Seismic Induced Global Collapse of Non-deteriorating Frame Structures

Abstract

In a severe seismic event the destabilizing effect of gravity loads, i.e. the P-delta effect, may be the primary trigger for global collapse of quite flexible structures exhibiting large inelastic deformations. This article deals with seismic induced global collapse of multi-story frame structures with non-deteriorating material properties, which are vulnerable to the P-delta effect. In particular, the excitation intensity for P-delta induced structural collapse, which is referred to as collapse capacity, is evaluated. The initial assessment of the structural vulnerability to P-delta effects is based on pushover analyses. More detailed information about the collapse capacity renders Incremental Dynamic Analyses involving a set of recorded ground motions. In a simplified approach equivalent single-degree-of-freedom systems and collapse capacity spectra are utilized to predict the seismic collapse capacity of regular multi-story frame structures.

Seismic collapse capacity of basic inelastic structures vulnerable to the P‐delta effect

“…Note that in a tall long period moment frame structure the inelastic stability coefficient is generally much larger than the elastic one. This can be accounted for with the procedure elaborated in .…”

“…Accordingly, the specification of the following parameters is sufficient for prediction of P-delta-induced structural collapse of SDOF systems with a bilinear backbone curve [16]: Note that in a tall long period moment frame structure the inelastic stability coefficient is generally much larger than the elastic one. This can be accounted for with the procedure elaborated in [21,26].…”

“…On the basis of the results of extensive parametric studies considering the uncertainties of the record‐to‐record variability, nonlinear regression analyses lead to collapse capacity spectra, which represent the collapse capacity as a function of the period and negative post‐yield stiffness ratio. The ultimate objective of this study is to provide collapse capacity spectra for easy to apply and yet sufficient accurate assessment of the dynamic stability of flexible multistory buildings (see, e.g., ).…”

Performance analysis of damaged buildings applying scenario of related non-linear analyses and damage coefficient

“…Applying the energy concept and the Yield Point Spectra Method the structures' damage functions were considered using: the displacement modification factor, yield strength reduction factor, seismic energy response parameter, damage index and equivalent ductility ratio [24]. Possibilities of developing various fracture mechanisms in the moment resisting frame (MRF), both in storey and combined levels, are shown in [31], while in [1] and [2] the collapse mechanism of system fracture are identified on the basis of collapse capacity spectra. Generally, the system's fracture mechanism can develop locally or globally.…”

“…Primenom energetskog koncepta i metode spektra odgovora za nivo granice tečenja (YPS), razmatrane su funkcije oštećenja zgrada preko: faktora modifikacije pomeranja, faktora redukcije nosivosti na granici tečenja, parametra seizmičke energije, indeksa oštećenja, koeficijenta ekvivalentne duktilnosti [24]. Razmatranje mogućnosti razvoja različitih mehanizama loma okvirnih sistema zgrada (MRF) -od spratnog do kombinovanogprikazano je u radu [31], dok je u radovima [1], [2] izvršena identifikacija kolapsnog mehanizma loma sistema na osnovu spektra kapaciteta kolapsa. Generalna podela razvoja mehanizma loma sistema jeste na lokalni i gobalni.…”