MPC
Research Projects (2005-06)

Identifying Number

MPC-261

Project Title

Time-Dependent Loading of Repaired Timber Rail Road Bridge Members

University

Colorado State University

Project Investigators

Dr. Richard Gutkowski
Colorado State University
(970)491-8291
gutkowsk@engr.colostate.edu

Dr. Don Radford
Colorado State University
(970)491-8677

External Project Contact

N/A

Project Objective

The objective is to examine the long term effectiveness and performance of composite shear spikes on full size timber trestle bridge chord members.

Project Abstract

Fiber reinforced composites are extremely popular for infrastructure and in situ infrastructure repair. Common approaches are fiber glass wrap (bandages) or adding reinforcing plates (patches) to the sides of members. These techniques require that the members be removed from the bridge for repair to be made. They also degrade with time due to exposure. "Shear Spiking" is an alternative to these techniques that does not require member removal and is not exposed to weather. Shear spikes are composite rods inserted from the bottom of the member into pre-drilled holes and an injected adhesive bonds them to the wood. They tighten the member to restore overall stiffness and add horizontal shear resistance, among other benefits. The intent of this project is to examine the durability of the repair by testing some of those members as well as some crossties to failure after repeated and/or creep loading and environmental exposure in a laboratory setting.

Task Descriptions

In a past project (see below) a set of timber rail road cross-ties reinforced with shear spikes were tested for flexural stiffness improvement and proved highly successful. A set of these members will be tested under repeated load, and then to failure. In a past project (see below), eight full-scale members of a timber trestle bridge chord are available as salvage. Six of these will be reinforced with larger shear spikes and then tested under creep and/or repeated loading and then to failure. Failure load tests of the comparable unreinforced specimens will be done as a control comparison.

Milestones, Dates

Starting Date: July 1, 2005
Ending Date: June 30, 2006

Yearly and Total Budget

$48,336

Student Involvement

Two graduate research assistants, one undergraduate aide.

Relationship to Other Research Projects

A past MPC project (see MPC Report No. 00-112) explored an innovative alternative to fiberglass wrap and patch repair techniques. A "shear spike" insert approach was tried on small wood members (based on 2x4nominal sizes) and shows promising results. Results of the study show substantial rejuvenation. In some cases repairs to split members resulted in strength and stiffness comparable to undamaged control specimens. A subsequent completed laboratory project addressed application to larger timbers (using rail road ties as a medium with similar encouraging results. Repairs improve stiffness by an average of 58 percent. An ongoing project shows significant recovery of stiffness is possible for intentionally badly damaged members of timber trestle member chord.

Technology Transfer Activities

In a TEL8 teleconference on the past related projects, DOT participants indicated there are numerous old highway bridges that would benefit from a successful technology. A TEL8 teleconference seminar on all past work was conducted as part of National Transportation Week. The results of the proposed work will be similarly disseminated.

Potential Benefits of the Project

In many installation, timber rail road bridges are 50 plus year's old but still necessary for daily operation. For rail road bridges, it is difficult to obtain large size members needed for repair and upgrading. Hence, economic repair of bridges is vital to the nation's infrastructure.. It is critical to maintain safety and economic vitality of rural areas that the transportation infrastructure be safe and long lasting after repairs. This project shows promise of leading to invaluable, affordable technology for repairing aged timber bridges on short and main line railroads and on secondary roads. These vital links for the movement of commodities and other freight often depend on an aging bridges and rails. The research effort will assist the bridge owners by providing a fundamentally new, more structurally effective, substantially low cost alternative to presently limited repair methods based on fiber composites. The researchers will attempt to foster interest in a field pilot project, albeit not included as a known aspect at this time.

The shear spike result itself is a tangible result of the project. As the shear spikes are easily installed and imbedded in the member, they are invaluable as a low cost, long lasting repair. An MPC technical report will be produced on the conduct and outcome of the research.

TRB Keywords

Fiber composites, shear spike, timber bridges, repair