University of Illinois Urbana-Champaign

Illinois-Specific LRFR Live-Load Factors Based on Truck Data

Fu, Gongkang; Chi, Jingya; Wang, Qing

Content Files
FHWA-ICT-19-002.pdf

Permalink

https://hdl.handle.net/2142/103133

Description

Title
Illinois-Specific LRFR Live-Load Factors Based on Truck Data
Author(s)
  • Fu, Gongkang
  • Chi, Jingya
  • Wang, Qing
Issue Date
2019-02
Keyword(s)
  • LRFR
  • bridge
  • load rating
  • live-load factor
  • WIM data
  • simulation
Date of Ingest
2019-03-05T16:33:01Z
Abstract
This research project has a focus on the load and resistance factored rating (LRFR) live-load factors for load rating bridges in Illinois. The study’s objectives were to examine the adequacy of available Illinois weigh-in-motion (WIM) data and to develop refined live-load factors for Illinois LRFR practice, based on recorded truck loads in Illinois. There are currently 20 operating WIM sites in Illinois, each next to a weigh station. Initially, only one WIM site was providing two lanes of truck-weight data simultaneously recorded, while the remaining 19 were collecting data for the driving lane only. Twolane WIM data are important for live-load factor refinement because it is the cluster events involving trucks in different lanes that induce maximum load effects in primary bridge components such as girders. Thus, such data are critical to live-load factors. Upon recommendation from this project, the capability of passing-lane recording was promptly added to two more of the 20 sites. An additional effort was made in this study to simulate the passing lane’s data for the remaining 17 sites, to maximize the use of Illinois-relevant WIM data for covering the entire state. This simulation used the probability of multiple trucks in a cluster, based on WIM data from eight states including Illinois. It also used truck-weight-demography information and headway distances of trucks in cluster from all available Illinois sites. This simulation method was tested and proven in the present project to be reliable for calibration here for Illinois. The resulting truck records of these 17 sites and those recorded at the other 3 sites capable of providing two lanes of truckweight data from 2013 to 2017 were then used to develop refined live-load factors for LRFR in Illinois. Illinois trucks are seen in these WIM data to be less severe than those weighed in Canada, which were used in calibrating the current AASHTO LRFD Bridge Design Specifications (BDS) (2017). Illinois trucks recorded in the WIM data were also found to have behaved with little or no influence from the nearby weigh station. Four load-rating cases are addressed in this project in calibrating LRFR live-load factors for Illinois: design load, legal load, routine-permit load, and special-permit load. Based on calibration using Illinois truckweight records, no change for the design load rating is recommended. Lower live-load factors are recommended for the other three cases for Illinois than those prescribed in the current MBE, by about 8% to 14%, depending on average daily truck traffic (ADTT). Illustrative examples using the recommended live-load factors have been prepared and presented in this report. It is also recommended that Illinois Department of Transportation (IDOT) continue to keep the WIM stations well-maintained, including periodical calibration of the weight sensors and systems; gather more truck-weight-data; review them at least biennially; and focus on possible growth of truck load in both magnitude and volume. When funding becomes available, passinglane recording is recommended to be added to those WIM sites that currently do not have this capability. Truck-data gathering is also recommended for sites where congested truck traffic is often observed, given adequate funding for such facilities.
Publisher
Illinois Center for Transportation/Illinois Department of Transportation
Series/Report Name or Number
FHWA-ICT-19-002
ISSN
0197-9191
Type of Resource
text
Genre of Resource
Technical Report
Language
en
Permalink
http://hdl.handle.net/2142/103133
Sponsor(s)/Grant Number(s)
IDOT-R27-171
Copyright and License Information
No restrictions. This document is available through the National Technical Information Service, Springfield, VA 22161.

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