Period-dependent seismic force reduction factors for short-period structures

1991 ◽  
Vol 18 (4) ◽  
pp. 568-574 ◽  
Author(s):  
W. K. Tso ◽  
N. Naumoski
Keyword(s):  
Reduction Factor ◽  
Structural Systems ◽  
High Ductility ◽  
Base Shear ◽  
Ductility Demand ◽  
Seismic Design Code ◽  
Short Period ◽  
Seismic Force ◽  
Force Reduction ◽  
Reduction Factors

The seismic force reduction factors proposed in the seismic provisions of the National Building Code of Canada 1990 (NBCC 1990) are examined using ground motion records from two recent Canadian earthquakes. The displacement ductility demands are analyzed for structural systems with different ductility capacity. It is found that the NBCC 1990 force reduction factors, which are period independent, lead to a very high ductility demand for short-period structural systems. To avoid this, two types of period-dependent force reduction factors for short-period structures are investigated. The results show that the linearly varying period-dependent reduction factor represents a viable means to resolve the high ductility problems associated with short-period structural systems. Key words: earthquake, seismic, design, code, response, spectra, ductility, reduction factor, base shear.

An Evaluation of Two-Level Seismic Design Procedure

1993 ◽  
Vol 9 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Chia-Ming Uang
Keyword(s):  
Structural Damage ◽  
Limit State ◽  
Design Procedure ◽  
Reduction Factor ◽  
Performance Criteria ◽  
Ultimate Limit State ◽  
Seismic Codes ◽  
Seismic Force ◽  
Force Reduction Factor ◽  
Force Reduction

The two-level design philosophy is recognized by modern seismic codes. When this philosophy is implemented in the code, the intensities of the two design earthquakes, the structural performance criteria, explicit versus implicit design approach, and the effectiveness to achieve the performance criteria vary considerably from one code to the other. For the ultimate limit state, the UBC was compared with seismic codes of Canada, Japan, and Eurocode. It was found that a trend to deviate from the UBC approach of using a single seismic force reduction factor (i.e., Rw) is apparent. Instead, an approach using a compound force reduction factor which considers the contribution of structural ductility and structural overstrength is preferred. For the serviceability limit state, a comparison of the level of design earthquakes and performance criteria of the UBC, Tri-Services Manual, and the Japanese code indicates that the UBC produces the most flexible structure, and that UBC does not control structural damage. It is suggested that the UBC adopts an explicit serviceability design procedure.

Development of Seismic Force Reduction and Displacement Amplification Factors for Autoclaved Aerated Concrete Structures

2006 ◽  
Vol 22 (1) ◽  
pp. 267-286 ◽  
Author(s):  
Jorge L. Varela ◽  
Jennifer E. Tanner ◽  
Richard E. Klingner
Keyword(s):  
Reduction Factor ◽  
Test Results ◽  
Lateral Loads ◽  
Autoclaved Aerated Concrete ◽  
Laboratory Test Results ◽  
Seismic Force ◽  
Force Reduction Factor ◽  
Aerated Concrete ◽  
Hysteretic Characteristics ◽  
Force Reduction

This paper addresses the development and application of a rational procedure to select the seismic force reduction factor ( R) and the displacement amplification factor ( Cd) for the design of autoclaved aerated concrete (AAC) structures. The values of R and Cd are proposed based on a combination of laboratory test results and numerical simulation. The test results are obtained from 14 AAC shear-wall specimens tested under simulated gravity and quasi-static reversed cyclic lateral loads. Analytical responses are predicted using nonlinear analysis models whose hysteretic characteristics are based on the experimentally observed responses. Using an iterative procedure, typical AAC structures are designed using successively larger trial values of the factor, R, until the structure's response (either ductility or drift) exceeds the experimentally determined capacity. A lower fractile of those critical values, modified for probable structural overstrength, is taken as a reasonable value of 3 for R. Using an analogous procedure, a reasonable value of Cd is determined as 3. These values will undoubtedly be refined based on field experience, just as they have been for other structural systems.

scholarly journals Further comments on seismic design loads for bridges

1981 ◽  
Vol 14 (1) ◽  
pp. 3-11
Author(s):  
J. B. Berrill ◽  
M. J. N. Priestley ◽  
R. Peek
Keyword(s):  
New Zealand ◽  
Response Spectra ◽  
Reduction Factor ◽  
Base Shear ◽  
Attenuation Model ◽  
Design Spectra ◽  
Model Code ◽  
Force Reduction Factor ◽  
Background Material ◽  
Force Reduction

This paper provides background material to the loadings section
of the model code recently published by the Society's Discussion Group
on Bridge Design, and presents a preliminary re-evaluation of the design spectra given in the proposed code. The basis for the proposed zoning scheme, in which the present uniform Zone B is replaced by a transition zone, is discussed. Arguments are given underlying the return period coefficients, and the force reduction factor used in generating the inelastic response spectra of the code. It is likely that the design spectra and the values of the other coefficients determining base shear forces will need to be revised as further research results become available; however, the form of the base shear expression, and the loadings section
as a whole, should remain unchanged. Re-evaluated spectra suggest that
the seismic coefficient values given in the proposed code may be too large by about 25 percent in Zone A, and too low by as much as 40 percent in
 Zone C. While the reassessed values should be more reliable than the original ones, they are based on a Japanese attenuation model, which has
not yet been calibrated against New Zealand data. Further research is required to establish an appropriate attenuation model for New Zealand;
 to avoid undue proliferation of design loadings it is preferable to defer revision of the various coefficients in the proposed code until such a
model is available. Until this is done, the proposed spectra should be viewed with caution, particularly in Zone C.

Seismic analysis of short-period structures subjected to the 1988 Saguenay earthquake

1992 ◽  
Vol 19 (3) ◽  
pp. 510-520 ◽  
Author(s):  
Pierre Léger ◽  
Angelo Romano
Keyword(s):  
Seismic Design ◽  
Seismic Analysis ◽  
Strong Motion ◽  
Response Spectra ◽  
Base Shear ◽  
Ductility Demand ◽  
Short Period ◽  
Modification Factor ◽  
Energy Dissipation Capacity ◽  
Design Earthquake

This paper presents elastic and inelastic response spectra of strong motion accelerograms recorded during the 1988 Saguenay earthquake. Comparisons are made with the National Building Code of Canada (NBC) 1990 lateral forces requirements for the seismic resistant design of short-period structures. The use of a period-dependent force modification factor is proposed to take advantage of the energy dissipation capacity of short-period structures on a more rational basis. The seismic response of a typical low-rise steel building designed according to the NBC 1990 and CAN3-S16.1-M89 is then investigated. It is shown that to obtain a realistic picture of the ductility demand of low-rise buildings, the structural overstrength, that is, the supplied strength in excess of the seismic design base shear, should be explicitly considered in the design process. Key words: seismic design, earthquake, low-rise structures, code.

Probabilistic Study on Accidental Torsion of Low-Rise Buildings

2004 ◽  
Vol 20 (1) ◽  
pp. 25-41 ◽  
Author(s):  
Jaime De-la-Colina ◽  
Cristina Almeida
Keyword(s):  
Ground Motions ◽  
Center Of Mass ◽  
Random Variable ◽  
Lateral Force ◽  
Reduction Factor ◽  
Ductility Demand ◽  
Accidental Eccentricity ◽  
Force Reduction Factor ◽  
Probabilistic Study ◽  
Force Reduction

A probabilistic study on accidental torsion is presented. Multistory shear systems, representative of low-rise buildings and subjected to bidirectional earthquake ground motions are considered. Ductility demands of lateral resisting elements (LREs) due to uncertainties on (1) center-of-mass locations, (2) LRE stiffness, and (3) LRE yield forces were studied. Building code recommendations on accidental torsion as well as the effects of both eccentricity and lateral-force reduction factor are assessed. Results indicate that considering one random variable in the accidental torsion problem can lead to larger ductility-demand probabilities of exceedance than using two or more variables. Individual effects of each one of the variables considered are not superimposed when all variables take place at the same time. For systems designed for torsion, ductility demands of LREs decreases for increasing eccentricities. Increments of yield forces and decrements of probabilities of exceedance due to the use of increasing values of factor β associated with the accidental eccentricity are presented.

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