How do They do That? — Install the Shear Vertical Pin and Bushing Assembly
This series in “How do They do That?” takes us again to the basement (Level “B”) of the structure where it is cool and dimly lit. Level “B” is where the structural components — Base Isolators and Dampers — for protecting the hospital structures against seismic activity are located and anchored to the foundation floor. At the Loma Linda University Health Campus Transformation Project (LLUHCTP) there are four major elements, noted in this blog,…
…that make up the earthquake protection system. They include: 1) the moat, 2) the foundation, 3) the dampers, and 4) the base isolators. In this blog, I will focus on the base isolator and its components. To put this post into context, we will review the elements of the Base Isolator and how they were assembled.
The Base Isolators became a factor during the foundation rebar installation phase. The pin sleeves were the first units that were set for the Base Isolator. They were embedded in the foundation rebar framework stage, and would be encased in the concrete foundation. The first four pin sleeves were set in the southwest elevator pit on January 31, 2017.
The first four pin sleeves being lowered in the southwest elevator pit.A view from above of the pin sleeves resting on a stabelizing frame.A single pin sleeve (one of four per Isolator) is being moved by a forklift.Four pin sleeves are set on a base before the rebar web surrounds the sleeves.This image illustrates how the pin sleeves look when integrated with rebar (top image), and how they look after the concrete foundation is poured (bottom image). The bottom image is of the four pin sleeves , which are anchored in the concrete of the southwest elevator pit: approximately four-feet below the foundation grade. Foundation concrete is being poured around the Isolator pin sleeves and up to the anchor bolts. Concrete is pumped around the base isolator sleeves during the third and last foundation pour.Between the Rebar: This image illustrates where the isolator pin sleeve sits between the rebar and will be encased in the concrete. The first Base Isolator was set on August 15, 2017The last and largest Base Isolator was set on December 4, 2017 in the northeast corner of the concrete pad.Two vertical isolator pins in a crate. I took this photo because it was interesting thinking I would learn what the contents in the crate were later.Just as I was about to take this photo, a young labor walked up and held onto one of the cylanders, which he later told me was a bushing. I asked what were they for?………. the young man turned and pointed to the above cart. I had to take a second look. He then confirmed that these were the long-awaited vertical pins to be installed in the base isolator sleeves, which were down on Level “B”. The sheer pins had been slipped into the bushings and placed in the cart assembled. These pins are the last non-option-element to complete the vertical isolation system. I later learned that the vertical shear pin and bushing assembly sets were a test to determine the viability of the proposed installation process. One of the transfer carts down on “B” Level where the base isolator is located. The round cylinder on the right side of the cart contains five (5) rubber cushions which are placed inside of the bushing before the vertical shear pin is set.All base isolators are set over the isolator pin sleeves that were installed before the concrete foundation was poured. A bushing (shown in a previous photo) is slipped into a sleeve after which a vertical pin is inserted and bolted to the base isolator. With this system installed on all four corners of each base isolator, they become an integral component in dampening the vertical energy during seismic activity. This image shows one of the pins that has been set. The pin is yet to be bolted to the isolator base. I was unable to document the installation of the test sets. I was assured that I would have time to record the installation at a later date.
The Shear Vertical Pin and Bushing Assembly Installation
The long stick of an excavator is used to lower boxes of Shear vertical Pins and Bushings to Level “B.”Two boxes of vertical shear pins and bushings are assigned to specific Base Isolators. In this image a laborer delivers a box to its designated Isolator. The bottom of the Base Isolator sleeve that was encased in the foundation. The depth of the sleeve is approximately 30 inches from grade and 37 inches from the flange where the top of the pin will be bolted. Preparing the bushing to be lowered into the sleeve. The laborer usually wears his hat, but it fell off while working with the bushing.A bushing is being lowered into a sleeve.Two of the five (5) shear vertical pin cushins are being lowered into the bushing. The cushins will be firmly pressed down in the busshing untill they rest on the bottom of the sleeve. A rubber gasket is carefully lowered over the ten (10) nelson type threaded studs to which the vertical shear pin cap will be anchored with ten (10) threaded nuts.A telescoping gantry with a remote operated electric hoist is moved over the wooden custom adjustable pallet that was fabricated to hold four vertical shear pins. Note the electrical conduits at the top of the image with wire pull cords hanging from the ends.Once the hoist hooked through the pin’s eye hook, the upper and lower segments of the adjustable pallet supporting the vertical shear pin will be removed to allow the hoist to remove the 850 pound pin from the cart.With the Shear Vertical Pin and Bushing Assembly now set another significant and final piece of the Base Isolator system is complete. Upon completing this installation, one of the installers quipped “another 499 sets to go.”
After graduate school Dennis accepted a position at Loma Linda University. He worked there for 42 years in the areas of administration and financial management, also teaching accounting and management to dietetic students at the School of Public Health. Through the years Dennis has chronicled the growth of the campus, including the construction of the Drayson Center and the Centennial Complex and the razing of Gentry Gym. He is the author of "The Mound City Chronicles: A Pictorial History of Loma Linda University, A Health Sciences Institution 1905 - 2005." dEp 09.30.2016 🔨
