Project Team

            Owner:  Kingstowne Office 36 LP   www.hallecompanies.com
            General Contractor:  L.F. Jennings Inc.   www.lfjennings.com
            Architects:  Davis, Carter, Scott Ltd.  www.dcsdesign.com
            Civil Engineer:  Tri-Tek Engineering   www.tritekinc.com
            Mechanical Engineer:  Jordan & Skala Engineers, Inc.   www.jordanskala.com
            Structural Engineer:  Cagley & Associates   www.cagley.com
Dates of Construction:  October 24, 2011 – Early 2013
Cost: $20,000,000 
Project Delivery Method:  Design- Bid-Build

Architecture

Kingstowne 36A is an 8 story office building located in Fairfax County Virginia. It will contain 4 levels of concrete structure parking garage and 4 levels of composite steel construction office space.  Space has also been allocated for about 5,000 square feet of retail area on the ground floor.  When completed, Kingstowne 36A will be part of a master planned development for retail and office space owned by the Halle Companies.  Being a part of a master planned development, the building was designed to match the appearance of the surrounding buildings.  This appearance can be characterized by a rectilinear footprint, pink velour brick, aluminum storefront with glass of blue/black appearance, and precast concrete bands around the circumference of the building.

Major Model Codes

2006 Virginia Uniform Statewide Building Code (Supplement to 2006 IBC)
ASCE 7-05
ACI 318-08
Manual of Steel Construction 13th Edition
2006 International Mechanical Code
2006 International Plumbing Code
2006 International Fuel Gas Code
2005 National Electrical Code
2006 International Fire Code

Zoning

            Location:  Fairfax County, VA
            Zone:  PDC
Use:  4-Story Office Building over 4-Story Parking Deck
Building Use Group:  B, S-2
            Type of Construction:  1B with Automatic Sprinkler
            Allowed Building Height:  11 stories or 160’
Allowed Floor Area:  79,000 Sq.Ft. for S-2, Unlimited for other occupancies

Building Enclosure

Facades

Three different façade styles were mainly used to enclose this building.  They consist of precast concrete panel with thin brick finish of color pink velour by Yankee Hill Brick & Tile, 1” thick insulated glass, and ¼” parking garage glass.  The 1” thick insulated glass is used at the office levels while the parking levels allow use of only ¼” thick glass.  All glass is supported by an aluminum storefront system, black in color.

Roofing

The roofing system consists of white EPDM membrane fully adhered over 6” minimum of R-30 continuous rigid roof insulation.  Where mechanical equipment is located within the penthouse, this is supported by 2” galvanized composite steel deck with a 3.5” thick concrete topping.  In all other areas of the roof, the system is supported by 3” roof deck.

Construction

Construction on Kingstowne Section 36 A started in October of 2011 and is currently being built under a design-bid-build delivery method.  Construction is expected to be completed sometime in early 2013.  Total cost for the building is expected to be just over $19 million.  Since KT36A is essentially being constructed into a hillside, handling the immense amount of unbalanced soil load is a significant challenge associated with constructing this building. 

Electrical

Power enters the building at the east parking entrance located at the south-east corner of the building where a utility transformer is also found.  From here, it travels to the main electrical room at the central core of the building on the P-1 parking level.  Adjacent to the main electrical room is the emergency electrical room which is supplied by three backup generators located south of the building on the opposite side of the south parking lot.  Power entering the building is split into 480/277 V 3 phase for mechanical and lighting loads and 208/120 V 3 phase for primarily receptacle loads. 

Lighting

Lighting in KT36A is generally supplied by 277V circuits throughout.  The façade is illuminated by metallic silver, wall-mounted decorative fixtures projecting vertical bars of light up the sides of the building.  Navigating the parking garage levels at night is made possible with Lithonia surface mounted parking deck fixtures outfitted with 100 watt Osram H.I.D. lamps.  Four foot long luminaires by Columbia outfitted with two T8 fluorescent lamps provide lighting in the retail space area.  The same Columbia luminaires are used for emergency lighting at the office levels, which will then be used to light the ceiling plenum once the ceiling is installed.  General lighting and the ceiling style at the office levels will be chosen at the discretion of the building occupant.

Mechanical

Three split system heat pumps ranging in total CFM from 600 to 1,800 provide heating and cooling to the lobby and retail space.  Two 5.0 kW electric unit heaters provide additional heating in the retail space area.  The garage levels are generally conditioned with multiple supply/exhaust fans at each level, each supplying/exhausting approximately 18,000 CFM of air when operating.  Four 5.0 kW electric unit heaters providing 350 CFM each at the highest level of parking provide some heat below the first office level floor in order to reduce the temperature difference between the un-insulated office floor and the uppermost  parking level.  The office levels are conditioned using four rooftop units, each weighing about 17,000 lbs, with natural gas fired heating ranging in total CFM from 19,500 to 21,500 to provide heating and cooling for the tenants. 

Structural

Foundations

Using the information provided by Burgess & Niple, Cagley & Associates designed concrete spread footings, bearing on Geopiers, ranging from 27” to 44” in depth to support the columns of KT36A.  48” thick mat foundations, also bearing on Geopiers, are located at the central core of the building to transfer forces in the main shear walls to the soil.  Geopier diameters typically range from 24 to 36 inches and are compacted using a special high-energy impact hammer with a 45-degree beveled tamper.  Concrete grade beams of 30” depth are used throughout level P0 to also transfer forces from the shear walls to the column footings.  Foundation walls are supported by continuous wall footings designed for an allowable bearing pressure of 2,500 psf.  All foundations are to bear a minimum of 30” below grade unless stated otherwise. 

Garage Structure

As previously mentioned, KT36A utilizes cast-in-place concrete for the support structure in the garage.  With the exception of the 5” thick slab on grade, this system consists of 8” thick two-way, flat slab construction with drop panels that project 8” below the bottom of structural slab.  The drop panels are continuous between grid lines C and D to help the slab span the increased distance of 36’-6” in this bay, otherwise, they are typically 10’-0” x 10’-0” in size.  Due to the need for vehicles to circulate vertically throughout the parking garage levels, the floor is sloped on 3 sides of the central core to achieve this.  A typical bay size for the concrete levels is 28’-6” x 29’-0”.  Supporting the floor slabs are cast-in-place concrete columns constructed of 5000 psi concrete, most commonly 24” x 24” in size. 

Cast-in-place concrete shear walls resist the lateral forces present in the parking garage levels of KT36A.  All of the twelve walls present in the building are 12” thick and cast using 5000 psi concrete.  Six of the shear walls extend 4-5 stories from the 48” thick mat foundations to office level 1 which is also the 5th elevated floor of the building.  Three of the six walls are oriented to resist lateral forces in the N-S direction while the other three walls are oriented in the E-W direction.  The remaining six walls are only one story tall and are oriented to best resist the lateral soil load at the lowest level of the below grade parking.

Office Structure

Office level 1 is constructed of the same cast-in-place style of construction as the garage floors below it with the exception of the top of slab elevation being uniform throughout the floor.  The remaining floors are constructed using a composite steel system.  This system is comprised of 3 ¼” thick lightweight concrete on 2” x 18 gage galvanized composite steel decking.  The 3000 psi lightweight concrete (115 pcf) coupled with the decking yields a total slab thickness of 5 ¼”.  The decking typically spans 9’-6” perpendicular to cambered beams of varying size.  W21’s and W18’s account for most of the beams while the columns range in size from W12x40 to W14x109.  The columns are all spliced just above the 7th floor (office level 3) where they are reduced in size to more economically carry the lighter axial loads. 

Lateral forces at the office levels are transferred to the concrete shear walls through three different frame systems.  Concentrically braced and eccentrically braced frames work in the north – south direction while ordinary steel moment frames resist the loads in the east – west direction.   Diagonal bracing for the frames consists of either HSS10x10 or HSS9x9 of varying thickness.  Beams and columns in the lateral system are upsized from the common sizes in order to handle the increased forces seen in the members.  

Fire Protection

The concrete construction used in the parking garage levels inherently provides the 2 hour fire rating needed for this area.  Once into the office levels, the steel beams and columns are covered in a 2-hr spray applied fire resistive material.  The underside of the steel floor deck does not require additional fireproofing since the 3-1/4” thick lightweight concrete it supports creates a 2-hr rated assembly.  1-hr rated assemblies are present at most of the roof with the exception of the stair and elevator roofs where a 2-hr rated assembly is required.  Automatic sprinklers are located throughout all levels of the structure.

Circulation

Two entrances are present for entering the parking garage, one at the east end of the building and the other at the west end.  The west entrance provides access to limited parking as it does not tie into the rest of the garage, while the east entrance allows users to circulate in both directions and vertically to all levels of parking above what is accessible from the west entrance.  Three elevators and two stair towers that circulate tenants and equipment vertically to all levels of the building are located in the central core of the building.  The central core can be accessed at all levels of parking and through the main entrance lobby area next to the retail space.