Certificate of Structural Adequacy – balustrade installation

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Description

Price:

as shown above (Minimum)

Description:

Assessment and certification of Structural Adequacy for balustrade installation. An installation comprises of one configuration and parameter set (Rail span, post height, load category, base connection): each variation to configuration and/or parameters defines a different installation. The assessment excludes the suitability of the existing support structure. {NB: Depending on the nature of the support structure, its suitability may require assessment of the structures normal loading in combination with the barrier loads. In general this means the person responsible for designing the building also needs to consider the loads imposed on the building by the proposed barrier. Tools are provided on this web site to assist with determining such loads.}

In general only rail type infill will be considered. For panel type infill materials, the material should be typically used for construction of walls and design charts should be available for assessing suitability.

Required Inputs:

  1. A properly documented technical specification for the balustrade system. {A system which is buried and otherwise hidden away inside some blackbox software is not acceptable. Balustrade manufacturers should ensure they have a properly documented technical specification for their system: unless wish us to produce such specification.}
  2. Detail drawings of the proposed installation. The installation includes the balustrade system, the structure it is being attached to, and the interface between the two.

Notes:

    1. AS1170 barrier loads: the infill loads are secondary, the top edge loads are the primary barrier load. For tall barriers, those with height more than 1100mm (upper functional height of a rail AS1675:1992), top edge loads are not appropriate, but nor are infill loads suitable for use as the primary load condition.
    2. Unlike AS1657:1992, the newer AS1657:2013 ignores maximum height for rail type barrier. If a rail barrier is too low, then a person will topple over. If a barrier is too high than a person can fold or buckle at any of their joints and fall under the barrier.
    3. A barrier 900mm high (AS1657:2013) is potentially unsafe, as 95th percentile centre of gravity is around 1000mm, and only a small force would be required to dislodge a persons footing and topple them over the barrier. Likewise a 1000mm barrier height (NCC/BCA) is also potentially too low, as just balanced. A barrier of 1100mm is a more preferable height, with appropriate infill below.
    4. Posts typically require 100mm to 150mm embedment when cast-in to a floor slab, whilst anchor bolts typically require a minimum  of 70mm to 100mm. Anchor bolts with shallower embedment maybe possible but more such bolts will be required: and such shallow embedments are not very robust.
    5. A cantilevered post develops a base moment, when fastened to a fascia beam, that moment will become a torsional moment relative to the axis of the fascia beam. Few structural elements have high torsional resistance, therefore the tradition in structural design is to avoid and otherwise remove torsional moments. To do so, posts are typically aligned with beams at right angles to the fascia (eg. joists, bearers). For footbridges U-frames can be used, for balconies L-Frames. Timber decking with joists over bearers can be a problem, as the two adjacent edges are different. In such cases it is preferable to take the main support posts up beyond the floor level and build the barrier between these posts. An alternative is a barrier constructed on top of the floor deck with a continuous base plate: such as stud wall like construction. An other alternative is to build a square grid, with the floor joists top edge flush with the bearer top edge: that is joists between the bearers. When designing a building structure the need for a barrier should be considered in the first instance and the structure designed to suit, or barrier selected to suit the building structure. The building structure and barrier type need to be compatible.
    6. Do not design a swimming pool fence solely to the swimming pool fence code, it only gives partial loading requirements. The swimming pool fence code only covers those requirements to make the fence tamper proof to children, it does not cover the loading of the fence as a barrier which obstructs movement of people, nor does it cover wind loading of the fence.  Select a suitable load category from AS1170 barrier loads. If suitable barrier loading category is selected, then wind loading is likely insignificant by comparison. Put another way, if wind load is critical, then it is disadvantageous to quote the barrier load for the barrier system, therefore pick a higher barrier load and design for the higher barrier load. If wind loading is higher than crowd loading of a barrier, then really need to give careful consideration to the application (eg. why is a crowd of people assembling in such a high wind load area?).
    7. The wind loading code AS1170.2 does not provide adequate coverage of wind buffeting and structural vibration which may be experienced by a cantilevered flat plate type barrier (eg. glass balustrade) installed to the edge of a multistorey building. The recommendation would be not to do it. If must install a barrier on roof top of tall building, then keep it back from the edge, at least twice its height, so that if wind loading does break the barrier, there is reduced chance of it falling to the ground below. Otherwise it is preferable to stick with substantial parapets (eg. at least 100mm thick), or rail barriers. Alternatively fully enclose the walk space for public access.
    8. If there is no requirement for a kick plate, and feet can protrude under a barrier, then consider that a permissible 100mm deflection (AS1657) of the barrier will result in the heal of the foot no longer supported on the floor. It is therefore suggested that the typical installed edge distance of 75mm to 100mm is not acceptable. Without anthropometric data, the recommendation would be to keep the inside face of the barrier at least 300mm from the edge of the floor, else provide a kick plate. If drainage is an issue, then consider is it any more appropriate that water should fall from the great height of the floor than any other object: such storm water drainage is not the equivalent of rain drops. In other words design suitable drainage system for the floor.
    9. Considerations for Panel type infill or Barriers where the panel is the primary structural restraint:
      • Glass Reference: AS 1288-2006 Glass in buildings – Selection and installation
        Section:7 Balustrades
        Table 7.3: Infill Balustrades
        May need to refer to section 4: Design for Wind Loading, if wind pressure greater than imposed pressure.
      • Plywood/Particle board/OSB: Span tables for floor loads, may be suitable.
      • Expanded Metals:  Seems only produce span tables for floors.
      • Profiled metal walling;  If supplier provides wind pressure tables, these may also be suitable for checking imposed pressures
      • CFC boards and planks: If supplier provides wind pressure tables, these may also be suitable for checking imposed pressures
      • No Capacity Tables Available:
        • Design as Single Span Beam
        • Use Plate Formula: AISC(now ASI)/DCT Volume 1 Open Sections : Part 11 Floor Plates
        • Use yield line theory
        • Use FEA/FEM
        • Use frame analysis software: approximate panel as a grid of flat bars
        • Test