The Woolworth Building, Top/Down Construction, & William Starrett

I have passed the Woolworth Building 100+ times in my life. When it was built in 1910, the project was the tallest structure in the world and kept the title for nearly 18 years when it was surpassed by the Bank of Manhattan Trust Building and later dropped to third place by the Empire State Building in 1929. With the 100th anniversary approaching I think that the construction techniques of 1910 were not only impressive for its time, but almost 100 years later are still valid and should be studied by builders.



Persons schooled in architecture and construction are familiar with the basic construction progression of excavation, foundation, substructure, superstructure, and so on up to completion. What struck me when reading The Master Builders (a public-domain book I found on Google Book search) was the innovative method of construction progression used on this project. This project used what is today called Top/Down Construction, but used it 100 years ago to speed the delivery of the excavation, foundation, substructure, and superstructure all at the same time and thus reduce the overall project time.

Excerpts from THE MASTER BUILDERS; by Hugh McAtamney & Co, 1913

BUILDING THE FOUNDATIONS

...the underground work of the Woolworth Building called for the largest single pneumatic caisson contract ever let in New York City or elsewhere. This work consisted of two main items; the sinking of the piers and the deep cellar excavation. Sixty-six reinforced concrete piers from ten to twenty feet in diameter, were sunk approximately one hundred and ten feet deep. They were installed by the pneumatic caisson process, and founded on bed rock. The material penetrated consisted entirely of the most treacherous material known to builders and engineers-quicksand.

... After the piers were completed the erection of the steel work began at once, it being possible to do this because of special cofferdams which had been installed on the tops of the piers. This saved considerable time in the ultimate completion of the building inasmuch as the steel work was not delayed by the general cellar excavation both departments of the construction work being conducted simultaneously.

...this cellar was 55 feet deep. and partly in running quicksand. below water. and that 1.5.000 cubic yards of the quicksand was taken out without interrupting the general work on building. and without jeopardizing the large buildings on all sides the difficulty of the problems will be better understood and the achievement appreciated. This total of the underground work involved an outlay of one million dollars and was accomplished in less than contract time by The Foundation Company of 115 Broadway, New York City.

This project illustrates how Top/Down Construction was executed 100 years ago. First the caissons were drilled. Once they were secured in the bedrock, shoring was installed around the perimeter (although given the contractor, William Starrett, this may have been done at the same time). With the caissons completed structural steel erection could begin. While the steel was moving up, the basement was being excavated.

I cannot describe William Starrett here because I will in no way do him or his career justice. Suffice it to say that William Starrett was the contractor responsible for delivering each of the three tallest structure in Manhattan from 1910 to 1930. These buildings(Woolworth Building, Bank of Manhattan Trust, and Empire State Building) were the World's tallest until the construction of the World Trade Center in 1970, the projects. In addition to these project, Starrett worked for his brother to build the Fuller or Flatiron Building in 1902. So with at least four skyscrapers under his belt it goes without saying that William Starrett deserves some close examination. I have attained a copy of his book 'Skyscrapers and the Men Who Build Them' - 1928 and will eventually post some insights on that text.

To close I want to include a quote from Starretts' Skyscrapers and the Men Who Build Them (1928) which I have taken from editor Carol Lewis' book 'Building the Empire State' (1998):

'Building skyscrapers is the nearest peace-time equivalent of war...The analogy to war is the strife against the elements. ...the service of supply in peace-time warfare, the logistics of building, and these men are soldier of a great creative effort'

Pourous Concrete Test

This video demonstrates the [AWESOME] ability of pourous concrete. Here it is being deluged with water from a concrete mixer. What is so amazing is how quickly it drains through the concrete.

As I watch this questions flood my mind. How deep does this slab have to be to resist uplift? Is there a special method required for the substructure? Are there special rebar requirements, or other installation requirements?



If anyone out there knows of some helpful links, please drop them in the comments section. So far all I have found is this site for pervious concrete paving.

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 092309

Wednesday
12:00 pm
Partly Cloudy

Caisson work is progressing northward. There were an additional two steel workers from the drilling company assembling ReBar. That means that two two-man teams were working simultaneously and within about 15 feet of one another.

The project also presents new insights into building with existing site conditions. The site is a parking lot, which means it is impervious for rainwater. To solve this a drainage pit had to be excavated at the southern end. Also a one-foot berm was created running north-west from the drainage pit. Any water running down over the parking lot is diverted into the pit.

Material storage will be interesting to observe. Once the caisson drilling progresses to the middle of the site, the storage of the caisson sleeves will become an issue that has to be dealt with.

Trailers are all located at the far northern end of the site. Home football game days create traffic congestion so no work is performed on Saturday or Sunday.


In observing a new drainage line that was being installed one can see three pieces of equipment in use. At the far end of the trench an excavator is used to removed the soil. A worker is fitting a drain pipe in a trench barrier. The white machine above the trench is backfilling the trench with stone and soil. In the foreground, one can see a sheepsfoot roller for compaction.



Also got a glimpse of some drainage covers from the Everlasting Vault Company of Randallstown, MD. These vault covers have travelled nearly 300 miles from Maryland to Blacksburg.

More to follow on Wednesday the 30th.

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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.

Site Visit 090709

Monday September 7th, 2009
Partly Cloudy


Construction of new basketball practice facility is complete. Some minor site work is being completed and the construction enclosure has been reduced to a single trailer, parking, and utility hook-up. They appeared to be taking down a notification board. The trailer looked as if they were packing up to move to the next job. There were some excavators at the rear of the site, but that work seemed connected to a new project down the hill.



Below are two photos taken from a similar perspective. The first shows construction in progress in December. The next shows the finished product.

Construction is where the action is. The 'under construction' photo and phase of the basketball facility has so much more going on. Several months ago a crane was in the middle of leveled area of soil. After the rat slab was poured and the metal decking was installed it was used as a large storage area for various trades. Now it serves a single purpose.

Construction in Calabria, Italy (Part Two)

Having travelled to this part of Italy several times since I was 6 years old, this visit to the hilltown of Maiera was different. There is a new project in this sleepy hilltown - a 4-star hotel. The town dates back to the 1100s and the hotel occupies a old palazzo (or palace) which is several hundred years old. The Hotel has four levels. The upper most two will contain rooms with private baths, the second level will hold a restaurant and the first level will have the kitchen. An adjacent building will also have rooms and office space.

Above is the entry to the second level. The scaffolding is set up infront of the entry. A hoist is mounted to the upper portion of the scaffold to assist with material transfer. There is a mortar mixing station on the ground level and the upper level adjacent to the scaffolding.

The metal decking is a modular floring which snaps into place providing flooring, a toe-guard, and an access hatch. There are stairs within the structure, but to access the scaffolding an internal ladder and hatch are used. Inside the building existing floors were reconstructed - terracotta forms the deck and concrete with a steel mesh wire provide the compressive strength.

Walls are composed of terracotta or concrete block. Above is an image showing a concrete block wall with electrical chases installed. To understand the process correctly. A mason lays the block and mortar for the wall. The electrician then comes through and chips aways at the block to insert plastic pipe which forms the conduit chase. Then either the mason or electrician come back through and patch the wall. Eventually which wall will have a stucco finish and no wiring will be seen. The wall does not appear to be load bearing.

With a masonry based system with no false or acoustical ceiling, all conduit is run on the floor. The ridges shown in the photo above are conduit runs along the floor of the upper level. These contain electrical lines. Once the plastic tubes are placed they are covered with concrete. Eventually a topping coat of concrete will be placed to level the floor before tile is placed. When I observed this I couldn't help wonder what it is like to work on this type of surface?

I did not learn to exact finish date or other details of the project. I was mainly trying to understand construction techniques and practices. Another entry will explain some bit of the regulations that were posted and practices I observed.