reinforced concrete

what is a beam?

structural elements that take external loads which cause bending moments, shear forces and torsional moments along their length

what are the four kind of failures a beam can experience?

1. flexural failure

2. shear-tension failure

3. diagonal tension failure

4. shear compression failure

what does C16/20 tell you about the concrete

• the numbers tell you the characteristic compressive strength of the concrete after 28 days

• the first number refers to the characteristic strength of a cylinder of concrete. so this concrete has a compressive strength of 16MPawhen in a cylinder shape

• the second number refers to the characteristic strength of a cube of concrete. so this concrete has a compressive strength of 20MPa when in a cube shape

why do concrete and steel make a good pairing?

• concrete has a very high compressive strength while steel is very ductile and has good tensile strength

• concrete is brittle so combining it with steel increases the tensile strength

• both materials have similar levels of thermal expansion

• the pH level of the concrete is compatible with the steel (if the pH >12 then it will corrode the steel

• the steel stops the reinforced concrete from failing suddenly

how can a beam resist shear force?

increase the number of shear links by the joints because that’s where the shear force is strongest

how can you protect the reinforcement in the concrete?

• increase the concrete cover

• use materials (like glass fibre) that don’t corrode

• use anti corrosion paint on the steel bars