Minnesota Department of Transportation

A Minnesota retrofit W-beam guardrail to concrete safety-shaped (Type J) bridge rail transition design with a separate end post was previously crash tested and found to have unsatisfactory impact performance. The design was improved with the addition of a channel rub rail and the improved design was crash tested and evaluated in this study. In accordance with guidelines outlined in NCHRP Report 230, one crash test was conducted on this improved transition design. Results of the crash test indicated that this improved design met all impact performance evaluation criteria as outlined in NCHRP Report 230. This improved transition design is recommended for approval in field applications.

This memorandum supplements the "Structural Study of Existing Lafayette Bridge No. 9800," dated March 1, 2007. The estimates of probable construction costs herein are intended to provide a comparison between the various alignment options and bridge type alternatives for selection of the preferred structure for bridge widening and also to provide information for future funding plans. The estimates are based on estimated quantities and unit price extensions, which will allow for more convenient adjustments to be made in case the planned construction year is modified. The pay quantities should remain fairly constant, whereas the unit prices are subject to a variety of influences that are often difficult to predict. A spreadsheet for each combination of alignment option and bridge type alternative is included in the appendix. These spreadsheets show estimated quantities, unit prices, and cost extensions for the more significant pay items. They also show add-on percentages and costs for minor quantities and staged construction methods under traffic. The adjusted totals have had a contingency percentage added to arrive at the total costs that are stated in the Lafayette Bridge Structural Study report. Backup information providing the basis of the estimated quantities has been provided to Mn/DOT's project manager.

The scope of work for the Lafayette Bridge Study requires the investigation of four bridge widening options. Options are defined in terms of three criteria: horizontal alignment, deck geometry, and whether or not river construction operations (piles footings, pier shafts, cofferdams, etc.) are allowed. The options are named Option 1a, 1b, 2, and 3. The distinguishing characteristics of each option are as follows: • Option 1a: Symmetrical widening about the existing centerline, bridge cross sections meet full geometric standards, foundation work in the river is not allowed. • Option 1b: Symmetrical widening about the existing centerline, bridge cross sections meet full geometric standards, foundation work in the river is allowed. • Option 2: Symmetrical widening about the existing centerline, bridge cross sections do not meet full geometric standards, foundation work in the river is not allowed. • Option 3: Northbound bridge on a new alignment east of the existing bridge, southbound bridge centered on the existing centerline, bridge cross sections meet full geometric standards, foundation work in the river is required.

New bridge decks will be designed to standards which insure a reasonably long maintenance free life. The new bridges have been grouped into three categories with a deck protective system designed to be cost effective for the anticipated exposure to de-icing chemicals in each of these categories.

A task force composed of personnel from the Offices of Bridges and Structures, Materials, Research and Standards has reviewed and analyzed existing procedures for protection of bridge decks. The objectives of the task force were: 1. To develop policy for installation of protective systems on new bridge decks. 2. To develop policy for establishing priorities and selecting methods for contract restoration and protection of in-service bridge decks. 3. To develop policy for systematic maintenance utilizing M.H.D. forces, for the preservation of in-service bridge decks which are not being considered for contract restoration. The objectives were set to protect the bridge deck investment in a cost-effective manner and within budget limitations.

This study was initiated to investigate the possible causes for excessive lamp failure rates on High Mast illumination towers in the State of Minnesota. This type of highway illumination system consists of high masts on which there are either three or four luminaires. The masts are 120 feet (36.6 meters) high and the luminaries are attached to a ring assembly that can be lowered for lamp replacement. The study consisted of two methods of analysis. The first step was to analyze numerically the complete system by employing a finite element code and to compute the motions of the complete system under typical wind conditions at the site (wind velocities between 5 to 60 mph). The second phase of the study consisted of an experimental effort during which one of the illumination towers was instrumented and motion data was collected for various wind conditions. The final phase of the study included the evaluation of the numerical as well as the experimental data that had been obtained from the preceding steps. This evaluation included the identification of modes of vibration in the frequency domain, filtering of data for acescent of modal effects, and comparisons between experimental and numerical results.

In the early 1990s, cities, counties and state agencies (primarily in the Twin City Metro area) experienced rapid growth in radio communications. The increased radio traffic on the public safety systems in the Metro created a severe interference problem among existing users. All FCC radio frequencies within the Metro area were in use, which limited system expansion and, in some cases, prohibited growth of radio systems. Interoperability among public safety agencies was hampered and cumbersome. The 1996 Minnesota Legislature funded the construction of a Metro-wide 800 MHz regional backbone system (Chapter 463, Sec.19, Subd. 3) to meet the demands of the Metro area, and provide capacity for local subsystems to join the network. The implementation of this system is in progress and will be operational in 2002. The problems in Metro are not unique to the area. Outstate public safety communications systems are facing many of the same problems that Metro faced ten years ago. For that reason, the 2000 Legislature directed the commissioners of the departments of Administration, Transportation and Public Safety to convene a planning committee to report to the Legislature on a plan for the development of a statewide, shared public safety radio system. The legislation further directed the planning committee to develop a means to include input from representatives of local governments and major system user groups. As a result of the legislative directive, an 800 MHz Executive Team was formed to study and assess the current and future wireless communication requirements, needs and concerns of the local units of government and major system user groups such as the state of Minnesota, the Emergency Medical Services (EMS) community and school districts.

The Minnesota Department of Transportation has operated permanent continuous weigh-in-motion stations since 1981. At present, 16 sites are collecting volume and weight data by vehicle type for use in transportation planning and design. Questions that can be answered from an analysis of this data can provide useful information. For example, gross weight trends of big trucks in Minnesota have been speculated on with great interest. Are trucks on the highways getting heavier? With a number of years of accumulated data from the first WIM sites and several years from succeeding locations available, we have the means to answer this question.

The graphs and reports in this book depict summaries and totals of the bridges in Minnesota. The five sections to the book are: 1. General information of all bridges. 2. Deficient Structures - 10' to 20' in length. 3. Deficient Structures - 20' and over in length. 4. Replacement program. 5. Trunk Highway bridge performance measures.

The 1994-1995 biennium brought significant changes to the Office of Bridges and Structures. With the office relocation to the Water's Edge Building in Roseville completed, changes to our methods of operation continued. Following the guidance provided by our strategic plan and the encouragement provided by our office Quality Improvement Steering Committee, we continually emphasized quality improvement An office Quality Work-out Session recently provided guidance and continued improvement to overall office operations. Bridge construction program delivery activities were provided at approximately $27,500,000 in Fiscal Year 1994 and $65,000,000 in Fiscal Year 1995 for Trunk Highways, and approximately $18,000,00 per year for county, city, and township projects. Support services were provided for this bridge and highway program in the form of hydraulic direction, structural metals inspection and construction & maintenance assistance. Major accomplishments during the biennium included the implementation of the PONTIS Bridge Management System, the initiation of the VIRTIS Bridge Rating System, initial training for the Load Resistance Factor Design Specifications and completion of the Bridge Aesthetics Design Manual