Movement of materials

Question 1

When we talk about the movement of materials, what do we need to consider?

Answer 1

Whether the movement is permanent or non-permanent deformation

Question 2

What is the value of E for steel?

Answer 2

205 GPa

Question 3

What is the value of E for concrete?

Answer 3

30-50GPa

Question 4

What is the value of E for timber?

Answer 4

10-40GPa

Question 5

What is the value of E for masonry?

Answer 5

10-50 GPa

Question 6

What is ‘creep’?

Answer 6

Under sustained loading most materials will gradually continue to deform under a sustained load

Question 7

If the load is sustained for a long period of time, what happens to the strain?

Answer 7

It gradually increases without an increase in load (creep)

Question 8

What happens when a creep load is removed?

Answer 8

The elastic recovery is immediately recovered, and the deformation is slowly recovered with time, which is the creep (plastic recovery).

Question 9

What happens of there are higher stress levels in concrete to creep?

Answer 9

Larger creep

Question 10

What causes the creep in timber to become more of a risk?

Answer 10

An increase in moisture content

Question 11

When is creep more significant in timber?

Answer 11

When the load applied is perpendicular to the strain

Question 12

What is the rate of creep in fibre-reinforced polymers dependant on?

Answer 12

The temperature and level of stress experienced by the resin

Question 13

Describe the drying shrinkage in concrete elements:

Answer 13

Some water in a concrete mix does not undergo ‘hydration’ with cement, and these water molecules are bonded with the concrete ingredients. Concrete can lose the absorbed water, causing a loss in volume.

The use of good quality aggregates and a low water/cement ratio reduces shirnkage

Question 14

What happens to clay brickwork as it draws in moisture?

Answer 14

It expands significantly

Question 15

What happens to blockwork (concrete) when moisture is lost?

Answer 15

It shrinks

Question 16

Why does shrinkage behaviour of timber vary in directions?

Answer 16

Due to the growth pattern of timber

Question 17

How do you reduce shrinkage of timber?

Answer 17

As the timber dries out, moisture should be supplied, this should be installed at around 20%

Question 18

What does a higher coeffient of thermal expansion mean?

Answer 18

The more susceptible to movement when a material is subject to a change in temperature

Question 19

What does the similar coefficient in thermal expansion of steel and concrete permit?

Answer 19

Their widespread use in reinforcement concrete elements

Question 20

How is thermal movement accommodated for?

Answer 20

Structure is designed to resist forces or have movement joints, which can accommodate for expansion/contraction.