Static-dynamic Load Test And Method Of Damage Indentification For Fish-belly Continuous Box Girder Bridge With Four Spans

The most obvious feature of continuous bridge is using the positive bending momentlocated at the support to decrease the negative moment located in the middle of the span. Theresult is that the force of a bridge sections have to burden is uniform, and the span can bebuilt larger. The box girder bridge has bigger bending stiffness and torsional stiffness, all ofthis make the bridge has a better integral when it burdens the force. The web of ifsh-bellycontinuous box Girder Bridge is curve line makes the bridge more beautiful. Using thetechnology of cast-in-place concrete, the bridge structure can suit for the change of the roadline. For all the reason above, the ifsh-belly continuous box girder bridge can suit for thechange of the road line well, and makes the bridge more beautiful. This kind bridge is widelybuilt in our country.While the structure of this kind bridge is complicated, and the result is that its forcefeature is also complicated. You can never do enough precise measurements, design for that.On the other hand, measurements and design can not take the place of test. It is necessary todo the static, dynamic load test to measure its mechanical properties. Through tests, you canget the primary data for the design.As the service period extend, this kind bridge also has some damage. The most eiffcientway for damaged bridge is do the bridge inspection. Make the reasonable maintain and ifxplan according to the result of the bridge inspection can tap the bearing capacity of thebridge. The static, dynamic load test is the most accurate measure among the bridgeinspection at present. So it has much sense to do the research of the static, dynamic load test.Taking advantage of dynamic parameters to judge the structure is widely used byresearchers for it has the following advantages: have high speed, do not create additionaldamage, and can ifnd the damage at the hiding places. As the ifsh-belly continuous boxgirder bridge has its own structure feature, it needs more research to decide that if the currentmethods can use into this kind bridge.Above all, the research in this paper about static, dynamic load test and method of damage identiifcation for ifsh-belly continuous box Girder Bridge has much meaning intheory and practical application.Based on a ifsh-belly continuous box girder bridge with four spans, the research I do asfollows:1.Make sure the general process for the static load test for the continuous box girderbridge，and do some research about the key technology. Build a theoretical calculate modelfor ifsh-belly continuous PC box Girder Bridge with four spans based on the basic principleof beam-grid method. Do the static load test for this bridge，measuring the static response ofkey section. Estimate its static operational performance according to the static response.2.Make sure the general process for the dynamic load test for the continuous box girderbridge，and do some research about how to set the sample rate and how to recognizedynamic parameter. Draw up how to set the dynamic measure point according to the result ofSystem calculation. We exerted excitation into bridge structure by ambient excitation andtest time-history response of all the measure points. Employing the method of modiifed ERAto recognize dynamic parameter. Estimate the bridge’s dynamic operational performanceaccording to the dynamic parameter.3.Based on dynamic parameter (frequency, vibration mode) and its derivativeindication (curvature mode shape, modal curvature difference), exploring the sensitive of thefish-belly box girder bridge to damage. At last, decided that using modal curvaturedifference to relfect damage of the structure. According to the damage feature of ifsh-bellycontinuous box Girder Bridge，I come up with a new method including two steps. Use neuralnetworks to train the cell which has damage, and recognize its damage level.