1. Topic 19: Bracing theory, terms and elements.
Unitec New Zealand
Construction Systems 1
Topic introduction, overview and threshold concepts.
Remember this is a big lecture keep it moving
Topic 19: Bracing theory, terms and elements.
© Unitec New Zealand

2. Intention of this short overview.
Students will be introduced to the fundamentals and basics of the topic area content.
Words and terms used in designing bracing in accordance with NZS3604 will be defined and explained including the units employed to measure bracing requirements.
Typical elements used in providing bracing to the sub- floors , walls and roofs of a typical timber framed dwelling to NZS3604 will be identified using photos , images and drawings .

3. Timber Framing and Loadbearing Masonry.
“Timber framing pretty good in EQ, load bearing brick not so much”
P Etherington , UNITEC.

4. Bracing theory. What is meant by BRACING anyway ?
Definition:
Any method employed to provide lateral support to a building .
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

5. The two main lateral forces that we have to be concerned with are -:
Bracing theory. What are we actually bracing against ?
The two main lateral forces that we have to be concerned with are -:
WIND and EARTHQUAKE.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
© Unitec New Zealand

6. Bracing theory. What are we actually bracing against ?
WIND and EARTHQUAKE.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

7. Bracing theory. What parts of a typical house have to be braced?
What’s to brace?
Roof:
Sheets
Metal strapping
Timber framing
Walls :
Proprietary steel frame inserts ( Gamma etc )
Diaphragms
Sub-floor :
Brace or anchor piles
Cantilevered piles
Concrete block walls
Exterior Cladding or framing
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
© Unitec, Mushtak Dawood

8. Bracing theory. What is meant by bracing DEMAND?
BRACING DEMAND. -: The horizontal forces resisted by a whole building
or by an element within a building.
These horizontal forces are a result
of wind or earthquake action.
Bracing demand forces are measured in
bracing units (BUs).
They shall be determined as set out in 5.2 (wind) or
5.3 (earthquake
Demand is measured in Bus for Wind
Demand is measured in BU’s / Sq m for Earthquake.
Demand is what we actually work out from the tables in NZS3604:2011
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

9. Bracing theory. What is meant by bracing CAPACITY?
BRACING CAPACITY. -: Strength of bracing of a whole building or of
elements within a building. Bracing capacity is measured in bracing units
(BUs), and shall be determined from section 5.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Source- GAMMA bracing systems .
Capacity is what we actually build into the project or house to strengthen it against the lateral forces of Wind and Earthquake.

10. Bracing theory. ALONG and ACROSS ? Whats’ that all about ?
ALONG and ACROSS refer to WIND demand.
The key element to identify here is the RIDGE.
ALONG is parallel to the ridge .
ACROSS is at right angles to the ridge.
HIP ROOFS -:
Use the across values from the tables to work out demand in both directions
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

11. Bracing theory. What is meant by a bracing ELEMENT?
WALL BRACING / WALL BRACING ELEMENT : A section of wall above the
ground floor level that performs a bracing function.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

12. Bracing theory. What are BRACING LINES ?
BRACING LINE. A line along or across a building for controlling the distribution of wall bracing elements.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Bracing lines are only seen on plans .
They are not something we build.
Just a design aid.

13. Bracing theory. What does NZS3604 mean by BRACING DISTRIBUTION?
Wall bracing elements shall be located as close as possible to the corners of external walls and evenly throughout the building.
Bracing elements shall be evenly distributed along each line as far as is possible.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Don’t put all your reinforcements in the one place !

14. Bracing theory. What does NZS3604 mean by BRACING DISTRIBUTION?
Christchurch.
New set of three storey of townhouses (row houses) where the main floor completely collapsed .
Squished car poking out of the bottom.
This was before the rule about 50% of the total bracing demand / no. brace lines so there was very little bracing on the front where the car ports were on the ground floor and it rocked back and forth a couple times and came straight down.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

15. Bracing theory. What is a DIAPHRAGM and its effect on bracing?
DIAPHRAGM. A building element such as a floor or ceiling capable of
transferring loads in its own plane to boundary members.
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

16. Bracing theory. What is a DRAGON TIE and how does it affect bracing?
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)
Dragon ties don’t contribute to the bracing capacity but, like diaphragms, let us space the bracing lines further apart .

17. Bracing theory. What do BRACING PLANS look like ?
The Sub-floor is the bottom most structural floor
Supports all of the super structure; and,
Suspended first floor
Pull up the 3D PDF of a house and show the sub floor
Point out the basic elements
Pile Footing
Pile
Bearer
Joist
Note the Anchor Piles and the Ordinary Piles (not in the right location)

18. END
Image sources-:
Slide 1- Unitec, Phil Etherington.
Slide 2- Unitec, R Kelly, MmcGarrigle 2014
Slide 3 - Unitec, Phil Etherington.
Slide 4-Renovate.org.nz. E architect.co.uk, Gamma Bracing
Slide 5- GIB living .co.nz
Slide 6
Slide 7- Clipart, M Dawood.
Slide 8- NZS
Slide 9- GIB Bracing manual, Gamma Bracing.
Slide 10- NZS
Slide 11- Carter Holt Harvey, Gamma Bracing products.
Slide 12-Lifesun.info , R Packard, Unitec.
Slide 13- LaSalle.edu, R Packard, Unitec.
Slide 14- Unitec, Phil Etherington.
Slide 15- Wood solutions Australia.
Slide 16-NZS 3604, Ted Carpentry
Slide 17- Rohan Packard Unitec, Doc
“Next session we will be exploring the principles of Bracing Design in accordance with NZS 3604:2011.
© Unitec New Zealand