Parking Garage 093009

Wednesday
10 am

On Wednesday I watched as a steel rebar cage for the new parking garage structure was lifted and set in place. My assumption was that it would simply be lifted and set within a matter of seconds or minutes. The reality was much more involved. Also the crew members and additional equipment was insightful.



Within the steel rebar cage a constellation-like arrangement of bars was located in the center. This I learned was to give the cage stability when going from a horizontal to a vertical position.

A 1-foot portion of the cage had to be to size before it was lifted. A front-end loader was linked to the cut end and used to move scrap to a nearby pile. The loader was repositioned and a chain was used to attach the bottom of the cage to a hook on the loader bucket.

After readjusting the straps which connect to the crane the lift was underway. The loader was used to assist the crane in getting the cage vertical. Once it was vertical and hovering about one foot off the ground, the loader was unchained. Workers then used a torch to remove half of the interior supports. The cage was then lifted to about midway between its lift and final location. Here two workers take what appear to be rigid foam feet to the bottom of the cage. This must provide the required amount of concrete coverage below the cage.

The cage is lifted in to place and lowered to about half way in to the caisson. At this point the cage is held in place while the remaining interior supports are cut and carefully removed so that no rebar fall in to the caisson excavation. With the supports removed the cage is sufficiently flexible and drops right in to place.

I was so impressed with how my assumptions were trumped by the reality of the operation. Last semester we had performed a rough estimate and schedule for caisson work on the new addition to the building department facility. Our estimate focused on the macro estimating and scheduling tasks, but on observing the actual operation I learned the micro-processes. It was a nice reminder that that is what matters. I need to understand the micro-processes in order to truly understand a job. This job is not simply a caisson drill and crane. It is a crew of 8+, a loader, a rebar cage station, drilling spoilage, caisson excavation safety, a welding torch, etc.

Parking Garage 091709

Wednesday
9am
Overcast

Construction has been underway at the new parking garage structure on campus. Just over a month ago an enclosing fence, runoff screen, and trailers were installed around the site. The site itself consists of an existing parking area. Trees and curbs were removed with excavators and dozers. Starting last week the caisson entourage showed up on site. Caissons will vary in size from two to four feet diameters. A crane and a caisson drill have begun drilling at the north west corner of the site. This photo was taken from the balcony of building across from the site.

The above photo shows the ReBar construction area. Workers use this space to build the caisson cages on site. This seems to be a space and labor intensive way to work. What is the cost/benefit of constructing on site as apposed to off-site and transporting it. It may have to do with paying for transportation twice (material to shop, shop to site).

The video shows the movement of the steel from the assembly to temporary storage area.

In observing the caisson drilling rig I noticed a safety cage which encircled the caisson excavation. This safety cage was roughly waist height and obviously meant to protect workers on the ground from falling in to the pit. Today I observed the drill rigs space needs. The caisson drilled is parallel or in-line with the tract. To the left was a spoil pile where the drill would shake loose soil (which appeared to be a shale of some sort) and to the right were some additional bits which could be swapped out when needed.
Note to self: consider safety enclosure for caisson, spoil area, removal of spoil, extra drill bits. Also there appeared to be a barrel of oil on the drilling rig which seemed to allow easy access to the drill apparatus.