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.

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.

Nonbuilding Structures Seismic Design Code Developments

2000 ◽  
Vol 16 (1) ◽  
pp. 127-140
Author(s):  
Harold O. Sprague ◽  
Nicholas A. Legatos
Keyword(s):  
Seismic Performance ◽  
Seismic Design ◽  
Nonlinear Behavior ◽  
Seismic Energy ◽  
Building Design ◽  
Structural Elements ◽  
Performance Requirements ◽  
Seismic Design Code ◽  
Wide Range ◽  
Structural Engineers

The building code development process has traditionally given little effort to developing the seismic design process of nonbuilding structures. This has created some unique problems and challenges for the structural engineers that design these types of structures. The intended seismic performance requirements for “building” design are based on life safety and collapse prevention. Structural elements in buildings are allowed to yield as a method of seismic energy dissipation. The seismic performance of nonbuilding structures varies depending on the specific type of nonbuilding structure. Nonlinear behavior in some nonbuilding structures is unacceptable while other nonbuilding structures may be allowed to yield during an earthquake. Nonbuilding structures comprise a vast myriad of structures constructed of all types of materials, with markedly different dynamic characteristics, and with a wide range of performance requirements. This paper discusses the development of codes, design practices, and future of the seismic design criteria for nonbuilding structures.

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.

Theoretical and Applied Insights on Pistons Buckling According to DNV Regulation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Nicholas Fantuzzi ◽  
Fabio Borgia
Keyword(s):  
Nonlinear Behavior ◽  
Experimental Investigations ◽  
Structural Elements ◽  
Linear Elastic ◽  
Geometrical Imperfections ◽  
Slender Beams ◽  
Hydraulic Cylinders ◽  
Uniform Cross Section ◽  
Engineering Practices ◽  
Numerical Approaches

Pistons are fundamental structural elements in any engineering practices such as mechanical, civil, aerospace, and offshore engineering. Their strength strongly depends on buckling load, and such information is a major requirement in the design process. Euler's linear buckling equation is the most common and most used model in design. It is well suited for linear elastic members without geometrical imperfections and nonlinear behavior. Several analytical and experimental investigations of typical hydraulic cylinders have been carried out through the years but most of the available standards still use a linear approach with many simplifications. Pistons are slender beams with not-uniform cross section, which need a stronger effort than the classical Euler's approach. The present paper aims to discuss limitations of current DNV standards for piston design in offshore technologies when compared to classical numerical approaches and reference results provided by the existing literature.

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
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