The steel structure course in kerala should have adequate strength, stiffness and toughness for proper functioning.
- Preliminary member sizing of beams
- Structural analysis – modeling, analysis
- Design review – member modifications
- Cost of estimation
- Preparation of structural drawings and specifications
- Loads for structural analysis and design
- Dead load
- Live load
- Mean return period OR
- Recurrence interval OR
- Live loads for various occupencies
- Reduction in basic design live load
- Impact Load
- Wind load
1. Adaptations to site:
If it is a building, the design must be such that there are suitable arrangements for rooms, corridors, stairways, windows, elevators, emergency exits etc and all this plan should be adapted to site so that it is acceptable and at a reasonable cost. This is called functional planning.
2. Structural scheme:
structural scheme is dependent on functional planning. Structural scheme includes the location of columns in the buildings, it is to be carried out with the functional plan and sufficient space must be calculated between finished ceiling and finished floor for location of columns.
3. Structural analysis:
Once the design is laid out, structural analysis must be performed to determine internal forces that will be produced in the framework. Proper calculations must be made and it should be ensured that structure in reality also behaves as it is supposed to be
5. Factor of safety:
The following factors must be considered while developing of design to provide suitable values of the margin of safety and reliability.
- Variability of the material with respect to strength and other physical properties
- Uncertainty in the expected loads
- Precision with which internal forces are calculated
- Possibility of corrosion
- Extent of damage, loss of life
- Operational importance
- Quality of workmanship
The design safety of structures may be evaluated in either of the two ways:
- Allowable Stress Design
- Load and resistance factor design
A. Allowable stress design:
- Based on the elastic behaviour of the material.
- The stress is in allowable limits.
- The full strength of the material is not utilized but we use less value as the limited stress value.
- It is based on the elastic behaviour of the material
- The stress on structural members is kept within the allowable limits
- Full strength of the material is not utilized and a lesser value of the limited stress value is used.
- The compressive stress is divided by a factor of safety to obtain an allowable or working stress.
Disadvantages of Allowable stress design
- In ASD the internal stress is zero before any loads are applied .
- ASD does not give reasonable measure of strength. As strength is more fundamental measure of resistance than allowable stress. Safety is applied only to stress. Loads are considered to be uniform. To overcome the above limitations and drawbacks LRFD was evolved.
- During manufacturing of steel when it is cooled, the rate of cooling at the top is different than at the bottom or middle and so it causes differential cooling, thus, introducing induced stress internally.
- It does not give reasonable measure of strength. .
- Safety is applied only to stress level. Loads are considered to be uniform. If not, only option is the factor of safety.
B.Load and Resistance Factor Design(LRFD)
This is based on the principle that strength of various materials and the applied loads depend on certain factors, and thus the structural elements are designed using reduced strength and increased loads.The strength is reduced on the basis of the strength of the material. The load factor is more for the materials that cannot be easily predicted.