Designing of ladders consists in a choice of a site of a staircase or a ladder in space-planning structure of a building and in calculation of its constructive elements. The special attention is demanded by a choice of a place for a ladder in individual apartment houses or apartments and in an interior of premises of public appointment. For example, a choice of a place for a ladder depends first of all, from the house or apartment plan Usually premises of entrance group (the vestibule, a lobby, a hall) take place on the ground floor. Therefore the input on a ladder is logical for providing from these premises. It is possible to co-ordinate a question on position of a ladder to a site, for example, a bathroom and a toilet in the house. If the bathroom is on the second floor, the ladder is better for having in a hall is approaches a bathroom to an input. If the toilet is provided only on the ground floor the ladder should be in that premise from which the input in it is supposed. The ladder device in the general room though and widely practises, is inconvenient in a life as the room becomes a checkpoint, i.e. the question of a choice of a site of a ladder demands the serious analysis of structure of interrelations of premises, and already then there is a question of calculation and ladder designing. Anyway it is important to consider following conditions: - the ladder or a staircase should be as much as possible approached to an input in the house; - the ladder should occupy a minimum of useful space of a premise; - pass from an input to a ladder or a staircase should be displaced to one of premise walls, instead of cross it in the middle or on a diagonal; - the ladder should be turned steps to an input into a premise in which is, if not everything it is indispensable several first; - the ladder conducting in a cellar, should be as much as possible approached both to the basic ladder of the house, and to an input in the house. That it is correct запроектировать a ladder, it is necessary not only to choose correctly its site, but also the nobility of norm of designing of the ladders, stated in corresponding heads СНиП. Further the basic norms, rules and requirements which should be observed at designing and building of ladders are resulted. · the width of marches and platforms defines throughput of a ladder. The width of a separate march is appointed depending on requirements of fire safety (evacuation) and prospective dimensions of transferable things. The minimum width of a march: for intraroom ladders - 800 mm, for 2-storeyed buildings - 900 mm, for residential buildings большей этажности - 1050 mm, for public buildings - 1350 mm. The maximum width of a march: for residential buildings - 1400 mm, for public - 2400 mm. · the width of ladder platforms should be not less than width of a march and not less than 1200 mm. · the Useful width of a march of a rotary ladder and a ladder connecting more of two floors, should be calculated on simultaneous pass not less than two persons, i.e. make not less than 1,0 m. Besides, at useful width of a march less than 1,0 m carrying over of large-sized things is at a loss. · the width of marches of two- and multimid-flight ladders should be identical on all extent of a ladder. · between the flights of stairs located in the passer to each other a direction, there should be a backlash not less than 50 mm. · the quantity of steps in one march should be not less than 3 and no more 16. ·При smaller number of steps it is easy to stumble, at большем - the ladder becomes "tired" and in this case it is required to arrange an intermediate platform. · the number of steps in a march is desirable for providing odd as it is more convenient to person to begin and finish movement on a ladder one foot - left or right. ·· the recommended bias of a ladder is in limits 1:2-1:1,75 (20 ° - 26°7 '). Limiting biases of the ladders intended for walking, have the top border 1:0,85 (50 °) and the bottom border 1:2,75 (20 °). ·· the Sizes of steps of ladders in inhabited and public buildings:" Н "- no more than 19 sm,"In"- not less than 26 see For intraroom ladders accordingly 20 and 23 see For basement and garret ladders - 21 and 21см. ·Высота steps within one march should not differ more than on 5 mm that provides a uniform bias on all march, and there should be no more than 200 and not less 120 mm. The width of a step of the basic ladders should be not less than 250 mm. For the ladders conducting in uninhabited premises, the height and width of steps can be 200 mm. At width of a step to 260 mm size of its ledge over an underlaying step (the size"with"on fig. 4) should not exceed 30 mm. Забежные (клиновидные) steps on internal border of useful width should have проступь in the width not less than 100 mm, and on an average line of a march - not less than 260 mm. The radius of curvature of an average line of a march with забежными steps should be not less than 30 the Useful width of ladder platforms see should be not less useful width of marches adjoining it. The length of the ladder platforms which are between marches, should be not less than 2 sizes of length of an average step of the adult person, i.e. not less than 1,3-1,4 m. the Length of ladder platforms at entrance doors should be not less than 1,0 m in the event that the door sliding or opens in the opposite party from a ladder. The length and width of ladder platforms before the doors opening towards a ladder, pays off with the account of width of a door cloth and safe position of the person at a door at the moment of its opening. · the height of protections (handrail) of interfloor ladders should be not less than 0,9 m, for ladders in height more than 12 m - 1,1 m. · For the ladders used by children, the height of protections is recommended 1,5 m. · Height of a protection of external entrance ladders at lifting on 3 and more steps there should be not less than 0,8 m. · the Ladders having more of 5 steps, at width of a march to 1,25 m are equipped with a hand-rail on the one hand, at width of a march from 1,25 to 2,5 m hand-rail should be from two parties. More than 2,5 m it is necessary to equip ladder marches in width with an additional handrail in the middle of a march. · absence of protections is supposed only for the ladders consisting of 5 steps and less. · the Distance between racks (балясинами) a handrail should not exceed 12 sm at height from level of a floor over 1,5 m. · Distance between any step of a ladder and a ceiling there should be not less than 2,0 m that on a ladder there could pass freely the adult person. · ladders should be well shined, especially the first and last steps of marches. ·В the conclusion some preliminary rough dimensions of ladders are resulted. The necessary area for a ladder construction (in a horizontal projection) makes roughly: - a spiral staircase with the central rack - not less than 3,6 m; - a ladder with a platform - 3,1 m; - A ladder with two turns on 90 ° - 2,1 m; - a direct one-mid-flight ladder - 2,5-3,0 m. the Standard two-mid-flight ladder from industrial крупноэлементных ferro-concrete designs (staircase) has in the plan the optimum sizes 3,0 х 6,0 m. the Sizes of apertures in interfloor overlappings: - for direct one-mid-flight ladders - 1,0 х 2,5 m; - for spiral staircases with the central rack - diameter 1,7-2,2 m; - for ladders with turn on 180 ° - 2,1-2,5 m.
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