Sub-Structural Modal Flexibility Integration Theory And Experiment Research For Bridge Deck Identification

Steel concrete composite structure is a commo n form of bridge structure, and the research on its structure ident ificat ion is of great significance. In this paper, stat ic load tests, dynamic load test s and substructural modal flexibilit y ident ificat ion were conducted on a laboratory steel concrete composite slab and a real steel-concrete composite structure bridge based on previous research findings. The specific research contents are listed in the following:(1) Two methods to calculate modal flexibilit y were reviewed, although the approaches may appear dist inct, in realit y these two modal flexibilit y calculat ion methods are consistent. By using the characterist ic of mutual transformat ion between two methods, the mass normalized mode shapes can be got. A method ut ilizing the substructural modal test to obtain the glo bal flexibilit y is proposed. The global structural mode shapes can be assembled by putt ing together substructural mass normalized mode shapes, further the global modal flexibilit y can be extracted.(2) Through a numerical test of simply supported reinforced concrete slab and a laboratory steel concrete composite slab test, it is shown that SISO, SIMO and MIMO impact tests can all generate reliable modal flexibilit y coefficients. The proposed integrat ion strategy can est imate the glo bal modal flexibilit y wit hin a few percent of stat ic flexibilit y. The possibilit y of ut ilizing substructur al modal tests to get global modal flexibilit y has been verified by a real bridge test. Meanwhile, the mass normalized mode shapes got by the random vibration test was studied. A numerical test and a laboratory test showed that structural modal flexibilit y can be extracted based on lumped mass matrix assumpt ion, and the tested flexibilit y result is bigger than the actual flexibilit y.(3) Structural damage ident ificat ion based on the modal flexibilit y was researched. First ly, three damage cases were designed to simulate the damage situat ion on real bridge, which are remo val of cross diaphragm, changes of boundar y condit io n, damage of connectors. By comparing modal flexibilit y informat ion before and after structural damage, the damage ident ification of steel concrete composit e slab is easily achieved. Test results show that modal flexibilit y is a good damage index and flexibilit y coefficients are more sensit ive to damage than either frequencies or mode shapes. Secondly, stat ic damage of steel concrete composite slab was made by the stat ic load test, and the damage locat ion and damage degree was successfully ident ified based on modal flexibilit y.(4) Steel concrete composite structure model updat ing method based on Strand7-Mat lab applicat ion programming interface(API) strategy was researched. First ly, three different finite element model of steel concrete composite structure was compared in this paper. The results show that the shell-brick model can well reflect the real stat ic and dynamic performance of composite structures. Then, sensit ivit y analysis for the physical parameters was studied based on the stat ic and dynamic data of the benchmark model, and four parameters was selected for model updating. Finally, the concept of Teughels damage funct ion was introduced to model ident ification. By comparison of test data and finite element analysis results, the st iffness degradat ion distribut ion of the tested slab has been ident ified.