2022/3/22 10:00 Assignment 1 - 2022 [20 marks]: CIVL3205 CIVL9205 Concrete Structures 1
https://canvas.sydney.edu.au/courses/39643/pages/assignment-1-2022-20-marks 1/3
Assignment 1 - 2022 [20 marks]
Submission date: 25 March 2022
General instructions
– Answers to questions should be provided in A4 size format.
– Make sure to provide a detailed description and explanation of all steps of your thinking process
and calculations when answering each question. Always provide the clause(s) of the standard you
are applying in each step.
– If a question does not provide the values of the variables required to calculate the solution,
make sure to select appropriate values for these variables based on your engineering judgment.
Make sure to point out when such assumptions are introduced.
– This assignment accounts for 20% of your final mark at the UoS. In accordance with University
policy (see Canvas for more information), the following penalties apply when written work is
submitted after 11:59pm on the due date: deduction of 5% of the maximum mark for each
calendar day after the due date; after ten calendar days late, a mark of zero will be awarded.
– Make sure to carefully read and answer all questions of this assignment.

In all questions below assume a characteristic compressive strength given by the last digit
of your personal S.I.D. number, according to the following table.
Last S.I.D. digit f' (MPa)
0, 3, 6, or 9 25
1, 4, or 7 32
2, 5, or 8 40
E.g. if your S.I.D. number is 310187753, then f' will be 25 MPa.

Question 1
A concrete column in a building in Melbourne is located near the coast and has a cross-section of
0.3 m by 0.4 m. The formwork was removed at 7 days after setting, leaving all surfaces exposed
to the environment afterwards. Knowing that the concrete column will be uniformly loaded with a
compressive stress of 0.3f ’ at 28 days of age, calculate:
c
c
c
2022/3/22 10:00 Assignment 1 - 2022 [20 marks]: CIVL3205 CIVL9205 Concrete Structures 1
https://canvas.sydney.edu.au/courses/39643/pages/assignment-1-2022-20-marks 2/3
(2.5 marks) a) The creep after 28 days of sustained loading.
(2.5 marks) b) The creep at 56 days of age assuming that the load is now gradually applied from
28 days of age up to 56 days of age.

Question 2
An elevated pedestrian walkway in Sydney is constructed using a rectangular reinforced concrete
section 2m wide, see structural scheme in Fig. 1. The slab is simply supported and has an
effective span of 4.0 m between supports.
The slab is doubly reinforced with 14 bars D500N12 at the top and 18 bars D500N12 at the
bottom. The clear concrete cover to the reinforcing bars is 30 mm (note: there are no stirrups).
The slab is required to support the own weight (25 kN/m ) and a live load of 4 kPa is applied
occasionally on or after 28 days of age.
Fig. 1 – Structural scheme

Under these conditions:
(2.5 marks) a) Calculate the short-term and long-term loading applied to the structure. Justify
carefully your choice of Ψ and Ψ .

In the following questions, you may assume Ψ =1 and Ψ =0. Using appropriate transformed
section properties, calculate:
(2.5 marks) b) The expected mid-span deflection of the slab immediately after loading the slab at
28 days of age.
(2.5 marks) c) The total long-term deflection of the slab in accordance with the simplified
approach in AS 3600.

Question 3
Fig. 2 shows the cross-section of a concrete T-beam located inside a non-residential building. The
beam is flexurally reinforced for a sagging moment with three D500N28 bars in the tension face
and two D500N28 bars in the compression face, being D500N12 bars used for stirrups. The
effective width of the flange is the entire width (i.e. 600 mm).
3
s l
s l
2022/3/22 10:00 Assignment 1 - 2022 [20 marks]: CIVL3205 CIVL9205 Concrete Structures 1
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In the following questions assume a concrete cover of 25 mm whenever needed. Under these
assumptions:
(2.5 marks) a) Calculate both nominal and design ultimate moment capacities (M and ΦM ) for
sagging, carefully verifying/justifying all assumptions made during calculations. Note: you may
disregard the top reinforcement in the calculations.
(2.5 marks) b) If the same cross-section were subjected to a hogging moment, how would its
behaviour change in terms of the neutral axis and ultimate moment capacity? Carefully justify your
answer.

Question 4
(2.5 marks) The apparent strength of concrete is dependent on the duration of loading and the
size/shape of the concrete specimen. How can this be explained?

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