Enhanced Camber Calculations for Prestressed Concrete Bridge Girders

The objective of this study was to develop accurate prestressed girder camber calculations and validate them with available data. The project team conducted a thorough literature review and analyzed recent girder camber research efforts in other states. The team collected existing data on 189 Missouri bridge girders as well as field data and cylinder samples from four girders during fabrication. The camber prediction equations and parameters were evaluated and compared to the field data.  

The study found that the current prediction method under-predicted the initial camber measured in the field on average by about 25%. However, investigation also found that the field measurements may have had error due to sag in the measurement string line. It was also found that the effect of the overhang (girder length past storage support locations) affects the camber. Temperature effects were found to be another source of camber error. The current camber calculations were modified to include the effect of the girder overhang and a continuous time-dependent prediction of camber. In addition, guidelines for camber measurement were developed. The modifications to the camber prediction reduced the underprediction of camber to less than 4% on average and decreased the variability to within ±25%. The proposed method was implemented into a computer spreadsheet for easy calculation.

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Report number: cmr 21-011
Published: December 2021
Project number: TR202101
Authors: Dr. Sarah Orton, Dr. Vellore Gopalaratnam, Ali Elawadi, John Holt, Dr. Maria Lopez, Dr. Thomas Murphy

Performing organization: University of Missouri-Columbia

Optimizing Work Zone Zipper Merge Using Federated Driving Simulators

Several departments of transportation have implemented the zipper merge to counter the issues of wasted capacity and queue jumping that surface at early merge work zones. This project researched four issues related to zipper merge operations and offered practical suggestions for the deployment of zipper merge. 

A main result is that public education is vital since many drivers either do not understand zipper merge or are averse to changing from the long-held practice of early merging. Specific recommendations are provided for the deployment of educational materials, including video and written bulletins. 

Drivers prefer for zipper merge to operate under lower traffic speeds and higher traffic flow conditions. However, simulator results show that zipper merge works even under higher speeds and moderate traffic flow conditions. The placement of the last CMS sign in the zipper merge system near the taper is preferred to produce more desirable driver behavior. This placement can be specified in the MoDOT Engineering Policy Guide. The adoption of these recommendation supported by research could improve zipper merge acceptance and operations in Missouri.

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Report number: cmr 21-010
Published: December 2021
Project number: TR202009
Authors: Carlos Sun, Praveen Edara, Sabreena Anowar, and Casey Canfield

Performing organization: University of Missouri-Columbia

Snow and Ice Treatment Products Evaluation

The Missouri Department of Transportation (MoDOT) Maintenance Division uses different materials to reduce the negative impact of snow and ice on the friction performance of state travelways. These materials include abrasives (sand or cinders), rock salt (sodium chloride), and other chemical deicers that emerged in recent years. The use of chemicals and abrasives (in addition to plowing) for highway winter maintenance operations is an essential strategy for ensuring a reasonably high level of service, yet the performance of such materials has to be balanced with their cost effectiveness, and potentially detrimental effects on transportation infrastructure, the natural environment, and motor vehicles. 

Currently, there are considerable data gaps when it comes to the quantification of their performance and impacts and comprehensive assessment for decision making. This study conducted a comprehensive and quantitative evaluation of snow and ice control chemicals currently used by various MoDOT districts for highway maintenance operations based on laboratory tests. An evaluation matrix to assess the cost-effectiveness and potential impacts under a holistic and multi-criteria framework was developed. The results indicated that products #5 (“Clear Lane” Produce), #7 (Calcium Chloride (liquid) Treated Rock Salt) and #3 (“Snow Slicer” Treated Rock Salt) scored above 60 out of 100. Product #5 with a score of 67 is the first priority, then product #7 with a score of 66 is the second priority, and finally product #3 with a score of 64 is the third priority.

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Report number: cmr 21-009
Published: December 2021
Project number: TR202002
Authors: Jenny Liu, Jun Liu, Xianming Shi, and Mehdi Honarvarnazari 

Performing organization: Missouri University of Science & Technology and Washington State University