The Detection Of Four-span Prestressed Concrete Continuous Box Girder Bridge From0th To4th Pier Of The Road And Rail Overpass In Baicheng Jinhut

The continuous beam bridge reduces the middle span positive bending moment by thenegative bending moment at the bearing points, which makes the structure stress more evenand enlarges the structure span. The continuous beam bridge belongs to staticallyindeterminate structure, whose advantages are better structural stiffness, smallertransformation, fewer expansion joints and more steady and comfortable drive. Theprestressed structures prestress the concrete by the high tensile reinforcement, which notonly exerts the characteristics of the high tensile reinforcement, but improves the crackresistance. The prestress reduces the transformation in the service period, puts off the displayof the cracks, and improves the bridge crack resistance. Then we can say the prestressimproves the usability of the continuous beam bridge and improves the span of the bridges.The advantages of the thin-wall box section:(1) combination of the bearing structureand the power transmission structure, makes all parts participate into the stress bearing, andimproves the utilization efficiency of the section, which has good economic effects;(2) hightorsional stiffness of the thin-wall box section makes the load lateral distribution more evenand improves the integrity of the structure;(3) the top tray and baseboard have majorconcrete areas which can effectively resist the positive and the negative moment and issuitable to the continuous bridges which have both positive and negative moments;(4) themechanical property of the section determines that this kind of structure is suitable to themodern construction method, such as cantilever construction method and hanging basketconstruction method. Because the prestressed concrete box bridge combines the advantagesof prestressed structures, continuous beam bridges and the box section, this kind of bridge iswidely applied.The detection meaning of this kind of prestressed concrete continuous girder bridge isas follows:(1) As the extension of the service period, this kind of bridge may encounter diseaseswhich degenerates the bridge use function. The most effective means is to detect the disease bridges and based on the data obtained to accurately assess the bridge usability, and then topresent reasonable usage, maintenance, and reinforcement measures.(2) The continuous beam bridge is statically indeterminate structure, under the effectsof the temperature load and bridge foundation deflection, the bridges can produce additionalinternal force. Under the external load, the thin-wall box section may have transformation oflongitudinal bending, transverse bending, torsion and distortion. The prestressed concretecontinuous box bridges combine the advantages of prestressed structures, continuous beambridges and the box sections. At the same time, this kind of bridge increases the complexityof the structure mechanical behavior. Considering the complexity of the structuralmechanical behavior, it is impossible to make clear all the structural mechanical behaviors,which surely makes differences between the design and practical projects. The bridgedetection can be regarded as a model test of the practical structure to a certain degree, so thebridge detection can provide the basic data and technical supports for the bridge structuredesign method.At present, the prestressed concrete continuous box bridge detection is not systematic oreffective. Considering the importance of this kind of bridge detection, the work conductedby this paper is necessary.This paper is based on the four-span prestressed concrete continuous box girder bridgefrom0th to4th pier of the road and rail overpass in Baicheng Jinhui, and the work conductedis as follows:1. Conduct appearance inspection to the practical project. Compare the testing methodof the concrete strength and discuss the basic step of the ultrasonic rebound synthetic methodand the calculation method of the concrete strength. Test the main beam concrete strength ofthe practical project.2. Build the theoretical analysis model of the four-span prestressed concrete continuousbeam bridge, and based on the model conduct the theoretical analysis. Based on the analysisresults, make sure of a series of key technical issues, such as the testing conditions and themonitoring point arrangement in the static load tests, and make up the static load testingprogram. Conduct the field static load tests to the bridge and test the static responses of the specific part of the bridge under the testing load conditions. Based on the static response data,assess the bridge stiffness and strength, and then analyze the bearing capacity of the bridge.3. Based on the eigenvalue analysis of the four-span continuous box bridge, make sureof the key problems in the dynamic load tests such as the shock excitation， the monitoringpoint arrangement and the sample frequency and make up the dynamic load testing program.According to the testing program, test the dynamic time-histories responses. Object to thecharacteristics of the dynamic time-histories response, present the test modal analysismethod of combining the Random Decrement Technique and STD method, and by thismethod obtain the dynamic parameter testing values of the bridge. Based on the dynamicparameter testing values, assess the dynamic usability of the bridge.