CENTRIFUGE MODELING OF LATERALLY LOADED BATTERED PILE GROUPS IN SAND
Author: McVay, M C University of Florida, Gainesville Gardner, R ZHANG, L | Size: 6.68 MB | Format:PDF | Quality:Original preprint | Publisher: University of Florida, Gainesville | Year: 1997 | pages: 258
This research is part of an on-going study of the effects of ship impact loads on waterway structures underlain by pile foundations. The objectives of this research are: (1) To modify the existing pile driver and make it capable of driving 3 by 3 and 4 by 4 battered pile groups in flight onto a base plate and achieve fixed head conditions at the pile cap; (2) To instrument each of the piles in both groups to measure shear and axial force and bending moment; (3) To conduct the lateral load tests in samples with relative densities of 36% and 55% and also to test with dead loads equivalent to 20%, 50%, and 80% of the vertical capacity of the model pile group; (4) To analyze the effect of dead load on the lateral capacity at different relative densities; (5) To gather data about the internal force distribution of the pile groups and to investigate the pattern of pile group rotation; and (6) To use measured test data to validate a coupled bridge superstructure-foundation finite-element-code (FLORIDA-PIER).
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Development of a Coupled Bridge Pier and Foundation Finite Element Code
Author: Hoit, M McVay, M Hays, C O | Size: 3.78 MB | Format:PDF | Quality:Original preprint | Publisher: University of Florida, Gainesville | Year: 1998 | pages: 117
The University of Florida, Department of Civil Engineering developed Florida Pier (FLPIER) in conjunction with the Florida Department of Transportation (FDOT), Structures Division. The first official release of the program was version 5.23 in January 1996. A new release (version NT 1.15) is now available which includes many enhancements including mixed prestressing and mild steel reinforcement, nonlinear pier columns and cap, tapered pier columns and cap, equivalent linear stiffness matrix generation and many other features. In addition, the new release is a Windows NT/95 based program including the graphics portions. The program is capable of analyzing an entire bridge substructure (piles, cap and pier) in conjunction with its soil support resulting in a nonlinear coupled foundation analysis. The new release is a step closer to a complete design program, allowing engineers to optimize their structures. The program was designed to allow input to be specified graphically using "designer" variables such as pile spacing, column offsets, number of columns, batter, missing piles and more. The program is distributed freely by the FDOT through their web site. Both the Federal Highway Administration and FDOT have funded efforts to add additional capabilities to enhance the programs. The next FDOT release is expected in November 1998 and will include pier design capabilities. The added features of the current release are summarized and the complete users manual is included in this document.
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THE RESPONSE OF PILES DURING EARTHQUAKES: DYNAMIC SOIL-PILE-SUPERSTRUCTURE INTERACTIONS
Author: Boulanger, R W Kutter, B L Wilson, D W | Size: 5.83 MB | Format:PDF | Quality:Original preprint | Publisher: University of California, Davis | Year: 1998 | pages: 125
The dynamic response of pile foundations in soft clay and liquefiable sand during strong earthquake shaking was evaluated. The research consisted of two major components: (1) a series of dynamic centrifuge tests of pile-supported structures in soft clay and liquefiable sand; and (2) an evaluation of dynamic "beam on a nonlinear Winkler foundation" (BNWF) analysis methods against the centrifuge model results. The dynamic centrifuge modeling techniques were critically evaluated in detail because these tests were among the first performed using the new shaking table on the 9-m radius centrifuge. The results of this evaluation will benefit other current and future projects utilizing the large centrifuge. Several BNWF computer programs were shown to give consistent results for similar idealizations of a physical problem. Two new p-y elements were implemented into the program GeoFEAP. The representation of radiation damping was shown to be important in certain cases, with series radiation damping being technically preferred over parallel radiation damping in such cases. Calculated responses for a single pile in soft clay were in good agreement with the centrifuge data when using series radiation damping and a p-y element with gapping ability. The p-y resistance of liquefied sand was shown to be strongly dependent on relative density and displacement level. Time histories of p-y resistance were obtained by backcalculation techniques for the soft clay and liquefied sand tests. The p-y resistance of liquefied sand shows characteristics that are consistent with the expected stress-strain behavior of liquefied sand, including the effects of relative dentify, dilation, cyclic degradation, and prior displacement history. If a scaling factor approach is used to approximate the effects of liquefaction on p-y resistance, then pseudo-static p-y analyses suggest a scaling factor of about 0.1-0.2 would be appropriate for Dr=35-40% sand and a scaling factor of about 0.25-0.35 would be appropriate for Dr=55-60% sand. It is emphasized that the use of an apparent p-y scaling factor for liquefied sand was shown to be a simplistic approximation to a complex phenomenon, and therefore its use in design requires considerable judgment.
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Author: Horne, J C Kramer, S L | Size: 5.29 MB | Format:PDF | Quality:Original preprint | Publisher: Washington State Transportation Center | Year: 1998 | pages: 140
Liquefaction of soils has caused considerable damage to pile-supported structures such as bridges and buildings in earthquakes. This project attempted to identify the most important impacts of liquefaction on pile foundations and to develop and verify new tools that allow those effects on pile foundation performance to be evaluated. A literature review indicated that the majority of damage to pile foundations has been caused by lateral movement of liquefied soil. Evaluation of the effects of lateral spreading on pile foundations requires that the soil displacements caused by lateral spreading be predicted and that the response of a pile foundation to those lateral displacements be predicted. In answer to the shortcomings of currently available estimation procedures, this project developed computational models for predicting lateral spreading deformations and pile-soil interaction. To validate the models against closed-form elastic solutions, they were compared with other computer programs that have some of the capabilities of the models and with field performance from available case histories. Free-field ground surface displacements produced by lateral spreading vary widely, but they are influenced most strongly by the initial and residual shear strength of the liquefiable soil, the gradation of the liquefiable soil, the initial state of shear stress within the deposit, the earthquake magnitude, and the distance from the site to the fault rupture zone. Pile response to lateral spreading is strongly dependent on surface slope, soil strength, and pile flexural stiffness, but it is relatively independent of groundwater table depth, pile diameter, pile length, and p-y curve stiffness. Both models developed in this study account for nonlinear, inelastic soil behavior and consider the development of excess porewater pressure and its effects on soil stiffness and strength. The pile-soil interaction model accounts for frequency-dependent radiation damping behavior in the time domain and allows computation of dynamic pile displacements, bending moments, shear forces, and soil reactions. By allowing computation of free-field displacements both at and below the ground surface and by considering the effects of those motions on the pile throughout earthquake shaking, the proposed model offers a practical, rational tool for evaluating lateral spreading effects on pile foundations.
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GEOTECHNICAL PERFORMANCE OF A HIGHWAY EMBANKMENT CONSTRUCTED USING WASTE FOUNDRY SAND
Author: Fox, P J Mast, D G | Size: 4.10 MB | Format:PDF | Quality:Original preprint | Publisher: Purdue University/Indiana Department of Transportation JHRP | Year: 1998 | pages: 110
The purpose of this study was to evaluate the use of waste foundry sand (WFS) as a highway embankment material in a full-scale field demonstration project. This evaluation included geotechnical concerns, such as deformation, strength, hydraulic conductivity, and ease of construction. The report presents an introduction and previous research concerning WFS use in highway construction. A geotechnical laboratory testing program characterized the WFS used in the project, which was a waste product of Auburn Foundry, Inc., located in Auburn, Indiana. This study was also a part of the Federal Highway Administration Priorities Technology Program. The project site was a 275 m section of the County Route 206 highway project near Butler, Indiana. Three sections of the embankment were studied: a section built with clay borrow, a section built with natural sand, and a section built with WFS. The embankment was built during the summer of 1996. This report presents field testing data with regard to vertical and lateral deformations of the WFS embankment, in situ changes in pore pressures in the foundation soil during construction, and the post-construction in situ penetration resistance of the WFS. The performance of the WFS section is compared to that of the clay borrow and natural sand sections of the embankment. The results of laboratory and field testing of the Auburn Foundry WFS provide general guidelines for the choice of geotechnical parameters for preliminary design of WFS embankments. From a geotechnical perspective, the results indicate that WFS can be used successfully as embankment fill material for full-scale highway projects.
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This report documents two studies that were conducted to review, assess, and provide recommendations regarding the seismic design of bridge foundations. Specifically, the report addresses modeling approaches and parameters that affect the seismic design and response of pile groups and drilled shafts. The report attempts to bridge the interface between the structural and geotechnical design process by describing a two-step design and analysis procedure for these bridge foundation components. Recent research results on pile group effects and the design of pile foundations to resist lateral spreading of liquefiable soils are also reviewed. Recommendations are provided concerning: modifications to p-y curves to account for cyclic loading conditions, pile group effects and soil-pile interaction behavior, and development of p-y curves for the design of drilled shafts.
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IDENTIFICATION AND STABILIZATION METHODS FOR PROBLEMATIC SILT SOILS
Author: McManis, K Nataraj, M Barbu, B G | Size: 8.09 MB | Format:PDF | Quality:Original preprint | Publisher: University of New Orleans | Year: 2001 | pages: 184
Many areas of Louisiana consist of soils with high silt contents, low strengths, and minimal bearing capacity. Construction traffic in these soils can cause detrimental pumping action in areas with a high water table. These wet subgrades under Louisiana pavements cause both construction and performance problems. Common solutions to the problem include excavation and replacement, lime treatment, or cement stabilization. Special provisions are often included in the contract for chemical additives in lieu of undercutting. The research emphasis of this study was placed on efforts to refine the pumping problem and on the development of guidelines for identifying the problem silt-soils. Secondary importance was given to the identification of alternate methods for stabilization. The study consisted of two phases. Phase 1 documented the field experiences of the Louisiana Department of Transportation and Development (DOTD) districts. Phase 2 consisted of a testing program to investigate the nature of the problem, the character of the silt materials, and their performance with modifying and stabilizing agents. Eight soil samples from four of the DOTD districts were used in the laboratory program. The soils were typical examples of those commonly encountered with a high-silt content. Several were acquired from current projects in which pumping problems were occurring. The basic characteristic-parameters of the natural samples were determined with standard laboratory tests. The response and stability of the silts under compaction and loading with various moisture levels and compaction efforts were also tested. The susceptibility to pumping of the different samples was reviewed in terms of their physical characteristics. In addition to the silt content percentage, the plasticity character was noted as significant during testing. Anomalies were also found to exist between the DOTD's earthwork specifications and the physical properties of the high silt-content soils. The potential for the modification and stabilization of the problem silt soils was also studied. The laboratory tests were selected with respect to construction needs and possible post construction conditions. A limited number of specific additives were proposed with consideration for their ability to dry the subgrade silts sufficiently in order that they be compacted and with the strength to provide a working table for the construction of the base and pavement. The additives selected included hydrated lime, portland cement, and Class C fly ash. Limited tests for evaluating long-period stability of the stabilized silt-subgrade subjected to accelerated curing followed by vacuum-saturation conditions were also conducted.
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Load and Resistance Factor Design (LRFD) for Reliability Analysis/Design of Piles Axial Capacity
Author: Rahman, M Shamimur | Size: 3.28 MB | Format:PDF | Quality:Original preprint | Publisher: North Carolina State University, Raleigh | Year: 2002 | pages: 347
Resistance factors were developed for use as a part of the implementation of the Load and Resistance Factor Design (LRFD) method of driven piles’ axial capacity. Resistance factors were calibrated in the framework of reliability theory utilizing pile load test data available from North Carolina Department of Transportation (NCDOT). Resistance statistics were evaluated for each data case in terms of bias factors. Reliability analyses on the current practice of pile foundation design by the Vesic, Meyerhof, and Nordlund methods were performed to evaluate the level of safety and to select target reliability indexes. Two types of First Order Reliability Method, Mean Value First Order Second Moment method and Advanced First Order Second Moment method, were employed for the reliability analysis and the calibration of the resistance factors. Recommended resistance factors for the three design methods (Vesic, Meyerhof, and Nordlund) are presented for the target reliability indexes of 2.0 and 2.5. Seven design categories for which the resistance factors are recommended are coastal concrete square pile with N@Toe<=40, coastal concrete square pile with N@Toe>40, coastal steel HP pile, coastal steel pipe pile, coastal concrete cylinder pile, piedmont concrete square pile, and piedmont steel HP pile. The resistance factors were calibrated separately for total, skin and toe capacities in an attempt to develop a correlation between the three resistance factors for each design category. In many cases, however, the resistance factor for total capacity is larger than both the skin and toe resistance factors and only total capacity factors are recommended. The resistance factors developed and recommended from this research are specific for the distinct soil types of North Carolina and for the unique practice of pile foundation design in the NCDOT.
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"Continuum Damage Mechanics and Numerical Applications" presents a systematic development of the theory of Continuum Damage Mechanics and its numerical engineering applications using a unified form of the mathematical formulations in anisotropic and isotropic damage models. The theoretical framework is based on the thermodynamic theory of energy and material dissipation and is described by a set of fundamental formulations of constitutive equations of damaged materials, development equations of the damaged state, and evolution equations of micro-structures.
According to concepts of damage-dissipation of the material state and effective evolution of material properties, all these advanced equations, which take nonsymmetrized effects of damage aspects into account, are developed and modified from the traditional general failure models so they are more easily applied and verified in a wide range of engineering practices by experimental testing.
Dr. Wohua Zhang is a Professor at Engineering Mechanics Research Center in Zhejiang University of China. Dr. Yuanqiang Cai is a Professor at Department of Civil Engineering in Zhejiang University of China.
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Exercises in Building Construction, Fourth Edition provides a fully revised, user-friendly exercise book to supplement the fourth edition of Fundamentals of Building Construction.
* Includes more than 40 exercises in "real world" construction problem solving; encourages students to apply information learned in classroom.
* Exercises are clearly presented with detailed line drawings; easy for student and instructor to follow.
* Revised to correspond with the fourth edition of Fundamentals of Building Construction.
* Includes companion web pages for instructor use, containing Answer Key and sample drawings.
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