# What is Beam? Classification, Reinforcement, and Development Length

Beams are essential structural elements in the construction industry that are designed to support and distribute the load to provide stability and strength to the structure. According to their characteristics, they are divided into different types. In this article, we will discuss everything about beam classification, reinforcement processes, load calculations, developing lengths, and much more.

**Contents**show

**What is a beam?**

A structural member subjected to external forces or couples at right angles to the longitudinal axis is called a beam.

**How to Classify the Types of beam? **

Different types of the beam are classified into various groups due to their strength, durability, properties, requirements, and uses.

**Based on structural: **

Types of beam | Description |

Simply supported beam | Beams that have supports at both ends |

Cantilever beam | Beam that is fixed at the end and free at the other end |

Overhanging beam | Types of beam in which the endpoint is extended beyond the support |

Fixed Beam | Abeam whose both ends are fixed |

Continuous beam | beam that is provided by more than two supports |

Propped cantilever beam | Beam in which one end is free and free end is supported by a roller support |

**Based on Loading:**

Concentrated Load | Beam in which force applied at a single point |

Uniformly Distributed load | uniform distribution of load along the beam’s length. |

Uniformly varying load | Load that varies uniformly along beam length. |

**Based on Cross-Sectional Shape:**

Rectangular Beam | Straight beam with rectangular cross-section |

I-Beam | Beam with I cross-section and use due to high strength. |

T-beam | Beam with T cross-section and used in construction for floors & and roof systems. |

Double-T Beam | As similar to I-beam but it has an additional horizontal flange |

L-beam | Beam with L cross-section and provided around the perimeter of the structure. |

Circular Beam | Beam has a circular shape and is used in columns and certain structural applications. |

Hollow circular beam | Circular cross-section with a hollow core |

H beam | |

C-beam | Beam with C cross-section and used for various applications |

Laminated Beam: | built by assembling layers of various materials or strengths. |

**Based on equilibrium conditions:**

Statically determinate beam | It allows us to determine the support reactions and internal forces by using equilibrium. |

Statically indeterminate beam | It does not allow us to determine the more unknown forces by using equilibrium conditions that require the compatibility equations or matrix analysis for a complete analysis |

**based on materials:**

Wooden beam | Used for residential and smaller-scale structures in construction |

Steel beam | Used due to their strength and durability |

Concrete beam | Widely used in various construction projects |

Composite beam | Made with a combination of multiple materials like steel, and concrete to optimal structural properties |

Aluminum Beams | Suitable for certain construction applications use light weight and corrosion resistance. |

**Based on geometry:**

Straight beam | Beam has no cross section that linear structural element. |

Curved Beam | Beams have two support points for stability. |

Tapered beam | Varying lengthwise in a gradual manner to deal with different loads. |

**Dynamic Classification:**

Free Vibration | Natural oscillation of a system without external forces |

Forced Vibration | Oscillation induced by external forces or excitations |

**Based on the construction method:**

Cast-in-Place Beams | Beam construct on site. First place formwork then pour the concrete. |

Precast Beams | Manufactured off-site and transported for assemble |

Prestressed Concrete Beams | Internal stresses are introduced before being utilized to improve the durability. |

**Based on Number of Spans:**

Singly beam | Supported on its end point without any intermediate support |

Multi-span beam | Supported on more than two points that create multiple spans with support between ends |

**Based on Use:**

Girder beam | Mostly used to carry heavy loads like bridges |

Lintel beam | Used to support the masonry over the doors, windows, and other openings |

Sill beam | Similar to lintel beams but located at the bottom of window or door openings. |

Plinth beam | |

Grade beam | Beams are constructed at ground level or grade level to connect the column foundations. |

**What is Beam reinforcement detail?**

The term “beam reinforcement details” describes the specific characteristics and detail of steel bars (reinforcement) inside a concrete beam, such as the size, spacing, and layout of the bars that ensure structural performance and strength.

**Based on embedded reinforcement:**

**Singly reinforced:**

- Due to bending and shear reinforcement resists tensile stresses in the beam.
- On the compression face of the beam, two bars are additionally provided with a nominal diameter of 8mm or 10mm.

**Doubly reinforced:**

- When beam depth is limited the doubly reinforced utilized.
- On the compression side, more reinforcement is provided.
- Also, provide extra bars to handle the bending and shear from torsion.

**Reinforcement detail: **

**Bottom formwork of beam:** Place the formwork on the vertical column to contain the beam structure.

**Clear cover: **Place the clear cover on the formwork to stabilize the distance between the bars.

**Bottom main bars:** Place the main bars to ensure the structure’s strength.

**Top Main Bars: **At the top place the main bars to enhance the strength.

**Stirrups:** Put the stirrups in reinforced to provide lateral support and resist shear forces.

**Bottom Spaces bars:** Steel reinforced bars placed at the bottom side with required gaps for flexibility.

**Bottom additional bars: **Extra two bars are added at the bottom for increased strength.

**Top spaces bar: **Steel reinforcement at the top is added with designated gaps for flexibility.

**Top additional bars:** Extra steel bars are added at the top of the side with a required gap for flexibility.

**Stirrups:** Place the stirrups to hold the bars tightly.

**Formworks: **Place the formwork around the bars to shape and contain the slab.

**Pour concrete: **Pour the concrete into the formwork.

**What is the beam load calculation?**

You can calculate the load of the beam by using the formula and by using the online calculator. However, the beam load calculation depends on determining the internal forces and stresses that apply load on the beam and its dimensions, material properties, and support conditions.

**Find Self-weight beam load calculation:**

**As we know,**

**Concrete self-weight**=2400 kg/m3**Steel self-weight**=7850 kg/m3

**We assume:**

- Beam dimension with slab thickness: 230mm x 450 mm
- Width=230
- Height=450
- Beam length=1m

**Solution:**

**The volume of concrete**= l×b×h

=1m×0.23m × 0.45m

=0.124m3

**Weight of concrete**=V×Density_{concrete}

=0.124×2400

=297.6kg

**Weight of steel (2%) in concrete**=V×Percentage_{steel}×Density_{steel}

=0.124 x 0.02 x x7850

=19.46kg

**Total weight of beam**=W_{concrete}+W_{steel}

=297.6+19.46

=317.06kg/m

**Conversion to Kn/m**=W_{total}/9.81=317.06_{kg/m}/9.81_{m/s}^{2}≈32.29kN/m

So, the self-weight will be around 32.29kN/m per running meter.

**What is the **development length of the **beam?**

Development length in beam and column is provided to transfer the load from one building component to another. The length of the steel bar needed to be embedded into the column when designing the beam to establish the desired bond strength between concrete and steel.

**Developing length of beam:**

In beams, the development length is the minimum amount of reinforcing bars that must be set into the concrete. So, the forces effectively transfer between the surrounding concrete and the steel reinforcement.

**Development length formula for beam:**

You can use development length in beam formula to calculate the required result in mm for any given dia of bars.

L_{d} = (Φ × σ_{s})/(4 × τ_{bd}),

**Where,**

- L
_{d}= development length - Φ=diameter of the bar
- σ
_{s}=stress in bars at design load - Τ
_{bd}= design bond stress

**Design Bond Stress in Limit state Method**

Design Bond Stress in Limit state Method | ||||||

– | M20 | M25 | M30 | M35 | M40 and above | _ |

Concrete Grade | 1.2 | 1.4 | 1.5 | 1.7 | 1.9 | For plain bars in tension |

Design Bond Stress(τ_{bd}, N/mm^{2}) | 1.92 | 2.24 | 2.4 | 2.72 | 3.04 | For deformed bars in tension |

**Designed Bond stress in Working Stress Method**

Designed Bond stress in Working Stress Method | ||||||||

– | M20 | M25 | M30 | M35 | M40 | M45 | M50 | – |

Concrete Grade | 0.8 | 0.9 | 1 | 1.1 | 1.2 | 1.3 | 1.4 | For plain bars in tension |

Design Bond stress (N/mm^{2}) | 1.28 | 1.44 | 1.6 | 1.76 | 1.92 | 2.08 | 2.24 | For deformed bars in tension |

**What is the clear cover of beam?**

Basically, beam cover in beam is the minimum distance between the bottom of the beam(i.e the summit of the beam) and the outer surface of the reinforcement (i.e. the layer where it is provided). Nominal concrete cover is also called as clear cover for beam as per is 456.

**Clear Cover for beam according to IS 456:**

Factor | Beam cover size |

Recommended range | 25mm to 40mm |

Optimal for dry weather | 25mm |

Optimal for wet/moist weather | 35mm to 40mm |

**What is the Lap length for Beam?**

In structural engineering, the term “lap length” refers to the required overlap of reinforcing bars in a concrete component in order to provide appropriate stress transfer and maintain structural integrity.

**Formula for lapping length in beam:**

**Lap length**= Development Length Coefficient × Diameter of Reinforcing Bar

=L×d

**Lap length in beam As per IS code 456-2000:**

**Tension Zone:**

**Flexural tension:**Ld or 30d (whichever is greater).**For different diameter bars:**2Ld or 30d (whichever is greater)**Minimum straight length of lapping:**15d or 20mm

**Compression Zone:**

The lapping length for beam should not be less than 24d, but it is equivalent to the development length calculated in compression.

**Key Points:**

- Avoid lapping (24d) in top bars within L/3 distance from both ends.
- Bottom bar lapping (45d) near column or L/4 distance but not at mid-span.
- At the lap zone, the stirrups should be positioned narrowly.
- It is best to organize bar dipping in an alternating method.

**Note:** Specifications and rules for structural engineering design determine the lap length of reinforcing bars in concrete beams. This can vary depending on a number of requirements, including the kind of structure, the strength of the concrete, and the diameter of the reinforcing bars applied.

**What are tension and compression in beam?**

Compression and tension are the two basic force types used in the construction of any structure. Every material has the ability to hold up to a certain amount of tension and contain the amount of compression.

**Tension stress:**A tension force on the bottom side due to the weight on the top so that it pulls materials apart.**Compression stress:**A compression force caused due to the weight on the top of the beam that squeezes material together.

**Frequently Asked questions: **

**What is a pillar beam?**

In the construction industry, the pillar is an integration of vertical structural elements like columns, posts, or piers with horizontal beams. Forming a structural element for load bearing and architectural support.

**What is effective depth and effective cover of beam?**

The **effective depth** of the beam and slab is the distance between the extreme compressive concrete fiber to the centroid of tension reinforcement in the section under flexural conditions.

The **effective cover** of beam is the distance between the exposed concrete surface and the main reinforcement centroid.

Reinforced concrete beam type of hidden beam, whose depth is equal to the thickness of the slab. Hidden beam is also referred to as a concealed beam.

**What is a foundation beam?**

A horizontal structural feature is called a foundation beam. which is frequently reinforced and improves stability and load-bearing capacity by distributing loads throughout the foundation of a building while providing additional support.

**Wrapping Up: **

In conclusion, each of the beam kinds suits particular structural requirements. Designing reliable and efficient structures requires a knowledge of their classifications, reinforcement specifications, and load calculations. Being up to date on the most recent developments in the field of structural engineering is essential for designing and building beams with maximum efficiency.