Research On Static And Dynamic Testing Method Of Continuous Latticed Beam Bridges

Latticed beams are composited force-bearing structures, which are widely applied intohighway subgrade retaining engineering and deep excavation retaining engineering. Latticedbeam bridges use the latticed beams into the main structure of bridges, which are spatial highdegree statically indeterminate structures from the aspect of force bearing.Latticed beam bridges include the following characteristics:(1) Saving material so as to reduce the dead-weight of the bridge main structure.(2) The structure style is variable, such as diamond, square,arch,etc. It makes the bridgeappearance more beautiful, which enables a certain application of latticed beam bridges intothe urban landscape.(3) The intuitive of the latticed beam bridges makes the bridge construction easy toconduct.Though the latticed beam bridges are used in the bridge engineering to a certain degree,the application is just started and there are not so much experience obtained in the design,construction and the maintenance and management in service, so it needs further study.Therefore, it’s meaningful to conduct the research on the detection method of this kind ofbridges,which can be shown as follows:①Test the new-built bridges and obtain thefirst-hand test data, so as to make clear the the force bearing state of the bridge structure,correctly master the static and dynamic characteristics and provide support for theimprovement of the bridge design concepts and construction methods.②Detect the bridgein service to know the characteristics of the bridge damage and then deeply analyze thecause of the damage; master the degradation trace of the static and dynamic characteristics,in order to provide decision-making alternatives for the bridge maintenance and management.③Explore the detection method for this kind of bridge and collect the basic data forforming the systematic detection method for the latticed beam bridges.Nowadays, the detection methods include three categories: load test, nondestructivedetection and visual inspection. Visual inspection is based on the visual observation of theinspectors, and use some simple tools (steel rule,etc.) to check the exterior damage.Nondestructive detection is using the nondestructive testing instruments to detect the bridge damage and material properties,etc. The load tests include static load test and the dynamicload test, which is to obtain the mechanics responses at certain position of the bridge bymeans of applying load to the bridge structure, and then analyze the static and dynamiccharacteristics. Then evaluate the bridge service conditions according to the measured data.By comparing these three detection methods, it’s considered that load testing is using themechanics characters to evaluate the bridge state, which is less affected by the environmentwith more accurate results.At present, the application of the latticed beam bridges has just begun, it’s necessary toconduct the detection in the design, construction and maintenance, and management. Loadtest can accurately evaluate the bridge state, so conducting research on static and dynamictesting method of continuous latticed beam bridges is very meaningful.Based on the7-span continuous reinforced concrete latticed beam bridge, this thesisconducts the following work:1. After deeply analyzing the mechanical behavior of the latticed beam bridge, discussthe general process of building the finite element theoretical calculation model of this kind ofbridge, based on the principle of the finite element method. What’s more, it builds thetheoretical models of latticed beam bridges separatively by using beam element and solidelement, and then compare the calculating precision of the two models.2. Based on the theoretical calculating models, the control sections of the7-spancontinuous latticed beam bridge are decided, and the testing load conditions are madeclear.Based on the concept of test efficiency, the load location and the force degree of everytest condition is ensured by means of pilot calculation. Plan the static load testing process ofthe latticed beam bridge, conduct the bridge static load testing, and detect the static-loadresponse of certain section of the bridge. At last, based on the measured static-load responses,evaluate the bridge service conditions.3. According to the theoretical analysis of the latticed beam bridges’ dynamiccharacteristics, the dynamic-load testing method of the7-span continuous latticed beambridge is made up. Exert the ambient excitation on the bridge and test the time historyresponse curves of each dynamic testing location under the ambient excitation.By combining the empirical mode decomposition and the random decrement technique, analyze the threedynamic parameters of frequency, vibration mode and damping. Evaluate the servicecondition based on the tested dynamic parameters and calculating data.