PRELIMINARY REPORT O N STEEL BUILDING DAM AGE FROM THE DARFIELD EARTHQUAKE OF SEPTEMBER 4, 2010
Author: Michel Bruneau , Myrto Anagnostopoulou , Greg MacRae , Charles Clifton and Alistair Fussell | Size: 1.6 MB | Format:PDF | Quality:Unspecified | Publisher: BULLETIN OF THE NEW ZEALAND SOCIETY FOR EARTHQUAKE ENGINEERING, Vol. 43, No. 4, December 2010 | pages: 9
This paper presents preliminary findings based on the performance of various steel structures during the Darfield earthquake of September 4, 2010, including concentrically braced frames, eccentrically braced frames, steel tanks, and steel houses. With a few exceptions, steel structures performed well during this
earthquake, but much of this is attributed to the fact that seismic demands from the Darfield earthquake were generally lower than considered in their design.
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SEISMIC ANALYSIS OF RETAINING WALLS, BURIED STRUCTURES, EMBANKMENTS, AND INTEGRAL ABUTMENTS
Author: usam Najm, Assistant Professor Suhail Albhaisi, Graduate Research Assistant Hani Nassif, Associate Professor Parham Khoshkbari, Graduate Research Assistant Nenad Gucunski, Professor | Size: 3.1 MB | Format:PDF | Quality:Unspecified | Publisher: Dept. of Civil & Environmental Engineering Center for Advanced Infrastructure & Transportation (CAIT) Rutgers, The State University | Year: 2005 | pages: 160
In 1998, the National Cooperative Highway Research Program (NCHRP) initiated a project to develop a new set of seismic design provisions for highway bridges intended to be compatible with the AASHTO LRFD Specifications (1) . This project, designated 12-49, was conducted by a joint venture of the Applied Technology Council (ATC) and the Multidisciplinary Center for Earthquake Engineering Research (MCEER). This research project was needed to reflect the experience gained during recent damaging earthquakes, as well as the results of research work conducted in the United States, Japan, and other countries over the last decade (2) . Recommended LRFD Guidelines for the Seismic Design of Highway Bridges (3) were based on NCHRP Project 12-49. The purpose of the new NCHRP 12-49 provisions is to provide seismic design guidelines and performance objectives for bridges in order to ensure the safety of the public, and to minimize structural and non-structural damage. In recent years, several major bridges have collapsed and others have sustained significant damage during earthquakes (2) . The NCHRP 12-49 guidelines adopted the MCE (maximum considered earthquake or 2 percent PE on 50 years) as an upper level event for collapseprevention and adopted the EXP (expected) earthquake (50 percent in 75 years) as a lower level event for which the structure essentially remains elastic. These changes in the newly recommended guidelines will have a major impact on seismic design of bridges in the Eastern United States. Several states, including New Jersey, are evaluating the impact of these changes on their local, state, and federal bridges. In addition, soil amplification factors Fa and Fv have increased dramatically for soft soils, especially when subject to small ground motions. These factors are not site-specific to the Eastern United States and were based on soils and earthquake records predominantly in the Western United States (See references 3,4,5, and 7) . These factors may vary for different soils, geographic locations, and ground motions. Among the other major changes in the new NCHRP 12-49 seismic design provisions are updated seismic maps, new response modification factors ®, detailed performance and hazard level criteria, and design incentives when performing “pushover” analysis. These provisions are intended to help bridge owners and state officials with current designs and provide designers more flexibility in the analysis and design.
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A Pseudo-Dynamic Method to Analyze Retaining Wall with Reinforced and Unreinforced Backfill
Author: Saeed Shekarian and Ali Ghanbari | Size: 219 KB | Format:PDF | Quality:Unspecified | Publisher: JSEE: Spring 2008, Vol. 10, No. 1 | Year: 2008 | pages: 7
ABSTRACT: In this article, the problem of determining pseudodynamic pressure and its associated forces on a rigid vertical retaining wall is solved analytically using the horizontal slices method for both reinforced and unreinforced walls. The use of this method in conjunction with the suggested equations and unknowns offers a pseudo-dynamic method that is then compared with the results of an available software. In the proposed method, different seismic accelerations have been modeled at different soil structure heights. Reinforced soil pressure on a retaining wall and the angle of the critical failure wedge are calculated using the new formulation. It is shown that as the horizontal seismic acceleration coefficient increases the angle of the critical failure wedge is reduced and that the maximum extension force can be increased for each layer by using stronger and longer reinforcements. The results of the pseudo-dynamic method show that both vertical and horizontal seismic accelerations are essential coefficients for calculation of the required length and extension force of the reinforcements and that their importance increases as the vertical and horizontal seismic accelerations increase. Also, the location of the application point of the resultant pressure rises as the horizontal
seismic acceleration coefficient increases.
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Author: Robert V. Whitman, Samson Liao Department of Civil Engineering Massachusetts Institute of Technology | Size: 5.3 MB | Format:PDF | Quality:Unspecified | Publisher: DEPARTMENT OF THE ARMY US Army Corps of Engineers | Year: 1985 | pages: 160
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It is generally agreed that the stability of retaining walls exposed to earthquakes is not
a matter for real concern.
In a paper delivered in 1970 at the ASCE Specialty Conference, Professors H. Bolton
Seed and Robert V. Whitman said:
"Few cases of retaining wall movement or collapse
of walls located above the water table have been
reported in the literature on earthquake damage.
(...) it seems likely that the small number of
accounts of retaining wall performance is not
necessarily indicative of the lack of occurrence of
wall movements: this type of damage is not
particularly dramatic compared with other forms of
earthquake damage and thus may often be
considered of minor significance."
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ABSTRACT
In common practice, the seismic design of an embedded retaining wall is carried out using the pseudo-static method. In this approach, constant forces are introduced in a limit equilibrium calculation, and the seismic analysis of a retaining wall is treated similarly to the evaluation of the safety against a collapse mechanism. This paper is aimed to propose a reconsideration of the simple pseudo-static calculation: it shows that the method can be used within the context of the performance-based design to predict the actual seismic performance of the wall, and that concepts employed in the capacity design of structural members can be extended to the design of embedded retaining walls. The paper also points to possible code prescriptions that may provide guidance for the correct application of the pseudo-static method to the design of retaining walls.
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A review of design methods for retaining structures under seismic loadings
Author: C. Visone & F. Santucci de Magistris Structural and Geotechnical Dynamic Lab StreGa, University of Molise, Termoli (CB), Italy | Size: 274 KB | Format:PDF | Quality:Unspecified | Year: 2008 | pages: 14
ABSTRACT: The earth retaining structures frequently represent key elements of ports and harbors, transportation
systems, lifelines and other constructed facilities. Earthquakes might cause permanent deformations of
retaining structures and even failures. In some cases, these deformations originated significant damages with
disastrous physical and economic consequences. For gravity walls, the dynamic earth pressures acting on the
wall can be evaluated by using the Mononobe-Okabe method, while Newmark rigid sliding block scheme is
suitable to predict the displacements after the shaking, as demonstrated by several experimental tests. Instead,
this simplified approach is not very useful for embedded retaining walls for various reasons. Many researchers
are interested to this topic. Advanced numerical analyses, centrifuge modeling, in-situ monitoring of full-scale
model are the main developing research activities on this subject. Here, after a brief review on the fundamental
seismic earth pressures theories, the application of the pseudostatic approach to the analysis of embedded
retaining walls, as prescribed by the European Codes, is highlighted. Finally, some considerations on the certain
limitations of this approach is done and the indications given by the latest Italian Building Codes (D.M
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Assessment of the modes of failure of retaining structures from previous major earthquakes: Caltrans Seismic Design Analysis of Retaining Walls Project
Author: Tadei Shayo Home Institution: UC Davis REU Institution: UCSD (Shake Table) REU Advisor: Prof. Lijuan (Dawn) Cheng, UC Davis Graduate Student Mentor: Erin Mock, UC Davis | Size: 968 KB | Format:PDF | Quality:Unspecified | Year: 2009 | pages: 21
The report herein is part of a larger project; the objective of the larger project is to improve the seismic design guidelines for highway retaining walls. For the large project, two specimens of
full-scale, reinforced concrete gravity retaining walls were constructed according to the current building code of The California Department of Transportation (Caltrans). The specimens will undergo shake table test at NEESinc’s Englekirk Center for Structural Engineering facility. The testing protocols to be used are the 1994 California Northridge (Mw= 6.7) and the 1999 Turkey Izmit/Kocaeli (Mw=7.4) earthquakes. The structural performance of the retaining walls after testing will thus be analyzed and used to make changes to the current design code. For this secondary project, assessment of the modes of failure of retaining walls from previous significant earthquake is done. A discussion is given regarding the correlations between the modes of failure and earthquake characteristics. Finally, recommendations as to which types of
reinforcing techniques are most effective in resisting seismic loads are given.
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SEISMIC ANALYSIS OF RETAINING WALLS WITHIN PLASTICITY FRAMEWORK
Author: T.Kalasin and D. Muir Wood | Size: 310 KB | Format:PDF | Quality:Unspecified | Publisher: The 14 th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China | Year: 2008 | pages: 11
Aseismic design of gravity wall still is a more difficult issue. The reason stems from the complexity of the problem which requires skills in soil mechanics, foundation engineering, soil-structure interaction along with knowledge of structure dynamics. Designing seismic gravity retaining structures deals with both kinematic interaction and inertial interaction but almost seismic building code neglected the soil-structure interaction by using the fixes base analysis of the structure. The gravity walls are a slender tall structure
and it was suggested to be taken into account of dynamic soil-structure interaction analysis because such walls often perform badly when subjected to strong earthquake ground motion. Also the permanent displacement should be evaluated when designing the seismic gravity walls so that the need of the most reliable approach to evaluate a wall’s vibration properties is required. In this paper, the alternative development of computed permanent responses was proposed in order to predict permanent responses of the
seismic wall. The proposed model was constructed within the concept of macro-element modelling the soil, foundation and the seismic earth pressures. The constitutive law for modelling soil and foundation were based on two-surface kinematic hardening with associated flow rule. The development of seismic earth pressures was based on the Mononobe-Okabe method (1929) and the elastic–perfectly plastic method (Muir Wood and Kalasin(2004)) which based on the kinematic hardening by updating of a reference position for the wall. A parametric study is presented and The results are compared with published experimental results.
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