Research Reports

Driven piles are the most common foundation solution used in bridge construction (Paikowsky et al., 2004). Their safe use requires to reliable verification of their capacity and integrity. Dynamic analyses of driven piles are methods attempting to obtain the static capacity of a pile, utilizing its behavior during driving. Dynamic equations (aka pile driving formulas) are the earliest and simplest forms of dynamic analyses. The development and the examination of such equation tailored for MnDOT demands is presented. In phase I of the study reported by Paikowsky et al. (2009, databases were utilized to investigate previous MnDOT (and other) dynamic formulas and use object oriented programming for linear regression to develop a new formula that was then calibrated for LRFD methodology and evaluated for its performance. This report presents the findings of phase II of the study in which a comprehensive investigation of the Phase I findings were conducted. The studies lead to the development of dynamic formulae suitable for MnDOT foundation practices, its calibrated resistance factors and its application to concrete and timber piles. Phase II of the study also expanded on related issues associated with Wave Equation analyses and static load tests, assisting the MnDOT in establishing requirements and specifications.

With bridge infrastructure in Minnesota aging, advancing techniques for ensuring bridge safety is a fundamental goal of the Minnesota Department of Transportation (MnDOT). As such, developing health monitoring systems for fracture-critical bridges is an essential objective in meeting the stated goal. This report documents the acquisition, testing and installation of a 16-sensor acoustic emission monitoring system in the Cedar Avenue Bridge, which is a fracture-critical tied arch bridge in Burnsville, Minnesota. The overall goal of the project was to demonstrate that acoustic emission technology could be used for global monitoring of fracture-critical steel bridges. Project activities included the acquisition of the monitoring equipment, its testing to verify compliance with manufacturer specifications, installation of the equipment on the selected bridge, field testing to calibrate the system, development of data processing protocols for the acoustic emission (AE) data, and the collection of field data for a period of 22 months. Fracture tests of notched cantilever steel beams were conducted in the laboratory to provide characterization data for fracture events.

This report builds on past efforts to analyze freight mobility and reliability by developing an analysis methodology using GPS data to study freight performance of heavy commercial trucks along 38 key freight corridors in the Twin Cities metropolitan area.

Minnesota counties and the Minnesota Department of Transportation (MnDOT) use the Dynamic Cone Penetrometer (DCP) and the Lightweight Deflectometer (LWD) for in situ evaluation of stiffness and strength of soil and aggregate bases. The in situ test of choice (DCP or LWD) varies somewhat by county and region, depending partly on the local soil conditions and partly on historical preferences. The LWD is considered a measure of modulus while the DCP is considered a measure of shear strength. Recent field and laboratory tests have provided calibration for these tests for several specific granular samples. However, the results are likely less reliable for a broader range of potential granular materials used for granular bases. The objective of this research is to build on a mechanistic model developed for dry aggregate bases under LRRB INV 850 to increase its applicability to more materials and tests used in Minnesota. There were three primary thrusts to these new additions: (1) A model for the LWD test has been added so that computational predictions for DCP tests could be compared with those from LWD tests; (2) Particle-scale models for moisture and fine particle content have been included for the user to input these among the other existing material input parameters, and (3) Analogous algorithms have been developed for the DCP and LWD tests to be used with PFC3D, a commercial code maintained by Itasca Consulting Group.

According to statistics from the Federal Highway Administration (FHWA), each year approximately 17% of all work zone fatalities are pedestrians. People who are visually impaired often encounter physical and information barriers that limit their accessibility and mobility. A survey was conducted among 10 visually impaired participants as a starting point to understand their challenges and what types of information are helpful in providing bypass or routing instructions to them around work zones. The survey results were incorporated into development of guiding documents in determining information elements that are essential and useful for providing routing instructions to the visually impaired around work zones. Building on our previous efforts to provide geometry and signal timing to the visually impaired at signalized intersections, a smartphone-based navigation system was developed and integrated with navigational audible information to alert pedestrians at decision points prior to their arrival at a work zone. The recommended message elements from survey results were implemented in a smartphone app that uses GPS and Bluetooth technologies to determine a user's location. When a work zone is detected, the smartphone will vibrate to alert users and the app will then announce a corresponding audible message to users. The visually impaired users can perform a single tap on the smartphone to repeat the messages, if needed. Functionality testing and system validation of the smartphone app were performed by attaching four Bluetooth beacons to light posts near a construction site in St. Paul, MN. Additional research is needed to conduct experiments with visually impaired users and evaluate system reliability and usefulness.

Researchers at Texas A&M Transportation Institute completed a study of E-Modified, Enhanced E-Modified, and Clearview 5W for overhead and shoulder-mounted guide signs. The overhead guide signs consisted of three 6-letter, 16-inch tall font words stacked over each other at a standard spacing. The test word was on the middle line and had a leading uppercase letter followed by a combination of lowercase ascender and neutral letters, lowercase descender and neutral letters, or all lowercase neutral letters. The word on the top line was "Paying," and the word on the lower line was "Likely." These words were chosen such that the descender and ascender letters encroached on the test words to evaluate the impact of interline spacing. The shoulder-mounted signs consisted of two-digit numbers. Both the word and number legends were chosen to have similar footprints to minimize the likelihood of guessing based on recognition rather than legibility. Legibility distance data were recorded for each word read; however, the researchers completed the analysis based on the legibility index (LI), which is the legibility distance divided by the legend height. A detailed table of previous research is provided in LI values for cross comparison. Similar to previous research, there were mean LI values in some instances for Enhanced E-Modified and Clearview 5W that were larger than E-Modified; however, none of them were statistically significant. The only statistically significant differences reported were with respect to subject age (e.g., 18-35, and 65+) and day versus night, and at night within Clearview 5W with respect to legend type. The mean LI were 68.9 and 45.2 for 18-35 versus 65+ participants in the daytime condition, respectively, and 50.2 and 36.4 for 18-35 versus 65+ participants in the nighttime condition, respectively. It was shown that the cost to implement Clearview 5W would be more expensive than E-Modified, so it was recommended that future research focus on evaluating Clearview 5WR.

The ALERT-2 system was redesigned to mitigate increased roll-throughs. With respect to technological advances, the ALERT-2 system improves many aspects of the basic technologies, providing higher system reliability, easier installation and maintainability, and better self-sustainability through redesign of the renewable energy application. To assess the driver behaviors at the test site, 13 months worth of video data and a survey of local residents were collected. This report describes the system development, implementation, and analysis of the video and survey data.

Cracking of the concrete decks on newly constructed bridges in Minnesota has become a significant concern. Since 2005 MnDOT has been collecting bridge deck construction and early age cracking information on a "Bridge Deck Placement Data Form." The information collected has been entered into a database, along with early age crack surveys, concrete mix design information and concrete testing information. There currently is information on over 120 bridges stored in the database. Crack surveys were performed on 20 of the bridges contained in the database. A statistical analysis of the data, including the updated crack surveys, was performed to determine if there were any relationships between variables collected on the forms and crack frequency, type, or time of development. The analysis showed that, in general, the data collected was not sufficiently consistent to draw significant conclusions. A relationship for temperature restraint cracking for bridges with integral abutments was developed for lineal feet of cracking as a function of bridge deck age, water/cementitious material ratio, and total cementitious content. Recommendations were made for modifications to current construction practices and improving the uniformity of the data collected on the "Bridge Deck Placement Data Form" in the future, so that additional analysis could be performed with more consistent data.

Experiments were conducted to test the feasibility of using the Diamond Wet-Blade mower along roadside right-of-ways. The research conducted compared Canada thistle control, herbicide drift, and operational costs of the Wet- Blade versus broadcast spray application using the herbicide aminopyralid. It was determined that there were no differences between the Wet-Blade and broadcast spraying in terms of Canada thistle control. Herbicide treatments conducted in the spring using at least 88 g ha-1 aminopyralid provided greater than 70% control that lasted for two years after treatment. Broadcast spraying produced detectable drift up to 3 m into non-target areas while the Wet- Blade had negligible drift. Operation of the Wet-Blade is approximately 2 times the cost of broadcast application.

The objective of this investigation was to develop a model to predict on-board sound intensity (OBSI) on hot mix asphalt pavements using on-site and laboratory data. The data used included noise and physical property data collected on 25 asphalt-surfaced roadway test sections at the MnROAD pavement testing facility. These test sections were constructed mainly in 2007 and 2008 using a variety of materials, mixtures and layer thicknesses. A modeling approach called the mechanism decomposition approach was used to develop the models. In this approach, the contributions of different noise mechanisms to the overall noise level and to noise in certain frequency ranges are modeled separately then are combined to form the total noise spectrum. Ultimately, two nonlinear statistical models were developed that predict one-third octave band and overall sound intensity levels on asphalt-surfaced pavements. The models incorporate the pavement parameters that were found to have the most significant effects on tire-pavement noise including pavement macrotexture, air temperature, modulus of the pavement surface layer, and the combined effect of temperature and modulus. The models differ in the type of texture data used as an input parameter. The models have been found to predict the overall OBSI sound intensity level to within 1.5 dB and the onethird octave bands to within 2 dB for most of the pavements tested. Other metrics and evaluation of the model accuracy by cell, year, temperature and other factors are also reported.