Details:

Creators:
Kwon, Oh-Sung ; Orton, Sarah ; Salim, Hani ; Kim, Eungsoo ; Hazlett, Tim
Kwon, Oh-Sung ; Orton, Sarah ; Salim, Hani ; Kim, Eungsoo ; Hazlett, Tim Less -
Corporate Creators:
Missouri University of Science and Technology ; University of Missouri--Columbia
Missouri University of Science and Technology ; University of Missouri--Columbia Less -
Subject/TRT Terms:
[+]
Bridges Bridges--Live Loads Bridges--Missouri Calibration Design Load Live Loads Load Factor Load Factor Design Traffic Flow Traffic Volume Trucks--Weight Vehicle Weight Weigh-in-motion Systems Weigh In Motion
Publication/ Report Number:
OR 11 - 003
Resource Type:
Tech Report
Geographical Coverage:
Missouri
Edition:
Final report.
Corporate Publisher:
Missouri. Dept. of Transportation. Organizational Results
Abstract:
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.


Format:
PDF
Funding:
TRyy0913
Collection(s):
US Transportation Collection
Main Document Checksum:
[+]
urn:sha256:66d09cba8f7a088d0936d1cc8686e04e646573b15d419d9331449f3e9231efda
Download URL:
https://rosap.ntl.bts.gov/view/dot/25620/dot_25620_DS1.pdf
File Type:

Supporting Files

• No Additional Files

More +