Dynamic Response And Analytical Study Of RC Spatial Frame Structures With Specially Shaped Columns With The Column Removal

Progressive collapse of structures occurs when local structure or substructure is damaged due to unexpected events, and the local failure leads to other parts of the structure, eventually resulting in the collapse of the entire structure. RC frame structures with specially shaped columns are widely used in residential buildings. But the limb of specially shaped columns is weaker than the rectangular columns, and its beam-column joints are prone to be damaged. Therefore progressive collapse more likely occurs to RC spatial frame structures with specially shaped columns. This paper focuses on RC frame with specially shaped columns, and collapse test of RC frame model with specially shaped columns was carried out to study on progressive collapse resistance.In order to study the dynamic response of the RC frame with specially shaped columns with the column removal, collapse test of a(3×2)-bay and 2-storey RC frame model with specially shaped columns was carried out. Two main scenarios of column removal have been considered: an angle column and a short edge column. And the experimental results show that the maximum angle of the beam which is connected with the removed column respectively are 1.45×10-4rad and 1.46×10-4rad, which are both lesser than the criteria of collapse 0.105 rad. So the experimental analysis predicts that the frame did not collapse when an angle column or a short edge column was instantaneously removed, which shows that the RC frame with specially shaped columns have good collapse resistant performance.Then the RC frame model with specially shaped columns was analyzed by using the finite element software ANSYS/LS-DYNA. Nonlinear dynamic alternative load path method was applied for the progressive collapse analysis, and the scenarios of column removal were consistent with the test. The displacement response and the reinforcement strain during the collapse test of the frame were comparison with the calculation, and the comparison shows that experimental values are in good agreement with the calculated values. So in the follow-up studies, LS-DYNA can be used to study progressive collapse resistance of the RC frame model with specially shaped columns. And the crack patterns of the beams which are connected with the removed column during the collapse of the frame were analyzed based on software. And the results show that stress values did not exceed the axial tensile strength or axial compressive strength of concrete, which means that neither cracking nor crushing will happen to concrete. In the collapse test no minor cracks were found, which are consistent with finite element analysis results.On this basis, more scenarios of column removal were considered: an inner column and two adjacent frame columns together. The results show that even if two adjacent frame columns were suddenly removed together, the remaining frame will not collapse. But the dynamic effects of the remaining frame is more significant.