Calibration of Load Factors for LRFR Bridge Evaluation PDF Download
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Author: Fred Moses
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 68
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Book Description
Author: Fred Moses
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 68
Get Book Here
Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
Author: Fred Moses
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 68
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Book Description
Author: Jordan Michael Pelphrey
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 326
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Book Description
The LRFR Manual, within commentary Article C6.4.4.2.3, contains provisions for development of site-specific live load factors. In Oregon, truck Weigh-in-Motion (WIM) data were used to develop live load factors for use on state-owned bridges. The factors were calibrated using the same statistical methods that were used in the original development of LRFR. This procedure maintains the nationally accepted structural reliability index for evaluation, even though the resulting state-specific live load factors were smaller than the national standard. The first part of this report describes the jurisdictional and enforcement characteristics in the state, the modifications used to described the alongside truck population based on the unique truck permitting conditions in the state, the WIM data filtering, sorting, and quality control, as well as the calibration process, and the computed live load factors. Large WIM data sets from four sites were used in the calibration and included different truck volumes, seasonal and directional variations, and WIM data collection windows. Finally, policy implementation for actual use of the factors and future provisions for maintenance of the factors are described. For bridge rating and evaluation, notional truck models are commonly used to simulate the load effects produced by the truck population. The recently developed Load Resistance and Factor Rating (LRFR) Bridge Evaluation Manual was calibrated based on the 3S2 truck configuration as the notional model. Using GVW as the parameter for establishing live load factors to reflect load effects may not necessarily provide consistent outcomes across all bridge span lengths, indeterminacies, or specific load effects. This is because the load effects are dependent on the distributions of the axle weights, the axle spacing, and the number of axles, in addition to the span geometry and support conditions. The Oregon Department of Transportation currently uses a suite of 13 rating vehicles for evaluation of their bridge inventory. The load effects for Oregon's bridge rating vehicles have also been calculated for various span lengths and support conditions in the second part of this report. These load effects, both unfactored and factored, were compared with load effects calculated using vehicles from large sets of WIM data. Further, because no established standard of time or quantity of WIM data has previously been recognized, a separate study was conducted in order to determine an acceptable window of WIM data. The objective of this analysis was to determine if the load effects and the live load factors developed for bridge rating produced by the suite of vehicles envelope load effects produced by an acceptable window of collected vehicle data for a variety of bridge span lengths and types. Observations and suggestions are made based on the results of these analyses.
Author: American Association of State Highway and Transportation Officials. Subcommittee on Bridges and Structures
Publisher: AASHTO
ISBN: 1560514965
Category : Bridges
Languages : en
Pages : 41
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Book Description
Author: Brandon W. Chavel
Publisher: Government Printing Office
ISBN: 9780160913099
Category : Self-Help
Languages : en
Pages : 130
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Book Description
This Primer serves as an initial resource for planning and performing inspection, metallurgical testing, and strength evaluation of suspension bridge cables. Also provides an example of a simplified strength evaluation, flowcharts illustrating the inspection and strength evaluation procedures, and inspection and strength evaluation forms that can be used, or replicated, by bridge inspectors and engineers. FHWA Publication No. FHWA-IF-11-045.
Author: Oh-Sung Kwon
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 104
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Book Description
The Load and Resistant Factor Design (LRFD) approach is based on the concept of structural reliability. The approach is more rational than the former design approaches such as Load Factor Design or Allowable Stress Design. The LRFD Specification for Bridge Design has been developed through 1990s and 2000s. In the development process, many factors were carefully calibrated such that a structure designed with LRFD can achieve a reliability index of 3.5 for a single bridge girder (probability of failure of about 2 in 10,000). As the initial development of the factors in the LRFD Specification was intended to be applied to the entire nation, state-specific traffic conditions or bridge configuration were not considered in the development process. In addition, due to lack of reliable truck weigh data in the early 1990s in the U.S., the truck weights from Ontario, Canada measured in the 1970s were used for the calibration. Hence, the reliability of bridges designed with the current LRFD specification needs to be evaluated based on the Missouri-specific data and the load factor needs to be re-calibrated for optimal design of bridges. The objective of the study presented in this report is to calibrate the live load factor in the Strength I Limit State in the AASHTO LRFD Bridge Design Specification. The calibration is based on the Missouri-specific data such as typical bridge configurations, traffic volume, and truck weights. The typical bridge configurations and the average daily truck traffic of the bridges in Missouri are identified from statistical analyses of 2007 National Bridge Inventory. The Weigh-In-Motion (WIM) data from 24 WIM stations in Missouri are used to simulate realistic truck loads. Updated material and geometric parameters are also used to update the resistance distributions. From this study, it was found that most representative bridges in Missouri have reliability indices slightly lower than 3.5 mainly due to the adopted projection method to predict 75 year load. For many bridges in rural areas with Average Daily Truck Traffic (ADTT) of 1,000 or less, the average reliability indices are higher than the average reliability index of bridges with ADTT of 5,000. This study proposes a table of calibration factors which can be applied to the current live load factor of 1.75. The calibration factor is developed as a function of ADTT such that bridge design practitioners can select a calibration factor considering the expected ADTTs of a bridge throughout its life span. Impact of the calibration factor on the up-front bridge construction cost is also presented.
Author: Andrzej S. Nowak
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 226
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Book Description
Author: Gongkang Fu
Publisher: John Wiley & Sons
ISBN: 1118329937
Category : Technology & Engineering
Languages : en
Pages : 448
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Book Description
A succinct, real-world approach to complete bridge system design and evaluation Load and Resistance Factor Design (LRFD) and Load and Resistance Factor Rating (LRFR) are design and evaluation methods that have replaced or offered alternatives to other traditional methods as the new standards for designing and load-rating U.S. highway bridges. Bridge Design and Evaluation covers complete bridge systems (substructure and superstructure) in one succinct, manageable package. It presents real-world bridge examples demonstrating both their design and evaluation using LRFD and LRFR. Designed for a 3- to 4-credit undergraduate or graduate-level course, it presents the fundamentals of the topic without expanding needlessly into advanced or specialized topics. Important features include: Exclusive focus on LRFD and LRFR Hundreds of photographs and figures of real bridges to connect the theoretical with the practical Design and evaluation examples from real bridges including actual bridge plans and drawings and design methodologies Numerous exercise problems Specific design for a 3- to 4-credit course at the undergraduate or graduate level The only bridge engineering textbook to cover the important topics of bridge evaluation and rating Bridge Design and Evaluation is the most up-to-date and inclusive introduction available for students in civil engineering specializing in structural and transportation engineering.
