The weight of a steel hollow section is key
in deciding just how heavy one might be or it will carry. It is this notion
which engineers, architects, and construction professionals must know.
Since steel hollow sections are common
components of buildings and other structures, those responsible for designing
and constructing them should be familiar with unit weights of these materials.
What is Unit Weight?
Unit weight or density, also known as
specific weight, is the weight per unit volume of a substance. For steel hollow
sections: this means the weight of an entire section by its length, generally
measured in kilograms per metre (kg/m) or pounds per foot (lb/ft).
A steel hollow section's unit weight depends
mainly on the density of the steel used, such as carbon or mild steel; wall
thicknesses for each section; and sizes of hollow spaces within it.
The
density of steel is approximately 7,850 kg/m³, a standard value for most types
of steel. But the unit weight of a steel hollow section varies according to its
shape and size.
The most common types for steel hollow
sections are square hollow sections (SHS), rectangular hollow sections (RHS)
and circular hollow sections (CHS) A square hollow section is a rectangular
one.
These various types each have different
geometric properties which affect their unit weights together.
What Affects the Unit Weight of Steel Hollow Sections?
Shape
and Geometry: The shape of the hollow
section affects its unit weight significantly. Circular hollow sections (chs)
have a more uniform distribution of material while square or rectangular
sections may possess pronounced edges or corners. These differences result in
varied amounts of steel needed to form each type of section.
Wall
Thickness: The thickness of the steel
walls in the hollow section is another determinant. Thicker walls will increase
the unit weight. This is because more material is used to form the section,
which always adds directly to its weight.
Dimensions
of the Section: Larger sections by
their nature entail greater volume and so weight. For instance, a large
rectangular hollow section weighs more than a small one given the greater
material volume entailed in its construction.
Material
Grade: While most hollow sections of
steel are made from mild steel, other grades steel such as high strength or
stainless steel may be used depending on the application. These materials have
different densities and so can affect the unit weight of final section is.
Calculation of Unit Weight for Steel Hollow Sections
To
calculate the unit weight of a steel hollow section, engineers often use the
formula: Unit Weight= Weight of Steel / Volume of the Section
For
a hollow section, the weight is found by considering the volume of steel in the
section--both outer and inner dimensions.
For instance, with a rectangular hollow
section (rhs), it can be calculated as subtracting the volume of the hollow
(inner dimensions) from the volume of the whole section (outer dimensions).
Let's do a sample calculation
For
example, we can only express what we mean in terms of units. In a rectangular
hollow section with an outside dimension of 50mm x 100 mm and inside this
overall size measure is 30mm then that would have 80 by 100mm internal
measurements (for cases where one leg differs from another-cases where three
sides are unequally sized are still regarded as being. In such a case, the
walls are 10mm thick.
The formula allows calculation of the volume
of steel in the section, and its weight is then obtained by multiplying this by
the density of steel (7,850 kg/m³).
Significance of Unit Weight
The
unit weight of steel hollow sections has significant implications for
structural design. With the weight in kg per metre, it allows engineers to
accurately calculate the total load that a structure will carry.
This helps in choosing both correctly sized
and appropriate type hallow sections used, which brings economic efficiency
without safety sacrifice. As heavier sections require more resources to
transport and install, other factors also come into play: How much material
gets used? What are the financial costs associated with these extra
weights-whether during shipment or in distribution?.
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