Photo: Jana Asenbrennerova / Special To The Chronicle Photo: Jana Asenbrennerova / Special To The Chronicle Photo: Santiago Mejia / The Chronicle Photo: Jana Asenbrennerova / Special To The Chronicle Photo: Jessica Christian / The Chronicle Photo: Jessica Christian / The Chronicle Photo: Lea Suzuki, The Chronicle Photo: Transbay Joint Powers Authority Photo: Jessica Christian / The Chronicle Photo: Jana Asenbrennerova / Special To The Chronicle

The shutdown of the broken Transbay Transit Center — nearly four months and counting — has delayed bus-riding commuters, closed one of the few parks in a crowded and growing neighborhood, and forced engineers and designers to scramble to reopen the city’s newest landmark.

But the closure also has had one unexpected benefit: Shuttered operations have allowed the Transbay Joint Powers Authority to save about $550,000 each month in reduced operating costs.

The three-block-long transit hub, which is wrapped in a lacy white steel shroud and features a rooftop park and retail center, took eight years to build, cost $2.2 billion and was heralded as “the Grand Central Station of the West Coast.” Just six weeks passed before the discovery of fractures in two critical steel girders forced its immediate evacuation and ongoing shutdown.

Initially, the hope was to reopen within weeks. But the closure has stretched into months — with no date yet scheduled for reopening — and side effects of the closure are emerging. The center has become an inconvenience for neighbors and bus riders, a headache for the authority and an embarrassment to many San Franciscans.

The center costs a little more than $2 million a month to operate. With the shutdown, staffing has been slashed and costs reduced by about 27 percent, according to Martha Velez, a Transbay facility manager.

People who pass by the entrances will find the transit center closed and surrounded with temporary cyclone fencing at its entrances. But some of the lights remain on, escalators and elevators sometimes run and landscaping crews can be seen pruning the gardens and otherwise caring for the 5.3-acre rooftop park.

“There is minimal staffing, but we have to keep operating the center so it’s ready to reopen,” said Christine Falvey, an authority spokeswoman. “We can’t just shut it down for months then turn it back on. We have to maintain it.”

Falvey said the Transbay closure doesn’t involve any city employees because the center and the park are operated by a third party, Lincoln Property Co.

Velez said Muni and AC Transit will get the benefit of the savings, reducing their annual contributions of $2.1 million and $6 million, respectively, toward transit center operations.

Transbay officials say they still don’t know when the center will reopen. But an independent oversight committee has approved a plan to repair the broken support beams. The steel is being fabricated and a date to reopen is likely to be announced in February.

The Metropolitan Transportation Commission assembled the five-person committee of engineers and welding experts to analyze the causes and potential fixes for the cracked girders at the request of San Francisco Mayor London Breed and Oakland Mayor Libby Schaaf. The committee’s assignment has since been expanded to review whether other parts of the structure could also be in danger of steel fractures.

So far, the committee has spent about $550,000, Falvey said.

Meanwhile, the Transbay closure has affected residents of the area, who recently decided to name the district the East Cut, as well as commuters.

During the 44 days the center was open, the 14,500 people who ride AC Transit buses in and out of the transit center each weekday grew accustomed to speedier commutes because Transbay features a buses-only ramp from the Bay Bridge.

The ramp’s closure has forced buses to return to the Temporary Transbay Terminal at Beale and Howard streets, where they went for eight years during the transit center’s construction.

Bus riders say the trip on city streets adds about 10 to 20 minutes depending on traffic, and congestion seems to be growing, said Robert Lyles, an AC Transit spokesman.

“We’re experiencing far more traffic around the terminal,” he said.

Maryclare James, 60, a claims specialist from Alameda, is a leader in People on the Bus, an AC Transit riders group. She said the traffic slowdowns, as well as having to endure rain and wind at the temporary terminal, make it tougher for riders to stomach a recent $1 fare increase blamed in part on the transit center.

“I feel very frustrated,” said James, who’s been riding AC’s buses into San Francisco for 28 years. “A dollar a ride is significant.”

Muni riders have adapted to the return to the temporary terminal, said Paul Rose, a spokesman for the Metropolitan Transportation Commission. However, stops are scattered around the outside of the hub and unprotected from the rains and winds. In the Transbay center, they’re grouped together in a covered area.

Neighbors who live near the transit center are also frustrated. With more buses on the streets, and cars slowing where they pass the Transbay’s temporary shoring on First and Fremont streets, said Andrew Robinson, executive director of the East Cut Community Benefit District.

Most of all, people miss visiting the rooftop park with its gardens, lawn, fountains and entertainment — from yoga and toddler activities to dancing.

In just six weeks, the park had already become a gathering place, Robinson said. Residents keep asking when it will reopen, he said, and hope they can return even while repairs are in progress and the center is braced with temporary supports.

“People are even saying they’ll sign waivers,” Robinson said.

Michael Cabanatuan is a San Francisco Chronicle staff writer. Email: mcabanatuan@sfchronicle.com Twitter: @ctuan