engleski

The effect of mass on the behavior of concrete columns under earthquake

Relatively numerous experimental studies of concrete columns by shaking table have been performed. Increasing a mass at a top of a column increases the inertia forces in it under earthquake, but also reduces the free oscillation periods of the column. So far, the authors of this paper are not familiar of any conducted research regarding this matter by using a shaking table. The results of experimental research of concrete columns with different mass at their top by using a shaking table are presented and discussed. Three equal 1:4 scaled concrete columns with mass of 1, 2 and 3 t at their top were tested. The tested columns were exposed to repeated horizontal base accelerations of artificially formed accelerogram. Each column was tested by a set of artificial accelerograms, with successive increase of accelerations in each applied excitation until structural collapse or loss of stability. Characteristic horizontal displacements and accelerations of the structure were measured, as well as strains in concrete and reinforcement. It was concluded that the size of the mass has great effect on the behavior and limit bearing capacity of the columns, however this effect is not linear. Namely, column with mass of 1 t at the top collapsed at the agmax= 4, 0 ms-2, and column with mass of 3 t at the top collapsed at agmax= 2, 5 ms-2. The numerical model for static and dynamic analysis of planar concrete structures is briefly presented, and then verified on the performed experimental tests. It was concluded that the experimental and numerical results are in good agreement, and that the presented numerical model can be useful in seismic analysis of practical concrete structures.

mass ; concrete column ; shake-table ; earthquake

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