Building

Beam structures

Introduction

The primary function of a beam in structures and building construction is to resist load. A beam is a structural member used for bearing loads. It is typically used for resisting vertical loads, shear forces and bending moments in which the load applied to it result in reaction forces at the beam’s support points and its more of deflection is primarily by bending.

A beam is a structural element that primarily resists loads applied laterally to the beam’s axis. The total effect of all the forces acting on the beam is to produce shear forces and bending moments within the beam, that in turn induce internal stresses, strains and deflections of the beam. Wikipedia.

Types of Beam in construction

Different types of beams are used in construction of building and structures and they will be discussed based on their manner of support, shape of cross-section, length, and their material.

1. Simply Supported Beam: This is one of the simplest structural element that both ends are rest on supports but are free to rotate.

2. Fixed Beam: This is supported at both ends and fixed to resist rotation. It is also called a built-in beam.

3. Cantilever Beam: This is a beam that is fixed at one end and set to be free at the end. The beam distribute the load back to the support where it is forced against with a moment and shear stress. It is use the creation of a bay window, balconies, and some bridges.

4. Continuous Beam: This is a beam that has more than two supports distributed along its entire length.

5. Reinforced Concrete Beam: This is a beam constructed from concrete and reinforcement

6. Steel Beam: This beam is constructed from steels and used in several applications.

7. Timber beam: This type of beam is constructed from timber and used in the past.

8. Composite Beams: These are constructed from two or more different types of materials such as steel and concrete.

9. Rectangular beam: This type of beam is widely used in the construction of reinforced concrete buildings and other structures.

10. T-section beam: This type of beam is mostly constructed monolithically with reinforced concrete slab. Sometimes, Isolated T-beam are constructed to increase the compression strength of concrete.

11. L-section Beam: This type of beam is constructed monolithically with reinforced concrete slab at the perimeter of the structure.

12. Straight beam: This is a type of beam with straight profile and majority of beams in structures are straight beams.

13. Curved beam: This is a beam with curved profile, such as in the case of circular buildings.

14. Tapered Beam: This is a type of beam with tapered cross section.

15. Statically determinate beam: in this type of beam equilibrium conditions alone can be used to solve reactions, that is, the number of unknown reactions are equal to the the number of equations.

16. Statically indeterminate beam: In this type of beam, equilibrium conditions are not enough to solve reactions. So, the analysis of this type of beam is more complicated than that of statically determinate beams.

17. Cast In-situ Concrete Beam: This type of beam is constructed on project site. so, forms are initially fixed then fresh concrete is poured and allowed to be hardened. Then, loads will be imposed.

18. Precast Concrete Beam: This type of beam is manufactured in factories. So, the construction condition is more controllable compare with on-site construction. Consequently, the quality of concrete of the beam will be greater.

19. Prestressed Concrete Beam: This type of beam constructed by stressing strands prior to applying loads on the beam. Pre-tensioned Concrete beam and post-tensioned Concrete Beam are variations of pre-stressed concrete beam.

20. Deep Beam: This is a beams that have large depths, and its clear span to depth ratio is less than 4 according to ACI Code. Significant amount of the load is carried to the supports by a compression force combining the load and the reaction. Consequently, the strain distribution is no longer considered linear as in the case of conventional beams.

Also check: Column in building construction

Classification of beam in construction

Beams are classified based on the following condition:

  1. Based on Support Conditions
  2. Based on Construction Materials
  3. Based on Cross-Section Shapes
  4. Based on Geometry
  5. Based on Equilibrium Condition
  6. Based on Method of Construction
  • Simply Supported beam, fixed beam, cantilever beam
    and continuous beam are classified based on the support conditions.
  • Reinforced concrete beam, steel beam, timber beam and composite beam are classified based on the construction materials.
  • Rectangular beam, T-section beam and L-section beam are classified based on the cross-section shape.
  • Straight beam, curved beam, tapered beam are classified based on the geometry.
  • Statically determinate beam and Statically indeterminate beam are classified based on the equillibrum condition. While the
  • Cast In-situ Concrete beam, Precast Concrete beam and Prestressed Concrete beam are classified based on the method of construction.

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