Drawings of stairs

The

basic data on ladders, calculation of ladders and drawings of ladders.

The choice of type of an intraroom ladder depends on solidity and fire resistance of a building, character of prospective movement, presence of the free area and premise height. The ladder form choose depending on its appointment and a site, architectural registration of a premise and a construction as a whole.

Ladders for apartment or a country house

Ladders for apartment or a country house can be divided into straight lines (fig. 1,) or straight lines with intermediate platforms (fig. 1, 6); with turn in one quarter (fig. 1,); with a half-turn on 180 ° (fig. 1,) or with turn in three quarters (fig. 1,); twisting, oval, round (fig. 1, е,); screw (fig. 1,), ladders with забежными steps (fig. 1, и-л). By quantity of the marches separated by platforms, distinguish one-mid-flight, two-mid-flight and multimid-flight ladders. Depending on a direction of lifting of a flight of stairs happen right and left (a sign of the right ladders — lifting clockwise).

Calculation of ladders is made taking into account following requirements:

• the maximum convenience and reliability;

• the convenient safe approach both for lifting, and for descent;

• a convenient and safe arrangement of a handrail;

• conformity of width and height of steps to convenient length of a step and convenient lifting of a foot;

• good illumination.

Calculation of width of a ladder march

The width of a ladder march is defined from calculation by throughput of a ladder, i.e. quantity the person which can pass in its narrowest place within one minute (fig. 2).

Fig. 2. Width of a ladder march.

0,6-0,7 m. there are enough for pass of one person Width of intraroom ladder marches there should be not less than 0,9-1 m, in houses of the raised comfort — 1,25-1,5 m. In garden small houses are supposed width of a march 0,7-0,8м.

Calculation of a ladder of relative size of lifting

For calculation of the size of a ladder it is necessary to establish its place on the plan and floor height, to choose the scheme of a ladder and the sizes of steps. As a rule, the angle of lead of a ladder march makes from 20 ° to 50 °, ladders with an angle of lead from 30 ° to 45 ° (fig. 3) however are more convenient.

Fig. 3. The parity diagramme between the sizes of steps and a march angle of slope.

Convenience of operation of a ladder - height of steps

Convenience of operation of a ladder and the guarantee of safety connected with it depend mainly on relative size of lifting of a march (angle of lead). The march Angle of lead can be established graphically, knowing a ladder site in the plan and premise height (fig. 4).

Fig. 4. Calculation of an angle of lead of a ladder.

By practice it is established: the ladder is convenient and safe, if the doubled height подступенка. Combined with width of a step (проступью) equals to an average step of the person. The length of a step of the person on a plane makes about 62-64 sm, and convenient lifting of a foot of 30-32 sm (fig. 5).

Fig. 5. Convenient length of a step and foot lifting.

Proceeding from it, проступь and lifting define as follows:

2а+b=64 sm, (1)

Or

а+b=47 Sm, (2)

Where and — step height, b — width appear.

For example, if the height of a step of 12 sm, проступь makes 40 sm (without considering a ledge of edge of a step). Such decision gives too wide проступь. In such cases use the formula (2) on which width appear it is equal 35 see Practice it is established that ladders are most convenient for lifting with height of a step from 140 to 170 mm and in the width appear — from 340 to 370 mm. Thus, for definition of width appear at height of a step from 140 to 170 mm it is recommended to apply the first formula. The step height should be no more than 200 mm and not less 120 mm. The edge steps (ledge) should be an order of 20-40 mm (fig. 6).

Fig. 6. Types of steps.

The above the step, the already should be проступь, and on the contrary. The width of a step should be equal to its height, at least. The table of selection of steps for flat and abrupt ladders with reference to the most widespread heights of floors (the tab. see) can give the additional help.

Height of steps and their number for flat and abrupt ladders depending on floor height (number of steps/heights of steps, mm)

Average line of a march

The average line of a march is an imagined line which passes in rectilinear ladders in the middle of width of a march, and in curvilinear — on distance of 40-50 sm from flight edge (for spiral staircases — from a rack axis). Appear steps of a curvilinear march have клиновидную the form, and the narrow party appear there should be not less than 140 mm. It is necessary that the width of such step on an average line of a march was equal to width of steps of a direct march. Rising on a curvilinear ladder, the person deviates the central line more often, overcoming lifting by step of various size. To exclude inconveniences, design ladders with the dispersed steps with gradual change of their width on all length of a march.

Calculation of height of pass, critical point

Pass height in light — the minimum distance on a vertical between the top edge appear also the bottom edge (or the bottom party) вышерасположенного a constructive element — accept not less than 1900... 2000 mm. In process of lifting on a ladder this size should remain (fig. 7).

Fig. 7. Pass height over a ladder.