Calculate Dead Load of Beam w/ Solid Square Cross Section

[sperrya]

Homework Statement

A beam has a solid square cross section of 100mm and is simply supported by two supports 3m apart. Calculate the dead load that can be safely supported when applied to the middle of the beam.

Homework Equations

Solid square cross section of beam: 100mm
Material: unknown
Distance between two beams: 3m
Assumption: material is reinforced concrete
weight of material: 24KN/m₃


Area of square = height x width

volume = area of solid x length

dead load = volume x unit weight of material

The Attempt at a Solution

area of square = 100mm x 100mm = 10,000mm² (0.0100m²)

volume = 0.0100m² x 3m = 0.0300m³

dead load = 0.0300m³ x 24KN/m³ = 0.72KNVm³

∴ dead load = 0.72KNVm³ / m³ = 720N


Can someone please tell me where I am going wrong with this as I have been advised this is wrong but I don't know where.

Thanks in advance for your help.

 

[tiny-tim]

hi sperrya!

A beam has a solid square cross section of 100mm and is simply supported by two supports 3m apart. Calculate the dead load that can be safely supported when applied to the middle of the beam.
dead load = 0.0300m³ x 24KN/m³ = 0.72KNVm³

no, that's not a dead load, that's the weight of the beam

a "dead" load is an extra load on top of the beam (in this case, at its middle) …

what are the properties of the material of the beam that determine how much extra load can be supported? ​