CYCLONIC FATIGUE RATING FOR ELASTOMAX RIDGE CAP FIXING

DATE: JUNE, 1999

Background Material

Test of the Elasto-max adhesive were carried out at the Department of Civil Engineering at the University of Western Australia on 19-23 June, 1999. Cyclic fatigue tests, described in Australian Standards AS2050 and AS1170/2, were performed using a 2m x 1m x .5m vacuum test chamber to conform to test procedures specified in Appendix F of AS2050. Vacuum pressure and cycle control were maintained electronically by a calibrated National Instruments (1 psi) differential pressure transducer.

To conform to the test procedures in Appendix F of AS2050, the roof was cured for more than 28 days (35 days). The tiles were then watered for 72 hours at the rate of 3 litres per minute. Fatigue testing followed directly after the application of water. The total test time was 16 hours.

Calculation of Pressure

Calculation of cyclonic wind pressures was carried out using Section 3 of the Australian Standard for Wind Loading AS1170/2, as specified in Clause 1 of AS4055.

Test One: Two Story, C3 Rating

Test pressures were derived for a C3 rating on a two story dwelling with a roof pitch in excess of 15° in Terrain Category 2.5 with no shielding in a topographical classification T2, as prescribed in TABLE 1 and TABLE 3 of AS4055.

Relevant calculations from AS1170/2 are given below:

V_u = 70 m/s Fig 3.2.2 AS1170/2

M_z = 0.99 TABLE 3.2.5.2 AS1170/2

M₁ = 1.25 TABLE A3 AS4055

M_i = 1 TABLE 3.2.9 AS1170/2

Base Wind Pressure: q_z = 0.6 x (70 x 87 x 1.25)² / 1000 = 3.48 kPa Clause 3.3 AS1170/2

External Pressure Coefficient = -.5 (15° pitch) TABLE 3.4.3.2 AS1170/2

Internal Pressure Coefficient = 0.7 dominant opening TABLE B2 AS4055

Local Pressure Factor = 2.0 TABLE 3.4.5 AS1170/2

Porosity Factor = 0.9 TABLE 3.4.6 AS1170/2

Design Ultimate Wind Pressure: p = -0.9 x (2.0 x 0.5 + 0.7) x 3.48 kPa = -5.32 kPa

Fatigue Cycles

Fatigue cycles prescribed in both AS1170/2 and AS2050 specify:

8000 Cycles @ 2.12 kPa
2000 Cycles @ 2.66 kPa
200 Cycles @ 3.46 kPa
1 Cycle @ 5.32 kPa

Test One Results

Upon completion of the fatigue loading sequence, the suction chamber was removed, and the tiles were examined. All ridge tiles remained fixed to the roof tiles and no external cracks were visible. Some tile clouts were observed to have lifted, but no external damage was observed in the elastomax coating. All ridge tiles remained intact.

After disassembling the roof, the tile depth of the grout was measured. The grout had a rich appearance, with an average penetration of 50mm beneath the capping tile. There was some separation of the grout from the roof tiles, but not from the capping tile. The thickness of the elastomax coating was a minimum of 5mm.

Test Two: Single Story, C4 Rating, Category 2 Only

Test pressures were dervied for a C4 rating on a single story dwelling with a roof pitch in excess of 15° in Terrain Category 2 with no shielding in a topographic classification T2, as prescribed in TABLE 1 and TABLE 3 of AS4055.

Relevant calculations from AS1170/2 are given below:

V_u = 70 m/s Fig 3.2.2 AS1170/2

M_z = 0.91 TABLE 3.2.5.2 AS1170/2

M₁ = 1.25 TABLE A3 AS4055

M_i = 1 TABLE 3.2.9 AS1170/2

Base Wind Pressure: q_z = 0.6 x (70 x 91 x 1.25)² / 1000 = 3.80 kPa Clause 3.3 AS1170/2

External Pressure Coefficient = -.5 (15° pitch) TABLE 3.4.3.2 AS1170/2

Internal Pressure Coefficient = 0.7 dominant opening TABLE B2 AS4055

Local Pressure Factor = 2.0 TABLE 3.4.5 AS1170/2

Porosity Factor = 0.9 TABLE 3.4.6 AS1170/2

Design Ultimate Wind Pressure: p = -0.9 x (2.0 x 0.5 + 0.7) x 3.80 kPa = -5.82 kPa

Fatigue Cycles

Fatigue cycles prescribed in both AS1170/2 and AS2050 specify:

8000 Cycles @ 2.33 kPa
2000 Cycles @ 2.91 kPa
200 Cycles @ 3.78 kPa
1 Cycle @ 5.82 kPa

Test Two Results

Upon completion of the fatigue loading sequence, the suction chamber was removed, and the tiles were examined. All ridge tiles remained fixed to the roof tiles and no external cracks were visible. A majority of tile clouts were observed to have lifted, but no external damage was observed in the elastomax coating. All ridge tiles remained intact.

After disassembling the roof, the tile depth of the grout was measured. The grout had a rich appearance, with an average penetration of 60mm beneath the capping tile. There was some separation of the grout from the roof tiles, but not from the capping tile. The thickness of the elastomax coating was a minimum of 5mm.

Conclusions

Suction testing has demonstrated that an elastomax coating in excess of 5mm thickness, with a rich grout base in excess of 50mm width the withstand wind suctions characteristic of two story house with an AS4055 general C3 rating, and for a single story house with an AS4055 C4 rating in Terrain Category 2 (not Terrain Category 1).

Dr Kenneth T Kavanagh
Head
Department of Civil Engineering
University of Western Australia
Nedlands, W.A.