Seismic stability and the force reduction factor of code-designed one-storey asymmetric structures

1999 ◽  
Vol 28 (7) ◽  
pp. 785-803 ◽  
Author(s):  
Mario De Stefano ◽  
Avigdor Rutenberg
Keyword(s):  
Reduction Factor ◽  
Seismic Stability ◽  
Asymmetric Structures ◽  
Force Reduction Factor ◽  
Force Reduction

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 shear demand of ductile cantilever walls: a Canadian code perspective

1994 ◽  
Vol 21 (3) ◽  
pp. 363-376 ◽  
Author(s):  
André Filiatrault ◽  
Danilo D'Aronco ◽  
René Tinawi
Keyword(s):  
Time History ◽  
Shear Walls ◽  
Analytical Investigation ◽  
Reduction Factor ◽  
Seismic Shear ◽  
Force Reduction Factor ◽  
Force Reduction ◽  
Shear Failures ◽  
Nonlinear Time History ◽  
Shear Demand

During severe earthquakes, ductile flexural walls are expected to exhibit inelastic flexural behaviour while other brittle deformation mechanisms, such as shear, should remain elastic. The philosophy of the Canadian seismic provisions for flexural walls is based on the assumption that the force reduction factor is applicable to both flexure and shear. If the bending moments are limited because of the flexural strength of a wall, then the shear forces are considered to be limited by the same ratio. Recent case studies have not confirmed this philosophy. Brittle shear failures in walls are still possible even if their shear strengths are established by the Canadian standards. This paper presents an analytical investigation on the shear demand of ductile flexural walls designed for three different seismic zones in Canada. For each zone, an ensemble of code compatible historical earthquake ground motions is identified. The shear demand of each structure, under each earthquake record, is obtained by nonlinear time-history dynamic analyses. In 77% of the cases, the computed dynamic shear demand is higher than the current code shear strength. To address this issue, a force modification factor for shear, different from the one for flexure, is suggested for the Canadian code. Key words: earthquake, seismic response, shear walls.

scholarly journals Force Reduction Factor R for Shear Dominated Low-Rise Brick Masonry Structures

2018 ◽  
Vol 2 (3) ◽  
pp. 14-29
Author(s):  
N. Ahmad ◽  
Q. Ali ◽  
M. Javed ◽  
◽  
◽  
...  
Keyword(s):  
Reduction Factor ◽  
Brick Masonry ◽  
Masonry Structures ◽  
Force Reduction Factor ◽  
Force Reduction

Caltrans' New Seismic Design Criteria for Bridges

2000 ◽  
Vol 16 (1) ◽  
pp. 285-307 ◽  
Author(s):  
Mark Yashinsky ◽  
Thomas Ostrom
Keyword(s):  
Seismic Design ◽  
Nonlinear Behavior ◽  
Previous Method ◽  
Reduction Factor ◽  
Design Criteria ◽  
Structural Elements ◽  
Linear Elastic ◽  
Displacement Capacity ◽  
Force Reduction Factor ◽  
Force Reduction

Caltrans' Seismic Design Criteria (SDC) has been adopted as the minimum seismic standard for ordinary bridges on California's highways. The SDC is a compilation of new and existing seismic criteria that had been previously documented in a variety of Caltrans documents. The SDC extends the capacity design philosophy introduced in the 1980 Caltrans Bridge Design Specifications. The most significant departure from the previous procedure is that ductile members are now designed by comparing the displacement demand to the displacement capacity. The demands are generated by a linear elastic analysis, and the capacities are determined from a curvature analysis that incorporates the nonlinear behavior of the structural elements. The demand/capacity methodology supplants the previous method based on reducing the elastic dynamic forces by a force reduction factor. In this paper, the significant features of Caltrans' SDC are described.

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.

Prediction of force reduction factor (R) of prefabricated industrial buildings using neural networks

2007 ◽  
Vol 27 (2) ◽  
pp. 117-134 ◽  
Author(s):  
M. Hakan Arslan ◽  
Murat Ceylan ◽  
Yaspr M. Kaltakci ◽  
Yuksel Ozbay ◽  
Fatma Gulten Gulay
Keyword(s):  
Neural Networks ◽  
Reduction Factor ◽  
Industrial Buildings ◽  
Force Reduction Factor ◽  
Force Reduction

scholarly journals Analytical Analysis of Seismic Behavior of Cold-Formed Steel Frames with Strap Brace and Sheathings Plates

2014 ◽  
Vol 2014 ◽  
pp. 1-22 ◽  
Author(s):  
M. Gerami ◽  
M. Lotfi
Keyword(s):  
Steel Frames ◽  
Shear Wall ◽  
Reduction Factor ◽  
Response Modification Factor ◽  
Resistance Reduction ◽  
Wall Panels ◽  
Force Reduction Factor ◽  
Modification Factor ◽  
Cold Formed Steel ◽  
Force Reduction

Cold-formed steel frames (CFS) are popular all over the world. In this study, we have investigated 112 frames with different bracing arrangements and different dimensional ratios with different thicknesses of sheathing plates under cyclic and monotonic loading using Finite Element Nonlinear Analysis. We also evaluated seismic parameters including resistance reduction factor, ductility, and force reduction factor due to ductility for all specimens. On the other hand, we calculated the seismic response modification factor for these systems. The maximum modification factor among shear wall panels with sheathing plates related to GWB (gypsum wall board) specimen with thickness of 15 mm was 5.14; among bracing specimens in bilateral bracing mode related to B sample was 3.14. The maximum amount of resistance among the specimens with bilateral (2-side) bracing systems belongs to the specimen C (2-side double X-bracing) with the dimension ratio of 2 (4.8 m × 2.4 m) and resistance of 305.60 kN and also among the shear wall panels with sheathing plates, it belongs to DFP (douglas fir plywood) with a thickness of 20 mm and resistance of 371.34 kN.

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