MPC
Research Projects (2006-07)

Identifying Number

MPC-275

Project Title

Z-Spike Rejuvenation to Salvage Timber Railroad Bridge Members, Year 1

University

Colorado State University

Project Investigator:

Richard Gutkowski, CSU
gutkowsk@engr.colostate.edu

External Project Contact

N/A

Project Objective

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

Project Abstract

Fiber reinforced composites are extremely popular for infrastructure and in situ infrastructure repair. Common approaches are fiberglass 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 weather exposure. "Shear Spiking" (adapted from "Z-spiking," a construction method used in the aerospace industry) is a viable alternative to the above techniques for application to timber bridge members. Shear spikes are composite rods normally 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. This method does not require member removal and the repair is not exposed to weather. In timber railroad bridges, an added advantage is installation into the top of the members. The intent of this project is to examine the durability of the repair by load testing actual old stringer members to failure after repeated and/or creep loading in a laboratory setting.

Task Descriptions

Past research in related projects (see below) involved load testing tested for flexural stiffness improvement and proved highly successful. These tests will be refined and repeated on the actual damaged timber stringer members. Old salvageable members will be acquired with the assistance of the railroad industry. Each of these will be incrementally reinforced with shear spikes and load tested after each increment of spiking. The final specimen will be tested before and after repeated loading and then loaded to failure. Failure load tests of the comparable non-reinforced specimens will be done as a control comparison.

Milestones, Dates

Starting Date: July 1, 2006
Ending Date: June 30, 2007

Yearly and Total Budget

$54,293

Student Involvement

Two graduate students; one undergraduate student

Relationship to Other Research Projects

A past MPC research project (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 2x4 nominal sizes) and show 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 (MPC Report No. ???) 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. A recent project (MPC Report No. 05-173) shows significant recovery of stiffness is possible for intentionally badly damaged members of timber trestle member chord. These members were newly fabricated members donated by the TransportationTechnology Center, Inc. of the Association of American Railroads for a past MPC project. Additional members with different types of intentional damage are being load tested under initial ramp, repeated loading and failure loading with indications of similar success.

Technology Transfer Activities

In a Transportation Learning Network (TLN) videoconference on the past related projects, DOT participants indicated there are numerous old highway bridges that would benefit from a successful technology. A TLN seminar on all past work was conducted as part of National Transportation Week in 2005. The results of the proposed work will be similarly disseminated in 2007. An MPC technical report will be produced on the conduct and outcomes of the research.

Potential Benefits of the Project

The shear spike result itself is a tangible result of the project. As the shear spikes are made from commercially available rods, easily installed and imbedded in the member, they are invaluable as a low cost, long lasting, repair. In many installations, timber rail road bridges are 50+ year's old but still necessary for daily operation. For rail road bridges 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 aging bridges. 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 researcher will attempt to foster interest in a field pilot project, albeit not included as a known aspect at this time.

TRB Keywords

Fiber Composites, Railroad Bridges, Rejuvenate, Shear Spike, Timber