A team from Clemson University, University of Delaware, Honda and Envalior display the Acura MDX door featuring CFRTP components.

Photo Credit: Sai Aditya Pradeep, Clemson University


Scalable ‘Bridge in a Box’

Project: Modular GFRP Pedestrian Bridge

School: West Virginia University

Location: Morgantown, W.Va.

Principal Investigator: P.V. Vijay

Researchers from the West Virginia University Constructed Facilities Center (WVU-CFC) developed a modular GFRP pedestrian “bridge in a box” that can be scaled to span up to 70 feet, easily transported and quickly installed.

Pedestrian bridges are typically constructed with steel and timber, which are susceptible to corrosion and decay and require high levels of maintenance. Recognizing the growing demand for pedestrian bridges, the WVU-CFC team set out to apply decades of experience developing GFRP solutions for the transportation sector to the infrastructure market.

The durability, light weight and strength of GFRP make it ideal for pedestrian bridges. “That’s where FRP plays a strong role. It has all those characteristics and much more,” says P.V. Vijay, principal researcher and associate professor in WVU’s Department of Civil and Environmental Engineering.

Beginning work on the project in early 2021, team members from WVU-CFC and industry partner Bedford Reinforced Plastics Inc. (BRP) wanted to create a modular bridge that could be quickly adapted and installed for different uses, ranging from bridges on remote hiking trails in public parks to ones on top-rated, private golf courses. They designed a truss-style pedestrian bridge made from pultruded parts that are pre-assembled into 5- to 10-foot-wide modules and shipped to the construction site, where they are bolted together to create a longitudinal span up to 70 feet.

All the components are made from GFRP, including beams, decking and the truss structure. The latter comprises hundreds of 2½ x 2½-inch or 3 x 8-inch box sections and 2½ x 10-inch or 2½ x 8-inch channel sections. The parts, which were pultruded by BRP in Bedford, Pa., are joined together using steel bolts and nuts and tightened to a specified torque level. In addition, customers can select wood decking for aesthetic reasons or to reduce construction costs.

After the final bridge in a box concept was developed, researchers constructed a 10-foot-wide, 70-foot-long pedestrian bridge in WVU’s materials and structures laboratories, where it underwent uniformly distributed load and vehicle load testing, dynamic excitation, equivalent wind load and other testing. “We had nearly 100 strain gauges and linear variable differential transformers mounted on the bridge to measure member stresses and deformations,” Vijay recalls. “The whole bridge was instrumented.”

The bridge in a box is now commercially available through Bedford Reinforced Plastics, which has installed more than 20 of the modular pedestrian bridges across the United States.

The initial cost of the GFRP bridge is higher than one constructed with conventional materials. However, the team believes that ease of transportation and installation, along with extended service life, offset those costs. In addition, the low maintenance of the bridges – which are expected to have a life span of 75 to 100 years – provide excellent long-term savings.

A truss-style pedestrian bridge constructed from GFRP pultruded parts that are pre-assembled into 5- to 10-foot-wide modules and bolted together.

Photo Credit: West Virginia University

Melissa O’Leary is a freelance writer in Cleveland. Email comments to melissa@good4you.org.