MPC
Research Projects (2009-10)

Identifying Number

MPC-328

Project Title

Low-Impact, High-Toughness Transportation Barriers

University

Colorado State University

Project Investigator

Paul Heyliger
E-mail: paul.heyliger@colostate.edu

Description of Project Abstract

The choice of construction materials for any engineering project is quite often a matter of trade-offs. Structural systems that see high use are by necessity designed with this high usage rate in mind when selecting materials so that issues of strength and serviceability are addressed during the design process. However, the cost of some materials continues to increase, and with global competition for finite resources, especially for structural metals, the search for alternative materials has accelerated in recent years.

Structural steel, reinforced concrete, and structural lumber, along with various composite materials, form the basic material library from which designers can select. Yet for specific structural systems, including barriers, safety fencing, and emergency ramps, it is possible to use alternative materials and methods that meet design objectives while lowering cost. Each of these systems is life-saving features of road systems that see a level of use that can vary widely with location. Barriers can be used to divide medians, protect workers, or provide safety along exposed roadways. They can consist of a wide array of structures varying from reinforced concrete to steel cables, and have strength and stiffness levels that vary from outstanding to merely cosmetic. Emergency ramps are also designed to protect life and property, and also have wide-ranging usage. Some of these ramps, including those on high-volume interstates, see very limited use. Others have events several times per month. In all cases, there are a number of design criteria that must be considered when constructing or modifying optimal barriers or escape ramps to ensure driver safety whether it be the truck or collateral vehicles. Most designs are based on slowing down or stopping a vehicle with large mass while minimizing the chances of injury to the driver, damage to the vehicle, and potential for multi-vehicle accidents. At the same time, other considerations such as vehicle recovery, and cost related to the subsequent repair of the damaged (or used) barrier or escape ramp can also have impact.

The proposed work is a continuation of earlier work that has focused primarily on materials that possess both lower stiffness (to soften the blow of impact in case of collision or other contact) but high toughness components that provide an alternative to more common materials. The primary intent has been to focus on new design concepts for roadway barriers and emergency ramps using, for the most part, biomaterials rather than those that require either significant manufacturing effort (metals), long cure times (reinforced concrete), or high cost (many composites). In the first segment of this project, designs of flexible barrier materials gave preliminary estimates of probably ramp/barrier alternatives to existing technologies. These new designs have the advantage of using sustainable materials, providing economically viable alternatives that provide a balance between performance and cost. They provide increased levels of structural toughness while being of a reduced overall stiffness, yielding potentially smaller damage to both the vehicles involved in barrier/ramp use and less likelihood of death or injury.

Our early models have focused on wood-based products, specifically those composed of either lesser known woods (primarily bamboo) or those that are based more on structural fibers. Our initial work has focused on laboratory testing of some of these candidate materials to extract design values for various material candidates. In the next proposed phase of this work, be wishing to perform both physical and numerical testing to place these systems in realistic transportation situations Note: This is to be considered for continuation funding.

Project Objectives

The primary objective of this work is to continue analysis and testing of an alternative classes of materials for use in secondary safety-related transportation structures, including barriers and emergency ramps for the purpose of either modifying existing ramps or use in constructing new ramps in low-use or rural regions.

Our primary intent is to determine, tabulate, and scale an array of materials for use in prototypical systems for eventual physical testing and evaluation for barrier/ramp types of structures.

Project Approach/Methods

The approach taken in this work can be separated into the following basic tasks.

Task a: Alternative Designs: Vertical Barriers and Sequential Webs
Two of the most promising and simple methods that will continue to be explored are what will be referred to as lawnmower-style networks of deformable beams and fibrous networks. Both have been explored as alternatives on firm grade to determine the required material using both synthetic and biomass material candidates. Initial tests of flexible, low-cost, low-diameter bamboo networks show very high promise. In the current year of funding, a guest worker from India along with two students (Ms. Jordan Jarrett of CSU), are working to assess the strength of these sorts of systems and provide assessments of the limits of energy absorbed during vehicle impact (both frontal and side).

Task b: Verification of Selected Designs via Prototype Testing
Testing will be performed to verify the adequacy or alternative ramp and barrier designs. The key variable of interest is momentum; thus a momentum-based similitude approach will be applied to allow scale, e.g. 1/5 scale, testing. These scale prototypes of our design candidates will be constructed and tested at scale using the CSU Vehicle Testing Ramp to determine the true slowing/stopping capacity of the candidate ramp systems. The largest possible vehicle will be used based on the capabilities of the test ramp. This phase of testing was proposed during the last round of funding, but was eliminated during the reduction of final research dollars. We are now in a position to begin conducting such tests.

Task c: Reporting and Design Guidelines
Reporting for this project will consist of the usual written and demonstration efforts as required by MPC.

MPC Critical Issues Addressed by Research

This work addresses USDOT Strategic Goals for Transportation Safety and Security

1) High Risk Rural Roads
5) Low-Cost Safety Improvements
7) Heavy Vehicles and Commercial Trucks
8) Safety of Unpaved Roads.

Contributions/Potential Applications of Research

With the exception of several regional transportation sites that are more specialty based (Motorsport facilities, for the most part), there is a dearth of published data available for barrier design. This is especially true for biomaterials. In addition, most designs of barriers and ramps have been somewhat ad hoc in that a lack of research and analysis of alternatives has led to adoption of known systems that will, for the most part, do the job of slowing down a vehicle with limited injury, damage, and cost. However, there are environments when alternatives should be explored both for the sake of improving existing ramps but also to consider the next generation of these systems that will provide cost and safety benefits to the citizens of MPC states.

Technology Transfer Activities

Competing escape ramp and barrier designs are typically low cost but have varying degrees of success. The design technologies developed in this work will provide real potential for commercial products and adoption by transportation entities.

Time Duration

July 1, 2009 through June 30, 2010

Total Project Cost

$50,150.00

MPC Funds Requested

$22,789.00

TRB Keywords

Barriers, emergency exits, engineering, flexibility, safety, structures.

References

N/A