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Author: Fernando Rafael Benitez Ortiz Publisher: ISBN: Category : Concrete Languages : en Pages : 184
Book Description
The Arkansas Department of Transportation (ARDOT) has identified bridge deck cracking shortly after concrete decks are placed and prior to applying traffic loads. Previous researchers have confirmed improper construction practices and design methods can lead to deck cracking. Currently, many contractors throughout Arkansas are using continuous deck pours. This construction approach may restrict the concrete slab from movement during early age shrinkage, causing tensile stresses to develop. The final stresses at the end of construction must be lower than the concrete tensile strength, if not cracking issues will develop. Eventually, these cracks may enlarge due to service load stresses and environmental damage. A nation-wide Department of Transportation (US DOTs) survey was performed to investigate the early age cracking extensiveness level in other state's bridges and what corrections, if any, they have made to address this problem. Additionally, Arkansas bridges with early age cracking were visited to examine any trends and inform instrumentation for bridge testing. A bridge deck was instrumented with 32 vibrating wire strain gauges prior to concrete placement to investigate strain and temperature changes in the first 14 days. Eurocode and ACI approximations for concrete mechanical properties were compared to field measured data for improving the understanding of an early age concrete deck behavior in a continuous steel bridge. Stress analysis study through the span length of bridge 030428 detected some locations prone to concrete cracking due to the variability of concrete mechanical properties and stress developed in the concrete deck. This thesis describes the results of this monitoring and anything that can be learned about formation of concrete stresses in continuous concrete bridge deck pours.
Author: Fernando Rafael Benitez Ortiz Publisher: ISBN: Category : Concrete Languages : en Pages : 184
Book Description
The Arkansas Department of Transportation (ARDOT) has identified bridge deck cracking shortly after concrete decks are placed and prior to applying traffic loads. Previous researchers have confirmed improper construction practices and design methods can lead to deck cracking. Currently, many contractors throughout Arkansas are using continuous deck pours. This construction approach may restrict the concrete slab from movement during early age shrinkage, causing tensile stresses to develop. The final stresses at the end of construction must be lower than the concrete tensile strength, if not cracking issues will develop. Eventually, these cracks may enlarge due to service load stresses and environmental damage. A nation-wide Department of Transportation (US DOTs) survey was performed to investigate the early age cracking extensiveness level in other state's bridges and what corrections, if any, they have made to address this problem. Additionally, Arkansas bridges with early age cracking were visited to examine any trends and inform instrumentation for bridge testing. A bridge deck was instrumented with 32 vibrating wire strain gauges prior to concrete placement to investigate strain and temperature changes in the first 14 days. Eurocode and ACI approximations for concrete mechanical properties were compared to field measured data for improving the understanding of an early age concrete deck behavior in a continuous steel bridge. Stress analysis study through the span length of bridge 030428 detected some locations prone to concrete cracking due to the variability of concrete mechanical properties and stress developed in the concrete deck. This thesis describes the results of this monitoring and anything that can be learned about formation of concrete stresses in continuous concrete bridge deck pours.
Author: Waleed Khalid Hamid Publisher: ISBN: Category : Bridges Languages : en Pages :
Book Description
The long-term performance of a bridge deck depends on its resistance to bridge cracking. Most of these cracks are initiated at the early age. Early age cracking of bridge decks is a typical issue in the U.S. that reduces bridge service life. Therefore, internally cured concrete (ICC) has been used in some states to reduce or eliminate the development of cracks in reinforced concrete decks. In this study, the early age behavior of ICC deck and the effect of the internal curing on the long-term behavior of the bridge was measured and evaluated in the laboratory and field for newly adjacent constructed bridge, which were located on Route 271 in Mayfield, Ohio. Two different types of concrete mixtures were utilized for the decks: conventional concrete (CC) and internally cured concrete (ICC). Firstly, the ICC and CC mixtures were examined in the laboratory in terms of a mechanical properties test, a plastic shrinkage test, a free shrinkage test, and a restrained shrinkage test. Second, the field behavior of an ICC deck and an adjacent CC deck during their early age and long-term performance were evaluated. Also, the shrinkage development for both decks was examined during the very early age. Instrumentation was used to measure the concrete and reinforcement strains and the temperature in both bridges. The instrumentation and results for both bridges are discussed. Laboratory results indicated that using pre-wetted lightweight concrete in the concrete mixture led to decreased density, coefficient of thermal expansion, and free shrinkage strain, and increased tensile strength and cracking time of concrete compared to conventional concrete. In the field, from the early age test, it was observed that the time to develop concrete shrinkage was approximately 5-6 hours after casting the deck of the ICC and the CC.
Author: Publisher: ISBN: Category : Bridges Languages : en Pages : 182
Book Description
The need to upgrade a large number of understrength and obsolete bridges in the U.S. has been well documented in the literature. Through several Iowa DOT projects, the concept of strengthening simple-span bridges by post-tensioning has been developed. The purpose of the project described in this report was to investigate the use of post-tensioning for strengthening continuous composite bridges. In a previous, successfully completed investigation, the feasibility of strengthening continuous, composite bridges by post-tensioning was demonstrated on a laboratory 1/3-scale-model bridge (3 spans: 41 ft 11 in. x 8 ft 8 in.). This project can thus be considered the implementation phase. The bridge selected for strengthening was in Pocahontas County near Fonda, Iowa, on County Road N28. With finite element analysis, a post-tensioning system was developed that required post-tensioning of the positive moment regions of both the interior and exterior beams. During the summer of 1988, the strengthening system was installed along with instrumentation to determine the bridge's response and behavior. Before and after post-tensioning, the bridge was subjected to truck loading (1 or 2 trucks at various predetermined critical locations) to determine the effectiveness of the strengthening system. The bridge, with the strengthening system in place, was inspected approximately every three months to determine any changes in its appearance or behavior. In 1989, approximately one year after the initial strengthening, the bridge was retested to identify any changes in its behavior. Post-tensioning forces were removed to reveal any losses over the one-year period. Post-tensioning was reapplied to the bridge, and the bridge was tested using the same loading program used in 1988. Except for at a few locations, stresses were reduced in the bridge the desired amount. At a few locations flexural stresses in the steel beams are still above 18 ksi, the allowable inventory stress for A7 steel. Although maximum stresses are above the inventory stress by about 2 ksi, they are about 5 ksi below the allowable operating stress; therefore, the bridge no longer needs to be load-posted.
Author: M. Ala Saadeghvaziri Publisher: ISBN: Category : Concrete bridges Languages : en Pages : 206
Book Description
Many concrete bridge decks develop transverse cracking and most of these cracks develop at early ages, some right after construction and some after the bridge has been opened to traffic for a period of time. Structural design factors have not been the subject of much research in the past and they were the main thrust of this research study. Using 2-D and 3-D linear and nonlinear finite element models many design factors such as girder stiffness, deck thickness, girder spacing, relative stiffness of deck to girder, amount of reinforcements, etc., were studied. The research study also included a comprehensive review of the existing literature as well as survey of 24 bridges in the state of New Jersey. Results of each research task are presented and discussed in detail. Furthermore, based on analytical results and literature review, the effect of various factors are quantified and specific recommendations for possible consideration in design are made.
Author: Federal Highway Federal Highway Administration Publisher: ISBN: Category : Languages : en Pages : 669
Book Description
This manual is intended to serve as a reference. It will provide technical information which will enable Manual users to perform the following activities:Describe typical erection practices for girder bridge superstructures and recognize critical construction stagesDiscuss typical practices for evaluating structural stability of girder bridge superstructures during early stages of erection and throughout bridge constructionExplain the basic concepts of stability and why it is important in bridge erection* Explain common techniques for performing advanced stability analysis along with their advantages and limitationsDescribe how differing construction sequences effect superstructure stabilityBe able to select appropriate loads, load combinations, and load factors for use in analyzing superstructure components during constructionBe able to analyze bridge members at various stages of erection* Develop erection plans that are safe and economical, and know what information is required and should be a part of those plansDescribe the differences between local, member and global (system) stability
Author: Maher K. Tadros Publisher: Transportation Research Board ISBN: 030908766X Category : Technology & Engineering Languages : en Pages : 73
Book Description
"The HCM includes three printed volumes (Volumes 1-3) that can be purchased from the Transportation Research Board in print and electronic formats. Volume 4 is a free online resource that supports the rest of the manual. It includes: Supplemental chapters 25-38, providing additional details of the methodologies described in the Volume 1-3 chapters, example problems, and other resources; A technical reference library providing access to a significant portion of the research supporting HCM methods; Two applications guides demonstrating how the HCM can be applied to planning-level analysis and a variety of traffic operations applications; Interpretations, updates, and errata for the HCM (as they are developed);A discussion forum allowing HCM users to ask questions and collaborate on HCM-related matters; and Notifications of chapter updates, active discussions, and more via an optional e-mail notification feature."--Publisher.
Author: Steven F. Hammerschmidt Publisher: ISBN: Category : Languages : en Pages :
Book Description
With aging and deterioration of bridges, evaluation of existing conditions of their structural elements becomes vital to engineers and public officials when deciding how to repair or replace the structures. The ability to obtain necessary information on these conditions is often expensive and time consuming, especially for concrete bridges where the reinforcement is not available for inspection. Employing the surface-strain relief method could allow for accurate evaluation of aged or damaged prestressed members. The surface-strain relief method was developed to measure initial or pre-existing strains in a concrete member. It involves relieving the strain in the member and measuring the change in strain. Two methods were tested-one used a linear electrical-resistance strain gage and a three-inch-diameter diamond concrete core bit to cut around the gage, and the second method used a laser-speckle imaging device and a diamond cutting wheel to create notches perpendicular to the axis of maximum strain. Both methods measured the change in strain and related it to within 10 percent of the actual fse. The method of cutting notches and the laser-speckle imaging device provided a simpler method to be implemented in the field, while the coring method achieved a higher level of accuracy and precision.
Author: Fernando Rafael Benitez Ortiz
Author: Fernando Rafael Benitez Ortiz
Author: Waleed Khalid Hamid
Author: 
Author: M. Ala Saadeghvaziri
Author: Federal Highway Federal Highway Administration
Author: Maher K. Tadros
Author: Paul D. Krauss
Author: 
Author: Steven F. Hammerschmidt
Author: