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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: Oh-Sung Kwon
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 104
Get Book Here
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: Bala Sivakumar
Publisher: Transportation Research Board
ISBN: 0309098815
Category : Bridges
Languages : en
Pages : 84
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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: Fred Moses
Publisher:
ISBN:
Category : Technology & Engineering
Languages : en
Pages : 68
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Book Description
Author: Bruce R. Ellingwood
Publisher:
ISBN:
Category : Architecture
Languages : en
Pages : 236
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Book Description
Author:
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 336
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Book Description
Author: Richard M. Barker
Publisher: John Wiley & Sons
ISBN: 1118330102
Category : Technology & Engineering
Languages : en
Pages : 1194
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Book Description
Up-to-date coverage of bridge design and analysis revised to reflect the fifth edition of the AASHTO LRFD specifications Design of Highway Bridges, Third Edition offers detailed coverage of engineering basics for the design of short- and medium-span bridges. Revised to conform with the latest fifth edition of the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications, it is an excellent engineering resource for both professionals and students. This updated edition has been reorganized throughout, spreading the material into twenty shorter, more focused chapters that make information even easier to find and navigate. It also features: Expanded coverage of computer modeling, calibration of service limit states, rigid method system analysis, and concrete shear Information on key bridge types, selection principles, and aesthetic issues Dozens of worked problems that allow techniques to be applied to real-world problems and design specifications A new color insert of bridge photographs, including examples of historical and aesthetic significance New coverage of the "green" aspects of recycled steel Selected references for further study From gaining a quick familiarity with the AASHTO LRFD specifications to seeking broader guidance on highway bridge design Design of Highway Bridges is the one-stop, ready reference that puts information at your fingertips, while also serving as an excellent study guide and reference for the U.S. Professional Engineering Examination.
Author: Zuocai Wang
Publisher:
ISBN:
Category : Bridges
Languages : en
Pages : 146
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Book Description
This report summarizes the findings and recommendations on the impact of foundation settlements on the reliability of bridge superstructures. As a collaborative effort of an overall initiative for the development of LRFD foundation design specifications, this study is focused on the investigation of pros and cons for including foundation settlements in bridge designs under gravity loads. Settlement was modeled both probabilistically and deterministically. In the case of a random settlement variable, a lognormal distribution was used in reliability analysis with a fixed coefficient of variation of 0.25. Dead and live loads were modeled as random variables with normal and Gumbel Type I distributions, respectively. Considering the regional traffic condition on Missouri roadways, the effect of a live load reduction factor on bridge reliability was also investigated. Therefore, a total of eight cases were discussed with a complete combination of settlement modeling (mean and extreme values), design consideration (settlements included and excluded), and live load reduction (unreduced and reduced live loads). Based on extensive simulations on multi-span bridges, bridges designed without due consideration on settlements can tolerate an extreme settlement of L/3500 - L/450 under unreduced live loads and up to L/3500 under reduced live loads without resulting in a reliability index below 3.5 (L=span length). Depending upon span lengths settlements and has potential to reduce overall costs in bridge design. The second method may result in oversized foundations.
Author: Peter Frederick Lagasse
Publisher: Transportation Research Board
ISBN: 0309283566
Category : Social Science
Languages : en
Pages : 175
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Book Description
"TRB's National Cooperative Highway Research Program (NCHRP) Report 761: Reference Guide for Applying Risk and Reliability-Based Approaches for Bridge Scour Prediction presents a reference guide designed to help identify and evaluate the uncertainties associated with bridge scour prediction including hydrologic, hydraulic, and model/equation uncertainty. For complex foundation systems and channel conditions, the report includes a step-by-step procedure designed to provide scour factors for site-specific conditions."--Publisher's description.
Author: Hassan Zaghloul
Publisher: Universal-Publishers
ISBN: 1599423979
Category :
Languages : en
Pages : 592
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Book Description
The Arabian Gulf oil and gas production reserves have made it one of the world's strategic producers since the early 1960s, with many of the existing platforms stretched beyond their original design life. Advances in drilling technology and reservoir assessments have extended the requirement for the service life of those existing platforms even further. Extension of the life span of an existing platform requires satisfactory reassessment of its various structural components, including piled foundations. The American Petroleum Institute Recommended Practice 2A (API RP2A) is commonly used in the Arabian Gulf for reassessment of existing platforms. The API guidelines have been developed for conditions in the Gulf of Mexico, the waters off Alaska and the Pacific and Atlantic seaboards of the USA. However, the Arabian Gulf conditions are fundamentally different to those encountered in US waters. Hence, there is a need to develop guidelines for reassessment of existing offshore structures to account for the specific conditions of the Arabian Gulf. This thesis performs statistical analyses on databases collected during this research from existing platforms to calibrate relevant load and resistance factors for the required guidelines. The developed guidelines are based on established approaches used in developing international codes and standards such as API RP2A-LRFD. The outcome of this research revolves around the following three main issues: 1. Calibration of resistance factors for axial capacity of piles driven in the carbonate soils 2. Development of open area live loads (OALL) on offshore platforms 3. Effect of extreme storm conditions on the reliability of existing platforms in the Arabian Gulf The outcomes of this research are expected to have a profound influence onreassessment of existing platforms in the Arabian Gulf.
