Research On The Technology Of Repairing The New And Old Concrete Bonding Interface Of Defective Old Railway Bridge

Since the completion and operation of the old railway bridge,under the influence of external environment,construction quality and other conditions,there have been a lot of disease problems,so that the old railway bridge has developed into a defective old railway bridge.Under the condition of long time acco MPanied by disease,it will cause potential danger to the line operation.Therefore,it is very important to strengthen and repair defective old railway Bridges.The bridge type widely used in old railway Bridges is simply supported girder with π-shaped section.Therefore,it is urgent to study the disease characteristics of the girder body with this type of section.In the maintenance of old railway Bridges in the past,more attention was paid to the bearing capacity of the whole bridge and the maintenance and reinforcement,but the bearing capacity of small bridge components(such as inner bridge deck,etc.)was often not paid enough attention,and the diseases of small components also had an important i MPact on the safe operation of railway.Therefore,it is of great significance to analyze the diseases and check the bearing capacity of these parts.In the maintenance of old railway Bridges in the past,more attention was paid to the bearing capacity of the whole bridge and the maintenance and reinforcement,but the bearing capacity of small bridge components(such as inner bridge deck,etc.)was often not paid enough attention,and the diseases of small components also had an important i MPact on the safe operation of railway.Therefore,it is of great significance to analyze the diseases and check the bearing capacity of these parts.In this paper,a railway station in northwest area of the railway bridge beam PI section bridge disease bridge reinforcement technology research is based on the thesis,PI to railway girder as the research object,disease causes,carrying capacity of local small component and local small component of the old and new concrete interface bond strength shear test as the main content,study of bridge structure strengthening.The research contents of this paper are as follows:(1)The diseases of the simply supported girders with π-shaped section of the defective old railway Bridges in some railway lines covered and administered in northwest Gansu Province were investigated;The field investigation and bridge inspection data are summarized,and the two major diseases of concrete carbonation and steel corrosion are analyzed from the aspects of disease mechanism,typical disease characteristics and influencing factors.The steel locator is used to determine the thick Ness of the protective layer of the old bridge,and the steel corrosion behavior is measured by the steel corrosion tester.The field test data show that the thick Ness of the protective layer and the alternately wet and dry environment will accelerate the corrosion of steel bars.(2)According to the current bridge inspection code,check and analyze the bearing reserve capacity of the inner deck of the simple supported girder with π-shaped section of the old railway bridge under dead load,medium-live load and heavy load under normal state and disease state.Based on the finite element numerical analysis of the interface stress state of the decks after deterioration,the safe maintenance limit for the maintenance of the decks with simply supported girder with π-shaped section is proposed.(3)The static loading method of laboratory test was adopted to co MPare the repair effect of the interface between the planting bars and non-planting bars under different concrete grades,different planting bars number,different planting bars specifications and different planting bars ratio.The shear capacity of the repaired interface after the reinforcement was taken as the evaluation index to judge the repair effect of the interface.Based on the test data,a formula for calculating the shear strength of the bonding surface between the old and new concrete of standard specimens is proposed.The accuracy of laboratory test was verified by finite element numerical simulation,and the cause of test deviation was found.(4)Discusses the repair method of inner bridge deck of flawed old railway bridgeπ-shaped section simply supported beam.Combined with the reinforcement and repair characteristics of old railway bridge,the finite element modeling method is used to analyze the stress condition of π-shaped section simply supported beam under the condition of no disease,deterioration and repair and after repair.