The design of concrete monolithic stairs consists in choosing the location of the stairs in the volume-planning structure of the building and in the calculation of its structural elements. Choosing a place for stairs in individual residential buildings or apartments and in the interior of public spaces requires special attention. For example, choosing a place for stairs depends, first of all, on the plan of the house or apartment. Usually, the premises of the entrance group (hallway, vestibule, hall) are located on the first floor. Therefore, it is logical to provide the entrance to the stairs from these premises. You can connect the question of the location of the stairs with the location, for example, of the bathroom and toilet in the house. If the bathroom is on the second floor, it is better to have the stairs in the hallway - this brings the bathroom closer to the entrance. If the toilet is provided only on the first floor, then the stairs should be located in the room from which the entrance to it is provided. The device of a staircase in a common room, although widely practiced, is inconvenient in everyday life, since the room becomes a passage, that is, the question of choosing the location of the stairs requires a serious analysis of the structure of the interconnections of the premises, and only then the question of calculating and designing the stairs arises. In any case, it is important to consider the following conditions: - the stairs or stairwell must be as close as possible to the entrance to the house; - stairs should occupy a minimum of usable space of the room; - the passage from the entrance to the stairs or stairwell should be shifted to one of the walls of the room, and not cross it in the middle or diagonally; - the stairs must face the entrance to the room in which it is located, if not all, then certainly the first few; - the stairs leading to the basement should be as close as possible to both the main stairs of the house and the entrance to the house. In order to properly design stairs, it is necessary not only to choose their location correctly, but also to know the standards for designing stairs, which are set out in the relevant sections of the DBN. The following are the main norms, rules and requirements that should be followed during the design and construction of concrete stairs. The width of the marches and platforms determines the capacity of the stairs.The width of a separate march is determined depending on the requirements of fire safety (evacuation) and the estimated dimensions of portable items. Minimum march width: for internal stairs - 800 mm, for 2-story buildings - 900 mm, for residential buildings with more floors - 1050 mm, for public buildings - 1350 mm. Maximum march width: for residential buildings - 1400 mm, for public - 2400 mm. The width of the landings should be at least the width of the march and not less than 1200 mm. The usable width of the march of the turning stairs and stairs connecting more than two floors must be calculated for the simultaneous passage of at least two people, that is, it should be at least 1.0 m. In addition, with a useful width of the march of less than 1.0 m, it becomes difficult to transfer large items. The width of the steps of two- and multi-step stairs should be the same along the entire length of the stairs. There should be a gap of at least 50 mm between flights of stairs located in opposite directions. The number of steps in one march should be no less than 3 and no more than 16. · With a smaller number of steps, it is easy to stumble, with more - stairs " tiring " and in this case, it is necessary to arrange an intermediate site. The number of steps in the march should be odd, as it is more convenient for a person to start and finish the movement on the stairs with one foot - left or right. · The slope of the stairs is within 1: 2-1: 1.75 (20 ° - 26 ° 7'). The limit slopes of stairs intended for walking have an upper limit of 1: 0.85 (50 °) and a lower limit of 1: 2,75 (20 °). · Dimensions of stairs in residential and public buildings: " N " - no more than 19 cm, " In " - at least 26 cm. For internal stairs, 20 and 23 cm, respectively. For basement and attic stairs - 21 and 21 cm. The height of the steps within one march should not differ by more than 5 mm, which ensures a uniform slope throughout the march, and should be no more than 200 and no less than 120 mm. The width of the tread of the main stairs should be at least 250 mm. For stairs leading to non-residential premises, the height and width of the steps may be 200 mm. With a tread width of up to 260 mm, the value of its protrusion above the lower step should not exceed 30 mm. Running (wedge-shaped) steps on the inner border of the usable width must have a tread width of at least 100 mm, and on the middle line of the march - at least 260 mm. The radius of curvature of the middle line of the march with running steps should be at least 30 cm. The useful width of the landings should be at least the useful width of the marches adjacent to it. The length of the landings between flights should be at least 2 times the length of the average step of an adult, i.e. 1.3-1.4 m. The length of the landings near the entrance door should be at least 1.0 m if the doors are sliding or open in the opposite direction from the stairs. The length and width of the landings in front of the doors that open towards the stairs are calculated taking into account the width of the door leaf and the safe position of the person in the door at the time of its opening. The height of the fences (handrails) of interfloor stairs should be at least 0.9 m, for stairs over 12 m high - 1.1 m. For stairs used by children, the height of fences is recommended to be 1.5 m. The height of the fence of the external entrance stairs when climbing 3 or more steps should be at least 0.8 m. Stairs with more than 5 steps, with a march width of up to 1.25 m, are equipped with a handrail on one side, with a march width of 1.25 to 2.5 m, handrails must be on both sides. Stairways with a width of more than 2.5 m must be equipped with additional handrails in the middle of the flight. The absence of fences is allowed only for stairs consisting of 5 steps or less. The distance between the posts (balusters) of the railing should not exceed 12 cm at a height from the floor level of more than 1.5 m. The distance between any step of the stairs and the ceiling should be at least 2.0 m, so that an adult can walk freely on the stairs. Concrete the stairs should be well lit, especially the first and last steps of the marches. In conclusion, some preliminary approximate dimensions of the stairs are given. The necessary area for the construction of stairs (in horizontal projection) is approximately: - spiral stairs with a central post - not less than 3.6 m; - stairs with a platform - 3.1 m; - stairs with two turns at 90 ° - 2.1 m; - straight single-step stairs - 2.5-3.0 m. Standard two-step stairs made of industrial large-element reinforced concrete structures (staircase) have optimal dimensions of 3.0 x 6.0 m in plan. Sizes of openings in interfloor ceilings: - for straight single-step stairs - 1.0 x 2.5 m; - for spiral stairs with a central rack - 1.7-2.2 m in diameter; - for stairs with a turn of 180 ° - 2.1-2.5 m.
