They don't mention the steel supplier. It was Zhenhua Port Machinery Co., in Shanghai.[1] They usually make port cranes, not bridge parts.
[1] http://www.sacbee.com/news/investigations/bay-bridge/article...
[1] http://www.sacbee.com/news/investigations/bay-bridge/article...
http://www.sfgate.com/bayarea/article/Bay-Bridge-supplier-fa...