Nonlinear analysis of the end zones of prestressed concrete girders

Pretensioned concrete girders have been used for many years in construction. Nevertheless, optimization is still possible, especially regarding the anchorage zones. These are typically subjected to different types of stresses due to the local transmission of the prestressing force. By using a 3D nonlinear finite element model, the stresses and cracks in the anchorage zone due to the prestressing forces can be predicted in a more reliable manner. In this paper two 3D FE models are developed by using the concrete damage plasticity model in Abaqus. In the first model, the load transfer is defined by creating a shear force around each strand. In the second model, the interaction between the strands and the concrete is created by using surface-to-surface contact elements with friction. Finally, to validate the models, the results are compared with strain measurements on a precast beam during production at a precast concrete plant

Evaluating Differences in Household Subsistence Harvest Patterns between the Ambler Project and Non-Project Zones

Western Alaska is one of largest inhabited, roadless areas in North America and, indeed, the world. Access, via a new road that would transverse Gates of the Arctic National Park and Preserve (GAAR), to a mining district in a vast roadless section of northwest Alaska has been proposed. Given the potential effects of the road on nearby communities, we analyzed how communities connected to the road system compare to their unconnected counterparts. Specifically, using zero inflated negative binomial models, we analyzed subsistence harvest data to understand factors that influence subsistence production at the household level. We found substantial difference in these factors between communities near the proposed road (project zone (PZ) communities and a comparable set of road accessible communities outside the region, and were affected by household characteristics such as the gender of the head of household, number of children, and income. Total subsistence production of project zone communities was 1.8 – 2.5 times greater than that of non-project zone communities. Communities with a higher percentage of Alaska Native residents had greater per capita subsistence harvests. Higher household income levels were associated with lower subsistence harvest levels. Roads can provide access for hunters from outside the region to traditional subsistence hunting grounds used by local residents that would not be very accessible if not for the road. Our proxy for competition (number of nonlocal moose hunters) indicates that resident moose harvest amounts are inversely related to the number of hunters in a particular area. If subsistence harvest patterns for project zone communities currently off the road changed to mirror existing non-project zone harvests due to the road, the financial cost would be USD $6,900 – 10,500 per household per year (assuming an$8/lb. ‘replacement’ cost for subsistence harvests). This represents about 33% of the median household income. Taken together, our results suggest that the proposed road should be expected to substantially impact subsistence production in communities that are not currently connected to the road system. The scale of our data did not allow for the comparison of the impacts of the different proposed routes but the impacts of different routes is likely minor in relation to the presence or absence of the proposed roadFigures / Tables / Abstract/Executive Summary / Acknowledgments / Introduction / The Proposed Road and Mine / Study Area / Communities / Background / Modeling Household Harvest / Conclusions / Literature CitedYe

Investigation of prestressed reinforced concrete for highway bridges, part V, analysis and control of anchorage-zone cracking in prestressed concrete

Cover title.Prepared as part of an investigation conducted by the Engineering Experiment Station, University of Illinois at Urbana-Champaign

A Catalog of Hydroclimatological Data for Alaska's Coastal Zone

In order to perceive a better understanding of the interrelationships of the coastal zone water we proposed a research project which was to sort out many of the complex variables. The project was not begun due to the lack of sufficient funds. We did, however, begin a limited literature search and listing of hydroclimatological data sources of Alaska's coastal zone. We felt this would be a modest but useful start towards the larger study. It should also have some practical usefulness to others. This data catalog is a result of this initial study. Because of the wide variety of types of agency which collect data and the literally hundreds of sources through which they are reported, it is often quite bewildering for even experienced investigators to sort out what can be found and where. Although we are sure that the catalog is far from complete, we feel that it is a useful beginning towards an attempt to better understand the hydroclimatological processes in Alaska's coastal zone. We wish to invite contributions and criticisms which could lead to an improved and more comprehensive version at some future date.We gratefully acknowledge the support of the Sea Grant Program of the University of Alaska and the support and encouragement of its Director, David Hickok. The project also received support from the Office of Water Resources Research and the State of Alaska through the Institute of Water Resources at the University of Alaska

Copper mineral occurrences in the Wrangell Mountains-Prince William Sound area, Alaska

On January 9, 1970, the U.S. Bureau of Mines entered into an agreement with the University of Alaska based upon a proposal submitted by the Mineral Industry Research Laboratory. Under the terms of this agreement, the Laboratory undertook to compile information on copper occurrences in eight quadrangles covering what are loosely known as the Copper River, White River, and Prince William Sound copper provinces. If time permitted four other quadrangles would be added, and this has been possible. Information was to be obtained by searching published and unpublished records of the Bureau of Mines, the U.S. Geological Survey, the State Division of Geological Survey, the University of Alaska, and the recording offices

Non-linear 3D finite element analysis of the anchorage zones of pretensioned concrete girders and experimental verification

This paper focuses on the modelling of the anchorage zone of a pretensioned girder. The finite element software Abaqus was used to create a 3D non-linear finite element model (FEM). This analysis was performed on a full-scale pretensioned girder with end blocks and with various types of strand modelling, where accurate contact properties between prestressing steel and concrete are essential. The model has been validated by comparing the numerical strain results with the strain measurements on a full-scale girder with end blocks, which was produced in a precast concrete plant. At the same time, a parametric study was executed to determine the value of the coefficient of friction between the strands and the concrete and to examine the sensitivity of the input parameters of the model. The results have indicated that an accurate determination of the concrete properties at the time of release is very important. Furthermore, the Hoyer effect is analysed. It is found that the radial expansion of the strand in the finite element model is in good agreement with the theoretically calculated expansion of the strand which demonstrates the accuracy of the finite element model. In addition, it is shown that the Hoyer effect influences the force transfer of two adjacent strands. The aim of this research is to investigate the potential of an alternative FE model of a pretensioned girder based on strand to concrete frictional behaviour, rather than the commonly used models based on an assumed shear stress distribution along the transfer length

A Program for the Collection, Storage, and Analysis of Baseline Environmental Data for Cook Inlet, Alaska

The scope of this report is to provide a general, yet comprehensive, description of the Cook Inlet System which will serve as a basis for understanding the interrelated natural and man-made factors governing its future; to present a program of field research studies for the estuarine environment that will describe the existing state of the Inlet with respect to the water quality and biota; to provide a framework whereby the program of studies can be evaluated and redirected in light of the preliminary results; and, to provide a method of storing and analyzing the data from the investigations so that it can be made available to interested parties in the most efficient manner possible.This report was prepared by the Institute of Water Resources of the University of Alaska for the Alaska Water Laboratory, Federal Water Pollution Control Administration under Contract No. 14-12-449

Investigation of Shallow Sedimentary Structure of the Anchorage Basin, Alaska, Using Simulated Annealing Inversion of Site Response

This study deals with shallow sedimentary structure of the Anchorage basin in Alaska. For this purpose, inversion of site response [SR(f)] data in the frequency range 0.5-11.0 Hz from various sites of the basin has been performed using the simulated annealing method to compute subsurface layer thickness, shear-wave velocity (beta), density, and shear-wave quality factor. The one-dimensional (1D) models for the aforementioned parameters were obtained with preset bounds on the basis of available geological information such that the L-2 norm error between the observed and computed site response attained a global minimum. Next, the spatial distribution of the important parameter beta was obtained by interpolating values yielded by the 1D models. The results indicate the presence of three distinct velocity zones as the source of spatial variation of SR(f) in the Anchorage basin. In the uppermost part of the basin, the beta values of fine-grain Quaternary sediments mainly lie in the range of 180-500 m/sec with thickness varying from 15 to 50 m. This formation overlies relatively thick (80-200 m) coarse-grain Quaternary sediments with beta values in the range of 600-900 m/sec. These two Quaternary units are, in turn, overlain on Tertiary sediments with beta > 1000 m/sec located at depths of 100 and 250 m, respectively, in the central and western side along the Knik Arm parts of the basin. The important implication of the result is that the sources of spatial variation of SR(f) in the Anchorage basin for the frequency band 0.5-11 Hz, besides in the uppermost 30 m, are found to be deeper than this depth. Thus, use of commonly considered geological formations in the depth intervals from 0 to 30 m for the ground-motion interpretation will likely yield erroneous results in the Anchorage basin.GIEnvironment and Natural Resources InstituteSchool of Engineering of the University of Alaska, AnchorageGeological Science