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California Pacific Medical Center, Pacific Campus
2333 Buchanan St., San Francisco, CA
Contractor:
Otis Elevator Co., Inc.
OSHPD Engineer of Record:
Cammisa and Wipf
Major alteration of four-car group, 10
story passenger elevators. Three were installed in
1972 and the forth car was added in 1982.
New Otis solid state controls,
overhaul existing gearless drive machines, reinforce
existing guide rails.
RCB Elevator Consulting, LLC (RCB) and its associate structural
engineering firm, Eddington Engineering, performed all of
the elevator and building engineering required to make the
conversion. This included performing all field
surveys.
Project Description
The CPMC Pacific Campus is a sizable general acute care
hospital that consists of a number of buildings of differing
age and equipment. Three of the four passenger
elevators were installed in 1972 and the forth car was added
in 1982. The older cars predate the OSHPD structural
standards whereas the forth car was added after OSHPD took
effect. The major alterations were prompted in part
due to the need to update the elevator control systems from
their antiquated relay logic controls and motor-generator
drives to new, solid-state controls and drives. The
other impetus to modernize was the mandate to comply with
SB 1953 and meet the current, more stringent OSHPD
requirements.
RCB Elevator Consulting, LLC and its structural
engineering subcontractor, Eddington Engineering, designed
the structural and seismic anchorage and reinforcing necessary for the
alterations. These included detailed
drawings (see below) and structural calculations as
required for a successful
OSHPD submittal.
Meeting the
SB 1953 requirements for existing structures and
elevator equipment requires an additional step to the
engineering process. Even when as-built drawings of
the original installation are available, they are rarely
detailed enough to provide the information that is needed to
certify compliance with the OSHPD requirements.
Invariably, a comprehensive field survey is required to
reverse engineer all of the structural elements of the
existing installation. This requires knowledge of the
various vintage elevator systems, manufactured components,
original installation practices, etc. as well as building
and structural systems. This survey by RCB is typically
performed by a team of experienced elevator and structural
engineers.
Unlike in new construction conditions, retrofitting
existing elevator installations to reinforce and strengthen
deficient machine anchorages and guide rail systems can
often require unique and inventive solutions.
Practicality and efficiency must play an important role in
the alternation design considering the spatial constraints
and complexity of working in existing, occupied structures -
especially functioning hospitals.
Often the obvious solution to deficient guide rail strength
is for the design to show replacing the rails with new,
heavier rails. This is typically far more
difficult to accomplish considering the likely barriers to
physically maneuvering 16 foot long section of rails into a
finished building. Replacing 8 lb/ft counterweight
guide rails with 15 lb/ft or heavier rails would require
either replacing all of the building support brackets or the
counterweights due to the larger profile dimension of the
heavier rails. Installing complete new guide rails in
completed elevator hoistways begs the question of what to do
with the existing cars and counterweights, which will be in
the way of the work.
However, a more creative solution where the existing
guiderails are retained in place and reinforced can more
safely allow the use of the running car as a hoisting
machine and work platform to accomplish the work. The
guide rail reinforcement and the building support
strengthening are designed uniquely, specifically and
minimally to the exact requirements necessary to meet the
structural and seismic requirements. Through proper
engineering and detailed drafting all of the components
required can be manufactured off-site and delivered to the
job ready for installation. The amount of on-site
welding can be minimized, which is especially desirous in a
functioning health care facility. Many components can
be designed for installation through simple bolting, often
using approved clips - thus avoiding labor intensive on-site
hole drilling. Through such measures, the total work
in labor, materials, expense and equipment downtime can be
reduced substantially.
This project is a very good example, we believe, of the
value of proper engineering. The existing guide rails
were retained and reinforced, including the otherwise
undersized 8 lb/ft counterweight rails. RCB and
Eddington designed a "ladder-type" guide rail reinforcement
consisting of horizontal plates that are attached to the
back of the existing guide rails at prescribed spans via
forged clips and bolts. Onto the back of these plates
are shop welded or bolted vertical structural members.
These members are sized as required to increase the
effective section modulus of the rail to meet the loads
applied, as proven by the engineering. In some
conditions, two structural angles are sufficient and in
others four angles or two channels are required. These
members are spaced sufficiently to permit the replacement of
all of the existing plate-type rail splices with the
code-prescribed full section rail splices. A major
consideration in this job was to design add-on guide rail
reinforcement where there was very little space between the
back of the rail and the building partition wall. Both
for reasons concerning fireproofing and the potential of
existing asbestos, penetrating these walls was to be
avoided. We were able to design in such cases
combinations of vertical structural members that fit the
limited space, yet met the strength requirements.
In summary, projects like the one described require a
combination of hands-on elevator field knowledge and
professional structural engineering to provide efficient and
practical and yet provable design solutions. This is
the forte of RCB Elevator Consulting, LLC working in
conjunction with Eddington Engineering.
If you have an OSHPD or DSA elevator project, feel free
to call.
Pictures
The existing early '80s Otis relay controllers and
motor-generator sets are to be replaced with Otis
solid-state controls and static drives. The anchorage
of the new equipment must meet OSHPD seismic requirements
(see drawings).
The existing gearless traction machines are to be
refurbished. To meet the specific SB 1953 OSHPD
guidelines, the anchorage of the machines and the strength
of the supporting beams must be reverse engineered with
drawings and calculations provided to prove compliance.
These picture shows the original 15 lb/ft car and the 8
lb/ft counterweight guiderails, splice plates and their
building supports. Through reverse engineering the
existing conditions, structural calculations proved the
guide rail stacks to be deficient. RCB with Eddington
have designed creative solutions to reinforce the guide
rails and strengthen the building attachments to meet the
OSHPD requirements
(see drawings).
Drawings & Engineering
Click on the drawing above to open the full drawing set in
PDF format. Note drawings cannot be printed or altered. All
drawings and artwork are the property of RCB Elevator
Consulting, LLC and may not be used, copied, or in anyway
used without the owner's consent.
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CPMC Pacific Campus