THE WINSTEP CONCEPT. The challenge

Transcription

1 W I N T E C WiNstep THE WINSTEP CONCEPT The challenge 1 Staircases present many on-site problems for the builder. Floor-to-floor heights vary as do riser and tread dimensions. Typically, skilled carpenters set out and build the shuttering with extensive propping and specially designed reinforcing being required before the concrete is poured. Not only is space needed for storing reinforcing and shuttering material but concrete spills resulting from bleeding and kicking shuttering and careless barrowhandling add to the general mess and congestion in the very place where easy access to upper floors would enhance efficiency and project completion. All this effort per force takes time. The solution Winstep* addresses all these problems effectively, bringing to the site, precast concrete components - stringer beams and treads - that are simply assembled and require no further finishing except paint, carpet or floor tiles. The same range of Winstep* components may be used to create concrete walkways ramps, access walkways, elevated cat-walks and bridges and many other similar structures. Winstep* is suitable for internal and external use in the industrial, commercial, recreational and domestic environments. Geometry Precast concrete treads with radiused undersides are glued into matching scalloped stringer beams. The pitch of the scallops is constant (Fig.1). As the stringer beams are raked to the required angle, the treads are rotated in the scallops to their level position and glued in place. The riser heights and the tread lengths thus vary to accommodate the rake, and maintain the geometry of good stair design (Fig. 2). A special adhesive has been selected to bond the concrete components together. For comfortable stairs, the formula 2 x RISER + TREAD = 600 to 650mm: is used (Neufert). Applying this formula to the steepest stair allowed by the National Building Regulations (Fig. 2) i.e. RISER 200mm, TREAD 250mm, we get (2 x 200) = 650mm. By Pythagoras, the diagonal distance from nose to nose is 320mm. Wintec chose 320mm as the pitch for the scallops on the stringer beams with 310mm wide treads resulting in a 10mm gap between the treads when the beam is horizontal (Fig. 3). The required minimum overlap of 25mm for treads is maintained even when the rake decreases to 27 (147mm riser) (Fig. 4). Because the treads may be fixed parallel to the beams the assembly may used to create walkways and inclined planes (Fig. 5). Cost Implications The Winstep* system is cost effective. The high cost of shuttering is eliminated. Winstep* elements are precast and prestressed with lighter concrete sections. Together with simple on-site erection procedures see (page 9) the innovative Winstep* system results in savings of up to 30% over conventional in-situ concrete staircases. A comprehensive costing comparison prepared by independent quantity surveyors is available on request. Savings in construction time and availability for use of the stairway is awesome.

2 1. PRODUCT APPLICATION 2 CAP 2 CAP 2 CAP 2 CAP 2

3 2. STANDARD PRODUCT RANGE 3 TR 1 is a designed for stairs with closed risers. The tread is supplied as a standard product with a riser height of 170mm or 190mm. Risers may be trimmed back with an angle grinder for lower riser heights. The struck face is wood floated to receive another finish (carpet, wood veneer, ceramic or our concrete coloured tiles) or simply left with the final non-slip finish supplied. Mass = 55kg/m. TR 2 is a designed as an open tread for use in open stairs or on walkways. The tread is supplied as a standard product. The step face is wood floated and roller finished to provide a non slip surface finish. Mass = 41,73kg / m.

4 3. STRUCTURAL DESIGN CONSIDERATIONS 4

5 4. STAIR DESIGN PRINCIPLES 5

6 4. STAIR DESIGN PRINCIPLES 6 See Site Instruction Diagrams for detailed dimensions compiled in all stair riser heights at 5mm increments

7 5. BUILDING WITH WINSTEP 7 HANDLING COMPONENTS NOTE: It is imperative that beams are carried and stacked in the upright position. The stringer beams are provided with 51 mm diameter holes to assist with onsite handling. Stout ropes or straps may be passed through these holes. Timber brandering of appropriate section and strength may be passed through the holes to provide rigid handles for manipulation of the beams (Fig. 1). PREPARING TOP AND BOTTOM FIXING DETAILS The particular top and bottom conditions of each stairway will vary depending on whether the building is still under construction or the stairway is being retro-fitted into an existing structure. SITE INSTRUCTION DIAGRAMS See set of diagrams for top and bottom landings for all angles of repose in 5mm riser height increments. This allows for stringer beams to be marked out top and bottom and cut to suit angle of repose. Available in hard copy or from the website. TOP LANDING PREPARATION In general the fixing at the top landing requires each beam to be fitted into a slot provided in the landing (Fig. 2). This may be prepared by angle grinding and chiselling in the case of an existing landing or, in the case of a new building, by preparing slots in the shuttering by using polystyrene foam blocks before casting the concrete landing. In both cases the slots should be oversize to allow for adjustment. A scaffold board may be used to simulate the position of the stringer beam. Note that landing slabs must be thick enough to secure beams in the slots with rebar correctly positioned in support. BOTTOM LANDING PREPARATION Fixing of the bottom landing may require chopping through an existing floor slab (Fig.3). In this case the fill under the slab should be excavated and the recess well compacted to receive a thickened, in-situ concrete pad, poured around the ends of the accurately positioned stringer beams. For new work the slab must be designed with slots shuttered in position to receive the stringer beam ends. SETTING BEAMS IN POSITION Mark off and cut all beam ends according to the appropriate site layout diagram. Use a tread or tread off-cut when supplied to set up stringers to level and tread height. Align beams with a 50mm pipe passed through in both beams. Beams must be positioned so that the first and last riser dimensions are equal. This will ensure constant riser heights throughout the stair set. The thickness of the finishes to be applied to the landings and treads must be allowed for in positioning the beams. If there are no applied finishes to the treads, then the lowest point of the arc of the top scallop must be 75mm below the top landing level (Fig. 4). Similarly the lowest point of the arc of the bottom scallop must be set above the floor by the total riser dimension less 75mm. If, for example, the total riser dimension was 200mm then this dimension would equal 125mm (200-75) (Fig. 5). Each beam in the same stairway-set should be aligned parallel to the others. In plan, no beam in a stairway-set should be placed forward or backward of another.

8 5. BUILDING WITH WINSTEP 8 support each tread if the stair is at a steep angle in place with few bricks thereon FIXING BALUSTRADE STANCHIONS TO TREADS (Where possible fix top and bottom stanchions into landings) 38mm O.D. tube, 2mm wall thickness (MIN) 80mm diameter. 5mm thick support plate welded to balustrade post standard 'winstep' open tread (APPROX.) M12 STUD THRU (MIN) 50 DIA H.D. Washer or Plate (See below) 75 ELEVATION NB: Hole must be on centre line of tread 38mm O.D. tube. 2mm wall thickness 80mm diameter. 6mm thick support plate welded to balustrade post 60 MIN 6x50x100mm steel support plate or 50% H.D. Washer PLAN Standard "winstep" open tread Instruction Note: Drilling with care 6mm pilot hole and then 13mm drill. Switch off percussion throughout last 15mm