scholarly journals Role of Higher-“Mode” Pushover Analyses in Seismic Analysis of Buildings

2005 ◽  
Vol 21 (4) ◽  
pp. 1027-1041 ◽  
Author(s):  
Rakesh K. Goel ◽  
Anil K. Chopra
Keyword(s):  
Seismic Analysis ◽  
Plastic Hinge ◽  
Pushover Analysis ◽  
Moment Resisting Frame ◽  
Frame Buildings ◽  
Moment Resisting ◽  
Pushover Curve ◽  
Fema 356 ◽  
Direction Opposite

The role of higher-“mode” pushover analyses in seismic analysis of buildings is examined in this paper. It is demonstrated that the higher-“mode” pushover curves reveal plastic hinge mechanisms that are not detected by the first-“mode” or other FEMA-356 force distributions, but these purely local mechanisms are not likely to develop during realistic ground motions in an otherwise regular building without a soft and/or weak story. Furthermore, the conditions necessary for “reversal” of a higher-“mode” pushover curve are examined. It is shown that “reversal” in a higher-“mode” pushover curve occurs after formation of a mechanism if the resultant force above the bottom of the mechanism is in the direction that moves the roof in a direction opposite to that prior to formation of the mechanism. Such “reversal” can occur only in higher-“mode” pushover analyses but not in the pushover analyses for the first-“mode” or other FEMA-356 force distributions. However, the “reversal” in higher-“mode” pushover curves was found to be very rare in several recent investigations that examined behavior of many moment-resisting frame buildings. Included are guidelines for implementing the Modal Pushover Analysis for buildings that display “reversal” in a higher-“mode” pushover curve.

Evaluation of the seismic level of protection afforded to steel moment resisting frame structures designed for different design philosophies

1999 ◽  
Vol 26 (1) ◽  
pp. 35-54 ◽  
Author(s):  
Aiman Biddah ◽  
Arthur C Heidebrecht
Keyword(s):  
Collapse Mechanism ◽  
Steel Moment Resisting Frames ◽  
Design Philosophy ◽  
Moment Resisting Frame ◽  
Panel Zone ◽  
Statistical Measures ◽  
Frame Buildings ◽  
Moment Resisting ◽  
Steel Moment Resisting Frame ◽  
Recent Earthquakes

Steel moment resisting frames have been considered as excellent systems for resisting seismic loads. However, after recent earthquakes (e.g., Northridge, California, in 1994 and Kobe, Japan, in 1995) the confidence in this structural system was reduced as a result of various types of damage that moment resisting steel frames suffered. This paper presents the results of the evaluation of seismic level of protection afforded to steel moment resisting frame buildings designed in accordance with the National Building Code of Canada. Six- and 10-storey office buildings located in a region of intermediate seismic hazard are designed in accordance with the current Canadian code provisions. Three different design philosophies are considered, namely strong column - weak beam (SCWB), weak column - strong beam (WCSB), and strong column - weak panel zone (SCWP). The performance of these frames is evaluated dynamically by subjecting an inelastic model to an ensemble of 12 actual strong ground motion records. The model takes into account both connection flexibility and panel zone shear deformation. The results are presented in terms of response parameters determined from static pushover analyses, as well as statistical measures of the maximum response parameters determined from the inelastic dynamic analyses. The computed performance of the frames is evaluated in order to assess both the overall level of protection of the frames and the preferred design philosophy. It is concluded that a well-designed and well-detailed ductile moment resisting frame designed using either the SCWB or SCWP design philosophy can withstand ground motions of twice the design level with very little likelihood of collapse, whereas a frame designed using the WCSB approach is ill-conditioned and may develop a collapse mechanism at an excitation level well below twice the design level.Key words: seismic, ductile, steel, frame buildings, performance, design, ductility, damage, inelastic, dynamic.

Pushover Analysis of Base Isolated RC Frame Buildings With Masonry Infills

2019 ◽  
Vol 10 (2) ◽  
pp. 18-31
Author(s):  
Radhikesh Prasad Nanda ◽  
Subhrasmita Majumder
Keyword(s):  
Base Isolation ◽  
Plastic Hinge ◽  
Pushover Analysis ◽  
Base Shear ◽  
Infilled Frame ◽  
Masonry Infills ◽  
Time Period ◽  
Frame Buildings ◽  
Story Drift ◽  
Rc Frame Buildings

In the present article, the performance of base-isolated infilled frames is studied analytically. The seismic performances of four RC buildings, namely RC bare frame without isolator, RC bare frame with isolator, RC infilled frame without isolator, and RC infilled frame with isolator are analysed. The results show a decrease in base shear value and increase in time period due to base isolated buildings, while these parameters are reversely affected due to infills. The decrease in story drift for the base isolated buildings is in phase while considering infill. Also, it can be inferred that plastic hinge formation is greatly affected by the introduction of masonry infill. Hence, relying on base isolation without considering infills may underestimate the seismic performance.

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