Geogrid inserted between the layers of asphalt pavement during construction can increase the strength and durability of the finished road. To help engineers decide whether to use geogrids in road construction projects, researchers calculated just how much strength and durability geogrid material can add to an asphalt pavement and integrated the findings into MnDOT’s design software.Continue reading Quantifying the Effect of Geogrids in Asphalt Pavement Foundation Layers
MnDOT has upgraded its concrete pavement design software, MnPAVE-Rigid, to make it easier to use and allow more design inputs.
“In the original software, we only allowed one aggregate base thickness and one aggregate type. MnPAVE-Rigid 2.0 allows two base thicknesses and three base types,” said Tim Andersen, Pavement Design Engineer, MnDOT Office of Materials and Road Research.
MnDOT developed its own pavement design software, MnPAVE-Rigid, in 2014 that incorporated the methodology of the American Association of State Highway and Transportation Officials (AASHTO) Mechanistic–Empirical Pavement Design Guide (MEPDG). Minnesota’s pavement designers use MnPAVE to apply AASHTO’s most sophisticated design principles for both rigid and flexible pavement, focusing on mechanical properties of the pavement and prevention of early cracking and other distress.
AASHTO’s mechanistic–empirical (M–E) design methods entail hundreds of inputs, each a mechanical parameter, a measure of site-specific characteristics or a design goal. To simplify the input selection process, AASHTO’s M–E design software offers various input levels to reduce the data gathering and input burden. The most basic level uses default values for most of the inputs based on national averages, but still requires dozens of inputs for the number of pavement layers, traffic expectations, climate and other features.
MnPAVE-Rigid for concrete pavement design reduced that number of inputs to nine, operating like a module of AASHTO’s M–E software. MnPAVE-Rigid inputs work with a set of default values for jointed plain concrete selected by the MnDOT Office of Materials and Road Research in 2014, as described in the MnPAVE-Rigid 1.0 report.
“Many states ignored the challenge of adopting AASHTO M–E or they bought an AASHTO
software license. MnDOT used its accumulated knowledge of AASHTO M–E and Minnesota conditions to build MnPAVE-Rigid, and so can account for its M–E design results firsthand,” said Derek Tompkins, Principal Civil Engineer, American Engineering Testing, Inc.
Since implementing MnPAVE-Rigid 1.0, MnDOT has gathered feedback from users about their experience with the software. In the current project, MnDOT wanted to address this feedback, and expand and improve the original software by exploring additional options with some of the default parameters for concrete pavements.
What Was Our Goal?
The goal of this project was to update MnPAVE-Rigid 1.0 by expanding the range of inputs for traffic, subgrade type, base type and thickness, and to make the user interface more accessible.
What Did We Implement?
MnPAVE-Rigid 2.0 allows users to enter 11 inputs, including inputs related to specific traffic levels and aggregate base types; calculate the new design thickness; and print a project report that summarizes the inputs and the recommended thickness. The upgraded software is more user-friendly, and MnDOT can maintain or make future upgrades to the source code.
How Did We Do It?
Researchers met with the Technical Advisory Panel and reviewed the list of software improvements requested by pavement designers and the MnDOT Office of Materials and Road Research.
Because every change to an input affects a large number of default input variables, investigators ran over 21,000 simulations to analyze the impact of changes made to inputs for base type, base thickness, subgrade type and traffic level. The research team also modified the traffic input calculator to allow designers to enter traffic values from MnDOT’s weigh-in-motion and traffic counting data. The calculator runs input traffic data in software simulations and assigns the input an appropriate axle value for design.
MnPAVE-Rigid 1.0 ran designs based on Class 5 aggregate base over a subgrade like clay loam. Other aggregate types were added to simulations to determine how the software responds to these changes. Investigation also explored the addition of subgrade material options in design simulations.
What Was the Impact?
MnPAVE-Rigid 2.0 is more user-friendly. Its tabs better match designer needs, and the software offers a design report PDF file for export. Instead of selecting from limited options for traffic volumes (default, normal and heavy), users can now input traffic data that the software will categorize. Designers can input Class 5 aggregate, Class 5Q (a higher quality aggregate with fewer fines) and open graded aggregate (no fines). Users can also choose 4-inch or 12-inch aggregate base thicknesses. An additional subgrade option was not included, as simulations indicated a sand subgrade input did not discernibly impact structural thickness outputs.
The AASHTO M–E software is expensive, and agencies that use it have to work closely with consultants to receive training and to explore or modify the code. MnDOT owns and manages the source code for MnPAVE-Rigid 2.0, can keep it secure, and can continue to change and upgrade it internally for Windows and Linux platforms.
The updated MnPAVE-Rigid is now available online. Presentations about the software upgrades will be made at meetings for materials and soils engineers through the fall of 2018.
This Implementation Summary pertains to Report 2018-17, “MnPAVE-Rigid 2.0,” published May 2018.
Minnesota’s transportation research governing boards put a new emphasis on financial benefits when selecting next year’s round of transportation research projects.
MnDOT’s Transportation Research Innovation Group (TRIG) and the Local Road Research Board announced their Fiscal Year 2016 funding awards this week after hearing proposals from researchers in several states. They selected 20 research proposals hall-marked by novel approaches to improving the environment, increasing transportation safety, improving construction methods and boosting the bottom line.
“We asked the principal investigator to present the safety and financial benefits up front, and how they can be implemented to improve the transportation system and economic viability of Minnesota,” said MnDOT Research Management Engineer Hafiz Munir. “We’re making a point early in the process to identify those potential benefits, quantify them and document them in our tracking system.”
Researchers will test new technology that could make crack-free pavements; find better, faster and less expensive ways to reclaim roads; and even explore how to use waste material from road construction projects as part of the landscaping to absorb water runoff.
Links are provided below to brief descriptions of each of the projects:
Bridges and Structures
- Concrete Grinding Residue: Its Effect on Roadside Vegetation and Soil Properties (MnDOT)
- Comparing Properties of Water Absorbing/Filtering Media for Bioslope/Bioswale Design (MnDOT)
- Salt Brine Blending to Optimize Deicing and Anti-Icing Performance and Cost Effectiveness, Phase III (MnDOT)
- Expanding the Success of Salt-Tolerant Roadside Turfgrasses through Innovation and Education (LRRB)
- Pothole Prevention and Innovative Repair (LRRB/MnDOT)
Materials and Construction
- Evaluation of Stabilized Full Depth Reclamation (LRRB/MnDOT)
- MnPAVE-Rigid 2.0 (MnDOT)
- A Mechanistic Design Approach for Novel Graphene Nanoplatelet (GNP) Reinforced Asphalt Pavements for Low Temperature Applications (MnDOT)
- Performance Monitoring of Olmsted County CR 117/104 (MnDOT)
- Slope Stabilization and Repair Solutions for Local Government Engineers (LRRB)
- Life-Cycle Cost Analysis Tool for Minnesota Pavements (LRRB)
- Exploring the Walking Tolerance of Transitway Users (MnDOT)
- Refining Return on Investment Methodology/Tool for MnPASS (MnDOT)
Policy and Planning
- The Futures Project: Planning for Technology Change (LRRB/MnDOT)
Traffic and Safety
- Examining Signing Options for Improving Safe Driving Behaviors in Work Zones (LRRB/MnDOT)
- Assessing the Impact of Pedestrian-Activated Crossing Systems (MnDOT)
- Development of Travel Time Reliability Measurement System (MnDOT)
- Weigh-In-Motion (WIM) Sensor and Controller Operation and Performance Comparison (MnDOT)
- Investigate the Effectiveness of Bluetooth Low Energy (BLE) Technology to Trigger In-Vehicle Messages At Work Zones (MnDOT)