Research On Evaluation Approach Of Lateral Distribution And In-sevice Condition For Reinforced Concrete Bridge

Highway bridge is an important part of traffic infrastructure, which plays an importantrole to raise the operation efficiency of transportation system, improve people’s life quality,and ensure the stable development of economy. According to the ministry of transportationauthority statistics, small and medium span bridges in China accounted for more than90%.In the small and medium span bridges, reinforced concrete beam bridge is the most widelyused structural form.As traffic continued to increase, and the occurrence of vehicles overloading, thefunctions of these in-service bridges decrease, fatigue damage phenomenon is serious. Thedamage rate of transverse connection is higher for prefabricated reinforced concrete beambridge, which results in the mutation of bridge load transverse distribution and "single board(beam) force" phenomenon. The traditional calculation method of transverse distribution isvery limited, which is inefficient in the evaluation of transverse connection damage problemfor reinforced concrete bridge. Therefore, it is important to carry out the calculation methodof transverse distribution for the reinforced concrete beam bridge, the damage assessment oftransverse connection and overall bridge performance assessment to guarantee the safeoperation of birdge structure. Combined with the national high technology research anddevelopment program (863Program) and Jilin Provincial Communications Departmentproject, the specific research works are carried out as follows:1. Based on traditional theory of elastic support continuous beam method, a novelapproach is put forward by combining monospar finite element calculation with elasticsupport continuous beam method to obtain the transverse distribution. The supportingstiffness of transverse model can be calculated by the acquisition of deflection and twistangle of longitudinal structure. The proposed method is applied to typical bridges includingsimply supported hollow slab bridge, simply supported T-beam bridge, simply supported curved beam bridge, simply supported skew bridge and also continuous beam bridge withvariable cross section, the applicability of the method is verified. Comparative analysis withtraditional hinged plate method, orthotropic plate method, the rigid cross beam method, thespatial finite element method, and the rigidity conversion method, the calculation precisionand effectiveness of the proposed method are analyzed.2. Based on the theory of modal analysis, the calculation method of transverse loaddistribution based on modal parameters of bridge structure is presented. Selecting of simplysupported T beam bridge and the simply supported hollow slab bridge as the research object,the calculation results of modal parameter method, the traditional simplified analysismethod and finite element static analysis method are compared and analyzed in detail, andthe applicability and accuracy of the proposed method in simply supported T beam bridgeand the simply supported hollow slab bridge in load transverse distribution calculation arevalidated. Moreover, the effects of diagram, skew angle, and girder spacing on loaddistribution of T-beam bridge are demonstrated through the modal properties-basedcalculation method for lateral distribution.3. Considering that the simply supported slab bridge in the service process is prone tohinge joints damage and girder damage condition. Condition evaluation for damges areconducted based on the modal parameters-based method for calculation of transversedistribution. For damage identification of hinge joint, damage position can be identifiedthrough the cross phenomenon of the transverse distribution influence line in the damagedhinge joint. According to the damage identification of girder, damage position can beidentified by offset phenomena through the lateral distribution influence line in the mainbeam. Aiming at the hinge joint damage and girder damage state identification, appropriatestructural damage identification parameters were selected, different fuzzy membershipfunctions were determined, fuzzy evaluation system for the hinge joints damage and girderdamage system were constructed.4. In the evaluation of bridge durability in existing methods, artificial subjective factorsbecome the main reasons affecting the effectiveness of bridge durability evaluation. Toeliminate the interference of subjective factors in the process of bridge condition assessment, a kind of bridge upperstructure durability evaluation method based on fuzzy C meansclustering optimized by particle swarm optimization was put forward. Evaluation indexsystem of bridge structure durability was formed by use of field measured data.10typicalbridges were selected as clustering samples for bridge durability condition assessment.Xie-Beni effective analysis was conducted after standardization of sample data in order todetermine the optimal number of samples clusters. Combining with bridge condition index,cluster centers and membership matrix were also obtained. By calculating the membershipdegree of measured data with hierarchical clustering center value, bridge condition can beassessed. Filed structure is selected to verify the effectiveness of the proposed method.