Attendees of a recent presentation on the earthquake-resistant structure of San Francisco’s Salesforce Transit Center—intended to provide a safe haven when the Big One hits—lauded the engineering of the 4.5-block-long hollow tube that supports the 1.2-million-sq-ft “groundscraper.” But there also was much talk of the project’s black eye, as a consequence of brittle fractures of the bottom flanges of two bridge-like built-up plate girders that span 87 ft over Fremont Street.

“It’s such a shame about the girders; it’s such a beautiful structure overall,” said one engineer, who declined to be named, after Bruce Gibbons, a managing principal of the hub’s engineer-of-record, Thornton Tomasetti (TT), presented at the American Institute of Steel Construction’s 2019 NASCC: The Steel Conference. The April 3-5 event drew more than 5,100 registrants to St. Louis.