Thesis presentation by Daniel Mill and Sudarshan Bhandari

1. PULL THROUGH FAILURE
PERFORMANCE OF LIGHT
GAUGE STEEL ROOF BATTENS
UNDER SIMULATED CYCLONIC
WIND LOADING
Daniel Mill and Sudarshan Bhandari

2. Cyclone Tracy (1974)

3. Darwin Area Building Manual (DABM)
 Northern territory implemented the DABM in 1975
 Consists of 10000 cycles of permissible load to 1.8 times of that load until it
fails.

4. TR440
 DABM has considered to be too conservative and TR440 been introduced at
1978
 Consists of simple loading sequence programme of
Load Cycles
62.5% of design load (DL) 8000
75% of DL 2000
100% 200
gxDL (g= no of tests) overload

5. Low High Low (LHL)
 Since the actual imitation of cyclones have not been considered by TR440,
the more likely (similar to cyclones) loading sequence have been proposed by
Mahen Mahendran on 1994, also listed in NCC.
Sequence Number of cycles
A 4500
B 600
C 80
D 1
E 80
F 600
G 4500

6. Basic failure modes
Two basic types of failure mechanism found on roof battens to the rafter
connection.
 Pull-out failure
 Pull-through failure

7. Research Problem Definition
 Accurate prediction on capacity of the battens are necessary.
 The current equation listed in the AS4600 overestimates the pull through
capacity and gives a lot higher values than the actual experiments.
 Static tests (slow rate loading) has been done in previous tests to accurately
predict the actual pull through capacity.
 Same capacity have been applied to the LHL tests to predict the cyclic
capacity.
 Some researches found that the cyclic capacity is actually higher than static
capacity which gives a very unusual results.
 Static capacity is taken when the crack initiates and load starts to drop,
however cyclic capacity is taken when the member disengage due to
complete pull through.

8. Research Aim
 Identify past research and testing relating to the low-cycle fatigue effect on
roof batten connections
 Test not only 0.75mm roof battens but also 0.55mm to further enhance results
and explore the possible effect of thickness on roof batten fatigue capacity
 Results to provide complete pull through failure capacities of the 0.75mm and
0.55mm battens for multilevel-level cyclic tests
 If results confirm static capacity is still lower than cyclic capacity, provide
recommendations.
 Assess the impact of loading rate on the static capacity of roof battens

9. Specimen details (0.55mm and 0.75mm)

10. Batten testing regime
0.55mm thick two span
slow load rate static tests
0.75mm thick two span
slow rate static tests
0.55mm thick cantilever
high load rate static tests
0.75mm thick cantilever
high load rate static tests
LHL

11. Testing setup- Static two span and LHL

12. Testing setup - Cantilever

13. Test plan
Test 0.55mm Batten 0.75mm Batten
High Speed Pull-Through
Cantilever (Static)
3 tests 3 tests
Slow Speed Pull-Through
Cantilever (Static)
1 test 1 test
Two-Span Test (Static) 3 tests 2 tests
Multi-Level Cyclic Test 1 tests 2 tests

14. Results
Two span slow loading rate
0.55mm static test (slow loading rate) 0.75mm static test (slow loading rate)

15. High loading rate cantilever
0.55mm static test (high loading rate) 0.75mm static test (high loading rate)

16. Two span static (slow rate loading)
Batten Type Static Capacity
(kN)
Mean COV
0.55mm (TS4055) 2.39, 2.29, 2.27 2.32 0.02
0.75mm (TS4075) 3.10, 3.10, 3.12 3.11 0.00

17. Multi-level Cyclic tests
0.75mm batten with 100% slow rate loading rate static capacity

18. Multi-level Cyclic tests
0.75mm batten with 110% slow rate loading rate static capacity

19. Multi-level Cyclic tests
0.55mm batten with 100% slow rate loading rate static capacity

20. Discussions and analysis
 Effect of Loading Rate on Static Capacity of Roof Battens
Test Batten
Size
High Load
Rate Static
Capacity (kN)
Slow Load
Rate Static
Capacity
(kN)
Cantilever 0.75 3.83 3.25
0.55 2.37 2.07

21. Discussions and analysis
 LHL loading sequence seems to be too soft due to possible underestimation of
the higher loads in the middle cycles and the minimum holding criteria
defined by NCC at the peak cycle.
 Just the initiation of crack for static failure criteria compared to complete
pull through for cyclic failure has not been equally accounted.
 Results shows that the thinner members are more vulnerable to the cyclic
loading than thicker members, furthermore thinner members have lesser
effect due to faster loading rate.

22. Acknowledgements
 Mahen Mahendran
 Myuran Kathekeyan
 Staffs at Banyo Pilot Precinct
 QUT Library services

23. The end
Thank you