Analysis On Pancake Collapse Impact Of Reinforced Concrete Frame Structures

Pancake collapse of the structures under strong earthquake or terrorist attacks is acommon failure mode. At present, only a few scholars have carried out exploratory researchon impact response between upper and lower structure. Research objects of those exploratoryresearches are generally a single component or scale model. Free fall impact, the mostunfavorable form of pancake collapse, is studied in this thesis. The effects of the free fallheight, the mass of upper structure, materials of lower structure and soil effects are studied onthe example of the real multi-story RC frame structure and an approximate estimation methodfor the effective impact force of RC frame structure is proposed. The main work is as follows:(1) On the basis of the well numerical simulation of the existing tests, by expanding thevalue range of main test parameters, the change law of the maximum impact force underexperimental conditions is obtained. The difference between experimental conditions andengineering conditions are studied and the reason for differences in the change law of themaximum impact force under two conditions is found out.(2) The free fall impact of the real multi-story RC frame structure is studied. The changelaw of the maximum impact force and its plane distribution, the impact impulse, relative tothe free fall height and mass of upper structure, are obtained.(3) The influence of soil effect on the impact response of RC frame structure is alsostudied in this thesis. It can be seen that: relative to the situation in which the soil effects isn’ttaken into account,(a) the maximum impact force is relatively7.41%to20.95%smaller;(b)the impact impulse in the same time range is slightly smaller.(4) An approximate estimation model for the effective impact force of RC framestructure under two situations (considering soil effects or not) is proposed. The quantitativeanalysis for the parameter in the approximation estimation model is carried out andestimation formulas of corresponding to different percentages are obtained. It can be seenthat: when the free fall height and the mass of upper structure are the same, the value of (considering soil effects) is0.84,0.85,0.85times that of (not considering soil effects),corresponding to different percentages (70%,60%,50%).