Steel roof truss tutorialSOUTHLINE TEEL NDUTRIES www.southlinesteel.comSteel Roof TrussesAn Overview on Designing, Manufacturing, and Installing Roof TrussesMost building roofs can be framed with engineered light-gauge steel trusses which are manufactured from C-Shaped metal studs.
Prefabricated steel trusses oer a high-strength, light-weight roof system that can be installed quickly.
Roofs on more than 20% of all new commercial structures in the United States are built with light-gauge steel trusses.
In residential construction, wood trusses still dominate the industry, however light gauge steel roof systems are gaining ground in markets where additional strength is needed, or where greater free spans are required.Scissor Truss (shown) provide a dramatic ceiling eect.
is truss type will exert lateral forces on walls if not nstalled with a xed and slide end.A standard truss is a series of triangles - a stable geometric shape that is dicult to distort under load.
Regardless of its overall size and shape, all the chords and webs of a truss form triangles.
ese triangles combine to distribute the load across each of the other members, resulting in a light structure that is stronger than the sum of the strength of its individual components.However, for all the advantages, proper installation techniques and bracing are critical.
Additionally, trusses should not be modied in the eld without consulting the truss manufacturer.
Cutting a web member, for example will radically alter its strength.Truss Typesere are many truss types.
e most common types are shown on the facing page.Most roof trusses have webs that run at an angle between top and bottom chords.One exception is the gable-end truss in which webs run vertically.
ese trusses sit atop a buildings end walls and are more like a wall than a truss.
e gable-end truss must be supported along the entire length, and stabilized at the truss/wall intersection.
ere are a number of truss types that leave space for attic storage or living area.
In any roof truss, however, attic or living space comes at a price.
e bottom chord of the attac truss also acts as a oor joist and must be sized to accommodate a live load typically between 20 and 50 psf.
A roof truss with attic storage translates to roughly twice the weight of the same truss span with no attic.
For example, a fty-foot truss designed without attic storage may weigh between 300-350 lbs.
A fty foot truss designed with a 9 foot by 9 foot attic opening may weigh between 600 and 700 lbs.
Some truss manufacturers use a proprietary shape for the truss bottom and top chords.
A non-proprietary shape truss is any truss made from standard cold-formed steel shapes, usually C-Shaped stud material.
e standard and proprietary congurations have their advantages and disadvantages, Steel Southline Steel Industries
(850) 865-5344and its up to the building designer to determine which is the best choice.
Depending on the design, proprietary systems can sometimes utilize lighter sections for their chords and webs to satisfy the load requirements.
is weight advantage can translate into cost savings.
On the other hand, the lighter sections may not be as rigid as a standard truss, and consequently more dicult to install.
On-site repairs on damaged trusses can be more time-consuming since the proprietery shapes cannot be purchased from any source other than the manufacturer.Roof truss strength derives from the triangle shapes that comprise the truss itself.
Triangles are naturally rigid geometric shapes that resist distortion.
Top chords are in compression and push out at the heel and down at the peak.The bottom chord is normally in tension to resist outward thrust.The webs form smaller triangles that strengthen the overall structure and provide rigidity.
Loads on the individual webs can be either compression or tension - depending on the type of load.
Specifying a TrussWhen specifying a roof system with a truss manufacturer, the builder/developer should include the span of the roof, the pitch, the top-chord overhang, the end cut and sot-return details needed, and any gable-end preferences.
Also needed are special loading requirements such as storage Trusses are manufactured from C-Shaped Galvanized steel.
The strength of derives from its geometry, rather than weight..
Trussspanflyer05425 Cold-Formed Steel TrussesRoof Truss SpansEvery TrusSteel roof truss is a custom design based upon the unique load, span, bearing, use, and code criteria of a particular project.
The load / span tables shown below demonstrate only a tiny subset of the possible combinations available with TrusSteel CFS roof trusses.Typical Roof Truss Design SpansGeneral Notes:1)Spans shown in charts are in feet.2)Loads shown above are outlined as Top Chord Live Load (TCLL), Top Chord Dead Load (TCDL), and Bottom Chord Dead Load (BCDL).3)Top chord designed assuming structural sheathing offers lateral restraint.4)Bottom chords designed assuming lateral restraint spaced at 24 inches on center.5)Deflection limits: Live Load - L/360Total Load - L/2406)Trusses designed with ASCE7-98 wind- Wind speed shown in charts7)Some trusses above may require a piggyback truss due to excessive truss height.8)80+ as shown above means that a span in excess of 800 is possible.
Refer to TrusSteel Technical Bulletin TB991102 and a TrusSteel engineer regarding these spans.9)Scissor trusses designed with a bottom chord pitch equal to half of the top chord pitch i.e.a 6/12 top chord pitch scissor truss will have10)Designs may include multiple gauges for top and bottom chords as determined by the designer using Alpines VIEW engineering software.
Maximum chord gauges are 18 11)The truss web pattern used in the design is to be determined by the designer using Alpines VIEW engineering software.Load 1Load 2Load 3Load 420, 10, 10 psf30, 10, 10 psf20, 10, 10 psf30, 10, 10 psf90 mph wind90 mph wind140 mph wind140 mph windChord .Truss of Alpine Engineered Products, Inc.TrusSteel Division of Alpine Engineered Products, Inc.3208 Fisher Court
Arlington, TX : 817-483-15210211 5K05425 Cold-Formed Steel TrussesFloor Truss SpansEvery TrusSteel floor truss is a custom design based upon the unique load, span, bearing, use, and code criteria of a particular project.
The load / span tables shown below demonstrate only a tiny subset of the possible combinations available with TrusSteel CFS floor trusses.Typical Floor Truss Design SpansLoad 1Load 240, 10, 5 psf80, 10, 5 psfChord .Truss 3125, 10, 5 psfChord SizeTSC2.75TSC4.00O.C.
Truss Notes:1)Spans Shown in charts are in feet
.2)Loads shown above are outlined as Top Chord Live Load (TCLL), Top Chord Dead Load (TCDL), and 3)Top and bottom chords designed assumingstructural sheathing offers lateral restraint.4)Deflection limits:Live Load - L/480Total Load - L/3605)Chases are to be located in center of span.Maximum chase width allowed is 24 inches.6)Refer to TrusSteel Technical Bulletin TB971125 for TrusSteel floor truss design criteria.7)Designs may include multiple gauges for top and bottom chords as determined by the designer using Typical Duct Opening Sizes for 2.75 Chord Size Steel Floor TrussDepthPanel Duct Opening Sizes for 4.00 Chord Size Floor TrussDepthPanel SizeDepthAllowable Duct SizesALPINEDivision of Alpine Engineered Products, Inc.TrusSteel Division of Alpine Engineered Products, Inc.3208 Fisher Court
Arlington, TX : 817-483-1521All panel and duct opening size dimensions shown above are in inches..
Prod cat1PRODUCT CATALOGUE
Email: firstname.lastname@example.org INTERNATIONAL TRUSS SYSTEMS (PTY) LTD.Head Office 28 Bisset Road
P.O.Box 30456 Cnr.Hargan Street
Jet Park Jet Park
1469 South Africa Cape Town BranchUnit 3, 4 Tedrick Street
P.O.Box 1029 Kaymore Industrial
7561 Unit 4, Le Mans House
P.O.Box 25326 7 Le Mans Place, , KwaZulu Natal
Cape Town punched metal connector plates ..
7 TRUSS HANGERS
50 / 80 U TYPE HANGERS
45 TRUSS CLIPS
SWING FIX CLIP
STRUCTURAL TIMBER WASHERS
ADJUSTABLE POLE BRACKETS
HEAVY DUTY CLEATS
....20 TRI-NAIL SITE APPLICATION PLATES
21 ANTI-SPLIT PLATES
....25 SAW HORSE BRACKET
..............................................................26 4.5m ROLLER PRESS
....27 DOUBLE BLADED WEB SAWS
...28 TIMBER SPLICE PRESS
INTERNATIONAL TRUSS SYSTEMS (PTY) LTD PRODUCT CATALOGUE SOFTWARE PACKAGE Tri-Design 3000software, a trademark of
International Truss Systems (Pty) Ltd incorporates over 30 years of International development in the specification, design and manufacture of prefabricated timber roof trusses and has been adapted for South African conditions to comply with all relevant local and International Codes of Practice, Building Regulations and generally accepted methods of
good engineering practice.
Tri-Design 3000is a state of the art STRUCTURAL TIMBER ENGINEERING software package that has been written specifically for desktop computers.
It offers fully interactive graphical input of modern timber structures and roofs, to produce output ranging from design calculations to fabrication detailing and costing.
Advanced features such as block to block building jump facilities for separated buildings and any combination of rectilinear, skew and splayed walls makes the ROOF INPUT module an industry leader.
A mouse driven graphical query facility allows effortless checking of correctness of input dimensions on even the most complicated of building shapes and any errors or changes can immediately be corrected using the MOVE NODE facility.
This enormously useful function is ideal for changing the quoted plan dimension to actual site dimensions once a quote becomes an order.A library of Standard Shapes and House Types is offered during ROOF INPUT to facilitate unrivalled speed of input on commonly used building shapes.International Truss Systems attention to technical excellence is borne out in the HIP EDITOR.
Every single type of hip used in South Africa has been specifically incorporated in the option, to allow limitless flexibility and maximum user friendliness to every estimator and Truss Plant Manager, irrespective of any particular hip system preference.The user even has the option of building his own hip types.Tri-Design 3000with its powerful features of zoom, windowing and 3D rotation, from any elevation or angle, enables the user to view the roofscape from all combinations of direction and distance.
It comes complete with its own GENERAL DRAFTING PACKAGE (GDP) thus eliminating the need for expensive add on costs of stand alone CAD/CAM systems.If required, it can also be linked to all major CAD software, to produce engineering drawings of the highest quality, with the minimum amount of time and effort.Any combination of roof plots, 3D views, zooms into congested areas, truss and girder cutting and plating details as well as over 100 standard bracing and erection details, can simply be plotted or printed onto a single drawing sheet within seconds and without any actual additional draughting work.International Truss Systems (Pty) Ltd policy is to constantly improve all products.
In line with our policy, information on this document is subject to change without notice.
For further information on the products please contact International Truss Systems (Pty) Ltd
REVISION PAGE 05/2002 1
Tri-Design 3000 incorporates a stand alone BEAM design module that allows the user to design structural timber beams using solid sections, Superjoist plated sections or laminated timber Glulam beams.
Specials and user defined sizes can also be input.Any combination of loads can be input and the output includes full calculations, stress analysis and deflection criteria.Tri-Design 3000 also boasts SUPERCHORD.
It is a unique feature in the truss design module which optimises timber selection in complex non-standard trusses, such as attics and top and bottom chord extensions of supported trusses.
SUPERCHORD increases the depth of the supporting member through an additional member being plated in-plane over the required design bays, thus creating a SUPERCHORD.
Tri-Design 3000 comes complete with C.Q.P.S.or Client Quote Processing System which is a sophisticated but easy to use database, which tracks either projects, clients or sales staff, or any combination of the above, to produce useful management and sales statistics and reports.
Tri-Design 3000 also offers SUPERFAST, which is a rapid input/output routine in the truss design module for quoting on standard truss types and load combinations without having to input full roof layouts.
This allows rapid comparisons of the cheapest of say 3 truss types, if no ROOF INPUT is required.Through many years of development, testing and user feedback, the package has achieved its main aim.
It is as user friendly as possible so as to be an essential tool to a broad spectrum of users, ranging from junior estimators to senior structural engineers.
It also has its place as a management tool in the