Using 3D laser scanning to improve the reliability of

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Proceedings 19th Triennial Congress of the IEA Melbourne 9 14 August 2015. Rise vertical distance between the horizontal upper surfaces of two consecutive treads or between a. tread and a floor or a tread and a landing, Going horizontal distance between two consecutive nosings measured along the walking line. Walking line notional line that indicates the average path of users of a stair. Nosing front edge portion of a tread or landing usually projecting beyond the riser. Table 1 Rise and going dimensions mm Australia BCA England AD K and BS 5395 1 and Singapore Building. and Construction Authority Approved Document Acceptable Solutions V6 0. Building Code Rise Going Tolerance,Min Max Min Max Rise Going. BCA public 115 190 250 355 Constant Constant,BCA private 115 190 240 355 Constant Constant. AD K general access 150 170 250 400,AD K private 150 220 220 300. BS 5395 1 normal use 150 180 300 450 1 0 1 5,BS 5395 1 private 150 200 250 400 1 0 1 0.
Singapore Public building 175 275 5 mm 5 mm,Singapore Residential unit 175 225 5 mm 5 mm. Singapore Industrial building 175 250 5 mm 5 mm, The normal relationship between the dimensions the rise and going twice the rise plus the going should be between. 550 mm and 700 mm, The maximum pitch for is 42 hence maximum rise cannot be used with minimum going. This is often interpreted as 5 mm the rise and going tolerance that is used in the New Zealand Building Code and. AS 1657 Fixed platforms walkways stairways and ladders Design construction and installation The tolerance in the. Guide to the BCA was also 5 mm until it was withdrawn without explanation at the end of 2000. A tolerance of 5mm between two consecutive steps in any flight of staircase is acceptable. The values provided in the documents are expected to be achieved for every stair built under the. respective codes In order to comply with these guidance documents the stairs must therefore be measured. to determine whether they meet the criteria or not Anyone measuring these dimensions would need to. consider both whether they fall within the acceptable values described in each document and whether they. vary from step to step Inappropriate dimensions and variance between steps have been shown to be. leading causes of non compliance and lead to the greatest risk of harm Some degree of variation is. expected any consequent risks have only been partially determined. Roys and Wright 2003 developed an algorithm for assessing the risk of a large overstep 50 of an. average male shod foot occurring in descent It is based on experimental variance of foot placement on an. adjustable stair rig The assumption again seen in experimental research is that the risk of this overstep. leading to a slipping event is directly linked to the size of the overstep The difference in relative risk is shown. in Figure 1 where the risk of a large overstep on a 14 step stair having a going of 300 mm and zero variance. between steps is given a value of 1 Decreasing the going dimension by 25 mm has two orders of magnitude. effect on the risk and this risk is increased by another order of magnitude for a decrease of 50 mm Similarly. by decreasing the length of one going by a small amount 5 mm 10 mm or 15 mm the risk is again. significantly increased The values in the bubbles are based on the same comparison but this time it is. considered in terms of time between events occurring If a typical family were to use the stairs at home. estimated to be equivalent to 18 descents a day with a 300 mm going and no variation between steps such. an event would be once in 8000 years longer than the life expectancy of most buildings Reducing the going. to 225 mm similar to current private stair minimums and with no variation between steps results in an. overstepping event occurring every year A slight variation in one step could cause an overstep event every. 3 months whereas if the going was set to 275 mm the risk would be once every 40 years It is clear from this. analysis that the dimensions in particular the going dimension and variance in this dimension are critical. risk factors relating to injury on stairs, Proceedings 19th Triennial Congress of the IEA Melbourne 9 14 August 2015. Figure 1 Increased risk of a large overhang 50 of shoe relative to 300 mm going with no variation which is about. once in 8000 years for typical family domestic stairs. 2 Who needs to make these measurements, While it is clear that measurement is required it is rare that such measurements are taken This is partly.
because the dimensions are very difficult to measure with any accuracy and also because many do not. consider the stairs to be contributing to the potential risk of harm In our opinion there are potentially four. sets of people who as part of their job should be considering measuring stairs building control. environmental health occupational health and forensic examiners Each group has different requirements. from these stair measurements and hence require different levels of accuracy. 2 1 Building control, Building control officers are responsible for confirming that a building is built according to the requirements. laid out in the various guidance documents The first part of this would be to ensure the plans are within. specification Stair measurements on plan are easily resolved through the CAD software and hence it will be. obvious quite quickly if the stair does not fall within the guideline recommendations Building control officers. will also make one or more inspections of the property as it is being built to ensure elements are being. introduced as specified on the plans One of these inspections is likely to include a site assessment of the. 2 2 Environmental Health, Environmental health officers are responsible for ensuring the buildings are fit for purpose once in use This. assessment can take many forms but in England this includes and assessment of the potential for risk from. a number of hazards determined under the Housing Health and Safety Rating Scheme HHSRS One of the. more serious hazards present in 9 of the housing stock is the risk of falls on or from stairs The risk. assessment will include any flights of steps whether internal to the building part of the circulation route to. access the dwelling or external steps associated with the dwelling They will be aware of the risks. associated with inadequate step dimensions and inter step variability and will want to include an. assessment of these factors when making an assessment. Proceedings 19th Triennial Congress of the IEA Melbourne 9 14 August 2015. 2 3 Occupational Health, Occupational health officers are amongst other things responsible for ensuring a home is suitable for. people to return to after injury or a stay in hospital Often their clients will be elderly or children with. disabilities Stairs can be a limiting factor for many of these clients restricting access to just the entrance. floor of the property In some cases the stairs require a handrail or better lighting to make them usable but in. other cases the stairs are so restrictive that alternative sleeping and hygiene requirements are needed on. the entrance level if the home is to remain usable They may be aware of the risks involved with the stair. and would benefit from being able to make quick and simple measurements to assess the potential risk from. the stairs for some cases,2 4 Forensic examiners, Forensic examiners are usually only called in to examine a stair after a fall has occurred In some of these. cases the fall could be fatal The examiner needs to consider every aspect of the stair in order to determine. where the risk of harm exists what part of this risk is inherent in the stair and whether the stair is built to the. specifications expected or perhaps altered in some way which could potentially increase the risk of harm As. with most investigations other aspects of the environment as well as human factors could be involved in. the hazardous event occurring So while a very important part of the investigation the stair dimensions are. just one aspect to be considered,3 How should these measurements be taken.
Listed below are a number of measurement techniques with increasing complexity. 3 1 Visual inspection, A lot can be assessed by a simple inspection of the stairs When approaching the flight consider whether the. passage is clear both on the steps and at the landings Pay special attention to anything that a user could. land upon if a fall were to occur or things that might restrict movement increasing the potential for a fall to. initiate Consider the step finish is it bare timber concrete tiles a resilient covering or carpet Check also. for the presence and suitability of handrails whether there is sufficient headroom over the whole flight and. whether the sides of the steps and landing are protected to stop people falling from height Requirements in. both England and Australia highlight how gaps in between open steps and barrier components although the. maximum size in Australia is 125 mm and in England it is 100 mm. Consider the lighting on the stair both the ability to artificially light the steps and any lighting from. natural sources Check for glare and potential shadows that might hide where the step edges are This is. often difficult to assess at a single point in time and hence some judgment of how the various lighting. options might affect the appearance of the steps in use is needed If there is any doubt it may be worth. checking the stair at a different time of day or under different weather conditions For some steps especially. those in public buildings and on access routes for transport or streetscapes the nosings should be clearly. marked by the addition of contrasting strips, The final visual check will be to consider the steps themselves for and movement or imperfections. which could be a hazard Where the step covering is worn or damaged or where the steps themselves are. damaged this should be noted By walking the flight any movement in the steps may be noticeable as might. any strange noises which might suggest movement,3 2 Crouch and sight test. This 10 second test is a very valuable quick assessment for between step variations If all the step rise and. going dimensions are equal throughout the flight then it should be possible to visually line up all the nosings. by simply crouching down at the top landing and eyeing up the nosings Where there is variation between. steps that are big enough to be a problem it will be impossible to line up all the nosings visually Instead one. or more steps will appear to hide behind other steps as you visually move your line of sight up and down. Other steps may stand out from their neighbours making it impossible to line them up with higher steps. Often in England the rise on the top step is higher than others making it impossible to see if the other steps. line up The bottom step may also have a lower rise than the others again this would not be visible using the. Proceedings 19th Triennial Congress of the IEA Melbourne 9 14 August 2015. crouch and sight test For any other variation the method gives a very quick check to see large differences. Figure 2 illustrates how this might occur, Figure 2 Lining up nosings using a crouch and sight test. 3 3 Simple measurement, Measuring the rise and going directly in situ is very difficult Measurements are between two similar points on.
consecutive steps which is usually the front face of the nosing for going and the top face of the nosing for. rise If the stair is well built with level equal steps then a quick measurement can be meaningful however. often the step nosings are not square with each other the treads slope or for existing stairs the treads may. be bowed or worn This makes it difficult to know where the measurement should be taken Measuring going. can be even harder since the nosing often overlaps the tread below A measurement on the tread of the. tread depth front of nosing to the back of the tread or to the riser is larger than the going by the size of this. overlap All measurements should also be taken along the walking line and perpendicular to the surfaces. With all this in mind a simple measurement can be made to give an indication of whether the steps are the. right size and whether they vary step to step Measurements can be taken with a marked stick a piece of. card a metal rule or even a user s foot Measurements taken at the edge of the step are easier to make. consistent step to step at the side string or edge of the step can be used to square up the measurements. however in many cases a value either in the centre of the step if the stair is less than 1 m wide or 270 mm. in from the edge of the step would be the most useful as these are the expected walking lines Using a card. like the one shown in Figure 3 enables a quick comparison against expected values and with a marker the. variance between steps can quickly be recorded If using a ruler or stick then again recording the position of. the nosing along the stick when pushed up against the riser for going or on the tread for the rise should. show adequacy and variance Remember to consider the overlap in going measurements If you don t have. anything to make measurements with it is possible to get a very rough estimate using your own leg Place. your foot onto the tread with your heel as far back as possible you will possibly feel the nosing of the step. above pressing against your calf and try to make your foot point d. British Standard BS 5395 1 2010 In Australia the National Construction Code also known as the Building Code of Australia BCA establishes the requirements There are a number of aspects of stairs that are controlled within these guides two of the dimensions controlled are rise and going These are defined below

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