Abstract
In the previous paper (Part 1) dynamic collapse mechanisms and energy absorbing capacities of framed structures subjected to catastrophic earthquakes were discussed theoretically. In this paper, the elastic and inelastic responses of steel framed structures to earthquake ground motions were investigated numerically, and the results of numerical examples were compared with theoretical predictions described in Part 1. Since the comparison demonstrated good agreement, it may be concluded that the theoretical predictions proposed in Part 1 is reasonable. The significant aspects of this study may be summarized as follows : (1) It is required to consider correlations between story shear forces in determining seismic loads for aseismic design. Therefore, it is efficient and convenient to express the distribution of seismic loads in terms of the second joint moments of story shear forces. (2) If the purpose of aseismic design is to maintain all the structural members in elastic region, the beams should be a little weaker than the columns belonging to the same beam-column assemblage. (3) The energy absorbing capacity predicted in Part 1 gives a lower bound of the energy that a framed structure subjected to earthquake excitations can absorb until collapse. (4) The energy absorbing capacity of a framed structure is strongly affected by the elastic limit strength ratio β of the beams to the columns belonging to the same beam-column assemblage. (5) If a total weight of structural steel is constant regardless of β, the energy absorbing capacity reaches the maximum when β is around 0.6. And the maximum value becomes approximately equal to the product of the square root of the number of stories and the energy that a framed structure with β=1 can absorb until collapse.
