Structural Design Basics

Structural design to commence, we require certain data. These data includes information about type of structure, site conditions, loading conditions, type of environmental exposure, earthquake zone and wind zone.

Site Conditions:

Structural design of foundation requires soil geotechnical (soil) investigation data i.e. safe bearing capacity of soil, depth of water level below the ground.

Loads on the structures:

Dead Loads:

Dead Loads are loads from the self weight of the structural members such as beams, columns, slabs, wall, finishing, plastering etc. Any stationary elements or equipment’s which may be permanently positioned on the structure shall also be considered as dead load. Unit of different materials are provided by the standard codes.

Live Loads:

Live loads also called as imposed loads are probable loads that the structure may be subjected to during occupancy. These are loads which are moving or dynamic in nature and may or may not be present on the structure during intended use of the structure. For example, for an industrial structure, loads from people, maintenance tools etc. can be called as live loads, while loads from equipment’s which are stationary at a location is considered as the dead load.

Wind Loads:

Wind loads are horizontal loads on the building which are exerted on the surface area of the building on windward side. This load is calculated based on the wind zone which provides the maximum wind speed in the given zone. This can be obtained from the wind map of the location. This wind speed is converted into force based on the surface area and orientation of building w.r.t. wind direction. Shape of the building is or structural member is also considered for calculation.

Seismic / Earthquake loads:

Design for seismic loads shall be carried out as per ASCE 7/ UBC/ IS 1893 or whichever standard code is applicable. The guidelines provided by these applicable codes shall be followed for calculation of earthquake forces.

Design of Structures:

Structural design of buildings or other structures should be carried out as per the relevant code of practice.

Structural concrete Design shall conform to ACI 318-95 / IS 456:2000 / BS 8110 : Part 1 : 1985 or other whichever code is applicable.

Structural steel design and fabrication shall conform to AISC-ASD (9th Edition) / IS 800:1984 / BS 5950 : Part 1 :1990.

Structural design methods are selected based on the local practices. Working stress method, Limit State Method, Load Resistance Factor Design method. These are the methods used for the design of structural members and are guided by the relevant standard code of practice.

Following factors to be considered for design of buildings or other structures and shall conform to the standard codes:

  1. Maximum allowable settlement of foundation / structure.
  2. Vertical and lateral deflections of buildings, structures as a whole and other structural members.
  3. Sliding and overturning of buildings or structures should be checked and prevented by design.
  4. Standard detailing guidelines should be followed in drawing.
  5. All engineering and design shall comply with relevant and applicable codes of practices, local bye-laws, and rules as per directorate of industries and factories & was listed in Project Design Basis.
  6. Environmental exposure conditions should be considered in design and respective factors must be applied in structural member design.
  7. Types of construction materials and structural members and their properties should be used during design.
  8. Special care should be taken to provide easy escape of occupants during emergency situations such as fire.

These are only few points, many other factors should also be considered which may be relevant for the design. A checklist for different types of structural design should be maintained and followed to prevent any error during design and detailing for buildings and other structures.

 

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