Aspect II

The joining and fixing of metal composite panels is critical to their performance in use. Additional stiffness can often be achieved by the incorporation of UPVC edge profiles, which also act as joint formers to achieve more complex jointing and fixings and to allow interchangeability with other components, such as doors, windows and louvres.

The search for an improved four-way crossover junction without the use of ladder gaskets (as used for the Sainsbury Arts Centre, University of East Anglia and Gatwick North Piers), and the need to avoid the use of site-applied sealants, were fundamental design aims in the design of the new cladding system, Aspect

6.37 Interchangeable facade panels.

6.37 Interchangeable facade panels.

II, developed by Brookes Stacey Randall Fursdon, and now manufactured and marketed by Coseley Panel Products (Fig. 6.37).

This system of Interchangeable facade components offers the opportunity of rearranging or adapting the building envelope at any stage during the construction process or after the building is occupied. Aspect II allows panels to be interchanged with glazed panels, louvres or doors. Even loading bay doors can be relocated. For a full description of the development of the system, see Anon (I 990).

Aspect II achieves the freedom of movement of the components of the building envelope as suggested by the architects of the Hertfordshire Schools Programme in I 948: 'the freedom of movement of a queen on a chessboard as opposed to the limitations of a pawn' (Fig. 6.38). Modular coordination is essential to make this possible.

The method of fixing panels is to fix via an aluminium clamping plate located within the UPVC edge profiles and behind the primary gaskets. The clamping plates are secured with a stainless steel countersunk socket-head machine screw to a rear fixing block, which slides within the vertical rear

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6.38 Hertfordshire chess diagram.

aluminium carrier. The Aspect II system is entirely secretly fixed, and avoids any problems of aligning fixings, sealing fixings or panel damage by fixings.

The panels can be easily assembled or dismantled by a skilled fixing team. The clamping plate has been carefully engineered with allowance for thermal movement, rotational effects and tolerance. The interface of the clamping plate and the UPVC edge section has been designed to minimize thermal bowing of the panel.The number of clamping plates is dependent upon the wind loading and panel size.

In Aspect II the weatherseal is formed by the primary gasket framing the perimeter of the panel.The inner seal is formed by a horizontal airseal mounted to the top and bottom edges of the panel. This is clamped against the vertical airseal mounted to the rear aluminium carrier A still air zone exists between the primary gaskets and the airseal. Drainage continuity is maintained using sealed joints in the rear carrier; normally at 4 m centres, which allow for thermal

6.39 Panels face fixed using Allen key, then tightened to a specific torque.

i.40 Sequence of erection.

expansion.The sill detail is designed to drain moisture from within the assembly to the outside.

All components, including windows, louvres and doors, have a common method of jointing, and are secretly fixed.This achieves a system of coordinated components, through their means of jointing, resulting in a coherent assembly of diverse elements.Throughout these elements the finish can be common or highly varied depending on the needs of each project and the requirements of the specifying architect.

6.41 Plan of joint.

The sequence of assembly starts with the aluminium rear carriers, which are fixed back onto the building's substructure and aligned, plumbed and shimmed to a flat plane.The fixings and shims will be determined by the nature and tolerance of the substructure of each project.The vertical airseals are rolled into the locating channels in the front face of the carriers. These airseals run continuously up the elevation, and initially are oversized to allow for shrinkage (Fig. 6.40).

INSIDE

6.42 Section through horizontal joint.

Aspect II 143

The first panel, complete with its horizontal airseal and primary framed gasket, is offered up to the carrier and restrained by bolting down the aluminium cladding plate onto the aluminium rear block within the carrier. The clamping plate is then partially backed off and the adjacent panel offered up to the carrierThe joint between the panels is compressed to 15 mm (Fig. 6.41).The panel alignment is checked. The action of tightening the clamping plates' socket-head machine screws compresses the panel and the horizontal airseals against the vertical airseals. It is good practice to assemble a bay of panels vertically.

What seems to be required of the structure is something analogous to the freedom of movement of a queen on a chessboard as opposed to the limitations of a pawn.

The weatherseal of the horizontal panel-to-panel joint is formed by the primary framed gaskets, backed up by the panel-mounted horizontal airseals. There is no requirement for horizontal rear carriers or subframes (Fig. 6.42).

To minimize thermal migration, the rear clamping block of the clamp plate assembly has an extended nose section. This ensures that panels are retained

SECTION

6.43 Horizontal wind stiffener

6.44 Quality control during production.

within the gridlines of the panel modules.The assembly is restrained vertically by stop blocks, which are located in every third horizontal panel joint and carry dead load.

In order to extend the spanning capabilities of the louvre and window sections, increasing the maximum performance to 3.6 m clear span at 1.6 kN/m2 wind loading, horizontal wind stiffeners have been designed (and patented) by Brookes Stacey Randall Fursdon. An example of one of the more unusual designs shown (Fig. 6.43) comprises two aluminium extrusions. One forms the beam, which is profiled and has holes cut in the web. Depending upon the structural performance required, these holes can change in diameter and shape.The second extrusion forms discrete 60 mm wide brackets fixed into the panel joint at typically 900 mm centres. These two extrusions are linked by 6 mm diameter stainless steel struts.

The composite construction of Aspect II can use various core insulation materials to achieve U values of 0.45-0.35 W/m2oC.

The Aspect II system of panels and its associated components were produced after a design, research and development programme of mock-ups, prototypes and testing. The panel-to-panel joint, with its patented framed gaskets, has been tested at BSI according to BS 5368 Parts 1-3 for air penetration, weather resistance and wind loading.

Quality control during production and on site is important to ensure the panel's performance in use (Fig. 6.44).

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