2. Pebs Manual

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PEBS MANUAL

Building for Life

PEB STEEL GROUPPre-Engineered Buildings

Jan, 2007


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INTRODUCTION

The Product Digest Manual is a central source of technical and non -

technical information, concerning Pre-Engineered Buildings products.

This manual is intended for sales engineers, sales support and engineering

staff. It provides comprehensive information concerning questions often

asked by PEB Steel customers, who are not familiar with our standards and

practices.


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PEBS Manual

Contents

1. APPLICATIONS OF PRE-ENGINEERED BUILDINGS ....................................................1

2. PLANNING AND OPTIMIZING THE PRE-ENGINEERED BUILDINGS..................12

3. DESIGN CODES............................................................................................................... ......25

4. DESIGN ENGINEERING PRACTICES...............................................................................27

5. FABRICATION .......................................................................................................................38

6. COMPATIBILITY OF MATERIALS AND PERFORMANCE.... ....................................41

7. FINISHED BUILDING CARE .............................................................................................49

8. ERECTION...............................................................................................................................52


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Application ofPre-Engineered Buildings

1.1 Is the PEB functional and suitable?

The PEB concept was first originated in the United States of America after the World War

II, as one of the solutions to the demand of fast economic growth, and then transferred toother industrialized countries. It consists of a complete steel framed building system, with

pre-designed components to best suit the unique customer requirements. The final productis a complete building shell with sub structural systems including mezzanine floors, cranesystems, canopies, fascias and interior partitions. The end product is an attractive building

that can be finished internally to serve the required function and accessorize externally toachieve a distinctive architectural style.


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From excavation to occupancy, no other building system matches the pre-engineered

building in speed and value for those who demand quality at a reasonable price. PEBsystem plays an active role in converting complex and expensive structural steel buildingdesigns into simpler and more economically designed, without sacrificing the utility and

basic function of these buildings.

The PEB system offers multiple advantages to the end-user, the most notable are low initial

investment, fast construction time, low maintenance cost, large clear spans, infinite choiceof layouts, inherent resistance to earthquakes, ease of expansion and unique attractive

appearance.

If customer requirements cannot be satisfied by using the standard economical structural

systems, PEB system has the flexibility and capability of how to supply the customer withalternate building system as custom made. The PEB performance over the last years and

the booming business expansion which PEB industry has experienced lately,

unquestionably prove that the PEB components act together as a system, for maximumefficiency, precise fit-up, and indeed a high quality product. PEB industry is part of a

continuous thinking machine.

Setting up plans, targets and performance standards for the production of engineering work

and the development of new systems to improve and increase the product reliability, andpresenting a clear vision of the economy, diversity, versatility and esthetics feature of PEB

as an enormous advantage for this industrys growth.

1.2 What is the meaning of Pre-Engineering Building?

Pre-engineered should not be confused with pre-fabricated. The name Pre-engineeredbuildings was adopted for the following reasons:

Pre-set methods for connecting and welding (standardized connections).

Utilization of pre-determined stock sizes.

Optimized design, detailing and fabrication, resulting in most economical (lower weight)

and fast delivery (reduced engineering time and fabrication time).

1.3 What type of building the PEB can utilize the PEB system?

The PEB system has created a unique architectural approach that is conducive to the

release of innovative ideas in design and erection of buildings. This approach is supportedby numerous applications, major and minor, carried out by professional and highly skilled

personnel. Since 1946 more than 60% of single story construction building in the USA arePEB. The standard PEB product line includes over 1300 different components, which may

be custom designed and manufactured to fit customer requirements exactly.


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Applications of PEB include -but are not limited to- the following:

Industrial Buildings -Factories

Warehouses

Distribution CentersCommercial Showrooms

Sports Halls

Recreational BuildingsShade Structures -Gas Stations

Agricultural Buildings -Grain Storage

Institutional BuildingsAircraft Hangars

SupermarketsWorkshops

RestaurantsOffice Buildings

Labor Camps

Almost any one, two or three storied building.

The wide range of PEB applications give this industry the cutting edge of market share.

Nevertheless, PEBs have some limitations when exposed to more than the maximum span

and loads possible. Therefore, according to the building utility and types of applied loads,

the proper pattern of building can be selected, meeting the limitations and satisfying other

requirements induced by the customer.

For very special conditions, it is possible for the consultants to obtain direct advice from

Metal Building Manufacturers on the most economical framing solutions for his buildingrequirements. Some vital considerations that are required when selecting the building

application, such as design loads, width, bay spacing, eave heights, ...etc. PEB Steel

standards are as follows:

Design load is indicated to be : Live Load = 0.57 KN./m2

Wind Load = 130 Km/Hr, theseloads satisfy 95% of all the loading conditions usually required in most applications.

Bay spacing set at 9 m as the most practical. Bay spacing as low as 5 m and as high as 30m can be accommodated.

Eave heights as high as 30 m can be accommodated in special buildings. The eave height isa critical issue when selecting the type of building for the appropriate application.

The PEB system offers multiple advantages to the end-user, the most notable are low initialinvestment, fast construction time, low maintenance cost, large clear spans, infinite choice

of layouts, inherent resistance to earthquakes, ease of expansion and unique attractive

appearance.


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1.4 Why do the customer choose PEB instead of Conventional Structural Steel?

The term pre-engineered building (PEB), is well known to engineers who traditionally

design their buildings with conventional steel instead of built-up members used in the PEB

system.

The broad range of applications in the metal construction industry gives PEB an enormous

advantage over any other system. The PEB manufacturers capacity and capability to

design, supply and erect a building for any project requiring fabricated steel members,offer a time and cost saving solution to consultants who generally prefer to have one

contract, instead of sub-contracts, which make it difficult to control. PEB can be used even

where conventional steel has been typically dominating. Applications that PEB has gained

ground against over conventional steel structures are heavy industrial and commercialbuildings such as:

Large Manufacturing Plants

Mill BuildingsBuildings less than 5 stories

Warehouses

Office Buildings

The engineering work of Structural Steel fabrication, is limited to the estimation andpreparation of erection and shop drawings for fabrication of assigned projects, design is

rarely done by the manufacturer.

The following shows a comparison between PEB and Structural Steel, intending to

familiarize design groups with the basis of the PEB concept, its high versatility andpracticality, and the advantages to designers and consultants.


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Feature DesignCriteria

Pre-Engineered Steel BuildingsA.I.S.C., M.B.M.A., A.W.S, AISI

Conventional Steel BuildingsA.I.S.C., A.W.S., J.I.S., D.I.N.B.S.

Foundation Simple design, easy to construct and Extensive, heavy foundations required.

lightweight.

Delivery

Average 6 to 8 weeks. Average 5 to 6 months.

Building is supplied complete with Many sources of supply. Project

cladding and all accessories, including Management time required to coordinate

erection if desired, all from one source of suppliers and sub-contractors.supply. About 30% lighter through the

efficient

use of steel. Primary framing membersPrimary steel members are selected from

standard hot rolled I sections, which in

are (varying depth) tapered built-up plate Many cases are heavier than what is

sections with large depths in the areas of actually required by design. Members

highest stress. have constant cross-sections along the

Entire span, regardless of local stress

Secondary members are light gage (light magnitude.

weight) cold formed (low labor cost) Z

or C shaped members. Secondary members are selected from

Z purlins/girts can be lapped. Lapping standard hot rolled I and C sections,

reduces the deflection, and allows double which again are heavier than required.

thickness at the points of higher stresses

Sourcing &

Coordination

(support points).


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Feature Pre-Engineered Steel Buildings Conventional Steel Buildings

Design Quick and efficient since standardization

of P.E.B. has significantly reduced

design time. Basic designs are used over

and over. Specialized computer analysis

and design programs reduce design timeand optimize material required. Drafting

is also computerized with minimal

manual drawings. Design, detaildrawings and erection drawings are

supplied free of charge by the

manufacturer. Approval drawings may

be prepared within 10 days to 3 weeks.Consultant in-house design and drafting

time is significantly reduced, allowing

more time for coordination and review,

and increasing margins in design fees.

Since most of the PEB are pin-based, thecost is reduced due to smaller sections at

the base with smaller base plates andfoundations (in absence of moments).

Each conventional steel structure is

designed from scratch by the Consultant,

with fewer design aids available to the

Engineer. Maximum engineering

required on every project. Generalizedcomputer analysis programs require

extensive input / output and design

alterations. Drafting is manual or onlypartially automated. Much Consultant

time and expense is devoted to design

and drafting, as well as coordination and

review.

Accessories Designed to fit the system, with Every project requires special design for

Windows, Doors, standardized, interchangeable parts, accessories and special sourcing for each.

Ventilation including pre-designed flashing and Flashing and trims must be uniquely

trims. Mass produced for economy. All designed and fabricated.

available with the building.

Erection Easy, fast, step by step. Erection costs &time are accurately known, based upon

extensive experience with similar

buildings.

Slow, extensive field labor required.

Typically 20% more expensive than

P.E.B. In most of the cases, the erectioncosts and time are not estimated

accurately.

Architecture Outstanding architectural design can be Special architectural design requires

achieved at low cost. Conventional wall research and high cost.

and fascia materials, such as concrete,

masonry and wood, can be utilized.

Overall PricePrice per square meter may be as much

as 40% lower than conventional steel.High price per square meter.


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FeatureChanges

Pre-Engineered Steel BuildingsVery flexible, tailor made, acceptschanges and revisions easily. Future

expansion simple, easy and cost

effective. One supplier to coordinate

changes.

Conventional Steel BuildingsChanges, revisions & additions can bedifficult due to extensive redesign and

coordination among suppliers and sub-

contractors.

Performance All components have been specified and Components are designed in general for

designed specifically to act together as a possible use in many alternative

system, for maximum efficiency, precise configurations. Design and detailing

fit-up, and performance in the field. errors are possible in assembling diverse

The experience with similar buildings, in components into unique buildings. Each

actual field conditions world-wide has

building design is unique, so prediction

ofresulted in design improvements over how components will perform together is

time which allow dependable prediction uncertain. Materials which have

of performance. performed well in some climates may not

in other environments.

Responsibility Single source of supply results in total Multiple responsibilities can result in

responsibility for one supplier, including questions of who is responsible when

design liability. components do not fit properly,

insufficient material is supplied, or

materials fail to perform, particularly at

supplier interfaces. The Consultant

Carries total design liability.

1.5 Why steel for Low Rise Construction and not Concrete?

Here are just a few advantages why PEB is favored over reinforced concrete.

The shorter erection period permits an earlier recovery of capital. A wide spanning frame is

possible, providing large column-free interior spaces with a wider range of potential uses.

Steel structural members offer the absolute accuracy of dimensions and uniform qualitypossible.

Concrete has a very low tensile strength, requiring the use of tensile reinforcing. Forms are

required to hold the concrete in place until it hardens sufficiently. In addition, false-workor shoring may be necessary to keep the forms in place for roofs, walls, and similar

structures until the concrete members gain sufficient strength to support themselves. Form-

work is very expensive. Its costs run from one-third to two-thirds of the total cost of a

reinforced concrete structure, with average values of about 50%.


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The low strength per unit of weight of concrete leads to heavy members. This becomes an

increasingly important matter for long span structures where concretes large dead load hasa great effect on bending moments. Similarly, the low strength per unit of volume ofconcrete means members will be relatively large, an important consideration for tall

buildings and long span structures. The properties of concrete vary widely due to variations

in its proportioning and mixing. Furthermore, the placing and curing of concrete is not as

carefully controlled as is the production of other materials such as steel.

Other characteristics that can cause problems are concretes shrinkage and creep. Cost

comparison studies have revealed that the overall construction cost of structural steel

buildings is generally more economical than reinforced concrete structures.

The following is a table showing the most important advantages that favored the use ofPre-Engineered Steel Buildings instead of Reinforced Concrete Buildings.

Feature Steel Concrete

Fabrication Done in shop-controlled

conditions

Mostly done at site in variable

conditions

Material Specifications Precise and Fixed Variable, Non-homogeneous

Dimensions Precise and accurate

measurements

Potential for significant errors.

Capacity May carry up to 6 times its

weight

Carried load almost equal to its

weight

Material Foundations Lighter Variable

Erection Faster Slower

Clear Spans Larger Smaller

Buildings Height Higher Shorter

Changes Movable, Expandable Difficult to modify

Fire Resistance Needs more protection Good Resistance

Applications Industrial, Commercial Houses, Villas and Parliaments

1.6 What are the materials Specifications and Designs Codes that PEB Steel uses, and

do they comply with the internationally recognized Standard?

Pre-Engineered Building systems mainly make use of built-up sections, cold formed

elements as well as some hot rolled sections. PEB Steel follows universally recognizedcodes of practice in the analysis, design and fabrication of its products.

These codes are widely used by the construction and buildings design industries as

authentic source of tested procedures, and as basis for acceptable quality for design,

materials, fabrication and construction standards.


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All materials used in the fabrication of Pre-Engineered Building systems, are new, unused

and meet or exceed the physical requirements of the PEB system design and fabricationprocesses, as well in accordance with the materials manufacturers standards andprocedures. Our quality control department tests the material ordered for inventory to meet

the design criteria for strength and to ensure that these materials possess the qualities

(including weldability) required by the fabrication process of each specific component of

PEB system.

The procedures and calculations used in PEB Steel design and fabrication are made in

reference to the following codes:

Main frames members (Hot Rolled or Built-up) shall be designed in accordance with the

2005 edition of the American Institute of Steel Construction (AISC), as specifications forthe design, fabrication and erection of Structural Steel for Buildings.

Loads on all buildings are applied in accordance with the 2006 edition of the international

building codes (IBC)

Cold-Formed members shall be designed in accordance with the 2001 edition of theAmerican Iron and Steel Institute (AISI), as specification codes applied for the design of

cold-formed steel structural members.

All welding shall be done in accordance with the 2006 edition of the American Welding

Society (AWS) codes. All welders are qualified for the type of welds performed on thesteel members.

Manufacturing dimensional tolerances shall be in accordance with MBMA 2002.

The materials of the steel members used in the PEB manufacturing are conforming toAmerican Society of Testing Materials (ASTM) specifications or equivalent standards.


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PEB STEEL COMPLIANCE WITH LATEST INTERNATIONAL CODES

Loads on all buildings are applied in accordance with:

2006edition of the International Building CodeInternational code council, Inc (IBC)4051 West Flossmoor Road, Club Hill, IL 60478-5795, USA

Manufacturing and Erection tolerances are applied as per:

2002edition of the Low Rise Building Systems ManualMetal Building Manufacturers Association, Inc (MBMA)

1300 Summer Ave., Cleveland, Ohio 44115, USA

For Erection & Manufacturer Tolenrances

Hot rolled sections and built up sections are designed in accordance with:

2005 Manual of Steel Construction Allowable Stress Design

American Institute of Steel Construction, Inc. (AISC)

1 East Wacker Drive, Suite 3100, Chicago, Illinois 60601-2001, USA

Cold formed members are designed in accordance with:

2003Edition of AISI (North American Specification for the Design of ColdFormed Steel Structural Member)

American Iron and Steel Institute (AISI)

1000 16th Street, NW, Washington, DC 20036, USA

Welding is applied in accordance with:

2004American Welding Society (AWS D.1.1.04)

Structural Welding Code Steel Manual550 NW LeJeune Road, Miami, FL 33126, USA


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PEB STEEL STRICT DEFLECTION CRITERIA

Deflection StructuralMember Deflection LimitationLoad

Combination

1 Main frame rafters Span/ 180 Dead + Live

2 Roof purlins Span/ 180 Dead + Live

3 Mezzanine beams and joists Span/ 180 Dead + Live4 Top running crane (TRC) beams Span/ 600 Dead + Crane

5 Underhung crane (UHC) beams Span/ 500 Dead + Crane

6 Monorail crane (MR) beams Span/ 500 Dead + Crane

7

Relative deflection of adjacent frames

at point of support of UHC or MRbeam.

Bay/ 225 Crane only

8Relative deflection of UHC beamssupported by the same frame

Crane span/ 225 Crane only

Vertical

Deflection

9

Rigid frame rafters supporting UHC or

MR beams running laterally in the

building.

Bldg. Span/ 500 Crane only

1Main frame columns with eave height

(EH) up to 9.0 mEave height/90 Dead + Wind

2

Main frames supporting top running

cranes (TRC) or underhung cranes

(UHC)Eave height/100 All

3 Wall Girts Span/ 90 Wind only

4 Endwall wind columns Span/ 90 Wind only

Lateral

Deflection

5 Portal frames Eave height/ 90 Wind only


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Planning and Optimizing thePre-Engineered Buildings

2.1 What is the Configuration of Pre-Engineered Building?

The PEB building as shown herein consists of all columns, rafters (roof beams), bracing,

connection clips, end wall posts, roof purlins, wall girts, roof and wall sheeting, anchor

bolts, flashing, trim, etc. or as specified. The main building structure is comprised ofsingle gable interior rigid frames with either rigid or post and beam frames at end-

walls.


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The configuration of a pre-engineered building comprises of the following:

Standard roof slopes which can vary from 0.5 or 1.0 unit of vertical rise to 10 units of

horizontal base. Other slopes are available upon request.

Side-wall steel line is the plane of the inside surface of the side-wall sheeting. It is also theplane of the outside vertical surface of the eave strut. End-wall steel line is the plane of the

inside surface of the end-wall sheeting. It is also the plane of the outside surface of the

outer flange of the end-wall posts.

Building width which is the distance between the steel lines of opposite sidewalls.Buildings width does not include width of side-wall lean to buildings and side-wall roof

extensions. The width of a lean-to building shall be the distance from the steel line of theexterior side-wall of the lean-to building to the (side-wall or end-wall) steel line of themain building to which the lean-to building is attached.

Building length is the distance between the steel lines of opposite end- walls.

Building length is a combination of several bay lengths. End bay length is the

distance from the outside of the outer flange of end-wall columns to the center line ofthe first interior frame. Interior bay length is the distance between the center lines of

two adjacent interior rigid frame columns. Building length does not include the width

of end-wall wall lean-to buildings or end-wall roof extensions.

Building eave height shall be the distance from Finish Floor Line FFL (typically theunderside of the side-wall column base plate) to the top of the eave strut at the side-

wall steel line. The building clear height shall be the distance from Finish Floor Line

FFL to the underside of the lower rafter flange at the haunch (the connection of theside-wall column to the rafter).

2.2 What is the Standard Configuration of Pre-Engineered Building?

The term Standard refers to the most common Structural Systems. More than 80% of the

pre-engineered steel buildings supplied by PEB Steel utilize one of the standard

structural systems. The other 20% utilize other structural systems. The standard

systems are:

Single Slope SSMulti-Gable MG

Clear Span CS

Multi-Span MSSpace Saver SS

Lean-To LT

Roof System RS


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The standard configuration of PEB refers to information in the form of standard building

widths, frame clearance dimensions, design live load, design wind speed, columnreactions, and anchor bolt setting plan, that is useful for customer information purpose.

Although this section pertains specifically to the standard buildings, this information

may also serve as a guide to non-standard conditions.

PEB Steel standard design loads are:

Live Load (LL) = 0.57 kN/M,

Wind Speed (WL) = 130 Km/hr.

These loads are identified as standard because they satisfy the overwhelming majority of

loading conditions in our Asia although a 110 Km/hr wind speed is more than adequate

in most areas.

PEB Steel can and often does supply non-standard custom buildings without

additional charges for engineering work. Non-standard buildings differ from standard

structural systems in that they can have non-standard design loads, building widths, bay

lengths, roof slopes, eave heights, module sizes ...etc.

2.3 What is the most Economical Configuration of Pre-Engineered Building?

For some special conditions, it is advisable that the customer seeks the advice of a PEBSteel representative for the most economical framing approach for the building prior to

specifying the basic parameters. Experience has demonstrated that consultation with a

PEB Steel representative prior to fixing the parameters of a building often results in

overall building supply savings, that range from 5% to 20%.

The most economical configuration for a pre-engineered building is:

Bay Length:

A bay length of 9.0 M is used because it is the most economical in most PEB

Steel applications. However, 10.0 M bay lengths are gaining popularity and

acceptance because longer bays often result in savings to the overall projectcost as their use results in lower foundation costs (fewer rigid frames translates

into fewer footings). When bay lengths greater than 10.5M are required, open

web joist purlins are used. These permit bay lengths of up to 30.0 M.

Eave Height :

The eave height is a critical point when selecting the right type of building,

high attention should be paid to this issue. Eave heights as high as 30m can be

accommodated.


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PEB Steel pre-engineered buildings are custom designed to meet the exact requirements,

the basic parameters that define a pre-engineered building are shown below, any buildingconfiguration is possible but may require more engineering time and possibly longerdeliveries. Practically, any geometrical shape can be done. Those shapes vary as follows:

2.3.1 Single Slope SS (Mono-slope building)

Single Slope SS buildings are economical in spans that are less than 24 meters.

The most common customer requirements best suited for using Single Slope

buildings are:

Whenever rain water drainage is required to be along one side-wall of the building.

When the new building (the Single Slope building) is added directly adjacent to an

existing building requiring the designer to avoid:

a- The gutter drainage created by a valley condition along the

connection of both buildings.

b- Loading the existing building. For buildings wider than 24M, it is common tospecify a gable roof from economic as well as aesthetic considerations. Single

Slope buildings may be designed as either Clear Span or Multi-Span.


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2.3.2 Multi-Gable MG

Multi-Gable MG buildings consist of two or more gable buildings sharing a

common side-wall column. Although Multi-Gable buildings are commonly used inmany regions of the world, PEB Steel recommends the use of Multi-Span buildings

in lieu of Multi-Gable buildings. We discourage Multi-Gable applications for the

following reasons:

Drainage at the valley between gables requires frequent maintenance to prevent

accumulation of residue such as sand, etc.. that must be removed or risk overflow

leakage in the building interior.

Access to valley gutters for cleaning is more cumbersome than accessing eave

gutters. This access requires maintenance traffic on the roof risking sheeting

deterioration or damage.

In long Multi-Gable buildings, down pipes have to be provided inside the buildings

with horizontal drain pipes or concrete channels have to be embedded in the concrete

along the length of the buildings under each valley gutter to carry the water from the

roof to an exterior location. The construction of such a water draining system is

expensive and risky, since blockage of these pipes can cause flooding inside the

building.

Wind bracing design for Multi-Gable buildings requires the provision of wind

bracing members between the interior columns of the Multi-Gable buildings, along

the length of the buildings. If diagonal bracing is not allowed because of interior

access requirements, this necessitates the inclusion of expensive portal bracing.

In modern mature steel building markets, particularly in the USA, Multi-Gable

buildings are rarely specified or constructed. Instead more practical low

maintenance Multi-Span MS buildings are specified.

This is now possible due to the availability of:

High speed computing equipment.

Efficient analysis/design software.

Automated welding equipment.

Multi-Gable buildings may be designed as either Clear Span or Multi-span.


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2.3.3 Clear Span "CS" buildings shall have a gable roof with vertical side-walls and end-

walls. Interior bay frames shall be clear span rigid frames typically utilizing tapered

columns and rafters.

Clear Span rigid frame is appropriate and economical when:

Frame width is less than 60m.Eave height is less than 10m.


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2.3.4 Multi-Span "MS" buildings shall have a gable roof with vertical side-walls and end-

walls. Interior bay frames shall be rigid frames typically having tapered exteriorcolumns, tapered rafters and square tube interior columns generally hot-rolled tube

section pin connected at top with the rafter (builtup straight column moment connected

is more viable when lateral sway is critical) .

Multi-Span rigid frame is the most economical solution for wider buildings (width >

60m)for the largest buildings such as warehouses, factories and distribution centers.

The most economical modular width in multi-span buildings is 24m .

The disadvantages of such framing system include:

Possibility to differential settlement of column supports.

Locations of the interior columns are difficult to change.

Longer unbraced interior columns especially for wider buildings.

2.3.5 Space Saver "S.S." (also known as main-streeter ) buildings shall have a gable roof

with vertical side-walls and end-walls. Interior bay frames shall be clear span rigid

frames having constant depth columns and tapered rafters, typically with horizontal

bottom flanges.

Selection of space-saver is appropriate when:

The frame is between 6m and 24m and eave height does not exceed 8m.

Straight columns are desired.

Roof slope equal to 0.5:10.


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2.3.6 Lean-to "LT" buildings shall consist of outer side-wall columns and simple span

rafters attached to the side-wall columns or the end-wall posts of the main building.

Lean-to columns shall be of constant depth. Lean-to rafters may be tapered or of

constant depth.

Lean-to is not a self-contained and stable framing system rather an add-on to the

existing building with a single slope. This type achieves stability when it is

connected to existing rigid framing. Usually column rafter connection at knee is

pinned type, which results in lighter columns.

Generally, columns and rafters are straight except that rafters are tapered for larger

widths (greater than 18m ). For clear widths larger than 18m tapered column withmoment resisting connection at knee is more economical.

Lean-to framing is typically used for building additions, equipment rooms and storage.


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2.4 What is the Maximum Possible Span & Loading Capacity?

Spanning is a key issue when selecting the appropriate type of building for the customerapplication, important design limitations take part of the selection process, although PEB

challenge was to overcome certain engineering obstacles, but the evolution has proved

over the years the capability of engineering in improving the results of larger spans and

heights.

The maximum spans created by PEB structural systems are:

Clear Span CS, maximum practical width = 100 m.Single Slope SS, maximum practical width = 50 m.

Multi-Span MS 1, maximum practical width = 100 m.

Multi-Span MS 2, maximum practical width = 150 m.Multi-Span MS 3, maximum practical width = 180 m.

Multi-Gable MG, maximum practical width = 100 m.

Lean To LT, maximum practical width = 24 m.

Roof System RS, maximum practical width = 36 m.

However, other structural system spanning capability is possible, but it should be

approved by the engineering department.


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2.5 Where to use Jack Beams?

Jack beam is a horizontal structural member that can be straight or tapered built-up

sections designed to support vertical and horizontal loads.

Some buildings require bay spacing more than 11m in order to have a greater clear space

at interior of building in multi-span buildings. Such situation can be handled by

providing Jack Beam that support the intermediate frames without interior columns.

Jack beam is also required when a bay longer than 11m is desired along the length of abuilding. The use of this frame allows bay lengths of up to 22m.


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2.6 Does the eave height affect the price?

The eave height is governed by:

Clear height which is the vertical dimension from the finished floor level to the lowest

underside point of the rafter (head clearance ). Mezzanine clear height below beam andabove joist. Crane beam / Crane hook heights.

We have to minimize the eave height to the bare minimum requirement since the eave

height affects the price of the building by adding to the price of sheeting , girts and

columns. If columns are not braced, eave height affects the frame weight significantly.

If eave height to width ratio becomes more than 0.8 then the frame may have a fixed

based design in order to control the lateral deflection.

2.7 Does the Building orientation effect the price?

Building should be oriented in such a way that the length is greater than the width. This

will result in more lighter frames rather than less heavy frames.

Larger width will increase the bracing forces too.


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2.8 When a rigid frame at the end wall is required?

A rigid frame at the end wall is required when:

End wall is fully open for access.

Building has a crane that runs up to the end of the building.

Building will have a future expansion at the end wall.


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2.9 How to determine the total height of fascias?

In order to cover the ridge with the fascia :Fascia with bottom curved : Ridge height + 1m.

Fascia without bottom curved : Ridge heights + 0.5m.


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Design Codes3.1 Are the codes used in the design of PEB accepted ?

The codes used for the design of PEB system by PEB Steel are internationally

recognized, such as American Institute of Steel Construction (AISC), International

building code (IBC) Metal Building Manufacturing Association (MBMA), American

National Standards Institute (ANSI), American Society for Testing and Materials

(ASTM) and American Welding Society (AWS), in addition to Uniform Building

Codes (UBC), British Standards (BS), and the Japanese Industrial Standards (JIS) used

when special job design requirements are requested by the customer.

3.2 Why these codes are selected?

As the PEB Steel system was first originated in the United States, the metal buildings

construction has gained acceptance as the preferred method for all types of low-rise, non

residential building projects. Today, in the US alone, the PEB Steel industry accounts

for over 50% of all construction in this category using the PEB Steel approach. The

results are high quality, attractive buildings with higher reliability, flexibility, and lower

life cycle costs than the alternatives.

The PEB Steel industry has developed a system to be compatible with ordinaryconstruction materials. The design practice over the years reflects the good results of

using the American Codes, these codes may differ in wording and presentation to other

internationally recognized codes. However, end-users can request the application of

other codes for their specific projects, experience in using such codes revealed full

satisfactory results, this is due to the flexibility of PEB Steel standards which gives a

full bearing responsibility of the structural stability of the building.

PEB Steel letter of design certification lists the design criteria including design codes

and standards, design loads and other design information supplied to the customer, and

certifies that the structural design such as magnitude, location of design loads, support

conditions, material properties and the type and size of major structural members, do

comply with the requirements of the contract documents.

3.3 What is the difference between American codes and others ?

The purpose of a building code is to provide standards for the design and construction

of buildings and structures. Thus, in its simplest contest, a code is intended to provide

for the safe use of buildings and structures under normal conditions. Our standard

design codes address other areas of particular industry applications such as more

sophisticated design procedures and more accurate design loads, tailoring to best suit


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specific applications (in terms of gross geometry, framing considerations, etc.).

It is worth to point out the difference between the American Codes and other codes

(British Codes), which are:

Other Codes apply structural steel codes over the PEB system, which is not a

recommended practice.

American codes provide more economical and flexible design procedures, resulting in

less weight of the sections, without sacrificing the quality or safety requirements of thebuilding.


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Design / EngineeringPractices

4.1 What is PEB Steels Design Criteria about the Wall and Roof Bracing ?

The two main stresses on a member under torsional loading are (1) transverse shear

stresses and (2) longitudinal shear stresses. These two stresses combine to produce

diagonal tensile and compressive stresses which are maximum at 45 degree. At 45

degree, the transverse and longitudinal shear stresses cancel each other. Therefore,

there is no twisting stress or action on a diagonal member placed at 45 degree. In a

frame made up of flat members, the transverse shear stresses cause the longitudinal

members to twist. The longitudinal shear stresses cause the cross braces and end

members to twist.

On a diagonal member at 45 degree to axis of twist, the transverse and longitudinal shear

stress components are opposite in direction to each other and cancel out, but in line with

this member they combine to produce diagonal tensile and compressive stresses which

tend to cause bending rather than twisting. Since these two shear stresses cancel out,

there is no tendency for a diagonal member placed in this direction to twist.

It is important that the diagonal members have a high moment of inertia to provide

sufficient stiffness, so there will be no failure from local buckling under severe torsional

loads.

4.2 Why Cables and Rods are allowed by the Codes to be used in lieu of Angle Bracing?

The frame of PEB is carried up true and plumb within the limits defined in the Code ofStandard Practice of the American Institute of Steel Construction. Bracing shall be

provided wherever necessary to take care of all loads to which the structure may be

subjected. This is done by either way of Rod bracing, Cable bracing or Angle bracing.

The factors which determine the use of either one is:

Economy (cables and rods).

Ease of Connection (cables and rods).Ease of Alignment and erection (cables and rods).

Cables and rods are designed for tension force only.

Crane with capacities exceeding 15MT (Angles Only).

Special Design Code Requirements.


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4.3 Why PEB Steel do not use Stiffeners in the main frames ?

The efficient use of materials is the first essential rule to lower cost designs. One way to

achieve such efficiency is to design the built-up members accordingly to be able to take

the loads applied, and avoid to the maximum extent possible the use of lighter-gage plate

that is fabricated, and added to the member as stiffener where necessary for the required

rigidity.

Stiffeners are sometimes used in order to more nearly match the moment requirements of

the frame. This is done through the increase of the web thickness, by producing a deeper

section in the region of maximum moment, extending back until the moment is reduced

to a value which the built up section is capable of carrying,.

Regardless of how flexible or rigid the stiffeners are, the increase of the web thickness

will increase the stiffness of the whole plate section, by increasing the moment of inertia

(I) of the member section.

Stiffeners are sometimes required on members in line with the compression flanges,

which act against them to prevent crippling of the web where the concentrated

compressive force is applied.

In figuring the maximum bending stress in this built-up section, the member may by

treated as a simply supported beam, and designed with sufficient moment of inertia (I) towithstand whatever load is applied without having to use the stiffeners.

4.4 When do we use sag arrestor / sag angle for walls and roof?

We use sag arrestor when using special Roof (No screw roof). And we use sag angle

when using normal Roof (Roof use screw for fastener). Beside, PEB always supply 2

lines sag arrestor (or sag angle) in each bay. Thats why PEBs roof is stronger thanothers.


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4.5 Why the Axial Load from the Walls Bracing is not included in the Design

Package?

It has been our practice of not including the axial loads from the bracing in the design

calculations. However, those loads do not control the design of the building, knowing

that PEB Steel engineering practice of the design, is to check such loads, and include

them wherever the design engineer feels necessary to do so. Also engineering

department can furnish these loads upon request of the customer in an additional design

sheet.

4.6 Why PEB industry use the standard of single side welding for the main frame?

It has been our practice since the introduction of built up sections in the PEB system of

one side welding for the main frame components (web and flanges). It is a common

welding procedure among the PEB manufacturers.

The use of single-sided fillet welds in statically loaded pre-engineered buildings is a

routine operation that has not resulted in adverse performance over the last decades in

the USA. As the single-sided welds is a design question, where the loads transfer from

web-to-flange required is fully achieved, except where crane beams and brackets are

present, there is a need for double-sided fillet welds.

This issue has been addressed by the American Welding Society (AWS), stating thecodes do not prohibit such practice, and it is a matter of design, leaving the application

to the engineering judgment.

The progress made in recent years in automatic welding, has made shop fabrication of

built up members quick, assuring high quality welds by enabling the welding head to be

put into proper alignment with the joint of the member in a matter of seconds. This

alignment is maintained along the length of the joint during welding.

The welding procedures adopted by PEB Steel are considered for the extreme

situations. The design engineer checks and design the welded sections for the stresses

occurring due to the special loads or special design requirements.

Many different welding processes may be used to produce metallurgical bonding,

through the application of pressure or fusion. The submerged arc welding process

which PEB Steel adopted in the fabrication of the built-up sections, is the most widely

used source of energy for the intense heat required for fusion welding. This is by

definition a fusion process that reduces the surfaces to be joined to a molten state, and

then allowing the metal to solidify reaching a complete metallurgical bonding, as

adherent to full weld penetration of the plates.


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In the submerged arc welding, the intense heat reduce the metal to almost liquid state by

an electric arc. This tremendous heat at about 6500 degree Fahrenheit, melts the two basemetal (flange and web), bringing them to one solid homogeneous piece by moving the

electrode along the joint to be welded.

4.7 Why Design Calculations do not show the size of the welds used by PEB Steel ?

As PEB Steel design procedures and policies developed its own standards and adoptedmeasures to avoid any technology transfer issues to outsiders, the welding procedures of

PEB Steel are an internal protected practice not intended to reveal to the customer of how

things are done. Therefore, the weld size is comprised within this context, and salesengineers should be aware when and to whom are releasing this kind of information, only

unavoidable in cases where the customer insistence is affecting the companys benefits,and even though prior consultation and approval from engineering is required for this

issue. PEB Steels engineers do check and design the welds for the stresses occurring dueto special loads or design requirements.

As stated in the AWS D1-1-1996, in reference to the fillet weld size, the minimum weld

size is dependent upon the thicker of the two parts joined, except that the weld size neednot exceed the thickness of the thinner part (see table below). This fillet welds and partial

penetration groove welds joining the components of the built up members, such as

flange-to-web connections, is designed to take the tensile and compression stress of these

elements parallel to the axis of the welds.

FILLET WELD ONE SIDE WEB FLANGE

Thickness of Thicker Plate Minimum Size of Fillet Weld (Single

Pass)

UP TO 6.4 mm 3 mm

6.4 TO 12.7 mm 5 mm

12.7 TO 19.0 mm 6 mm

ABOVE 19.0 mm 8 mm

Note: Fillet size need not exceed the thickness of thinner part to be joined.

4.8 Is Bolt Tensioning required for primary connections?

Bolt tensioning must be employed in connections of any of the two following cases:

a - Slip critical joints, where damage can occur to the finishing material.

b- Connections subject to direct tension.


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In any of the above two mentioned cases, the snug tight method is recommended by the

AISC as the best tightening procedure to be used in order to achieve the required bolttension.

Type (b) of the connections above, includes connection where bolts are subject to direct

tension or those with tension as a result of moment application such as the case in rigid

frames at the haunch and peak connections.

Snug tight tightening need also be applied to shear / bearing connections.

Snug tight condition is defined as the tightness that exists when all plies in a joint are in

firm contact. This may be attained by a few impacts of an Impact Wrench of the full

efforts of a man using an ordinary Spud Wrench. Shear/ bearing connection exists

usually in the following situation:

a- Mezzanine / Beams / Joists connections

b- Angle Bracing or any connection subject only to shear.

Most PEB Steel tightening practices are required to be Snug tight position. Where

specified bolts should be tensioned to the recommended tension values.

The drawings in next page are illustration for the right use of each case mentioned above.


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4.9 Are fully threaded high strength bolts subject to any strength reduction?

PEB Steel has switched to the use of fully threaded high strength bolts and has been

under use for years with a proven track record of quality. As PEB Steel is the designer of

the projects, all the connections of the job utilizing A-325 high strength bolts are

designed taking into account the fact that threads are included in the shear plane.

However, it must be noted that all the chemical and mechanical properties of the material

are same for both threaded or unthreaded fasteners.

PEB Steel ensures that fully threaded bolts are specified in our purchase orders to our

vendors as per our design requirements, and there is no reduction of strength as a resultof using such fully threaded fasteners.

4.10 Why are sizes of the rigid frame members, portal frame members and other

primary steel members, not shown on the erection drawings?

As per PEB Steel practice over the years, we do not provide such dimensions on the

erection drawings unless specified by the customer in the contract.

Dimensions and clearances on the drawings tend to confuse the erectors, in addition,


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such information are not required for the erection use, though reference can be made to

the design calculation package whenever needed for further clarification on suchdimensions.

The erection drawings intended to show how to assemble and erect the building. This set

of drawings is required for each building of the job. Therefore, the purpose of the

erection drawings is to provide the erector with the necessary information to safely erect

the building. Part numbers for the building elements are shown on the drawings and

physically marked on the steel members.

4.11 Why PEB Steel dont use washers for the purlins lap connections ?

In order to meet the dimensional tolerances, oversized and slotted holes are used inpurlins to provide the flexibility and functionality to the members to be joined during

erection time. The criteria for using washers at the purlins lap connection has been

subject to continuous evaluation to provide a clear understanding of such practice.

Practical experience over the last 22 years at PEB Steel, have indicated that theperformance of bolted connections (shear type) is not affected by the absence of washers

at lap locations. Specifications of AISC codes -manual of steel construction, 9th

edition

section 5-7(c) page 272- makes a clear reference to this subject, where machine boltsA307 are excluded from the use of washers. Those specification provisions apply only to

high strength A325 - A490 bolts.

In a complementary action by the AISI codes, washers are mentioned to be not required

for oversized and slotted holes, where suitable performance is demonstrated by tests.PEB Steels position on this issue does support such codes provisions, and our design

engineers do check the shear capacity of the bolts to determine any reduction in strengththat might be encountered.

As per tests concerned, PEB Steel practice for the last years is a major endorsement on

such issue, where no problems have been reported at all. This practice has proven to be

fully satisfactory to our customers and no measures are required to be taken.


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4.12 Why bracing is not allowed for Post and Beam Endwall?

The Post and Beam endwall system of framing consists of columns ( posts ), with pinnedends, supporting endwall rafters . Flush-framed girts between posts as well as cladding

provide lateral stability through the diaphragm action.

Lateral stability along the width of pre-engineered steel buildings is provided by

designing the frames to resist the imposed lateral loads.

Bracing systems are usually furnished along the length of the buildings to provide

longitudinal stability due to the weakness of the building structure in that direction.


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4.13 When do we require rotational bracing?

It is a bracing with only one side wall bracing. This type of bracing is not applicable for

building with width greater than 15m and eave heights greater than 6m and not

applicable for crane building.

The loads in the roof system are all transferred to one side wall containing thevertical bracing.

4.14 When do we require minor Axis Bending?

This system is recommended generally for open structures with narrow widths, low eave

heights and having a large number of bays. The lateral force along the eave of thebuilding is divided by the total number of main frame columns, resulting in a small force

per column that can be resisted by the section properties of the column about its weak

axis.

In this method, the rigid frame columns are analyzed as fixed at the base in the minoraxis direction so as to resist the lateral forces applied along the length of the building.

Minor axis bending becomes uneconomical and less suitable for enclosed buildings with

greater widths, high eave height and smaller number of bays. This bracing system is most

common in car canopies, which require walls to be fully open for access.


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4.15 When and why do we require an expansion joint?

Expansion joints are provided at certain intervals along a member to absorb accumulated

incremental movements resulting from temperature changes in the structure.

When a member is restrained from free movement during expansion or contraction ,stresses develop in the member. If these additional stresses are not considered in the

design of that member, failure may occur.

PEB Steels standard practice for the above matter, is to use only one rigid frame at the

location where an expansion joint is required and to provide slotted purlin holes at thelocation of the expansion joint that can absorb thermal movements at that points.

However, regardless the thermal expansion, an expansion joint is recommended

whenever the building length exceeds 120m.


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Fabrication5.1 Why Purlins and Girts have redundant holes?

PEB Steel uses standard various punching pattern at purlin and girt end locations for

connection purposes. Such standard punching patterns do include many connection

possibilities (short, continuous, long lap connection, location of flange bracing, sag rods,

end-wall connections, strut clip connection, framed opening clip, stitch bolt connectionwhere there is nested purlins, etc..), depending on various design requirements. As a

result, some holes may not be used at certain times. Their presence does not affect the

structural integrity or the durability of a members.

5.2 Do the surfaces of connection need to be in complete contact in order to achieve a

satisfactory connection?

As per the AISC, the faying surfaces of connection need not to be in complete contact if

all the bolts reach their snug tight condition.

As per the AISC, 9th

edition - Code of Standard Practice, Projecting elements of

connection attachments need not be straightened in the connection plane, if it can be

demonstrated that installation of the connections or fitting aids will provide reasonable

contact between faying surfaces.

Also as per the AISC, under Installation and Tightening even after being fully tightened,

some thick parts with uneven surfaces may not be in contact over the entire faying

surface. This is not detrimental to the performance of the joint. As long as the specifiedbolt tension is present in all bolts of the completed connection, the clamping force equal

to the total of the tension in all bolts will be transferred at the locations that are in contact

and be fully effective in resisting slip through friction.

It is important to note from the above that even with slip critical type joint, full contact

between faying surfaces is not vital for the connection to be satisfactory.

5.3 What causes the waviness of the welded built-up members (Web)?

In making a weld, the heating and cooling cycle always causes shrinkage in both base

metal and weld metal, and shrinkage stresses tend to induce a degree of distortion. The

enormous temperature differential in the arc welded area creates a non-uniform

distribution of heat in the welded members.

The heat of welding causes the metal adjacent to the weld deposit to expand. However,

this metal is restrained by the relatively cooler sections of the remainder of the plate.

Almost all the volume expansion must take place in thickness. On cooling, this heatedsection undergoes volume contraction, resulting in shrinkage stresses in the longitudinal


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and transverse direction, and this adjacent base metal tends to shrink along the weld

metal.

Heating on the side of the member initially causes expansion and bowing upward. This

problem is of no major importance.

Permissible AWS tolerances for most welded members are illustrated below as follows

(refer to the sketch in next page):

Deviation between centerline of web and centerline of flange.

Camber or sweep of columns.At left, tilt of flange; and at right, warpage of flange.

Deviation of camber of girders.Sweep of girders.Deviation from flatness of girder web.

5.4 What causes the abrasions of the shop coat primer applied by PEB Steel plant ?

All structural members of the pre-engineered building system not fabricated from

corrosion resistant material or protected by a corrosion resistant coating, are painted one

coat of shop primer (red oxide or gray oxide). All surfaces to receive shop primer arecleaned of loose rust, loose mill scale and other foreign matter prior to painting.

Sandblast is not necessary unless required by the customer. The shop primer is intended

to protect the steel framing during transport and erection. The shop primer cost does not

provide the uniformity of appearance, or the durability and corrosion resistance.

PEB Steel is not responsible for the deterioration of the shop coat primer, or corrosion

that may result from prolonged exposure to environmental conditions, nor the

compatibility of the primer to any field applied coating. Minor abrasions to the primercaused by handling, loading, shipping, unloading and erection after painting are

unavoidable.

Please, refer to the erection guide manual for proper storage of shop painted steel at site

before erection, to avoid water-holding pockets, dust, mud, and other contaminationelements of the paint film.

5.5 What is the reason behind flat fixing of the roof sheeting panels ?

There are several reasons why PEB Steel uses the practice of flat fixing of the roof

sheeting panels, those are:

Based on vast experience with our panel, we find that the end-laps are the first area to

corrode. This problem is due to ingress of dust, sand and water, which remain trapped.

We have found that at end-laps, the minor corrugation tends to be slightly raised afterscrewing the adjacent high ribs. By fixing in the flat we can eliminate the gap thereby

reducing the possibility of corrosion and leakage.


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Fixing in the flat gives a more positive connection to the purlins and the screw will not cause

any dimpling of the panel when properly tightened to compress the EPDM washer. Dimplingoften occurs at high rib fixing when tightening a screw to properly compress and expand theEPDM washer.

The screws we use for roofing are of the highest quality developed for the specificapplication. These screws are with EPDM washer called T19, it is 3mm Thick & 19mm Dia.

This makes T19 the best washer in the Industry to prevent water leak.


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Compatibility of Materials andPerformance

6.1 Is Zinc Aluminium Roof Sheeting compatible with Galvanized Purlins ?

With growing customer awareness of products and their potential performance, it isbecoming increasingly important that manufacturers adhere to the international standards

which relate to the products they use. PEB Steel fully complies with those standards and as

per Blue scope Steel confirmation on such issue, Zinc Aluminium steel is fully compatible togalvanized steel Z & C purlins. However, some metals (such as copper and lead) which

can cause an accelerated corrosion when used with Zinc Aluminium.

6.2 How compatible Zinc Aluminium is with other materials ?

The avoidance of direct contact between incompatible metals, although minimizing electro-chemical corrosion, will not necessarily increase the resistance of the metals to general

chemical attack in strong corrosive atmospheres. In such atmospheres, certain metals requirethe extra protection of a coating. Such extra protection should be applied to the sheet

fasteners as well as to the sheeting and specially to those parts of the sheeting and / or

fastenings in mutual contact. Lead must not be in contact with aluminum alloys oraluminum/zinc-coated steel.

Copper is incompatible with Zinc Aluminium, either in contact with or where water can flow

from it, such as is often experienced with hot water system overflows.

Lead is also incompatible with Zinc Aluminium, which in contact with orreceiving run-off water from lead is prone to the coating corrosion.Therefore, lead washers, lead-headed nails and lead flashing should not beused


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Rating:

*** = Acceptable, increase in the corrosion rate of the sheeting or contact

material

will be zero or slight.

**=

Acceptable, but increase in the corrosion rate of the sheeting or contact

material can occur.

X =Do not use. Accelerated corrosion will occur, or the reduction in the

lives of the two materials is too great or both.

6.3 What is the reason of Black Stain on Sheeting Panels?

Storage stain is a dark gray to black stain, that can occur on coils and tightly packed stacks of

sheets or panels of Zinc Aluminium sheet. In its very early stages, it can appear as a whitestain similar to the storage stain that can form on galvanized steel. Although storage stain is


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usually superficial, it is unattractive and can progress quickly to a more severe state if the

cause of the stain is not eliminated. When it is severe, there can be a substantial loss ofcoating material and subsequent reduction of service life. The storage stain itself will notworsen once a panel is in place

The cause is water or moisture. Water can get into an unwrapped steel coil or lift of cut-

length sheets by exposure to rain or high humidity. Even though the coil laps, cut sheets or

roll formed panels are tightly packed, moisture can enter the closed surfaces by capillaryaction. Water often gets on the sheet by condensation. When cold steel is brought in from

outside to a warmer building, the moisture in the warm air condenses on the colder steel.

Zinc Aluminium has excellent durability in the atmosphere because of the protective, air-

formed oxide that forms on the surface. However, the situation is different inside coils or inbundles of closely formed panels, because there is no free access to air. If water or moisture

is present, a faster type of corrosion occurs due to the lack of an inhibiting oxide film. Under

these conditions, storage stain on Zinc Aluminium sheet can occur in as little as 24-48 hours.

Even pre-painted Zinc Aluminium sheet is not immune to storage stain. Roll forming pre-

painted sheets into profile panels can results in micro-fracturing of the paint. These very fine

micro-cracks are of no consequence and in no way interfere with durability, but they can

permit access of moisture to the metal surface. Inside a bundle of painted panels, the sameaccelerated corrosion can occur as with bare Zinc Aluminium sheets.

6.4 What is White Corrosion and its effect on Panels life expectancy?

White corrosion is the formation of a basic zinc carbonate complex on zinc surfaces in moist

atmospheres where unprotected by surface passivation this is an in-line process on thecooled strip after hot-dip metallic coating and prior to coiling. The purpose of this

passivation is to afford a measure of protection to sheets bundles or coils if they get wet, and

to assist exposed exterior metallic finishes to weather evenly in use. While this protection iseffective, it can provide only a limited period of resistance to wet storage damage.

White corrosion is a discoloration of the surface of the sheet panels usually found on nested,

unwrapped corrugated sheets which have been exposed to moist air or dampness, that

permeates into the capillary or open spaces between the nested sheets. It can be any shade ofdiscoloration from white, through light gray, blue gray, to black; which is usually caused by

exposure to polluted air high in sulfur content. The white corrosion can be localized in spots

on one side of the sheets, or may be massive and cover the whole sheet on both sides.

Formation of the white corrosion consumes zinc and the degree of damage is indicated by the

depth of corrosion product. Generally speaking, very light superficial powdery corrosionproduct, would have minimal effect on the panels life, while thick crusty white deposits are


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evidence of potential reduced life.

White corrosion, will not materially affect corrosion resistance, and no rusting of the

corrosion resistant base steel will occur under normal use and circumstances. Thus, white

corrosion on galvanized sheets surface is not a cause for rejection.

6.5 What are the most common causes of early failure of the Gutter and Downspouts ?

Based on years of experience regarding the relative performance of gutters and down-spouts,

important findings of causes of early failure include:

Leaves accumulated in the gutter.

Ponding of water.Acid in gutter resulting from the cleaning down of brick work above the gutter.

Water dripping into guttering from INERT catchments.

The solution to the problem of early gutter failure lies simply in the knowledge of the

mechanism of corrosion. Research carried out by Blue Scope Steel has proved that Zinc

Aluminium used as a gutter and down spout product in combination with any traditional

roofing material will perform the desired non-corrosive functions of a gutter and down spoutsystem far better than zinc-coated material. (The following pictures illustrate the tests carried

out).

6.6 Why must Steel be Coated?

The durability of a well designed and maintained steel structure is practically indefinite.

When exposed to the atmosphere, all construction materials deteriorate and steel is no

exception. The protection of steel is not the problem but the degree of protection required forfull assessment.

A building represents a major investment for its owner. Whether a building is constructed out

of concrete or out of steel, it is being continuously exposed to heat, dust, salt, sand, moistureand other environmental and/or climatic conditions. Even indoors, corrosion can have ground

to initialize.

It is therefore important to protect structures against corrosive exposures with reliable

protective coating systems. A properly applied protective coating system will not onlypostpone maintenance for years, but it will at the same time minimize the recurring costs of

maintenance. Maintenance will still be necessary because of mechanical damages, abrasion

blistering, flaking or corrosion.


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6.7 What are the factors that affect the service life of the steel members ?

The service life up to the first maintenance is dependent on the following factors:

Exposure conditions: the more severe the exposure condition, the higher the demands for the

coating system.

Surface preparation: a high standard of surface preparation such as ISO-Sa 2 (ABRASIVE

BLASTING) will substantially extend the service life of the steel.

Type of coating: epoxy/polyurethane coatings will have a service life almost twice as long as

alkyd coatings.

Dry film thickness (DFT): the higher the film thickness, the better the protection; as long asthe thickness does not exceed the manufacturers recommendations.

6.8 Why is the cost-durability balance and the factors that affect the degree of protection of

the steel ?

The choice for a protective system need not be the most expensive. It needs to be capable of

providing adequate protection throughout the planned usage period. There is no logic to

protect a steel structure with a coating system that will last for 20 years, when the structureitself will become redundant in 10 years.

Architects, engineers and end-users have in the past overemphasized the protective systems,

only to turn them down later when they realized their cost implications.

6.9 What are the effects of Corrosion on unprotected steel members ?

Corrosion is a hydrated form of iron oxide (iron oxide combined with water), very similar tomany iron ores in composition. Unlike some metal oxides as described above, however, it is

very porous and does not protect iron or steel surfaces from further reaction with the

atmosphere. It is not very tough and, as corrosion proceeds, will flake away from a steelsurface allowing more corrosion to form, a very similar pattern. This is the very reason why

steel is coated.


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6.10 How can Steel be protected to avoid material deterioration ?

Elimination or reduction of any of the three essential parameters, water, oxygen, or the

electric current is sufficient to stop the rate of corrosion. Pollutants in air act as corrosion

accelerators, because sulfur dioxide from industrial atmospheres and salt from marineenvironment increase the electrical conductivity of water.

Usually local rust spots are acceptable from a structural standpoint but flakes of trust are not.

The best way to keep water away from steel structures is by storing it inside a dry area of thebuilding.

Steel can be protected from corrosion by the atmosphere in many ways. For sheet and strips

materials, the most economic has been to coat it with any one of a number of materials, frompaint to metals of various types.

6.11 What is the most economical way to prevent steel structures from corrosion ?

A good design that takes into account all possible ways of preventing corrosion is much

better and economical than one where protection only depends on the coating system

applied.

Experienced design engineers at PEB Steel acquire a corrosion awareness that enables themto eliminate potential corrosion hazards. PEB Steels good design practice include:

Proper design by the careful choice of suitable shapes to avoid corrosion.

Avoiding entrapment of moisture and dirt.

Avoiding small gaps, slits and lap joints.Avoiding sharp edges and corners.

Avoiding contact with different materials (contact causes Galvanic action).

Avoiding places that can not be reached either for painting or for cleaning.

6.12 What is the criteria to decide on the most adequate protection system for steel

structures?

The materials and methods used to protect the structural members of the building from

factors that affect the building safety and durability. These factors are fires, weather,corrosion and chemical attacks.

Failure to provide adequate protection may shorten the life of the building and affect its

functionality and safety.


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The type and cost of protection systems vary substantially. The factors to decide on the most

adequate systems are as follows:

The required functional life of the building.

The cost and quality of maintenance, cleaning and repair.The intensity of the affecting factor and the probability of occurrence;buildings located

Near the sea need more paint protection than buildings located in a friendly environment.

Building contains flammable objects need special care for fire protection.

The decision on the most suitable protection system is a decision of economy and safety.

6.13 What are the Barrier coating types for the steel structures?

The simplest coating type for steel sheet is one which provides a purely Mechanical barrier

between it and the atmosphere, i.e., air and moisture. This works extremely well PROVIDED

there are no breaks in this barrier coating, caused either by shearing to adjust the size of thesheet, by punching holes for fastening, by scratching or damage to the coating or by the

gradual deterioration of the coating by natural weathering processes.

Protective coatings are achieved by metal coating, paint coating or combination of both.

Common types of simple barrier coatings used for steel sheet are:

- Metal Coating

Hot-Dip Galvanizing: zinc is higher thaniron in the

galvanic series, so it is more active.

The period during which a zinc coating protects the steel is directly

related to the coating thickness.

70 - 100 u of zinc coating can provide up to 20 years of protection

in a coastal climate.

Distortion is a problem during the hot-dip process, mainly in lightsections.

- Zinc Spraying

Using zinc wire melted on a flame in a spraying gun (surfaces inSa2 or Sa3). No distortion, but porous which usually require

over-coating.


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6.14 What is the purpose of PEB Steels Primer Coating?

The main purpose of PEB Steels standard 40 microns Red or Gray Oxide Primer (applied

over solvent cleaned steel), is to protect the steel structure against excessive rust during the

transport and the relatively short period of time of steel erection. The performance of this redor gray oxide primer on its own and without the application of any further coatings has

proven to be adequate in the majority of applications, particularly when the location of the

erected building is far away from the coast, and the building is enclosed and well ventilated.

6.15 What are the procedures for surface protection of steel members ?

Some cases where a red oxide primer applied to the steels surface is not deemed sufficient, a more

elaborated surface preparation method and more sophisticated paint system is required.

6.15.1 Preparation of a steel surface for protection:

-When the steel comes out of the mill, due to the hot surface, it reacts

with the air to form an oxide scale (called usually mill scale). If paint is applied on top ofthis mill scale in a very corrosive environment, paint may fail early due to flaking. If paint

is applied on top of rust, the performance of the paint usually is not satisfactory.

-

Cleanliness The Swedish pictorial surface preparation standard is the most wide

spread standard for surface cleanliness indication. The Swedish classificationstandard specifies two processes for cleaning:

Hand Cleaning (St). Blast Cleaning (Sa).

St2 : Thorough scrapping and wire brushing, machine brushing, grinding, etc..

The treatment shall remove loose mill scale, rust, and foreign matter.The surface ends with a faint metallic sheen.

S3: Very thorough scrapping and wire brushing. More thorough cleaning than

the St2. Results is clear metallic shine.

Sa1 : Light blast cleaning, loose mill scale, rust and foreign matter shall beremoved.

Sa2-1/2 : Very thorough blast cleaning. Mill scale and rust were removed to the extendthat only traces are remaining. (In the form of spots or stripes).


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Finished Building Care&

Maintenance7.2 What are the factors which cause damage to the sheeting panels ?

Rain, condensed moisture, dust and airborne contaminants from other localpollution, and plant conditions, combine to provide an electrolyte which enables

corrosion of iron and steel to proceed. Under these conditions, every attempt shouldbe made to avoid the entrapment of such contaminants. The contours of exposedsurfaces should be as smooth as possible and be free of unnecessary cavities,

recesses and protuberances.

7.1.1 Water Stain (or White Oxide)

When a galvanized product is exposed to the air, the surface gradually loses itsgloss and becomes dull gray darkening as it ages. This is due to the surface zinc

being transformed into a compound of zinc carbonate, zinc hydroxide and zinc

oxide which acts as a protective film on the surface.

In the majority of cases, the compound is primarily composed of zinc carbonatewith relatively small amounts of zinc oxide and zinc hydroxide. However, if

improperly stored, white oxide may be formed. This compound contains high

amounts of zinc hydroxide, the percentage being dependent on storage andatmospheric conditions.

If the protective oxidized film of completely gray zinc carbonate compounds has

been formed, then white oxide is rarely a problem. If, however, the galvanized coat

is exposed to moisture before or during the chemical transformation of the outerzinc layer, then white oxide, high zinc hydroxide content emerges on the surface.

The white oxide appears in a powder form on the surface of the zinc. At a glance,

the zinc will appear to be heavily corroded. In practice, the loss of zinc will be in

the range of 0 - 4.0 g/m2

which is very small compared to a coating classificationsuch as G90, which is 275 g/m

2(total coating weight on both sides).

In some instances, the formation of black spots or patches may occur along with

the white oxide, although it is of poor appearance. There is no reason for rejection


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as there is no significant reduction in the relative corrosion resistance.

7.1.2 Contact with Iron

Corrosion and possible failure of the zinc coating may take place when ferrous

based materials are in contact with the zinc coated surface. Examples of this arenails, screws, metal filings, swarf, etc. Which can penetrate the outer paint layer, if

any, and then form a chemical reaction with the zinc layer eventually breaking it

down, and the corrosion reaching the base metal.

7.1.3 Continuous contact with Moisture

Continuous contact between galvanized or pre-painted material and moisture willlead to a rapid breakdown of the zinc layer, and eventual corrosion of the base

metal. This fact is often overlooked, particularly after building has been completed.

Common sources of this problem are as follows:

Damp wind-blown sand stuck to the exterior cladding for a long period of time.

Ground soil or sand heaped against wall cladding for any length of time.

Condensation from air conditionings units dripping onto the panel.Water storage tanks being located adjacent to the panel. Evaporated water

condenses on the panel.

Inlet or outlet air grills, located in the wall cladding eventually clog with dampdust particles which should be periodically cleaned

Metal filings stuck to the surface of the panel.Uncoated ferrous items connected to the galvanized section.

7.2 How can we prevent panels from Storage Stain ?

Prevention of wet storage stain is the responsibility of the mills, shippers,

fabricators and erectors. Any letdown in the chain from mill to final erection cancause rapid corrosion if moisture is present.

As for the erection, refer to the PEB Steel erection guide manual for properprevention of such problem. Erectors, as the final links in the chain to prevent

storage of Galvalume sheet, should do the following:

Inspect the bundles on arrival at the building site and note on the delivery receipt

any exceptions such as damage, corrosion or wet material.

Store the bundles on racks at least one foot above ground level. Do not use uncured

lumber.


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Under roof storage is recommended when possible. If the bundles must be stored in

the open on bare ground, then a plastic ground cover should be used under thebundles to minimize condensation on the sheets from moisture in the soil.

Elevate one end of the b

Documents

2. Pebs Manual