Posted by: giguni - 11-15-2012, 11:11 AM - Forum: Archive
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New formulas derived from seismic interferometry to simulate phase velocity estimates from correlation methods using microtremor
Toshiaki Yokoi
Geophysics July 2010 v. 75 no. 4 p. SA71-SA83
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Posted by: andersen3 - 11-15-2012, 10:53 AM - Forum: Concrete
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Effect of adhesive stiffness and CFRP geometry
Author: Reeve Benjamin Zachary | Size: 2.54 MB | Format:PDF | Quality:Original preprint | Publisher: University of Pittsburgh | Year: 2005 | pages: 110
The current American Concrete Institute (ACI) recommendation intended to mitigate
debonding failure by limiting the allowable strain in the FRP (the limiting strain is referred to as
εfub) is shown to be non-conservative, overestimating the strain where debonding becomes likely
by two fold for the high modulus adhesive and less so for the low modulus adhesive. The
equation for estimating εfubrecommended by Teng et al. (2001), including the modifying kbterm,
appears to provide appropriatelyconservative estimates of debonding for the specimens having
low modulus adhesive although remains unconservative for the high modulus adhesive. This
indicates that the nature of the adhesive should be included in the calculation of limiting strain.
Proposed values for the coefficient kwhich accounts for the b b f/b ratio were found to generally
underestimate the effect of the width ratio for the test specimens. Therefore, not only is the ratio
bf/b (as represented by kb) a contributing factor to bond behavior, its contribution may be
underestimated. Cover delamination (end peel debonding) was effectively mitigated in all
specimens by extending the CFRP close to the support along the relatively long shear span.
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Author: Hayward, Alan / Weare, Frank / Oakhill, A. C. | Size: unknown MB | Format:PDF | Quality:Unspecified | Publisher: Wiley-Blackwell | Year: 2011 | pages: 184-192
This highly illustrated manual provides practical guidance on structural steelwork detailing. Examples of structures include single and multi-storey buildings, towers and bridges. The detailing shown will be suitable in principle for fabrication and erection in many countries, and the sizes shown will act as a guide to preliminary design. The third edition has been revised to take account of the new Eurocodes on structural steel work, together with their National Annexes. The new edition also takes account of developments in 3-D modelling techniques and it includes more CAD standard library details.
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Concrete Repair, Rehabilitation and Retrofitting III - REQUEST
Author: Mark G. Alexander, Hans-Dieter Beushausen, Frank Dehn, Pilate Moyo | Size: unknown MB | Format:PDF | Quality:Unspecified | Publisher: CRC Press | Year: 2012 | pages: 546
The Third International Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR 2012) was held in Cape Town, South Africa, from 3 to 5 September 2012. The conference was the latest in a sequence of ICCRRR international conferences, the two previous ones having also been held in Cape Town in 2005 and 2008. It was again a collaborative venture of the Universities of Cape Town and The Witwatersrand, and the Construction Materials Sections at Leipzig University and MFPA Leipzig in Germany.
The conference was also an occasion to honour the considerable achievements of Professor Joost Walraven of TU Delft who has made, as a researcher and as an engineer, outstanding and international contributions to the development and application of new construction materials, new structures, and structural models.
This 3rd ICCRRR was held in conjunction with the Annual RILEM Week – marking the first time that RILEM had held its annual event in sub-Saharan Africa. The African continent is on the move, and the next decades will provide great opportunities for expansion on this continent of science and technology, industry and culture. For this reason, it was timely that the RILEM Week was held in Cape Town.
Considerable progress has been made in recent years in understanding deterioration mechanisms for concrete, and in repair and rehabilitation technologies. Nevertheless, a vast stock of concrete infrastructure worldwide remains in a serious state of disrepair, and substantial work is needed to maintain and possibly restore it to acceptable levels of service, cost-effectively. Confidence in concrete as a viable construction material must be retained and sustained, particularly considering the environmental challenges that the industry and society now face.
The conference proceedings contain papers presented at the conference, classified into a total of 12 sub-themes which can be grouped under the five main themes of (i) Concrete durability aspects, (ii) Condition assessment of concrete structures, (iii) Concrete repair, rehabilitation and retrofitting, (iv) Developments in materials technology, assessment and processing, and (v) Concrete technology and structural design. In terms of submissions, major foci of interest are the fields of innovative materials for durable concrete construction, integrated service life modelling of reinforced concrete structures, NDE/NDT and measurement techniques, repair methods and materials, and structural strengthening and retrofitting techniques. The large number of high-quality papers presented and the wide range of relevant topics covered confirm that these proceedings will be a valued reference for many working in the important fields of concrete durability and repair, and that they will form a suitable basis for discussion and provide suggestions for future development and research.
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The report examines the problem of establishing values of properties of seismic isolation bearings in the analysis and design of seismically isolated bridges. These bounding values of properties are determined with the use of system property modification factors. The property modification factors account for the effects of history of loading, the environmental conditions, and aging on the properties of the isolation bearings. The procedure requires that the mechanical behavior of the bearings be understood at both the macroscopic and microscopic levels. The report focuses on the effects of aging in elastomeric bearings and sliding bearings. The nature of friction in sliding bearings is also discussed. Property modification factors are presented for the effects of aging, contamination, travel, temperature, and scragging for selected interfaces and elastomeric bearings. The values represent the basis on which the bounding analysis is described in the 1999 AASHTO Guide Specifications for Seismic Isolation Design. (Adapted from authors' abstract).
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This monograph introduces the basic concepts of passive energy dissipation and discusses current research, development, design and code-related activities in the field. The authors provide basic definitions for passive energy dissipation systems and provide basic design principles governing their use. Mathematical modeling, recent developments, and modern applications of the following devices are covered in depth: Metallic Dampers, Viscoelastic Dampers, Tuned Mass Dampers, Friction Dampers, Viscous Fluid Dampers and Tuned Liquid Dampers. The final chapter in the monograph discusses semi-active control systems. Semi-active mass dampers and semi-active fluid dampers have been installed in buildings in Japan, and are discussed in some detail, along with current research in the field. Tables are provided in the appendices that detail application of passive energy dissipation systems in North America and active and semi-active systems in Japan.
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A fractional derivative Maxwell model is proposed for viscous dampers which are used for vibration isolation of piping systems, forging hammers and other industrial equipment, as well as for vibration and seismic isolation of building structures. The development and calibration of the model is based on experimentally observed dynamic characteristics. The proposed model is validated by dynamic testing and very good agreement between predicted and experimental results is obtained. Some analytical results for a single-degree-of-freedom viscodamper system are presented. These results are useful to the design of vibration isolation systems. An equivalent viscous oscillator is defined whose response is essentially the same as that of the viscodamper isolator. The model is employed in the analysis of a base-isolated model structure which has been tested on a shake table.
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This report is concerned with a study of two different devices, a combination of tapered-plate energy absorber (TPEA) and viscoelastic dampers and a combination of TPEA and fluid dampers. It starts with a general review of the developments in various energy dissipating devices. Then a finite element formulation for fluid dampers is developed for this study. A comparison is made between numerical solutions and experimental results when a 2/5 scale steel structure is equipped with added viscoelastic dampers. The structural response of high-rise buildings mounted with three energy absorbing devices, tapered-plate energy absorber (TPEA), viscoelastic dampers, fluid dampers, and two combined devices, TPEA and fluid dampers and TPEA and viscoelastic dampers, respectively, have been investigated. Next, a parametric study of TPEA devices for high-rise buildings is conducted. The selected response parameters in this study include: 1) story shear force; 2) floor displacement; 3) base shear force; and 4) ductility ratio. Finally, two combined devices, TPEA and viscoelastic dampers and TPEA and fluid dampers are examined. Results show such combined devices provide a strong safe-failure mechanism as reliable energy absorbing devices. They also can sustain a wide range of loadings from minor to severe earthquake ground motion and wind loads. The combined devices can compensate for each other's shortcomings so that a satisfactory design for wind loads and seismic hazard mitigation of the structures can be achieved.
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This report focuses on two fundamental issues related to the design of nonlinear viscous dampers for building structures: structural velocities and equivalent viscous damping. It begins with an overview of the capacity-demand spectral design approach and includes various steps involved in the pushover analysis to determine the structural capacity. An alternative elasto-plastic analysis approach is also introduced. Fundamental considerations for the design of supplmental damping systems are reviewed and the design formulations for a pseudo-actual velocity transformation are given following a discussion of the differences between the two quantities. The proposed equivalent linear damping for the nonlinear [viscous nature] devices based on the equivalent power comsumption approach is presented. Finally, various phases involved in designing supplemental systems are given Design steps for 2 alternative device configurations are given. A retrofit design example of a 9-story flexible steel building is presented and the performance of the two alternative configurations is discussed.
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SAP2000 is a recently released commercial structural analysis program with capabilities for dynamic analysis of structures with isolation and energy dissipation systems. This report presents five verification examples in which results obtained by SAP2000 are compared to experimental results and to results obtained by programs 3D-BASIS and ANSYS. Three of the examples involve seismically isolated structures, of which, one was tested on the shake table under conditions resulting in bearing uplift. The other two examples involve structures with linear and nonlinear fluid viscous energy dissipation devices, which were also tested on the shake table. In general, SAP2000 produced results in excellent agreement with other analysis programs and in good agreement with experimental results, except for the case of the structures tested with nonlinear viscous damping devices. In this case, SAP2000 underpredicted the displacement response of the structure.
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The 1997 AASHTO "Guide Specifications for Seismic Isolation Design" specify response modification factors for the substructures of isolated bridges that are lower than those specified for the substructures of non-isolated bridges. This report presents the rationale behind these specifications and presents research results that lead to the establishment of appropriate response modification factors for isolated bridges. The research concentrated on the dynamic analysis of simple models of seismic-isolated and non-isolated bridges for a range of isolated system and substructure behaviors, and for seismic excitation characterized by AASHTO ground motion spectra for a range of soil conditions and acceleration coefficients. The study investigated the displacement ductility demands in the substructure of these bridges and established the appropriate value of the ductility-based portion of the response modification factors. This was achieved by comparing the displacement ductility ratio for the substructures of isolated and non-isolated bridges. The study concludes that response modification factors should be lower in the substructures of isolated bridges than in the substructures of non-isolated bridges because: (a) elastic or nearly elastic substructure behavior is required for proper behavior of the isolation system, and (b) isolated bridges exhibit more sensitivity in the substructure inelastic response due to variability in the seismic input.
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The Recommended Guidelines consist of specifications, commentary, and appendices developed to be compatible with the existing load-and-resistance-factor design (LRFD) provisions for highway bridges published by AASHTO. This two-volume set offers the Specifications in Part I and the Commentary and Appendices in Part II. The new, updated provisions are nationally applicable and cover all seismic zones, as well as all bridge construction types and materials. They reflect the latest design philosophies and approaches that will result in highway bridges with a high level of seismic performance. This report contains numerous innovative and updated requirements and procedures, including: state-of-knowledge seismic hazard maps developed by the USGS; recommended design earthquakes and performance objectives; guidance on assessment of liquefaction and design solutions; new soil factors and spectral shapes; seismic design requirements for steel bridges; “no analysis” design concepts; some seismic resisting systems and elements not permitted in the current AASHTO provisions; capacity spectrum design procedures; displacement capacity verification (“Pushover”) analysis; and cost comparisons and implications. Equations, figures, and tables appear throughout this report.
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The effect of near-field and soft-soil ground motions on structures with viscous-damping systems was examined. Damping modification factors for damping ratios up to 100% of critical were obtained for sets of near-field and soft-soil ground motions and compared to the values presented in the 2000 NEHRP Recommended Provisions. A study was carried out for the ductility demand in structures with and without damping systems, where the damped buildings were designed for a smaller base shear than conventional buildings in accordance with the 2000 NEHRP Provisions. Nonlinear response-history and simplified methods of the 2000 NEHRP Provisions were used to analyze single-degree-of-freedom systems and 3-story moment frames with linear viscous and nonlinear viscous damping systems to acquire knowledge on the influence of near-field and soft-soil ground motions on the accuracy of simplified methods of analysis. An extensive use of figures is provided throughout the report.
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Assessing the variability of ground motions, σ, is an inescapable reality in the ground-motion prediction process, since the appropriate characterization of ground motions needs to acknowledge the large degree of scatter associated with these motions. The value of σ has remained fairly stable over the past 40 years, with values typically lying between 0.10 and 0.40 log10 units (about 0.23 to 0.92 ln units) and most commonly falling in the range of 0.15 to 0.35 log10 units (0.35 to 0.80 ln units). The resistance of σ to any efforts made to reduce its value is a matter of great concern to ground-motion prediction in general and seismic hazard analysis in particular, in view of the significant impact the value of σ has on hazard estimates. This impact has sometimes led to the temptation of ignoring σ altogether, but it is now accepted that the inclusion of σ, rather than being an option that can be switched on and off, is an integral part of any seismic hazard assessment process.
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IsiPlot is a software developed to help the modellers (and not only....) to print scaled plans.
- Viewing and printing of DXF and raster files (.BMP, .GIF, .TIF, .JPG etc.)
- Now you have the possibility to export from DXF to high resolution raster files.
- You can scale and select the printing area in a very simply way
- IsiPlot let's you to print large plans (A0 and bigger) using little A4 printer
IsiPlot is a program that we can print images in scale, is the perfect tool to print the maps published here. supports raster formats (jpg, png, gif, etc) and even dfx, autocad format.
How to use the program is very simple, we loaded the plane in the program and proceed to calibrate the picture, for it in the upper right corner we click the rule, we go to the drawing and click in one end of a line which we know its measure, click on the other end and opens a window where you enter the measure, we can do it in inches or centimeters.
Now click on the scale to tell the program if you want to print to 1:1 or another selection, then the software does is, taking into account the actual size of the pieces drawn, distributes flat sheets DIN A-4 for after printing and mounting, the leaves can also print the set, with margin, no margin, print all or only a certain IsiPlot and printed marks to facilitate our assembly.
Private Note:
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This book represents several decades of data collection, research, conversations with different airframe specialists, plus the author's more than twenty years' experience in airframe structural design. From structural standpoint, the book is intended to be used as a tool to help achieve structural integrity according to government regulations, specifications, criteria, etc., for designing commercial or military transports, military fighters, as well as general aviation aircraft. It can be considered as a troubleshooting guide for airline structural maintenance and repair engineers or as a supplementary handbook in teaching aircraft structural design in college. This book is divided into a total of sixteen chapter and emphasizes itemized write-ups, tables, graphs and illustrations to lead directly to points of interest. The data can be used for designing and sizing airframe structures and, wherever needed, example calculations are presented for clarification.
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