Numerous bolts used to anchor the railing along the bicycle path on the new Bay Bridge eastern span have failed, forcing Caltrans to make plans to replace hundreds of the steel parts, The Chronicle has learned.

Crews that built the railing committed what experts called a basic mistake - they welded the bolts in place firmly in their slots rather than leaving a small amount of room to accommodate a natural expansion of the bicycle path that happens in hot weather.

As a result, scores of the 1-inch-diameter bolts have been sheared off along the 1.2-mile bike path on the southern side of the span's skyway section. All of them, along with hundreds of others that were solidly welded, will have to be inspected and possibly replaced, a Caltrans spokesman said Tuesday.

The problem pales in comparison with the failure of 32 steel rods crucial to seismic-stability structures on the eastern span and questions that have been raised about the soundness of more than 2,300 similar metal fasteners. But it also adds to skepticism about how Caltrans managed construction of the bridge, which is scheduled to open to traffic Sept. 3 - a timetable that is now very much in doubt.

'Serious questions'

"This is not pretty," said Bob Bea, civil engineering professor emeritus at UC Berkeley. "If we are being challenged by straightforward, simple things, it raises serious questions about what we've done on complex situations."

Caltrans officials will update the Metropolitan Transportation Commission on Wednesday about the status of the steel rods. They may also be asked about the problems with the bridge railing, which the agency says it has known about since last year.

Caltrans designers added the bike path to bridge plans in the late 1990s to placate cycling activists. The path will extend from the eastern shore to Yerba Buena Island and is supposed to open in 2015, after the existing eastern span is torn down.

The problem

The path consists of 30-foot segments that are allowed room to move in openings known as expansion joints. The bolts that failed are in the hundreds of 3-foot-long segments of the railing, which link together the 30-foot sections.

The expansion joints allow the segments - steel plates that support a blend of asphalt and polyester - to move slightly as they expand and contract as the weather heats up and cools down.

The 4 1/2-foot-tall railing, painted white like the rest of the span and installed after the skyway was finished in 2008, is held in place by several bolts, which in turn are covered by decorative caps. During inspections in 2012, Caltrans officials say, crews discovered that scores of the bolts had failed under those caps.

The problem is that rather than being allowed to slide in slots in the expansion joints, the bolts had been welded solidly in place. When the weather heated up and the bike-path decks expanded, the bolts sheared off.

Inspect and replace

"It is not a bolt problem," said Caltrans spokesman Will Shuck. "The bolt has to slide free, but the welding prevents it from doing so.

"The caps and welds have to be removed," Shuck said, "and any place where the bolt broke, they have to be replaced."

Every bolt holding the railing in place will have to be inspected, and many are likely to have to be replaced, Shuck said. He didn't have an estimate for how many such bolts are on the span, but conceded the total was at least in the hundreds.

Shuck added, "It will be 100 percent fixed before they open that bicycle path. I'll tell you that much."

He also did not have an estimate for how long it will take to fix the problem or how much it will cost. Whatever the expense, it is likely to be dwarfed by the $10 million fix for the rods that failed on the seismic-stability structures.

Those rods, made of high-strength, galvanized steel, snapped after workers tightened them in March because they had been invaded by hydrogen, which can get into the metal either during the manufacturing process or when the fasteners are exposed to the elements.

Caltrans says it's unclear when the hydrogen invaded the rods, but concedes that the fasteners were made to be harder than those the state allows to be galvanized for typical bridges. Harder metal is more vulnerable to hydrogen after it is galvanized.

A lapse in quality control

Bea said the problem with the bike-path railing amounted to a major lapse of Caltrans' quality control, similar to the problems that have arisen with steel rods.

"Most of these things people do without malice," Bea said. "To these welders, working on the bridge, they figure, 'We better tie these suckers down.' The question is, who is watching the welders?"