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89-465: In recent buildings there is a preference for trussed rafters on the grounds of cost, economy of materials, off-site manufacture, and ease of construction, as well as design considerations including span limitations and roof loads (weight from above). There are many names for rafters depending on their location, shape, or size (see below). The earliest surviving roofs in Europe are of common rafters on

178-444: A cruck frame or a couple of rafters. One engineering definition is: "A truss is a single plane framework of individual structural member [sic] connected at their ends of forms a series of triangle [sic] to span a large distance". A truss consists of typically (but not necessarily) straight members connected at joints, traditionally termed panel points . Trusses are typically (but not necessarily ) composed of triangles because of

267-412: A lattice . The Vierendeel truss is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments . As such, it does not fit the strict definition of a truss (since it contains non-two-force members): regular trusses comprise members that are commonly assumed to have pinned joints, with

356-467: A structure , particularly a building , support and shape. Framing materials are usually wood , engineered wood , or structural steel . The alternative to framed construction is generally called mass wall construction, where horizontal layers of stacked materials such as log building , masonry , rammed earth , adobe , etc. are used without framing. Building framing is divided into two broad categories, heavy-frame construction (heavy framing) if

445-424: A tie beam ; this assembly is known as a "closed couple". Later, principal rafters and common rafters were mixed, which is called a major/minor or primary/secondary roof system. Historically many rafters, including hip rafters, often tapered in height 1/5 to 1/6 of their width, with the larger end at the foot. Architect George Woodward discusses the purpose of this in 1860: "The same amount of strength can be had with

534-490: A Dimensional number two-by-four to 5 cm by 30 cm (two-by-twelve inches) at the cross-section, and lengths ranging from 2.5 metres (8.2 ft) for walls to 7 metres (23 ft) or more for joists and rafters. Recently, architects have begun experimenting with pre-cut modular aluminum framing to reduce on-site construction costs. Wall panels built of studs are interrupted by sections that provide rough openings for doors and windows . Openings are typically spanned by

623-429: A balloon frame extend two stories from sill to plate. Platform framing superseded balloon framing and is the standard wooden framing method today. The name comes from each floor level being framed as a separate unit or platform. The use of factory-made walls and floors has shown an increase in popularity due to the time-saving and cost-efficiency. ( Pre-fabrication ) Walls are made usually in facilities and then shipped to

712-445: 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 a rim joist around 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

801-476: A ceiling joist , and in other mechanical structures such as bicycles and aircraft. Because of the stability of this shape and the methods of analysis used to calculate the forces within it, a truss composed entirely of triangles is known as a simple truss. However, a simple truss is often defined more restrictively by demanding that it can be constructed through successive addition of pairs of members, each connected to two existing joints and to each other to form

890-850: A floor and as a support for the structure. Other light-frame buildings are built over a crawlspace or a basement , with wood or steel joists used to span between foundation walls, usually constructed of poured concrete or concrete 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 chipped poplar wood, in panels as thin as 1 cm (0.39 in), glued between horizontally laminated members of less than 4 cm by 4 cm ( two-by-twos ), to span distances of as much as 9 m (30 ft). Open web trussed joists and rafters are often formed of 4 cm by 9 cm ( two-by-four ) wood members to provide support for floors, roofing systems and ceiling finishes. Platform framing

979-556: A header or lintel that bears the weight of the structure above the opening. Headers are usually built to rest on trimmers , 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. Wall sections usually include

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1068-403: A larger cross section than on a previous iteration requires giving other members a larger cross section as well, to hold the greater weight of the first member—one needs to go through another iteration to find exactly how much greater the other members need to be. Sometimes the designer goes through several iterations of the design process to converge on the "right" cross section for each member. On

1157-428: A less amount of lumber. There is an additional labor in sawing such rafters, as well as a different calculation to be made in using up a log to the best advantage. It is necessary always to order this special bill of rafters direct from the mill, and the result will be that the extra cost will, nine times out of ten, overbalance the amount saved." John Muller also discussed a one-sixth taper for rafters. A piece added at

1246-402: A matrix method such as the direct stiffness method , the flexibility method , or the finite element method. Illustrated is a simple, statically determinate flat truss with 9 joints and (2 x 9) − 3 = 15 members. External loads are concentrated in the outer joints. Since this is a symmetrical truss with symmetrical vertical loads, the reactive forces at A and B are vertical, equal, and half

1335-512: A moisture content not exceeding 19%. There are four historically common methods of framing a house. Wall sheathing, usually a plywood or other laminate, is usually applied to the framing prior to erection, thus eliminating the need to scaffold , and again increasing speed and cutting manpower needs and expenses. Some types of exterior sheathing, such as asphalt-impregnated fiberboard , plywood , oriented strand board and waferboard , will provide adequate bracing to resist lateral loads and keep

1424-404: A new joint, and this definition does not require a simple truss to comprise only triangles. The traditional diamond-shape bicycle frame, which utilizes two conjoined triangles, is an example of a simple truss. A planar truss lies in a single plane . Planar trusses are typically used in parallel to form roofs and bridges. The depth of a truss, or the height between the upper and lower chords,

1513-408: A ridge. Valleys are formed when two sloping roof sections drain toward each other. Dormers are small areas in which vertical walls interrupt a roof line, and which are topped off by slopes at usually right angles to a main roof section. Gables are formed when a length-wise section of sloping roof ends to form a triangular wall section. Clerestories are formed by an interruption along the slope of

1602-649: A roof is called an A-frame . In North America, roofs are often covered with shingles made of asphalt, fiberglass and small gravel coating, but a wide range of materials are used. Molten tar is often used to waterproof flatter roofs, but newer materials include rubber and synthetic materials. Steel panels are popular roof coverings in some areas, preferred for their durability. Slate or tile roofs offer more historic coverings for light-frame roofs. Light-frame methods allow easy construction of unique roof designs; hip roofs, for example, slope toward walls on all sides and are joined at hip rafters that span from corners to

1691-550: 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 (called scuppers ) to allow water to drain out. Sloping crickets are built into roofs to direct water away from areas of poor drainage, such as behind a chimney at the bottom of a sloping section. Light-frame buildings in areas with shallow or nonexistent frost depths are often erected on monolithic concrete-slab foundations that serve both as

1780-475: A single object". A "two-force member" is a structural component where force is applied to only two points. Although this rigorous definition allows the members to have any shape connected in any stable configuration, trusses typically comprise five or more triangular units constructed with straight members whose ends are connected at joints referred to as nodes . In this typical context, external forces and reactions to those forces are considered to act only at

1869-583: A structural building that goes diagonally across a wall is called a T-bar. It stops the walls from collapsing in gusty winds. Pressure-treated wood (Green Treated wood) is a type of wood that is used when a bottom plate is exposed to outside moisture, while even when in contact with concrete. Roofs are usually built to provide a sloping surface intended to shed rain or snow, with slopes ranging from 1:15 (less than an inch per linear foot of horizontal span), to steep slopes of more than 2:1. A light-frame structure built mostly inside sloping walls which also serve as

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1958-532: A sturdy, light skeleton. Builders were reluctant to adopt the new technology; however, by the 1880s, some form of 2×4 framing was standard. Alternatively, a precursor to the balloon frame may have been used by the French in Missouri as much as 31 years earlier. 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

2047-566: A truss are called 'top chords' and are typically in compression , the bottom beams are called 'bottom chords', and are typically in tension . The interior beams are called webs , and the areas inside the webs are called panels , or from graphic statics (see Cremona diagram ) 'polygons'. Truss derives from the Old French word trousse , from around 1200 AD, which means "collection of things bound together". The term truss has often been used to describe any assembly of members such as

2136-503: A vital interior part of many roof systems, and in-wall wind braces are required by building codes in many municipalities or by individual state laws in the United States. Special framed shear walls are becoming more common to help buildings meet the requirements of earthquake engineering and wind engineering . Historically, people fitted naturally shaped wooden poles together as framework and then began using joints to connect

2225-538: Is a 393 meter (1,291 foot) long truss bridge built in 1912. The structure is composed of nine Pratt truss spans of varying lengths. The bridge is still in use today. The Wright Flyer used a Pratt truss in its wing construction, as the minimization of compression member lengths allowed for lower aerodynamic drag . Named for their shape, bowstring trusses were first used for arched truss bridges , often confused with tied-arch bridges . Thousands of bowstring trusses were used during World War II for holding up

2314-422: Is a roof or floor truss whose wood members are connected with metal connector plates . Truss members form a series of equilateral triangles, alternating up and down. Truss members are made up of all equivalent equilateral triangles. The minimum composition is two regular tetrahedrons along with an octahedron. They fill up three dimensional space in a variety of configurations. [REDACTED] The Pratt truss

2403-408: Is also likely that, by radically reducing construction costs, balloon framing improved the shelter options of poorer North Americans. However, balloon framing did require very long studs, and as tall trees were exhausted in the 1920s, platform framing became prevalent. Balloon framing presents challenges in firefighting, since many older balloon-framed buildings lack firestops or fire blocking in

2492-580: Is an early form of light framing developed from the heavier timber framing which preceded it. It is defined by the continued use of girts, corner posts, and braces. The pieces are mortised, tenoned, and pegged with the studs nailed to the girts and sills. Due to the early introduction of sawmills (as early as 1635 in New Hampshire), as early as 1637 timber frames in the northeastern English colonies in North America made use of light studs between

2581-650: Is at the floor lines. The balloon wall studs extend from the sill of the first story all the way to the top plate or end rafter of the second story. The platform-framed wall, on the other hand, is independent for each floor. Light-frame materials are most often wood or rectangular steel, tubes or C-channels. Wood pieces are typically connected with nail fasteners, nails, or screws; steel pieces are connected with pan-head framing screws, or nuts and bolts. Preferred species for linear structural members are softwoods such as spruce, pine and fir. Light frame material dimensions range from 38 by 89 mm (1.5 by 3.5 in); i.e.,

2670-645: Is not certain who introduced balloon framing in the United States. However, the first building using balloon framing was possibly a warehouse constructed in 1832 in Chicago , Illinois, by George Washington Snow or Augustine Deodat Taylor. Both men arrived in Chicago from New England, where the use of light framing timber was already common. Architectural critic Sigfried Giedion cited Chicago architect John M. Van Osdel 's 1880s attribution, as well as A. T. Andreas' 1885 History of Chicago, to credit Snow as 'inventor of

2759-496: Is preferable to a braced-frame system, which would leave some areas obstructed by the diagonal braces. A truss that is assumed to comprise members that are connected by means of pin joints, and which is supported at both ends by means of hinged joints and rollers, is described as being statically determinate . Newton's Laws apply to the structure as a whole, as well as to each node or joint. In order for any node that may be subject to an external load or force to remain static in space,

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2848-464: Is similar to a king post truss in that the outer supports are angled towards the centre of the structure. The primary difference is the horizontal extension at the centre which relies on beam action to provide mechanical stability. This truss style is only suitable for relatively short spans. Lenticular trusses, patented in 1878 by William Douglas (although the Gaunless Bridge of 1823 was

2937-422: Is the force in the member, γ is a safety factor (typically 1.5 but depending on building codes ) and σ y is the yield tensile strength of the steel used. The members under compression also have to be designed to be safe against buckling. The weight of a truss member depends directly on its cross section—that weight partially determines how strong the other members of the truss need to be. Giving one member

3026-405: Is the simplest space truss, consisting of six members that meet at four joints. Large planar structures may be composed from tetrahedrons with common edges, and they are also employed in the base structures of large free-standing power line pylons. There are two basic types of truss: A combination of the two is a truncated truss, used in hip roof construction. A metal plate-connected wood truss

3115-465: Is what makes it an efficient structural form. A solid girder or beam of equal strength would have substantial weight and material cost as compared to a truss. For a given span , a deeper truss will require less material in the chords and greater material in the verticals and diagonals. An optimum depth of the truss will maximize the efficiency. A space frame truss is a three-dimensional framework of members pinned at their ends. A tetrahedron shape

3204-524: The load and the limitations imposed by the type and thickness of the wall covering used. Wider 1 + 1 ⁄ 2 -by- 5 + 1 ⁄ 2 -inch studs may be used to provide space for more insulation . Insulation beyond that which can be accommodated within a 3 + 1 ⁄ 2 -inch stud space can also be provided by other means, such as rigid or semi-rigid insulation or batts between 1 + 1 ⁄ 2 -by- 1 + 1 ⁄ 2 -inch horizontal furring strips , or rigid or semi-rigid insulation sheathing to

3293-461: The US, most wood rafters have maximum length of 20 feet (6.1 m). If a longer rafter is needed, LVL is an alternative. Truss A truss is an assembly of members such as beams , connected by nodes , that creates a rigid structure. In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assemblage as a whole behaves as

3382-525: The balloon frame method'. In 1833, Taylor constructed the first Catholic church in Chicago, St. Mary's, using the balloon framing method; this building was moved and rehabbed multiple times before burning in the Great Chicago Fire . In the 1830s, Hoosier Solon Robinson published articles about a revolutionary new framing system, called "balloon framing" by later builders. Robinson's system called for standard 2×4 lumber, nailed together to form

3471-409: 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. Once the assembled sections are plumbed, they are nailed together at the corners and intersections. A strip of polyethylene is often placed between the interior walls and the exterior wall, and above

3560-407: The connections may also be required to transfer bending moment. Wood posts enable the fabrication of strong, direct, yet inexpensive connections between large trusses and walls. Exact details for post-to-truss connections vary from designer to designer, and may be influenced by post type. Solid-sawn timber and glulam posts are generally notched to form a truss bearing surface. The truss is rested on

3649-531: The curved roofs of aircraft hangars and other military buildings. Many variations exist in the arrangements of the members connecting the nodes of the upper arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss. One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support. The queen post truss, sometimes queenpost or queenspost ,

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3738-452: The design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding , have significantly influenced the design of modern bridges . Once the force on each member is known, the next step is to determine the cross section of the individual truss members. For members under tension the cross-sectional area A can be found using A = F × γ / σ y , where F

3827-416: The development of wall insulation. Wall framing in house construction includes the vertical and horizontal members of exterior walls and interior partitions, both of bearing walls and non-bearing walls. These stick members , referred to as studs , wall plates and lintels (sometimes called headers ), serve as a nailing base for all covering material and support the upper floor platforms, which provide

3916-456: The diagonal wind braces and the stiff exterior sheathing regardless of the type and kind of outer weather resistant coverings. A multiple-stud post of at least 3 three studs, is generally used at exterior corners and intersections to secure a good tie between adjoining walls. It provides nailing support for interior finishes and exterior sheathing. Corners and intersections, however, must be framed with at least two studs. Nailing support for

4005-545: The different job sites. This process of framing has improved the speed of framing on site moving the framing of buildings to speed up. Framed construction was rarely used in Scandinavia before the 20th century because of the abundant availability of wood, an abundance of cheap labour, and the superiority of the thermal insulation of logs. Hence timber framing was used first for unheated buildings such as farm buildings, outbuildings and summer villas, but for houses only with

4094-506: The early 19th century made balloon framing highly attractive, because it did not require highly skilled carpenters, as did the dovetail joints , mortises and tenons required by post-and-beam construction . For the first time, any farmer could build his own buildings without a time-consuming learning curve. 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. It

4183-492: The economy of the method; use of minimal structural material allows builders to enclose a large area at minimal cost while achieving a wide variety of architectural styles. Modern light-frame structures usually gain strength from rigid panels ( plywood and other plywood-like composites such as oriented strand board (OSB) used to form all or part of wall sections), but until recently carpenters employed various forms of diagonal bracing to stabilize walls. Diagonal bracing remains

4272-446: 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 or backing. Wall framing in house construction includes the vertical and horizontal members of exterior walls and interior partitions. These members, referred to as studs, wall plates and lintels, serve as a nailing base for all covering material and support

4361-403: The equilibrium condition described. Because the forces in each of its two main girders are essentially planar, a truss is usually modeled as a two-dimensional plane frame. However if there are significant out-of-plane forces, the structure must be modeled as a three-dimensional space. The analysis of trusses often assumes that loads are applied to joints only and not at intermediate points along

4450-414: The exact arrangement of forces is depending on the type of truss and again on the direction of bending. In the truss shown above right, the vertical members are in tension, and the diagonals are in compression. In addition to carrying the static forces, the members serve additional functions of stabilizing each other, preventing buckling . In the adjacent picture, the top chord is prevented from buckling by

4539-546: The first machines developed in the late 1700s in Massachusetts. Jacob Perkins of Newburyport, Massachusetts , invented a machine which could produce 10,000 nails a day. Three-decker buildings in New England were commonly constructed with this form, which is noted on period building permits as "mortised frame." Its use survived into the 1940s in the northeastern United States, when it was gradually replaced by

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4628-461: The first of the type), have the top and bottom chords of the truss arched, forming a lens shape. A lenticular pony truss bridge is a bridge design that involves a lenticular truss extending above and below the roadbed. American architect Ithiel Town designed Town's Lattice Truss as an alternative to heavy-timber bridges. His design, patented in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them, to form

4717-437: The first top plate of interior walls before the second top plate is applied to attain continuity of the air barrier when polyethylene is serving this function. 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

4806-848: The floor system for a stairwell, in which stair risers and treads are most often attached to squared faces cut into sloping stair stringers. Interior wall coverings in light-frame construction typically include wallboard , lath and plaster or decorative wood paneling . Exterior finishes for walls and ceilings often include plywood or composite sheathing, brick or stone veneers , and various stucco finishes. Cavities between studs, usually placed 40–60 cm (16–24 in) apart, are usually filled with insulation materials, such as fiberglass batting, or cellulose filling sometimes made of recycled newsprint treated with boron additives for fire prevention and vermin control. In natural building , straw bales , cob and adobe may be used for both exterior and interior walls. The part of

4895-417: The following conditions must hold: the sums of all (horizontal and vertical) forces, as well as all moments acting about the node equal zero. Analysis of these conditions at each node yields the magnitude of the compression or tension forces. Trusses that are supported at more than two positions are said to be statically indeterminate , and the application of Newton's Laws alone is not sufficient to determine

4984-557: The foot to create an overhang or change the roof pitch is called a sprocket, or coyau in French. The projecting piece on the gable of a building forming an overhang is called a lookout . A rafter can be reinforced with a strut , principal purlin , collar beam , or, rarely, an auxiliary rafter (see below). Rafter types include: Rafters are usually made of pine or cedar. For longer span rafters, building materials manufacturers have created laminated veneer lumber (LVL) rafters that can be 2–5 times longer than typical wood rafter. In

5073-483: 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 0.036 in (0.91 mm) galvanized steel plates at least 3 in (76 mm) wide and 6 in (150 mm) long, nailed with at least three 2 + 1 ⁄ 2  in (64 mm) nails to each wall. Braced frame construction , also known as full frame, half frame, New England braced frame, combination frame,

5162-417: The heavier corners. Norman Isham wrote, "sometimes the frame was covered with vertical boarding applied to the sills, plates, and girts without any intermediate framing, but in a greater number of houses the spaces between the heavier timbers are filled with lighter vertical sticks called studs." The growth of a nail-making industry in the early 19th century made the frame even faster to assemble, with some of

5251-509: The implication that no moments exist at the jointed ends. This style of structure was named after the Belgian engineer Arthur Vierendeel , who developed the design in 1896. Its use for bridges is rare due to higher costs compared to a triangulated truss. The utility of this type of structure in buildings is that a large amount of the exterior envelope remains unobstructed and can be used for windows and door openings. In some applications this

5340-479: The lateral strength along a wall. The platforms may be the boxed structure of a ceiling and roof, or the ceiling and floor joists of the story above. In the building trades, the technique is variously referred to as stick framing , stick and platform , or stick and box , as the sticks (studs) give the structure its vertical support, and the box-shaped floor sections with joists contained within length-long post and lintels (more commonly called headers ), support

5429-401: The loads supported and the type and thickness of the wall finish used. Partitions can be built with 1 + 1 ⁄ 2  in ×  2 + 1 ⁄ 2  in (38 mm × 64 mm) or 1 + 1 ⁄ 2  in ×  3 + 1 ⁄ 2  in (38 mm × 89 mm) studs spaced at 16 or 24 in (410 or 610 mm) on center depending on the type and thickness of

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5518-501: The member forces. In order for a truss with pin-connected members to be stable, it does not need to be entirely composed of triangles. In mathematical terms, the following necessary condition for stability of a simple truss exists: where m is the total number of truss members, j is the total number of joints and r is the number of reactions (equal to 3 generally) in a 2-dimensional structure. When m = 2 j − 3 {\displaystyle m=2j-3} ,

5607-562: The members means that longer diagonal members are only in tension for gravity load effects. This allows these members to be used more efficiently, as slenderness effects related to buckling under compression loads (which are compounded by the length of the member) will typically not control the design. Therefore, for given planar truss with a fixed depth, the Pratt configuration is usually the most efficient under static, vertical loading. The Southern Pacific Railroad bridge in Tempe , Arizona

5696-446: The members. Component connections are critical to the structural integrity of a framing system. In buildings with large, clearspan wood trusses, the most critical connections are those between the truss and its supports. In addition to gravity-induced forces (a.k.a. bearing loads), these connections must resist shear forces acting perpendicular to the plane of the truss and uplift forces due to wind. Depending upon overall building design,

5785-431: The members. The weight of the members is often insignificant compared to the applied loads and so is often omitted; alternatively, half of the weight of each member may be applied to its two end joints. Provided that the members are long and slender, the moments transmitted through the joints are negligible, and the junctions can be treated as " hinges " or "pin-joints". Under these simplifying assumptions, every member of

5874-427: The minimum cross section of the members, the last step in the design of a truss would be detailing of the bolted joints , e.g., involving shear stress of the bolt connections used in the joints. Based on the needs of the project, truss internal connections (joints) can be designed as rigid, semi rigid, or hinged. Rigid connections can allow transfer of bending moments leading to development of secondary bending moments in

5963-477: The nodes and result in forces in the members that are either tensile or compressive . For straight members, moments ( torques ) are explicitly excluded because, and only because, all the joints in a truss are treated as revolutes , as is necessary for the links to be two-force members. A planar truss is one where all members and nodes lie within a two-dimensional plane, while a space frame has members and nodes that extend into three dimensions . The top beams in

6052-432: The notches and bolted into place. A special plate/bracket may be added to increase connection load transfer capabilities. With mechanically-laminated posts, the truss may rest on a shortened outer-ply or on a shortened inner-ply. The later scenario places the bolts in double shear and is a very effective connection. Framing (construction) Framing , in construction , is the fitting together of pieces to give

6141-410: The open framing cavities, and a fire can spread vertically in a short time. Since the floor framing and wall framing cavities interconnect, fire can rapidly spread throughout the structure. Many balloon-framed buildings predate the introduction of building codes that mandate fire blocking, and a fire can spread from basement to attic in minutes. The main difference between platform and balloon framing

6230-460: The opening may be bridged with a single piece of 1 + 1 ⁄ 2  in (38 mm) lumber the same width as the studs. These members provide a nailing support for wall finish, door frames and trim . Lintels (or, headers) are the horizontal members placed over window, door and other openings to carry loads to the adjoining studs. Lintels are usually constructed of two pieces of 2 in (nominal) (38 mm) lumber separated with spacers to

6319-438: The other hand, reducing the size of one member from the previous iteration merely makes the other members have a larger (and more expensive) safety factor than is technically necessary, but doesn't require another iteration to find a buildable truss. The effect of the weight of the individual truss members in a large truss, such as a bridge, is usually insignificant compared to the force of the external loads. After determining

6408-637: The outside of the studs. The studs are attached to horizontal top and bottom wall plates of 1 + 1 ⁄ 2 -inch lumber that are the same width as the studs. Interior partitions supporting floor , 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 + 1 ⁄ 2  in ×  3 + 1 ⁄ 2  in (38 mm × 89 mm) lumber spaced at 16 in (410 mm) on center. This spacing may be changed to 12 or 24 in (300 or 610 mm) depending on

6497-529: The platform frame. Balloon framing is a method of wood construction used primarily in areas rich in softwood forests such as Scandinavia , Canada , the United States up until the mid-1950s, and around Thetford Forest in Norfolk, England . The name comes from a French Missouri type of construction, maison en boulin , boulin being a French term for a horizontal scaffolding support. It

6586-425: The presence of bracing and by the stiffness of the web members. The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence

6675-406: The relation (a) is necessary, it is not sufficient for stability, which also depends on the truss geometry, support conditions and the load carrying capacity of the members. Some structures are built with more than this minimum number of truss members. Those structures may survive even when some of the members fail. Their member forces depend on the relative stiffness of the members, in addition to

6764-400: The same function as the flanges of an I-beam . Which chord carries tension and which carries compression depends on the overall direction of bending . In the truss pictured above right, the bottom chord is in tension, and the top chord in compression. The diagonal and vertical members form the truss web , and carry the shear stress . Individually, they are also in tension and compression,

6853-404: The structural stability of that shape and design. A triangle is the simplest geometric figure that will not change shape when the lengths of the sides are fixed. In comparison, both the angles and the lengths of a four-sided figure must be fixed for it to retain its shape. The simplest form of a truss is one single triangle. This type of truss is seen in a framed roof consisting of rafters and

6942-402: The timbers, a method today called traditional timber framing or log framing . In the United States, timber framing was superseded by balloon framing beginning in the 1830s. Balloon framing makes use of many lightweight wall members called studs rather than fewer, heavier supports called posts; balloon framing components are nailed together rather than fitted using joinery . The studs in

7031-421: The total load. The internal forces in the members of the truss can be calculated in a variety of ways, including graphical methods: A truss can be thought of as a beam where the web consists of a series of separate members instead of a continuous plate. In the truss, the lower horizontal member (the bottom chord ) and the upper horizontal member (the top chord ) carry tension and compression , fulfilling

7120-415: The truss is said to be statically determinate , because the ( m +3) internal member forces and support reactions can then be completely determined by 2 j equilibrium equations, once we know the external loads and the geometry of the truss. Given a certain number of joints, this is the minimum number of members, in the sense that if any member is taken out (or fails), then the truss as a whole fails. While

7209-519: The truss is then subjected to pure compression or pure tension forces – shear, bending moment, and other more-complex stresses are all practically zero. Trusses are physically stronger than other ways of arranging structural elements, because nearly every material can resist a much larger load in tension or compression than in shear, bending, torsion, or other kinds of force. These simplifications make trusses easier to analyze. Structural analysis of trusses of any type can readily be carried out using

7298-583: The upper floors, ceiling and roof. Exterior wall studs are the vertical members to which the wall sheathing and cladding are attached. They are supported on a bottom plate or foundation sill and in turn support the top plate. Studs usually consist of 1 + 1 ⁄ 2 -by- 3 + 1 ⁄ 2 -inch (38 mm × 89 mm) or 1 + 1 ⁄ 2 -by- 5 + 1 ⁄ 2 -inch (38 mm × 140 mm) lumber and are commonly spaced at 16 inches (410 mm) on center. This spacing may be changed to 12 or 24 inches (300 or 610 mm) on center depending on

7387-493: The vertical supports are few and heavy such as in timber framing , pole building framing , or steel framing ; or light-frame construction (light-framing) if the supports are more numerous and smaller, such as balloon , platform , light-steel framing and pre-built framing. Light-frame construction using standardized dimensional lumber has become the dominant construction method in North America and Australia due to

7476-499: The wall finish used. Where a partition does not contain a swinging door, 1 + 1 ⁄ 2  in ×  3 + 1 ⁄ 2  in (38 mm × 89 mm) studs at 16 in (410 mm) on center are sometimes used with the wide face of the stud parallel to 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

7565-457: The wall square (construction codes in most jurisdictions require a stiff plywood sheathing). Others, such as rigid glass-fiber, asphalt-coated fiberboard, polystyrene or polyurethane board, will not. In this latter case, the wall should be reinforced with a diagonal wood or metal bracing inset into the studs. In jurisdictions subject to strong wind storms (hurricane countries, tornado alleys ) local codes or state law will generally require both

7654-417: The weight of whatever is above, including the next wall up and the roof above the top story. The platform also provides 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. In some countries, framing lumber is subject to regulated standards that require a grade-stamp, and

7743-458: The width of the studs and nailed together to form a single unit. Lintels are predominately nailed together without spacers to form a solid beam and allow the remaining cavity to be filled with insulation from the inside. The preferable spacer material is rigid insulation. The depth of a lintel is determined by the width of the opening and vertical loads supported. The complete wall sections are then raised and put in place, temporary braces added and

7832-482: Was also known as "Chicago construction" in the 19th century. Balloon framing uses long continuous framing members ( wall studs ) that run from the sill plate to the top plate, with intermediate floor structures let into and nailed to them. Here the heights of window sills, headers and next floor height would be marked out on the studs with a story pole . Once popular when long lumber was plentiful, balloon framing has been largely replaced by platform framing . It

7921-415: Was patented in 1844 by two Boston railway engineers, Caleb Pratt and his son Thomas Willis Pratt . The design uses vertical members for compression and diagonal members to respond to tension . The Pratt truss design remained popular as bridge designers switched from wood to iron, and from iron to steel. This continued popularity of the Pratt truss is probably due to the fact that the configuration of

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