Countdown Church Corner Seismic Strengthening
The works that were carried out to the basement carpark included cutting sections out of the slab and excavating for where the poles and reinforcing cages would be placed. A square 1.2m x 1.2m was cut and excavated with a tie beam strip foundation connecting all in a row. As there were existing columns in the basement, we had to drill through these to run and connect the reinforcing bars. Two types of piles were used, P1 and P2. P1 was an augured hole 1.2m deep x 500mm wide that had a reinforcing cage placed inside and filled with concrete. The P2 plies were a screw pile that was to a depth of around 6m each but weld was 10mm from pile to pile then filled with 30npa concrete. Each pile had to reach loads of Nc=625kN and Nt=359kN. When the piles were completed, we then installed a 250UC to the underside of the existing precast beam, these were cored drilled and cemset with m20 rod. When set, the K Braces were hung off the 250UC, on top of the pile was a base connection with hold down bolts. When all were set, each line was poured in one go so we had no cold joints. A total of 41 P2 piles, 75 P1 piles and 5 grid lines.
To the existing slab to the store we installed 2, 25mm reinforcing bars to 20 dycores in total. These then had to be filled with a high-strength concrete that was pumped from underneath, under pressure to fill the void.
Inside the store, cross bracing and SHS were installed 125EA and 250SHS to seven areas in total.
We also had to install equal angle steel to the precast walls and hollow core floor and the reverb off the drilling was traveling up through the checkouts. To overcome this issue, we met with the store and created a plan where the drilling only took place during times that the store decided were off peak hours.
For the strengthening works to the interior of the store, we had the cross bracing at roof height to install. This had to be managed with great care as the staff restocks the store during the night. During this time, the store had a complete change to the layout of the aisles. A change to the layout meant that a team came into the store and moved stock from one part of the store to another to rebrand and change the layout of the store.
The supermarket continued to operate during the day throughout the works, which meant high-level programming was completed and implemented throughout the duration of the works. We set up hoarding over half of the carpark whilst driving the piles into the concrete, which allowed us to be sectioned off from the public but still allowed the public to access the store from the carpark.