Definition of Design: Planning or creating drawings for a structure not yet constructed.
Understanding Reinforced Concrete
Reinforced Concrete: Concrete made stronger by adding steel bars (reinforcements).
Composition of Concrete
Components: Cement, fine aggregates, coarse aggregates, and water.
Water-Cement Ratio: Crucial for determining concrete strength; too much or too little affects the quality.
Key Concepts in Concrete Design
Mix Ratios: Common ratios include 1:2:4 (cement:sand:coarse aggregates) and designations like M15 (15 N/mm² strength after 28 days).
Curing: Essential for achieving strength; involves keeping concrete moist to prevent cracking.
Structural Components
Elements of Design: Slabs, beams, columns, and footings.
Slab: Horizontal surface supported by beams and columns.
Beam: Horizontal member that supports loads from slabs.
Column: Vertical structural member that transfers loads to the foundation.
Footing: Base of a column that distributes its load to the ground.
Design Considerations
Bearing Capacity: Determined by geotechnical engineers; informs footing size.
Reinforcement Details: Include bar dimensions, spacing, and cover to protect steel from corrosion (15mm clear cover for slabs, 25mm for beams).
Effective vs Clear Cover: Effective cover includes half the diameter of the bar beyond the clear cover.
Importance of Detailing
Bar Specifications: Length, diameter (e.g., 6mm to 25mm), and types of bars used in different structural elements.
Lapping and Ties: Necessary for continuity of bars and preventing bulging; ties secure longitudinal bars in columns.
Construction Practices
Clear Cover Blocks: Used to maintain proper concrete cover.
Curing Methods: Often involves covering with jute bags and keeping them moist.
Testing and Quality Assurance
Cube Testing: 150mm cubes of concrete are cast to test strength after curing.
Universal Testing Machine: Used for compression tests on concrete and tension tests on steel.
Testing Standards: Follow specific codes (Indian Standard IS 456:2000) for material properties and design methods.
Load Considerations
Dead Load: Self-weight of the structure, often 50% of total load.
Live Load: Variable loads from occupancy; standards suggest calculating based on expected use.
Wind Load: Account for wind conditions based on location.
Seismic Load: Use IS 1893 for earthquake-resistant design considerations.
Design Guidelines and Codes
Importance of Codes: Follow established codes for safety and standardization.
Key Codes: IS 875 for design loads, IS 456 for reinforced concrete, and IS 1893 for seismic considerations.
Recommended Books
"Properties of Concrete" by Neville.
"Design of Reinforced Concrete" by BC Punmia.
Various other materials available in the department.
Conclusion
Reinforced concrete design involves a comprehensive understanding of materials, structural elements, and adherence to coding standards to ensure safety and effectiveness.