MPC
Research Projects (2002-03)

Identifying Number

MPC-216

Project Title

Experimental Thick-Deck Wood-Concrete Highway Bridge Construction, Year 2

University

Colorado State University

Project Investigator

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

Jeno Balogh, Visiting Scientist
Department of Civil Engineering
Colorado State University
(970)491-8524 or Fax (970)491-2788
jbalogh@engr.colostate.edu

External Project Contact

N/A

Project Objective

The objective is to configure and construct a prototype "thick deck" wood-concrete highway bridge and test it to failure in the laboratory.

Project Abstract

Commonly, deteriorating wood bridge decks are completely replaced without consideration of a possible retrofit. This is likely due to lack of potential approaches to strengthen such decks. One approach to strengthening a wood bridge deck is to add a concrete deck layer and interconnect it to the wood deck. A prior MPC project showed this to be successful using a notched shear key/anchor detail tested in the laboratory under static loads. A need exists to examine additional aspects critical to field application. However, the load capacity needed greatly exceeds that of the shorter span applications envisioned in the prior study, resulting in a "thick deck". To proceed to such an application, it is imperative to examine repeated loads and ultimate strength for a "thick deck" as compared to the more slender decks previously examined.

Fundamentally, the thick deck mechanics differ from a thin deck mathematically, too. Extrapolation of the findings for a thin deck specimen to the loads required in the field application is high risk without a study of the underlying mechanics differences.

Task Descriptions

In Year 1, an available test frame was modified to sufficiently and safely apply higher loads. Preliminary to a deck test in Year 2, thick beam specimens were load tested and that is continuing. In Year 2, a full deck test is planned and additional actuator capacity may be needed, including repeated loading and long term loading (creep). These tests will permit verification of the computer simulation for the"thick deck" bridge.

Computer-based structural modeling based on applicable commercial software is being employed to configure the laboratory specimens and predict capacity. A thick deck wood-concrete bridge can possibly be assembled from these salvaged beam specimens. Otherwise, a layered wood-concrete deck bridge will be constructed from new materials.

Milestones, Dates

• Starting Date: July 1, 2002
• Project Milestones:
  • Completion of computer modeling: October 1, 2002
  • Completion of beam tests: October 30, 2002
  • Configuration and testing of a bridge deck specimen: April 1, 2003
  • Comparison of analytical and test results: May 30, 2003
• Ending Date: June 30, 2003

Yearly and Total Budget

This is the second year of a two-year project. The budget is $83,667.

Student Involvement

Two graduate students; one undergraduate student

Relationship to Other Research Projects

A prior MPC project conducted at CSU by the first PI showed the composite wood-concrete system to be mechanically successful in the laboratory under static loads for think deck systems. Thus, it is promising for the thick deck system needed for repetitive HS-20 capacity bridge loadings.

Technology Transfer Activities

Technology transfer will be via an MPC final technical report, a technical journal and/or conference paper submittal each year and an MPC InfoX seminar over the TEL8 telecommunications network after completion of the project. Publicity about all of the MPC projects is available through the MPC web site maintained at NDSU.

If the study is successful, as anticipated, there is a large inventory of deficient bridges available in Region 8 for possible field application. Although not included in this project, the PI will seek to arrange a pilot field test bridge in the future.

Potential Benefits of the Project

The number of deficient bridges in the nation is very high (nearly half of the nation's bridges) and funds to effect repair and replacements are very limited. Thus methods to avoid costly deck replacements and strengthen bridges for today's (and tomorrow's higher) truck loads are economically beneficial.

In the region of the MPC universities, state and local bridges are predominately on secondary roads and are critical to the movement of the vast agricultural and mineral production of the region. The dispersed rural area and low tax base makes saving every possible bridge repair and replacement dollar a critical need.

Typically, decks in older bridges are the first component to wear and exhibit reduced load capacity. As stated above, the usual consequence is the deck is completely replaced with a new one. Otherwise, the bridge using the deck would have to be either posted for lower load limits or closed. The technology being examined in this project has the potential to not only save existing deteriorated wood decks, but to increase the overall bridge load capacity considerably. The resulting additional strength would enable bridge owners to avoid posting and closures in many cases.

If the proposed research is successful, a method for new construction would also result. This cost effective concept also has potential short span access bridges into recreational areas and tourist attractions along secondary and access roads, adjacent to major highways. This project is imperative on a safety basis, to confidently proceed to such applications.

TRB Keywords

Bridges, decks, computer modeling, load tests, wood-concrete