CIVL2201 STRUCTURAL MECHANICS 2014: ASSIGNMENT 2

SCHOOL OF CIVIL ENGINEERING

CIVL2201 STRUCTURAL MECHANICS 2014: ASSIGNMENT 2

SUBMISSION REQUIREMENTS  Assignment is due to your tutor at the start of your tutorial (either 11 am or 2 pm) on Friday 23 May

2014. The hard copy of the assignment should include your working and answers for question 1, plus a printout of your answer to question 2. Please submit stapled sheets without any manilla folders or slip in sheet protectors etc, and include the assignment cover sheet. There is no requirement to email to Prof Smith.

ACADEMIC HONESTY  Students are always encouraged to help each other with studying, however copying solutions from

anyone, where you have little or no academic input is not acceptable.  Any form of copying and pasting electronic data for question 2 is not acceptable.

The details of your submission depend on your tutorial group. 1) A timber beam, with rectangular cross section (h × b) is reinforced with additional full width (b) steel plates.

There is a plate of thickness t securely connected on the bottom and a plate of thickness 2t on the top of the timber to ensure composite action in bending. The section is then used as a simply supported beam of length L. The beam is oriented such that the minor principal axis is vertical. It should be taken that ρsteel = 7850 kg/m

3, ρtimber = 1000 kg/m 3, Etimber = 11000 MPa and Esteel = 200000 MPa, and that both

materials exhibit linear elastic behaviour. The design engineer needs to ensure that the normal bending stress (tension or compression) does not exceed 8 MPa (for the timber) or 250 MPa (for the steel). The beam experiences a vertically downwards point load of magnitude P acting mimdspan. It can be assumed that the self-weight of the steel-timber beam is negligible compared to the value of P.

a) Before the steel plates are connected (ie based on the timber beam only) what is the maximum value of P that can be applied before the timber reaches its maximum stress.

b) For the value of P calculated in (a), what is the maximum deflection of the beam. c) The steel plates are then added. What new value of P will induce the critical bending stress (8 MPa

(for the timber) or 250 MPa (for the steel))? Draw the stress and strain distributions (values required) for both the steel and the timber on the critical cross-section when this occurs.

d) For MPE masters students in CIVL5508 only: Is the use of 2 differently sized steel plates (t & 2t) the optimal use of material? Discuss. About ½ page of discussion and possibly formulae but not actual calculations plus appropriate diagrams is expected.

Group  h (mm)  b (mm)  t (mm)  L (m) 

2A  300  210  4  3.5 

2B  325  190  5  4 

2C  350  210  7  4.25 

2D  275  190  5  3.25 

2E  250  210  7  3.1 

2F  300  190  4  3.6 

11A  300  220  12  4.2 

11B  325  225  6  3.8 

11C  350  220  4  4.1 

11D  275  175  6  3.75 

11E  250  185  9  3.6 

11F  300  195  3  4.2 

2) Read all of Chapter 2 of the ASCE / FEMA World Trade Center Building Performance Study which can be downloaded from the Blackboard eLearning site.

Identify a portion of the report which in your opinion relates to any issue you have studied in your degree so far (it does not have to be in Structural Mechanics). If you are a repeating student, you must write about a different issue to what you may have written in the past. Write approximately 300 words plus a diagram explaining how this issue relates to what you have studied. This is not an email to Prof Smith. Just include your summary in the hard copy of your assignment. If you are a repeating student, you are obliged to choose a different portion of the report to read.

Tim Wilkinson Tim Wilkinson Senior Lecturer in Civil Engineering