After decades of minimal ac-tivity, steel-framed parkingstructures are gaining popu-larity with designers and de-velopers, according to Dale

Denda, an industry analyst with the ParkingMarket Research Company. “Exposed steel-frame construction is back as a recognizedoption for multi-story parking structures,” heinsists.

Steel has long been recognized for its ob-vious advantages: lower construction costs (inaddition to reduced structure weight whichreduces foundation costs), rapid constructiontime, and longer clear-spans. Some designershave also touted steel’s security benefits—fewer and smaller columns mean fewer placesfor predators to hide.

In the past however, some designers haveshied away from steel because of structuralfire protection requirements and perceivedfailings of standard coatings. Fortunately, thesteel industry has addressed both of theseconcerns.

In 1972, the steel industry sponsored thefull-scale Scranton Fire Test, the results ofwhich put the fire safety issue to rest. The testshowed that a car fire in an open parkinggarage does not spread to fully involve adja-cent vehicles, and temperatures of unpro-tected steel during this exposure are wellbelow those at which the strength of struc-tural steel begins to diminish. Today, underthe International Building Code, open, de-tached parking garages up to 75’-high can beframed with unprotected steel in most juris-dictions. In fact, a study of more than 400

STRUCTURE ◆ July/August 2001 37

John Cross, P.E.

AT&T-Lucent, Warren, NJ

38 STRUCTURE ◆ July/August 2001

parking garage fires during the past decade bythe Parking Market Research Corporationreveals less than a total of $50,000 in struc-tural damage.

The coatings industry has also playedtheir part in increasing the viability of steelfor parking structures. Today, coating tech-nology exists that can effectively protect steelframing systems with limited touch up forsignificant periods. Hot dip galvanizing,which utilizes the cathodic process of intro-ducing zinc to the corrosion “circuit” as thesacrificial anode, has a projected protection

life (less than 5% surface corrosion) in excessof 40 years.

Likewise, new high-performance paintsystems are now available at an economicprice. Today’s high performance paint sys-tems, which utilize zinc rich primers and oneor two topcoats of epoxy, have an expectedlife-span (with minimal touch-up) that ex-ceeds 25 years.

Steel has made the fastest inroads into theairport, health-care and university markets.These three markets share the need for fasterection on tight sites, and also often are in-volved with the expansion of existing struc-tures.

Portland International Airport,Portland, OR

A notable recent project is the expansionof a parking garage at Portland InternationalAirport. The project involved adding 3,300spaces to an existing three story, pre-cast con-

crete framed parking structure. Steel was cho-sen as the framing material for the garageexpansion to minimize structure weight andallow the existing garage to remain open dur-ing the construction process. The design ofthe expanded structure called for a four-storyaddition to the top of the existing garage anda 95’ widening of the existing structure witha seven-story steel framed addition.

The expansion of the garage required7,500 tons of structural steel. Typical interiorfloor framing for the expansion consisted of3” composite G90 galvanized metal deckingwith a 3-1/2” concrete topping. Reinforcingsteel was added to the low flutes of the deckas a backup system in event of deck corrosion.W16x26 floor beams span 30’ to W30x116girders with columns in a 30’ x 60’ bay sys-tem. Two levels of the expansion were sup-ported directly on top of existing pre-castconcrete columns. New pin piles were in-stalled inside the garage and supported ap-proximately half the weight of the existingstructure and the upper two levels of the ex-pansion.

The west expansion of the garage was col-umn free to allow buses and commercial ve-hicles unimpeded access. To create thiscolumn free space, W33x118 beams at 10’ oncenter span 95’ between column lines. To ac-complish this span large cambers were re-quired that varied from beam to beam toprovide slope for storm water runoff.

Structural engineer for this award-win-ning project was KPFF Consulting Engi-neers. Project architect was Zimmer GunsulFrasca. Baugh Construction served as generalcontractor with Fought & Company andCanron Steel as steel fabricators.

Jefferson at Lenox Park, Atlanta, GA

A different approach to steel–framed,conventionally reinforced cast-in-place decksystem was utilized for an apartment complexparking deck at Jefferson at Lenox Park inAtlanta, GA. A clear span, 62’ parking baywas constructed using a castellated steel beamin a composite system with the slab and thedeck. The system included the use of a 30”castellated beam fabricated from W21x44and W21x50 wide flange beams. The typicalbeam weighed only 47 lbs. per lineal foot, re-ducing the overall weight of the parkingstructure. The smaller top cord section hadwelded stud shear connectors applied in thefield and is composite with the corrugatedmetal deck and concrete. The deck consists ofa 3” deep, 20-gage composite galvanized deckwith 3” of normal weight, reinforced concreteover the high corrugation.

Principal exterior girders are regularW24x62 wide flange beams on 30’ spans. Thelargest column section is a W8x67. The low

Portland International Airport, Portland, OR

Jefferson at Lenox Park, Atlanta, GA

weight of the steel in the structure allowedsignificant savings in the foundation costs forthe project resulting in a total per space costof $4,500 and a differential cost savings of$600,000 compared to a concrete alternative.A vibration study of the finished project wasconducted by Dr. Thomas M. Murray, P.E.,who concluded that the performance of thebeam-deck system was excellent with “barelyperceivable” vibrations.

The project was developed by JPI, Inc.with JPI Construction serving as the generalcontractor. Structural design was completedby Alliance Structural Engineers. SMI SteelProducts supplied the castellated beams.

Winthrop University Hospital, Mineola, NY

The parking requirements of theWinthrop University Hospital were ad-dressed through the recent construction of a630 space, three-story steel framed parkingstructure with a 6” nominal composite, posttensioned deck. Ten feet floor-to-floor heightis typical with a minimum clearance of 7’2”.Architectural pre-cast panels are used as afaçade treatment for the structure. The post-tensioned deck was chosen based on the hos-pitals desire to avoid joints and maintain alarge expanse of crack free space typical withthis style deck. This minimizes the probabil-ity of leakage and/or chloride contaminationof the slab, which in turn reduces mainte-nance and future repair expense. Also, by uti-lizing post-tensioning, the amount of steelrequired to reinforce the slab was reduced. A40% solids penetrating silane sealer was ap-plied to the deck surface to act as additionalprotection against moisture and chloride ab-sorption.

The structure utilized 750 tons of steel.Typical members were 30” deep spanning 60’across drive lanes and parking bays. By utiliz-ing the composite action of the steel framerunning in a single plane across the driveaisles and parking bays and the concrete deck,the weight of the steel frame was reduced toabout 9 lbs. per square foot. The concretefaçade panels were erected at the same time asthe structural components to add stability tothe structure during erection.

The steel was protected by shop blastingto bare metal (SSPC-SP6) and shop applying3 mils of an epoxy/zinc based primer. A 4 to

6 mil epoxy topcoat applied in the field com-pleted the protective coating system.

The project was constructed as a de-sign/build project by Carl Walker Construc-tion and Carl Walker, Inc. Sydney Brown andSon served as the architect and Axis Con-struction was the construction manager. Thedesign/build contracting approach was cho-sen in order to facilitate faster project deliv-ery and resulted in significant time savingsthrough the simultaneous structural design,foundation work, steel fabrication and millorders.

AT&T-Lucent, Warren, NJThe benefits of combining a steel-framing

system and pre-cast double tee decks are veryapparent in four parking structures con-structed at AT&T’s office complex in War-ren, NJ. The four garages contain a total of3,600 spaces on three levels.

The garages were designed by ZaldastaniAssociates and fabricated by Interstate Steelutilizing the Hybrid System approach. TheHybrid System consists of paired steelcolumns and girders designed to support thepre-cast floor deck and provide lateral stabil-ity during and after construction. Pairedplates at 5’ -on-center interconnect the pairedcolumns vertically. The columns were erectedto full height, interconnected at each floorwith steel girders at each of the two columnlines. This arrangement provides vertical sta-bility in the transverse direction by the ladder

frame cantilevering from the ground and inthe longitudinal direction by conventionalframe action.

Special attention was given to connectiondetails in order to create a moment resistingframe that enabled the steel supported struc-ture to readily resist lateral forces without theintroduction of unsightly shear walls or brac-ing.

The floor consists of pre-cast double teesthat were attached to the top flange of theframe’s steel girders. The flanges of the dou-ble tees were welded together in the mannernormally provided for pre-topped tees and aconnection was made between the tees in ashaped cast-in-place infill that incorporatesfloor and roof drains into the deck system.

The Hybrid System has been optimizedto reduce the number of pieces in construc-tion and to simplify erection. The advantageof the approach was evident in the design andconstruction of the project in a ten-monthperiod, matching the demand for parkingspaces from the adjacent office buildings. Thetotal cost savings of the Hybrid System overthe concrete alternative exceeded one milliondollars.

John Cross, P.E., is National Project Directorwith AISC Marketing, LLC in Chicago.

STRUCTURE ◆ July/August 2001 39

Winthrop University Hospital, Mineola, NY