scholarly journals Assessment of Progressive Collapse Capacity of Earthquake-Resistant Steel Moment Frames Using Pushdown Analysis

2014 ◽  
Vol 8 (1) ◽  
pp. 324-336 ◽  
Author(s):  
Massimiliano Ferraioli ◽  
Alberto Maria Avossa ◽  
Alberto Mandara
Keyword(s):  
Nonlinear Dynamic ◽  
Progressive Collapse ◽  
Accurate Estimation ◽  
Resistant Steel ◽  
Moment Frames ◽  
Earthquake Resistant ◽  
Dynamic Analyses ◽  
Column Removal ◽  
Nonlinear Dynamic Analyses ◽  
Pushdown Analysis

The study investigates the progressive collapse resisting capacity of earthquake-resistant steel moment-resisting frames subjected to column failure. The aim is to investigate whether these structures are able to resist progressive collapse after column removal, that may represent a situation where an extreme event may cause a critical column to suddenly lose its load bearing capacity. Since the response to this abnormal loading condition is most likely to be dynamic and nonlinear, both nonlinear static and nonlinear dynamic analyses are carried out. The vertical pushover analysis (also called pushdown) is applied with two different procedures. The first one is the traditional procedure generally accepted in current guidelines that increases the load incrementally to a specified level after column has been removed. The second procedure tries to reproduce the timing of progressive collapse and, for this reason, gravity loads are applied to the undamaged structure before column removal. The load-displacement relationships obtained from pushdown analyses are compared with the results of incremental nonlinear dynamic analyses. The effect of various design variables, such as number of stories, number of bays, level of seismic design load, is investigated. The results are eventually used to evaluate the dynamic amplification factor to be applied in pushdown analysis for a more accurate estimation of the collapse resistance.

Structural Simplicity vs. Robustness in the Progressive Collapse Risk Assessment of a 13-Story RC Framed Structure

2017 ◽  
Vol 21 ◽  
pp. 78-85 ◽  
Author(s):  
Teodora S. Besoiu ◽  
Adrian M. Ioani
Keyword(s):  
Cross Sections ◽  
Nonlinear Dynamic ◽  
Numerical Models ◽  
Progressive Collapse ◽  
Computer Software ◽  
Maximum Load ◽  
Seismic Code ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses ◽  
Structural Simplicity

In the present study, the effect of the structural simplicity on the progressive collapse resistance of a 13-story RC framed building is assessed. The existing structure from Brăila (a zone with high seismic risk from Romania) designed in 1972 according to the former seismic code P13-70, was re-designed in accordance to the provisions of the current seismic code P100-1/2013. The original building consists of beams and columns with different cross-sections along the height of the structure. To achieve the objective of this study, a new model with constant cross-sections was designed according to the current seismic and structural concrete codes. Following the provisions of the GSA (2003) Guidelines, nonlinear dynamic analyses are performed using the Applied Element Method incorporated in the ELS® computer software. It was shown that, under the standard GSA loading (DL+0.25LL) the both two numerical models of the 13-story building are not expected to fail when a first-story corner column is suddenly removed. To estimate the ultimate load-bearing capacity of the structural models, a series of nineteen nonlinear dynamic analyses are carried out. The robustness analyses indicate that, the model with different cross-sections can sustain a maximum load 16% larger than the model with constant cross-sections along its height.

Numerical Investigations on the Seismic Response of Masonry Building Aggregates

2010 ◽  
Vol 133-134 ◽  
pp. 715-720 ◽  
Author(s):  
Ilaria Senaldi ◽  
Guido Magenes ◽  
Andrea Penna
Keyword(s):  
Seismic Response ◽  
Nonlinear Dynamic ◽  
Masonry Building ◽  
Structural Units ◽  
Numerical Investigations ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses ◽  
Building Aggregates

The work focuses on the analysis of the seismic response of masonry building aggregates for a better understanding of the vulnerability of single structural units and of their behaviour within the aggregates. Idealized representative models are developed based on the typical characteristics of the row conglomeration typology. The seismic response of the models is evaluated and discussed by means of nonlinear dynamic analyses.

Implications of cumulated seismic damage on the seismic performance of unreinforced masonry buildings

2014 ◽  
Vol 47 (2) ◽  
pp. 157-170 ◽  
Author(s):  
Amaryllis Mouyiannou ◽  
Andrea Penna ◽  
Maria Rota ◽  
Francesco Graziotti ◽  
Guido Magenes
Keyword(s):  
Nonlinear Dynamic ◽  
Fragility Curves ◽  
Seismic Damage ◽  
Unreinforced Masonry ◽  
Masonry Building ◽  
Masonry Buildings ◽  
Seismic Capacity ◽  
Building Stock ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses

The seismic capacity of a structure is a function of the characteristics of the system as well as of its state, which is mainly affected by previous damage and deterioration. The cumulative damage from repeated shocks (for example during a seismic sequence or due to multiple events affecting an unrepaired building stock) affects the vulnerability of masonry buildings for subsequent events. This paper proposes an analytical methodology for the derivation of state-dependent fragility curves, taking into account cumulated seismic damage, whilst neglecting possible ageing effects. The methodology is based on nonlinear dynamic analyses of an equivalent single degree of freedom system, properly calibrated to reproduce the static and dynamic behaviour of the structure. An application of the proposed methodology to an unreinforced masonry case study building is also presented. The effect of cumulated damage on the seismic response of this prototype masonry building is further studied by means of nonlinear dynamic analyses with the accelerograms recorded during a real earthquake sequence that occurred in Canterbury (New Zealand) between 2010 and 2012.

INFLUENCE OF ADDED VISCOUS DAMPERS ON THE PROBABILISTIC SEISMIC PERFORMANCE EVALUATION OF RC FRAMES

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Luca Landi ◽  
Cristina Vorabbi ◽  
Pier Paolo Diotallevi
Keyword(s):  
Nonlinear Dynamic ◽  
Ground Motions ◽  
Frame Structures ◽  
Rc Frame ◽  
Viscous Dampers ◽  
Fluid Viscous Dampers ◽  
Hazard Curve ◽  
Dynamic Analyses ◽  
Nonlinear Dynamic Analyses ◽  
Rc Frame Structures

This paper deals with the parameters which influence the probability of reaching the near collapse limit state of RC frame structures equipped with nonlinear fluid viscous dampers. The study can be divided into two steps. The first aims to assess how the median and the dispersion of seismic demand can vary in the RC frame structures with and without dampers, considering a wide set of ground motions. The second step evaluates the expression in closed form, given by 2000 SAC/FEMA method, to assess the annual probability of failure of RC structures. This probability has been estimated considering a wide set of ground motions and different methods to approximate the hazard curve. The evaluations have been made on the basis of the results of a large number of nonlinear dynamic analyses; in particular, 180 nonlinear dynamic analyses have been made for the case studies with and without dampers. In conclusion, it has been noticed that the probabilistic assessment depends on the number of records considered and that the simplified formula provided by the 2000 SAC-FEMA method is strongly sensitive to the variation of the hazard curve and the dispersion.

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