Spandrel Beams - Functions, Features and Construction

Spandrel beams are beams constructed along the exterior wall of each floor level of the building as shown in Figure-1 below. It is a horizontal structure made of steel or concrete, constructed along the perimeter of the building to take the wall loads or some roof loads coming over it. Spandrel beams are also called as edge beams. These are provided in situations, when the wall constructed do not take the weight of the slab or the floor.

A before and after photo of the repair performed at a steel spandrel beam. The moment splice plate behind the screw jacks is needed for the new steel member installation. Photos courtesy RMF Engineering

Load Distribution By Spandrel Beams

The spandrel beams fundamentally transfer the external wall and the slab loads to the exterior columns. These beams are subjected to axial compression, torsion, bending moment and shear stresses as a part of interaction with the floor beams. The slab load is transferred to beam and then to the columns by torsion. All together the load distribution of spandrel beam system is a complex process.

Figure-1: Spandrel Beams

Features of Spandrel Beam

Some of the important features regarding spandrel beams are:
  1. A wall structure may or may not be there under a spandrel beam. There can be a column or a window under a spandrel beam. (Figure-2)
  2. Spandrel beam are provided along the exterior wall of the building. (Figure-1)
  3. Spandrel beams can be provided between the sill of a window and the head of the window placed below as shown in Figure-2.
  4. The spandrel beams can extend from one column to another column horizontally in steel or R.C.C structures. These structures can also support the wall.
  5. In roof structures, the parapets are constructed over the roofs.
Figure-2: Spandrel Beams for Windows

The construction of beam as flanged floor beam like T- Beams and L- Beams are more resistant to torsional stresses compared to rectangular floor beams. Hence, spandrel beams or edge beams are constructed as flanged floor beams, which help to increase the ultimate load capacity of the high-rise building.

Figure.2. Spandrel Beams

In spandrel beam arrangement, the load from slab is transferred to columns through the beams by means of torsion. Hence, the beam demands additional reinforcement to prevent torsional failure. 
ACI Committee 318 provides the specifications and recommendation to design spandrel beam in "Building Code Requirements for Structural Concrete and Commentary (ACI 318-19).
In flat slab constructions, spandrel beams are used to strengthen the connections between the slabs and the edge columns.

Advantages and Disadvantages of Spandrel Beam

The benefits of providing spandrel beams are:
  1. The outer edges of the multi-story building is strengthened using spandrel beams.
  2. For buildings with wide beam -column connections, the use of spandrel beam is recommended to enhance seismic performance. Such uses of spandrel beam demand both longitudinal and transverse reinforcement.
  3. Spandrel beams increases the lateral stiffness of steel and concrete.
  4. Spandrel beam are used along with coupled shear walls to increase stiffness and ductility against earthquake activities.
  5. Spandrel beams provide support for external side openings like windows , along with shear walls and lintels.
The drawbacks of spandrel beams are:
  1. Spandrel beams are located at the exterior edges of the building which is more prone to atmospheric moisture. This results in deterioration of concrete due to corrosion.
  2. Spandrel beams due to weathering actions are subjected to cracking and spalling of concrete.

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