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Research Projects (2000-01)

Identifying Number


Project Title

Effects of Environmental Exposure on Timber Railroad Bridge/Track Members and Connectors


Colorado State University

Principal Investigator(s)

Dr. Richard M. Gutkowski
Department of Civil Engineering
Colorado State University
(970)491-8291 or Fax (970)491-2788

Dr. Don Radford
Department of Mechanical Engineering
Colorado State University

External Project Contact

Dr. Shakoor Uppal
Structural Research Engineer
Transportation Test Center, Inc.
Association of American Railroad

Project Objective

The objective is to examine the time dependent mechanical effects of moisture, temperature and humidity on existing and rehabilitated timber railroad bridge and track constructions.

Project Abstract

A series of pilot laboratory tests will be conducted to expose full-size timber Railroad bridge and track members and connections to realistic extremes of temperature and humidity on an accelerated time basis over 6 to 9 months. An existing environmental chamber will be used to subject specimens to controlled levels and ranges of temperature and humidity. Specimens will include connection details typically used in timber railroad bridge and track construction, e.g. the steel rail to wood ties and the wood ties to the chord plies. The condition of wood material will be monitored continuously and effectiveness of the structural connections examined by specimen testing at scheduled times during the simulated exposure periods. Nationally, the structural condition of short span railroad bridges can be characterized as one of increasing concern. Many have been in service for 50-100 years, particularly on short lines in sparsely populated areas. During ser vice life single carloads have increased enormously and the frequency of dual cars has risen dramatically. Reports by the Association of American Railroads (AAR) indicate that degradation has been occurring with material failure evident at some sites. Consequently, existing bridges are being upgraded to more safely carry these increased loads to avoid potential structural problems leading to more costly replacements. Track to wood tie connections also are exposed to such time-dependent environmental degradation, and continual maintenance.

The AAR is involved in a strategic research program to investigate the structural performance of strengthened existing timber trestle bridges via a program of field load tests. Based on the tests on selected bridges to assess the state of strengthened timber railroad bridges, a national plan to upgrade them can be formulated. It is pertinent and important to examine the consequence of upgrades made to b rides comprised of old timbers and the subsequent effects on the environmental climate changes on them. This particularly relates to fastening of new steel or wood components into aged pieces of wood.

CSU has acquired a state-of-the-art ENVIROTONICS walk-in environmental test chamber available to conduct the planned studies. Donated to CSU by Storage Technology, Inc., in Boulder, Colorado, the chamber has been put in place at the Engineering Research Center (ERC) at CSU, where the study will be conducted. The temperature range available is -73C to +85C and can be controlled within +/- 1.1C and transitioned at up to 11 C per hour. The humidity range is 20 % - 95% RH.

CSU will plan the environmental condition test program in con junction with AAR research staff. Specimens will be configured to full-size to represent situations encountered in actual upgrade situations. Over a period of 6-8 months, various extremes of environmental conditions of temperature and humidity encountered in the mountain plains region of the MPC university states and other nearby states will be simulated.

Advice of research scientists in the Atmospheric Sciences Department, located nearby to the ERC will be utilized to determine typical climate conditions. It is expected that annual day-to-day variations and fluctuations of climate conditions can be represented. At selected points in time, specimens that have been sufficiently "conditioned" will be subject to ordinary structural tests (e.g. withdrawal tests of connectors; flexural tests of steel rail to tie to chord ply specimens). These tests will be conducted in the Structural Engineering Laboratory at the ERC, which will also house the environmental chamber.

A two-year project is anticipated. The first yea r is intended as an exploratory project, in which a few selected climate conditions and specimens will be assessed as well as the nature and extent of data to be feasibly obtained in the time period available. An interim MPC report will be prepared. The second year of research will be to extend the pilot studies into comprehensive studies of a broad range of specimen configurations and environmental conditions. A final report will be prepared at the conclusion of the two-year project.

Task Descriptions

The environmental test chamber is physically installed and will be prepared for use and tested for research operation. CSU researchers will communicate with AAR technical staff to determine a 2-3 field construction conditions to be studied as pilot specimen types and to establish controlled environmental conditions and to be used in the chamber. T his will also serve to determine nature and timing the pilot structural tests to be conducted after the specimens have been conditioned in the environmental test chamber. The test specimens will be configured and prepared for conditioning. The pilot experimental test program will be conducted and the resultant data assessed. With AAR input, recommendations for the comprehensive production test program to be conducted in year 2 of the study. This will possibly include alternative connection detailing, if deemed appropriate from the pilot test program. An interim research report will be developed as back-drop for a continuation funding proposal in MPC Year 14.

Milestones, Dates

  • Starting Date: July 1, 2000
  • Completion of physical testing: March 1, 2001
    • Recommendations for Year 2 April 1, 2001
    • Interim Report April 30, 2001
  • Ending Date: June 30, 2001

Yearly and Total Budget

This is a 2-year project. The attached budget is for Year 1 of the project (July 1, 2000-June 30, 2001). The amount requested from USDOT is $32,914 and is augmented by $14,647 as anticipated CSU and external match. The total budget for Year 1 of the project is $47,561. It is expected a total budget of $50,000 will be requested for Year 2 of the project.

Student Involvement

Funds are included for support of a graduate research assistant and hourly student (undergraduate or graduate) labor. It is anticipated a M.S. thesis will result during the second year of the planned project.

Relationship to Other Research Projects

The first PI conducted past MPC projects on field and laboratory of timber trestle bridges. These were done in cooperation with the AAR. Considerable salvage material, wood bridge members, wood ties and some steel rail and connection hardware are salvaged from the laboratory project. Otherwise this is an independent project.

Technology Transfer Attributes

By cooperation with the AAR, the project will produce practical, usable outcomes and the AAR will implement them to improve its timber bridge and track inventory.

Potential Benefits of the Project

This project promotes the maintenance of effective, efficient railroad services to small communities. The AAR is the national industry association representing the numerous member railroads. The research is consistent with a targeted program of research in the AAR to address the state of its timber railroad bridges, nationwide. Concern for viability of the railroad bridges is high as safety issues add to the concerns of a recent history of short line closures. The impact of railroad bridge failures or closures on intermodal freight movement can be devastating to local, state and regional agricultural and freight economies.

By helping to upgrade railroad bridges on main lines and short lines, the programmed research will contribute to the effective transport of agricultural goods and freight throughout the region and country. Without attention to them, some railroad bridges will remain deficient for current loads and others, which are nominally safe will only worsen. The safety concerns are evident as are the potential negative economic consequences of potential railroad bridge closures or, worse, failures. Even one main line bridge failure could be a crisis situation locally and regionally and national fears.

TRB Keywords

Railroads, bridges, track, connections, environmental exposure

NDSU Dept 2880P.O. Box 6050Fargo, ND 58108-6050