Author: C. O. CIOFLAN, A. MÃRMUREANU, GH. MÃRMUREANU National Institute for Earth Physics, Romania Received January 19, 2009 | Size: 602 KB | Format:PDF | Quality:Unspecified | Year: 2009 | pages: 10
The seismic hazard of Romania has been the object of several studies based on probabilistic or deterministic methods (1). Details of the resulted hazard maps are still a controversial issue that leads to an innovative approach: a combined analysis of the available records and macroseismic information completed with numerical simulations since the strong motion records are rather scarce. The main purpose of this paper is to add new features regarding site effects evaluation and its role in seismic hazard analyses at regional and/or local scale. This study is focusing on nonlinear aspects of seismic ground motion and presents new results related to site effects induced by strong Vrancea intermediate events.
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A FIBER BEAM-COLUMN ELEMENT FOR SEISMIC RESPONSE ANALYSIS OF REINFORCED CONCRETE STRUCTURES
Author: Fabio F. Taucer Research Assistant Enrico Spacone Doctoral Student and Filip C. Filippou Associate Professor Department of Civil Engineering | Size: 2.6 MB | Format:PDF | Quality:Unspecified | Publisher: Report No. UCB/EERC-91/17 Earthquake Engineering Research Center College of Engineering University of California, Berkeley | Year: 1991 | pages: 140
This study proposes a reliable and computationally efficient beam-column finite element model for the analysis of reinforced concrete members under cyclic loading conditions that induce biaxial bending and axial force. The element is discretized into longitudinal steel and concrete fibers such that the section force-deformation relation is derived by integration of the stress-strain relation of the fibers. At present the nonlinear behavior of the element derives entirely from the nonlinear stress-strain relation of the steel and concrete fibers.
The proposed beam-column element is based on the assumption that deformations are small and that plane sections remain plane during the loading history. The formulation of the
element is based on the mixed method: the description of the force distribution within the element by interpolation functions that satisfy equilibrium is the starting point of the
formulation. Based on the concepts of the mixed method it is shown that the selection of flexibility dependent shape functions for the deformation field of the element results in
considerable simplification of the final equations. With this particular selection of deformation shape functions the general mixed method reduces to the special case of the
flexibility method. The mixed method formalism is, nonetheless, very useful in understanding the proposed procedure for the element state determination. A special flexibility based state determination algorithm is proposed for the computation of the stiffness matrix and resisting forces of the beam-column element. The proposed nonlinear algorithm for the element state determination is general and can be used with any nonlinear section force-deformation relation. The procedure involves an element iteration scheme that converges to a state that satisfies the material constitutive relations within the specified tolerance. During the element iterations the equilibrium and the compatibility of the element are always satisfied in a strict sense by the assumed force and deformation interpolation functions. The proposed method proved to be computationally stable and robust, while being able to describe the complex hysteretic behavior of reinforced concrete members, such as strain hardening, "pinching" and softening under cyclic nodal and element loads.
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EVALUATION OF SEISMIC DEFORMATION DEMANDS USING NON- LINEAR PROCEDURES IN MULTISTORY STEEL AND CONCRETE MOMENT FRAMES
Author: Sashi K. Kunnath and Erol Kalkan Department of Civil and Environmental Engineering University of California at Davis | Size: 271 KB | Format:PDF | Quality:Unspecified | Publisher: SET Journal of Earthquake Technology, Paper No. 445, Vol. 41, No. 1, March 2004, pp. 159-181 | Year: 2004 | pages: 23
A key component of performance-based seismic evaluation is the estimation of seismic demands. In FEMA-356 (FEMA, 2000b), which is now recognized as the model for future performance-based seismic codes in the US, these demands are evaluated at the component level in terms of ductility demands or plastic rotations when using non-linear procedures. Since acceptance criteria for various performance objectives are assessed in terms of local component demands, it is essential that a rational basis be established for determining such demands. Of the non-linear procedures advocated in FEMA-356,
pushover procedures are becoming increasingly popular in engineering practice. However, there are still several unresolved issues in identifying appropriate lateral load patterns to be used in a pushover procedure. This paper investigates the correlation between demand estimates for various lateral load patterns used in non-linear static analysis. It also examines the rationale for using component demands over story and system demands. Results reported in the paper are based on a comprehensive set of pushover and non-linear time-history analyses carried out on eight- and twelve-story steel and concrete moment frames. Findings from this study point to inconsistencies in the demands predicted by different
lateral load patterns when using pushover analysis and also highlight some issues in the current understanding of local demand estimates using FEMA-based procedures.
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Nonlinear Soil-Site Effects in Probabilistic Seismic-Hazard Analysis
Author: Paolo Bazzurro and C. Allin Cornell | Size: 250 KB | Format:PDF | Quality:Unspecified | Publisher: Bulletin of the Seismological Society of America, Vol. 94, No. 6, pp. 2110–2123, December 2004 | Year: 2004 | pages: 14
This study presents effective probabilistic procedures for evaluating ground-motion hazard at the free-field surface of a nonlinear soil deposit located at a specific site. Ground motion at the surface, or at any depth of interest within the
soil formation (e.g., at the structure foundation level), is defined here in terms either of a suite of oscillator-frequency-dependent hazard curves for spectral acceleration,
, or of one or more spectral acceleration uniform-hazard spectra, each associated with a given mean return period. It is presumed that similar information is available
for the rock-outcrop input. The effects of uncertainty in soil properties are directly included.
This methodology incorporates the amplification of the local soil deposit into the framework of probabilistic seismic hazard analysis (PSHA). The soil amplification is characterized by a frequency-dependent amplification function, AF( f ), where f is a generic oscillator frequency. AF( f ) is defined as the ratio of to the spectral acceleration at the bedrock level, . The estimates of the statistics of the ampli-fication function are obtained by a limited number of nonlinear dynamic analyses of the soil column with uncertain properties, as discussed in a companion article in this issue (Bazzurro and Cornell, 2004). The hazard at the soil surface (or at any desired
depth) is computed by convolving the site-specific hazard curve at the bedrock level
with the probability distribution of the amplification function.
The approach presented here provides more precise surface ground-motion-hazard estimates than those found by means of standard attenuation laws for generic soil conditions. The use of generic ground-motion predictive equations may in fact lead
to inaccurate results especially for soft-clay-soil sites, where considerable amplification is expected at long periods, and for saturated sandy sites, where high-intensity
ground shaking may cause loss of shear strength owing to liquefaction or to cyclic mobility. Both such cases are considered in this article. In addition to the proposed procedure, two alternative, easier-to-implement but approximate techniques for obtaining hazard estimates at the soil surface are also briefly discussed. One is based on running a conventional PSHA with a rockattenuation relationship modified to include the soil response, whereas the other consists of using a simple, analytical, closed-form solution that appropriately modifies the hazard results at the rock level.
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Rapid Excavation and Tunneling Conference Proceedings 2011
Author: Steve Redmond, Victor Romero | Size: 106 MB | Format:PDF | Quality:Unspecified | Publisher: Society for Mining Metallurgy & Exploration | Year: 2011 | pages: 1608 | ISBN: 0873353439, 9780873353434, 9780873353441
Every two years, industry experts and practitioners from around the world gather at the prestigious Rapid Excavation and Tunneling Conference (RETC) to learn about the latest developments in tunneling technology, and the signature projects that help society meet its growing infrastructure needs. Inside this authoritative 1608-page book, you’ll find the 115 influential papers that were presented providing valuable insights from projects worldwide. You’ll gain from the lessons learned—often the hard way—from large and demanding projects in difficult ground conditions.
This book will take you underground for a practical, up-close look into headline-making projects from around the globe. Virtually every aspect of tunneling is examined. It is an indispensable resource for design and construction engineers and contractors in the large-scale civil tunnel industry who want to stay on the leading edge of their profession.
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Author: KALIPRASANNA SETHY | Size: 850 KB | Format:PDF | Quality:Unspecified | Publisher: DEPARTMENT OF CIVIL ENGINEERING NATIONAL INSTITUTE OF TECHNOLOGY, ROURKELA | Year: 2011 | pages: 62
After 2001 Gujarat Earthquake and 2005 Kashmir Earthquake, there is a nation-wide attention to the seismic vulnerability assessment of existing buildings. There are many literatures available on the seismic evaluation procedures of multi-storeyed buildings using;nonlinear static (pushover) analysis. There is no much effort available in literature for seismic evaluation of existing bridges although bridge is a very important structure in any country. There are presently no comprehensive guidelines to assist the practicing structural engineer to evaluate existing bridges and suggest design and retrofit schemes. In order to address this problem, the aims of the present project was to carry out a seismic evaluation case study for an existing RC bridge using nonlinear static (pushover) analysis.
Bridges extends horizontally with its two ends restrained and that makes the dynamic characteristics of bridges different from building. Modal analysis of a 3D bridge model
reveals that it has many closely-spaced modes. Participating mass ratio for the higher modes is very high. Therefore, pushover analysis with single load pattern may not yield correct
results for a bridge model. A 12-span existing RC bridge was selected for the case study. Standard pushover analysis using FEMA 356 (2000) displacement coefficient method and an improved upper bound pushover analysis method were used to analyse the building. Some of the analysis parameters were suitably modified to use in a bridge structure. The evaluation results presented here shows that the selected bridge does not have the capacity to meet any of the desired
performance level.
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Author: David W. A. Rees | Size: 35 MB | Format:PDF | Quality:Unspecified | Publisher: World Scientific Publishing Company | Year: 2000 | pages: 734 | ISBN: 1860942180, 9781860942181
The 15 chapters in this volume are arranged in a logical progression. The text begins with the more fundamental materials on stress, strain and plane elasticity. There follows a full treatment of the theories of bending and torsion. Coverage of moment distribution, shear flow, struts and energy methods precedes a chapter on finite elements. Thereafter, the book presents yield and strength criteria, plasticity, collapse, creep, visco-elasticity, fatigue and fracture mechanics. Appended is material on the properties of areas, matrices and stress concentrations. Each topic is illustrated by worked examples and supported by numerous exercises.
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Green building technologies and materials:
selected, peer reviewed papers from the 2011 International Conference on Green Building Technologies and Materials (GBTM 2011), May 30, 2011, Brussels, Belgium
A major goal of this special collection of 47 peer-reviewed papers was to gather together the current knowledge of academic scientists, engineers and industrial researchers and have them share their experiences and research results concerning every aspect of green building technologies and materials, and discuss the practical challenges encountered and the solutions adopted. An interesting guide to this increasingly relevant subject.
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Fiber-reinforced polymer (FRP) composites are becoming increasingly popular as a material for rehabilitating aging and damaged structures. Rehabilitation of Metallic Civil Infrastructure Using Fiber-Reinforced Polymer (FRP) Composites explores the use of fiber-reinforced composites for enhancing the stability and extending the life of metallic infrastructure such as bridges.
Part I provides an overview of materials and repair, encompassing topics of joining steel to FRP composites, finite element modeling, and durability issues. Part II discusses the use of FRP composites to repair steel components, focusing on thin-walled (hollow) steel sections, steel tension members, and cracked aluminum components. Building on Part II, the third part of the book reviews the fatigue life of strengthened components. Finally, Part IV covers the use of FRP composites to rehabilitate different types of metallic infrastructure, with chapters on bridges, historical metallic structures and other types of metallic infrastructure.
Rehabilitation of Metallic Civil Infrastructure Using Fiber-Reinforced Polymer (FRP) Composites represents a standard reference for engineers and designers in infrastructure and fiber-reinforced polymer areas and manufacturers in the infrastructure industry, as well as academics and researchers in the field.
Looks at the use of FRP composites to repair components such as hollow steel sections and steel tension members
Considers ways of assessing the durability and fatigue life of components
Reviews applications of FRP to infrastructure such as steel bridges.
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