is analyzed and defined based on the method of pre-bending prestressing and loading features of old and new material in stages in bridge reinforcing. Then core idea and content of structure prestress synthetic reinforcing approach method are systematically analyzed and defined. Meanwhile advantages and feasibility of this approach are detailedly analyzed based on the purpose and basic principle of bridge reinforcing design. Besides, necessity of this approach is also detailedly analyzed based on current situation of dangerous bridges.2. Effect of ultimate load, stress deformation, failure mechanism and unload rate on different unload levels is studied on ultimate load and failure mode of strengthened reinforced concrete girders, which is according to model test and finite element analysis of 3 groups of reinforced concrete girders. Researches show that concrete stress and reinforcement stress of strengthened reinforced concrete girders are very different on different unload rate, which resulting in significant difference of strengthened reinforced concrete girders bearing capacity in normal use but similar ultimate bearing capacity. Strengthened reinforced concrete girders bearing capacity should be calculated by stages to consider effect of unload rate. Extended finite element analysis could more accurately simulate stress behavior and cracking process of reinforced concrete girders, so this method can be an effective approach to analyze reinforced concrete girders mechanical property.3. Optimum unload rate corresponding to optimum initial bending moment is defined based in two different limit conditions. Requirement of optimum initial bending moment is also analyzed and defined on two different limit conditions. Solution formula of optimum initial bending moment in two different limit conditions is established according to defined condition and relevant assumption. Then optimum unload rate can be confirmed in condition of appropriate reinforcement parameter. In this process, interrelation between reinforcement layer thickness and optimum initial bending moment is detailedly analyzed. Meanwhile, important issues during design process of bending member are raised.4. Key point of structure prestress synthetic reinforcing approach is systematically analyzed and put forward, which is generally analyzing based on current situation and structure loading features of reinforced bridge. This requires following relevant safety principle, choosing reasonable unload direction and reinforcing order when necessary. A series of simple and efficient unload engineering measures (which is infliction of prestress) are put forward specific to bridges with difficult unload process such as arch bridges and simply support concrete girder bridges, which support engineering application of structure prestress synthetic reinforcing approach.5. Application of structure prestress synthetic reinforcing approach that adopts theory of influence line is in research, which combined with practical maintenance and reinforcement project. Researches show that stress distribution between old and new concrete is reasonable and bearing capacity reserve is high after reinforcement during reinforcement project based on research result in this article. The reinforcement project achieves expected result. Besides, this approach has effective reinforcement effect and good operability.