ANN ARBOR—Motivated by damage to steel-framed structures in such earthquake-prone areas as Turkey, Japan, and California, faculty from the University of Michigan Department of Civil and Environmental Engineering have worked to develop sturdier connections between steel beams and columns. Two designs of connections were recently tested in the Structures Laboratory, and “performed admirably under the most demanding earthquake simulations,” noted Assistant Prof. Bozidar Stojadinovic.
Stojadinovic had previously proven that, when a steel beam is subjected to earthquake conditions, the flow of stress inside the beam near its connection to the column is concentrated toward the beam corners or flanges. This concentration overloads the flanges and causes them to fracture. While the earthquake engineering community was digesting that idea—which was contrary to accepted stress-flow theory—Stojadinovic assembled a team to design new connections that would better withstand seismic attack.
The team’s first concept used a set of cover plates and ribs to strengthen the critical regions of the connection and safely transfer beam forces to the column. The second used an opposite strategy; the beam flanges were deliberately weakened to direct the stress flow away from the most vulnerable regions.
Though different in design, both connections work to the researchers’ satisfaction. Cracking, the plague of old-style connections, was completely eliminated. “We believe that our designs are safe to use in steel buildings built in the most seismically active regions,” said Stojadinovic, “and are working to have them adopted into design codes.”
For more information about earthquake-proof designs for steel-framed structures, contact Stojadinovic at (734) 764-6576. (Photos are available to illustrate this research.) For more information about reinforced concrete structures, contact U-M Prof. James Wight at (734) 763-3046.

Civil and Environmental EngineeringJames Wight