NU Online News Service, April 27, 2:04 p.m. EDT
Some buildings constructed of reinforced concrete that were at the epicenter of the April 6 earthquake in Italy’s Abruzzo region survived gravitation forces that were off the chart, a survey has found.
That discovery was made by a damage reconnaissance team assembled by the Earthquake Engineering Research Institute and the Pacific Earthquake Engineering Center led by Paolo Bazzurro, AIR Worldwide director of engineering analysis, Boston-based AIR said.
“Several identical six-story reinforced concrete structures built in the late 1980s to early 1990s, which were located at the site where the recording station went off scale at 1g, showed no apparent structural damage, only moderate cracking to the infill walls,” said Mr. Bazzurro.
“A three-story reinforced concrete frame building, which was recently remodeled, located across the street from the recording station remained completely untouched,” he noted.
Mr. Bazzurro said, “This finding will likely prompt thorough investigation in the engineering community to better understand how these buildings could survive relatively unscathed under such severe ground motion.”
The earthquake had magnitude of 6.3 and AIR has estimated that insured losses would range between EUR200 million ($263 million) and EUR400 million ($525 million)–with low penetration of earthquake insurance serving to limit losses to the industry.
AIR estimated damage to buildings and contents (exclusive of infrastructure), or “ground up” loss, at between EUR2 billion ($2.6 billion) and EUR3 billion ($3.9 billion)
Mr. Bazzurro said the quake “was a shallow event, which undoubtedly concentrated the damage in the provincial capital of L’Aquila and surrounding villages. Damage to unreinforced masonry buildings has been severe. Even in cases where a building looks relatively intact from the outside, the inside may reveal severe to total destruction.”
“The large majority of reinforced concrete buildings in the epicentral region fared well, particularly since they were subjected to a ground motion equal to or greater than that for which they were designed,” he added.
These buildings, he explained, were designed for a horizontal acceleration of 0.25g. Mr. Bazzurro said in the epicentral region, maximum gravitational force accelerations up to 0.67g were measured, “and one recording station went off scale at 1g.”
“Among the construction classes, modern reinforced concrete frame buildings–designed after 2003 when the last building code was issued–performed much better than those built in the 1960s through the 1990s,” he reported.
“Modern RC frame buildings typically suffered no exterior damage, or perhaps minor to moderate damage to exterior and interior clay brick partitions. Only very rarely negligible damage was observed to structural elements,” Mr. Bazzurro noted.