An upstand beam is one that has its structural top level elevated above the structural top level of the surrounding slab. In many cases, this style of beam may function as both a load-bearing beam and an architectural parapet. The elevation difference allows for drainage away from the structure and any other necessary amenities.
Upstand beams are commonly used in low-rise structures such as single-family homes, townhouses, and small apartment buildings. They provide much needed stability while also allowing for natural light and ventilation inside the building.
Upstand beams can be made of wood or steel. The type of material that is chosen depends on how long the building will remain standing after being sold by the original builder. If this structure is only expected to last 10 years for example, then a wood beam would be appropriate because it would not need to be replaced for many years after it was installed. But if it is expected to last for decades or even centuries, then a steel beam would be best because it will still look good after many years.
The elevation difference between a wooden upstand beam and a steel one can be as high as. These differences in beam type and quality must be taken into account when specifying materials for construction projects.
An upstand beam is often constructed as a rectangular beam, regardless of whether it is in the positive or negative moment zone. However, at the zones of negative moment, it is theoretically conceivable to construct it as an inverted T or L beam. In practice, however, such beams are very rarely used because they can be difficult to produce and install properly.
The main advantage of an upstand beam is that it can support more load than a parallel beam of the same size and material. This is because the force applied to the end supports is shared between them, whereas with a parallel beam only one third of the force is shared.
Also, an upstand beam does not have to be as strong as a parallel beam of the same size and material because it is supported at both ends. Therefore, it can be made of lighter material which reduces its weight but increases its flexibility. A disadvantage of an upstand beam is that it takes more space when laid out horizontally because it has no vertical members like a parallel beam to divide the distance between supports down the middle.
An example of an upstand beam is the center beam on a flatcar. The two halves of the center beam rest on top of the rails and connect to them at their centers. Because the force is shared between the end supports, this beam can be much thinner than a corresponding parallel beam without losing strength.
In some cases, a beam can be a hybrid of an upstand and a downstand, with both the beam top and the soffit protruding upwards and downwards from those of the surrounding slab. A slab beam (also known as a concealed beam) is one that has its top and soffit at the same level as the surrounding slab. They're commonly used where aesthetics are important such as in home kitchens or bathrooms.
Beams come in various shapes and sizes. The most common types are I-beams and H-beams. I-beams have two parallel sides and a flat bottom, while H-beams have three perpendicular sides and a flat bottom. Certain beams are also called "double" or "triple" beams because they have more than one surface. For example, an H-beam with flat tops and flat bottoms is also called an H-beam double-top.
The length of beams varies too. Short beams are usually required when building small spaces such as apartments, while long beams are needed for large rooms like churches or warehouses. Beams can also be semi-long or half-width. Half-width beams have dimensions that are half way between short and long. Semi-long beams have lengths that are almost equal to their widths.
Finally, beams can be straight or curved. Curved beams are used where straight ones would interfere with other parts of the structure or house the roof.