STRUCTURAL All of the foundation walls, mat slabs, and elevated slabs in Building One are cast in place concrete. Clark Concrete, the concrete sub-contractor, specializes in cast-in-place concrete structures and accounts for approximately one third of the 350 workers that are on the site each day.
The concrete structure is comprised of 30’ x 30’ mm typical bays, with 2’ x 2’ columns and 7” thick floor slabs. In order to reduce the financial burden of the original 8” thick floor slab design, Clark Construction, with the help of Cagley & Associates, proposed a value engineering change that lessened the slab thicknesses to 7”, while incorporating drop panels 8” in thickness around the columns that maintain the building’s structural integrity and blast rating.
The foundations beneath Building One are comprised of rolled W-shaped column piers and concrete pile caps that support a system of grade beams that range in size from 2’-4” x 3’-0” to 5’-3” x 3’-0”. In some places, a 4’-0” thick mat slab sits atop the grade beam system to provide adequate load distribution for the floors above, while a 5” thick slab on grade is located in areas with lesser building loads.
MECHANICAL Building One is serviced by eight McQuay Vision VAV air handling units, ranging in size from 40 to 50 horsepower and 26,650 CFM to 30,800 CFM, located in three mechanical rooms. Three air handling units are located in the north finger on lower level 8, two are located on lower level 8 in the middle finger (Figure #5), and the remaining three are located in the mechanical penthouse located in the south finger on lower level 6 (Figure #6). These air handling units feature water coils that are fed by chilled water and hot water pipelines from the Central Utility Plant. In order to achieve LEED points, the McQuay Vision air handling units include three energy recovery devices; heat wheels, fixed plate heat exchangers, and runaround coil loops.
Once conditioned, air is supplied to localized VAV’s through medium and low pressure ductwork. In areas where additional heating or cooling is required, fan coil units are utilized. These units are fed by the aforementioned hot and cold water lines that are serviced from the boilers and chillers in the central utility plant. The heat recovery devices in the air handling units lend to increased efficiency of the fan coil units by limiting the degree to which the supply water needs to be heated by the boilers in the central utility plant.
ELECTRICAL Within the building, eleven transformers, ranging in size from 150 KVA to 15 KVA, step down the high voltage electrical service from the central utility plant to 480/208 power. This power is distributed to the various electrical closets by a medium-voltage switchgear room in the southern end of lower level 9, and a low-voltage switchgear room located one floor above. The medium-voltage switchgear is backed up by an emergency switch gear located in an adjacent room.
All of the plastic power distribution conduits are located within the slabs overhead. They provide power to the electrical closets, primary and emergency lighting systems, and fire alarm system. Building components requiring large amounts of power, such as elevators and air handling units, are strategically located near switchgear rooms in order to utilize electrical bus-ways to provide the required power to these locations. Elevators are fed by bus-way penetrations through nearby electrical closets. Air handling units are powered through the vertical mechanical chase-ways mentioned above.
LIGHTING Due to its primary use as an office building, the structure is lit predominantly by pendant strip lighting using T6 fluorescent tube lamps. All bathrooms feature cove up-lighting around the vanities and can type down-lighting throughout the remainder of the space. The elevator lobbies also feature can type down-lighting as well as cove up-lighting around the elevator banks. The most complex lighting systems are located in the executive meeting rooms, where fully controllable can type down-lights illuminate the large tables located in the center of the room and track lighting is directed at the white boards. The lighting in these rooms is dimmable to provide optimum presentation and meeting conditions.
Many of the spaces in the building rely on the abundance of natural light from the extensive curtain wall façade. Dry wall recessions into the ceiling above serve as “skylights” that illuminate the exterior offices and hallways.
CONSTRUCTION SUPPORT OF EXCAVATION This project, due to its sloping site conditions, required a substantial amount of excavation support. Steel piles were driven into the ground in areas of deep excavation, including the uphill side of each of the building’s footprints. These piles were secured by 12-strand, steel tiebacks that were fully grouted into the hillside. Lagging boards were installed after every 5’ of excavation, ensuring a stable earth retention system. The support of excavation required for the construction of building one included 12’ high piles and lagging along the eastern side of the building, as well as a 25’ tall system east of the child care wing that is responsible for holding back all of the earth uphill of that location. Additional support was required around the western perimeter of the pond wall in order to excavate the building and pond footprints concurrently, maximizing excavation efficiency. Most of the support of excavation on site is permanent in nature. The exposed faces of lagging board and steel piles will be waterproofed and serve as one side of the formwork for foundation walls.
CONSTRUCTION METHODS Due to building height restrictions in the neighboring counties, the regionally dominant structural system is cast in place concrete due to its ability to maximize the number of stories within a structure by eliminating the wasted plenum space associated with structural steel applications. Most general contractors and subcontractors are extremely familiar with the cast-in-place approach to building construction, and prefer this method over the application of structural steel framing.
Surprisingly, Clark Construction developed a value engineering alternative that implemented the use of precast T-beams on the parking garage (not included in this thesis). However, it was decided that the varying grades and continuously changing laydown areas were not conducive to the delivery and erection of precast beams, and the precast approach was determined to no longer be a viable option on the rest of the project.
UNIQUE SITE CONDITIONS Although the site is one of the largest partially developed tracts of land in the region, with extensive fields and wooded areas, extra space on site was very limited. A number of factors, including the historic nature of the campus, adjacent projects with bordering limits of construction and the necessity for clear access roads and ramps, drastically limits the amount of parking on site. Subcontractors are provided with a designated number of parking passes that they distributed to their foremen. Workers are encouraged to car pool to the site with their foremen, or make use of the nearby public transportation lines and walk the length of the site’s access road to gain entry to the site. Unfortunately, the workers continue to park in restricted areas, warranting the punishment of certain subcontractors who are forced to bus their employees to the site for the remainder of the project. In addition to on-site issues, workers began to park in large numbers along the public road to the east of the site. While parking along this road, although inconvenient to locals who lose the use of a driving lane during the day, was legal, the workers began to scatter their litter along the sidewalks and in the grass median, prompting city officials to visit the site and demand a weekly cleanup operation.
Additionally, the site is surrounded by a previously existing, eight foot high brick wall designed to keep the former occupants of the since-decommissioned mental hospital within the complex grounds, and although the secure nature of the site is monumental to the elimination of material and tool theft, it proved to be a logistical nightmare at times. Each and every visitor to the site, whether they are a delivery truck driver, a consultant, or a project architect or engineer has to be screened, badged and checked-in at either of the two main gates. The “guest approval” system put in place by the security company is flawed at times, and sometimes prevents the swift access-to-site of numerous mission-critical guests, leaving the construction process at the hands of the security company.
GEOTECHNICAL The soils on site are much more unstable than initially believed. Geotechnical specialists underestimated the soil’s reactivity to the introduction of water during the excavation phase. There are no traces of rock on the entire site, which is comprised predominantly of the aforementioned compressed clay material. Global stability issues prompted the design development of concrete caisson systems that provide the necessary bearing capacity for the large building above. Additionally, the site is very reactive to inclement weather. During dry weeks, the clay material hardens to a state that prompts angular shearing during excavation, making trench digging operations extremely difficult. Conversely, during rainy weather, the site becomes very favorable for surface trenching and minor excavation operations, but does not provide much rainwater absorption, leading to the ponding of water both inside and outside of the buildings. This rainwater also softens the clay material, resulting in unpredictable movement and settling of excavated areas, demanding the implementation of the aforementioned caisson system in some areas of the building footprint. Rainwater remediation efforts demanded the undivided attention of a large portion of the general laborers on site, setting them back on their other responsibilities such as fall protection, access ladder and general carpentry erection and repairs. Fortunately, as the building progresses up the hill and under-drainage is put into place, the severity of these storm water issues substantially lessened, allowing the rest of the work to progress more smoothly. Fortunately, the elevation and sloped nature of the site lends to the absence of any subsurface aquifers or water tables, eliminating any construction issues associated with the necessity to dewater areas of deep excavation, unless it rains, when most low spots, as previously stated, experience extensive ponding.
SMALL BUSINESS REQUIREMENTS In a partnership with the United States Small Business Administration (SBA), Clark Construction committed to soliciting and awarding approximately $145M in subcontracts to the following small business groups:
SB – Small Business
SDB – Small Disadvantaged Business
WOSB – Women-Owned Small Business
HUBZone – Historically Underutilized Business Zones
VOSB – Veteran-Owned Small Business
SDVOSB – Service Disabled Veteran-Owned Small Business
In addition to subcontracting requirements, Clark is required to make attempts at employing local residents on the project. In order to achieve this goal, Clark joined a registered Apprentice Participation Program that helps local employees develop the skills required to become skilled craftsmen. Currently, there are 50 local residents that have gone through this program employed on site.
CONSTRUCTION MOTIVES This project is to serve as the tenant’s flagship headquarters, and was approached by the owner as a Design-Build RFP for two main reasons. The first, the project required an aggressive, fast tracked schedule (see Figure #3) in order to meet the owner’s long term goals for the relocation of multiple properties in an attempt to streamline their operations. Secondly, the owner is very confident that the Design-Build approach will allow them to meet their sustainable goals through the integration of a design team capable of incorporating sustainable aspects in the building’s design, and a contractor/subcontractor presence that will provide continual cost analyses of the proposed building features. They strongly believe that together, this designer/contractor team will be able to deliver a high-end, high-value product in a substantially shorter amount of time when compared to a traditional design-bid-build approach.
In order to successfully meet the owner’s schedule acceleration desires, Clark Construction, with the help of its design subcontractors, HOK, WDG and McKissack and McKissack, approached the bridging document development and design process with the idea of beginning excavation soon after this process began. Luckily, the bridging documents, developed by Perkins & Will, outlined the owner’s desired building footprint and basic structure. This allowed the design team to produce site, civil, and foundation drawings early in the design process, expediting the release of the associated contracts which permitted groundbreaking and site development operations to begin early in the design process. This overlap of design and construction is crucial to the time-based success of the project. Additionally, the tiered design of the project allows for the phased construction of the building. Excavation efforts began on the lower part of the site and worked uphill, allowing the foundations and structure of Building One to begin shortly after the site was prepare, while excavation activities progressed up the slope. This ultimately allows for the phased construction of Buildings One, Two and Three respectively, so that the façade, MEP and interior trades can essentially “chase” one another up the tiered structure. This staggering of trades further exploits the advantages of the fast-tracked approach to building construction. While phased-occupancy requirements COULD be met through this fast-tracked approach, the owner has not chosen to implement any such requirements on the design-build team at this time.
Due to the dilapidated state of the their current facilities and the fact that this office building will serve as the their main headquarters for many years to come, the owner committed to spending approximately $550M on the project in order to provide their employees with a state of the art, sustainable facility that surpasses the quality of similar facilities in the area. The owner is determined to provide a facility that will promote productivity, worker satisfaction, and provide a high level of security and safety to its occupants. These goals are met through the utilization of ample day-lighting, extensive interior courtyards, and state of the art security and blast rated systems.
In addition to their sustainable and space utilization goals, the owner also expects a high level of quality from the design-build team. To ensure that these expectations are met, Clark partnered with McKissack and McKissack’s quality control division in a quality assurance subcontract separate of the CUP and Garage design contract. The quality control team is responsible for overseeing water tests on all of the MEP systems, operational tests of the vertical transportation systems, and wall close-in inspections. KTLH Engineers and ECS Testing Services were also subcontracted to oversee the quality and structural design compliance of the entire cast in place concrete and curtain wall embed system on the project. In a partnership with Harmon Glass and Atlantic Waterproofing, the glass and brick façade system will undergo stringent water tests to ensure the compliance of all waterproofing details and design facets.
Project Team and Delivery Method Stringent project controls and a watchful field staff are crucial in the effort to meet the aforementioned owner requirements and expectations. The quality control measures in place help establish a system of controls that will ensure that the installed systems and materials are of the highest craftsmanship and meet or exceed the project specifications and requirements. The presence of an experienced and attentive field staff will further support these quality control measures, assuring that the work in place is of high quality and meets the design standards. The support provided by the on-site design team members promotes a continual awareness of the design intent and minimizes the application of in-field coordination techniques that conflict with the project specifications. This attribute of the design-build team alone is irreplaceable, as it helps guarantee that actions taken in the field are not later deemed unacceptable, requiring additional remediation that can adversely affect the project schedule and budget.
As previously discussed, the design-build project delivery method is utilized on this project. The main driving force behind this decision is the owner and tenant’s desire to implement a fast-track approach in order to expedite the construction process. Additionally, the complex bridging documents produced by Perkins & Will, along with the requirements associated with a LEED Gold rating demanded an interdisciplinary team that can effectively work together in order to understand and foresee the relationships between the design and construction of advanced building systems and sustainable features, ensuring a cohesive design that is not only highly efficient and functional, but also constructible.
CONTRACT TYPES The relationship connections in the organizational chart found in Appendix D are numbered based upon the type of contract between the two connected parties. Below is an explanation of these contractual agreements.
#1 – Owner/Perkins & Will Contract – Guaranteed Maximum Price The owner of the project partnered with Perkins & Will to create bridging documents that would later become the basis of design for the Clark design-build team. Perkins & Will was awarded a guaranteed maximum price contract that held them responsible for the production of initial bridging documents on the project. Their contract was completed when the design was turned over to the Clark design-build team for further development.
#2 – Owner/Clark Construction Contract – Lump Sum Clark Construction and its design partners were awarded a lump sum bid contract that includes all design and construction costs. Due to the foresight of various unforeseen conditions and possibility of owner change orders, a negotiation clause was added to the lump sum contract to allow Clark Construction to add appropriate additions to the contract in the event of a change directive.
#3 – Clark Construction/Design Partners Contract – Negotiated GMP The designer partners on this project were subcontracted by Clark Construction through negotiated guaranteed-maximum-price contracts. The designers submitted bids that included design costs and fees associated with the initial design process, but were able to negotiate reimbursements for any changes that led to further design work in the future.
#4 & #5 – Design-Build Team/Engineers Contracts – Negotiated GMP Similar to the contracts utilized between Clark Construction and its design partners, the design-build team entered into negotiated guaranteed-maximum-price contracts with engineers and consultants. These contracts included costs and fees for the design and consulting work during the originally planned design period, but included a negotiation clause through which the firms could gain reimbursements for any additional work associated with project change orders and unforeseen conditions.
#6 – Clark Construction/Subcontractor Contracts – Negotiated GMP In order to preserve the competitive bidding process, Clark Construction solicited guaranteed maximum price bids from interested contractors. Like the other GMP contracts, these too included a negotiation clause that permits subcontractors to seek proper payment for changing project specifications and conditions.
#7 – Subcontractor/Third-Tier Subcontractor Contracts – Not Available It could be reasonably assumed that subcontractors and third-tier subcontractors were bound by negotiated guaranteed maximum price contracts as well. This would allow the subcontractors to evaluate their subcontractors on a level playing field, but also allow the third-tier subcontractors to negotiate the cost of any changes in the contract documents.
FIRE PROTECTION The entire building is protected with a dry-pipe, pre-action system that fills with water once smoke has been detected. In the event of a sprinkler head rupture, water will be present in the pipes to immediately address any fire in that area. Due to their element-exposed outdoor nature
TRANSPORTATION Building One has six traction elevators, located in the northeast and northwest corners of the building. These elevators service floors LL9 through LL6, with hoistway penthouses located on the roof of the building.
TELECOMMUNICATIONS The telecommunications package was not included in Clark Construction’s contract. A telecommunications specialist was hired by the owner to provide design and installation services for the telecommunications systems.
SPECIAL SYSTEMS BLAST PROTECTION Due to the sensitive nature of the building’s future tenants, the building’s curtain wall and masonry façade meets blast rating requirements. The building is divided into three blast rating categories, Level I to III. Due to its proximity to the entrance road, the building’s façade in the southwest corner is clad in Level III blast rated curtain walls and masonry. The blast rating diminishes to Level I towards the northeast corner of the building.