THE HOBSON · used to calculate the ultimate limit state design pressure. The wind always finds the...
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HOBSON THE www.hobson.com.au Volume 30 From the desk of Peter Hobson In This Issue: Cyclone Testing - Trials C3 & C6 1 Wedge-Locking Fastening Solutions 4 Fastening Problems in Sydney 5 Web Portal Tips 6 Hobson Newsfeed 7 Hobson on Location 8 Merry Christmas 8 Cyclone Testing Hobson Engineering (HEC) are extending our screw range to incorporate the HEC Universal Multi-Seal Cy- clone Assembly. These products will soon be available, endorsed, like all Hobson products, with the assurance that they have been tried and tested to perform to the high standard that our customers rely on. To ensure full confidence in the Universal Multi-Seal Cyclone Assembly we have recently completed testing at the James Cook University (JCU) Cyclone Testing Station in Townsville. In discussion with JCU and DEKS Industries, we instructed JCU to carry out Static and Cyclic simulated wind load strength testing of the Assembly. The Universal Multi-Seal Cyclone Assembly is comprised of 14-10x53mm self-drilling screw and a bonded 25mm aluminium washer. The washer with a bonded EPDM seal has an improved design giving the assembly greater performance. All tests, static and cyclic Low-High-Low (LHL), were conducted in an airbox as pictured, which is located in the wind tunnel facility at JCU. All trials for this testing were performed in accordance with NATA require- ments and in conjunction with JCU, DEKS Industries and our knowledge of the Shed and Roofing Industry. Purlins, cladding and roof sheets were selected to give results best suited to the application of the HEC Multi-Cyclone Assembly. Universal Multi-Seal Cyclone Assembly The airbox is an open topped pressure chamber just over 10m long and 2m wide. It is used to simulate wind pressure on structural roof sheeting, wall cladding, fasteners and other various building components. The airbox is used to predict the likely response of products when subjected to high wind pressures. We used the JCU facility to verify the performance of our Universal Multi-Seal Cyclone Assem- bly and develop span tables to show the parameters for using this product. The airbox works by air being supplied to the chamber using two large centrifugal fans, powered by 45 kW motors. The Airbox They can generate air pressure far in excess of what the strongest tropical cyclone would inflict on a shed or house. This pressure can be made to simulate the com- bined effect of both outward pressure (suction) and the internal positive pressure acting on the cladding. Com- puter controlled valves apply uniform pressure for both static and cyclic pressures to simulate the gustiness with- in a tropical cyclone or steady state pressure to simulate gale winds. The box can be divided into compartments so that strategic opening or closing of the inlet ducts can produce different pressures, testing the fastener and cladding performance. A transducer was used to mea- sure the applied loads. Assembly and cladding under load Static testing applies increasing pressure onto the back of the roofing sheet in increments, and each pressure is held for a set period of time. This procedure is repeated until failure of either the sheet or assembly or the maxi- mum capacity of the airbox is reached. The last reading at which the assembly was able to support the load is used to calculate the ultimate limit state design pressure. The wind always finds the weakest link, therefore, com- pleting static testing gave us the data to set the criteria for the LHL cyclic testing. Static Testing
Transcript of THE HOBSON · used to calculate the ultimate limit state design pressure. The wind always finds the...
HOBSONTHE
www.hobson.com.au
Volume 30
From the desk of Peter Hobson
In This Issue:Cyclone Testing - Trials C3 & C6 1
Wedge-Locking Fastening Solutions 4
Fastening Problems in Sydney 5
Web Portal Tips 6
Hobson Newsfeed 7
Hobson on Location 8
Merry Christmas 8
Cyclone TestingHobson Engineering (HEC) are extending our screw range to incorporate the HEC Universal Multi-Seal Cy-clone Assembly. These products will soon be available, endorsed, like all Hobson products, with the assurance that they have been tried and tested to perform to the high standard that our customers rely on. To ensure full confidence in the Universal Multi-Seal Cyclone Assembly we have recently completed testing at the James Cook University (JCU) Cyclone Testing Station in Townsville. In discussion with JCU and DEKS Industries, we instructed JCU to carry out Static and Cyclic simulated wind load strength testing of the Assembly.
The Universal Multi-Seal Cyclone Assembly is comprised of 14-10x53mm self-drilling screw and a bonded 25mm aluminium washer. The washer with a bonded EPDM seal has an improved design giving the assembly greater performance. All tests, static and cyclic Low-High-Low (LHL), were conducted in an airbox as pictured, which is located in the wind tunnel facility at JCU. All trials for this testing were performed in accordance with NATA require-ments and in conjunction with JCU, DEKS Industries and our knowledge of the Shed and Roofing Industry. Purlins, cladding and roof sheets were selected to give results best suited to the application of the HEC Multi-Cyclone Assembly.
Universal Multi-Seal Cyclone Assembly
The airbox is an open topped pressure chamber just over 10m long and 2m wide. It is used to simulate wind pressure on structural roof sheeting, wall cladding, fasteners and other various building components. The airbox is used to predict the likely response of products when subjected to high wind pressures. We used the JCU facility to verify the performance of our Universal Multi-Seal Cyclone Assem-bly and develop span tables to show the parameters for using this product. The airbox works by air being supplied to the chamber using two large centrifugal fans, powered by 45 kW motors.
The Airbox
They can generate air pressure far in excess of what the strongest tropical cyclone would inflict on a shed or house. This pressure can be made to simulate the com-bined effect of both outward pressure (suction) and the internal positive pressure acting on the cladding. Com-puter controlled valves apply uniform pressure for both static and cyclic pressures to simulate the gustiness with-in a tropical cyclone or steady state pressure to simulate gale winds. The box can be divided into compartments so that strategic opening or closing of the inlet ducts can produce different pressures, testing the fastener and cladding performance. A transducer was used to mea-sure the applied loads.
Assembly and cladding under load
Static testing applies increasing pressure onto the back of the roofing sheet in increments, and each pressure is held for a set period of time. This procedure is repeated until failure of either the sheet or assembly or the maxi-mum capacity of the airbox is reached. The last reading at which the assembly was able to support the load is used to calculate the ultimate limit state design pressure. The wind always finds the weakest link, therefore, com-pleting static testing gave us the data to set the criteria for the LHL cyclic testing.
Static Testing
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LHL cyclic testing of the Universal Multi-Seal Cyclone Assembly, cladding and immediate members is carried out over many hours of LHL testing, achieved by opening and closing pressure dump valves representing cyclone gusts. The assembly and cladding is subjected to the relevant fatigue loading sequence as shown in table 2. The fatigue loading sequence increases cyclic simulated wind load strength tests then decreases them back to the starting load. During the test the assembly and cladding are examined for any permanent distortion, fracture or damage.
LHL Cyclic Testing
Sequence No. of Cyles
Cummulative Cycles Load
A 4500 4500 0 to 0.45 Pt
B 600 5100 0 to 0.60 Pt
C 80 5180 0 to 0.80 Pt
D 1 5181 0 to 1.00 Pt
E 80 5261 0 to 0.80 Pt
F 600 5861 0 to 0.60 Pt
G 4500 10361 0 to 0.45 Pt
As previously mentioned, in order to replicate the typi-cal materials used in domestic dwellings, steel sheds, garages and roofing, HEC conducted extensive testing using three base metal thicknesses (BMT) of cladding supports, purlins and roof battens, and two types of com-monly used cladding. The cladding selected was 0.42 mm Monoclad and Corrugated sheeting, and 0.75 mm top hat roofing battens, 1.0 mm and 1.5 mm BMT purlins. The top hat material was fixed into timber supports using HEC 12-11 x 40 mm vmaX batten screws, and various spans were tested. The methods of testing were carried out in accordance with AS 1562.1 and AS 4040.2. The following span tables were then produced after conduct-ing three static simulated wind load strength tests, and nine LHL cyclic tests.
Conclusion
Steel Sheds and Garages in Cyclonic Regions
Span (mm)Strength Limit State
Capacity (kPa) - Cyclonic
1200 3.821100 4.081000 4.34900 5.07800 5.81700 6.54600 7.27
› 0.42 BMT Corrugated fixed to 0.75mm BMT purlin› 3 equal spans and greater than 3 spans› 6 fasteners per sheet @ 152mm ctrs› Hobson HEC Multi- Cyclonic Assembly, 14-10 x
53mm self-drilling carbon screw and 12-11 x 40mm› Hobson Vmax batten screws› Hobson 25mm diameter aluminium washer with
bonded EPDM seal
Domestic Dwellings in Cyclonic Regions
› 0.42 BMT Monoclad fixed to 1.5mm BMT purlin› 3 equal spans and greater than 3 spans › 5 fasteners per sheet @ 190mm ctrs› Hobson HEC Multi- Cyclonic Assembly, 14-10 x
53mm self-drilling carbon screw› Hobson 25mm diameter aluminium washer with
bonded EPDM seal
Span (mm)Strength Limit State
Capacity (kPa) - Cyclonic
900 4.96800 5.40750 5.62700 6.11600 7.08
Table 2: Low-High-Low Fatigue Loading Sequence
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With pressures for the proposed building determined, Engineers can use the span tables to specify the HEC Universal Multi-Seal Cyclone Assembly in accordance with design loads on sheds, garages or domestic dwell-ings in cyclonic regions throughout Australia. The span tables will provide valuable knowledge and information for the correct spans and number of assemblies required, and will assure our distributors that this product will per-form and can be sold with confidence. The HEC Multi-Cyclone Assembly will be arriving soon, stocked in plain and colorbond colours.
For further information please visit the Hobson website www.hobson.com.au or contact your representative.
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The principle of friction locking is based on in-creased friction in the thread or under the bolt head/nut. The main disadvantage of this method is increased torsion stress in the joint. High torsion may cause the fastener to yield at a lower preload than expected. Since friction conditions are un-even you may not reach the necessary preload. Insufficient preload is the most common cause of the bolt’s failure, often due to fatigue. Lubricants are often used to minimize friction and to obtain uniform clamp load. However lubrication will signif-icantly reduce or even discharge locking ability of any friction-based method. Friction-based locking results in little or no control over achieved clamp load.
The wedge-locking method is based on tension in-stead of friction. The most common example of the wedge-locking system is a pair of washers which have cams with a rise greater than the thread pitch of the bolt. The washer pair is installed cam face to cam face. When the bolt/nut is tightened teeth grip and lock the mating surfaces, allowing movement only across the cam faces. Any rotation of the bolt/nut is blocked by the wedge effect of the cams. The wedge locking ability is not affected by lubri-cation; furthermore by using it you can utilise each bolt to its full capacity. Nord-Lock wedge-locking products are recognised worldwide for their abil-ity to secure bolted joints exposed to severe vibra-tion and dynamic loads. The system cannot loosen unintentionally as it created a wedge underneath the bolt head/nut.
Why use wedge-locking instead of friction based locking?
For more information about Nord-Lock wedge-locking solutions, visit www.nordlock.com
"An Ideal solution for bolted joints where failure is not an option"
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Not that I frequent Redfern train station on a regular basis, but I found myself there on a recent “new experience” Saturday. As always, I have to check out the head markings of all the fasteners I see, but to my horror, I discovered that the lock-ing nuts (thin nuts) used to fasten an overhead steel structure had been installed incorrectly. As you would all know from Volume 24 of the Hobson Update, thin nuts should be installed BELOW the full size nut. The photos below show that only one set were installed correctly. There also appears to be some major installation issues where the foundations bolts have been severely deformed.
The Things You See!
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* The Hobson newsletter will now include a section on 'web Portal Tips'. We hope to cover some FAQ about our web portal and online ordering systems.
Live Order Status
WEB PORTAL TIPS:
All of your orders placed with Hobson will show in this screen - whether you placed them online or not! This allows you to: - Track the status of your order - See which Hobson warehouse your order is being despatched from - Email copies of invoices and test certificates to yourself - & more
On a live order W = Warehouse › NS2 Sydney, NSW › QB2 Brisbane, QLD› QT1 Townsville, QLD › VM1 Melbourne, VIC › WP3 Perth, WAOnce an order is shipped, W = Order Weight
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We celebrated Rebecca's 40th Birthday at the end of August. Rebecca started working at Hobson
when she was just 25!
Alan also had a birthday in August, and turned 30...he is clearly thrilled about this!
Hobson's Townsville Branch opened its doors
A Pizza Truck in the warehouse for Melbourne Cup lunch
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Hobson On Location
As 2015 comes to an end, we would like to take the opportunity to thank you, our valued customers, for your support again this year. From all of us at Hobson, we wish you a Merry Christmas and a very happy and prosperous New Year!
“Year’s end is neither an end nor a beginning but a going on, with all the wisdom that experience can instill in us. Cheers to a new year and another chance for us to get it right.” — Oprah Winfrey
We will be closed from the 23rd December 2015 to the 11th January 2016. Our online web portal will be available for you to use, and web orders will commence shipping from the 4th January 2016.
Merry Christmas
