Study On The Bridge Bearing Disease Identification Technique Based On The Natural Frequency Change Rate

Bridge bracing is an important part of the bridge structure, although in the bridgeconstruction costs accounted for the proportion of relatively low, but bearing plays animportant role in bridge structure. The load of superstructure is transferred to the stage. at thesame time, to meet the free deformation under the action of the bridge upper structure load,temperature, creep and shrinkage of concrete. It affects the service life and the use safety ofbridges directly,for various reasons of bearing defects,. For this time, the detection methodsof bridge bearing is still relatively primitive, and it mainly rely on the observation of artificialruler which is still remain in the apparent detection stage, and it is relatively less that thetesting study on the actual working performance of bridge bearings after installation. Becauseof the height of the support is small,the location in low light, and the bearing detection is highaltitude operation, which lead to so many difficulty to detect bridge support, and the detectionof abutment support in the breast wall side is more difficult. Now the instruments of bearingtest is very simple and limited, such as only by naked eye observation and ruler, which isdifficult to accurately reflect the actual working state support, and it is useful to identify itsuse through making a qualitative and quantitative analysis of support.Based on the theory of bridge vibration with detection technology has the advantages ofsimple operation, high efficiency, low cost, no need to block traffic without structure damageand other advantages, and can grasp the structure from the global. Bridge bearing as the forcetransmission component connecting bridge girders and piers of the bridge, which is boundaryconditions in the structural analysis, and it has a greater effect on the vibration of the bridge’scontribution. In this paper, it discussed the frequency change rate method for the detection ofbridge bearing disease, which is based on experimental and numerical calculation.Firstly, According to the motion equations of structure analysis establish the structure ofbridge. The bearing can be considered to be part of the whole bridge structure system, and itcan be simplified as a spring connected with the bridge piers. Bearings for vibration onlydepends on the bearing stiffness, and the influence of various diseases of bridge vibrationcharacteristic of the bridge is the result of spring stiffness changes.Secondly, the theoretical analysis in this paper base on16meters of reinforced concretehollow slab beam bridge that the size according to the ratio of1:5.In this experiment threereinforced concrete beams were made, the stiffness of bearing was translated into the contactarea change. By experiment, the use of DHDAS5922vibration acquisition system, thejumping beam method was used to collect the self vibration frequency under the normal bearing arrangement and the bearing stiffness degradation, and discussed the bridge bearingstiffness on the bridge natural frequency effect. Through researching the natural frequencychange rate, and finding that the trend of bridge bearing stiffness effects on naturalfrequencies. through the experiments,it can be found that: the reduced stiffness of supportaffects the natural frequency of the structure, and the natural frequencies of the structure itselfwill decrease with the decrease of bearing stiffness. The bearing stiffness effects on thenatural frequency of the structure with the different of bearing position, and the support thatclosed to both sides of the bridge have more influence on the natural frequency than thesupport of the bridge central. By the multi support common disease, the total variation ofstructure frequency rate is higher than the single support frequency changes occurred diseases,this is because the rate of frequency under each support separate disease occurring is the samemagnitude; so with the increase of diseases bearing number, natural frequencies of thestructure reduce the rate of change. It can diagnose disease degree of disease, disease locationand disease bearing number.In conclusion, the MIDAS FEA finite element software is applied to set up two wholebridge according to the ratio of1:1. The calculation method of the eigenvalue and the adjustedbearings were used to detect the disease state, the hollow slab beam bridge which is16metersand the prestressed concrete continuous girder bridge which main span is52meters weresimulated. The experimental conclusion is extended to the actual size of the bridge model test.Through the study of this paper, it can be concluded that the testing methods of bridgevibration frequency is useful to detect the degree of disease diagnosis, disease location anddisease bearing number.