Open web (Ratcliff truss):
Q1.1 Why hasn‘t it been thought of before?
A1.1 It may have been considered, but never explored as there were several barriers that would throw any trained person off. Uplift especially and seemingly more pieces so more labour costs. We have proven that it is viable at 14 metres onwards.
Q1.2 The bottom chord would have to be a compression member to overcome uplift, wouldn‘t it?
A1.2 No, when transverse deflection is controlled, uplift is no longer a problem as there is minimal deflection, which is the reason a bottom chord compression member is needed normally.
Q1.3 Will you need more cables to control uplift?
A1.3 No, when transverse deflection is controlled, uplift is no longer a problem as there is minimal deflection, which is the reason a bottom chord compression member is needed normally.
Q1.4 It won‘t make any difference having a third chord and diagonals, will it?
A1.4 This is the key to controlling deflection. The diagonal members of a truss are what controls transverse deflection and by having more diagonals transverse deflection is under control)
Q1.5 It will be too rigid, won‘t it?
A1.5 Having a bridge or tall building fully rigid, in the event of an earthquake, would be dangerous as anything not tied down would be thrown around. The designs can be adjusted so that there is suitable movement for such seismic events. Any sudden ground movement will transfer throughout the structure and peter out towards the centre of the span or height, much like when a high car aerial flutters in the wind and the top of the aerial is stationary.
Q1.6 How will you tension the webbing in shop?
A1.6 All members are predetermined length to allow for tension when the truss is jacked in shop. With each member added, the jacks are released slightly so the tension of previous members increases.
Q1.7 How will you erect it on site?
A1.7 The truss is in sections which are prefabricated. The first section is attached to an abutment, and then each consecutive section is attached as span increases, until it reaches the other abutment.
Q1.8 What connection method would you use?
A1.8 Double (sandwich) plates would be used and the members would be bolted through the plates and through the members. Normally, with a two chord system there is a lot of movement compared to ours, which puts a lot of strain on the joints. There is minimal movement on the joints with this system.
Q1.9 Too many parts. Highly labour intensive, isn‘t it?
A1.9 Labour and material cost reduces dramatically after 14 metres. You would not need the system under 14 metres as transverse deflection is not such a big problem unless heavier than normal loads are needed for a structure.
Q1.10 It looks too complicated.
A1.10 At first sighting it may look complicated, but becomes more simplified as it is better understood.
Q1.11 Fatigue is the biggest problem isn‘t it?
A1.11 Less movement means less fatigue.
Q1.12 Heat is the biggest problem, isn‘t it?
A1.12 Heat will be less of a problem as there is less movement in the structure and it will expand and contract evenly. All members are in equilibrium and will work together.
Closed web (ULB):
Q2.1 Is there too much steel in the section?
A2.1 Same amount of steel up to 20 metres and then reduces dramatically as the span increases.
Q2.2 Are the sections not doing enough structurally.
A2.2 The section is the maximum strength you can get out of any material. Built-in web tensioning being a big feature of the beam, which will eliminate initial deflection experienced when loading as the beam web is already in tension.
Q2.3 Is it complicated to fabricate.
A2.3 Easy to fabricate. The beam can be fully automated using continuous rolled C sections and robotic riveters etc.
Q2.4 Do you need to have it physically tested?
A2.4 Of course. This is obviously the best you can get as physical testing will prove. It is a full understanding of how trusses work and what is needed and where.
Q2.5 Is C sections/Warren truss the ideal beam configuration?
A2.5 The Warren truss system is only a two chord system, which suffers with transverse deflection and buckling.
Double skin freestanding column:
Q3.1 How can it be automated?
A3.1 Individual lengths of tubing can be used, where the smaller inner tubes would be staggered so that there are no straight joins. The tubes can also be further strengthened by adding an inner sleeve to the joins, but deemed unnecessary as they would be boxed in from either side tubes.
Q3.2 Could you use steel?
A3.2 You could, but it would be difficult to weld the tubes together.
Q3.3 Where could it be used?
A3.3 A very wide variety of applications subject to a technical review.