pile cap reinforcement formworkwhat is a pile cap? A pile cap is a thick concrete mat that rests on piles and is usually part of the foundation of a building especially a multi-storey building. It helps to distribute the load from the pillars or piers to the piles.Typical dimensions: 5m wide x 800mm thickConcrete used: Grade 40/20Nominal concrete cover to re-bars: 75mm blinding layer for undersideMinimum cover to re-bars for precast concrete covers on topside: 30mmThickness of all precast concrete covers: 125mmThe pile caps were casted by employing a pump truck with hydraulic boom placer to pump fresh concrete from truckmixer down to cap formwork at Pok Fu Lam Road level.Nominal concrete cover to re-bars: 50mm, with a 75mm blinding layer below the underside as wellConcreting operation for the pile caps was launched simultaneously using two different methods: one by crane-and-skip bucket and the other by hydraulic excavator, in order to achieve faster placing rates.Formwork is the term used for the temporary timber, plywood, metal or other material used to contain, support and form wet concrete until it has gained sufficient strength to be self-supporting. Falsework is the term used to describe the temporary system or systems of support for formwork.

reference:http://www.ask.com/question/what-is-a-pile-caphttp://civcal.media.hku.hk/queenmary/structures/trough/pile_cap/default.htmhttp://civcal.media.hku.hk/queenmary/structures/bridge/cap/default.htm

manufactured steel trusses

lift slabsLift slab constructionis a method of constructing concrete buildings by casting the floor or roof slab on top of the previous slab and then raising (jacking) the slab up withhydraulic jacks, so being cheaper and faster as not requiring boxing and supports for casting in situ.Johnstone Hall, a dormitory atClemson University,Clemson,South Carolinawas erected using this method in 1954. Several of the blocks have now been demolished, and campus legend says that that two other similar structures built elsewhere collapsed before completion.[citation needed]The method was involved in theL'Ambiance Plazacollapse inBridgeport, Connecticutduring construction in 1987, and resulted in a major nationwide federal investigation into this construction technique in the United States, and a temporary moratorium of its use in Connecticut.[1]A patent was issued toTom Slickfor this construction method, called the "Youtz-Slick" method, in 1955.

what is lift slab construction?Ba s i c a l l y, the method entails casting floor and ro o f slabs on or at ground level and jacking them up into position. The traditional lift slab construction sequence isi l l u s t rated in Fi g u re 1. Flat plate floors are commonly used because they are so well suited to stack-casting, req u i ring form w o rk at only the edges of the slab and at floor openings.Special lifting collars or shearheads are provided inthe slabs at the columns. Bond breaking compounds areapplied between slabs to separate them. After the slabsh a ve cured long enough to reach a pre s c ribed stre n g t h ,p owe rful hyd raulic jacks mounted on top of the columnslift the slabs into their re s p e c t i ve positions. A consoleconnected to each hyd raulic jack synchro n i zes the number of turns of the check nuts to assure that the concre t eslab is being raised the same amount at all points.Lift slab can be used for heights up to about 16 stori e s. Economical column spacing ranges from 22 to 32feet. Columns may be pipe, tubes or wide flange sections; concrete columns may be used in 3- to 4-storybuildings not re q u i ring splices.The big advantage of erecting concrete buildings using lift slab construction is elimination of most formw o rk, an especially important factor in areas where laborcosts are high. Co n c rete floor construction at groundlevel is convenient and requires no shore s, scaffolds orc ra n e s. Slabs can be cast and protected easily duri n gcold weather without expensive heating and enclosure sre q u i red for ord i n a ry construction. Another advantage isreduced handling and hoisting of materials and suppliesthat can simply be placed on top of the slabs and liftedwith them.Because lift slab uses concre t e, the technique offersgood fire resistance and good acoustic ra t i n g s. Mass designed into walls, floors and roofs helps to reduce theNew developments inlift slab construction

Figure 1. The lift slab technique reduces costs for multistory buildings by eliminating most formwork. A typical liftingsequence is illustrated above.

Figure 2. Recent changes in lift slab construction include supporting the hydraulic jack off the column by a welded plate. The old approach used jacks mounted on top of the columns. Columns can now be up to 6 stories tall without field splices.

Figure 3. A lift slab system used extensively in Latin America involves casting concrete bearing walls flat in the stack along with the floor slabs. The wall panels are hinged to the floor with plastic rope, allowing them to unfold automatically as the stack is raised into position.

reference:http://en.wikipedia.org/wiki/Lift_slab_constructionhttp://www.concreteconstruction.net/images/New%20Developments%20in%20Lift%20Slab%20Construction_tcm45-343687.pdfhttp://books.google.com.ph/books?id=bC7KMKKyPbEC&pg=PT8&lpg=PT8&dq=lift+slabs&source=bl&ots=an3slS0iwW&sig=XLSV03v5xqNPkTAlsVh02Em2pXs&hl=en&sa=X&ei=C2rhUdyDCsWxrAeJm4HoDw&ved=0CFQQ6AEwCA (jep daytoi kut han ku maala nga mayat daytoi kompleto . . .google books gamin isu nga haan maala. . .)

steel space deck roofWhat is Steel Deck ? There are a wide variety of steel deck products on the market today, basically divided into two categories: roof deck and composite floor deck. Steel deck is a structural panel element that acts as the surface of a floor or roof. The deck is roll formed from structural quality sheet steel and is engineered to span over joist or purlins. Variations in the thickness, shape and depth of the deck can be utilized to meet a variety of loading conditions and spans. The deck can also be fastened to the supporting structure to enable it act as a diaphragm and provide lateral bracing for the structure.Advantages of Steel DeckVersatility: Steel deck products are available from CSSBI Fabricator member companies in a range of depths (38 to 76 mm, (1-1/2 to 3 in.)) and different rib spacing. Roof deck can also be supplied as acoustical deck with perforations in the web elements to attenuate sound. Steel deck products are available in a variety of thickness to meet most structural requirements. This extensive choice of options makes steel deck applicable to a wide range of projects and structural designs.

High Strength to Weight Ratio: The strength of steel is used with maximum efficiency in the design and fabrication of steel deck, resulting in products with a high strength-to-weight ratio. Consequently, delivery, erection and structural framing costs can be lower than other systems.

Aesthetics: Although steel deck is primarily a structural component, it is visually attractive when left exposed to the interior of the building. With the properly specified prefinished coating, steel deck is easy to maintain, durable and aesthetically pleasing.

All-Weather Construction: Steel deck can be erected inmost weather conditions, eliminating the costly delaysthat can occur with other types of roof systems.

Required Fire Resistance Ratings: ULC and UL fire resistance ratings are available for many standard roof and floor assemblies incorporating steel deck.

Uniform Quality: Through engineering and continuously refined production techniques, CSSBI fabricators produce deck that conforms to explicit industry standards.

Proven Durability: Steel deck has a successful servicehistory of over 60 years, which is indicative of theproducts durability.

Economy and Value: Value is determined by combininginitial costs, life-cycle costs, and overall performance. Steel deck assemblies are the best value in roof and floor designs. They combine low cost with top performance

SECTION 05 31 23 - STEEL ROOF DECKING PART 1 - GENERAL 1.1 SUMMARY A. Furnish all materials and labor necessary to complete metal decking installation per the Contract Documents. Edit list of related sections for project requirements. Section numbers and titles are those recommended in CSI MasterFormat; revise numbers and titles to reflect actual sections in Project Manual. B. Related Requirements: 1. Section 03 52 16: Lightweight Insulating Concrete. 2. Section 05 10 00: Structural Metal Framing. 3. Section 05 20 00: Metal Joist. 4. Section 07 22 16: Roof Board Insulation. 5. Section 07 60 00: Flashing and Sheet Metal. 6. Section 09 91 00: Painting 1.2 REFERENCE STANDARDS FOR QUALITY ASSURANCE A. Codes/Standards The work and materials of this section shall comply with: 1. ASCE 7: Minimum Design Loads for Building and Other Structures. 2. Section properties shall be derived in accordance with AISI "North American Specification for the Design of Cold-Formed Steel Structural Members", latest edition. 3. Metal Decking is to be attached to the structural frame in conformance with AWS D1.1 "Structural Welding Code Steel" and D1.3 "Structural Welding Code Sheet Steel." 4. ICC Research Report No. ESR-1414. 5. IAPMO Research Report No. IAPMO ES-0161 Insert the appropriate L.A. City Research Report No. when applicable; 23783, 23784, 23803. 6. ASTM A653, "Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process". 7. Steel Deck Institute (SDI) Metal roof deck profiles shall be in conformance with ANSI/SDI standard RD1.0 "Standard for Steel Roof Deck". 8. Factory Mutual (FM) Metal roof deck profiles shall be in conformance with FM where applicable. ASC Steel Deck, A Division of ASC Profiles, Inc. STEEL ROOF DECK PANELS Guide Specification 05 31 23 - 2 1.3 SUBMITTALS A. Product Data for each type of decking specified, including dimensions of individual components, profiles, and finishes. B. Shop drawings: Prior to fabrication, prepare shop drawings for work under this section and submit to Architect. Shop drawings are to include deck layout, deck type and gauge, framing and support of openings, dimensions and sections, details of accessories and type and location of welds. Manufacturers product literature and relevant approvals are to be submitted with the shop drawings. 1.4 PRODUCT DELIVERY, STORAGE AND HANDLING A. Metal Deck: Transport, store and erect metal deck and accessories in a manner that will prevent corrosion, deformation or other damage. Store deck clear of the ground with one end elevated to promote drainage; protect metal deck from water and the elements with a water resistant material. Include the following when Acustadek is specified: B. Acustadek Sound Absorption Batts: Store batts in an enclosed area, protected from the elements. PART 2 - PRODUCTS 2.1 MATERIAL AND FINISHESA. Metal roof deck to be ASC Steel Deck [select appropriate profile(s) and gauge(s)]. 1. B-36 [22], [20], [18], [16] gauge;1 1/2 inches deep by 36 inches wide. 2. N-32 [22], [20], [18], [16] gauge; 3 inches deep by 32 inches wide. 3. N-24 [22], [20], [18], [16] gauge; 3 inches deep by 24 inches wide. 4. 2W-36 [22], [20], [18], [16] gauge; 2 inches deep x 36 inches wide. 5. 3W-36 [22], [20], [18], [16] gauge; 3 inches deep by 36 inches wide. 6. BF-36 [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 1 1/2 inches deep by 36 inches wide. 7. NF-24 [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 3 inches deep by 24 inches wide. Deck units are to be fabricated from sheet steel conforming to ASTM A653 SS Grade 40 with a galvanized coating. 2W-36 and 3W-36 are available in 24 wide panels; when specified, the designations are 2W-24 and 3W-24. When specifying CP-32, use the following, for CP-32 18 gauge; replace ASTM A653 SS Grade 80 with ASTM A653 Grade 33. 7. CP-32 [26], [24], [22], [20], [18] gauge; 1 3/8 inches deep by 32 inches wide. Deck units are to be fabricated from sheet steel conforming to ASTM A653 SS Grade 80, with a G-40 galvanized coating. When specifying Deep Deck and Deep Cellular, using the following: 1. Deep Deck [20], [18], [16], [14] gauge; 4 1/2, 6, or 7 1/2 inches deep by 12 inches wide. 2. Deep Deck Cellular [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16]gauge; 4 1/2, 6, or 7 1/2 inches deep by 24 inches wide. Deck units are to be fabricated from sheet steel confirming to ASTM A653, Fy = 33ksi with a galvanized coating. When specifying acoustical deck use the following: ASC Steel Deck, A Division of ASC Profiles, Inc. STEEL ROOF DECK PANELS Guide Specification 05 31 23 - 3 A. Metal roof deck to be ASC Steel Deck [select appropriate profile(s) and gauge(s).]1. B-36 Acustadek [22], [20], [18], [16] gauge, 1 1/2 inches deep by 36inches wide. 2. N-32 Acustadek [22], [20], [18], [16] gauge, 3inches deep by 32 inches wide. 3. N-24 Acustadek [22], [20], [18], [16] gauge, 3 inches deep by 24 inches wide. 4. BF-36 Acustadek [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 1 1/2 inches deep by 36 inches wide. 5. NF-24 Acustadek [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 3 inches deep by 24 inches wide. 6. Deep Deck Acustadek [20], [18], [16], [14] gauge; 4 1/2, 6, or 7 1/2 inches deep by 12 inches wide. 7. Deep Deck Cellular Acustadek [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 4 1/2, 6, or 7 1/2 inches deep by 24 inches wide. 8. 2WF-36 Acustadek [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 2 inches deep by 36 inches wide. 9. 3WF-36 Acustadek [20/20], [20/18], [20/16], [18/20], [18/18], [18/16], [16/16] gauge; 3 inches deep by 36 inches wide. B. Acustadek perforations are 1/8 or 5/32 diameter holes on staggered centers. The noise reduction Coefficient is to be [select from chart on pages 23 and 24]. The NRC values were developed in accordance with ANSI C423, as performed by Riverbank Laboratory. ASC Steel Deck panels, in their standard sheet steel, contain approximately 24.3 percent postconsumer recycled content and 9.4 percent pre-consumer recycled content, for a total 29 percent recycled content as calculated for this LEED credit. Higher percentages are available if specified. B. [Or C. for acoustical deck] Sustainability Characteristics: 1. Recycled Content: [29] [50] [75] percent post-consumer recycled content [, calculated according to LEED Credit MR4]. 2. Shipping Distance: Provide panels manufactured at the following factory: If locally manufactured materials are a project requirement, select factory closer to Project site. a. Fontana, California 92335 b. West Sacramento, California 95691 If the project is subject to Federal Buy American provisions, which requires that panels be manufactured in the USA and that 50 percent of the cost of the panels be of U.S.A. origin, use the following: C. [Or D. for acoustical deck] Manufacturing Characteristics: Provide panels complying with provisions of Buy American Act 41 U.S. C 10a 10d. If the project is subject to Buy America Act (STAA) or American Recovery & Reinvestment Act (ARRA) 2009 (which requires that steel used in the manufacturing process be poured and melted in the USA, use the following: C. [Or D. for acoustical deck] Manufacturing Characteristics: Provide panels complying with provisions of the Buy America Act (STAA) or the American Recovery & Reinvestment Act (ARRA) 2009. 2.2 FABRICATION A. Metal Deck Manufacture deck units to lengths as indicated on shop drawings. Panel end conditions are to be butted or end-lapped, 2 minimum. Sidelaps are to be male/female interlocking type allowing connection with DeltaGrip tool. Sidelaps are to be nestable or interlocking when using screw-type fasteners. When specifying CP-32 delete the last two sentences and insert: Sidelaps are to be overlapping type. B. Accessories Fabricate steel deck accessories (not including cell closures) from the same gauge and materials as adjacent steel deck.reference:http://www.cssbi.ca/Eng/_pdf/CSSBI-S15-01.pdfhttp://www.ascsd.com/files/Roof%20Deck%20Guide%20Specs.pdf

space framesInarchitectureandstructural engineering, aspace frameorspace structureis atruss-like, lightweight rigid structure constructed from interlockingstrutsin ageometricpattern. Space frames can be used to span large areas with few interior supports. Like thetruss, a space frame is strong because of the inherent rigidity of the triangle; flexingloads(bendingmoments) are transmitted astensionandcompressionloads along the length of each strut.

If a force is applied to the blue node, and the red bar is not present, the behaviour of the structure depends completely on the bending rigidity of the blue node. If the red bar is present, and the bending rigidity of the blue node is negligible compared to the contributing rigidity of the red bar, the system can be calculated using a rigidity matrix, neglecting angular factors.

Simplified space frame roof with the half-octahedron highlighted in blue

The roof of this industrial building is supported by a space frame structure.

Advantages of Space Frames1. One of the most important advantages of a space structure is its lightweight. This is mainly due tothe fact that material is distributed spatially in such a way that the load transfer mechanism isprimarily axial tension or compression. Consequently, all material in any given element isutilized to its full extent. Furthermore, most space frames are now constructed with steel oraluminum, which decreases considerably their self-weight. This is especially important in the caseof long-span roofs, which led to a number of notable examples of applications.2. The units of space frames are usually mass produced in the factory so that they can take fulladvantage of the industrialized system of construction. Space frames can be built from simpleprefabricated units, which are often of standard size and shape. Such units can be easilytransported and rapidly assembled on site by semi-skilled labor. Consequently, space frames canbe built at a lower cost.SecondarybeamBeamBeamArch(a) (b)PurlinFIGURE 24.2 Roof framing for a Circular Dome.24-4 Handbook of Structural EngineeringCopyright 2005 by CRC Press3. A space frame is usually sufciently stiff in spite of its lightness. This is due to itsthree-dimensional character and to the full participation of its constituent elements. Engineersappreciate the inherent rigidity and great stiffness of space frames and their exceptional ability toresist unsymmetrical or heavy concentrated load. Possessing greater rigidity, the space framesallow also greater exibility in layout and positioning of columns.4. Space frames possess a versatility of shape and form and can utilize a standard module to generatevarious at space grids, latticed shell, or even free-form shapes. Architects appreciate the visualbeauty and the impressive simplicity of lines in space frames. A trend is very noticeable in whichthe structural members are left exposed as a part of the architectural expression. Desire foropenness for both visual impact as well as the ability to accommodate variable space requirementsalways calls for space frames as the most favorable solution.

Preliminary Planning GuidelinesIn the preliminary stage of planning a space frame to cover a specic building, a number of factorsshould be studied and evaluated before proceeding to structural analysis and design. These include notonly structural adequacy and functional requirements but also the esthetic effect desired.1. In its initial phase, structural design consists of choosing the general form of the building and thetype of space frame appropriate to this form. Since a space frame is assembled of straight, linearelements connected at nodes, the geometrical arrangement of the elements surface shape,number of layers, grid pattern, etc.needs to be studied carefully in the light of various pertinentrequirements.2. The geometry of the space frame is an important factor to be planned, which will inuence boththe bearing capacity and the weight of the structure. Themodulesize is developed from the overallbuilding dimensions, while the depth of the grid (in the case of double-layer), the size of cladding,and the position of the supports will also have a pronounced effect upon it. For curved surface, thegeometry is also related to the curvature, or more specically to the rise of the span. A compromisebetween these various aspects usually has to be made to achieve a satisfactory solution.3. In a space frame, connecting joints play an important role, both functional and esthetic, whichderives from their rationality during construction and after completion. Since joints have adecisive effect on the strength and stiffness of the structure and compose around 20 to 30% of thetotal weight, joint design is critical to space frame economy and safety. These are quite a fewproprietary systems that are used for space frame structures. They should be selected on the basisof quality, cost, and erection efciency. In addition, custom-designed space frames have beendeveloped, especially for long-span roofs. Regardless of the type of space frame, the essence of anysystem is the jointing system.4. At the preliminary stage of design, the choosing of the type of space frames has to be closely relatedwith the constructional technology. The space frames do not have such a sequential order oferection for planar structures and require special consideration on the method of construction.Usually, a complete falsework has to be provided so that the structure can be assembled in the highposition. Alternatively, the structure can be assembled on the ground, and a certain technique canbe adopted to lift the whole structure, or its major part, to the nal position.reference:http://en.wikipedia.org/wiki/Space_framehttp://img20.imageshack.us/img20/5880/ch24spaceframestructure.pdf

cold roll-formed sections welded togetherCold-formed steel (CFS)is the common term for products made by rolling or pressing thin gauges of sheet steel into goods. Cold-formed steel goods are created by the working of sheet steel using stamping, rolling, or presses to deform the sheet into a usable product. Cold worked steel products are commonly used in all areas of manufacturing of durable goods like appliances or automobiles but the phrase cold form steel is most prevalently used to described construction materials. The use of cold-formed steel construction materials has become more and more popular since its initial introduction of codified standards in 1946. In the construction industry both structural and non-structural elements are created from thin gauges of sheet steel. These building materials encompass columns, beams, joists, studs, floor decking, built-up sections and other components. Cold-formed steel construction materials differ from other steel construction materials known as hot-rolled steel (seestructural steel). The manufacturing of cold-formed steel products occurs at room temperature using rolling or pressing. The strength of elements used for design is usually governed by buckling. The construction practices are more similar to timber framing using screws to assemble stud frames.

Cold-formed steel buildingCold-formed steel members have been used in buildings, bridges, storage racks,grain bins, car bodies, railway coaches, highway products, transmission towers, transmission poles,drainagefacilities, various types of equipment and others.[1]These types of sections are cold-formed from steel sheet, strip, plate, or flat bar inroll formingmachines, by press brake (machine press) or bending operations. The material thicknesses for such thin-walled steel members usually range from 0.0147 in. (0.373mm) to about in. (6.35mm). Steel plates and bars as thick as 1 in. (25.4mm) can also be cold-formed successfully into structural shapes (AISI, 2007b). History of cold-formed steelThe use of cold-formed steel members in building construction began in the 1850s in both the United States and Great Britain. In the 1920s and 1930s, acceptance of cold-formed steel as a construction material was still limited because there was no adequate design standard and limited information on material use in building codes. One of the first documented uses of cold-formed steel as a building material is the Virginia Baptist Hospital[1], constructed around 1925 in Lynchburg, Virginia. The walls were load bearing masonry, but the floor system was framed with double back-to-back cold-formed steel lipped channels. According to Chuck Greene, P.E of Nolen Frisa Associates[2], the joists were adequate to carry the initial loads and spans, based on current analysis techniques. Greene engineered a recent renovation to the structure and said that for the most part, the joists are still performing well. A site observation during this renovation confirmed that "these joists from the 'roaring twenties' are still supporting loads, over 80 years later!" In the 1940s, Lustron Homes built and sold almost 2500 steel-framed homes, with the framing, finishes, cabinets and furniture made from cold-formed steel.

History of AISI design standards[edit]Design standards for hot-rolled steel (seestructural steel) were adopted in 1930s, but were not applicable to coldformed sections because of their relatively thin steel walls which were susceptible to buckling. Cold-formed steel members maintain a constant thickness around their cross-section, whereas hot-rolled shapes typically exhibit tapering or fillets. Cold-formed steel allowed for shapes which differed greatly from the classical hot-rolled shapes. The material was easily workable; it could be deformed into many possible shapes. Even a small change in the geometry created significant changes in the strength characteristics of the section. It was necessary to establish some minimum requirements and laws to control the buckling and strength characteristics. Also it was observed that the thin walls underwent local buckling under small loads in some sections and that these elements were then capable of carrying higher loads even after local buckling of the members.In the United States, the first edition of the Specification for the Design of Light Gage Steel Structural Members was published by theAmerican Iron and Steel Institute(AISI) in 1946 (AISI, 1946).[3]The firstAllowable Stress Design(ASD) Specification was based on the research work sponsored by AISI atCornell Universityunder the direction of late Professor George Winter[3]since 1939.[4]As a result of this work, George Winter is now considered the grandfather of cold-formed steel design. The ASD Specification was subsequently revised in 1956, 1960, 1962, 1968, 1980, and 1986 to reflect the technical developments and the results of continued research at Cornell and other universities (Yu et al., 1996).[5]In 1991, AISI published the first edition of theLoad and Resistance Factor DesignSpecification developed atUniversity of Missouriof Rolla andWashington Universityunder the directions of Wei-Wen Yu[4]and Theodore V. Galambos (AISI, 1991).[6]Both ASD and LRFD Specifications were combined into a single specification in 1996 (AISI, 1996).[7]In 2001, the first edition of the North American Specification for the Design of Cold-Formed Steel Structural Members was developed by a joint effort of the AISI Committee on Specifications, theCanadian Standards Association(CSA) Technical Committee on Cold-Formed Steel Structural Members, and Camara Nacional de la Industria del Hierro y del Acero (CANACERO) in Mexico (AISI, 2001).[8]It included the ASD and LRFD methods for the United States and Mexico together with the Limit States Design (LSD) method for Canada. This North American Specification has been accredited by the American National Standard Institute (ANSI) as an ANSI Standard to supersede the 1996 AISI Specification and the 1994 CSA Standard. Following the successful use of the 2001 edition of the North American Specification for six years, it was revised and expanded in 2007.[9]This updated specification includes new and revised design provisions with the additions of the Direct Strength Method in Appendix 1 and the Second-Order Analysis of structural systems in Appendix 2.In addition to the AISI specifications, theAmerican Iron and Steel Institutehas also published commentaries on various editions of the specifications, design manuals, framing design standards, various design guides, and design aids for using cold-formed steel. For details, see AISI[5]website.Common section profiles and applications[edit]In building construction there are basically two types of structural steel: hot-rolled steel shapes and cold-formed steel shapes. The hot rolled steel shapes are formed at elevated temperatures while the cold-formed steel shapes are formed at room temperature. Cold-formed steel structural members are shapes commonly manufactured from steel plate, sheet metal or strip material. The manufacturing process involves forming the material by eitherpress-brakingorcold roll formingto achieve the desired shape.When steel is formed by press-braking or cold rolled forming, there is a change in the mechanical properties of the material by virtue of the cold working of the metal. When a steel section is cold-formed from flat sheet or strip the yield strength, and to a lesser extent the ultimate strength, are increased as a result of this cold working, particularly in the bends of the section.Some of the main properties of cold formed steel are as follows:[10] Lightness in weight High strength and stiffness Ease of prefabrication and mass production Fast and easy erection and installation Substantial elimination of delays due to weather More accurate detailing Non shrinking and non creeping at ambient temperatures No formwork needed Termite-proof and rot proof Uniform quality Economy in transportation and handling Non combustibility Recyclable material Panels and decks can provide enclosed cells for conduits.

A broad classification of the cold-formed shapes used in the construction industry can be made as individual structural framing members or panels and decks.Some of the popular applications and the preferred sections are: Roof and wall systems (industrial, commercial, and agricultural buildings) Steel racks for supporting storage pallets Structural members for plane and space trusses Frameless Stressed skin structures: Corrugated sheets or sheeting profiles with stiffened edges are used for small structures up to a 30ft clear span with no interior frameworkCFS Decking

CFS purlins

CFS X-braced wall system

CFS stud/girt wall connectionThe AISI Specification allows the use of steel to the following ASTM specifications in the table below:[11]Steel DesignationASTM DesignationProductYield Strength Fy (ksi)Tensile Strength Fu (ksi)Fu / FyMinimum Elongation (%) in 2-in. Gage Length

Carbon structural steelA363658-801.6123

A3650701.421

High-strength low-alloy Structural steelA24246671.4621

Low and intermediate tensile strength carbon steel platesA283

A2445-601.8830

B2750-651.8528

C3055-751.8325

D3360-801.8223

Cold-formed welded and seamless carbon steel structural tubing in rounds and shapesA500Round Tubing

A33451.3625

B42581.3823

C46621.3521

D36581.6123

Shape Tubing

A39451.1525

B46581.2623

C50621.2421

D36581.6123

High-strength carbonmanganese steelA529 Gr. 424260-851.4322

A529 Gr. 505070-1001.4021

Hot-rolled carbon steel sheets and strips of structural qualityA570

Gr. 3030491.6321

Gr. 3333521.5818

Gr. 3636531.4717

Gr. 4040551.3815

Gr. 4545601.3313

Gr. 5050651.3011

High-strength low-alloy columbium vanadium steels of structural qualityA572

Gr. 4242601.4324

Gr. 5050651.3021

Gr. 6060751.2518

Gr. 6565801.2317

High-strength low-alloy structural steel with 50 ksi minimum yield pointA58850701.4021

Hot-rolled and cold-rolled high-strength low-alloy steel sheet and strip with improved corrosion resistanceA606Hot-rolled as rolled cut length50701.4022

Hot-rolled as rolled coils45651.4422

Hot-rolled annealed45651.4422

Cold-rolled45651.4422

Hot-rolled and cold-rolled high-strength low-alloy columbium and/or vanadium steel sheet and stripA607 Class I

Gr.4545601.33Hot rolled (23)Cold rolled (22)

Gr.5050651.30Hot rolled (20)Cold rolled (20)

Gr.5555701.27Hot rolled (18)Cold rolled (18)

Gr.6060751.25Hot rolled (16)Cold rolled (16)

Gr.6565801.23Hot rolled (14)Cold rolled (15)

Gr.7070851.21Hot rolled (12)Cold rolled (14)

A607 Class II

Gr.4545551.22Hot rolled (23)Cold rolled (22)

Gr.5050601.20Hot rolled (20)Cold rolled (20)

Gr.5555651.18Hot rolled (18)Cold rolled (18)

Gr.6060701.17Hot rolled (16)Cold rolled (16)

Gr.6565751.15Hot rolled (14)Cold rolled (15)

Gr.7070801.14Hot rolled (12)Cold rolled (14)

Cold-rolled carbon structural steel sheetA611

A25421.6826

B30451.5024

C33481.4522

D40521.3020

Zinc-coated or zinc-iron alloy-coated steel sheetA653 SS

Gr. 3333451.3620

Gr. 3737521.4118

Gr. 4040551.3816

50 Class 150651.3012

50 Class 350701.4012

HSLAS Type A

5050601.2020

6060701.1716

7070801.1412

8080901.1310

HSLAS Type B

5050601.2022

6060701.1718

7070801.1414

8080901.1312

Hot-rolled and cold-rolled high-strength low-alloy steel sheets and strip with improved formabilityA715

Gr. 5050601.2022

Gr. 6060701.1718

Gr. 7070801.1414

Gr. 8080901.1312

55% aluminum-zinc alloy-coated steel sheet by the hot-dip processA792

Gr. 3333451.3620

Gr. 3737521.4118

Gr. 4040551.3816

Gr. 50A50651.3012

Cold-formed welded and seamless high-strength, low-alloy structural tubing with improved atmospheric corrosion resistanceA84750701.4019

Zinc-5% aluminum alloy-coated steel sheet by the hot-dip processA875 SS

Gr. 3333451.3620

Gr. 3737521.4118

Gr. 4040551.3816

50 Class 150651.3012

50 Class 350701.4012

HSLAS Type A

5050601.2020

6060701.1716

7070801.1412

8080901.1310

HSLAS Type B

5050601.2022

6060701.1718

7070801.1414

8080901.1312

Typical stressstrain properties[edit]A main property of steel, which is used to describe its behavior, is the stressstrain graph. The stressstrain graphs of cold-formed steel sheet mainly fall into two categories. They are sharp yielding and gradual yielding type illustrated below in Fig.1 and Fig.2, respectively.

These two stressstrain curves are typical for cold-formed steel sheet during tension test. The second graph is the representation of the steel sheet that has undergone the cold-reducing (hard rolling) during manufacturing process, therefore it does not exhibit a yield point with a yield plateau. The initial slope of the curve may be lowered as a result of the prework. Unlike Fig.2, the stressstrain relationship in Fig.1 represents the behavior of annealed steel sheet. For this type of steel, the yield point is defined by the level at which the stressstrain curve becomes horizontal.Cold forming has the effect of increasing the yield strength of steel, the increase being the consequence of cold working well into the strain-hardening range. This increase is in the zones where the material is deformed by bending or working. The yield stress can be assumed to have been increased by 15% or more for design purposes. The yield stress value of cold-formed steel is usually between 33ksi and 80ksi. The measured values ofModulus of Elasticitybased on the standard methods usually range from29,000 to 30,000 ksi (200 to 207 GPa). A value of 29,500 ksi (203 GPa) is recommended by AISI in its specification for design purposes. The ultimate tensile strength of steel sheets in the sections has little direct relationship to the design of those members. The load-carrying capacities of cold-formed steel flexural and compression members are usually limited by yield point or buckling stresses that are less than the yield point of steel, particularly for those compression elements having relatively large flat-width ratios and for compression members having relatively large slenderness ratios. The exceptions are bolted and welded connections, the strength of which depends not only on the yield point but also on the ultimate tensile strength of the material. Studies indicate that the effects of cold work on formed steel members depend largely upon the spread between the tensile and the yield strength of the virgin material.Ductility criteria[edit]Ductilityis defined as an extent to which a material can sustain plastic deformation without rupture. It is not only required in the forming process but is also needed for plastic redistribution of stress in members and connections, where stress concentration would occur. The ductility criteria and performance of low-ductility steels for cold-formed members and connections have been studied byDhalla,Winter, andErreraatCornell University. It was found that the ductility measurement in a standard tension test includes local ductility and uniform ductility. Local ductility is designated as the localized elongation at the eventual fracture zone. Uniform ductility is the ability of a tensioncouponto undergo sizeable plastic deformations along its entire length prior to necking. This study also revealed that for the different ductility steels investigated, the elongation in 2-in. (50.8-mm) gage length did not correlate satisfactorily with either the local or the uniform ductility of the material. In order to be able to redistribute the stresses in the plastic range to avoid premature brittle fracture and to achieve full net-section strength in a tension member with stress concentrations, it is suggested that: The minimum local elongation in a - 12 in. (12.7-mm) gauge length of a standard tension coupon including the neck be at least 20%. The minimum uniform elongation in a 3-in. (76.2-mm) gauge length minus the elongation in a 1-in. (25.4-mm) gage length containing neck and fracture be at least 3%. The tensile-strength-to-yield-point ratio Fu /Fy be at least 1.05.Weldability[edit]Weldability refers to the capacity of steel to be welded into a satisfactory, crack free, sound joint under fabrication conditions without difficulty.[1]Weldingis possible in cold-formed steel elements, but it shall follow the standards given in AISIS100-2007, Section E.1.When thickness less than or equal to 3/16 (4.76mm):The various possible welds in cold formed steel sections, where the thickness of the thinnest element in the connection is 3/16 or less are as follows Groove Welds in Butt joints Arc Spot Welds Arc Seam Welds Fillet Welds Flare Groove Welds2.When thickness greater than or equal to 3/16 (4.76mm):Welded connections in which thickness of the thinnest connected arc is greater than 3/16 (4.76mm) shall be in accordance withANSI/AISC-360. The weld positions are covered as perAISI S100-2007(Table E2a)[9]Minimum material thickness recommended for welding connections[edit]ApplicationShoporField fabricationElectrodemethodSuggested minimum CFS thickness

CFS toStructural steelField-fabricationStick-welding54 mils to 68 mils

CFS toStructural steelShop-fabricationStick-welding54 mils to 68 mils

CFS to CFSField-fabricationStick-welding54 mils to 68 mils

CFS to CFSField-fabricationWire-fed MIG (Metal Inert Gas) welding43 mils to 54 mils

CFS to CFSShop-fabricationWire-fed MIG (Metal Inert Gas) welding33 mils

[12]Application in buildings[edit]Cold-formed steel framing[edit]Cold-formed steel framing (CFSF) refers specifically to members in light-frame building construction that are made entirely of sheet steel, formed to various shapes at ambient temperatures. The most common shape for CFSF members is a lipped channel, although Z, C, tubular, hat and other shapes and variations have been used. The building elements that are most often framed with cold-formed steel are floors, roofs, and walls, although other building elements and both structural and decorative assemblies may be steel framed.Although cold-formed steel is used for several products in building construction, framing products are different in that they are typically used for wall studs, floor joists, rafters, and truss members. Examples of cold-formed steel that would not be considered framing includes metal roofing, roof and floor deck, composite deck, metal siding, and purlins and girts on metal buildings.Framing members are typically spaced at 16 or 24inches on center, with spacing variations lower and higher depending upon the loads and coverings. Wall members are typically vertical lipped channel stud members, which fit into unlipped channel track sections at the top and bottom. Similar configurations are used for both floor joist and rafter assemblies, but in a horizontal application for floors, and a horizontal or sloped application for roof framing. Additional elements of the framing system include fasteners and connectors, braces and bracing, clips and connectors.In North America, member types have been divided into five major categories, and product nomenclature is based on those categories. S members are lipped channels, most often used for wall studs, floor joists, and ceiling or roof rafters. T members are unlipped channels, which are used for top and bottom plates (tracks) in walls, and rim joists in floor systems. Tracks also form the heads and sills of windows, and typically cap the top and bottom of boxed- or back-to-back headers. U members are unlipped channels that have a smaller depth than tracks, but are used to brace members, as well as for ceiling support systems. F members are furring or hat channels, typically used horizontally on walls or ceilings. L members are angles, which in some cases can be used for headers across openings, to distribute loads to the adjacent jamb studs.In high-rise commercial and multi-family residential construction, CFSF is typically used for interior partitions and support of exterior walls and cladding. In many mid-rise and low-rise applications, the entire structural system can be framed with CFSF.Connectors and fasteners in framing[edit]Connectors are used in cold-formed steel construction to attach members (i.e.studs,joists) to each other or to the primary structure for the purpose of load transfer and support. Since an assembly is only as strong as its weakest component, it is important to engineer each connection so that it meets specified performance requirements. There are two main connection types,Fixed and Movement-Allowing(Slip). Fixed connections of framing members do not allow movement of the connected parts. They can be found in axial-load bearing walls, curtain walls, trusses, roofs, and floors. Movement-Allowing connections are designed to allow deflection of the primary structure in the vertical direction due to live load, or in the horizontal direction due to wind or seismic loads, or both vertical and horizontal directions. One application for a vertical movement-allowing connection is to isolate non-axial load bearing walls (drywall) from the vertical live load of the structure and to prevent damage to finishes. If the structure is in an active seismic zone, vertical and horizontal movement-allowing connections may be used to accommodate both the vertical deflection and horizontal drift of the structure.Connectors may be fastened to cold-formed steel members and primary structure using welds, bolts, or self-drilling screws. These fastening methods are recognized in the American Iron and Steel Institute (AISI) 2007 North American Specification for the Design of Cold-Formed Steel Structural Members, Chapter E. Other fastening methods, such as clinching, power actuated fasteners (PAF), mechanical anchors, adhesive anchors and structural glue, are used based on manufacturer's performance-based tests.Hot-rolled versus cold-rolled steel and the influence of annealing[edit]Hot rolledCold rolled

Material propertiesYielding strengthThe material is not deformed; there is no initial strain in the material, hence yielding starts at actual yield value as the original material.The yield value is increased by 15%30% due to prework (initial deformation).

Modulus of elasticity29,000 ksi29,500 ksi

Unit weightUnit weight is comparatively huge.It is much smaller.

DuctilityMore ductile in nature.Less ductile.

DesignMost of the time, we consider only the global buckling of the member.Local buckling, Distortional Buckling, Global Buckling have to be considered.

Main usesLoad bearing structures, usually heavy load bearing structures and where ductility is more important ( Example Seismic prone areas)Application in many variety of loading cases. This includes building frames, automobile, aircraft, home appliances, etc. Use limited in cases where high ductility requirements.

Flexibility of shapesStandard shapes are followed. High value of unit weight limits the flexibility of manufacturing wide variety of shapes.Any desired shape can be molded out of the sheets. The light weight enhances its variety of usage.

EconomyHigh Unit weight increases the overall cost material, lifting, transporting, etc. It is difficult to work with (e.g. connection).Low unit weight reduces the cost comparatively. Ease of construction (e.g. connection).

Research possibilitiesIn the advanced stages at present.More possibilities as the concept is relatively new and material finds wide variety of applications.

Annealing, also described in the earlier section, is part of the manufacturing process of cold-formed steel sheet. It is aheat treatmenttechnique that alters the microstructure of the cold-reducing steel to recover itsductility.reference:http://en.wikipedia.org/wiki/Cold-formed_steel

welded built-up columnsBuilt-up columns are used in steel construction when the column buckling lengths are large and the compression forces are relatively low. This guide covers two types of built-up columns: Built-up columns with lacing Built-up columns with battens. This document includes an overview of common details for such members. It describes the design method according to EN 1993-1-1[1] for the determination of the internal forces and the buckling resistance of each member (chords, diagonals, etc) of built-up columns made of hot rolled profiles. It should be noted that due to the shear deformation, battened built-up columns are more flexible than solid columns with the same inertia; this must be taken into account in the design. In order to derive the axial resistance of a steel built-up column, the following must be addressed: Analysis of the built-up column to determine the internal forces by taking into account an equivalent initial imperfection and the second order effects Verification of the chords and bracing members (diagonals and battens) Verification of the connections. A fully worked example of a built-up column with an N-shape arrangement of lacings is given in Appendix A, which illustrates the design principles.

TYPES OF BUILT-UP MEMBERS AND THEIR APPLICATION 2.1 General In general, built-up columns are used in industrial buildings, either as posts for cladding when their buckling length is very long, or as columns supporting a crane girder. When used as a post for cladding with pinned ends, the column is designed to support the horizontal forces, mainly due to wind. Hence the bending moment in such a built-up column is predominant compared to the compression force.

A typical built-up column that supports a crane girder is shown in Figure 2.2.They usually have a fixed base and a pinned end at the top, and are designed toresist: The compression forces that result either from the frame or from the cranerail The horizontal forces that result from the effects of the crane applied on theinternal chord and the wind loads applied to the external one.In this case, the compression forces are predominant compared to the bendingmoment.

The built-up columns are composed of two parallel chords interconnected bylacings or battens see Figure 2.1. In general, the truss system concentratesmaterial at the structurally most efficient locations for force transfer.In an industrial building and for a given height, built up columns theoreticallyhave the least steel weight of any steel framing system.Any hot rolled section can be used for the chords and the web members ofbuilt-up columns. However, channels or I-sections are most commonly used aschords. Their combination with angles presents a convenient technical solutionfor built-up columns with lacing or battens. Flat bars are also used in built-upcolumn as battens.This guide covers two types of built-up columns with pinned ends that areassumed to be laterally supported: Laced columns Battened columns.

The difference between these two types of built-up columns comes from themode of connection of the web members (lacings and battens) to the chords.The first type contains diagonals (and possibly struts) designed with pinnedends. The second type involves battens with fixed ends to the chords andfunctioning as a rectangular panel.The inertia of the built-up column increases with the distance between thechord axes. The increase in stiffness is counterbalanced by the weight and costincrease of the connection between members.Built-up columns provide relatively light structures with a large inertia. Indeed,the position of the chords, far from the centroid of the built-up section, is verybeneficial in producing a great inertia. These members are generally intendedfor tall structures for which the horizontal displacements are limited to lowvalues (e.g. columns supporting crane girders).The axial resistance of built-up columns is largely affected by the sheardeformations. The initial bow imperfection is significantly amplified becauseof the shear strains.It is possible to study the behaviour of built-up columns using a simple elasticmodel.

Laced built-up columns2.2.1 GeneralThere is a large number of laced column configurations that may beconsidered. However, the N-shape and the V-shape arrangements of lacings arecommonly used.

Figure 2.4 Built-up column with lacings in an industrial building

The selection of either channels or I-sections for chord members providesdifferent advantages. I-sections are more structurally efficient and therefore arepotentially shallower than channels. For built-up columns with a largecompressive axial force (for example, columns supporting cranes), I orH sections will be more appropriate than channels. Channels may be adequatein order to provide two flat sides.Tee sections cut from European Column sections are also used for the chordmembers. The web of the Tee sections should be sufficiently deep to permiteasy welding of the bracing members.The angle web members of the laced column allow use of gusset-less weldedconnections, which minimises fabrication costs. Other member types requireeither gussets or more complex welding.The centroidal axes of the compression and tension web members are notnecessarily required to meet at the same point on the chord axes. In fact, lacedcolumns with an eccentricity at the joints can be as efficient as those withouteccentricity. The chord-web joint can be separated without an increase in steelweight. Although eccentric joints require that local moments be designed for,there are several advantages in doing so. Eccentric joints provide additionalspace for welding, hence reducing fabrication complexity. In addition, thereduced length of the compression chord provides enhanced buckling andbending resistance which partly compensates for the additional momentsgenerated by the joint eccentricity. For single angles, it is recommended thatjoint eccentricity is minimised.

2.2.2 Various lacing geometriesThe N-shape arrangement of lacings, as shown in Figure 2.5(a), can beconsidered as the most efficient truss configuration, for typical frames inindustrial buildings. The web of the N-shape arrangement comprises diagonalsand posts that meet at the same point on the chord axes.This arrangement reduces the length of the compression chords and diagonals.It is usually used in frames with a significant uniform compressive force.The V-shape arrangement of lacings increases the length of the compressionchords and diagonals and provides a reduction of buckling resistance of themembers. This arrangement is used in frames with a low compressive force.The X-shape configurations are not generally used in buildings because of thecost and the complexity of fabrication.

\2.2.3 Construction detailsSingle lacing systems on opposite faces of the built-up member with twoparallel laced planes should be corresponding systems as shown inFigure 2.6(a) (EN 1993-1-1 6.4.2.2(1)).When the single lacing systems on opposite faces of a built-up member withtwo parallel laced planes are mutually opposed in direction, as shown inFigure 2.6(b), the resulting torsional effects in the member should be taken intoaccount. The chords must be designed for the additional eccentricity caused bythe transverse bending effect, which can have a significant influence on themember size.Tie panels should be provided at the ends of lacing systems, at points where thelacing is interrupted and at joints with other members.

2.3 Battened built-up columnsBattened built-up columns are not appropriate for frames in industrialbuildings. They are sometimes used as isolated frame members in specificconditions, where the horizontal forces are not significant.Channels or I-sections are mostly used as chords and flat bars are used asbattens. The battens must have fixed ends on the chords.Battened built-up columns are composed of two parallel planes of battenswhich are connected to the flanges of the chords. The position of the battensshould be the same for both planes. Battens should be provided at each end ofthe built-up member.Battens should also be provided at intermediate points where loads are applied,and at points of lateral restraint.

reference:http://www.arcelormittal.com/sections/fileadmin/redaction/4-Library/4-SBE/EN/SSB06_Detailed_design_of_built-up_columns.pdf

hallow precast floor beamsAhollow core slab, also known as avoided slaborhollow core plank, is aprecastslab ofprestressed concretetypically used in the construction offloorsin multi-storyapartment buildings. The slab has been especially popular in countries where the emphasis of home construction has been on precast concrete, including Northern Europe andsocialist countriesofEastern Europe. Precast concrete popularity is linked with low-seismic zones and more economical constructions because of fast building assembly, lower self weight (less material), etc.Theprecast concreteslab has tubular voids extending the full length of the slab, typically with a diameter equal to the 2/3-3/4 of the slab. This makes the slab much lighter than a massive floor slabs of equal thickness or strength. Reduced weight is important because of transportation cost and less cost of material (concrete). The slabs are typically 120cm wide with standard thicknesses between 15cm and 50cm. The precast concreteI-beamsbetween the holes contain the steel wire rope that provide bending resistance to bending moment from loads.Slabs in prestressed concrete are usually produced in lengths of about 120 meters. The process involvesextrudingwet concrete along with the prestressed steel wire rope from a movingmold. The continuous slab is then cut by big diamond circular saw according to the lengths (and width) required on blueprint. Factory production provides the obvious advantages of reduced time, labor and training. Another fabrication system produces hollow-core floorslabs in Reinforced Concrete (not prestressed). These are made on carousel production lines, directly to exact length, and as a stock product. Although the length is limited to about 7-8 metre, this type is much more cost effective (needs less people, and is faster). Especially in Belgium, this method is widely used in private housing.To meet modern standards (both hollow-core and massive slab) ofsoundproofingthe floor needs to be covered with a softfloor coveringthat is able to dampen the sound of footsteps. An alternative is to use a thin "floating" slab of concrete insulated from the voided slabs.

Diagram of a concrete slab of hollow core constructionHollowcore benefitsClear, unpropped spansFast and simple to erectProvides an immediate working platformCan be used in all types of structure Masonry, steel and concreteExcellent sound and fire resistanceEasier installation of servicesHoles and notches preformed during manufactureQuality service guaranteedAvailable nationwide either supply only or supply and fixFactory manufacture to consistent quality standards Complies with all relevant standards and manufactured in accordance with BS EN ISO 9001 and BS EN ISO140001

referencehttp://en.wikipedia.org/wiki/Hollow-core_slabhttp://www.heidelbergcement.com/NR/rdonlyres/DECAC297-B027-4E60-A7C0-7BCF29AEDC19/0/Flooring_Hollowcore.pdfprecast prestressed concrete floor units

steel ring spacer

floor reinforcement cage

precast concrete wall frame

stud framesFraming, in construction known aslight-frame construction, is a building technique based around vertical structural members, usually calledstuds, which provide a stable frame to which interior and exteriorwallcoverings are attached, and covered by aroofmade of horizontal ceilingjoistsand slopingrafters(or pre-fabricated rooftrusses).Modern light-frame structures usually gain strength from rigid panels (plywoodand other plywood-like composites such asoriented strand board(OSB) used to form all or part of wall sections) but until recentlycarpentersemployed various forms of diagonal bracing (calledwind braces) to stabilize walls. Diagonal bracing remains a vital interior part of many roof systems, and in-wall wind braces are required by building codes in many municipalities or by individualstate lawsin the United States.Light frame construction using standardizeddimensional lumberhas become the dominant construction method inNorth AmericaandAustraliabecause of itseconomy. Use of minimal structural materials allows builders to enclose a large area with minimal cost, while achieving a wide variety of architectural styles. The ubiquitousplatform framingand the olderballoon framingare the two different light frame construction systems used in North America.

A wooden-frame house under construction in this example of platform framing the location of the upper floor is readily discerned by the wide joists between the floors, and the upper structure rests on this platform.Walls[edit]Wall framing in house construction includes the vertical and horizontal members of exterior walls and interior partitions, both ofbearing wallsand non-bearing walls. Thesestickmembers, referred to asstuds,wall platesandlintels(headers), serve as a nailing base for all covering material and support the upper floor platforms, which provide the lateral strength along a wall. The platforms may be the boxed structure of aceilingand roof, or the ceiling andfloorjoistsof the story above.[1]The technique is variously referred to colloquially in the building trades asstick and frame,stick and platform, orstick and boxas the sticks (studs) give the structure its vertical support, and the box shaped floor sections with joists contained within length-longpost and lintels(more commonly calledheaders), supports the weight of whatever is above, including the next wall up and the roof above the top story. The platform also provides the lateral support against wind and holds the stick walls true and square. Any lower platform supports the weight of the platforms and walls above the level of its component headers and joists.Framinglumbershould be grade-stamped, and have a moisture content not exceeding 19%.[2]There are three historically common methods of framing a house. Post and beam, which is now used predominately in barn construction. Balloon framing using a technique suspending floors from the walls was common until the late 1940s, but since that time,platform framinghas become the predominant form of house construction.[3] Platform framing often forms wall sections horizontally on the sub-floor prior to erection, easing positioning of studs and increasing accuracy while cutting the necessary manpower. The top and bottom plates are end-nailed to each stud with two nails at least 3.25in (83mm) in length (16dor16 pennynails). Studs are at least doubled (creating posts) at openings, the jack stud being cut to receive the lintels(headers) that are placed and end-nailed through the outer studs.[3]Wall sheathing, usually a plywood or other laminate, is usually applied to the framing prior to erection, thus eliminating the need toscaffold, and again increasing speed and cutting manpower needs and expenses. Some types of exterior sheathing, such as asphalt-impregnatedfibreboard,plywood,oriented strand boardandwaferboard, will provide adequate bracing to resist lateral loads and keep the wall square. (Construction codes in most jurisdictions require a stiff plywood sheathing.) Others, such as rigid glass-fibre, asphalt-coated fibreboard,polystyreneorpolyurethaneboard, will not.[1]In this latter case, the wall should be reinforced with a diagonal wood or metal bracing inset into the studs.[4]In jurisdictions subject to strong wind storms (hurricane countries,tornado alleys) local codes or state law will generally require both the diagonalwind bracesand the stiff exterior sheathing regardless of the type and kind of outer weather resistant coverings.Corners[edit]A multiple-stud post made up of at least three studs, or the equivalent, is generally used at exterior corners and intersections to secure a good tie between adjoining walls and to provide nailing support for the interior finish and exterior sheathing.Cornersand intersections, however, must be framed with at least two studs.[5]Nailing support for the edges of the ceiling is required at the junction of the wall and ceiling where partitions run parallel to the ceiling joists. This material is commonly referred to as 'dead wood'[6]or backing.Exterior wall studs[edit]Wall framing in houseconstructionincludes the vertical and horizontal members of exterior walls and interior partitions. These members, referred to asstuds, wall plates and lintels, serve as a nailing base for all covering material and support the upper floors, ceiling and roof.[1]Exterior wall studs are the vertical members to which the wall sheathing andcladdingare attached.[7]They are supported on a bottom plate or foundation sill and in turn support the top plate. Studs usually consist of 1.5in 3.5in (38mm 89mm) or 1.5in 5.5in (38mm 140mm) lumber and are commonly spaced at 16in (410mm) on centre. This spacing may be changed to 12in (300mm) or 24in (610mm) on centre depending on theloadand the limitations imposed by the type and thickness of the wall covering used. Wider 1.5in 5.5in (38mm 140mm) studs may be used to provide space for moreinsulation. Insulation beyond that which can be accommodated within a 3.5in (89mm) stud space can also be provided by other means, such as rigid or semi-rigid insulation or batts between 1.5in 1.5in (38mm 38mm) horizontalfurring strips, or rigid or semi-rigid insulation sheathing to the outside of the studs. The studs are attached to horizontal top and bottom wall plates of 1.5in (38mm) lumber that are the same width as the studs.[2]Interior partitions[edit]Interior partitions supportingfloor, ceiling or roof loads are called loadbearing walls; others are called non-loadbearing or simply partitions. Interior loadbearing walls are framed in the same way as exterior walls. Studs are usually 1.5in 3.5in (38mm 89mm) lumber spaced at 16in (410mm) on centre. This spacing may be changed to 12in (300mm) or 24in (610mm) depending on the loads supported and the type and thickness of the wall finish used.[5]Partitions can be built with 1.5in 2.5in (38mm 64mm) or 1.5in 3.5in (38mm 89mm) studs spaced at 16 or 24in (400 or 600mm) on center depending on the type and thickness of the wall finish used. Where a partition does not contain a swinging door, 1.5in 3.5in (38mm 89mm) studs at 16in (410mm) on centre are sometimes used with the wide face of the studparallelto the wall. This is usually done only for partitions enclosing clothes closets or cupboards to save space. Since there is no vertical load to be supported by partitions, single studs may be used at door openings. The top of the opening may be bridged with a single piece of 1.5in (38mm) lumber the same width as the studs. These members provide a nailing support for wall finish, door frames andtrim.[5]Lintels (headers)[edit]Lintels (or, headers) are the horizontal members placed over window, door and other openings to carry loads to the adjoining studs.[1]Lintels are usually constructed of two pieces of 2in (nominal) (38mm) lumber separated with spacers to the width of the studs and nailed together to form a single unit. The preferable spacer material is rigid insulation.[7]The depth of a lintel is determined by the width of the opening and vertical loads supported.Wall sections[edit]The complete wall sections are then raised and put in place, temporary braces added and the bottom plates nailed through the subfloor to the floor framing members. The braces should have their larger dimension on the vertical and should permit adjustment of the vertical position of the wall.[4]Once the assembled sections are plumbed, they are nailed together at the corners and intersections. A strip ofpolyethyleneis often placed between the interior walls and the exterior wall, and above the first top plate of interior walls before the second top plate is applied to attain continuity of theair barrierwhen polyethylene is serving this function.[4]A second top plate, with joints offset at least one stud space away from the joints in the plate beneath, is then added. This second top plate usually laps the first plate at the corners and partition intersections and, when nailed in place, provides an additional tie to the framed walls. Where the second top plate does not lap the plate immediately underneath at corner and partition intersections, these may be tied with 0.036in (0.91mm) galvanized steel plates at least 3in (76mm) wide and 6in (150mm) long, nailed with at least three 2.5in (64mm) nails to each wall.[4]Balloon framing[edit]

Balloon framing is a method ofwoodconstruction also known as "Chicago construction" in the 19th century[8] used primarily inScandinavia,Canadaand theUnited States(up until the mid-1950s). It utilizes long continuous framing members (studs) that run from thesill plateto the top plate, with intermediate floor structures let into and nailed to them.[9][10]Here the heights of window sills, headers and next floor height would be marked out on the studs with astorey pole. Once popular when long lumber was plentiful, balloon framing has been largely replaced byplatform framing.It is not certain who introduced balloon framing in the United States. However, the first building using balloon framing was probably a warehouse constructed in 1832 inChicago,Illinois, byGeorge Washington Snow.[11]The following year, Augustine Taylor (17961891) constructed St. Mary's Catholic Church inChicagousing the balloon framing method.In the 1830s,HoosierSolon Robinson published articles about a revolutionary new framing system, called balloon framing by later builders. Robinsons system called for standard 2x4 lumber, nailed together to form a sturdy, light skeleton. Builders were reluctant to adopt the new technology, however, by the 1880s, some form of 2x4 framing was standard.[12]Alternatively, the balloon frame has been shown to have been introduced in Missouri as much as fifty years earlier.[13]The name comes from a French Missouri type of construction,maison enboulin,[13]boulinbeing a French term for a horizontal scaffolding support. Historians have also fabricated the following story:[14]As Taylor was constructing his first such building, St. Mary's Church, in 1833, skilled carpenters looked on at the comparatively thin framing members, all held together with nails, and declared this method of construction to be no more substantial than a balloon. It would surely blow over in the next wind! Though the criticism proved baseless, the name stuck.[15]Although lumber was plentiful in 19th-century America, skilled labor was not. The advent of cheap machine-made nails, along with water-powered sawmills in the early 19th century made balloon framing highly attractive, because it did not require highly-skilled carpenters, as did thedovetail joints,mortises and tenonsrequired bypost-and-beam construction. For the first time, any farmer could build his own buildings without a time-consuming learning curve.[16]It has been said that balloon framing populated the western United States and the western provinces of Canada. Without it, western boomtowns certainly could not have blossomed overnight.[17]It is also a fair certainty that, by radically reducing construction costs, balloon framing improved the shelter options of poorer North Americans.[citation needed]For example, many 19th-centuryNew Englandworking neighborhoods consist of balloon-constructed three-story apartment buildings referred to astriple deckers.

A very unusual example of balloon framing: The Jim Kaney Round Barn, Adeline, Illinois, U.S.A.The main difference between platform and balloon framing is at the floor lines. The balloon wallstudsextend from the sill of the first story all the way to thetop plateorend rafterof the second story. The platform-framed wall, on the other hand, is independent for each floor.[18]Balloon framing has several disadvantages as a construction method:1. The creation of a path for fire to readily travel from floor to floor. This is mitigated with the use of firestops at each floor level.2. The lack of a working platform for work on upper floors. Whereas workers can readily reach the top of the walls being erected with platform framing, balloon construction requires scaffolding to reach the tops of the walls (which are often two or three stories above the working platform).3. The requirement for long framing members.4. In certain larger buildings, a noticeable down-slope of floors towards central walls, caused by the differential shrinkage of the wood-framing members at the perimeter versus central walls. Larger balloon-framed buildings will have central bearing walls which are actually platform framed and thus will have horizontal sill and top plates at each floor level, plus the intervening floor joists, at these central walls. Wood will shrink much more across its grain than along the grain. Therefore, the cumulative shrinkage in the center of such a building is considerably more than the shrinkage at the perimeter where there are many fewer horizontal members. This problem, unlike the first three, takes time to develop and become noticeable.5. Present-day balloon framing buildings often have higher heating costs, due to the lack of insulation separating a room from its exterior walls. However, this can be remedied through the addition of insulation, as with any other framed building.Since steel is generally more fire-resistant than wood, and steel framing members can be made to arbitrary lengths, balloon framing is growing in popularity again in light gauge steel stud construction. Balloon framing provides a more direct load path down to the foundation. Additionally, balloon framing allows more flexibility fortradesmenin that it is significantly easier to pull wire, piping and ducting without having to bore through or work around framing members.[citation needed]Platform framing[edit]In Canada and the United States, the most common method of light-frame construction forhousesand smallapartment buildingsas well as other small commercial buildings isplatform framing. In builder parlance, platform framing might also nowadays be called (only partly correctly) 'stick framing'or 'stick construction'as each element is built up stick by stick, which was also true in the other stick framing method, in the obsolete and labor intensive, but previously fashionable, balloon framing method, wherein the outside walls were erected, headers hung, then floor joists were inserted into a box made of walls.In contrast, in platform framing a floor box and joists making up the platform is built and placed on a supporting under structure (Sill plates, headers, or beams) where it sits flat and gets fastened down against wind lifting with galvanized metal tie straps. Once the boxed floor platform is squared, leveled and fastened thensubfloor,walls,ceilings, androofare built onto and above that initial platform, which can be repeated floor by floor, 'without the slow downs and dangers of fastening and leveling rough-sawn joists of a new floor together to the walls from ladders extending one or even twostoriesup.Generally, the flooring ('platform') is constructed then the walls built on top of that layer, then another atop that, and so forth making for quick efficient labor saving construction methodologies and those have quickened further as technologies such asjoist hangershave been developed to speed and enhance the technology. The methods and techniques have become so common and pervasive that evenSkyscrapersuse a modified form of platform framing techniques and indeed the same tools and technologies once construction builds the initial structuralskeleton. Once the platform floor is laid down, the builder's crew can with chalk line, rule and pencil directly transfer an outline of the exterior and interior walls, their openings and relative locations with ease and precision from the plans or builders blue prints.As the survey group lays down the notations and chalk lines, a carpenter crew can follow behind and lay down 2x4 'bottom plates' and tack them to the floor box. The topmost wall plates are cut only to the outside dimensions of the walls. Butting two other two by fours against these cut to size and fastened bottom plate allows the crew to rule across all three with square and lay out studs, cripple studs, and openings for that particular wall. The two loose studs are then quickly flipped on edge after openings are cut in, and studs added on the marks with quick reliable end nailing through the respective top and bottom plates. A few minutes later the whole wall section can be levered up and aligned in place and braced for later application of the top plates and adjoining walls.The method provides builders options and flexibility such as when and where there is a floor-level opening (doorway) the next wall section can be aligned and fastened in place separately with the top plate added then used then a lintel and cripple studding added, or the entire wall could have been cut and joined at the top all along and lifted up as one entity. In the end, the outside walls are plumbed and fastened together with 'ell-configured reinforced corners' that provide nailing wood in the interior angles and strength to the building forming in effect wide posts at each corner and fastened lastly by overlapped top plates which stagger their joints from the ones capping each plate by which the studs are end nailed together. Each wall from top to bottom ends up with a doubled plate, studs, and a doubled plate, where structurally the doubled plates spread the weight of the roof and loading across the studs of the wall, ultimately to the foundation.Overall, the framed structure sits (most commonly) atop aconcretefoundationonpressure treated wood 'sill', or 'beam'.When on concrete, thesill plateisanchored, usually with (embedded) 'J' bolts into the concrete substrate of the foundation wall. Generally these plates must be pressure treated to keep from rotting from condensing moisture. By various standards the bottom of thesill plateis located a minimum 6 inches (150mm) above thefinished grade(the surrounding ground) per standard builders practices, and frequently more dependent upon building codes of the relevant jurisdiction's local building codes. In North America, building codes may differ not only state to state, but town to town, the tighter specification applying at all times. This distance, together with roofing overhangs, and othersystemfactors, is most often selected both to prevent the sill-plate from rotting (due to the invasion of splashed water) as well as providing a termite barrier. The latter is particularly (more or less) important than anti-rotting considerations depending upon the geographical location.Alternatively, the room, room extension, deck or even a house can be built aboveconcrete columnsU.S. builders callpierssome others callpilasters, another of many term misuses common to building trade parlance. In such cases, the pier (column) is usually required to rest on bed rock or extend well below the zone of average freezing soil depth (the same as a foundation) locally, and frequently is required to also have flared out or mushroomed bottom of greater surface than that the pier top (These are called 'big foots' in the building trade and building suppliers carry PVC molds to conserve concrete which allow a builder to satisfy area requirements and the building codes). Rigid pressure treated 'beams' (usually doubled or tripled up wider types of 2x boards) are attached to the piers using galvanized metal brackets and serve the same function as sills in foundation supported framing.The floors, walls and roof of a framed structure are created by assembling (using nails) consistently sized framing elements ofdimensional lumber(e.g. 24s) at regular spacings (typically divisions of 4 and 8 feet, or such as 12, 16, 19.2, or 24 inches on center). The empty space formed between elements is called a stud bay in the wall and a joist bay in the floor or ceiling. The floors, walls and roof are typically made torsionally stable with the installation of a plywood or composite wood skin referred to as sheathing[citation needed]. Sheathing has very specific requirements (such as thickness and spacing of nailing). These measures allow a known amount of shear force to be resisted by the elements. Spacing the framing members properly usually allows them to align with the edges of standard sheathing. In the past,tongue and grooveplanks installed diagonally were used as sheathing. Occasionally, wooden orgalvanized steelbracesare used instead of sheathing. There are alsoengineered woodpanels made for shear and bracing.[citation needed]The floor, or the platform in this framing type's name, is made up of joists (usually 2x6, 28, 210 or 212 depending on the span, on edge thus the wider joist supporting weight for a greater distance) that sit on supporting foundation walls, beams, columns or girders within and at right angle to doubled outside members also on edge (the band), forming a box. The outer perimeter is nearly the same (3inch vs. 3.5inches) width as the support sill. The joists will generally be installed across the shortest distance of any floor span rectangle. The outer layer of the band will overlap the inner layer with staggered end joints creating a stronger box. If joist hangers are not used, the installation of the outer board in the band is delayed to allow through-nailing directly into the ends of the joists.The floor joists are spaced at 12in, 16in, and 24in on center, depending upon the live load needs of the design the closer the spacing and the wider the floor joist dimension, the less the floor will flex. It is then usually covered with a 3/4-inch tongue-and-groove plywood subfloor. In the century past, 1x planks set at 45-degrees to the joists were used for the first subfloor layer, and a second layer of 1x planks set at 90-degrees to the floor cladding topped that as the second subfloor layer. In that same era, all flooring choices were a very short menu of choices between finished wood types or ceramic tiles versus today's extensive multipage menu of manufactured flooring types.Where the design calls for a framed floor, the resulting platform is where the framer will construct and stand that floor's walls (interior and exterior load bearing walls and space-dividing, non-load bearing partitions). Additional framed floors and their walls may then be erected to a general maximum of four in wood framed construction. There will be no framed floor in the case of a single-level structure with a concrete floor known as aslab on grade.[citation needed]Stairsbetween floors are framed by installing three 90-steppedstringersattached to wall structures and then placing the horizontaltreadsand verticalrisers(usually about 14 of each for an 8-ft. ceiling) upon the planes formed by the stringers.A framed roof is an assembly of rafters and wall-ties supported by the top story's walls. Prefabricated and site-builttrussedrafters are also used along with the more common stick framing method.Trussesare engineered to redistribute tension away from wall-tie members and the ceiling members. The roof members are covered withsheathingorstrappingto form the roof deck for the finish roofing material.[citation needed]Floor joists can be engineered lumber (trussed,I-joist, etc.), conserving resources with increased rigidity and value. They are semi-custom manufactured to allow access for runs of plumbing, HVAC, etc. andsome 'common-needs' formsare pre-manufactured as semi-mass-produced standard products made on a per order basis, like roofing trusses. Such products have a post-order lead time from several weeks to several months.Double framing is a style of framing used in some areas to reduce heat loss and air infiltration. Two walls are built around the perimeter of the building with a small gap in between. The inner wall carries the structural load of the building and is constructed as described above. The exterior wall is not load bearing and can be constructed using lighter materials. Insulation is installed in the entire space between the outside edge of the exterior wall and the inside edge of the interior wall. The size of the gap depends upon how much insulation is desired. The vapor barrier is installed on the outside of the inner wall, rather than between the studs and drywall of a standard framed structure. This increases its effectiveness as it is not perforated by electrical and plumbing connections.Materials[edit]Light-frame materials are most often wood or rectangularsteeltubes or C-channels. Wood pieces are typically connected withnailsorscrews; steel pieces are connected with nuts and bolts. Preferred species for linear structural members are softwoods such asspruce,pineandfir. Light frame material dimensions range from 38mm by 89mm (1.5in by 3.5in; i.e., atwo-by-four) to 5cm by 30cm (two-by-twelve inches) at the cross-section, and lengths ranging from 2.5m (8.2ft) for walls to 7m (23ft) or more for joists and rafters. Recently, architects have begun experimenting with pre-cut modular aluminum framing to reduce on-site construction costs.[citation needed]Wall panels built of studs are interrupted by sections that provide rough openings fordoorsandwindows. Openings are typically spanned by a header or lintel that bears the weight of structure above the opening. Headers are usually built to rest ontrimmers, also called jacks. Areas around windows are defined by a sill beneath the window, and cripples, which are shorter studs that span the area from the bottom plate to the sill and sometimes from the top of the window to a header, or from a header to a top plate. Diagonal bracings made of wood or steel provide shear (horizontal strength) as do panels of sheeting nailed to studs, sills and headers.[citation needed]

Light-gauge metal stud framingWall sections usually include a bottom plate which is secured to the structure of a floor, and one, or more often two top plates that tie walls together and provide a bearing for structures above the wall. Wood or steel floor frames usually include arim joistaround the perimeter of a system of floor joists, and often include bridging material near the center of a span to prevent lateral buckling of the spanning members. In two-story construction, openings are left in the floor system for a stairwell, in which stair risers and treads are most often attached to squared faces cut into sloping stair stringers.[citation needed]Interior wall coverings in light-frame construction typically includewallboard,lath and plasteror decorativewood paneling.[citation needed]Exterior finishes for walls and ceilings often include plywood orcompositesheathing,brickorstoneveneers, and variousstuccofinishes. Cavities between studs, usually placed 4060cm (1624in) apart, are usually filled withinsulationmaterials, such asfiberglassbatting, orcellulosefilling sometimes made ofrecyclednewsprinttreated withboronadditives forfireprevention andvermincontrol.[citation needed]Innatural building,straw bales,cobandadobemay be used for both exterior and interior walls.The part of a structural building that goes diagonally across a wall is called a T-bar. It stops the walls from collapsing in gusty winds.[citation needed]Roofs[edit]Main article:RoofRoofsare usually built to provide a sloping surface intended to shed rain or snow, with slopes ranging from 1cm of rise per 15cm (less than an inch per linear foot) of rafter length, to steep slopes of more than 2cm per cm (two feet per foot) of rafter length. A light-frame structure built mostly inside sloping walls comprising a roof is called anA-frame.Roofs are most often[citation needed]covered withshinglesmade of asphalt, fiberglass and small gravel coating, but a wide range of materials are used. Moltentaris often used to waterproof flatter roofs, but newer materials include rubber and synthetic materials.Steelpanels are popular roof coverings in some areas, preferred for their durability.Slateortileroofs offer more historic coverings for light-frame roofs.Light-frame methods allow easy construction of unique roof designs. Hip roofs, which slope toward walls on all sides and are joined at hip rafters that span from corners to a ridge. Valleys are formed when two sloping roof sections drain toward each other.Dormersare small areas in which vertical walls interrupt a roof line, and which are topped off by slopes at usuallyright anglesto a main roof section.Gablesare formed when a length-wise section of sloping roof ends to form a triangular wall section.Clerestoriesare formed by an interruption along the slope of a roof where a short vertical wall connects it to another roof section. Flat roofs, which usually include at least a nominal slope to shed water, are often surrounded by parapet walls with openings (calledscuppers) to allow water to drain out. Slopingcricketsare built into roofs to direct water away from areas of poor drainage, such as behind a chimney at the bottom of a sloping section.Structure[edit]Light-frame buildings are often erected onmonolithicconcrete-slab foundations that serve both as a floor and as a support for the structure. Other light-frame buildings are built over a crawlspace or abasement, with wood or steel joists used to span between foundation walls, usually constructed of poured concrete orconcrete blocks.Engineered components are commonly used to form floor, ceiling and roof structures in place of solid wood.I-joists(closed-web trusses) are often made from laminated woods, most often chippedpoplarwood, in panels as thin as 1cm (0.4in), glued between horizontally laminated members of less than 4cm by 4cm (two-by-twos), to span distances of as much as 9m (30ft). Open web trussed joists and rafters are often formed of 4cm by 9cm (two-by-four) wood members to provide support for floors, roofing systems and ceiling finishes.reference:https://en.wikipedia.org/wiki/Framing_(construction)