# Homework Help: A question on thermal stress and axial force in a structure

1. Dec 23, 2015

### manutd@13

hi guys
i've really been struggling with this question but I still cant get any glimpse of idea on how to solve the problem,
so the conditions are given in the table and what the question is asking for is the axial force acting in each members of the structure.
ah, almost forgot to tell you that there is temperature rise of 40 degrees Celsius in all members.
help!!!

2. Dec 23, 2015

### haruspex

You will need to supply a translation of the question into English.

3. Dec 23, 2015

### manutd@13

translation of the question:
Area, Length and etc(e.g. young's modulus) information about each of the members are as given below, if there is rise of 40 degrees celcius in every member of the structure what would be the axial force in each of the members?

4. Dec 23, 2015

### haruspex

How are the members connected to each other and to the supports? Is something holding the supports a fixed distance apart?
Is the "A2" on AC correct? Should it perhaps be A1?
There's no mention of mass or density, so I assume we ignore gravity.

5. Dec 23, 2015

### Staff: Mentor

What is the equation for the tensile stress in a member as a function of the tensile strain in the member if there is thermal expansion present, with a temperature rise of ΔT? Have you learned such an equation?

If point A is displaced v in the y direction and u in the x direction, what is the strain in each of the members AB and AC? Member BC is easy to do because the strain in this member is zero.

6. Dec 23, 2015

### manutd@13

The connections are pinned connections, the strain equation is strain=a(▲t)L, and the A2 stated is correct

7. Dec 23, 2015

### manutd@13

The connections are pinned connections, the strain equation thermal increase/decrease is strain=a(▲t)L, and the A2 stated is correct, they are fixed distance apart, and the gravity is ignored yes

8. Dec 23, 2015

### Staff: Mentor

Your equation for the strain is not correct. Try again.

I'll give you a freebie, the answer to my first question in post #5 is:
$$σ=E(ε-αΔT)$$
where E is Young's modulus, σ is the tensile stress, and ε is the tensile strain.

9. Dec 23, 2015

### manutd@13

Ah i left out the youngs modulus;; that helps alot, i'l try again,thanks

10. Dec 23, 2015

### Staff: Mentor

Also, the L should not be in your strain equation.

Chet