Subtract the zero readings from the measured strains in order todetermine the true strains. Record these values in Table 3.
Calculate the equivalent member forces at 450N and record the values inTable 4 (experimental force). You will need the information below:To get the elastic modulus you need to calculate the stress over the strain:
E=
!
/
”
where
E
represents the
elastic modulus (N/m
2
);
!
represents
stress inthe member (N/m
2
) and
!
represents
the true strain in the member. Note to obtain the cross sectional area of each member, se the measureddiameter The elastic modulus for steel E = 210 GN/m
2.See the attached calculations sheet for the complete calculations.
.
Select one compression member (strut) and one tension member(tie) and plot the graph of the strain and the loads and comment on your graph. Members choosen from Table 3 are member 2(T) and 7(C).
Comment
As we can see from the graph, as the load increases the true strain in the member which is in tension, tends to increase drastically especially between load of 200N and load 300N. If we continue to increase the load,we see the same member tends to obtain a continual increase. In a different way, goes the true strain of member in compression. Therefore the strain, in member in compression increases directly with the load increase