Week 5

Question 1

What is the overview of ‘Load Transferring’?

Answer 1

Load -> Beams -> Structural columns -> Sub soil layer

Question 2

What are the 3 axes?

Answer 2

• Longitudinal axis (length of beam/height of column)
• Major axis (longer than minor)
• Minor axis (shorter than major)

Question 3

What are the 2 types of beam support conditions?

Answer 3

1. Pinned (simply supported) (less than 90deg with load)
2. Fixed (rigid) (Kept at 90deg with load)

Question 4

What zone of a concrete beam would reinforcement steel be placed?

Answer 4

Tension zone.

Concrete is weak in tension but strong in compression

Question 5

What are the bending stresses of simply supported/pinned connection?

Answer 5

• The bending moment at the supports are zero
• The maximum bending moment occurs at the mid span
• The area of tensile reinforcement steel is highest at the mid span (most bending)

Question 6

What are the bending stresses of fixed/rigid connection?

Answer 6

Two bending moment types:
1. Hogging moments near the support (maximum hogging moment is at the support)
2. Sagging moments near the mid span (maximum sagging moment is at the mid span)

• The maximum sagging moment is significantly smaller than in the maximum sagging moment in the simply supported case.
• Therefore smaller cross-sections for beams with fixed connections can be used

Question 7

What are the shear stresses of concrete beams?

Answer 7

• Tends to deform the beam
• Concrete is weak in shear (shear-links/stirrups) are used in beams to resist shear stresses developed by transverse loading
• The stirrups have longitudinal bars top and bottom -> for tensile strength requirements, and minimise shrinkage and cracks in concrete

Question 8

What is axial loading?

Answer 8

Pure compression, generally upright beams

Question 9

What is eccentric loading?

Answer 9

Load that is along the X-X, Y-Y, or X-Y axis (not centre)

Question 10

What is pad footing?

Answer 10

• Interface between structural column and foundation material
• Reduces the stress transferred to the sub-soil by structural columns

Question 11

What are the 4 minimum cover requirements are specified to AS 3600?

Answer 11

1. Concrete grade used
2. Exposure classification
3. Method of formwork
4. Method of compaction

Question 12

What are cover blocks used for?

Answer 12

• Attatched between the formwork and the bottom of the outermost reinforcements
• Ensures minimum cover requirements

Question 13

What is Newtons Law?
(In reference to support beams)

Answer 13

• Must be an equal and opposite force (‘T’)
• Counter balance is created by bond between the rebar and surrounding concrete

Question 14

What is splicing of reinforcement bars?

Answer 14

• Joining two bars to provide a required length, a splice shall be provided
• Splicing transfers stress between two bars
• Overall length of two bars -> ‘Lap Length’
• Staggering splicing minimises weak points

Question 15

What loads do suspended floors withstand?

Answer 15

• Dead loads: weight of the structural elements (for example, self-weight of the slab)
• Superimposed dead loads: weight of the non-structural elements (such as weight of floor finishes)
• Live load: weight of furniture and people

Question 16

What stresses do suspended floors withstand?

Answer 16

• Bending stresses
• Shear stresses
• Torsional stresses

Question 17

List 2 characteristics of thermal resistance in suspended floors.

Answer 17

• Suspended floors do not always need thermal insulation
• Suspended slabs with in-slab heating/cooling systems should be insulated
  (min. R value should be 1.0)

Question 18

What is slab action?

Answer 18

How applied load on a suspended floor is distributed/transferred to its structural supports

Question 19

What is a ‘one-way slab’?

Answer 19

Slab supported at two edges

Question 20

What is a ‘two-way slab’?

Answer 20

Slab supported at four edges

Question 21

List the 5 benefits of concrete over timber floors.

Answer 21

1. High level of durability
2. Sufficient stiffness to avoid deflection under load (will not affect other elements of the building)
3. Energy efficient because of their high thermal mass
4. High level of acoustic performance which meets BCA requirements
5. Constructed quickly where precast or composite elements are used

Question 22

What are ‘composite concrete floors’?

Answer 22

• Made of concrete & steel
• Steel decking acts as permanent formwork

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Question 22

What are ‘insitu concrete floors’?

Answer 22

• Designed to support walls anywhere within a slab
• The most flexible concrete floor type

Question 23

What are ‘precast concrete floors’?