Spandrel Beam | Properties, Uses, design, Advantages & Disadvantages of Spandrel Beam

Spandrel beams are those beams that are constructed along the external wall of each floor of the house. It is mainly a horizontal frame, prepared of steel or concrete, constructed along the exterior of the building to support loads of walls or definite loads of roofs over it.

Spandrel beams are usually known as edge beams. These beams are added in such cases where the wall being constructed does not support the weight of the slab or the floor.

  1. Properties of Spandrel Beam  

a. The beams fixed to a flanged floor beam in place of a rectangular floor beam make an increased ability to hold torsional tension.

b. The torsional action of the spandrel beams is necessary since the load of the slab is transported from the beams to the column.

  2. Uses of Spandrel Beam  

a. Spandrel beams are generally utilized in multi-story buildings at each floor level.

b. These are fixed to the outer perimeter of floor slabs as a belt to hold the floor beams.

c. It also strengthens the connection between the slab and outer columns. On the roofs, the parapets are placed upon these beams.

  3. Design of Spandrel Beams  

Any of the basic specification specifications are as follows:

1. Internal torsion and shearing.

2. End of beam torsion.

3. The link to the internet.

4. Transfer of the Load.

5. Web flexion arises from the torsion balance.

6. Ledge serves as a corbel at the end of the beam reaction.

7. Flexure of the beam.

1. Internal Torsion and Shear

As given vertical and horizontal loads do not displace through the middle torsion of the beam. At each cross-section, the formation of the torsion to the beam is the addition of the torques (the shear force times the distance from the shear center) lying at that cross-section.

It is sure that the loads given to the beam differ from the point of erection to when all time-dependent volume adoptions are performed. Each loading case requires to be noted to figure out who commands the design.

If the given torsion and shear are produced, the internal torsion and shear reinforcement can be known on the basis of ACT 3183 criteria for strengthened members or on the basis of other relationships 9′ for pre-stressed members.

If only vertical loads are summed to the spandrel, the shear basics can be taken to be very conservatively aligned with the vertical centerline of the web beam.

2. Beam End Torsion

The beam edge torsion is known as the torsion at the end of the beam within the distance “d” or “d/2” leading from the torsion at the end of the beam.

Generally, the beam torsion prepared by the top and bottom connections is explained by a single crack, inclined at about 45 deg, with a nominal width of 0.015 in. (0,38 mm) or more.

3. Ledge Attachment

The attachment of the spandrel beam ledge to a web can be either even by the strength of plain concrete or even by the reinforcement of steel, depending on the size of the beam, the strength of the concrete, and the scale of the ledge load.

The ledge to the horizontal cable connection is known to be analogous to the motion of two hard bodies where the separation will take place over the whole length of the web of the beam on the connection surface.

4. Ledge Load Transfer

The spandrel beam transmits uniform as well as concentrated loads to either the web through shear and flexure. The engineering techniques given for the movement of lead loads are depending on the PCI Concept Handbook with some guidelines Variations. The load shift of the ledge would complete the concrete punching shear if the new shear reinforcement is not to be utilized.

5. Web Flexure Resulting from Torsion Equilibrium

Two conditions of web flexure can develop if the total torsion balance of the spandrel beam is made by,

The web beam runs against the top of the members it provides and the bottom attaches at the end of the vertical spandrel.

Similar loading conditions may increase when horizontal loads are applied to the web of the beam, except that the forces are in a direction opposite to those increasing from the vertical load torsion balance.

6. Ledge acting as a Corbel at Beam End Reaction

When the end support reaction of the spandrel beam is compatible with the applied ledge loads, the ledge functions as the upside-down corbel The upside-down corbel may be designed to support the final reaction by following the procedures of the PCI Construction Handbook for corbels with some changes.

7. Beam Flexure

General spandrel beam flexure requires two distinct loading conditions-one at the service level and the other at the final point.

Depending on the cross-section dimensions of the beam and whether or not the spandrel utilizes support bars or pre-stressing strands, the methods of analysis may be exactly similar or completely different.

If the relations between both the spandrel beam and the structural units given by the spandrel do not neglect torsional rotation, it will be exact to take the effect of the main inertia axes on the service loads.

Spandrel beams may not have symmetry on either axis. If the depth of the beam is shallow, the direction of the main axis can be important when assessing the elastic tension at the service stage, either for reinforcement bars or for pre-stressed reinforcement.

  4. Advantages of Spandrel Beam  

1. The exterior walls of the multi-story structure are held by spandrel beams.

2. For buildings with large beam-column links, the utilization of a spandrel beam is recommended to extend seismic efficiency. These utilize spandrel beams that contain both longitudinal and transverse reinforcement.

3. It improves the sideways stability of steel and concrete.

4. It is utilized along with coupled shear walls to advance stiffness and ductility against earthquakes.

5. Spandrel beams add protection for exterior side openings such as windows, shear walls, and lintels.

6. Spandrel beams have extra support on the outside walls of a multi-story structure.

7. Spandrel beams for both longitudinal and transverse reinforcement, which extend the seismic ability of the structure, are best for large beam-column ties.

  5. Disadvantages of Spandrel Beams  

a. It is mounted on the exterior of a structure, they are majorly riskier to moisture than floor beams leading to the collapse or corrosion of reinforcing steels.

b. As a result of cracking and chewing asphalt, considerable effort and money are spent on the reconstruction of the structure.