Pre Engineered Buildings:
Pre Engineered Buildings (PEB) are the buildings which are engineered at a factory and assembled at site. Usually PEBs are steel structures. Built-up sections are fabricated at the factory to exact size, transported to site and assembled at site with bolted connections. This type of Structural Concept is generally used to build Industrial Buildings, Metro Stations, Warehouses etc.
The adoptability of PEB in the place of Conventional Steel Building design concept resulted in many advantages, including economy & easier fabrication. These type of building structure can be finished internally to serve any functions that is actually help in low rise building design. Examples of Pre-Engineered Buildings are warehouses, Canopies, Factories, Bridges etc.
Components of PEB:
Pre Engineered Buildings consist different steel structural member which are as follows,
- Primary Frame: Primary framing of a PEB is an assembly of builtup I-Shaped steel members & that framing consist trusses or castellated beams etc.
- Secondary Structural Elements: It is actually Cold Formed Members, which can be in diff. shapes like “Z”, “C” etc. In general known as “Purlins”.
- Roof & Wall Panels : Tin shades & Curtain Wall made of Glass & Roll-formed steel sheets usually comes in this category , S
- Sandwich Panels: Sandwich Panel is made of three layers , in which a non-Aluminum Core is inserted b/w two aluminum sheet.
- Other Accessories: Mezzanine floors, Bolts, Insulation, etc.
Advantages of PEB:
There are many advantages of Pre Engineered Buildings, which are as follows,
- Quality control is the main advantage as all the structural member are engineered beforehand, standards of different codes also taken into consideration & these components are made in factory under the supervision of Quality Control Engineer.
- Lower cost due to the saving in design, manufacturing and on site erection cost.
- Minimizing time of construction due to the use of software for design of the structural components.
- Low Maintenance due to use of standard quality of paints over steel members , which increases the ability to withstand & finally the maintenance cost will be low as compare to conventional steel building.
- Quick Erection, as all the members are Pre Manufactured & skilled labor is used for connections of different components.
- Warranty on PEB, mostly warranty period of 20 years given by manufactures for PEB.
Disadvantages of PEB:
Although PEB have many advantages in the field of Industrial structure but still there are some demerits of Pre Engineered Buildings, which are as follows,
- Rusting / Corrosion Sensitive, as if the quality of steel used or paint used for coating of steel members is not of good quality , than it can damage the structure and thus reduces the life of structure.
- Insulation Cost, as insulating the building to an agreeable benchmark will furthermore add to your construction costs.
- Appearance, Steel Sections can be unattractive when left exposed.
- Method Used : Stiffness Matrix Method
- Standard Code used :
- IS : 800
- Software used : Staad.Pro v8i, ETABS, RAM Steel
- Load Considerations & their Calculations : Loads considered in the PEB design are same as for general building structure. These are as follows ,
- Dead load Calculations : It includes Self Wt. of Purlins , Roof & Wall Sheeting , insulation material & other structural component.
- Live / Imposed Load Calculations : It should be Considered as per given in IS 875 (Part 2 ) for diff. type of
- Wind Load Calculations : Consider the Basic wind Speed as per Area of that particular structure. Design wind Pressure is calculated as per IS 875 (Part 3) . Wind Load on Roof can be UDL & calculation for this can be done as per IS875(Part 3)
- Seismic Load Calculations : Earthquake Loads affect the design of structure in areas of great seismic activity. The seismic load can be calculated as per IS 1893-2002(Part 1).
- Other Moving Loads : It can be Moving EOT Crane load or Mono Rail etc.
- Load Combinations : As per IS 1893 – 2002 (Part 1)
- 7(DL ± LL)
- 7(DL ± EL)
- 3(DL + LL ± EL)
- Mechanism : For diff. Load Combinations structure should be checked by considering Internal work equal to External work and We will consider the following Mechanism,
- Beam Mechanism
- Sway Mechanism
- Gable Mechanism
- Combined Mechanism
- Checks Made :
- Effect of Axial Force : Max. Load should be checked with allowable load bearing of the section. As, Max. Axial Force in Column/Axial Load causing yielding < 0.15
- Check should also be made for Local Buckling of Flanges & Webs.
- Check for the Effect of Shear Force : Shear Force at the end of the Girder should be less than the Max. Shear Capacity.
- Design Procedure : It consist some steps, which are as follows,
- Based on the geometry, set up section sizes and brace locations.
- Loading Calculations : Specify the Load case & load combinations for designing of the framed steel structure.
- Calculate S.F. & M. for each load case detail
- By using the Standard Codes, check and compare the calculated stress with the allowable or Permissible Shear Stress & Bending Stress values.
- Design the optimum Splice Location.
- Made check for predicted section that it satisfy or fail for any loading conditions.
- Now, by ending the design an analysis is run to achieve flange bar optimization.
Video below shows step by step assembly of a Pre engineered structure.