Notes

An industrial building is any structure that is used to store raw materials, house a manufacturing process, or store the furnished goods from a manufacturing process. Industrial buildings can range from the simplest warehouse type structure to highly sophisticated structures integrated with a manufacturing system. These buildings are low rise steel structures characterised by low height, lack of interior floor, walls, and partitions. The roofing system for such a building is a truss with roof covering. Design of basic elements of the structure (Roof deck, Purlins, Girders, Columns and Girts) is not difficult, but combining them into functional and cost effective system is a complex task.

In Industrial building structures, The walls can be formed of steel columns with cladding which may be of profiled or plain sheets, GI sheets, precast concrete, or masonry. The wall must be adequately strong to resist the lateral force due to wind or earthquake.

Definition:

A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th- and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.

COMPONENT OF AN INDUSTRIAL
BUILDING:-
The elements of industrial buildings are listed
below.
1) Purlins
2) Sag rods
3) Principal Rafters
4) Roof Truss
5) Gantry Girders
6) Bracket
7) Column and Column base
8) Girt Rods
9) Bracings

Design:
The nature of a truss allows the analysis of the structure using a few assumptions and the application of Newton's laws of motion according to the branch of physics known as statics. For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet. This assumption means that members of the truss (chords, verticals and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant bending loads upon the elements, as in a Vierendeel truss.
In the bridge illustrated in the infobox at the top, vertical members are in tension, lower horizontal members in tension, shear, and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension. The central vertical member stabilizes the upper compression member, preventing it from buckling. If the top member is sufficiently stiff then this vertical element may be eliminated. If the lower chord (a horizontal member of a truss) is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated, but with additional strength added to other members in compensation. The ability to distribute the forces in various ways has led to a large variety of truss bridge types. Some types may be more advantageous when wood is employed for compression elements while other types may be easier to erect in particular site conditions, or when the balance between labor, machinery and material costs have certain favorable proportions.
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 the design decisions beyond mere matters of economics. Modern materials such as prestressed concrete and fabrication methods, such as automated welding, and the changing price of steel relative to that of labor have significantly influenced the design of modern bridges.

Brief historical evolution and development of trusses

The modern roof truss—the metal plate connected engineered wood truss—was invented and patented in the then-small town of Pompano Beach, Florida in 1952.

A. Carroll Sanford, founder of Sanford Industries, was familiar with truss design and spent a good bit of time experimenting with a variety of different materials in an attempt to build a better truss, until he landed on his final design that changed the construction world forever.

Since 1952, truss manufacturing processes have evolved significantly, as have design capability and materials used in truss manufacture. At face value, 1952 doesn’t seem that long ago. Thanks to A. Carroll Sanford’s design, over the short course of just over 6 decades, wood building construction has been made much more efficient. Clearly, however, wood buildings have been in production for a long time

Purlins
Purlins are beams which are provided over trusses to support roof coverings. Purlins spans between top chord of two adjacent roof trusses. When purlin supports the sheeting and rests on rafter then the purlins are placed over panel point of trusses. Purlins can be designed as simple, continuous, or cantilever beams. Purlins are often designed for normal component of forces. the various sections of purlins are as follows.

Sag Rod
These are round sections rods and are fastened to the web or purlin. The roof covering in industrialbuildings are not rigid and do not provide proper support. Therefore, sag rods provided between adjacent purlins to extend lateral support for purlins in their weaker direction. A sag rod is designed as a tension member to resist the tangential component of the resultant of the roof load and purlin dead load. The tangential component of the roof load is considered to be acting on the top flange of purlins, whereas the normal component and purlin dead load is assumed to act at its centroid. Therefore the sag rod should be placed at a point where the resultant of these forces act

Principal rafter
The top chord member of a roof truss is called as principal rafter. They mainly carry compression but they may be subjected to bending if purlins are not provided at panel points.



Roof Trusses
Roof trusses are elements of the structure. The members are subjected to direct stresses. Truss members are subjected to direct tension and direct compression.



Gantry Girder
Gantry girders are designed as laterally unsupported beams. Overhead travelling cranes are used in industrial buildings to lift and transport heavy jobs, machines, and so on, from one place to another. They may be manually operated or electrically operated overhead travelling crane. A crane consists of a bridge made up of two truss girders which moves in the longitudinal direction. To facilitate movement, wheels are attached to the ends of crane girders. These wheels move over rails placed centrally over the girders which are called gantry girders.

Brackets
Brackets types of connections are made whenever two members to be secured together do not intersect.

Column and Column Base
A column is a structural member which is straight to two equal and opposite compressive forces applied at the ends. Stability plays an important role in the design of compression member because in columns buckling is involved. The problem of determining the column load distribution in an industrial building column is statically indeterminate. To simplify the analysis the column is isolated from the space frame and is analyzed as a column subjected to axial load and bending.

An industrial building column is subjected to
following loads in addition to its self weight.
1) Dead load from truss
2) Live load on roof truss
3) Crane load
4) Load due to wind
Steel columns are normally supported over concrete blocks. However when the load supported by these columns are large and the bearing pressure of concrete from below is insufficient to resist the loads, they may fail. Therefore it is a normal practice to distribute column loads to steel base plate which are placed over these concrete blocks. In addition to transferring safely the column loads, a base plate also maintains the alignment of the column in plane, verticality of the column and controls column and frame deflection.