AT&T Corporate Center Integrated Design CASE Study

Comprehensive & Accentuated Simulated Experience Report

AT&T Corporate Center

227 West Monroe Street Chicago, IL Architect: Skidmore, Owings, & Merrill Developer: Stein & Co. ARCH 544: Integrative Design of Buildings

Becky Chen, Beth Nowicke, Dorian Janowicz, Francia Flores

Table of Contents

Table of Contents Acknowledgements and Preface .

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Chapter 1 Building Overview

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1 - 12

Chapter 2/3 . . . . . . . .

Enclosure System: Conventional Wall System, Curtian Wall System

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13 - 22

Chapter 4 . .

Structural System: Substructure

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23 - 34

Chapter 5 . .

Structural System: Superstructure

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35 - 44

Chapter 6 . .

Mechanical System Organization

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45- 48

Chapter 7 Space Conditioning

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49 - 54

Chapter 8 Electrical System

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55 - 58

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59

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Reflections on Design Integration .

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Introduction

Acknowledgements + Preface This case study could not have been completed without the assistance of the professionals and professors who have devoted their careers to the development of integrative design. The participants of the case study would like to thank those individuals for their assistance.

We would like to thank Skidmore, Owings and Merril for providing the construction documents for the AT&T Corporate Center. Their genorosity has granted us the opportunity to study an iconic work of architecture and learn about each facet of its design.

We would also like to thank Dr. Michael Kyong-il Kim you for his assistance throughout the course of this study. We appreciate every suggestion and insight you have provided us. We greatly value each lesson you have shared with us, both about architecture and life.

The following case study is a detailed look at the design and integration of the systems of the AT&T Corporate Center. Over the course of a semester, the team has dissected, analyzed and delved into every detail of the building and each of us has gained a wealth of information that has equipped us with the tools to begin improving peoples’ lives through architecture.

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Building Overview

Chapter 1 Building Overview 1.1 Building Overview 1.2 Site Context 1.3 Construction Goals 1.4 Building Configuration 1.5 Building System Overview 1.6 Internal Transportation 1.7 Egress + Life Safety

1.1 Building Overview The AT&T Corporate Center is located in Chicago, Illinois, at 227 West Monroe Street.

Adrian Smith of Skidmore, Owings, & Merril was the main designer for the building commissioned by the developer Stein & Company. The center opened in April 1989. The building is 60 stories tall and is an iconic part of the Chicago skyline. It is the fifth tallest building in the city, reaching a

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height of 1007 feet and totaling 1,500,000 square feet. The primary use of the building is commercial, with its main occupants being AT&T Corporation, Guggenheim Partners, Credit Lyonnais, Alliance Capital Management Corporation.

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Phase 1

1.2 Site Context relatively small. In fact, the building is directly adjacent to the USG Building, also designed by Skidmore, Owings and Merrill. This unique relationship required special consideration of the some of the building’s systems.

Phase 2

The AT&T Corporate Center is located in the Loop of downtown Chicago about two blocks from the Chicago River. It occupies the corner of Monroe and Franklin Streets (in fact, since 2007 the building has been referred to as the Franklin Center). The building is located very close to the Willis Tower as well. The specific site that the AT&T Corporate Center is unique in that it is very close in proximity to the surrounding buildings, making the footprint of the building

Phase 3 Phase 4 Phase 5 Phase 6

Figure 1.1 Aerial View Phase 7

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Phase 8

Figure 1.2 AT&T Building in Chicago Skyline

Building Overview

1.3 Construction Goals All projects have a set of supplementary goals that help achieve the primary goal of the building, to improve people’s lives. The functional utility, aesthetic value, meronic value, constructability, social responsiveness, investment value, and the preservation of the designed value must be simultaneously considered throughout the design process. The AT&T Corporate Center is a good example of the importance of the construction goals because of its proximity to neighboring buildings and construction methods in a confined space.

1) Functional Utility 2) Aesthetic Value 3) Meronic Value 4) Constructability 5) Social Responsiveness 6) Investment Value 7) Preservation of the Designed Value

1.3.1 Functional Utility The functional utility of any building is its primary goal. It consists of functional efficiency, environmental comfort, and safety and protection of the occupants. The AT&T Corporate Center addresses functional efficiency by providing maximum tenant space in the building. The building systems are designed to optimize the indoor air quality and the structural system provides a high level of safety in case of fire, heavy wind loads or other possible strains on the building.

1.3.2 Aesthetic Value While the function of the building is important, its appearance is also a priority. The AT&T Corporate Center needed to establish a presence within the Chicago skyline while also creating an image that tenants find appropriate. The materiality of the building is essential to the design and unique features like the setbacks of the AT&T Corporate Center create a presence that also contributes to the other goals of the building.

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1.3.3 Meronic Value The meronic value of a building is one of the most important supplementary goals of the design process. A building may be considered as a “meron,� which is a part of a larger system. Its meronic value is its contribution to the whole rather than its value as an individual entity. The AT&T Corporate Center is located in a very dense area with much architectural significance so its meronic value is essential. It is immediately adjacent to another building and the heights of both the old and new buildings affected the design of the AT&T Corporate Center. The materiality and program also contribute to meronic value.

1.3.4 Constructability Constructability is a matter of balancing the goals of the building with the cost, quality and availability of the methods and materials. The downtown location of the AT&T Corporate Center makes constructability more complicated than usual. Using module systems may be the most economical option but the size of the job site may limit the size of materials that can feasibly be delivered. Efficiency in constructability can also be improved by using as many similar members as possible, reducing production and labor costs.

Phase 66 Phase Phase 77 Phase Phase 88 Phase

Achieving other goals in the building is pointless if the preservation of design value is not considered. The AT&T Corporate Center is designed in such a way that it continues to function in the same way as time goes on.

Maintenance and repairs must be able to be made with little difficulty or order to preserve the physical integrity of the building. The design should also be adaptable so that new tenants will find the space functional. The building may also transition to a new use all together and a good design should be able to address this challenge as well. Ideally the building will also be self-diagnosing and self-repairing and should be able to adapt to new and developing technology.

Phase 55 Phase

1.3.7 Preservation of the Designed Value

Phase 44 Phase

Buildings such as the AT&T Corporate Center must generate some sort of revenue to maintain themselves. Important considerations must be made for the tenants to increase investment value. The AT&T Corporate Center maximizes its leasable tenant space so as to satisfy possible occupants. Early occupancy was achieved in the building as well so that tenants could begin to rent from the developer as soon as possible.

Phase 33 Phase

1.3.6 Investment Value

Phase 22 Phase

Social responsibility is related to the concept of meronic value and the concept that buildings affect more than just the tenants that occupy them. A socially responsible building will ideally maintain itself. This is very difficult to achieve so most buildings attempt to produce their own energy and prepare for disposability or recyclability in the eventual life cycle of the building. If a building can achieve a collection of systems that contribute to its function, the building can contribute to a greater global sustainability.

Phase 11 Phase

1.3.5 Social Responsiveness

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Building Overview

1.4 Building Configuration The AT&T Corporate Center is primarily for commercial use. The lower levels are used for lobby and retail space while the upper levels contain mostly offices. Vertically, the building is segmented into four sections, each spanning fifteen floors. The sections are separated by the mechanical level at the sixteenth floor and the sky lobbies at the twenty-ninth and forty-fourth floors.

1.5 Building System Overview GROUND LEVEL Pedestrian entrances to the AT&T Corporate Center are located off of Franklin Street and Monroe Street. People may pass directly through the lower lobby to the adjacent USG Building. Other programs, such as the loading dock and service areas are located out of the way of the main pedestrian passage. Vertical transportation is arranged so that unauthorized visitors cannot access areas beyond the lobby and retail space.

UPPER LEVELS The upper levels of the AT&T Corporate Center are most used for tenant space. The lease depth in the building ranges from forty-five feet to forty-eight feet. This is generally a desirable lease depth as it lends itself well to an office space. Each vertical segment is slightly different due to the building’s setbacks.

SKY LOBBIES The sky lobbies function as transition points for the vertical transportation. Passengers can transfer from express elevators to local elevators at the twenty-ninth and forty-fourth f loors.

Machine Room 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 LL 1 LL 2

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Level 60 El. 843’-7”

Tenant Space

Sky Lobby Level 44 El. 602’-8”

Tenant Space

Sky Lobby Level 29 El. 382’-8”

Tenant Space

Mechanical Level Level 16 El. 287’-10”

Tenant Space

Lobby + Retail Parking

Phase 1

Lobby

Phase 2

Retail

Phase 3

Loading Dock + Service Area

Phase 4

Lobby

Figure 1.4 Lobby Program

Phase 5

48 ft

Phase 6

45 ft

Tenant Space

Phase 7

6

Phase 8

Figure 1.5 Typical Upper Level Program (3-15)

Building Overview

48 ft

45 ft

Tenant Space

Figure 1.6 Typical Upper Level Program (18-43, 45-59)

Figure 1.7 Sky Lobby Program

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Phase 1

1.6 Internal Transportation

Phase 2

The small footprint of the AT&T Corporate Center requires special consideration for the elevator system. The main goals of the system are to transport passengers in a timely fashion and to provide security to the tenants. The main security feature is a shuttle elevator from the lower parking area that ensures that visitors may only access the lobby without passing a security checkpoint.

Phase 3 Phase 4

The AT&T Corporate Center uses a series of express elevators in order to better serve the higher level floors. Passengers may ride an express elevator to one of the sky lobbies where they may then transfer to a local elevator. The service elevator is the only elevator with access to all floors.

There are also escalators on the lower lobby level that provide access to the second floor lobby.

The local elevator that serves this area is ADA compliant for accessibility to the upper lobby.

Phase 5

Local Elevator 43-60 Phase 6

Local Elevator 29-44 Express + Local Elevator L2-29

Express Elevator L2-44 Phase 7

Local Elevator 3-15

Service Elevator

Figure 1.8 Vertical Transportation Diagram

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Phase 8

Shuttle Elevator L2-1

Building Overview

Figure 1.9 Elevator Plan (3-15)

Figure 1.10 Elevator Plan (18-28, 30-43)

Figure 1.11 Elevator Plan (29, 44)

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Phase 1

1.7 Egress + Life Safety

90 ft

Phase 2

In the city of Chicago, occupants typically should only have to travel one hundred and fifty feet to the nearest exit, however some stipulations are made for buildings with sprinkler systems. Throughout the AT&T Corporate Center, this item is satisfied.

130 ft

Phase 3 Phase 4 Phase 5

40 ft 15 ft

Figure 1.12 Lower Lobby Egress

Phase 6

40 ft

40 ft

70 ft

70 ft

Phase 7

tinted heat-absorbing glass tempered glass heat-strengthened glass

insulating glass -clear

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Phase 8

mirror glass 45 ft insulated spandrel glass 40 ft clear wire glass Figure 1.13 Typical laminated glass Upper Level Egress

Building Overview

50 ft

60 ft

30 ft 55 ft

55 ft

Figure 1.14 Upper Lobby Egress

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Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Phase 6

Phase 7

Phase 8

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Enclosure Systems [Conventional Wall Systems; Curtain Wall Systems]

2.1 Enclosure System Overview The basic functions of an enclosure system are to keep undesireable conditions such as heat, moisture and humidity, out of the building and to maintain a good air quality inside. The system needs to achieve these goals supplementary building goals as possible. It is important for the system to be easily maintainable and the availability of the desired material should be taken into consideration early in the process. A cladding system should also support the aesthetic goals of the dsign and contribute good meronic value to its surroundings.

There are advantages and disadvantages to both unitized and stick-built methods of construction enclosure systems. It is possible that this entire building could be constructed with stick-built methods but a combination of stick-built and unitized systems would also be feasbile for the AT&T Building. The punched-out window systems are built construction as they attach into their aluminum sills. The amount of to support the stick-built method. The rib windows, however, would make most sense as a unitized system. They are basically constructed as a curtain wall, so a standard unitized system would be

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Storage of the materials must also be considered in the constructability of the AT&T Building. The site was already surrounded by existing buildings when the building was constructed so it is likely that materials needed to be scheduled to arrive at the site ahead of time. Layout of the enclosure system woud also have to be considered within this framework.

Phase 1

2.2Goals of Enclosure System

system and the overall building.

The enclosure system should be designed and constructed in a safe and easy way, preferably from the inside of the building level above. Having an uncomplicated installation for the system is important, such as being unitized to minimize costs of the fabrication.

5. Long Term Serviceability

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Phase 8

To maintain investment value and to preserve designed value, durable material should be used to reduce the overall maintenance needed by the enclosure system. An important component of the investment

Phase 7

Aesthetics is important in any design because that is what people see. We want the users and viewers to enjoy what they see. Therefore the materials chosen should support the aesthetic objectives of the building, which are to be grandeur and opulent. These objectives compliment the building’s post-modern architectural style.

The building should be designed

Phase 6

2. Aesthetic Value

4. Constructability Phase 5

loading conditions present throughout the building.

Phase 4

Achieving meronic value is important in any enclosure system design. It should be designed to support and enhance the related subsystems of the building. The enclosure system should seal the building.

Shading mechanisms, glazing, electrical systems, and HVAC systems should all be included in the encosure system design. This system should be designed to easily attach to the structural system of the building. It should also

The main goal of the enclosure system is to keep out any undesirable or uncontrollable outside conditions of the building, as well as to provide the interior with the best possible conditions. Maintaining a comfortable interior air quality will enhance building occupant productivity, which will contribute to the overal investment value of the building from a tenant perspective. The enclosure system should be located towards the outer limit of the

Phase 3

1. Meronic Value

3. Utility Value

Phase 2

A properly designed enclosure system is important in any complex building, such as the AT&T Corporate Center. The enclosure system must protect the building occupants and the interior of the building from variable and potentially damaging exterior conditions. It is also important to cooperate with the subsystems of the other surrounding buildings. The following are goals of the AT&T Corporate Center, which can also be applied to most buildings.

Enclosure Systems [Conventional Wall Systems; Curtain Wall Systems]

2.3 Cladding value is the aesthetic value; the enclosure system should be designed in such a way that allows for easy maintenance and repair of damaged or vandalized be chosen with long-term availability of replacement materials in mind.

The primary material used for the facade of the AT&T building is granite. The stone panels are attached to a solid concrete wall using L brackets. The joints are treated with sealant with sealant with a backer rod that allows for some movement at the joints.

Choice of cladding material is an important design decision, not only for aesthetic value of the building, but for the ease of replacement and repair. If a panel is damaged at some point during the lifetime of the building and needs to be replaced, certain ma-

Granite Panels

Finish of the material is also imInsulation

others.

Concrete

Insulation Steel Beam

Bolt

Face of Column

Bracket Backer Rod

Sealant Neoprene Gasket Concrete

Figure 2-1

Granite

Figure 2-2: Connection Detail

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Phase 1

2.4 Wind Loads Phase 2

Wind loads increase as a response to three factors: altitude, location on the facade transitions between materials.

Phase 3

When the building is at lower altitudes, it is surrounded at close proximity by neighboring buildings which obstruct the wind. At higher levels the wind velocity increases and greater pressure develops on the building facade.

Phase 4

At any corners and particularly setbacks, loads due to wind are especially high due to the development

Phase 5

moves at a high velocity around the corners will create alternating negative and positive pressure zones that push and pull the building’s facade in alternating directions. The structural engineer of the building must take into consideration this added stress.

Phase 6

Irregularities and setbacks introduce complexity in the building facade, but more importantly it This lessons the load they incur on the building.

Phase 7

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Phase 8

Figure 2-1

Enclosure Systems [Conventional Wall Systems; Curtain Wall Systems]

Level 59

Level 45 Level 43

Level 31 Level 28

Level 19 Level 16

Level 5

East Elevation

West Elevation

South Elevation

North Elevation

Figure 2-2

2.5 Typical Corner Wall System The corner joints of the building must be reinforced to handle additional wind loads. Typicall the corner joind it composed of solid concrete with a granite facing. The granite pieces are attached to the concrete by tie-backs. The downside to this system is that once it is attached, the wall panels Granite curtain wall panels are connected to the typical wall by specially designed “L” brackets. A kerf cut slot in the edge of each of the granite panel slips over an extension at the end of the “L” bracket.

Two neoprene gaskets cushion and suspend the granite panel on the

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brackets. The bracket is tied back to the concrete wall by a steel masonry bolt. The bolt is attached to the bracket through a layer of rigid foam insulation into the concrete wall. This creates an air space between the stone panel and the insulation. This inhibits conduction and improves the overall insulation of the system.

The joint between panels is bridged by sealant applied in front of a backer rod. The backer rod is a compressible material designed to both accommodate movement between the panels and to prevent the sealant from permeating uncessarily far into the joint.

Only two neoprene gaskets are used to cushion each panel. This is to compensate for engineering

Phase 1 Phase 2

tolerances in the manufacturing of the graphite panel, as well as the construction of the wall

Phase 3

on which the panel site; additional gaskets run the risk of being out-of-line with the two that the panel ultimately sits on, subjecting the panel to increased risk of bending and cracking.

2.6 Window Types

Phase 4

The AT&T Building has three main types of windows: punch out windows, two story punch out windows, and rib windows.

The rib windows are basically a curtain wall and comprise the middle sections of the facades

tinted heat-absorbing glass tempered glass heat-strengthened glass

Phase 7

Section 08800:

Phase 6

frm the rest of the building.

Although there are only three main window types, there are many more glazing types. Only main glazing types will be called out in drawings but all types are listed here.

Phase 5

located. Punch outs and two story punch outs are found towards the facade edges. These types make up the main bulk of the facades, however a few variations do exist in areas like the corners and the lower levels.

The lobby area, especailly has a

mirror glass insulated spandrel glass clear wire glass laminated glass

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Phase 8

insulating glass -clear

Enclosure Systems [Conventional Wall Systems; Curtain Wall Systems] Window Type Locations

Vertical Windows

Punch Out Windows

Corner Windows

Three Story Punch Out Windows

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Phase 1

2.6.1 One Story Punched-Out Window System

punched-out window system allows for a 7’-9” double-paned plate glass window, but it does allow for some problems. One problem is that the extension of the

break is used, which perserves the insulation characteristics of the wall, and the panel is sealed to the

not high enough to obscure typical

backer rod. The window is cradled in the alunimum extrusion by two neoprene gaskets on the bottom, and two horizontal neoprene strips that run the legnth of the window.

This seals the inside of the building from the outside, which is very important.

Phase 4

adjacent to the exterior wall. A solution to this problem could be to extend the wall to a higher position such as 3’-10”, which would allow the wall to surpass the height of

Phase 3

The assembly of a punched-out window wall system takes into account several foresights in serviceable design. At the upper limit, the granite panel attaches to an extruded aluminum sill via a tongue and groove steel fastener.

Phase 2

A punched-out window system in a building is when an aluminum sill connects the granite curtain wall system to a “punched-out” window.

This is attached to the building at the exterior vertical concrete columns and extend 1’-7” above the

inches.

Phase 5 Phase 6 Phase 7

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Phase 8

Figure 2-3 Punched Out Window Section

Enclosure Systems [Conventional Wall Systems; Curtain Wall Systems] 2.6.2 Two-Story Punch-Out Window System

2.6.3 Rib-Window System

Both a single and a two-story version of the punched-out window system is dominate the AT&T

A curtain wall system is used

between the two is that the twostory system introduces an aluminum spandrel to obscure the midd it attaches to vertica columns of the tube structure. They rely on a simple clip mechanism to secure the connection. They are also attached to spandrel girders at

segmented and supported at the mechanical penthouse. The “rib window� is basically a curtain wall system is a stick system composed of plate glass and aluminum spandrel panels suspended between vertical and horizontal aluminum spandrels and mullions. The vertical mullions are designed for constructability from the interior of the building.

kinds of vision glasses are used on all four sides of the facade to control the sunlight and to make the

Figure 2-4 Two-Story Punched Out Window Section

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Figure 2-5 Rib Window Section

Phase 7 Phase 8

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Phase 6

The system at the AT&T Corporate Center is successful in achieving its primary goals. The aesthetic of the granite works with its surroundings and adds good meronic value to the area. The system is constructable either as a stick-built or a unitized system and able to be build with the “on-demand” method. Lastly, the enclosure system achieves its main purpose of keeping the elements out and creating an acceptable environment within the building.

Phase 5

2.8. Summary

Phase 4

The AT&T Corporate Center uses a “stick built” system. Most of the work on the enclosure system is building from the oustide. By using a stick built system through most of the building meant that there is no need for extra subcontractors to do any other parts other than the enclosure system. The construction process of the punched-out window system begins with attaching the strongback metal frame to the column or spandrel.

Next the horizontal clip for the granite is attached to the strongback and the granite is place on the clip. This process is repeated until all the granite panels are installed. Last,y the glass will be inserted into the mullion.

Phase 3

to the outside.

2.7 Construction Method

Phase 2

and the anti-walk block keeps the front and back aluminum blocks from rotating against one another.

A steel back pan contains the exterior layer of insulation and is held in place by extruded aluminum elements. Neoprene sponge gaskets run the whole height of the window and suspend the glass within the mullion. On the inside of the rib is a coat of silicone sealant which adds a moisture barrier. There is also a weep hole

Phase 1

In this system, and interior rigid foam intallation is mechanically fastened to an extruded aluminum bracket. The vapor barrier prevents

Structural System: Sub-Structures

Chapter 4 Structural Systems SUB-STRUCTURE 4.1 Structural System Overview 4.2 Foundation 4.3 Foundation Construction 4.4 Slurry Wall Construction

lo a

lo a

d

d

tr an s

tr an s

fe flo r

fe r

flo

or

or

4.1Structural System Overview The primary purpose of the AT&T building’s structural system is to provide structural integrity by protecting its occupants under various forces of nature.

Other objectives are to preserve the physical integrity of the building, aesthetic potential, constructability and economy, and to maximize inter/intra system synergy.

As any building, the structural system can be divided into two parts: the substructure and the superStructure. The sub-structure combines caissons with a slurry wall system. Meanwhile, the superstructure is composed of a concrete-tube structure, interior steel columns, and a combination of transfer floors and columns.

AT&T’s construction method is very interesting, since it places steel columns along the interior spaces, which are referred to as “erection columns.” These columns are used to

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C

A

IS SO

N

S

C

A

SO S I

N

S

Figure 4-1 provide support to the upper unfinished floors during construction. The concrete columns are built around the “erection” columns where steel reinforcement is used to form a belt-like form that wraps around the entire perimeter of the building. This construction system allowed for the building to be built without having to compromise the concrete curing time needed for proper strength.

Phase 1

4.2 Foundation

Phase 2 Phase 3 Phase 4 Phase 5

The slurry wall is not only a retaining structure, but also served in this case, as a wall for the basement floor. The wall is laid out on the perimeter of the site. The perimeter portion contains about 50 caissons, while the core has 12.

Although there were existing caissons, none were reused for the building.

Phase 7

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Phase 8

The slurry walls are used for 10 story or higher buildings with footings on soft clay. For the At&T building, they needed to excavate without causing damage to the surroundings. The walls were filled with bentonite to create the edges of the trench. The mixture of bentonite and water is what is called “slurry.� Bracing or ties (also called rakers) help us support the hhwalls.

Figure 4-2

Caisson Plan Phase 6

Slurry Wall Gravity Load Caissons Special Case for Existing Caissson Grade Beam

Structural System: Sub-Structures

4.3 Foundation Construction

Concrete Column Caisson Cap Temporary Steel Liner Corrugated Steel Liner

60’

Cement Grout Vertical Reinforcement: bars (12-#10s)

Cement Grout: bars (#5@20)

Figure 4-3

Typical Caisson Detail

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Since soil provides adequate compressive forces to contain the concrete, stability is acquired. As a result, reinforcement ends at the lower end and bell column.

Reinforcement at midsection of the column resists columns buckling (vertical reinforcement), and bursting (lateral reinforcement). So, when the temporary steel liner is removed, the corrugated steel liner thrusts the column downward against force.

Figure 4-6

Phase 3

Figure 4-5

6�

Phase 2

Figure 4-4

A new caisson is placed very close to an existing caisson, then the inferred segment is removed. As a result the new caisson is placed so that the bell clears the depth of the existing caisson. The new caisson shaft is placed 6� minimum from the previously existing one. This is a construction technique to allow human error because the existing caisson may not be placed perfectly into the ground.

Phase 1

Existing Caisson Special Condition

Phase 4 Phase 5 Phase 6

Typical Caisson Cap at Concrete

Caisson Cap Detail Phase 7

The caisson cap needs precise construction and it can be built at a time indeterminate of the caisson construction.

Phase 8

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Structural System: Sub-Structures

Slurry Wall Property Line

2’ Slurry Wall

#6 Rebar Hook

#6 Vertical Rebar

#6 Horizontal Rebar

Figure 4-7 Slurry Wall Section

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A slurry wall was required at this site because it is in an urban setting and the neighboring buildings are very close to the site. The soil composition on the site also validates the decision to use the slurry wall.

The wall is 43’ deep along the north and south elevations and steps down to 62’ to meet the east and west elevations. The width of the wall varies, but is usually near 30” wide.

Cap Beam with Key For Slurry Wall Connection

Property Line

Phase 1

Slurry Wall East Alley

Ground Level Phase 2

T-Slurry Wall

Phase 3

Lower Level 1 Phase 4

2’-6” Slurry Wall

Lower Level 2 Phase 5 Phase 6 Phase 7

End Slurry Wall EL (-45’-0”)

Figure 4-8

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Phase 8

Slurry Wall Section at East Alley

Structural System: Sub-Structures Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Col.

Wall Cap Top of Slurry Wall LL1 LL2

B. Slurry Wall 45’-0”

B. Slurry Wall 65’-0”

Figure 4-9 Slurry Wall West Elevation

4.4 Slurry Wall Construction 7’-0” min

Width of Slurry Wall Varies

Maintain Trench Dimension Prior to Excavation

Figure 4-10 Typical Slurry Wall Guide Wall

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7’-0” min

3’-0” min

The slurry wall is built in 24’ segments. The panels alternate shapes so that they may be excavated and supported with steel tubes, then filled with concrete.

Phase 1

Typical Wall Panel (24’-0” max)

This trench is maintained by raker supports at the caisson caps.

Circular Key Formed by Panel Joint Pipe

Phase 2

Slurry Wall

Vertical Reinforcement Phase 3

Horizontal Reinforcement

Figure 4-11 Typical Slurry Wall Panel

2

Excavate Panel 1 and 2 (Drill Out Circular Keys)

3

Excavate Panel 3, Pour Panels 1 and 2, Excavate Panel 4

4

Pour Panel 3, Excavate Panel 5, Pour Panel 4

5

Pour Panel 5

24’-0” MAX

24’-0” MAX

PANEL #5

PANEL #1

PANEL #4

Typical Slurry Wall Construction Sequence 1

PANEL #2

Phase 7

Figure 4-12

Phase 6

PANEL #3

24’-0” MAX

Phase 5

Pour Guide Walls Phase 4

1

Panel pour sequence as seen in SOM’s drawings. It shows panels 1 and 2 being excavated first. The firm went beyong the usual scope by providing suggestions for construction.

Phase 8

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Structural System: Sub-Structures

1

Pour Guide Walls

2

Insert Hollow Steel Tubes as Formwork

3

Excavate Panel 4 and 5

4

Pour Panel 4 and 5

5

Remove Steel Tubes (save for reuse elsewhere), Excavate Panels 1,2,3 Pour Panels 1, 2, 3

PANEL #1

24’-0” MAX

24’-0” MAX

24’-0” MAX

PANEL #3

PANEL #1

PANEL #4

PANEL #2

Figure 4-13 Typical Slurry Wall Construction Sequence 2 8’

The drawing shows where the concrete columns and steel come together. The column and the footing separate from the floor to allow movement of the members. The mud slab eliminates imperfections in the concrete to provide an adequate surface for the footing to sit on.

3’ Mud Slab

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Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Phase 6

Figure 4-14

Lower Level Concrete Plan

Phase 7

Phase 8

32

Structural System: Sub-Structures

Figure 4-15 Lower Level Concrete and Steel Plan

33

Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Phase 6

Phase 7

Phase 8

34

Structural System: Super-Structures

Chapter 5 Structural Systems SUPER-STRUCTURE 5.1 Structural System Overview 5.2 Floor Framing System 5.3 Erection Sequence 5.4 Long Term Reliability 5.5 Set-Back Structural Considerations 5.6 Double Columns

lo a

lo a

d

d

tr an s

tr an s

fe flo r

fe r

flo

or

or

5.1 Structural System Overview As stated in Chapter 4, the main goal of the structural system of the AT&T is to provide structural integrity by protecting a buildings’ occupants against various forces of nature.

The AT&T Building implies a concrete tube structure supplemented by a steel core and steel floor framing structure. This concrete tub`e structure is supplemented by an inner steel structure meant to be temporary for accelerated construction of the floors, which was left as a part of the structure. Whether this method was economical in the end it is up for debate, as the building is overdesigned (therefore more expensive) yet it was built in a shorter time span.

The tube structure acts as both gravity and laterla load carrying device and therefore requires no separation of systems.

35

C

A

IS SO

N

S

C

A

SO S I

N

S

Figure 5-1

The tube structure also offers the tenants less columns, and therefore, more space at the expense of less glazing and natural light.

Phase 1

5.2 Floor Framing System

steel concrete

wide flange beams

Phase 2 Phase 3 Phase 4 Phase 5

Loads: Live Load: 80psf Partitions: 20psf GMB: 10psf

Phase 6

Figure 5-2

Lower Level Framing Diagram Floor Framing Construction Sequence

Phase 7

36

Phase 8

The framing diagram above shows the sequence of the framework that the AT&T Building followed. The building has different connections in the concrete columns. the most important connection is the moment connections between the

perimeter columns and the floor steel trusses and beams. The steel frame in the tower will be put together firstly, then cast-in-place concrete columns will be built after formwork and installation of the reinforcement bars. After 7 days (concrete curing time), the steel beams will be attached to the steel plates, which are literally embedded in the concrete column.

Structural System: Super-Structures

5’ columns spaced at 15’ indicate tube structure steel concrete wide flange beams

Figure 5-3

Upperr Level Framing Diagram

Erection Column

Truss Seat

37

steel core allows longer spans

Phase 1

Structural System: Super-Structures

5.3 Erection Sequence

Phase 2

Exterior Columns

3 Stories 8 Stories Maximum

Temporary Bracing: to secure against lateral loads and help with construction process

Phase 5 Phase 6

Curing Time: 7 days

12 Stories Maximum

Concrete Deck: hardens for 3 days minimum. When finished it spans for 8 floors maximum.

Phase 4

Bracing at this level is removed

Concrete Floor

Phase 7

10 Stories Concrete Perimeter Frame

Steel Deck

Phase 3

3 Stories

Interior Columns

Ground Level

Construction Sequence Diagram

38

Phase 8

Figure 5-4

Structural System: Super-Structures

5.4 Long Term Reliability

Exterior Concrete

Level 47

Interior Steel Column

Level 32

Initial Leveling of Floor

Level 19

Final Position of Floor

Level 0

Settlement due to Creep in Concrete Foundation

Figure 5-5

39

Phase 1 Phase 2

When a concrete structure is loaded, it creep over a certain period of time. This needs to be taken care of during design to allow shrinkage to occur. As a result, the floor slabs were laid out at an angle during construction. Two years later, the floor slabs will be in the trully horizontal. Although, we are not sure what happens years after that because gravity still affecting the concrete.

Phase 3

5.5 Set-Back Structural Considerations Since, the AT&T Building implemented a tube structural system, the setback became an important point of structural consideration due to its unique configuration. The 5’ setbacks require proper bracing, and the double floor space, which is required to accomodate the transfer floor makes the setback points the ideal space to place the mechanical rooms and sky lobbies.

Phase 4

Steel Column From Below

Steel Column From Top Phase 5

Studs Welded to Plate

The setback are located at levels 29th and 44th. Whenever there is a setback, the top floor will act in tension to counteract the compression coming from the wall above that is pussing down.

Shear Plate Phase 6 Phase 7

Figure 5-6

40

Phase 8

Steel Detail At Transfer Floor

Structural System: Super-Structures

Figure 5-6

Compressive/Tensile Forces Diagram

41

Phase 1

5.6 Double Columns

Spandre Beam

Phase 2

Concrete Pour Line

acts in tension

Phase 3

Concrete Pour Line

Concrete Line Concrete Column

Phase 4

acts in compression

Phase 5

Figure 5-7

Concrete Detail At Transfer Floor

Phase 7

Transfer Column Plan Detail

42

Phase 8

The interior of these columns consist of 2 W-Flange columns connected by a shear plate in the middle. The shear plate is also covered by welded studs to insure composite movement with the concrete incasement. The outer W-Flange is then connected to the truss, which counteracts the outward as well as the inward forces created by the load transfer.

Phase 6

These doubled columns appear at the mechanical levels, which also act as the load transfer points between setbacked floors.

Structural System: Super-Structures

Level 29 Framing Plan

43

Phase 1

Phase 2

Phase 3

Phase 4

Phase 5

Level 30 Framing Plan

Phase 6

Phase 7

Phase 8

44

HVAC System Organization and Space Conditioning

Chapter 6 Mechanical System Organization 6.1 Mechanical System Overview 6.2 Chilled Water Loop 6.3 Condenser Water Loop 6.1 Mechanical System Overview In consideration of a building’s Mechanical system, we uphold that the goals of such a system must: provide a comfortable and healthy environment, give a rich environmental experience, and to best facilitate these system needs within and among the other building systems. Herewithin we explore the needs and solutions presented in the AT&T Corporate Center Building.

Levels 45 -60

Level 44

As presented in the Building’s Organizational Overview chapter the AT&T Building’s layout consists of: Office: 1.4 million sq. ft.

Ground Retail: 22,000 sq. ft Total Area= 1.5 million sq. ft Each zone within this layout must be adequately conditioned and ventiliated per each occupation requirement. That is, each zone must be provided an optimum environmental quality in terms of ambient air temperature, humidity, air movement, and adequate circulation and ventilation of fresh air. In order to satisfy these requirements, the AT&T Building uses an All- Air system for space conditioning.

The building’s vertical mechanical systems layout Figure 6-1 consists of 3 dedicated mechanical floors, with an array of cooling towers on the penthouse floor, with smaller fan rooms scattered in the lower levels. The seperation of these floors is typically dictated by the height limits of passenger elevators.

45

Levels 30-43

Level 29

Levels 17-28

Level 16

Levels 3-15

Figure 6-1

Mechanical Space Vertical Layout

Phase 1

20 19 18 17

3 2

Riser Diagram

46

Phase 8

16 1 15 14 13 Figure 6-2 12 Chilled Water 11 10 9 8 7 6 5 4

Phase 7

6-2

23 22 21

Phase 6

This process starts within the 5 hermetic centrifugal liquid chillers 1 located on the 16th floor mechanical level (an adequate height for construction speed considerations (due to long system lead time), and water pumping requirements). Chilled water is then sent into adjacent pumps 2 for distribution between the building’s 7 Air Handling Units 3 via the cooling coils. Figure

29 28 27 26 25 24

Phase 5

In tall buildings, cooling is typically the most essential thermal quality to control and is therefore most readily addressed in the mechanical system. The most important process in this chain is the making of chilled water ( ), that is water which the air handlers use to condition air that is circulated throughout the building. In a building the size of the AT&T Center a Cooling Capacity of approximately 1 ton/270 sq. ft is required. The provided cooling capacity of the AT&T system is 1,052 tons per chiller. These chillers use the condensation process to cool water down to an adequate temperature for use within the Air Handling Units.

3

Phase 4

6.2 Chilled Water Loop

Phase 3

As a result of the All-Air System, chilled water is needed to conditioned (and humidify) the air that is then sent throughout the building in ducts. The process of making and maintaining chilled water is thusly an important task the building’s mechanical system must control.

Phase 2

As a result of the 15 floor limit of a typical passenger elevator, the mechanical rooms are located on the 16th, 29th, and 44th floors. From these floors, each mechanical system serves zones above and below its origin. This system seperation allows for a larger number of smaller machines to serve multiple zones. This creates greater reliability between machines and increased control over thermal comfort. Each mechanical floor contains: Air Handling Units (AHUs), refrigeration machines or chillers, condensing units, cooling towers, and ducts for supply, return and exhaust air, as well as pumps which are needed to help circulate water through the chillers and condensing units.

HVAC System Organization and Space Conditioning

6.2 Condenser Water Loop An additional product must be present in the production of chilled water in a condensing chiller ). Consystem. This is condenser water ( denser water is a biproduct of the condensing process and acts as a refrigerant for the cooling of the chilled water. Condenser water therefore loses heat in the condensing process and must expell its heat for reuse within the system. This adds the requirement of cooling towers.

3 60 59 58 57 56 55

Cooling towers are (almost always) located on the roof or penthouse floor of tall buildings. Cooling towers act to dissipate the heat generated within the condenser water by introducing cool air (by means of big fans and cooler outside air). This simple (and noisy, adding to the requiement of the system’s seclusion) process effectively lowers the water’s temperature allowing for its re-introduction into the process.

The condenser loop then originates through the upper tank of the chillers, 1 where the now hot condenser water is sent into pumps 2 to be pumped up to the building’s cooling towers 3. At this point, the water cascades down plates, is blown through with cool air and is then sent back into the chiller process. A portion of this water is also sent into a seperate array of pumps and is pumped towards the a seperate ‘tenant’ loop for heat exchange 4. Figure 6-3

54 53 52 51 50 49

3

3

29 28 27 26 25 24 23 22 21 20 19

3

18 17

48 47 46 45

2 2

44 43 42 41 40 39 38 37 36 35 34 33

Condenser water is not however only used in the chilled water process. It too is often used in cooling processes for specialty equipment. This equipment (typically supplied by the tenant in the form of packaged A/C units for use in applications such as server rooms) hooks onto its own seperate loop of condenser water. This condenser loop is seperated from the main loop by heat exhanger which transfer heat between the loops without mixing water directly. This allows for greater reliability between systems, whereas the failure of one branch will not affect that of the other.

3

16 15 14 13 12 11 10 9 8 7 6 5 4

1

4

32 31 30

3 2 GRD LL2 LL1

Figure 6-3

Condenser Water Riser Diagram

47

58

Phase 1

57 56 55 54 60 53 59 52 58 57 51 56 50 55 49

Phase 2

48 54 53 47 52 46 51 45 50 49 48 47 46

Phase 3

45 44 43 42 41 40 39 44 38 43 37 36 42 41 35

Phase 4

40 34 39 33 38 32 37 31 36 30 35 34 33 32

Phase 5

31 30 29 28 27 26 25 24 23 22

Phase 6

21 20 19 18 17

Phase 7

16 15 14 13 12

8 7 6 5 4

48

Phase 8

11 10 9

HVAC System Organization and Space Conditioning

Chapter 7 Space Conditioning 7.1 HVAC System Overview 7.2 Mechanical Room Layouts 7.3 Mechanical System Principles 7.4 Conditioned Air Supply and Returns 7.1 HVAC System Overview In a building’s All-Air System, two components, water (for heat transfer and thus air conditioning) and air (as the vehicle for conditioned air) come together and are distributed throughout each occupied zone. This system consists of an array of Air Handling Units, fans, filters, coils, dampers, ducts for supply, return and exhaust air, as well as VAV (variable air volume boxes) with reheaters. The amount of elements at work in this system therefore creates the need for very careful buildingdesign integration.

The cold air that is produced in the chillers must be pumped and distributed to Air Handling Units.

These units contain cooling coils, filters, fans, and ductwork to bring conditioned (in terms of ambient temperature, humidity) as well as fresh air to a building’s occupants.

The AT&T building contains 7 of these Air Handling Units located on all three mechanical floors Figure 7-1. Ductwork leads from these units upwards and downwards from each mechanical space. The division of these service zones may be a function of system reliability or for less dependence and strain on each unit.

Levels 45 -60

Level 44

Levels 30-43

Level 29

Levels 17-28

Level 16

Levels 3-15

Figure 7-1

Mechanical Level Vertical Service Areas

49

Phase 1

7.2 Mechanical Room Layouts The process of transferring heat energy from water to air requires a lot of special equipment and therefore requires large space allotments.

Phase 2 Phase 3

Space organization then is key to creating an effective mechanical system. Because of the immense space requirements mechanical floors are typically multistory levels (planned strategically this space can be benefitted by other multistory space requirments such as elevator overrun space shafts). Below is the layout of the AT&T building’s 16th level mechanical floor Figure 7-2. This bottom half of the level contains all the neccesary equipment for space conditioning. This level also contains the chillers which create the chilled water used by the Air Handling Units.

Chillers alone require additional space for maintanence requirements such as for the cleaning of the chiller pipe system (pull space). At this level (as in all mechanical levels), Air Handling Units mix fresh and recirculated air and send it (via fans) through ductwork to the final occupied zones. Return air is then sent from each occupied zone to the exhaust fans which disspell the air to the outside or recirculate it back into the AHUs.

Figure 7-2

Phase 4

16th Floor Mechanical Level Exahust Fans

AHU

Phase 5

Preheat coil

Phase 6

AHU

Phase 7 Phase 8

50

7.3 Mechanical System Principles The Air Handling Units require a number of additional elements for the proper filtering and conditioning of air through the building Figure 7-3.

These elements include birdscreens for the prevention of animal intervention, and mechanical dampers for control over the amount of air introduced into the system. Other non mechanical elements include air filters for the dissipation of air bourne pollutants, sound attenuators for control over the acoustic environment of supplied spaces, and large fans to facilitate air movement. Oftentimes an additional heating coil may be needed in order to preheat incoming air (this is done to prevent freezing the cooling coils during inclement weather).

Fresh air is an imperative part of the space conditioning process Figure 7-4. Because of the scale of tall buildings like the AT&T Building, natural ventilation via operable windows is often impracticble and undesirable. It is therefore better to have a central (and controllable) source of fresh air intake. This fresh air is filtered and mixed with (often) preconditioned return air and then pulled via fan through the cooling coil (cooled by chilled water). This conditioned air is now ready to be dispersed to each floor of the building. Air distribution in this case is done with ductwork leading vertically through a central duct within the buildings core.

Figure 7-3

Air Handling Unit Plan Detail

M M

COOLING COIL

AIR FILTER

FRESH AIR

BIRDSCREEN

FAN SOUND ATTENUATION

HEATING COIL BUILDING SUPPLY SHAFT

51

FRESH AIR

MACHINE DAMPER

Phase 7

M

CONDITIONED AIR

RECIRCULATED AIR

COOLING COIL

FAN SOUND ATTENUATION

Phase 6

AIR FILTER

BUILDING OUTSIDE AIR/RECIRCULATION FANS

Fresh Air Introduction and Mixture with Return Air. Section detail

Figure 7-4

SPRINGS FOR VIBRATION CONTROL

Phase 5

ACCESS DOORS

TO BUILDING SUPPLY

Phase 4

M

Phase 3

M

Phase 2

FROM BUILDING OUTSIDE AIR/RECIRCULATION FANS

Phase 1

FRESH AIR

52

Phase 8

BIRDSCREEN

7.4 Conditioned Air Supply and Returns Now that the air is conditioned, it must be distributed to the various zones of occupation throughout the building. Vertical movement of conditioned air is handled through a central supply (and return) duct running in the building’s core. At each floor level, air is sent through branch ducts that circulate among the each area within a floor level Figure 7-5. At this point, air is being blown into these areas at a single rate and temperature.

This is effective in terms of mechanical efficiency, but undesirable in terms of thermal comfort which may be different per floor (based upon the tasks performed at each floor, or occupant preference).

Branch Duct

Fan Powered VAV Box

To control air speed and temperature at the local level, VAV’s (variable air volume box) are installed at the terminus’ of branch ducts within each zone.

These machines control the volume of air (by means of machine dampers) let in through each branch into a space. This allows the occupant control over their thermal environment which is always desirable. This controlled air is sent to each space along the perimeter (the most vital area for conditioning (also used against condensation accumulation on windows) via slot diffuser. Slot diffusers send out air along a large area for more thourough coverage.

Slot Diffuser

BUILDING RETURN SHAFT

BUILDING RETURN SHAFT BUILDING SUPPLY SHAFT BUILDING SUPPLY SHAFT

Figure 7-5

Typical Floor Air Distribution Plan

53

BUILDING SUPPLY SHAFT

Phase 1 This ensures that conditioned air is less likely to seep out of the buildling (oftentimes violently in rushing air from opened doors.

As a result of the complexity of the building’s mechanical and air conditioning system, it is vital for well integrated design to consider the effects both spatially/organizationally and the quality of the built environment that is warranted by a mechanical system.

Phase 2

In this way, conditioned air from the AHUs is distributed among each occupied floor of the building. Stagnant or used air is then returned via ductwork in the core back into the system or for expulsion. Air that is returned from bathrooms (and kitchens if applicable) is not recirculated but is exhausted to the outside immediately. The fans ) that exhaust this air (colored here in Figure 7-6 also give the building an overall negative air pressure.

Phase 3 Phase 4

29 28 27 26 25 24 23 22 21 20 19 18

Phase 5

17

Figure 7-6

Air Riser Diagram

Phase 6

16 15 14 13 12 11 10 9 8 7 6 5 4

Phase 7

3 2 GRD

LL1

54

Phase 8

LL2

Electrical System

Chapter 8 Electrical System 1.1 Electrical System Overview The electrical system of the AT&T Corporate Center functions much like any other high rise. The main power is brought in at lower level 2 and brought through the building via the pull room. Power is distributed from the main switchgear room. It is stepped down with the use of transformers as it moves to serve items with lower power requirements. In the case of a disruption in the main power supply, the building has an automatic transfer switch that will connect the building to an alternate emergency power source in the case of an outage.

Figure 8.1 Electrical Room (Level 6,7,9,11,13)

Figure 8.2 Electrical Room (Level 8,10,12)

Figure 8.3 Electrical Room (Level 14,15)

55

GRD LL2

Phase 2

Phase 3

Phase 4

Phase 5

Phase 6

Phase 7

Figure 8.4 Lower Level 2 Power Plan

Phase 1

2

LL1

Phase 8

56 2

Electrical System

29 28 27 26 25 24 23 22 21 20 19 18

16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 LL1 LL2

Figure 8.4 Lower Power Riser

57

3

Phase 1

2

GRD LL2 LL1

Phase 2

Roof 60 59 58 57 56

Phase 3

55 54 53 52 51

Phase 4

50 49 48 47 46 45

Phase 5

44 43 42 41 40

Phase 6

39 38 37 36 35 34

Phase 7

33 32 31

Tra

30 29

22 58

Phase 8

Figure 8.5 Upper Power Riser

Conclusion

In order to implement integrative design, a building must constantly evolve throughout the design process. A small change to one the other systems in the building.

The systems of the AT&T Corporate Center show evidence of this process. The systems come together to create a building that works synergistically and improves the lives of those that interact with it.

The AT&T Corporate Center is a good example of a building with strong telelogical design principles.

Executing a successful integratively designed building is no easy task and Skidmore, Owings and Merrill have managed to meet and even exceed these standards. All of the basic design goals are addressed throughout the building in a manner that not only functions for the occupants of the AT&T Corporate Center, but also functions for the city of Chicago.

mer

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