An evaluation ofP-Δ amplification factors in multistorey steel moment resisting frames

1999 ◽  
Vol 26 (5) ◽  
pp. 535-548 ◽  
Author(s):  
R Tremblay ◽  
B Côté ◽  
P Léger
Keyword(s):  
Amplification Factor ◽  
Ground Motions ◽  
Beam Model ◽  
Steel Moment Resisting Frames ◽  
Moment Resisting Frame ◽  
Dynamic Analyses ◽  
Moment Resisting ◽  
Shear Beam ◽  
Nonlinear Dynamic Analyses ◽  
Shear Beam Model

Three different amplification factors that have been proposed to account for P-Δ effects in the seismic design of multistorey building structures are described and compared. Nonlinear dynamic analyses of a typical 20-storey steel moment resisting frame are carried out under earthquake ground motions typical of eastern and western Canada to evaluate the gravity load effects and to assess the effectiveness of each type of amplification factor in accounting for these effects. All three approaches maintain the ductility demand within the level computed without P-Δ effects, but lateral deformations are generally larger than those obtained neglecting the gravity loads. Nonlinear dynamic analyses are also performed on a shear-beam (stick) model of the same building to examine the possibility of using such simple models for studying the dynamic stability of buildings subjected to ground motions. The shear-beam model does not predict adequately the seismic behaviour of steel moment resisting frames for which P-Δ effects are significant.Key words: ductility, earthquake, ground motion, lateral deformation, moment resisting frame, P-Δ effects, push-over analysis, seismic, shear-beam model, stability coefficient, amplification factor.

scholarly journals Evaluation of Modified Fish-Bone Model for Estimating Seismic Demands of Irregular MRF Structures

2018 ◽  
Author(s):  
Amin Haghighat ◽  
Ashkan Sharifi
Keyword(s):  
Ground Motions ◽  
Fish Bone ◽  
Seismic Demands ◽  
Error Measure ◽  
Ductility Demand ◽  
Earthquake Records ◽  
Moment Resisting Frame ◽  
Different Types ◽  
Story Drift ◽  
Moment Resisting

This paper evaluates the accuracy of the Modified Fish-Bone (MFB) model for estimating the maximum inter-story drift ratio of irregular moment resisting frame (MRF) structures. To make this model applicable to irregular MRF structures, some modifications are made to the MFB formula. In order to evaluate the accuracy of the MFB model, several irregular frames with different types of irregularities are considered when subjected to different ground motions with different intensities. A local and a global error measure are defined and they are calculated for different frame models subjected to different earthquake records. The effects of different irregularities, ductility demand and frame height on the accuracy of the MFB model are investigated. Based on the results obtained from this evaluation, two simple and effective approaches are suggested to improve the MFB models.

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.

scholarly journals Comparison of Scaling Ground Motions Using Arithmetic with Logarithm Values for Spectral Matching Procedure

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Rui Zhang ◽  
Dong-sheng Wang ◽  
Xiao-yu Chen ◽  
Hong-nan Li
Keyword(s):  
Ground Motions ◽  
Time History ◽  
Response Spectra ◽  
Time History Analysis ◽  
Spectral Matching ◽  
Moment Resisting Frame ◽  
History Analysis ◽  
Moment Resisting ◽  
Structural Responses ◽  
Structural Time

In recent studies, spectral matching is the most commonly proposed method for selecting earthquake records for time-history analysis of structures. However, until now, there have been no serious investigations of the effects of coordinate values on the scaling of ground motions. This paper investigated the influence of using arithmetic and logarithmic values of response spectra in spectral matching procedures (i.e., ASM and LSM methods) on the results of nonlinear structural time-history analysis. Steel moment resisting frame structures of the 3-, 9-, and 20-stories, which represent low-, medium-, and high-rise buildings, respectively, were used as examples. Structural benchmark responses were determined by calculating the arithmetic mean and median of peak interstory drift ratio (PIDR) demands based on the three record sets developed by the American SAC Steel Project. The three record sets represent seismic hazard levels with 50%, 10%, and 2% probabilities exceeded in 50 years, and their average acceleration spectra were also taken as the target spectrum. Moreover, another 40 record components for selection were scaled both by ASM and LSM methods. The seven components whose spectra were best compatible with the target spectra were selected for the structural time-history analysis. The scale factors obtained by the LSM method are nearly larger than that of the ASM method, and their ranking and selection of records are different. The estimation accuracies of structural mean (median) responses by both methods can be controlled within an engineering acceptable range (±20%), but the LSM method may cause larger structural responses than the ASM method. The LSM method has a better capacity for reducing the variability of structural responses than the ASM method, and this advantage is more significant for longer-period structures (e.g., 20-story structure) with more severe nonlinear responses.

Comparative Study of the Inelastic Seismic Demand of Eastern and Western Canadian Sites

2001 ◽  
Vol 17 (2) ◽  
pp. 333-358 ◽  
Author(s):  
Robert Tremblay ◽  
Gail M. Atkinson
Keyword(s):  
Current Practice ◽  
Ground Motions ◽  
Seismic Demand ◽  
Uniform Hazard Spectra ◽  
Damage Potential ◽  
Single Degree Of Freedom ◽  
Dynamic Analyses ◽  
Damage Law ◽  
Nonlinear Dynamic Analyses ◽  
R Factors

The damage potential of earthquake ground motions compatible with site-specific 2% in 50 year uniform hazard spectra is compared at two North American sites in areas of moderate seismic hazard: Montreal, in the east, and Vancouver, along the west coast. For Vancouver, crustal, subcrustal and Cascadia subduction ground motion earthquake ensembles are considered. Nonlinear dynamic analyses of bi-linear single-degree-of-freedom oscillators exhibiting various ductility levels and damage laws were performed to determine R factors required to prevent structural collapse for each site and each system. Then, inelastic response parameters were computed for the general design case, wherein a prescribed R factor is used for a given system irrespective of tectonic region or structural period. The results show that the R factors vary with the ductility level, the damage law, the structural period, and the tectonic region. Neglecting the latter two dependencies in design, as is current practice, may lead to significant discrepancies in the level of protection achieved for different structures in different regions.

A twin shear beam model for double chord RHS joints

1986 ◽  
Vol 23 (1) ◽  
pp. 59-67
Author(s):  
H.S. Mitri ◽  
R.M. Korol ◽  
F.A. Mirza
Keyword(s):  
Beam Model ◽  
Shear Beam ◽  
Shear Beam Model
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