24 resultados para Post-tension
em Iowa Publications Online (IPO) - State Library, State of Iowa (Iowa), United States
Resumo:
Many state, county, and local agencies are faced with deteriorating bridge infrastructure composed of a large percentage of relatively short to medium span bridges. In many cases, these older structures are rolled or welded longitudinal steel stringers acting compositely with a reinforced concrete deck. Most of these bridges, although still in service, need some level of strengthening due to increases in legal live loads or loss of capacity due to deterioration. Although these bridges are overstressed in most instances, they do not warrant replacement; thus, structurally efficient but cost-effective means of strengthening needs to be employed. In the past, the use of bolted steel cover plates or angles was a common retrofit option for strengthening such bridges. However, the time and labor involved to attach such a strengthening system can sometimes be prohibitive. This project was funded through the Federal Highway Administration’s Innovative Bridge Research and Construction program. The goal is to retrofit an existing structurally deficient, three-span continuous steel stringer bridge using an innovative technique that involves the application of post-tensioning forces; the post-tensioning forces were applied using fiber reinforced polymer post-tensioning bars. When compared to other strengthening methods, the use of carbon fiber reinforced polymer composite materials is very appealing in that they are highly resistant to corrosion, have a low weight, and have a high tensile strength. Before the post-tensioning system was installed, a diagnostic load test was conducted on the subject bridge to establish a baseline behavior of the unstrengthened bridge. During the process of installing the post-tensioning hardware and stressing the system, both the bridge and the post-tensioning system were monitored. The installation of the hardware was followed by a follow-up diagnostic load test to assess the effectiveness of the post-tensioning strengthening system. Additional load tests were performed over a period of two years to identify any changes in the strengthening system with time. Laboratory testing of several typical carbon fiber reinforced polymer bar specimens was also conducted to more thoroughly understand their behavior. This report documents the design, installation, and field testing of the strengthening system and bridge.
Resumo:
A compilation of the six sections of David C. Mott's "Abandoned Towns, Villages and Post Offices of Iowa", that was published in the Annals of Iowa: V.17, #6 ,10/1930, pp. 435-465; V.17, #7 ,1/1931, pp. 513-543; V.17, #8 ,4/1931, pp. 578-599; V.18, #1 ,7/1931, pp. 42-69; V.18, #2 ,10/1931, pp. 117-148; V.18, #3 ,1/1932, pp. 189-220. (NOTE: this is a large file and may take a while to download.)
Resumo:
Using a matched sample of 1091 inmates released between April 1,1999 and June 30, 2001, Prison Industries Enhancement Certification Program (PIECP) participants re-enter society more successfully than Traditional Industries (TI) or other than work (OTW) releasees in terms of employment. The primary findings of this research are that Iowa state prison inmates who worked in open-market jobs in PIECP were found to be significantly more successful in post-release employment. That is to say, they became tax-paying citizens quicker and remain in that status longer than TI and OTW releasees. Additionally, PIECP releasees were incarcerated post release at a slower rate than OTW releasees.
Resumo:
Iowa has the same problem that confronts most states in the United States: many bridges constructed more than 20 years ago either have deteriorated to the point that they are inadequate for original design loads or have been rendered inadequate by changes in design/maintenance standards or design loads. Inadequate bridges require either strengthening or posting for reduced loads. A sizeable number of single span, composite concrete deck - steel I beam bridges in Iowa currently cannot be rated to carry today's design loads. Various methods for strengthening the unsafe bridges have been proposed and some methods have been tried. No method appears to be as economical and promising as strengthening by post-tensioning of the steel beams. At the time this research study was begun, the feasibility of posttensioning existing composite bridges was unknown. As one would expect, the design of a bridge-strengthening scheme utilizing post-tensioning is quite complex. The design involves composite construction stressed in an abnormal manner (possible tension in the deck slab), consideration of different sizes of exterior and interior beams, cover-plated beams already designed for maximum moment at midspan and at plate cut-off points, complex live load distribution, and distribution of post-tensioningforces and moments among the bridge beams. Although information is available on many of these topics, there is miminal information on several of them and no information available on the total design problem. This study, therefore, is an effort to gather some of the missing information, primarily through testing a half-size bridge model and thus determining the feasibility of strengthening composite bridges by post-tensioning. Based on the results of this study, the authors anticipate that a second phase of the study will be undertaken and directed toward strengthening of one or more prototype bridges in Iowa.
Resumo:
Contains information to be used by teachers in classrooms including history of the the United States flag, the government of Iowa, the Constitution of Iowa, the birth of Americanism, the Declaration of Independence, the Constitution of the United States, Lincoln's Gettysburg Address.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.
Resumo:
IPERS is prefunded, which means that while members are working they contribute to IPERS for their own future retirements. Contributions from employees and their employers, plus investment income, must be enough to cover the costs of future benefits that IPERS promises to pay.