Effects of Design Parameters on Deck Cracking from Restrained Concrete Shrinkage in Jointless Bridges PDF Download
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Author: David Jonathan Stringer
Publisher:
ISBN: 9781267552112
Category : Bridges
Languages : en
Pages : 245
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Book Description
Author: David Jonathan Stringer
Publisher:
ISBN: 9781267552112
Category : Bridges
Languages : en
Pages : 245
Get Book Here
Book Description
Author: David J. Stringer
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 135
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Book Description
Bridges have traditionally relied on a system of expansion joints and flexible bearings to accommodate movements due to temperature, creep, and shrinkage loading. Joints and elements in their vicinity experience a high amount of degradation; thus modern design approaches are advocating their removal, with movement accommodated through flexible piles and abutment walls. While jointless bridges have been performing well, many of them suffer from widespread early-age transverse deck cracking. Restrained concrete shrinkage was identified as the most dominant source for the noted damage based on a literature review and a field investigation. Deck cracking is caused by the build-up of tensile forces resulting from the increased rigidity in jointless bridges. Experimentally calibrated finite-element models were used to predict deck cracking in two bridge systems under shrinkage-induced loading and a parametric study was conducted to investigate the influence of design parameters on restrained shrinkage cracking. Simulation results confirmed that the increase of system restraint increases the tendency for cracking. Models for steel and concrete beam bridges showed that both systems were equally susceptible to deck cracking due to restrained concrete shrinkage. The lowest amount of cracking was predicted for bridges with non-integral abutments, higher shear connector spacing, and a low-shrinkage concrete mix. Changing the deck reinforcement configuration had little effect on the predicted damage patterns. Use of a low-shrinkage concrete mix had the greatest impact on minimizing deck cracking. Overall, the computational simulations indicated that restrained shrinkage cracking in the decks of jointless bridges is unavoidable, but that modifying design details and improving concrete mixture designs can help reduce its extent.
Author: Robert J. Frosch
Publisher:
ISBN: 9781622601592
Category :
Languages : en
Pages :
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Book Description
Author: Timothy Walkowich
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 107
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Book Description
Over the past decade many state engineers throughout New Jersey have reported cracking on High Performance Concrete (HPC) bridge decks at early ages. The presence of cracking early in the life of a high performance deck offsets the benefits gained in using the material as the potential for corrosion begins at the onset of cracking. While many factors apply to bridge deck cracking, the shrinkage of the concrete's mass is a primary concern. Because of shear studs and boundary conditions, among other causes that act in restraining the deck itself, it is important to understand the mechanics of concrete under restraint. The AASHTO Passive Ring Test (PP 34-06) is seeing an increase in use in studies analyzing restrained shrinkage. The test simulates a concrete member of infinite length and allows researchers to study the effects of various parameters on restrained shrinkage. This thesis presents the results of a study that analyzed the ring test's ability to simulate restrained shrinkage on HPC bridge decks. The investigation incorporated an instrumented, simply supported composite bridge deck with laboratory samples taken on the day of the pour as well as a finite element analysis. The results suggest the AASHTO Passive Ring Test simulates the restrained shrinkage of simply supported HPC decks reasonably well. Fewer than 1% of all cracking present on the ring specimens saw complete penetration through the sample with 80-90% of all cracking considered to be micro cracking. While the presence of several cracks along the bridge deck itself showed no correlation with the shrinkage ring specimens, finite element analysis suggests these cracks are a result of adjacent live load. Also, the findings of this study highlight the importance of following design in the field as well as the effect of live load on staged construction of HPC bridge decks.
Author: Anuoluwa Adediji
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 156
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Book Description
Designers have consistently been concerned with long term deformation of bridges to mitigate unfavorable effects such as excessive movement and cracking. Furthermore, any developed tool of use to a designer must make use of parameters known at the time of design as well as be simplistic in nature as defined in the code. As such, many prediction models for the free shrinkage of a concrete specimen have been developed toward this end. However, structures designed and placed in the field experience shrinkage under restraint. Also, the differences in environmental conditions affect the shrinkage of structures. It is important to understand the restrained shrinkage of structures under field conditions and use this understanding to make improved guidelines on shrinkage from a design standpoint. In this study, the prediction and modelling of the free shrinkage of small samples under constant conditions were expanded to the prediction and modelling of restrained shrinkage under field conditions of large samples using finite element analysis. A parametric analysis was then performed to derive useful information from a design perspective such as the impact of various design parameters on the performance of a bridge deck. The findings indicated that the use of reinforcement is the preferable method of addressing shrinkage in bridge decks. Furthermore, the efficacy of the amount of reinforcement specified in the AASHTO guidelines to mitigate excessive cracking in bridge decks was discussed. The traditional and empirical methods of bridge deck design were investigated for shrinkage reinforcement. Finally, recommendations were suggested to the reinforcement requirements based on the findings of this study.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Ohio Department of Transportation started a program of replacement of bridge decks by high performance concrete decks but the decks started showing cracks after just six to eight months or a season of construction. This study was taken up to ascertain the causes of this early cracking with emphasis on the study of the role of temperature and restrained shrinkage in cracking. Analysis of data from ODOT about its previously cast decks about their location, mix design, slump, compressive strength, average shrinkage, month of casting, ninety day chloride penetration values and temperature differential showed vast scatter, indicating that deck cracking is the compounded effect of several factors acting together and implied an in-depth study in various directions. To gain an insight into the role of temperature and restrained shrinkage in cracking, an experiment was done in an ODOT project involving a phased replacement of deck of a bridge (on US 127) over still water in Richland Township of Darke County in Ohio. Prior to casting, four pairs of vibrating wire gages were placed at the top and bottom of the reinforcement cage of deck at following locations * On the mid-span between two beams * Over the pier * Over the beam * Over the beam pier intersection. Hourly strains and corresponding Temperatures were measured and recorded for fifteen months. Numerical analysis and analytic study was done on the data obtained from site. Both phases of construction showed a different behavior so far as the pattern of strain generation is concerned. It was observed that the gages having least external restraint developed highest strains. The deck showed a wavy behavior with upward curvature at locations where deck had a beam below and downward curvature for locations where deck has no beam (restraint) below it. The temperature was seen to become a potential source for cracking only when a vast difference of temperature existed along the cross section of deck. Even after one year of casting the deck, only minor cracking was observed. This unexpected behavior of deck was attributed to good construction practices, especially proper curing.
Author: Ronald A. Lorini
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 30
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Book Description
Author: Robert J. Frosch
Publisher: Purdue University Press
ISBN: 9781622601080
Category : Transportation
Languages : en
Pages : 178
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Book Description
Transverse cracking of concrete bridge decks is problematic in numerous states. Cracking has been identified in the negative and positive moment regions of bridges and can appear shortly after opening the structure to live loads. To improve the service life of the bridge deck as well as decrease maintenance costs, changes to current construction practices in Indiana are being considered. A typical bridge deck was instrumented which incorporated the following: increased reinforcement amounts, decreasing reinforcement spacing, and high-performance, low-shrinkage concrete. The low shrinkage concrete was achieved using a ternary concrete mix. The objective of this research was to determine the performance, particularly in terms of transverse cracking and shrinkage, of a bridge incorporating design details meant to reduce cracking. Based on measurements from the bridge, it was determined that maximum tensile strains experienced in the concrete were not sufficient to initiate cracking. An on-site inspection was performed to confirm that cracking had not initiated. The data was analyzed and compared with the behavior of a similarly constructed bridge built with nearly identical reinforcing details, but with a more conventional concrete to evaluate the effect of the HPC. Based on this study, it was observed that full-depth transverse cracks did not occur in the structure and that the use of HPC lowered the magnitude of restrained shrinkage strains and resulting tensile stresses.
Author: Eric Simonton
Publisher:
ISBN:
Category : Concrete
Languages : en
Pages : 302
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Book Description
Abstract Shrinkage cracking is reducing the service life of concrete bridge decks in South Dakota due to premature deterioration. In this study, the effects of varying concrete mix design parameters on autogenous and drying shrinkage was observed. Tested mix design changes include aggregate type (limestone and quartzite) and gradations (ASTM C33, Tarantula Curve, and 0.45 Power Curve), supplementary cementitious materials (fly ash), cementitious content, water-to-cementitious ratio, internal curing using saturated lightweight aggregates (expanded shale), and shrinkage reducing admixtures. These changes were evaluated for their effect on the shrinkage of paste, mortar, and concrete as measured by ASTM C1698 (autogenous shrinkage) and ASTM C157 (drying shrinkage). Fresh property tests, compressive strength, and electrical resistivity measurements were performed on each mix as well. A survey of state Department of Transportations revealed the current state-of-the-art practices on shrinkage reduction in bridge decks, including the use of admixtures, internal curing agents, and external curing methods.
Author:
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 64
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Book Description
Early-age cracking, typically caused by drying shrinkage (and often coupled with autogenous and thermal shrinkage), can have several detrimental effects on long-term behavior and durability. Cracking can also provide ingress of water that can drive chemical reactions, such as alkali-silica reaction (ASR) and sulfate attack. Because of the problems associated with cracking observed in bridge decks, and the impact of early-age cracking on long-term performance and durability, it is imperative that bridge decks be constructed with minimal early-age cracking and that exhibit satisfactory long-term performance and durability. To achieve these goals for bridges in the state of Texas, a research team has been assembled that possesses significant expertise and background in cement chemistry, concrete materials and durability, structural performance, computational mechanics (finite difference/element), bridge deck construction and maintenance, monitoring of in-site behavior of field structures, and the development of test methods and specifications aimed at practical implementation by state highway departments. This proposal describes a laboratory- and field-based research program aimed at developing a bridge deck cracking model that will ultimately be integrated into ConcreteWorks, a suite of software programs developed for TxDOT by this same research team.
