STEEL COMMITTEE OF CALIFORNIA

TECHNICAL INFORMATION & PRODUCT SERVICE

FEBRUARY 1986

UN FIRE PROTECTED EXPOSED STEELPARKING STRUCTURES

INTRODUCTION

The key to construction economy in amultistory parking deck is its structuralframing system. From 55 to 65 percent of thetotal cost of most parking structures is thecost of structural components -- framing,floor slabs, and foundations. It is apparent,therefore, that the selection of the structuralframing system is oneofthe most importanteconomic decisions involved in the designof a parking structure.

Un Fire Protected exposed steel was pro-hibited by restrictive building code provi-sions, originally developed for enclosedgarage buildings, that required fire-ratedconstruction in all parking structures. Everysteel framing member had to be "fire-proofed", at extra cost, even in open parkingdecks.

The 1985 Uniform Building Code recog-nizes the results of several recent fire testsin open parking garages so that limitationon area and height of non-fire protectedsteel parking structures has been relaxed.Changes have come about largely due to atest sponsored by A.I.S.I. in cooperationwith the Scranton, Penna. Parking Authority,the Scranton, Penna. Fire Bureau and Under-writers Laboratory. The new code now allowsconstruction of Un Fire Protected steelframed open parking structures of unlimitedarea with certain restrictions noted later.

The elimination of fire-protective encase-ment has reduced the cost of open-decksteel parking structures by 7-10 percent. Nosimilar reduction has occurred in the cost ofconcrete parking structures, because con-crete construction is essentially the sameunder both new and old codes. As a result,prestressed and reinforced concrete parkingstructures that once had been competitive

with fireproofed steel structures are nowsignificantly more expensive than today'sexposed steel structures.

No owner or designer can afford to ignorethe potential savings inherent in steel con-struction forparking structures. In 1986 it'sa new deal with a new structure -- anexposed steel structure -- that offers Iowcost and greater value than any otherparking structure.

GENERAL

An open parking garage is a structure ofType I or Type II construction with openingson two or more of its sides. Area and heightlimits for open parking garages are given inthe table below, re-printed from the 1985Uniform Building Code,

Type of Area Per HeightConstruction Tier Ramp Access

I Unlimited Unlimited

II-FR 125,000 12 Tiers

I1-1 HR 50,000 10 Tiers

II-N 30,000 8 Tiers

In order to be considered "open" thestructure must meet the following:

1. It must be open on two or more sideshaving an open wall area on each tier of 20%or more of the total perimeter wall area ofeach tier.

2. The total length of the openings mustbe at least 40% of the perimeter.

AREA & HEIGHT INCREASES

Area & height increases over that allowedby the above table are permitted if:

1. The structure is open on three fourthsof the perimeter, a 25% increase in area pertier and one tier increase in height is per-mitted.

2. The structure is open around the entireperimeter, a 50% increase in area per tierand one tier increase in height is permitted.

These area & height increases allowedwhen the structure is "open" on three or foursides result in the following table for TypeI1-1 Hr & Type II-N construction. Also in-cluded in the table is the parking capacitybased on a•3 area of 300 sq. ft. per car.

Type o! Area Per Gross No. ofConstruction Tier Height Area Cars

II-N (Open 3 Sides) 37,500 9 Tiers 337,500 1,125

II-N (Open 4 Sfdes) 45,000 9 Tiers 405,000 1,350

I1-1 HR (Open 3 Sides) 62,500 11 Tiers 687,500 2,292

H-1 HR (Open 4 SJdeS) 75,000 11 TJer$ 825,000 2,750

If the structure is constructed to heightsless than the number of tiers shown in theabove table the following applies:

1. The area per tier may be increasedprovided the gross area does not exceedthat allowed for the higher structure.

2. At least three sides of each larger tiermust have openings at least 30" high for atleast 80% of the length of the side.

3. No part of the larger tier can be morethan 200 feet from an opening.

4. Each opening must face a street oryardaccessible to a street with a width at least 30ft. for the full length of the opening.

5. Standpipes must be installed on eachtier.

Since publication of the 1982 UBC thecode has permitted construction of openparking structures of Type I I-FR, Type I I-lHor Type II-N of unlimited area. The followingrestructions apply.

1. The height cannot exceed 75 feet.

2. All sides must be open for at least 50%of the exterior area of each tier.

3. The openings must be equally dis-tributed along each side.

4. No part ofatiercan be more than 200 ft.from an opening.

RECENT REVISIONS TO THE 1985 UBC

At the 1985 ICBO Annual Business Meet-lng the following changes relative to openparking structures were approved:

1. An open parking structure of Un FireProtected steel structure may be constructedabove an enclosed basement or first storyused for the parking or storage of motorvehicles.

2. The distance to adjacent property linesfrom exterior non fire rated walls has beenreduced from 20 ft. to 10 ft. and allows a onehour fire rated wall less than 10 ft. and morethan 5 ft. This will increase the instanceswhen the designer can get more sides openthus allowing greater use of unprotectedsteel.

Both of these changes will appear in the1986 supplement to the Uniform BuildingCode.

THE STEEL COMMITTEE OF CALIFORNIAAce & Stewart Detailing, Inc.Allied Steel Co., Inc.Artimex Iron Co., Inc,Bannister Steel, Inc.Baresel CorporationBethlehem Steel CorporationC A Buchen CorporationButler Manufacturing Co,Central Industrial Engineering Co.,Inc.

Cochran-lzant & Co., Inc.Dovell Engineering, Inc.The Herrick Corporation

Hoertig Iron WorksHogan Mfg., Inc.Industrial Steel Corp.Inland Steel CompanyInryco, Inc.

Junior Steel Co.Kaiser Steel CorporationLee & DanielMcLean Steel, Inc.Martin Iron Works, Inc.

Nelson Stud Welding Co.Palm Iron & Bridge Works

Pascoe Steel CorporationPittsburgh-Des Moines CorporationRiverside Steel ConstructionH.H. Robertson Co.Ross-Carter Corporation

Schrader Iron Works, Inc.Stockton SteelStott Erection, Inc.USS FabricationsUnited States Steel CorporationVerco Manufacturing, Inc.Western States Steel, Inc.

Northern California X • Southern California1250 Pine St. No. 301 • [ • • 9440 Telstar Ave. No. 103Walnut Creek, CA 94596 El Monte, CA 91731(415) 932-0909 (818) 444-4519

Funding for this publication provided by the California Field Iron Workers Administrative Trust.