Pebs Manual

 

PEBS MANUAL

 Building for Life

PEB STEEL GROUP Pre-Engineered Buildings

 Jan, 2007

 

 

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.

 

 

PEBS Manual Contents 1.  APPLICATIO APPLICATIONS NS OF PRE-ENGINEER PRE-ENGINEERED ED BUILDINGS ....................................................1

2. PLANNING AND OPTIMIZING THE PRE-ENGINEER PRE-ENGINEERED ED BUILDINGS. .................12 3. DESIGN CODES............................................... CODES............................................................................................................... ................................................................ ......25 4. DESIGN ENGINEERING PRACTICES.... PRACTICES...............................................................................27 ...........................................................................27

5. FABRICATIO FABRICATION N .......................................................................................................... .......................................................................................................................38 .............38 6. COMPATIBILITY OF MATERIALS AND PERFORMANC PERFORMANCE.... E.... ....................................41 7. FINISHED BUILDING CARE ............................................................................................ .............................................................................................49 .49 8. ERECTION...............................................................................................................................52

 

 

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Application of Pre-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 to other industrialized countries. It consists of a complete steel framed building system, with  pre-designed components to best suit the unique customer requirements. The final product is a complete building shell with sub structural systems including mezzanine floors, crane systems, canopies, fascias and interior partitions. The end product is an attractive building that can be finished finished internally to serve the required function and accessorize externally to achieve 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. PEB system an active role in converting complex and expensive structural the steel building designs plays into simpler and more economically designed, without sacrificing utility and  basic function of these buildings. The PEB system offers multiple advantages to the end-user, e nd-user, the most notable are low initial investment, fast construction time, low maintenance cost, large clear spans, infinite choice of 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 with alternate 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 maximum efficiency, 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, and  presenting a clear vision of the economy, diversity, versatility and esthetics feature of PEB as an enormous advantage for this industry’s growth. 1.2 What is the meaning of Pre-Engineering Building? Building?

Pre-engineered should not be confused with pre-fabricated. The name Pre-engineered  buildings 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 supported  by 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 are a re PEB. 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 no t limited to- the following: Industrial Buildings -Factories Warehouses Distribution Centers Commercial Showrooms Sports Halls Recreational Buildings Shade Structures -Gas Stations Agricultural Buildings -Grain Storage Institutional Buildings Aircraft Hangars Supermarkets Workshops Restaurants Office 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, PEB’s 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 building requirements. 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: 2

Design load is indicated to be : Live Load = 0.57 KN./m  Wind Load = 130 Km/Hr, these loads 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 30 m can be accommodated. Eave heights as high as 30 m can be accommodated in special buildings. The eave height is a critical issue when selecting the type of building for the appropriate application. The PEB system offers multiple advantages to the end-user, e nd-user, the most notable are low initial investment, 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 manufacturer’s 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 commercial  buildings such as: Large Manufacturing Plants Mill Buildings Buildings less than 5 stories Warehouses Office Buildings The engineering work of Structural Steel fabrication, is limited to the estimation and  preparation of erection and shop drawings for fabrication of assigned projects, design is rarely done by the manufacturer. The following shows a comparison between PEB P EB and Structural Steel, intending to familiarize design groups with the basis of the PEB concept, co ncept, its high versatility and  practicality, and the advantages to designers and consultants.

 

 

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Feature  Design Pre-Engineered Steel Buildings

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Conventional

Steel

Buildings

Criteria

A.I.S.C., M.B.M.A., A.W.S, AISI

A.I.S.C., A.W.S., J.I.S., D.I.N.B.S.

Foundation

Simple design, easy to construct and lightweight.

Extensive, heavy foundations required.

Average 6 to 8 weeks.

Average 5 to 6 months.

Building is supplied complete with cladding and all accessories, including erection if desired, all from one source source of supply. About 30% lighter through the efficient

Many sources of supply. Project Management time required to coordinate suppliers and sub-contractors.

 Delivery

use of steel. Primary framing members Sourcing &  Coordination 

are (varying depth) tapered built-up plate sections with large depths in the areas of highest stress. Secondary members are light gage (light weight) cold formed (low labor cost) “Z” or “C” shaped members. Z purlins/girts can be lapped. Lapping reduces the deflection, and allows allows double thickness at the points of higher stresses (support points).

Primary steel members are selected from standard hot rolled “I” sections, which in Many ca cases ses are are heavier heavier than than wha whatt is actually required by design. design. Members have constant cross-sections along the Entire span, regardless of local stress magnitude. Secondary members are selected from standard hot rolled “I” and “C” sections, which again are heavier than required.

 

 

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Feature

Pre-Engineered Steel Buildings

Conventional Steel Buildings

 Design

Quick and efficient since standardization Each conventional steel structure is of P.E.B. has significantly reduced designed from scratch by the Consultant, design time. Basic designs are used over with fewer design aids available to the and over. Specialized computer analysis Engineer. Maximum engineering and design programs reduce design time required on every project. Generalized and optimize material required. Drafting computer analysis programs require is also computerized with minimal extensive input / output and design manual drawings. Design, detail alterations. Drafting is manual or only drawings and erection drawings are  partially automated. automated. Much Consult Consultant ant supplied free of charge by the time and expense is devoted to design manufacturer. Approval drawings may and drafting, as well as coordination and  be prepared within 10 days to 3 weeks. review. 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, the cost is reduced due to smaller sections at the base with smaller base plates and foundations (in absence of moments).

 Accessories Windows, Doors, Ventilation

Designed to fit the system, with standardized, interchangeable parts, including pre-designed flashing and trims. Mass produced for economy. All available with the building.

Every project requires special design for accessories and special sourcing for each. Flashing and trims must be uniquely designed and fabricated.

 Erection

Easy, fast, step 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, tthe he erection costs and time are not estimated accurately.

 Architecture

Outstanding architectural design can be achieved at low cost. Conventional wall

Special architectural design requires research and high cost.

and fascia materials, such as concrete, masonry and wood, can be utilized.

Overall Price

Price per square meter may be as much as 40% lower than conventional steel.

High price per square meter.

 

 

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Feature

Pre-Engineered Steel Buildings

Conventional

Changes

Very flexible, tailor made, accepts changes and revisions easily. Future expansion simple, easy and cost effective. One supplier to coordinate changes.

Changes, revisions & additions can be difficult due to extensive redesign and coordination among suppliers and subcontractors.

Performance

All components have been specified and designed specifically to act together as a system, for maximum efficiency, precise fit-up, and performance in the field. The experience with similar buildings, in

Components are designed in general for possible use in many alternative configurations. Design and detailing errors are possible in assembling diverse components into unique buildings. Each  building design is unique, so prediction of how components will perform together is uncertain. Materials which have

actual field conditions world-wide has resulted in design improvements over time which allow dependable prediction

 Responsibility

Steel

Buildings

of performance.

performed well in some climates may not in other environments.

Single source of supply results in total responsibility for one supplier, including design liability.

Multiple responsibilitie responsibilitiess can result in questions of who is responsible when 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 quality  possible. 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-work or 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. Formwork 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 concrete’s large dead load has a great effect on bending moments. Similarly, the low strength per unit of volume of concrete 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 concrete’s 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 of Pre-Engineered Steel Buildings instead of Reinforced Concrete Buildings. Feature

Steel

Concrete

Fabrication

Done in shop-controlled conditions Precise and Fixed Precise and accurate measurements May carry up to 6 times its weight Lighter Faster Larger Higher Movable, Expandable Needs more protection Industrial, Commercial

Mostly done at site in variable conditions Variable, Non-homogeneous Potential for significant errors.

Material Specifications Dimensions Capacity Material Foundations Erection Clear Spans Buildings Height Changes Fire Resistance Applications

Carried load almost equal to its weight Variable Slower Smaller Shorter Difficult to modify Good Resistance 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 recognized codes 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 fabrication of Pre-Engineered Building systems, are new, unused and meet or exceed the physical requirements of the PEB system design and fabrication  processes, as well in accordance with the materials manufacturer’s standards and  procedures. Our quality control department tests the material ordered for inventory to meet the design criteria for strength and to ensure that these these materials possess possess the qualities 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 for the 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 the American 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 the steel members. Manufacturing dimensional tolerances shall be in accordance with MBMA 2002. The materials of the steel members used in the PEB manufacturing are conforming to American 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:

2006 edition of the International Building Code  International code council, Inc (IBC) 4051 West Flossmoor Road, Club Hill, IL 60478-5795, USA Manufacturing and Erection tolerances are applied as per:

2002 edition of the Low Rise Building Systems Manual   Metal BuildingAve., Manufacturers (MBMA) 1300 Summer Cleveland,Association, Ohio 44115,Inc 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:

2003 Edition of AISI (North American Specification for the Design of Cold Formed Steel Structural Member ) American Iron and Steel Institute (AISI)  1000 16th Street, NW, Washington, DC 20036, USA Welding is applied in accordance with:

2004 American Welding Society (AWS D.1.1.04) Structural Welding Code – Steel Manual 550 NW LeJeune Road, Miami, FL 33126, USA

 

 

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PEB STEEL STRICT DEFLECTION CRITERIA

Structural Member

Deflection

Vertical Deflection   Deflection

Lateral Deflection   Deflection

Deflection Limitation

Load Combination

1

Main frame rafters

Span/ 180 

Dead + Live

2

Roof purlins

Span/ 180 

Dead + Live

3

Mezzanine beams and joists

Span/ 180 

Dead + Live

4

Top running crane (TRC) beams

Span/ 600

Dead + Crane

5 6

Underhung crane (UHC) beams Monorail crane (MR) beams

Span/ 500 Span/ 500

Dead + Crane Dead + Crane

7

Relative deflection of adjacent frames Bay/ 225 at point of support of UHC or MR  beam.

Crane only

8

Relative deflection of UHC beams supported by the same frame

Crane span/ 225

Crane only

9

Rigid frame rafters supporting UHC or MR beams running laterally in the Bldg. Span/ 500  building.

Crane only

1

Main frame columns with eave height Eave height/ 9 90 0 (EH) up to 9.0 m

Dead + Wind

2

Main frames supporting top running cranes (TRC) or underhung cranes (UHC)

Eave height/ 100 100

All

3

Wall Girts

Span/ 90 

Wind only

4

Endwall wind columns

Span/ 90

Wind only

5

Portal frames

Eave height/ 90 

Wind only

 

 

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Planning and Optimizing the Pre-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 of single gable interior rigid frames with either rigid or “post and beam” frames at endwalls.

 

 

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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 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 the  plane of the outside vertical surface of the eave strut. End-wall En d-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 the exterior side-wall of the lean-to building to the (side-wall or end-wall) steel line of the main 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 of the first interior frame. Interior bay length is the distance between the center lines of two adjacent interior rigid 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 the underside of the side-wall column base plate) to the top of the eave strut at the sidewall 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 the side-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 “SS” Multi-Gable “MG” Clear Span “CS” Multi-Span “MS” Space 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, column reactions, 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/M², 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 PEB Steel 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 pre-eng ineered 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 project cost 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 building configuration is possible but may require more engineering time and possibly longer deliveries. Practically, any geometrical shape can be done. Those shapes vary as follows: 2.3.1

Single Slope “SS” (Mono-slope (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 b e 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 to specify 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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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 in many regions of the world, PEB Steel recommends the use of Multi-Span buildings in lieu of Multi-Gable buildings. We discourage Multi-Gable 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

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

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Multi-Span "MS" buildings shall have a gable roof with vertical side-walls and endwalls. Interior bay frames shall be rigid frames typically having tapered exterior

columns, 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 24 m . 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." "S.S."   (also known as main-streeter ) buildings shall have a gable roof

with vertical side-wall Interior bay rafters, frames frames typically shall be clear rigid frames havingside-walls constants and depthend-walls. columns and tapered with span 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

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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 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 with moment 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

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What is the Maximum Possible Span & Loading Capacity?

Spanning is a key issue when selecting the appropriate type of building for the customer application, 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 bu built-up ilt-up sections designed to support vertical and horizontal ho rizontal 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. columns. Jack beam is also required when a bay longer than 11m is desired along the length of a  building. 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 and above 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 Codes 3.1 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 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 ordinary construction 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 results, for their specific experience in using codeswhich revealed full satisfactory this is due projects, to the flexibility of PEB Steelsuch standards 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 co ntract 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 the  building.

 

 

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Design / Engineering Practices 4.1

What is PEB Steel’s 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 of Standard 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 capacities exceeding 15MT (Angles Only). Specialwith 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 the stiffness (I) ofincrease the member section. of the whole plate section, by increasing the moment of inertia 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) to withstand 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 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. That’s why PEB’s roof is stronger than others.

 

 

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4.5

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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 the codes 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 q uality 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 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 base metal (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 adopted measures 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 sales engineers should be aware when and to whom are releasing this kind of information, only unavoidable in cases where the customer insistence is affecting the company’s benefits, and even though prior consultation and approval from engineering is required for this issue. PEB Steel’s engineers do check and design the welds for the stresses occurring due to 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 need not 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

Thickness of Thicker Plate UP TO 6.4 mm 6.4 TO 12.7 mm 12.7 TO 19.0 mm ABOVE 19.0 mm

FLANGE

Minimum Size of Fillet Weld (Single Pass) 3 mm 5 mm 6 mm 8 mm

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

4.8 Is Bolt Tensioning required for primary connections?

Bolt tensioning must be employed in connections co nnections of any of the two following cases: a - Slip critical joints, where 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 bolt tension. 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, allinto theaccount connections thethreads job utilizing A-325 highshear strength designed taking the factofthat are included in the plane.bolts are 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 result of 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 such dimensions. 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 don’t use washers washers for the purlins lap connections ?

In order to meet the dimensional tolerances, oversized and slotted holes are used in  purlins to provide the flexibility and functionality to the members to be joined during erection The criteria for using washers at understanding the purlins lap has been subject totime. continuous evaluation to provide a clear of connection such practice. Practical experience over the last 22 years at PEB Steel, have indicated that the  performance of bolted connections (shear typ type) e) is not affected by the absence of washers th at lap locations. Specifications of AISC codes -manual of steel construction, 9 edition section 5-7(c) page 272- makes a clear reference to this subject, where machine bolts A307 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 Steel’s 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 strength that 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 pinned ends, supporting endwall rafters . Flush-framed girts between posts as well as cladding  provide lateral stability 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 the vertical bracing. minor Axis Bending? 4.14 When do we require minor

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 the  building is divided by b y 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 minor axis 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? 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. occu r. PEB Steel’s 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 the location 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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Fabrication 5.1 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 connection where 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. th

As per the AISC, 9  edition - Code of Standard Stand ard 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 specified  bolt 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 heated section 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):

5.4

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. 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 are cleaned 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. abrasions the primer caused by handling, loading, shipping, unloading andMinor erection after to 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 contamination elements 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 after screwing 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. Dimpling often occurs at high rib fixing when tightening a screw to properly compress and expand the EPDM washer. The screws we use for roofing are of the highest quality developed for the specific application. 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 and Performance 6.1 Is Zinc Aluminium Roof Sheeting compatible c ompatible with Galvanized Purlins ?

With growing customer awareness of products and their the ir potential performance, it is  becoming increasingly important that manufacturers adhere to the international standards which relate to the products they use. u se. PEB Steel fully complies with those standards and as  per Blue scope Steel confirmation on such issue, Zinc Aluminium steel is fully compatible to galvanized 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 electrochemical corrosion, will not necessarily increase the resistance of the metals to general chemical attack in strong corrosive atmospheres. In such atmospheres, certain metals require the 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 aand nd / or fastenings in mutual contact. Lead must not be in contact with aluminum alloys o orr aluminum/zinc-coated steel. Copper is incompatible with Zinc Aluminium, either in contact co ntact 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 or receiving run-off water from lead is prone to the coating corrosion.  Therefore, lead washers, lead-headed lead-headed nails and lead fla flashing shing should not be used

 

 

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Rating: ***

= Acceptable, increase in the corrosion rate of the sheeting or contact will be zero or slight. material

**

X

=

Acceptable, but increase in the corrosion rate of the sheeting or contact material can occur.

=

Do not use. Accelerated corrosion will occur, or the reduction in the lives of the two materials is too great or both. bo th.

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 white stain 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 of coating material and subsequent reduction of service life. The storage stain itself will not worsen once a panel is in place The cause is water or moisture. Water can get into an unwrapped steel coil or lift of cutlength 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 capillary action. 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, airformed oxide that forms on the surface. However, the situation is different inside coils or in  bundles 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 same accelerated corrosion can occur occu r as with bare Zinc Aluminium sheets. 6.4 What is White Corrosion and its effect on Panel’s 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 the cooled 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 co ils if they get wet, and to assist exposed exterior metallic finishes to weather evenly in use. While this protection is effective, 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 of discoloration 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 corrosion  product, would have minimal effect on the panel’s 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 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 spout system 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 for full 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, moisture and 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 only  postpone 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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What are the factors that affect 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 ½ (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 as the thickness does not exceed the manufacturer’s recommendations.

6.8

Why is the cost-durability cost-durability balance and the factors that affect the 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 last for 20 years, when the structure itself 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 the effects effects of Corrosion on unprotected steel members ?

Corrosion is a hydrated form of iron oxide (iron oxide combined with water), very similar to many iron ores in composition. Unlike some metal oxides as described above, however, it is very porous and does not n ot 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 steel surface allowing more corrosion to form, a very similar pattern. This is the very reason why steel is coated.

 

 

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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 marine environment 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 the  building. 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, from  paint to metals of various types. 6.11 What is the most economical way to prevent steel structures 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 them to eliminate potential corrosion hazards. PEB Steel’s 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 protection systems vary substantially. 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 an d safety. 6.13 What are the Barrier coating types for the steel structures? 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 the sheet, 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 light sections. Zinc Spraying  Using zinc wire melted on a flame in a spraying gun (surfaces in Sa2 ½ or Sa3). No distortion, but porous which usually require over-coating.

 

 

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What is the purpose of PEB Steel’s Primer Coating?

The main purpose of PEB Steel’s 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 red or 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 steel’s 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 of this 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 classification standard specifies two processes for cleaning:

-

Hand Cleaning (St). Blast Cleaning (Sa). St2 : Thorough scrapping and wire brushing, machine brushing, The treatment shall remove loose mill scale, rust, and The surface ends with a faint metallic sheen. S3

grinding, etc.. foreign matter.

: 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 removed.

matter shall be

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

 

 

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&  Finished Building Care Maintenance 7.2

What are the factors which cause damage to the sheeting panels ?

Rain, condensed moisture, dust and airborne contaminants from other local  pollution, and plant conditions, combine to provide an electrolyte which enables corrosion of iron and steel to proceed. proce ed. Under these conditions, every aattempt ttempt should  be made to avoid the entrapment of such contaminants. The contours of exposed surfaces 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 its gloss 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 carbonate with relatively small amounts of zinc oxide and zinc hydroxide. However, if improperly stored, white oxide may be formed. This compound contains high amounts of conditions. zinc hydroxide, the percentage being dependent on storage and atmospheric If the protective oxidized film of completely gray zinc carbonate compounds has  been formed, then white oxide is rarely a problem. If, however, howev er, the galvanized coat is exposed to moisture before or during the chemical transformation of the outer zinc 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 2 the range of 0 - 4.0 g/m  which is very small compared to a coating classification 2 such as G90, which is 275 g/m  (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 co ating may take place when ferrous  based materials are in contact with the zinc coated surface. Examples of this are nails, 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 will lead 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 damp dust 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 can cause rapid corrosion if moisture is present. As for the erection, refer to the PEB Steel erection guide manual for proper  prevention 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 the  bundles to minimize condensation on the sheets from moisture in the soil. Elevate one end of the bundle to allow any moisture to run off rather than puddle on the top of the bundle or between nested panels. Water resistant paper will not keep out puddle moisture beyond beyo nd its rated moisture vapor transmission time. 7.3

How can we remove Storage Stain from panels ?

Storage stain on Galvalume sheet is mostly hydrated aluminum oxide which can be very difficult to remove. In mild cases, a solvent such as mineral spirits applied with a soft rag has been known to effectively remove the stain. This method is also used to remove stain from pre-painted Galvalume sheet without damaging the  paint. For more advanced cases on unpainted Galvalume sheet, it is impossible to remove the stain without also affecting the good coating under and around the stained area. The amount of damage to the coating during removal will depend on the method used. In more severe stages, storage stain can be removed from bare Galvalume sheet with a mild household cleanser such as Clorox Soft Scrub and a wet sponge or rag. Industrial products such as Oakite 84M may also be used, but are more aggressive to the coating. In any case, the Galvalume panel should be thoroughly rinsed with water after the stains have been removed. Harsh alkaline cleaning solutions and high pressure sprays should be avoided, as these have been known to dramatically alter the corrosion resistance and appearance theabrasive Galvalume Steel wooliron should be used for two reasons, it isoftoo and itcoating. can leave behind finesnot which will rust and cause a cosmetic staining problem. Regardless of what method is used to remove the storage stain, remember that the coating has been affected by the stain cleaning. These areas will have a different appearance than the surrounding coating. And, depending on the severity of the stain, may have a shorter lifetime. Our initial consultations with steel mill metallurgists and our experience over the years has verified that the sheets PEB Steel use, storage stain (even after many years of nested exposure) will not materially influence the original corrosion resistance of the sheets after they are installed. Thus, we guarantee that all corrugated steel sheets furnished by PEB Steel meet the specifications, and white   rust or storage stain on galvanized surfaces shall not be cause for rejection.

 

 

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Erection

Why Girts sag during Erection ?

Girts are secondary simply supported members attached to the end-wall post web to support the wall panel sheeting (usually cold formed “Z”). Girts outside flanges are assumed to be restrained against lateral buckling by the wall panels. When the outside flange is compressed in flexure, the allowable bending stress is 0.6 Fy. When the inside flange is in compression and is unbraced, and the allowable stress is less than the actual stress, it is recommended the use of sag rods to brace the inside flange in order to increase the allowable bending stress. Usually the girts at the time of erection are aligned by means of wood blocking, one above the other between the girts, at mid bay, this makes a more accurate leveling of the girts for further connection to the sheeting panels. Girts are not designed to take any load, however, bay spacing of 8.5 m and more do require the use of sag rods for leveling and avoiding the deflections. Sheeting panels offer diaphragm action as a resistance to racking. Thus, only the sag is taken out by the wood blocking and the wall panels are attached, the girts will remain level and the wood blocking can be removed. Deflection of girts is not a major problem to worry about, since the integrity and building stability is not affected by any mean by the girt sagging. 8.2

What are the Procedures of storage storage of panels on site, prior to Erection ?

There are certain precautions which should be considered during handling and storage at site of panels bundles. These are: Panels are normally delivered in bundles which should be checked for moisture. This involves removing protective wrapping and binders and making random checks  between the panels. If moisture is present, the panels should be separated and inclined to drain moisture. If any salt compounds have formed on the surface, they should be removed with a soft  brush and clean water, then allowed to thoroughly dry before re-stacking. The panels should then be stored as mentioned before. Dry members should be stored on timber blocks a minimum of 50 mm above the concrete slab or tarmac. The panels should be at an incline of 1 in 100 to assist moisture dispersion.

 

 

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If long term site storage is envisaged, over 15 days, or adverse environmentalconditions such as high salinity, heavy industrial pollution, high humidity ormajor wind-blown sand, then the erector should take additional steps to protectthe panels as follows: Move panels into a weather-protected area as soon as possible.Loosely cover the  panels. Make frequent checks, between panels to avoidmoisture build-up. 8.3 What are the Procedures of checking the panels after installation ?

Once the erection of a building is complete, the following checks should be made  before hand over the customer: Check roof for debris such as screws, pop rivets, swarf, sheet metal off cuts, etc. Large items should be removed by hand, smaller items may be swept-up with a soft nylon  brush. Check roof sheets and gutters for sand build-up. This should be removed with a soft nylon brush and clean water. Any debris left by other contractors should be notified to the customer in writing, with suggested instructions for its removal. Check wall panels for wind-blown sand or zinc salt deposits. These should be removed with a soft brush and clean water. Check the base of all panels, the ground should be a minimum of 150 mm below the  bottom of the wall panel, if not, the customer should be informed in writing, this condition is detrimental to the wall panel and should be rectified immediately. Check all equipment located in, or adjacent to the wall panel. If moisture is generated or collected, such as at air conditioning units, then proper collection trays, etc. Should  be provided by the customer or the company co mpany responsible for its installation. If the panel is likely to be subjected to any kind of corrosive condition, the customer should be notified in writing with instructions to remedy the situation and a possible course of action to correct the situation. When the building is “Handed-Over” to the customer, a copy of the owners manual should be given and the customers signature received in receipt.

 

 

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Where tightening of joints should begin ? It is important to install bolts in all holes of the connection and bring them to an intermediate level of tension generally corresponding to sung tight, in order to compact the  joint. Even after being fully tightened, some thick 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 specified bolt tension is present in all bolts of the completed connection, the clamping force equal to the total of the tensions in all bolts, will be transferred at the locations  that are in contact and be fully effective in resisting slip through friction.

If however, bolts are not installed in all holes and brought to an intermediate level of tension to compact the joint, bolts which are tightened first will be subsequently relaxed  by the tightening of the adjacent bolts. Thus, Th us, the total of the forces in all bolts will be reduced which reduce the slip load whether there is uninterrupted contact between the surfaces or not. With any tightening method used, tightening should begin at the most rigidly fixed or stiffest point, and progress toward the free edges, both in the initial snugging up and in the final tightening. 8.5

What is the best method used for bolts tightening ?

As per the Research Council on Structural Connection (RCSC) specifications section 5, in order to provide more uniform tension in the bolts, a snug tight method tightening is used rather than the torque controlled tensioning methods. Consistency and reliability is dependent upon assuring that the joint is well compacted and all bolts at a snug tight condition. 8.6

What are the procedures for correct bolts tightening, tightening, using the Snug Tight method method ?

The following are the procedures to adopt for bolts tightening: Bolts in all the holes of the connection must be installed. Bring all the bolts to sung tight position. Snug tightening shall progress systematically from the most rigid part of the connection to the free edges . This procedure shall be repeated in a similar systematic manner as necessary until all bolts are simultaneously snug tight. The above snug position can be achieved in two methods: methods: Manual operation using an ordinary spud wrench. Using impact wrench

 

 

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8.7 What are the recommended Torque Values Values for the High Strength Strength Bolts ASTM ASTM A-325? The high strength bolts are intended for use in structural connection such as main frames. These connections are covered by the requirements of the Specifications for Structural Joints using ASTM A-325, approved by the Research Council on Structural Connections (RCSC) of the Engineering Foundation. The torque values indicated in the table below are not intended to be used as guidance for the high strength bolts connections, noted that PEB Steel does not endorse and is not to be held responsible for the use of the torque values indicated in the table. Please, take reference to the AISC codes chapter-5, section-8d, that do not support such values, making a very clear statement regarding this issue as follows: “This specification does not recognize standard torque determined from tables or from formulas which are assumed to relate r elate torque to tension.

a- Torque Values  Nominal Bolt

Tensile Stress

No. Of Threads

Minimum

Recommended

Diameter

Area

per

Tension

Torque Values

in (mm)

in2 (cm2)

in

lbfx103 (kN)

ft. lb. (N.m)

1/2 (12.70)

0.142 (0.92)

13

12 (53)

75 (101)

5/8 (15.88)

0.226 (1.46)

11

19 (84)

149 (201)

3/4 (19.05)

0.334 (2.15)

10

28 (125)

264 (357)

7/8 (22.23)

0.462 (2.98)

9

39 (173)

425 (526)

1 (25.40)

0.606 (3.91)

8

51 (226)

635 (861)

11/8 (28.58)

0.763 (4.92)

7

56 (249)

789 (1069)

11/2 (31.75)

0.969 (6.25)

7

71 (317)

1113 (1508)

13/8 (34.93)

1.155 (7.45)

6

85 (378)

1465 (1985)

13/4 (38.10)

1.405 (9.06)

6

103 (459)

1937 (2623)

 

 

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What are the correct procedures to prevent coating damage to the steel structures?

It is important that steel be handled properly in order to prevent damage to the coating system. Some features that can be implemented to reduce the damage to the coating system are as follows: Use clamps where possible. Use of nylon slings, rubber protected chains. Handling must only be done if the coating system has dried and cured. Order at the correct time to reduce site storage to a minimum. Store properly, prevent water contact through stacking in slopes,wrapping...etc.