Seismic Mechanism Of RC Split Column And Performance-based Seismic Design Of RC Frame With Split Columns

In RC tall building structures, the sections of frame columns are larger and their shear-span ratios are smaller due to the limitation of axial-compression ratio of the columns, so that some short even ultra short columns exist at the bottom floors of the structures, which may generate brittle shear failure to result in damage even collapse of the structures because of their poor ductility during earthquakes. Technology of reinforced concrete split column is to split a rectangular short column to 2 or 4 elemental columns with same section and reinforced individually by partitions, which may enlarge one time of the shear-span ratio of the short column and transfer the short column to"long"columns directly.In this thesis, based on the previous systematic research, seismic mechanism of RC split columns is numerically analyzed by using the nonlinear finite element method, which may develop and complete the theory of RC split columns. The main research work and achievements are described as follows:(1) Based on the experimental data, the solid finite element models are established considering the bond-slip between concrete and bars as well as the contact between partitions and elemental columns. The numerical experiment under cyclic actions is carried out. The calculated results are much coincided with the experimental results.(2) The regularity of contact state, maximum contact stress, maximum normal stress and shear stress of elemental columns at the yielding, ultimate and damaged points as well as the crack distribution at the damaged point is summarized.(3) The seismic behavior, including the failure pattern, bearing capacity, deformation ability and ductility of a concrete frame with integral long columns is numerically analyzed by using the static elasto-plastic finite element method, and compared with the corresponding frame with split columns. The results indicate that the seismic behavior of split column is equivalent to that of the integral long column which is as 1.7 times high as the split column. Performance-based design procedure of frame with split columns is recommended.