The bridge, which connects the cities of Fremont and Menlo Park, was expected to be closed until 5 a.m. this morning but reopened at 3 a.m. instead.
Crews replaced an existing joint on the western side of the 1.6-mile bridge with a newer joint that will absorb and dissipate energy during an earthquake, according to bridge officials.
In addition to the new joint, sections of the bridge were raised by as many as 5 inches during the closure to allow for the installation of seismic bearings over the next few months that will provide independent movement of the bridge deck from its concrete piers, officials said.
Seismic retrofitting of the bridge, which serves as many as 60,000 motorists daily, is expected to be completed by early next year.
Other work was also completed during the closure, including inspections, electrical work, road maintenance, landscaping and at the toll plaza, according to bridge officials.
Bay City News contributed to this report.