Clemens JÄGER

The collapse capacity spectrum methodology - a method for quick collapse capacity assessment of stability prone frame structures subjected to earthquake excitation (in German)

Despite the fact that increased research efforts in the last decade have led to a greater understanding of seismic induced global structural collapse, assessment of seismic collapse is still a challenging and in general computer-demanding task. In particular in an early stage of the design process, the benefits of a detailed determination of the collapse capacity are relatively small compared to the required computational efforts. Thus, it is desirable to have simplified procedures available for a simple and fast to apply but sufficiently accurate assessment of the seismic collapse capacity.

In this thesis such a simplified methodology is proposed aiming at prediction of the seismic collapse capacity of planar moment-resisting frame structures with enelastic non-degrading component behavior, which are vulnerable to the destabilizing effect of gravity loads.

The methodology is based on the transformation of the multi-degree-of-freedom system into an equivalent single-degree-of-freedom system. Its parameters are derived from global pushover curves with and without consideration of gravity loads. Subsequently, the collapse capacity is assessed using so-called collapse capacity spectra. In the spectra the non-dimensional median collapse capacity of a single-degree-of-freedom system is presented as a function ot the elastic structural period and the negative post-yield stiffness. In this thesis these spectra are derived from extensive time history analysis and subsequent applicatioon on nonlinear regression analyses. Consideration of the transformation coefficient yields to the assessment of the collapse capacity of the equivalent single-degree-of-freedom system, which is assumed to be a reasonable estimate of the actual median collapse capacity. Since the essential part of the methodology are collapse capacity spectra, the methodology is referred to as "collapse capacity spectra methodology".

The proposed collapse assessment methodology is applied and tested on a large number of planar moment-resisting frame structures. Moreover, its limitations are discussed.


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