Analysis of TRUSSES || TRUSS

What is Truss?

In mechanical engineering, farms are structures that "comprise only two members of strength, the members being arranged so that the whole as a whole function as one body".

"Member of 2 forces" could be a structural organ during which the forces apply solely on 2 points. Although the definition permits armour of any style, however, is connected in an exceedingly stable configuration, it includes 5 or additional triangular units designed with straight members whose ends are connected and joints are called nodes.

Two-dimensional armour is one during which all members and nodes are in an exceedingly single plane.

Within a two-dimensional plane, whereas an area truss has members and nodes that reach into 3 dimensions. The prime beams in an exceeding truss are known as top chords and are generally in compression, very cheap beams are known as bottom chords, and are typically in tension. The interior beams are known as webs, and therefore the areas within the webs are known as panels.

Types of truss/frames:

There are two basic types of truss:

(i) Pitched truss, or common truss

(ii) The parallel chord truss

The pitched truss, or common truss, is characterized by its triangular shape. It is most often used for roof construction. Some common trusses are named in keeping with their internet configuration. The chord size and internet configuration are determined by span, load, and spacing.

The parallel chord truss, or flat truss, gets its name from its parallel top and bottom chords. It is often used for floor construction.

A combination of the 2 could be a truncated truss, used in hip roof construction. A metal-plate-connected wood truss could be a roof or floor truss whose wood members are connected with metal connective plates.

Warren Truss

Truss members type a series of equal triangles, alternating up and down.

Warren Truss

Pratt Truss

The Pratt truss was proprietary in 1844 by 2 Bean Town railway engineers, Caleb Pratt and his son Thomas Willis Pratt. The design uses vertical members for compression and diagonal members to reply to tension. The Pratt truss style remained well-liked as bridge designers switched from wood to iron, and from iron to steel.

Pratt Truss

This continuing quality of the Pratt truss is perhaps because of the actual fact that the configuration of the members means longer diagonal members are solely in tension for gravity load effects. This allows these members to be used additional with efficiency, 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.

Bowstring truss

It is named for his or her form, cord trusses were 1st used for arched truss bridges, usually confused with tied-arch bridges. Thousands of cord trusses were used throughout war II for holding up the curving roofs of craft hangars and alternative military buildings.

A bowstring truss is used on the oldest metal bridge in Virginia

Many variations exist within the arrangements of the members connecting the nodes of the higher arc with those of the lower, straight sequence of members, from nearly isosceles triangles to a variant of the Pratt truss.

Kingpost Truss

Kingpost Truss

One of the best truss designs to implement, the king post consists of two angled supports leaning into common vertical support.

The post truss, sometimes queen-post or queens post is similar to a king post truss in that the outer supports are angled towards the center of the structure.

Queen-Post

The primary distinction is that the horizontal extension at the middle that depends on beam action to supply mechanical stability. This truss vogue is simply appropriate for comparatively short spans.

The Waterville Bridge:

The Waterville Bridge in Swatara State Park in Pennsylvania could be a convex truss. 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 convex pony span could be a bridge-style that involves a convex truss extending on top of and below the bed.

Waterville Bridge

American creator, Ithiel city designed Town's Lattice Truss as another to heavy-timber bridges. His design, proprietary in 1820 and 1835, uses easy-to-handle planks arranged diagonally with short spaces in between them.

Town's Lattice Truss

For additional truss sorts, see truss sorts utilized in bridges. A large timber Howe truss in an exceedingly industrial building.

Lenticular truss

Lenticular bridge includes a lens-shaped truss, it has trusses between an upper chord (functioning as an arch) that curves up and then down to end points, and a lower chord (functioning as a suspension cable) that curves down and then up to meet at the same end points.

Lenticular Truss

Vierendeel truss

A Vierendeel bridge that lacks diagonal parts within the primary structure. The Vierendeel truss could be a structure wherever the members don't seem to be triangulated however type rectangular openings and is a frame with fixed joints that are capable of transferring and resisting bending moments. As such, it doesn't match the strict definition of a truss (since it contains non-two-force members); regular trusses comprise members that are normally assumed to own fastened joints, with the implication that no moments exist at the jointed ends.

Vierendeel Bridge

This form of the structure was named when the Belgian engineer Arthur Vierendeel, UN agency developed the planning in 1896. Its use for bridges is rare because of higher prices compared to a triangulated truss.

Analysis of frames:

1. Perfect Truss
2. Imperfect Truss

A-frame could be a structure made from many bars/ rods welded/riveted along. The bars are angle irons/ channels of “i” or “t” sections. These are known as members on the appliance of load on to the structure, the members remain loaded with the tensile/compressive load. Members underneath tension are known as “tie”, Members underneath compression are known as “strut”. The structure formed by the members (tie/ strut) is called “truss”. Extensively used in roof, bridge, sheds etc.
The structure is meant of links which are just enough to keep a truss in equilibrium, While under load without any change in the shape

N = 2j – 3

where, ‘n’ is the number of members, and

‘j’ no of joints

It is efficient and optimized structure.

The structure is meant of links more or less than the minimum numbers necessary to maintain it in equilibrium when loaded

N ≠ 2j – 3

if N > 2j – 3 ----------------------- it is redundant Imperfect Truss


if N < 2j – 3 ---------------------it is Deficient imperfect Truss

 

Click on this link for MCQs Practice. It covers most of the conceptual questions linked with the problems of trusses and frames.