Evaluation For Durability And Safety Of Railway Concrete Bridge In Arid Region

Combined with the technical problems of safety evaluation of the railway RCbridge in northwest arid region, the material and structure performance change featureand rule of the railway existing bridge in arid region were researched, and thereasonable evaluation methods for safety and durability of railway RC bridge were putforward. It is very significant to ensure the safety of railway RC bridge and thesustainable development of railway operation.The concrete strength testing works of northwest railway RC bridge were carriedout according to Xining-Geermu Railway, Baotou-Lanzhou Railway, Diesel DaleRailway Line and Lan-Yu Railway Line. The concrete strength tests showed that, by theimpact of the dry weather, the concrete strengths of the long-age bridge in arid regionexisted great errors with the conversion strength of the criterion, even misadjusted.Considering the influence of environment on intensity evaluation, and the existingproblems of high strength concrete testing, the long-age concrete blocks are made in thesame condition, the strength nondestructive testing and compressive strength test ofconcrete block are made in the lab. The concrete strength detection formulas of reboundmethod and ultrasonic-rebound method in arid region were proposed. The new methodsof concrete strength assessment in arid region based on stress wave and stress-waverebound were proposed, these improved the strength test accuracy, and can be used tohigh strength concrete test.The carbonation phenomenon of concrete of bridge in arid region have significantdifferent characteristics with other region bridge, through the surveys of reinforcedconcrete protective layer thickness, depth of carbonation and reinforcement corrosion of the northwest railway bridges in arid region, the carbonation regular of protectiveconcrete and reinforcement corrosion characteristics of railway bridge in arid regionwere revealed, and the deterioration characteristic of mixed chloride sail concrete wasanalyzed, the design requirements of the railway bridge in arid region were proposed,and were verified by real bridge.With extension of the service period and implementation of the strategy ofOverload and speed up of the railways in our country, the applicability and conditionassessment to large number of gravity pier system is a heavy and lasting work. ByComparisons the testing data of vibration test of railway piers of simple-beam, theapplicability and main point of test method of pier modal parameter was analyzed.According to the structure characteristics of railway bridges of simple beam, based onthe finite-element analysis and real bridge test, the simplified calculation model ofdynamic analysis of simple-beam bridges was proposed. Respect to the problem ofparametric sensitivity of railway piers condition assessment, and combined withtheoretical analysis, the degradation evaluation index of gravity pier system based onthe integrity parameters was proposed.It is a technical difficult problem to test the existing stress in bridge pier of railwayon structure bearing capacity assessment. The pre-stress state of long-age bridge affectthe bridge maintain or disuse decision. To the existing pre-stressed decision ofthin-walled box pier as the background, based on the grooving method finite-elementanalysis, through the research of changing regularity of concrete working stress bycondition changed of load, groove spacing, groove long, cutting depth, the calculationparameters of groove spacing, cutting depth,etc which stress release needed of thepre-stressed box pier were proposed. Combined with the test of existing pre-stress ofthin-walled box piers and vibration test of railway bridges, the key technical problemsof pre-stress assessment and the modification of bridge were solved in practicalapplication.The railway bridge, line, vehicles, etc. factors affect the driving safety, with therailway traffic speed up and the railway bridge styles become more and more, therailway driving safety judgment bases are very difficult selected from test works. To theRC arch bridge of arid region as the background, through the finite-element analysis and the test of wheel/rail force before and after the bridge reinforced, the influence ofstructure dynamic performance and driving safety parameters with the structure statuschanged were analyzed. For looking for the dynamic index of the arch bridge safetyjudgment, combined with the bridge reinforcement, the site tests of the derailmentcoefficient and rate of wheel load reduction change and bridge frequency, amplitude,acceleration indicator before and after bridge reinforced have been done. The testsresults show that the wheel/rail force change before and after the bridge reinforcementhave some relevance with the bridge dynamic indicator change, the equal-substitutebeam method which analyzed the RC arch bridge driving safety limits were proposed, itmade up for the shortage of driving safety limits of the dynamic judgment in TestSpecification of Railway Bridge.The sidewalk system is an important part of railway RC bridge, its safety becomemore and more serious with the train speed gradually increase. To the on-siteinvestigation of disease of sidewalk system of bridges of Bao-Zhong railway, throughstructure analysis, and the vibration test of bridge on site and the sidewalk system fullscale model test in lab, the capacity of sidewalk system were obtained. Combined withthe metallographic analysis of fracture of the U bolt and the fatigue experiment ofsidewalk system indoor, the fatigue life of the U bolt was analyzed. The defects of staticstrength calculation theory of sidewalk system and the fatigue damage characteristics ofsidewalk system were pointed out, the reinforcement method of existing bridgesidewalk system was proposed and the validity of the reinforced sidewalk system wasverified by experiment.