Beams are the backbone of structural engineering, carrying loads and transferring forces in buildings and bridges. Understanding different beam types and how they respond to various loads is crucial for designing safe, efficient structures.

From simple supports to complex continuous spans, each beam configuration has unique properties. Loads can be concentrated at points or distributed along the length, creating diverse stress patterns that engineers must analyze and account for in their designs.

Beam Types

Common Beam Configurations

• Simply supported beam spans between two supports with free rotation at both ends
  • Rests on two supports, typically at or near its ends
  • Allows for rotation at the supports, reducing moment transfer
  • Commonly used in residential construction for floor joists and roof rafters
• Cantilever beam fixed at one end and free at the other
  • Rigidly connected to a support at one end, with the other end unsupported
  • Transfers both moment and shear forces to the fixed support
  • Frequently employed in balconies, canopies, and aircraft wings
• Fixed-end beam restrained against rotation at both ends
  • Rigidly connected to supports at both ends, preventing rotation
  • Develops moment reactions at both supports
  • Often found in reinforced concrete structures and industrial buildings

Advanced Beam Configurations

• Overhanging beam extends beyond one or both supports
  • Combines characteristics of simply supported and cantilever beams
  • Portion extending beyond support behaves like a cantilever
  • Used in bridge construction and building eaves
• Continuous beam spans over multiple supports
  • Extends uninterrupted over three or more supports
  • Allows for more efficient distribution of loads
  • Commonly utilized in multi-story buildings and long-span bridges
  • Requires analysis of moment redistribution and support settlement

Loading Conditions

Concentrated Forces

• Point load applies force at a specific location on the beam
  • Represents a concentrated force acting on a small area
  • Can cause localized stress concentrations
  • Often modeled as acting at a single point for simplification
  • Includes weights of equipment, vehicle wheels on bridges
• Moment load applies a pure rotational force to the beam
  • Creates bending without direct vertical or horizontal forces
  • Can be caused by eccentric loads or structural connections
  • Represented by a curved arrow in beam diagrams
  • Examples include wind loads on tall structures, torque from machinery

Distributed Forces

• Distributed load spreads force over a length or area of the beam
  • Uniform distributed load applies constant force per unit length
    • Represented by a rectangular pressure diagram
    • Common in floor loads of buildings, snow loads on roofs
  • Non-uniform distributed load varies along the beam length
    • Can have linear, parabolic, or other variations
    • Represented by a non-rectangular pressure diagram
    • Occurs in fluid pressure on dams, soil pressure on retaining walls
  • Partially distributed load acts over a limited portion of the beam
    • Combines characteristics of point and distributed loads
    • Examples include crowd loads on bleachers, parking areas on bridges