Metal Roof Trusses – 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 a single object”. 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 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 truss has members and nodes that extend into three dimensions. The top beams in 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.
- 1 Types of Truss
- 2 Metal Roof Trusses Design Ideas
- 2.1 Alumunium Metal Roof Truss
- 2.2 Apartment Metal Roof Truss
- 2.3 Basket Ball Stadium Metal Roof Truss
- 2.4 Church Metal Roof Truss Black Colour
- 2.5 Best Home Metal Roof Truss Design Ideas
- 2.6 Dome Metal Roof Truss
- 2.7 Green Roof Metal Truss Design
- 2.8 Futuristic Metal Roof Truss
- 2.9 House Metal Roof Truss
- 2.10 DIY Metal Roof Truss
- 2.11 Mall Metal Roof Truss
- 2.12 Old Design Metal Roof Truss
- 2.13 Garage Metal Roof Truss
- 2.14 Public Park Metal Roof Truss with Glasses Roof
- 2.15 Red Garage Metal Roof Truss
- 2.16 Stadium Metal Roof Truss Design
- 2.17 Small Storage Metal Roof Truss
- 2.18 Swimming Pool Area Metal Roof Truss
- 2.19 Vintage Metal Roof Truss with Black Steel
- 2.20 Wooden Metal Roof Truss
- 2.21 Zinc Metal Roof Truss Design Ideas
Types of Truss
There are many types of truss, a truss consists of typically (but not necessarily) straight members connected at joints, traditionally termed panel points. In comparison, both the angles and the lengths of a four-sided figure must be fixed for it to retain its shape. The joint at which a truss is designed to be supported is commonly referred to as the Munter Point.
Simple Metal Roof Truss
The simplest form of a truss is one single triangle. This type of truss is seen in a framed roof consisting of rafters and 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 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.
Space Frame Metal Roof Trusses
A space frame truss is a three-dimensional framework of members pinned at their ends. A tetrahedron shape 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.
Planar Metal Roof Trusses
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, 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.
Truss members form a series of equilateral triangles, alternating up and down.
The Pratt truss 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 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 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 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.
King Post Truss
One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support.
Queen Post Truss
The queen post truss, sometimes queenpost or queenspost, 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.
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 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. This is preferable to a braced-frame system, which would leave some areas obstructed by the diagonal braces.
Town’s Lattice Truss
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.
Lenticular trusses, patented in 1878 by William Douglas (although the Gaunless Bridge of 1823 was 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.
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After determining 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 of the bolt connections used in the joints, see also shear stress. 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 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, 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 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.
Metal Roof Trusses Design Ideas
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Best Home Metal Roof Truss Design Ideas
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Zinc Metal Roof Truss Design Ideas
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