Research On The Load Test Method Of Changchun Gongping Road Birdge Cross Yitong River

Changchun gongping road bridge is a variable cross-section continuous concretebox-beam bridge. The continuous box-beam bridge combines the characteristics ofbox-section and continuous beam, which has advantages of better cross-section torsionalrigidity, reasonable moment distribution of the nagative moment reinforcement at thefulcrum and the sagging moment at the mid-span, flexible style and possibility of usingadvanced construction method, etc. So this kind of bridge is applied wider and wider. Theflexible structure style makes this kind of bridge have a place in the urban landscape bridges.As the extensin of service period, some diseases occur. So some further researches areneeded in the design, construction and detection method of this kind of bridge.To the new-built bridges, structure detection can gain the first-hand data of the bridgeservice state,which can provide reasonable measures for the structure design and the advanceof construction methods. For the existing bridges, structure detection can make clear thebridge existing states, fully excavate the bridge bearing capacity, provide reasonablemeasures for the usage of the bridges and provide the corresponding solutions for the bridgemaintenance and reinforcement. Thus, the research of the detection method is an importantaspect of bridge engineering.At present, the detection methods include three categories: load test, nondestructivedetection and visual inspection. Related data show that load test methods are the mostaccurate. The load tests include static-load tests and dynamical-load tests. The static-loadtesting is to apply the testing load on certain locations of the bridge, test the static responsesof the certain cross-sections under testing load and then evaluate the bridge service statesbased on the static responses. The dynamical load testing is to apply certain motivations onthe the bridge structure to arouse bridge vibration, and then collect the dynamic time historyresponses at certain locations, use experimental modal analysis to obtain the dynamicparameters from the dynamic time history responses, and valuate the bridge service statesbased on the dynamic parameters. So using the test methods to evaluate the bridge servicestates can be less affected by human factors, has high accuracy, and even can find tehdiseases in the hidden parts of the structure. Nowadays, the static and dynamic load test theoretical system of the continuousbox-beam bridges, especially those of special shapes, has not been established. So it’s verymeaningful to conduct the researches on the bridge static and dynamic load tests.Based on the Changchun Gongping Road bridge cross Yitong River, this thesisconducts the work as follows:1. Based on the grillage simulation and the finite element principle, it concludes thegeneral process of building continuous box girder model with variable section by means ofgrillage simulation. According to the characteristics of the Changchun Gongping Roadbridge cross Yitong River, based on the different reduced forms of the arc transition sections,three kinds of grillage simulation theoretical analysis models are separately built. Based onthese three models, the static responses and the dynamic parameters are separately calculatedand compared. Based on the comparative analysis results, it presents the methods of buildingthe arc-transition-section theoretical models of this kind of Yitong River bridges, whichprovides the theoretical support for building the theoretical analysis models of this kind ofbridge.2. By consulting literatures, it concludes the general process of static load tests. Thestatic load test plans are made for the Changchun Gongping Road bridge cross Yitong River,based on which the static load tests are conducted and the deflection and the strain data atcertain cross-sections are tested under different static load conditions. Then based on thesemeasured static responses, the service states are evaluated. Practice shows that the generalprocess concluded by this thesis and the static load test plans can be applied to the staticload tests of the Changchun Gongping Road bridge cross Yitong River. The static load testsof this thesis is applicable to evaluate the bridge service states.3. It divides the assignment of bridge dynamic load tests, and identify the contents ofeach part of work, then form the general process of dynamic load tests. It states the datapreprocessing technology of the random dynamic response signals, and presents the dynamicparameter detection method of combining random decrement technique and ERA method.Based on the theoretical analysis, the dynamic load test plans are made for the ChangchunGongping Road bridge cross Yitong River, and the dynamic load tests are conducted. The random signal preprocessing technology and the dynamic parameter detection methods ofthis thesis can analyze the structure dynamic parameters from the collected dynamicresponses, which proves the feasibility and adaptability.