The Metropolis Trust Building San Francisco, California
Unique challenge overcome in busy 110-year-old building
submitted by Rick Nieva, Star Elevator, Inc.
San Francisco’s 15-story Metropolis Trust Building was constructed in 1907 in the wake of the Great 1906 San Francisco Earthquake. Today, it sits among the most expensive real estate in the city. The designated Category 1 Historic Landmark has a vertical-transportation system still anchored in the past, installed more than 100 years ago. It was not operating reliably, and building management was intent on tenant satisfaction, safe operation and improved structural integrity.
Star Elevator, Inc. was tasked with retrofitting machinery to make 21st-century safety concerns meld with the old equipment. The job involved untangling a perplexing crisscross cable gearless basement traction elevator system and converting it into a modern overhead traction variable-frequency-controlled AC gearless system. We completely reengineered the existing offset basement design and added microprocessor AC drives and controllers.
Due to the placement of the machines under the hoistways and the need for proper rope leadoff of the overhead sheaves, the counterweights did not run in the same hoistways as the cars, making for a long, complicated rope scheme. In fact, each car had more than 3/4 mi. of hoist rope. Further complicating matters was the fact that there were no building blueprints available. Thus, Star turned to Rich Blaska of RCB Elevator Consulting, LLC to draw up a detailed plan.
The project included upgrading the rail systems to bring them up to modern seismic code. New push-button and signal fixtures, and modern cab interiors were also added. The focus was on job sequencing and scheduling. It was important to keep the building in operation with an elevator running reliably and safely at all times. The rope configuration made it necessary to shut down two cars at the same time, leaving one car to service the building for months before a modernized car was completed and returned to use.
The building is located on one of the busiest corners in San Francisco, so using cranes was out of the question. Furthermore, the building itself offered limited access: there was no loading dock or service entrance. Thus, all equipment had to enter through the front door. This included 20-ft.-long pieces of reinforcing steel and 4000-lb. gearless hoist machines. The cabs were dismantled to provide a platform so the hoist machines could be brought up through the existing hoistways. The machines were set in position 40 in. above the deck to achieve the proper traction angle on the drive sheaves.
The elevators are now in standard configuration. The new machines are overhead traction, and the counterweights run in the same hoistways as the cars. This layout offers improved long-term safety, reliability, serviceability and speed of the system. Power consumption was reduced 45-50%, and three AC/DC converters were eliminated. The new controls are upgradeable to future standards and can maintain the same elevator configuration, making future modernizations simpler and more straightforward.
- Consultant: JE Sellen Consulting General contractor: Yerba Buena Builders Inc.
- Elevator modernization contractor: Star Elevator, Inc.
- Design, layout and engineering: RCB Elevator Consulting, LLC
- Building property manager: Alhouse Deaton Management
- Building owner: Sun Life Assurance Co.