Algor Software Enables 19th Century Bridge to Span into the 21st Century

This schematic shows the Wheeling Suspension Bridge, which spans the Ohio river. The bridge was recently analyzed with Algor software.

At the time it was built in 1849, the Wheeling Suspension Bridge, which connects West Virginia to Ohio, was the longest span bridge in the world. Despite the fact that the bridge was not designed to carry today's loads, the bridge has served as a vital link across the Ohio River for nearly a century and a half. With the help of Algor software, it will continue to be useful into the twenty-first century.

An Historic Structure

The Wheeling Suspension Bridge was designed and constructed by Charles Ellet, Jr., who may rightfully be considered the father of the American suspension bridge. Today the 1,100 foot bridge is one of the 57 long span suspension bridges in operation in the United States.

The bridge was modified twice: once in 1956, when a steel deck replaced timber, and again in 1983. Increasing traffic necessitated yet another modification this year.

The West Virginia Department of Transportation contacted Dr. Emory Kemp and Dr. Constantine Spyrakos to conduct testing and finite element analysis on the historic structure. The two West Virginia University professors used Algor software to construct a finite element model of the bridge and conduct linear, nonlinear, modal and response spectrum analyses.

The purpose of these analyses was to assure the safety of the traveling public, taking into account the stress of the traffic volume expected at the turn of the twenty-first century.

Modeling the Structure

Dr. Kemp and Dr. Spyrakos constructed several models based on the bridge's modal testing measurements. They were assisted by graduate student Ramesh Venkatareddy, who is now employed by Kennedy Porter & Associates, Inc.

The finished 3-D model was a compound beam and truss model consisting of 6,906 elements and over 41,000 degrees of freedom.

The Analyses

The first step was to conduct a nonlinear analysis with Accupak. The main cables of the bridge are under tension with stresses that result in large displacements which must first be taken into account.

Several separate analyses were then conducted. The first was a static analysis to determine the stress of traffic over the bridge. The static analysis showed that deflections and stresses caused by present-day loading conditions are within allowable limits under the applicable structural codes.

A modal analysis using Accupak Nonlinear Analysis software to account for the load stiffening effects of the tension forces in the main cables was executed. The results were compared with natural frequencies obtained from modal analysis without consideration of load stiffening to examine whether response spectrum analysis was applicable.

Then, a series of response spectrum analyses were conducted to determine how the bridge would respond to seismic activity.

Seismic analysis using data based on historic earthquakes in the region showed localized damage of floor beams and diagonal floor ties at the east tower and the top chords of the stiffening truss at mid-span. The localized failure in the bridge deck could be avoided through reinforcements.

Since no overstressing was imposed on the main cables and suspenders, catastrophic failure of the bridge due to seismic excitations is highly unlikely.

Dr. Emory Kemp

Dr. Constantine Spyrakos

Putting the Results to Work

Renovations on the Wheeling Suspension Bridge are expected to begin soon. Thanks to FEA, this National Historic Civil Engineering Landmark will continue to be useful in the twenty-first century.