“They’ve produced a pretty impressive bridge for us,” Tony Anziano, a program manager at the California Department of Transportation, said a few weeks ago. He was touring the 1.2-square-mile manufacturing site that the Chinese company created to do the bridge work. “Four years ago, there were just steel plates here and lots of orange groves.”

On the reputation of showcase projects like Beijing’s Olympic-size airport terminal and the mammoth hydroelectric Three Gorges Dam, Chinese companies have been hired to build copper mines in the Congo, high-speed rail lines in Brazil and huge apartment complexes in Saudi Arabia.

In New York City alone, Chinese companies have won contracts to help renovate the subway system, refurbish the Alexander Hamilton Bridge over the Harlem River and build a new Metro-North train platform near Yankee Stadium. As with the Bay Bridge, American union labor would carry out most of the work done on United States soil.

American steelworker unions have disparaged the Bay Bridge contract by accusing the state of California of sending good jobs overseas and settling for what they deride as poor-quality Chinese steel. Industry groups in the United States and other countries have raised questions about the safety and quality of Chinese workmanship on such projects. Indeed, China has had quality control problems ranging from tainted milk to poorly built schools.

But executives and officials who have awarded the various Chinese contracts say their audits have convinced them of the projects’ engineering integrity. And they note that with the full financial force of the Chinese government behind its infrastructure companies, the monumental scale of the work, and the prices bid, are hard for private industry elsewhere to beat.