Microstructural investigation of long-term degradation mechanisms in GFRP dowel bars for jointed concrete pavement

2008 ◽  
Vol 108 (5) ◽  
pp. 3128-3137 ◽  
Author(s):  
Chan-Gi Park ◽  
Chang-Il Jang ◽  
Si-Won Lee ◽  
Jong-Pil Won
Keyword(s):  
Concrete Pavement ◽  
Degradation Mechanisms ◽  
Microstructural Investigation ◽  
Jointed Concrete Pavement

Analysis by High-Speed Profile of Jointed Concrete Pavement Slab Curvatures

2000 ◽  
Vol 1730 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Christopher R. Byrum
Keyword(s):  
High Speed ◽  
Profile Analysis ◽  
Concrete Pavement ◽  
Pavement Management ◽  
Pavement Performance ◽  
Analysis Method ◽  
Pavement Rehabilitation ◽  
Curvature Index ◽  
Jointed Concrete Pavement

A high-speed pavement profile analysis method that detects curvature present in the wheelpaths of jointed concrete pavement slabs is presented. This technique can be used to analyze slab curvatures present in pavements and caused by curling and warping forces. The FHWA Long-Term Pavement Performance (LTPP) program has obtained high-speed elevation profiles for the jointed concrete pavements in the study. This profile analysis method reads an LTPP profile and detects imperfections in the road curvature profile, which typically are joints and cracks. It then analyzes the slab regions (intact slab segments) between these numerical imperfections for the presence of curvature. The result of a profile analysis is a road profile index—the curvature index—which represents the average slab curvature present along the wheelpaths for the profile. This profile analysis method was applied to more than 1,100 LTPP GPS3 profiles. The range of the slab curvatures encountered is described, and some key factors related to apparent locked-in curvatures (related to warping and construction) are discussed. The amount of locked-in curvature in slabs significantly affects slab behavior and long-term pavement performance. Curvature information should be available to pavement rehabilitation engineers making fix type and funding decisions for pavements. This new analysis method could be implemented rapidly in routine pavement profile analysis and pavement management systems.

Influence of Overgrown Micropipes in the Active Area of SiC Schottky Diodes on Long Term Reliability

2005 ◽  
Vol 483-485 ◽  
pp. 925-928 ◽  
Author(s):  
Roland Rupp ◽  
Michael Treu ◽  
Peter Türkes ◽  
H. Beermann ◽  
Thomas Scherg ◽  
...  
Keyword(s):  
Leakage Current ◽  
Power Dissipation ◽  
Schottky Diodes ◽  
Physical Structure ◽  
Active Area ◽  
Clear Correlation ◽  
Local Power ◽  
Degradation Mechanisms ◽  
Failure Simulation

Other than open micropipes (MP), overgrown micropipes do not necessarily lead to a^significantly reduced blocking capability of the affected SiC device. However they can lead to a degradation of the device during operation. In this paper the physical structure of overgrown micropipes will be revealed and their contribution to the leakage current will be shown. The possible impact of the high local power dissipation in the surrounding of the overgrown micropipe will be discussed and long term degradation mechanisms will be described. Failure simulation under laboratory conditions shows a clear correlation between the position of overgrown micropipes and the location of destructive burnt spots.

New Long-Life Concrete Pavements in the Czech Republic

2021 ◽  
Author(s):  
Bohuslav Slánský ◽  
Vit Šmilauer ◽  
Jiří Hlavatý ◽  
Richard Dvořák
Keyword(s):  
Isothermal Calorimetry ◽  
Coupled Model ◽  
Plain Concrete ◽  
Pilot Project ◽  
Economic Benefits ◽  
Concrete Pavement ◽  
Technical Solution ◽  
Concrete Pavements ◽  
Hydration Kinetics

A jointed plain concrete pavement represents a reliable, historically proven technical solution for highly loaded roads, highways, airports and other industrial surfaces. Excellent resistance to permanent deformations (rutting) and also durability and maintenance costs play key roles in assessing the economic benefits, rehabilitation plans, traffic closures, consumption and recycling of materials. In the history of concrete pavement construction, slow-to-normal hardening Portland cement was used in Czechoslovakia during the 1970s-1980s. The pavements are being replaced after 40-50 years of service, mostly due to vertical slab displacements due to missing dowel bars. However, pavements built after 1996 used rapid hardening cements, resulting in long-term surface cracking and decreased durability. In order to build durable concrete pavements, slower hardening slag-blended binders were designed and tested in the restrained ring shrinkage test and in isothermal calorimetry. Corresponding concretes were tested mainly for the compressive/tensile strength evolution and deicing salt-frost scaling to meet current specifications. The pilot project was executed on a 14 km highway, where a unique temperature-strain monitoring system was installed to provide long-term data from the concrete pavement. A thermo-mechanical coupled model served for data validation, showing a beneficial role of slower hydration kinetics. Continuous monitoring interim results at 24 months have revealed small curling induced by drying and the overall small differential shrinkage of the slab.

Development of Some Performance-Based Material Specifications for High-Performance Concrete Pavement

2003 ◽  
Vol 1834 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Prasada Rao Rangaraju
Keyword(s):  
High Performance ◽  
High Performance Concrete ◽  
Concrete Pavement ◽  
Performance Criteria ◽  
Test Results ◽  
Department Of Transportation ◽  
Performance Specifications ◽  
Concrete Materials ◽  
Practical Feasibility

In collaboration with FHWA, the Minnesota Department of Transportation (Mn/DOT) has successfully completed its first experimental high-performance concrete pavement (HPCP) project under the Testing and Evaluation Program (TE-30). This project is one of the 22 projects funded under the TE-30 Program. With a structural design life of 60 years, this HPCP is unique in that it incorporates significant changes to the existing Mn/DOT specifications on concrete materials. Some of the new materials-related specifications developed as a part of this project are based on performance criteria that influence long-term durability of the pavement structure. The background and considerations for selecting the new performance measures are discussed, and test results are presented that evaluate the practical feasibility of establishing and achieving the performance specifications.

Degradation Susceptibility Metrics as the Bases for Bayesian Reliability Models of Aging Passive Components and Long-Term Reactor Risk

2011 ◽  
Author(s):  
Stephen D. Unwin ◽  
Peter P. Lowry ◽  
Michael Y. Toyooka ◽  
Benjamin E. Ford
Keyword(s):  
Passive Component ◽  
Degradation Mechanisms ◽  
Component Reliability ◽  
Passive Components ◽  
Reliability Models ◽  
Age Dependent ◽  
Probabilistic Risk Assessments ◽  
Component Failure Rates ◽  
Service Data

Conventional probabilistic risk assessments (PRAs) are not well-suited to addressing long-term reactor operations. Since passive structures, systems and components are among those for which refurbishment or replacement can be least practical, they might be expected to contribute increasingly to risk in an aging plant. Yet, passives receive limited treatment in PRAs. Furthermore, PRAs produce only snapshots of risk based on the assumption of time-independent component failure rates. This assumption is unlikely to be valid in aging systems. The treatment of aging passive components in PRA does present challenges. First, service data required to quantify component reliability models are sparse, and this problem is exacerbated by the greater data demands of age-dependent reliability models. A compounding factor is that there can be numerous potential degradation mechanisms associated with the materials, design, and operating environment of a given component. This deepens the data problem since the risk-informed management of materials degradation and component aging will demand an understanding of the long-term risk significance of individual degradation mechanisms. In this paper we describe a Bayesian methodology that integrates the metrics of materials degradation susceptibility being developed under the Nuclear Regulatory Commission’s Proactive Materials Degradation Assessment Program with available plant service data to estimate age-dependent passive component reliabilities. Integration of these models into conventional PRA will provide a basis for materials degradation management informed by the predicted long-term operational risk.

Long-Term Operation of BWR RPV and its Internals

2018 ◽  
Author(s):  
Otso Cronvall
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Pilot Project ◽  
Computational Time ◽  
Degradation Mechanisms ◽  
Irradiation Embrittlement ◽  
Screening Process ◽  
Term Operation ◽  
Operational Lifetime

This study concerns the long-term operation (LTO) of a boiling water reactor (BWR) reactor pressure vessel (RPV) and its internals. The main parts of this study are: survey on susceptibility to degradation mechanisms, and computational time limited ageing analyses (TLAAs). The ageing of nuclear power plants (NPPs) emphasises the need to anticipate the possible degradation mechanisms. The BWR survey on susceptibility to these uses the OL1/OL2 RPVs and significant internals as a pilot project. It is not necessary to carry out the TLAAs for all components. Some components were excluded from the TLAAs with a screening process. To do this, it was necessary to determine the component specific load induced stresses, strains and temperature distributions as well as cumulative usage factor (CUF) values. For the screened-in components, the TLAAs covered all significant time dependent degradation mechanisms. These include (but are not limited to): • irradiation embrittlement, • fatigue, • stress corrosion cracking (SCC), and • irradiation accelerated SCC (IASCC). For the components that were screened-in, the potential to brittle, ductile or other degradation was determined. Only some of the most significant cases and results are presented. According to the analysis results, the operational lifetime of the OL1/OL2 RPVs and internals can safely be extended from 40 to 60 years.

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