Spandrel Beam Definition-
Spandrel beams are beams built along the external wall of each floor of the house. It is a horizontal frame, made of steel or concrete, built along the exterior of the building to hold loads of walls or certain loads of roofs over it.
Spandrel beams are also called edge beams. These are provided in cases where the wall being built does not take the weight of the slab or the floor.
Properties of Spandrel Beam:
Spandrel beams are heavily dependent on the properties of the floor beams.
- Beams attached to a flanged floor beam instead of a rectangular floor beam create an increased ability to absorb torsional tension.
- The torsional action of the spandrel beams is important since the load of the slab is transferred from the beams to the column.
Features Regarding Spandrel Beams:
Both the arrangement may or may not be under the spandrel beam. There may be a column or a window under a spandrel beam.
- Spandrel beam is provided along the exterior wall of the house.
- Spandrel beams may be mounted between the sill of the window and the head of the window.
- Spandrel beams may be stretched horizontally from one column to another in steel or R.C.C systems. These systems will support the wall as well.
- The parapets are placed over the roofs of roof frameworks.
In flat slab structures, spandrel beams are being used to reinforce the link between both the slabs as well as the edge columns.
Advantages of Spandrel Beam:
The advantages of the distribution of spandrel beams are:
- The exterior walls of the multi-story structure are supported by spandrel beams.
- For buildings with large beam-column links, the use of a spandrel beam is advised to increase seismic efficiency. These uses of spandrel beam include both longitudinal and transverse reinforcement.
- Spandrel beams improve the lateral stability of steel and concrete.
- Spandrel beam is used along with coupled shear walls to improve stiffness and ductility against earthquake activity.
- Spandrel beams provide protection for exterior side openings such as windows, shear walls, and lintels.
- Spandrel beams have extra support on the outside walls of a multi-storey structure.
- Spandrel beams for both longitudinal and transverse reinforcement, which increase the seismic performance of the structure, are favored for large beam-column ties.
Disadvantages of Spandrel Beam:
- Since spandrel beams are mounted on the outside of a structure, they are often more vulnerable to moisture than floor beams resulting in the deterioration or corrosion of reinforcing steels.
- As a result of cracking and chewing asphalt, substantial money is spent on reconstruction.
Uses of Spandrel Beam:
- Spandrel beams have been used in multi-story structures on each floor.
- They are attached as a belt to the outer perimeter of the floor slab to support the floor beam.
- In addition, it enhances the connection between both the slab as well as the outer columns.
- The parapets are mounted above such beams on the roofs.
- The spandrel beam is built to transfer the load of the outer wall and the load of the slab from the slab to the outer column, and then the whole load is transferred across the column to the foundation.
- This produces a dynamic load management mechanism.
Spandrel Beam Design:
Any of the basic specification specifications are as follows:
- Internal torsion and shearing.
- End of beam torsion.
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- Transfer of the Load.
- The web flexion arising from the torsion balance.
- Ledge serving as a corbel at the end of the beam reaction.
- Flexure of the beam.
#1. Internal Torsion and Shear-
As applied vertical and horizontal loads do not move through the middle torsion of the beam. At every cross-section, the evolution of the torsion to the beam is the sum of the torques ( the shear force times the distance from the shear center ) acting at that cross-section.
It is likely that the loads applied to the beam which vary from the point of erection to when all time-dependent volume adjustments are done. Each loading case needs to be tracked to figure out who controls the design.
If the applied torsion and shear are established, the internal torsion and shear reinforcement can be calculated 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 added to the spandrel, the shear core can be considered to be very conservatively aligned with the vertical center line of the web beam.
#2. Beam End Torsion-
The beam end torsion is known as the torsion at the end of the beam within the distance “d” or “d/2” resulting from the torsion at the end of the beam.
Usually, the beam torsion produced by the top and bottom connections is defined 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-
Connection of the spandrel beam ledge to a web may be either even by the strength of plain concrete or even by the reinforcement of steel, based on the size of the beam, the strength of the concrete, and the scale of the ledge load.
The ledge to the horizontal cable attachment is known to be analogous to the motion of two hard bodies where the separation will occur over the whole length of the web of the beam mostly 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 provided for the movement of lead loads are based on the PCI Concept Handbook with some guidelines Variations. The load shift of the ledge would ful-fill the concrete punching shear if the special shear reinforcement is not to be used.
#5. Web Flexure Resulting from Torsion Equilibrium-
Two situations of web flexure can grow if the total torsion balance of the spandrel beam is produced by the
The web beam working against the top of the members it serves and the bottom connects at the end of the vertical spandrel.
Similar loading conditions may arise when horizontal loads are applied to the web of the beam, except that the forces are in a direction contrary to those arising 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.
Based on the cross-section dimensions of the beam and whether or not the spandrel uses support bars or pre-stressing strands, the techniques of analysis may be exactly the same or radically different.
If the relations between the spandrel beam and the structural units provided by the spandrel do not avoid torsional rotation, it will be appropriate to consider the effect of the main inertia axes on the service loads.
Spandrel beams typically may not have symmetry on either axis. If the depth of the beam is shallow, so 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.