Research On Seismic Performance Of Exposed-type Steel Column Bases With Wedge Devices

In the field of normal steel structure and light-weight steel structure, the exposed-type steel column base is widely used. The restoring force characteristics of conventional exposed-type column bases are slip-type under low cyclic load, and the energy dissipation ability is not fully performed. To resolve the above problem, a non-slip-type steel column base with wedge spring damping devices is studied. The new type column base shows significantly improved seismic performance. Sponsored by the National Natural Science Foundation project "the research on disaster analysis and relief measures of Wenchuan earthquake"(50848008) and the National High Technology Research and Development Program "the key technology and application of the recycled concrete and new steel structural building materials"(2009AA032304), the mechanical behavior of the new steel column base is studied by theoretical analysis, cyclic loading test and numerical simulation. Also, the dynamic properties of steel frame with the new column base are studied. The main research achievements are summarized as follows:With the deformation influences of bolt, steel column plate, concrete base, washer and nut taken into account, formulas of deformation and rotational stiffness of exposed-type steel column bases are derived. The working mechanism and mechanical properties of the column base with wedge devices and the conventional column base are studied. The results show that the restoring force model of the exposed-type column base with wedge devices is non-slip-type, and the restoring force model of the common exposed-type steel column base is slip-type. The new column bases with wedge devices and common column bases are tested separately under low cyclic load, with the influence of different bolt numbers and column axial force taken into account. Thus, the restoring force characteristics of these column bases are deduced. Through experimental study, the derived formulas and restoring force models in the thesis are proved to be practical and effective. For column base with wedge devices, the gap between base plate and foundation produced by deformation of column base bolt is eliminated by use of the wedge spring devices, and the column base is fastened all the time. Compared with the ordinary column base, the new column base shows improved seismic performance, slower rigidity degeneration, improved ductility and energy dissipation capacity. The three-dimensional finite element model is established for numerical simulation, given the influence of material nonlinearity, contact nonlinearity, bolt number and arrangement on the bearing force and seismic performance of column bases. The finite element analysis results agree well with the test results. Hysteretic curve and skeleton curve have the same changing tendency as the test results. The curve is approximately linear before the specimen yield, but after the yield, the curve is obviously nonlinear. The increase of axial force is beneficial to the improvement of the bearing capacity in a certain range, but the capability of energy consumption is also reduced. The joint area has strong constraint on column, which results in the larger experimental value of skeleton curve in plastic zone compared with the finite element analysis. The increase of the bolt number is favorable to the bearing capacity and stiffness of column base.The simplified numerical simulation technology of slip-type column base is presented under low cyclic load, by using Link8unit in ANSYS in series with Link10tension type unit, and then in parallel with Link10pressure type unit to simulate the bolt of column base, and using Link10pressure type unit to simulate the base plate of column base. The simulation technology of non-slip-type column base is also proposed under low cyclic load, by using APDL language and the unidirectional displacement technology of Link8unit to simulate the base plate of column base. By comparison with the test results, the numerical simulation technology on column base presented in the thesis shows a good, practical and reliable effect.The Combin39unit in ANSYS and pressure type Link10unit are arranged in parallel, by using the former to simulate the bolt of column base and the latter to simulate the pedestal base. The characteristics of the constitutive relation of Combin39unit can be defined by inputting force-displacement curve. The numerical simulation technology of slip-type and non-slip-type column base is realized by inputting the different force-displacement curve. The energy consumption characteristics and the dynamic response of frame structure are studied under the seismic excitation. The new type wedge spring damping device can effectively control inter-story displacement of structure, reduce the seismic response of structure, and effectively dissipate the seismic energy. Thus, the structure of the new column bases with wedge spring devices shows an improved seismic performance.In summary, the seismic performance of a new non-slip-type steel column base with wedge spring devices is studied based on the test, theoretical research and finite element analysis. Meanwhile, the theoretical calculation formulas of the conventional slip-type exposed column base and the new non-slip-type exposed column base with wedge spring devices are derived. Then, the numerical simulation technology is also proposed. The work provides a reliable basis for the application of the new non-slip-type exposed column base.