Flitch Plate Design

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5 Flitch Plate andSteel I Beams

NAHB BEAM SERIES

NationalAssociation of ome Builders15th and Streets N.W.Washington, D.C. 20005


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The NAHB Research Foundation, Inc., prepared the contents of thi s publica tion and made it available toNAHB for publication and distribution .The NAHB Research Foundation, Inc., is a wholly owned subsidiary of the Association that carries outNAHB-sponsored research programs. It also performs research and development for private manufac-turers of building materials and equipment and for departments and agencies of the Federal Government.

Copyright 1981 by theNational Association of Home Buildersof the United States15th and M Streets, N.W.Washington, D.C. 20005

Al l rights reserved. No part of this book may be reproduced or utilized i n any form or by any means, elec-tronic or mechanical, including photocopying and recording, or by any information storage and retrievalsystem without permission in writing from the publisher.When ordering this publication, please provide the follow ing information:TitlePriceQuantityNAHB membership number (as it appears on the uilder label)Mailing address (includ ing the zip code)


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Contents IntroductionThe NAHB Builders Beam Manual was originall y

published in 1964 by the NAHB Journal o Homebu i l d i ng (now BUILDER Magazine). Since 1964,many changes have been made in lumber sizes,species, plywood grade names. grade designationsand allowable stresses. Changes have also occurredin structural steel shapes and plates. These changeshave made the design tables contained in the origi-nal manual obsolete. This revision updates andgreatly expands the number of designs available inthe original edition.

In the housing field structural engineering hasproduced a variety of fabricated beams. In selectingbeam types for this manual, the following properties

Introduction 3H o w To Use This Manual 4Flitch Plate Beams 8

Nail and Bolt Spacing 9Material Requirements, Flitch Plate Beams 10Beam Cost Estimate Sheet 10Beam Length in Feet 11Index to Steel Fli tch Plate Beam Designs 12Index to Steel Shape Beam Design 14Allowable Loads Tables, Flitch 15

Plate BeamsSteel I Beams 95 were sought:

Beam Cost Estimate Sheet 95 Low costEfficient use of materialsLight weightEase of fabricationSimplified installationReadily available materials

Thecomplete manual contains designs and instruc-Wo o d BeamsPlywood I-BeamsPlywood Box BeamsSteel-Wood I-BeamsSteel Flitch Plate BeamsStructural Steel Shape Beams

Allowable Loads Table 96

tions for the following beam types.


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H o w To UseThis ManualThe beams in this manual were designed in

accordance with accepted engineering practice toprovide maximum efficiency f or the intended use.The NAHB Research Foundation, Inc., has preparedthis manual to consolidateexisting nformation, addnew information where necessary and provide build-ers with a direct method of determining the appro-priate and economical structural beam for a specificdesign.

Many actorsare involved in determining the mostsuitable beam for a given set of design conditions.This section includes-A discussion of the scope and im itations of theinformation presented

A description o f simplified design procedureswhich may be followed to determine loadings,A material estimating guide and a beam costestimating form design.

divided by the clear span length of the beam in feet.In cases where a few concentrated loads exist, amethod is provided below to convert these con-centrated loads to equivalent uniform loads. Thebeam design tables as given can be used with th isinformation.

Conversion FactorsConcentrated Loadsfor Cases of Symmetrical

The tables are computed. for a uniform load of wpounds per foot extending down the length of thebeam (f ig . 1). This conditi on is not always realized.For example, a 12 foot beam carrying trussesspaced 2 feet apart is not subjected to a uniformload but rather to 5 concentrated loads (fig. 2 . ThisWhen properly selected and installed, uSeS of

these beams have no limi tations provided the load-ings are in accordance with the design conditions.All beams are assumed to be protected from expo-sure to the weather. The manual includes spansfrom 12 to 20 feet. A few common examples ofbeams used for these spans are garage door head-ers, headers for large windows and sliding glassdoors, substitutes for load bearing partitions, ridgebeams for cathedral ceilings and basement girders.

fact does not invalidate the tables, but it doesrequiren alteration of the load value by a conver-sion actor. Chart 1 provides onversionactors forall conditions of symmetrical concentrated loads.When a built-up beam with a thin web is used tocarry concentrated loads, adequate stiffeners andweb reinforcement must be provided.

Design InformationA l l the allowable design loadings in the tables

were computed on the basis of a beam over a simplespan subjected to a uniform load. (the most commonconstruction in resident a buiIding

Any span with eight or more equal, evenly spacedconcentrated loads can be assumed to be subject toa uni form load. (For example, a 16-foot span withloads 2 feet on center, or a 10-foot 8-inch span withloads 16 nches on center can be considered subjectto uniform load.) The magnitude of this uniformload per foot is the total load acting on the beam


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The allowable uni form loads per beam foot in thetables are computed on the basis of bending stress,horizontal shear stress, ro lling shear stress (plywoodbeams only), and deflection. The governing values,also given in the tables, are the smallest allowableload values resulting from these computations. Theindividual beam weights have already been sub-tracted so that the allowable uniform load in pounds

per foot is the design live load. The deflection of allbeams is limited to the lesserof 1/360 of the spanor1/2 inch.

The allowable lumber stresses are taken fromDesignValues for WoodCons t r u c t i o n a supplementto the 1977edition of NationalDesign pecificationfor Wood Construct ion by the National Forest Pro-ducts Association. Allowable steel stresses are taken


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from the Cold-Formed Steel Design anual pub-lished by the American Iron and Steel Institute.Allowable plywood stresses and design propertiesare taken from Plywood Design Specification, re-vised edit ion April 1978, by the American PlywoodAssociation. Steel structural shape propert ies andallowable stresses are taken from Manual of SteelConstruction, published by the American Instituteof Steel Construction, Inc.

Because of their complexity, special problemssuch as lateral buckling and web buckling are notdiscussed in this manual. However, adequatewebstiffeners should be provided in all types of beamssusceptible to web buckling, such as fabricatedplywood box or I-beams and the steel-wood beam.Lateral beam stability is rarely a problem in rest-dential construction: but f little or no lateral restraintfrom sideway movement is present, the allowableload values obtained from the tables should bechecked by an engineer to insure that lateral buck-ling is not critical.

Dead The weight of all permanent constructionin a building.Design-Total load which a structure or memberis designed t o sustain safely without exceedingspecified deformation.Live The weight of all moving and variable loadsthat may be placed on or in a building such as snow.wind, occupancy, etc.Uniform An average load applied uniformly

over a floor, roof or wall or a long a beam or girder.Two typ ical examples of beam applications and

the methods or determining the appropriatedesignloads a re given below.

Design TablesFour variables are considered in the design tables:the beam span, the beam depth, the beam designload, and the beam type. At least two of these factorswill be known or can be determined, at least one willbe unknown.

Proper use of the design tables will prov ide beamdesigns, several of which are available for any spe-cific beam requirements, which are structurallyadequate. Probably the primarycriteria fordetermin-ing which of these beams is best suited for the jobwill be the total cost. However, factorssuch as depthof beam, availabilityof materials, easeof fabrication,weight of beam and installation, and architecturaldetails can influence the final selection.

In Fig. 3 the roof trusses are designed to supportlive and dead loads. In this case, the header supportsendone of the roof trusses.The design load on theheader is determined by comput ing the truss reac-tions caused by the roof live and dead loads. Thefollowing equation can be used to determine theroof load that must be supported by the header:

w in pounds per footof beam = 1/2 truss span(including overhang) in feet times roof live plusdead load in pounds per square foot.

I f less than eight trusses bear on the header, use themethod described earlier for comput ing wExample

Roof truss span ( including overhang)Roof live loadw = truss span x roof live and dead loadsw = 1/2 24) x (30 + 5w = 420 pounds per foo t of beam

Determining AppropriateDesign Loads

The design tables can be used properly when thedesign load on the beam is known. An engineeringcalculation is required to determine the live loadsthat a beam must support. In residential designmany simplifying assumptions normally made re-duce the number of calculations required. Accept-able methods of determining the beam design loadsfor various condit ions are discussed in this section.

The loads acting upon a structure are defined inHUD Minimum Property Standards for One- andTwo-Family Dwellings as follows:oadsConcentrated A load concentrated upon a speci-

fied small area of a floor. roof, wall, or othermember.

24 ft.30 psf

Roof dead load 5 psf

Garage Door Clear Span Opening 16 FootIn this case, since only seven trusses bear on the

header span, theconversion formula i n Chart 1 mustbe used. The total load on the beam i s 16 x 4206720 Ibs. The equivalent uniform load is:


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With this answer (480), adequate designs can be Many factors determine the final selection of abeam. These factors include depth requirement,labor rates, material costs. availability of materials,fabrication facilities, connection details, and architec-tural considerations. Most of these factors can beeasily determined on the basis of preference andarchitectural considerations. Cost will probably bethe final basis for selection.

Material EstimatingTo simplify the work of estimating costs of beams,

the following tables give calculated quantities ofmaterials for the beam designs given. These quanti-ties are reduced to the most convenient un its for thepurpose of pricing. For example, lumber is given inboard feet, steel in pounds, and plywood in thenumber of 4 x 8-foot sheets required. Some materialsin the beams, such as the number of nails and theboard feet of stiffeners in a plywood box beam, arenot susceptible to tabular expression. Therefore,these must be computed individually for each beam.

selected from the design tables in this manual.Beam Supportinga Floor ConstructionFrom fig. 4 , L = the distance. center-to-center,between beams.

Each beam supports the load on a section extend-ing one half the distance to the next beam on eitherside. The load acting on a one-foot strip of thissection, taken at right angles to the beam, is the loadon the beam in pounds per foot.

ExampleConsidering the floors illust rated in Fig. 4.Loads ive

DeadTotal

40 psf10 psf5 psf

Load on the center beam = L (ft.) x 50 Ib./ft. =50L Ib./ft.


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Flitch Plate BeamsA flitch plate beam consists of a steel platesand-

wiched between two pieces of lumber. The beamderives most of its strength and rigidity from theprevent buckling of the steel. The components are

FabricationThe basic fastener spacing or each web thickness

the fastenersalong the top edge of the beam.Alongsteel plate, and the lumber sides provide bracing tojoined with hardened nails in the lighter membersand with bolts in heavy plate members. Since it iscommon practice or many steel suppliers o furnishsteel plate in even inch widths, and 2 x hrough 2 x16 umber comes in even inch depths, he designsare predictedon the steel flitch plate being inchless in depth than the wood members.

is given in the table below. This distance applies tothe bottom edge the basic spacing is doubled.Alsotwo fasteners are placed at each end. For the lightgage members (12 and 14 gage), the fasteners canbe driven n with a minimum of difficulty. A 32-ouncehammer was found to be desirable or this purpose.In the heavier members, it i s necessary to have thebolt holes punched or drilled in the steel plate andwood sides. See Fig. 5 for the basic fastener layoutand Fig. 6 for the suggested abrication procedure.Selection of Correct Beam

The numbers in the tables give the design load inpounds per foot that each beam will support. Thefirst column gives the lumber size. The secondcolumn gives steel thickness and the third columngives approximate beam weight in pounds per footof beam length. The columns in the table give the

Pl a te Thickness Bas ic Spacingaximum of inch. The Index to the Flitch PlateBeam Designs are given on pages 12 through 14.1 4 gage 3 i n c h e sesigns are included for four grades of ten com-monly available species of lumber ranging from 2 x

4 inchess through 2 x 16s. 1 2 gageMaterials 1 /8 i n c h 5 inches

1 4 inch 10 inches3 8 i n c h 15 inches

7 16 inch 18 inches1 2 inch 20 i n c h e s

Trade name, Independent Nai l and Packing Company.Bridgewater,Massachuset ts

ail and Bolt Spacing

The side pieces are continuous nominal 2 umberof the depth and species-grade combination for theparticular design chosen.

The steel plate shall consist of a single piece ofhot rolled commercial grade steel with a minimumyield of 33,000 psi.

The 12- and 14-gage (0.105 and 0.075 thick)flitch plate beams can be fabricated with 3 x 0.148electro-zinc plated, hardened fluted Screwtite*masonry nails or equivalent.

The 1 8 through flitch plate beams are heldtogether with American Standard Regular boltsand nuts. A flat washer is used on each side.


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Steel I-BeamsOccasionally in residential construction, problems

are encountered where the loads are too great, orthe space available is too small, to permit the use ofa solid wood o r build-up beam. In these cases, oneof the hot rolled structural steel shapes will usuallysuffice. Therefore, the table on page 96 gives theallowable line loads for several of the lighter, rolledsteel shapes.

Selection of Correct BeamThe numbers in the table give the design load, inpounds per foot, that each beamwi l l support. These

loads were computed in accordance with AmericanInstitute of Steel Construction (AISC) criteria forbending and-deflection. The beam weight isa lreadyincluded in the calculations.

The numbers in the top horizontal line of the tablegive the clear span distance in feet. The first verticalcolumn gives the AlSC designation. The secondvertical column gives the beam dimensions. Thecolumns in the table give the maximum load inpounds per foot that each beam will safely support,with the FHA deflection limitation of 1/360of thespan, or a maximum of inch.


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Flitch Plate Design