EDEXCEL DT Timbers 7.4 - strengthening timber

What are the 3 forces that can act on a timber + a little explanation

• compression, is a squashing force like standing on something

• tension, is a pulling force like tugging on ends of a rope

• shear, forces that act in opposite direction, pushing one side up and the other side down, like the cutting action of scissors

What are the natural forces within timber as it grows

the wind blows which can cause the tree to lean to one side

the leaning action stresses the wood so when the wood is cut it can bend or crack

what are pre-stressed construction beams

by putting the timber in tension when the beam is being made, it will stretch less when weight is on the beam.

this makes the beam bend less and be stronger

What are the 5 reinforcement and stiffening techniques

• frame strctures

• fabrication,assembly and construction processes

• lamination

• braces and tie bars

• embedding composite material

What are frame structures

a square or a rectangle a usefull shapes butt hey are not very strong the corners can twist deforming it

A rectangle can be strengthened by

• putting a thin panel inside the frame

• adding a diagonal strut or triangle across each of the corners

• by adding a strut from corner to corner to make two triangles

What are fabrication,assembly and construction processes

fabrication porcesses are the processes used to make the parts of something

assembly processes are the processes used to put the parts together

What is lamination

a laminate is a thine layer of material

lamination is sueful to make curved shapes from timber y the thin layers being glued and bent into shape

lamination also greatly improves the strength

What are braces and tie bars

a brace is a bar added to a frame to strengthen it they are usually diagonal to make triangular shapes

a tie bar is similar but is a rod good in tension, normally steel is used. The rod is fixd to the frame, and since it cannot stretch, the frame holds it shape

Whis is embedding composite materials

adding composite materials to timber can improve its proerties

fibreglass can be used to make it strong, hardwearing and give a waterprrof shell.

fibres can be laminated to increase strength

steel atrips can be fixed to timber due to its high tensile strength making the wood stronger