EoW July 2013

Transatlantic Cable

The adaptation “does the trick for galvanising high-strength rods,” a Caltrans engineer told colleagues in April 2003 – an assurance that, ten years later, would prove faulty. In early March, a third of 96 high-strength threaded rods – three inches in diameter and 17 to 24 feet long – broke in key seismic stabilisers on the Bay Bridge span. Ms Vorderbrueggen wrote: “Engineers blame hydrogen embrittlement triggered by the combination of susceptible steel, the presence of hydrogen atoms trapped during galvanising, and the heavy load on the fasteners.” † Caltrans, Bay Area Toll Authority, the bridge contractor, and the team of private engineering consultants hired to design the span are now striving to determine whether a proposed $5 million to $10 million repair job can be nished in time to open the bridge on schedule. Drop in American and European crude steel production is more than o set by higher Asian output, especially in China The most recent data from the Brussels-based World Steel Association showed global crude steel production rising 1.2 per cent in April compared with April 2012, as higher output from Asia – notably China – contrasted with declining output in other major steel producing regions. Worldsteel on 21 st May reported that global production rose to 132.1 million tons in April compared with 130.5 million tons in the same month of last year, while crude steel production in China, the world’s largest steel producer, increased 6.8 per cent year-on-year to 65.7 million tons. Japanese and Indian steel production also rose, 1 per cent and 3.5 per cent, respectively, o setting declines in South Korea and Taiwan. Excluding China, production in the rest of the world declined 3.7 per cent year-on-year in April to 66.5 million tons, according to data from the 63 countries contributing to the report. Worldsteel member-states account for some 85 percent of global steel output. North American crude steel production fell 5.7 per cent year-on-year in April to 10.1 million tons, driven by a 7.3 per cent drop in US crude steel production to 7.3 million tons. South American steel production dropped 3 per cent compared with April 2012, to 3.9 million tons, as Brazilian crude steel production fell 1.6 per cent to 3 million tons. Steel

Bay Bridge’s broken bolts

For the problematic eastern span of the new San Francisco-Oakland Bay Bridge, an elusive x and blame to go around

State senators on 14 th May pressed California Department of Transportation (Caltrans) o cials at a hearing on their plans for dealing with suspect steel parts in the new San Francisco-Oakland Bay Bridge. “I understand that this is a big project, but we seem to have problem after problem after problem,” one of the senators said to Caltrans director Malcolm Dougherty. Whether the bridge will open to public tra c, as planned, on Labor Day (2 nd September), depends heavily on how quickly a retro t can be completed to replace the function of 32 bolts that broke in March after being tightened down by contractors. Caltrans and other agencies have struggled to determine a x for the broken bolts – also known as rods. On 23 rd May, o cials overseeing construction of the bridge presented an update on a plan, previously announced by the toll bridge programme oversight committee, to compensate for the broken bolts by installing large steel saddles over two seismic safety devices on the span. And the o cials themselves received an update: about ongoing testing of the other xtures on the bridge. Reporting from Oakland in the Contra Costa Times (22 nd May), Lisa Vorderbrueggen wrote that the use of large galvanised steel fasteners on a project in 2001 – the retro t of the Richmond-San Rafael bridge – had led engineers to adopt the same speci cations for the bolts that snapped this year on the Bay Bridge. Weakened molecular structure Noting “the well known phenomenon” of weakened molecular structure in high-strength steel coated with zinc, with attendant risk of embrittlement and fractures, Ms Vorderbrueggen wrote, “National standards caution engineers about [the use of galvanisation], and the Caltrans bridge design manual prohibits it on ordinary spans.” Referencing dozens of documents, emails and letters released by Caltrans, the Times reported that – in designing the unique self-anchored suspension span for the Bay Bridge in 2003 – state and private engineers believed that modi cations in steel rod manufacture, developed for the Richmond-San Rafael retro t, would su ciently reduce the risk of hydrogen embrittlement.

Image: www.bigstockphoto.com Photographer Zsolt Ercsel

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July 2013