Up Down Construction

When it came to building the new 50- story, mixed use complex that opened in Chicago in 1992, the engineers, geotechnical consultants, architects and managers overseeing construction were pressed with a 105 million dollar budget and one block of working space. (3) The Chicago Title and Trust Center was built on an old greyhound bus depot that was one block long and was once a 13 story base. (3) This gave the builders a 13-story base and a no-so typical dilemma to overcome. The question was how to build this 1.3 sq ft commercial development with a parking garage that could have a capacity of 130 cars on one block of one of the busiest cities within the continental forty-eight. With typical construction, the below grade section of the structure is built first followed by the construction of the above grade structure. The builders of this Chicago commercial building knew that this would not suffice. The method of up down construction was employed, a construction method that utilizes the ability of the above ground construction to begin before the below ground construction has finished. (3) In the case of the Chicago Title and Trust Center, by the time the sub grade floors had been completed, 20 upper level floors had been built.

In Up Down construction, or commonly known as Top Down Construction, the substructure and the superstructure are built at the same time. The construction begins with the construction of the slurry walls that are built around the building’s foundation. (1,2,3,6) If water is within the slurry walls, the water is removed prior to excavation (6) or during excavation if not present at time of slurry wall construction. The next step in up down construction is the load bearing elements that will carry the superstructure. (6)These elements are created by caisson-auger drilling shafts as deep as the lowest floor and installing steel beams that will be surrounded by rebar or steel cage that will later be filled in with concrete.(1,2) The installation of the columns and foundations is the key to this construction process. (2) The ground floor is next to be formed and poured as it is the reinforcement for the column structure and the upper superstructure construction progress. (1,6) This slab also serves as the reinforcement for the slurry walls and has “glory” holes, or access bays, for equipment and people to move in and out of the basement. (1,6) The work underground is similar to a mining operation, once the first basement floor is poured and cured and “gained sufficient strength” then the excavation of the lower level floor begins. (1,6) “The slab floors are commonly cast-in-place flat slabs or framed slabs. The procedure for forming each of the progressively lower-level slabs has ranged from customary formwork to casting the slab on a mud mat to a drop-form system.” (2) Soil under the top basement floor is excavated around the basement columns to slightly lower than the first basement floor elevation in order to allow for the installation of the forms for the first level basement slab. Glory holes are left open within each newly formed basement floor slab and the procedure is repeated. Each floor rests on the basement columns that were constructed earlier. (6) Once the floor is excavated and the slab is poured and cured, then the work can progress to the lower floors. (1) This excavation/mining work continues until the work has reached the bottom of the lowest level.
 

The Up down construction system has many advantages. Some advantages are the potential cost savings as the price of a temporary support system becomes prohibitive, the technical feasibility as site conditions becomes more complex, and the presence that this method requires no radical changes but rather a resourceful sequencing of proven construction techniques. (2) The up down construction method can eliminate the need for cross cutting or shoring during the excavation process and aside from the obvious simultaneous processes of sub and super structure construction that is a major advantage when dealing with tight capital that leads to significant savings (4), the method allows excavation of the lower level floors in a confined area around the immediate perimeter of the site whereas other conventional methods might disturb neighboring structures. (4) Lastly, another valuable advantage to the up down method of construction is the ability for mostly all trades to begin work at the same time. (3) This last advantage is especially optimistic in the overall work progress of the construction as the trades can work together instead of trying to work around each other’s existing installations. The simultaneous beginning of all trades could also prove useful in the overall construction providing extra communication, understanding between trades, and immediate feedback that may be lacking in more typical types of construction where different trades begin at different intervals throughout the construction process.

As with anything that provides a widespread advantage towards time management, there actually must also be disadvantages. The up down construction method has several disadvantages. Some of the disadvantages are the insufficient outlay information, complicated and unusual construction sequences, and problems that can occur during construction. (5) The top down construction method also is more expensive than conventional construction and does not allow for easy project redesign; project redesign may sometimes be frequently necessary in construction environments where the situation is uncertain. (5) Also, the variables of cost effectiveness and risk factors are not well understood because the method is relatively new in the United States. (5)

In a research paper by Joon H Paek,., and Jong H. Ock about a modified up down construction method, among describing the advantages and disadvantages of the method, such as the disadvantage “ due to innovative combination of heavy construction techniques, there are more potential risks with this method, such as schedule delay from poor planning, unforeseen technical problems, lack of coordination, and unpredictable accidents, than with conventional construction”, the paper provides newer techniques of thought concerning the original up down construction method. The paper presents the up down method in the same way which starts with excavation but instead of slurry wall the authors suggest soldier piles with tiebacks or for the limited space installations a soil-nailing system. The soil nailing system presented in the paper begins with the excavation, then once to the desired depth the temporary stable soil is sprayed with shotcrete then the soil nails are installed connecting to the face wall (5). The next step in the method is the typical foundation column/stem beam installation with cast in place concrete for the foundation. Next, the ground-level floor is installed using composite steel/concrete construction, this floor is utilized as a cross-lot brace. This modified method contrasts the original up down construction the greatest in the last of the sequence where the floors of the substructure are advances upward from the lowest floor rather from top downward.

From the experience in the field, project managers found that the modified up down construction method took typically three to four weeks longer and the cost, although there was less figures, was increase due to the modified method. (5) Since these variables were in place, the authors of the modified method offered a couple motives to use the modified method. The first being that the project’s sub grade levels must be more than 3 levels, second the project must have an adequate number of levels above grade, and last the project must not be in the early stages of design as redesign would offset the time savings.(5) Other variables to consider were: modified approach is more expensive, a larger volume of work is compressed into a short time span, which results in a great deal of site congestion and crowded conditions, access routes would need to be carefully designed, the tieback and soil nailing are not water proof so the conditions would need to be right in the environment.
Although the modified method has many variables to contend with, the method shows considerably more technical feasibility and reduces critical construction time. (5) Contractors may begin to use this technique for frequently as understanding of the modified method increases. (5).

The up down method is a cost, time, and space saving advantage to typical construction sequences.



















Works Cited
Works Cited was numbered in order to protect the paper from excessive citations.
1. "Up-down building technique shaves months from project schedule. " Civil Engineering 70.6 (2000): 31. ABI/INFORM Global. ProQuest. MTSU Library, Murfreesboro, TN. 23 Mar. 2009 http://www.proquest.com/
2. Becker, James M.. . "Building Beneath Boston. " Civil Engineering 61.3 (1991): 66. ABI/INFORM Global. ProQuest. MTSU Library, Murfreesboro, TN 23 Mar. 2009 http://www.proquest.com/
3. Lyons, William T. . "Ups and downs in Chicago. " Civil Engineering 63.12 (1993): 54. ABI/INFORM Global. ProQuest. MTSU Library, Murfreesboro, TN 23 Mar. 2009 http://www.proquest.com/
4. "High Strength High Rise. " Civil Engineering 58.3 (1988): 62. ABI/INFORM Global. ProQuest. MTSU Library, Murfreesboro, TN 23 Mar. 2009 http://www.proquest.com/
5. Paek, Joon H., and Jong H. Ock. "Innovative building construction technique: modified up/down method." Journal of Construction Engineering and Management 122.n2 (June 1996): 141(8). General OneFile. Gale. Middle Tennessee State University. 23 Mar. 2009
<http://find.galegroup.com.ezproxy.mtsu.edu/itx/start.do?prodId=ITOF>.
6. Patsy, Blake D., et al. “Leverage Value from Up-Down Construction”. Construction Issues.11.6(2006): 64. 05 Apr. 2009 http://www.structuremag.com/
7. Deep Excavation, LLC. “SUPPORT SYSTEMS FOR DEEP EXCAVATION”. Top/Down Excavations. 05 Apr. 2009. http://www.deepexcavation.com/supportsystems_topdown.html