ANALYSIS & DESIGN OF RC BEAM AS PER ACI 318-08

The Basic Concept: When a concrete beam bends under load, the concrete on one side gets compressed while the other side gets stretched (tension). Since concrete is very weak in tension, steel reinforcement bars (rebar) are placed in the tension zone to carry those forces. The calculation ensures the beam has enough steel reinforcement to safely carry the applied bending moments without failing.

The Design Philosophy: The calculation follows the "ultimate strength design" approach, which means:

• Design the beam to handle the maximum expected loads multiplied by safety factors
• Ensure the steel reinforcement yields (stretches) before the concrete crushes, creating a "ductile" failure that gives warning before collapse
• Balance the amount of reinforcement - too little and the beam fails suddenly, too much and it becomes inefficient

Key Checks Being Performed:

1. Flexural capacity - Does the beam have enough steel to resist the bending moments?
2. Shear capacity - Can the beam resist the cutting forces without diagonal cracking?
3. Crack control - Will cracks in the concrete be acceptably small under normal use?

The calculation considers different locations along the beam (supports vs. midspan) because the internal forces vary along the length, requiring different amounts of reinforcement at different locations.

This follows ACI 318 code requirements, which provide standardized rules for safe concrete design based on decades of research and testing.