New laminates for old masonry reduce shear

CEE graduate student Reid Senescu monitors the width and extent of the cracks that finally caused the masonry specimen to fail. The shear tests were funded by the NSF, the Hellman Family Faculty Fund, and Sika Corporation. PEG SKORPINSKI PHOTO

A series of preliminary shear tests conducted last spring by a student research team in CEE professor Khalid Mosalam’s structures lab shows that an affordable, transparent fiber-reinforced polymer (FRP) laminate applied to the surface of historic brick buildings could significantly minimize building damage and lives lost in a major earthquake.

Reid Senescu, one of Mosalam’s students on this project, built six masonry test walls — each 2-1/2 feet square — designed to mimic the old brick walls typical of historic buildings and low-cost homes in Third World cities. For these tests, the wall specimens were rotated 45 degrees into a vertical position for mounting inside the compression test machine. "This tilted position makes the shear test easier," said Senescu, "because we are investigating the validity of FRP for multiple-layer masonry walls for the first time."

Each test lasted no more than five minutes, during which the wall was subjected to a vertical load reaching 150,000 pounds — well beyond the load buildings can endure in major earthquakes. The student team varied mortar type and wall thickness, as well as the strength of the FRP laminates in the wall specimens developed in Mosalam's lab.

"It looks like the FRP improved the strength of the walls by as much as 50 percent," said Mosalam, moments after the test. "The amount of deformation in this test was impressive, and this is even more important than the strength gain, because the longer it takes a building to deform before failure, the more warning the people inside have."

Mosalam’s team will conduct more tests this fall, this time with 17-foot-long masonry walls that will be built into large-scale reinforced concrete buildings. The masonry will be tested at the Richmond Field Station shake table and structures lab, where true earthquakes of all magnitudes can be simulated.

"It will be the first time such combined masonry and reinforced concrete structural systems are examined in this way," said the Egyptian native, whose passion for historic buildings has been life-long. "Brick masonry is beautiful. It’s the oldest construction material around, yet it’s the least understood."

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