Week 4 WORKSHOP

During the workshop time, our group

needed to built a 1m ‘bridge’ with 3

same dimension woods and one

plywood. As for thinking and testing

by hand about different

characteristics of wood and plywood,

we found that the plywood pretty

much softer than the wood which is

easily to be deformed. As for the

wood, it is the material which can

return to its original shape easily

under stress, which means that the

elasticity of wood is better than the

plywood.

As for the main structure of our ‘bridge’, we

make the wood vertical standing with the

plywood underneath, as we thought the plywood

is not easy to break under stress as the

deformation is better.

This side view sketch is to illustrate the

connection, which we use the common

nails for general construction. Each wood

bricks has two nails connected to the wood

same as the back side of plywood.

During the test, the basic data of the

compression on the ‘bridge’ is 9KG, as the

increase of the pressure, the first breakage

is under the strength of 280KG. The place

of the first fracture take place on the wood

(as shown on the picture). As what we

guessed, the plywood is really soft material

for deforming , which is not easy to be

broken even under high strength of

compression.

These two photos

show the deformation

of our bridge under

compression from 38

to 40.

After the testing, it reminds me one things

that said on the textbook. Grain direction is

the major determining factor using the

wood as the structural material. As the data

provided in the textbook, “the allowable

compressive force perpendicular to its grain

is only about 1/5 to 1/2 of allowable

compressive force parallel to the grain”

(Ching, 2008,p12.11). It can easily found in

the left picture, the compression on the

wood is perpendicular to the grain of the

wood, thus, it make me think that the

strength can increase of the grain is parallel

to the strength.

Reference: Ching, F 2008, Building Construction Illustrated, n.p.: Hoboken, N.J. : John Wiley & Sons, c2008