Convince ordinary person sometimes it is not easy in the reliability of a cantilever ladder structure. In this case, the elegance of cantilever stairs works against them. However, for people who understand this is a great opportunity to demonstrate the possibilities of engineering and interior ergonomics.
Indeed, the cantilever staircase can be called the most spectacular among other interfloor stairs. Its steps "hover" in the air, and the structure itself does not take up much space and does not obscure the light.
Modern minimalist styles do not tolerate the waste of space that a concrete or traditional wooden stringer staircase unceremoniously takes away. Today, designers are faced with the task of creating light and transparent stairs. These include suspended, bolt, spinal and actually cantilever stairs. The last type of stairs is more suitable for fans of minimalism and hi-tech. There are no unnecessary details in such stairs. In fact, these are only the steps themselves, which are attached to a wall, pole or other supports with only one side. But stairs without railings are quite rare in practice. Rather, such stairs serve more demonstration purposes. Guardrails can be made minimally noticeable, but it will significantly increase the safety of the stairs.
For further conversation, we need an accurate command of the "ladder" terminology.
Baluster- a post that serves to support the railing.
Console- shelf structure, rigidly fixed at one end with a bracket or pinch.
Kosour- the bearing beam of the stairs, on which the steps are attached.
railing- stair railing.
riser- step height; a vertically installed bar that closes the space under the step.
handrail- part of the railing, which is taken by hand when descending / ascending the stairs.
Prokid- detail of the railing, parallel to the march.
tread- the horizontal part of the step on which the foot is placed.
Pillar(flattering) - the most extreme railing post, which rests on the ceiling.
bowstring(staircase) - a carrier beam that holds the steps fixed to it with ends.
Tyazh- a rod or cable with which the steps of a suspended ladder are attached to the upper ceiling.
Cantilever ladders are generally not sold in ready-made. They are ordered for a specific object and for specific requests of the owner of the house. However, models from the catalog are taken as a basis, which are then adapted to the conditions of the object. European companies at the same time try to make as few changes as possible using factory components. This reduces the cost of stairs. In Russia, there are also companies involved in the production of cantilever stairs, but the latter are made individually.
Support for cantilever ladder
The controversial view of the cantilever staircase, which many people are even afraid to climb for the first time, has its own engineering explanation. I note right away that the construction of a cantilever staircase is a rather laborious and difficult task. The bearing base for cantilever steps is laid into the wall at the stage of its construction. Each rung of a cantilever ladder must unwaveringly support a load of at least 150 kg, not counting the weight of the railing. And this means the load on the extreme point of the suspended stage.
Installation of steps. The wall into which the steps of the cantilever staircase will be mounted must be made of heavy wall materials, for example, in the form of brickwork. The ends of the steps are immured into it, deepening them by at least 20 cm with a maximum march width of 80 cm. Each step must be pinched by at least 10 rows of masonry. If the wall is lined with blocks of porous ceramics, expanded clay concrete blocks or slotted bricks, then the depth of the steps is increased to 30-40 cm. However, this does not always allow the thickness of the wall. When installing steps in aerated concrete, each of them must be reinforced with a heavy concrete element.
Certain requirements are also imposed on the material from which the steps are made. It must be a very hard and resilient material. Reinforced concrete is widely used for these purposes. You should not be afraid of the brutality of this material, because there is always the opportunity to finish concrete with anything. Well, for fashionable style loft concrete steps - that's it.
To embed the brackets in the wall to a depth of 25-30 cm, meter lengths are embedded profile pipe. In this case, the outlets make up 2/3 of the length of the steps. Such large overhangs make it possible to use almost any material for the manufacture of the steps themselves, up to chipboard or MDF. The steps in this design are based on steel brackets, so they are freed from the bearing load. Metal fasteners are hidden in the selected grooves and holes in the steps. I note that, despite all the clarity of pinching or immuring steps, such work should be carried out under architectural supervision. Better yet, entrust this work reputable construction company.
Another way to build a cantilever staircase involves anchoring. The method is good, first of all, in that it allows the installation of steps after the completion of the construction of the supporting wall. For each step, a separate welded bracket is intended, which is fastened with 4-6 anchor bolts with a length of 150 mm and a diameter of at least 10 mm. But this method is only suitable in cases where the wall is made of solid brick. Neither aerated concrete nor slotted brick can withstand such a load - the anchors will loosen, and the steps will be in danger of collapse.
Fastening to a metal frame supporting structure. If the wall, near which the cantilever staircase should be attached, does not have sufficient bearing capacity, then this complicates the matter, but does not deprive the chance to realize the plan. the only right decision at the same time, there will be a creation of a powerful steel profile frame-frame, which will serve as the basis for the cantilever steps. The frame-frame is made up to the ceiling. At one end it is attached to the upper, the other - to the lower ceiling. Cantilever supports for steps can either be welded to the frame or bolted. The supporting structure (frame-frame) is sheathed with drywall, after which it looks like an ordinary wall.
The frame-frame can be replaced by a steel bowstring attached to the upper and lower ceilings on powerful support platforms. On the bowstring fixed in this way, when walking up the stairs, significant torsional loads will be exerted. To resist them, it must be in the form of a truss with longitudinal, transverse and diagonal stiffeners. This design can be compared with the boom of a crane. But even with this, it is rarely possible to achieve a feeling of “solidity” of steps. Therefore, the most reliable method is walling into a wall or fastening using a frame frame.
Ways to strengthen the cantilever structure. Fastening a step on only one side requires extreme strength, which is not easy to achieve. To stabilize the steps, you can resort to an additional, but little noticeable supporting structure. In order to avoid "keying", the cantilever steps can be interconnected with bolts, transferring the load to the ceiling. At the same time, each cantilever step is connected with one bolt, and not two. These bolts can be disguised as fencing details or hidden in treads. The use of bolts allows you to reduce the load on the wall brackets, which makes them less powerful. By linking two adjacent steps, we halve the load on the cantilever mount of each of them. Thus, for one step, the power of a pair of rods 400-600 mm long and 30-40 mm in diameter is enough, which are embedded in the wall to a depth of only 80-160 mm.
Another way to insure cantilever steps is to fasten their edges to the ceiling with the help of strands in the form of steel cables with a diameter of 8-10 mm, the slack of which is selected by installed lanyards (screw hooks). Hanging belay looks less massive than bolt belay. If desired, the cables can be passed into chrome pipes.
Stairs are designed for communication between floors and timely evacuation of people from the premises. stairwell in most cases, they are used to accommodate utilities: heating mains, internal drain risers, electrical distribution panels and electric meters.
In the measures for the technical operation of stairs, they provide for the prevention of possible defects due to poor quality design and construction: corrosion of metal stringers, deflections of reinforced concrete marches, cracks in landings and steps, weakening of the fastening of fences, handrails, destruction of the finishing layer of walls and ceramic tiles floors of staircases.
During the operation of wooden stairs, load-bearing elements may rot, their strength may decrease, the fastening of the railing to the bowstrings may be broken, and the paint layer may be destroyed.
The condition of the elements of the stairs, the reliability of the fastening of the railings, the condition of the floors, the color of the walls are determined by an external inspection. With significant corrosion of metal stringers and platform beams, the bearing capacity of platforms and flights of stairs is sometimes checked by test load.
Defects of stairs and their causes
Stairs according to their purpose are divided into main and secondary. They consist of marches and platforms placed in the stairwell, and are:
stone (from natural and artificial stone);
concrete and reinforced concrete;
metal and wood.
Depending on the number of marches within the height of one floor, the stairs are divided into one-, two- and three-flight.
Common defects in stairs made of natural and artificial stone are breaks in treads and steps, cracks in individual steps, cracking of steps, a violation of the continuity of the flight of stairs, a divergence of the steps of an external staircase due to exposure to low temperatures. The causes of these damages lie in the improper laying of steps, mechanical influences on them and natural wear and tear. Often there is a loosening of the railing at the stairs due to the weakening of the sealing of their racks. Incorrect installation of the steps of external stairs, when the slope of the steps is directed towards the seams of the joints, leads to their freezing in winter and breakdown.
In concrete and reinforced concrete stairs, breaks and cracks, weakening of the sealing of cantilever (hanging) stairs, damage to the lining, as well as potholes and breaks in them are noted; deformation of reinforced concrete structures and exposure of reinforcement under a peeled protective layer; stringer deformations; fractures of monolithic landings; weakening of concrete of external stairs; fracture chipping and surface peeling. Cracks appearing in the compressed belt of stairs reinforced as two-bearing beams indicate a weakening of the cross section, and when the edges of cracks in the concrete are painted, this is a confirmation of the insufficient bearing capacity of the concrete of the compressed zone. For outdoor stairs great harm can bring humidification and alternate freezing and thawing. Therefore, they use denser concretes with high frost resistance and appropriate selection of aggregate, quality and quantity of cement.
Wooden stairs are characterized by damage from mechanical stress, exposure to fungal diseases and insects. Wooden stairs cannot be designed for evacuation of people both inside and outside the building, as they have a low fire resistance limit.
Metal stairs have the following defects and damage: excessive deflection load-bearing elements; cracks and fractures of connecting elements; steps deformation; excessively smooth surface, unsafe for walking; protrusions of connecting elements; corrosion of all or part steel structures; abrasion and polishing of the surface of the steps.
Most of the metal stairs are of limited use, mainly for maintenance of technological sites and as evacuation in case of fire. Excessive deflection of the stringers of the stairs indicates their insufficient rigidity and design errors, and the presence of corrosion indicates a lack of protection against it during the operation of the stairs.
A kosour in a staircase is called an inclined metal beam on which the steps are based.
This calculation concerns metal stringers from rolled channels.
Attention! In the article, the font periodically flies, after which the sign "?" I apologize for the inconvenience.
Initial data.
Width of the flight of stairs 1.05 m ( stair steps prefabricated LS11, weight of the 1st stage 105 kg). The number of stringers - 2. H \u003d 1.65 m - half the height of the floor; l 1 \u003d 3.7 m - the length of the stringer. Stringer angle α = 27°, cosα = 0.892.
Collection of loads.
As a result, the current standard load on the inclined stringer is q 1 n \u003d 449 kg / m 2, and the calculated q 1 p \u003d 584 kg / m 2.
Calculation (selection of the section of the stringer).
The first thing to do in this calculation is to bring the load per 1 sq. m of the march area to the horizontal and find the horizontal projection of the kosour. Those. in fact, with the actual length of the kosour l 1 and the load per 1 sq.m of the march q 1, we translate these values into the horizontal plane through cosα so that the relationship between q and l remained in effect.
For this we have two formulas:
1) the load per 1 m 2 of the horizontal projection of the march is:
q = q 1 / cos 2 α;
2) the horizontal projection of the march is:
l = l 1 cosα.
Please note that the steeper the angle of inclination of the kosour, the shorter the length of the march projection, but the greater the load per 1 m 2 of this horizontal projection. This just preserves the dependence between q and l to which we aspire.
As proof, consider two stringers of the same length 3 m with the same load of 600 kg / m 2, but the first is located at an angle of 60 degrees, and the second - 30. It can be seen from the figure that for these stringers the projections of the load and the length of the stringer are very different from each other, but the bending moment is the same for both cases.
Let us determine the normative and calculated value of q, as well as l for our example:
q n \u003d q n 1 / cos 2 α \u003d 449 / 0.892 2 \u003d 564 kg / m 2 \u003d 0.0564 kg / cm 2;
q p \u003d q p 1 / cos 2 α \u003d 584 / 0.892 2 \u003d 734 kg / m 2 \u003d 0.0734 kg / cm 2;
l = l 1 cosα \u003d 3.7 * 0.892 \u003d 3.3 m.
In order to select the cross section of the stringer, it is necessary to determine its moment of resistance W and moment of inertia I.
The moment of resistance is found by the formula W \u003d q p a l 2 /(2*8mR), where
q p \u003d 0.0734 kg / cm 2;
l\u003d 3.3 m \u003d 330 cm - the length of the horizontal projection of the stringer;
m = 0.9 is the coefficient of operating conditions of the stringer;
R \u003d 2100 kg / cm 2 - design resistance steel grade St3;
8 - part of the notorious formula for determining the bending moment (M \u003d ql 2 / 8).
So, W \u003d 0.0734 * 105 * 330 2 / (2 * 8 * 0.9 * 2100) \u003d 27.8 cm 3.
The moment of inertia is found by the formula I \u003d 150 * 5 * aq n l 3 /(384*2Ecos?) , where
E \u003d 2100000 kg / cm 2 - the modulus of elasticity of steel;
150 - from the condition of maximum deflection f = l/150;
a \u003d 1.05 m \u003d 105 cm - march width;
2 - the number of stringers in the march;
5/348 is a dimensionless coefficient.
For those who want to understand in more detail the definition of the moment of inertia, let's turn to Linovich and derive the above formula (it is somewhat different from the original source, but the result of the calculations will be the same).
The moment of inertia can be determined from the formula for the allowable relative deflection of the element. The deflection of the stringer is calculated by the formula: f = 5q l 4 /348EI, whence I = 5q l 4/348Ef.
In our case:
q \u003d aq n 1 / 2 \u003d aq n cos 2 ? / 2 - distributed load on the stringer from half the march (in the comments they often ask why the kosour is considered for the entire load from the march, and not for half - and so, the deuce in this formula just gives half the load);
l 4 = l 1 4 = (l/cos?) 4 = l 4 / cos? 4 ;
f= l 1 /150 = l/150cos? - relative deflection (according to DSTU "Deflections and displacements" for a span of 3 m).
Plugging everything into the formula, we get:
I \u003d 150 * cos? * 5aq n cos 2 ? l 4 / (348 * 2E l cos 4 ?) = 150*5*aq n l 3 /(348*2Ecos?).
Linovich has, in fact, the same thing, only all the numbers in the formula are reduced to the "coefficient With, depending on the deflection. But since in modern standards the requirements for deflections are more stringent (we need to limit ourselves to 1/150 instead of 1/200), then for ease of understanding, all numbers are left in the formula, without any abbreviations.
So, I \u003d 150 * 5 * 105 * 0.0564 * 330 3 / (384 * 2 * 2100000 * 0.892) \u003d 110.9 cm 4.
We select a rolling element from the table below. Channel number 10 suits us.
This calculation was made according to the recommendations of the book Linovich L.E. "Calculation and design of parts of civil buildings" and provides only for the selection of the section of a metal element. For those who want to understand the calculation in more detail metal stringer, as well as with the design of staircase elements, you must refer to the following regulatory documents:
SNiP III-18-75 "Metal structures";
DBN V.2.6-163:2010 "Steel structures".
In addition to calculating the kosour using the above formulas, you also need to calculate the fluctuation. What it is? Kosour can be strong and reliable, but when walking up the stairs, it seems that she shudders with every step. The feeling is not pleasant, so the standards provide for the following condition: if you load the stringer with a concentrated load of 100 kg in the middle of the span, it should bend no more than 0.7 mm (see DSTU B.V.1.2-3: 2006, table 1, p. 4).
The table below shows the results of the calculation for fluctuation for stairs with steps 300x150 (h), this is the most convenient size of steps for a person, with different floor heights, and hence different lengths of the stringer. As a result, even if the above calculation gives a smaller section of the element, you need to finally select the kosour by checking the data in the table.
|
March projection length Lx, m |
March height H, m |
Stringer length L, m |
Rolled channel number GOST 8240-97, DSTU 3436-96 |
Number of bent channel GOST 8278-83 |
I-beam number GOST 8239-89 |
Dimensions of bent square pipe GOST 30245-94, DSTU B.V.2-6-8-95 |
In order to properly design the stairs, you can use the typical series:
1.450-1 "Stairs from prefabricated reinforced concrete steps on steel stringers";
1.450-3 "Steel stairs, platforms, ladders and railings".
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When you think about the need for comfortable and safe access to the second floor even in the process of designing a house, you can lay a staircase of any type. This is much more effective than after trying to squeeze in at least something digestible, not to mention aesthetics. One of the participants of our portal thought of everything in advance, and as a result, he has a cantilever staircase, which is considered one of the most attractive in terms of "airiness". His experience is interesting in that, having remained a customer, he was still able to save decently even in terms of finances, not to mention time and labor costs.
- About cantilever stairs.
- sergpn.
- Project.
- Materials and tools.
- Execution.
About cantilever stairs
The effect of lightness and airiness in these designs is achieved due to the absence of external supports in the usual sense - there is no even stringer, no bowstring, no vertical support. "Soaring" steps are mounted directly into the wall, given that the entire load will fall only on this fastener. When choosing this type of stairs, it is necessary to correctly calculate, first of all, the bearing capacity of the wall. The type of fastening of the steps depends precisely on the result of the calculations, these can be the following options:
- tie-in into the wall - the depth depends on the strength of the wall, on average 20-40 cm;
- brackets - how special fasteners, and various variations (metal plates, channel, decorative supports);
- frame - with a minimum bearing capacity of the wall, a metal frame (channel, profile) is placed close to it, which is fixed to the ceilings, and cantilever steps to it.
The handrail is usually launched along the wall, if necessary, ceiling strands are made as a fence, in rare cases, for the sake of the visual component, they do without strands and without a handrail.
With regard to materials, the flight of fancy is almost limitless, but the most practical stairs with steps on a metal frame with wooden lining or cases. It is this version of the execution of our craftsman.
Metal cantilever staircase from sergpn
sergpn
Project
Topikstarter's house was built using monolithic technology, and since he originally conceived the cantilever staircase, one of the stiffening diaphragms metal frame and was involved in the construction. The missing fragment was supplemented with a channel.
All calculations and the project itself sergpn ordered from professionals. Both bearing capacity and resistance to dynamic loads are taken into account. Our craftsman believes that the project is mandatory.
sergpn
All points were taken into account at the design stage, I deliberately singled out the costs for the calculation in a separate line, and did not write that “we go to the barn, look at what is left of the scrap metal, and cook a staircase of approximately this shape from this.” Considering the pathological rejection of most of the members of the forum of any expenses for designers and the desire to build by intuition, I want to convey to them that the project and calculation are savings, not expenses.
Drawings of your stairs sergpn posted for everyone interested.
Materials and tools
Used materials:
- profile pipe 60 × 60 × 5 mm - frame of steps;
- sheet metal, 10 mm thick - base plates and "kerchiefs";
- sheet metal, 4 mm thick - covering and end strips;
- channel 270 × 6 mm - the missing part of the support for four steps;
- chemical anchors, studs - for attaching support plates and channel to the wall.
Instead of bothering with cutting such thick metal with a grinder, I gave everything to the workshop for plasma cutting, an inverter welder and professional welders of the 5th category were used for welding.
Execution
At the first stage, according to the marking, holes were drilled for the studs and fixed in the wall; next, they mounted the support plates for the steps and the channel on them. The craftsman preferred chemical anchors to ordinary ones in order to avoid the formation of backlash in the future.
Due to certain difficulties, the algorithm for the execution of steps turned out to be as follows:
- pipes "tacks" to the base plate;
- kerchiefs;
- covering sheet;
- end plank.
It is this sequence that is due to the fact that in other cases it was not possible to maintain the ideal plane.
sergpn
We cooked alternately, which is somewhat more difficult, due to the inability to attach the thrust plates evenly (somewhere reinforcement, somewhere else some kind of trouble). Therefore, each step is made individually. It is easier to weld a frame from a professional pipe, but this design works worse for bending than parallel pipes completely sewn on top with a covering plate. But, on the other hand, sewing with a sheet from above is possible (as practice has shown) only for pipes that are already welded to the plate, otherwise it is difficult to maintain parallelism (the sheet leads). That, in fact, because of this, this assembly method was chosen.
Some participants in the topic were interested in the question of whether it was easier to use through fasteners. As the craftsman answered, due to the load, it is impossible to make the bolts flush. And to do the double work of attaching the plates on the other side and then figure out how to close them is too problematic. Others were confused by kerchiefs, since many examples of mounting steps are without this knot. It turned out that scarves are not only necessary, but also useful.
Since, for financial reasons, decorative wooden cases are not expected in the foreseeable future, the craftsman generously treated the finished structure with a primer and stopped there for now.
As recommended by the project, after completion installation work the ladder was checked for its bearing capacity by the "classic" method - 250 kg bags of cement were loaded onto the step. The deflection was less than 1 mm, which is quite satisfactory, given that the weight of the household is much less, and no one plans to jump on consoles.
Taking into account all the expenses, the staircase cost 45 thousand rubles:
- project - 5 thousand;
- metal (with cutting) - 15 thousand;
- installation (welding / cutting on site) - 20 thousand;
- consumables and accessories (anchors, studs, electrodes, primer) - 5 thousand.
It took only four days to make the stairs. As emphasized separately sergpn, companies offering ready-made designs of such a plan called a price tag of 100 thousand rubles and a period of two weeks. Therefore, even if we refuse self-manufacturing in favor of a professional, really cut costs in half. If you have the appropriate skills and equipment, then the cost of materials is completely minimal in our time.
You can follow the further development of events, more about different types stairs, including cantilever ones - in the article, how to provide access to cold attic- in the material. An example of a very unusual staircase is in one of our videos.
1. Introduction
2. Stairs made of natural and artificial stone
3. Concrete and reinforced concrete stairs
4. Wooden stairs
5. Stairs made of steel structures
6. References
7. Introduction
Faulty condition of stairs (corrosion of metal stringers, increased deflections of platforms and marches, loose fit of platforms and flights to walls, cracks, potholes, delamination of the floor in landings and steps, recesses in steps from abrasion, weakening of fastening of fences, handrails and safety nets, damage to railings, rotting of wood, insufficient strength of fastenings of bowstrings to strut beams, etc. .) should be eliminated as they appear and further destruction should be prevented.
Metal elements of stairs should be painted periodically every five to six years, after cleaning the surfaces from rust. Metal stringers must be plastered or painted with paint
providing a fire resistance limit of 1 hour.
In case of deflection of flights of stairs and landings exceeding the permissible norms (in the case of increasing deformation), employees of the housing maintenance organization must reinforce the load-bearing elements of the stairs (according to the project), having previously taken measures to ensure the safety of the operation of the stairs.
Sealing of cracks, depressions, potholes and borders in the structures of stairs should be carried out as defects appear using materials similar to the material of the structures. Stair steps that have lost their strength in collapsible marches must be replaced with new ones.
The gaps between the flight of stairs and the wall should be sealed cement mortar. It is recommended to correct chips in the tread rollers by using ready-made inserts or concreting in place.
In stone steps, damaged areas should be cut down and repaired with stone inserts.
Replacing damaged and fixing exfoliated ceramic tiles on landings with new ones should be carried out immediately after the discovery of defects.
4.8.6. Wooden handrails with cracks and curvature should be replaced with new ones. Minor damage (burrs, uneven surface) should be eliminated by cleaning the surface or replacing individual unusable parts with inserts, followed by finishing the handrail.
Damaged sections of the PVC handrail should be cut out and replaced with new ones of the same shape and color. The joints of the handrail inserts must be welded and cleaned.
The bowstrings that have fallen into disrepair, the coverings of the landings of the steps and the damaged parts of the fences must be replaced, and the loose fences must be strengthened.
When conducting overhaul stairs to provide for the device of ramps.
Ladder structures should be painted every five years.
Stair elements:
the minimum allowable value of bearing on concrete and metal surfaces- 50 mm, on brickwork- 120 mm;
permissible violation of the horizontality of landings is not more than 10 mm, and the steps of stairs - not more than 4 mm;
the deviation of the railing from the vertical is not more than 6 mm.
Stairwells:
glazing must be in good working order; the presence of fittings on windows and doors (handles, hardware), staircase lighting;
the room should be regularly ventilated, the air temperature should not be less than + 16 ° С;
regular cleaning should be provided: sweeping windows, window sills, heating appliances - at least 1 time in 5 days; walls - at least 2 times a month; washing - at least 1 time per month;
entrances from stairwells to the attic or roof (with non-attic roofs) must be locked.
It is forbidden to use staircases (even for a short time) for storing materials, equipment and inventory, to arrange storerooms and other utility rooms under flights of stairs.
Gate valves, switchboards and other disconnecting devices located on the stairs must be in closed cabinets, the keys to which are kept by the dispatcher of the housing maintenance organization.
1. STAIRS FROM NATURAL AND ARTIFICIAL STONE
1.1 Step divergence outdoor stairs from freezing
Cause: Wrong styling
Freezing of external stairs of old buildings can
be the result of an improperly executed foundation. When the foundation subsides, the slope of the steps changes, rainwater and snow falls between them, freezing occurs in winter. The reason may be the wrong installation steps. the right way, when the tread slopes outward, is the creation of such profiles when the seams are located above the planes of the treads.
Repair method: In most cases complete dismantling, then a thorough correction of defects and installation of steps by qualified specialists. Naturally, damaged steps are repaired, and some of them are replaced. In the latter case, a more resistant stone material should be selected (granite, syenite, gabbro, andesite, freshwater hard limestone, marble).
1.2 Cracking of steps, violation of the rigidity of the cantilever (hanging) staircase
Cause: Uneven shrinkage of the bearing wall; bad seal; poor quality wedging
Defects in flights of stairs with a stringer, in many cases their destruction is caused by defects in the supporting (bearing) structures. Such structures must be examined on site, to determine from what and how they were made, in what condition
are located, it is sometimes possible to determine at what stage of manufacture a defect occurred.
In buildings built at the turn of the century, stringers made of wood were used. These beams, as a rule, were upholstered with reeds and plastered. Thus, the design turned out to be hidden and it was impossible to determine its diseases (fungus, insect damage). In such a situation, the replacement of the supporting structure is mandatory; repair and re-installation of steps.
1.3 Disruption of the continuity of the flight of stairs, breaks in treads, steps, wear
Cause: Natural wear, mechanical impacts
The natural wear of the running line of old steps becomes the cause of accidents over time. Characteristic defects: breakage of the edges of the steps, thinned due to abrasion, the formation of a wavy surface of the steps. Defects are aggravated by impacts with heavy objects, for example, when carrying bulky items.
Repair method: Small damage to monolithic or wedge-shaped steps is repaired by cutting out a recess in the form dovetail, then dedust, moisten and make an insert from the material of the step or from artificial stone, suitable in color and structure.
Usually, in the manufacture of artificial stone, stone chips are used, obtained by chiseling a recess for an insert. If it is not enough, then crushed stone is added. repair material prepared for 2/3 gravel of various sizes and 1/3 cement. The main requirement is good seal. In most cases, to achieve a reliable result, it is necessary to install a solidly fixed formwork. Newly made or repaired surfaces require wet processing within 7 days. The surface of the artificial stone is ground after 1-2 days. Polishing to a mirror finish is not advisable as the slippery surface can cause accidents. The initial signs of abrasion of the treads, which later appear in the form of waviness or slippery patches, are eliminated by notching the surface.
Defects in stairs made of natural and artificial stone can be repaired using various modern adhesives. At the same time, metal staples made of reinforcing steel are used in stretched belts (Fig.).
Rice. 1.2. Hanging ladder wedging
1 - wedging; 2 - hanging ladder; 3 - bearing wall
Rice. 1.3. The device of stringers from steel beams
1 - flooring from tiles; 2 - solution
1.4 Cracks in individual steps, sometimes breaks
Cause: Mechanical influences
When replacing steps or a whole flight of stairs, hanging stairs should be supported with props, starting from the base of the wall, from the lower floor and along the outer contour. Work begins with gouging out the embedding points. The steps are dismantled from top to bottom. New marches are mounted from below, paying attention to the correct installation of the tread planes so that water flows freely from them when washing the stairs. When replacing, individual steps enter at least to a depth of half a brick with wedging and embedding with bricks on cement mortar (Fig. 1.2). If replacement is not necessary, then flights of stairs can be reinforced with stringers made of steel beams (Fig. 1.3).
1.5 Shell-shaped delamination of the ladder material, cracking
Cause: Fire exposure
Natural stone is not resistant to fire, although it does not burn itself. Under the influence high temperature it cracks, peels off, crumbles. Limestones lose their strength to a large extent under the influence of a relatively low temperature, chemical processes take place in them (lime burning). Igneous rocks behave better in this respect. If water suddenly gets on hot stone steps when extinguishing a fire, then it can severely damage the material from which they are made, and as a result, lead to severe destruction of stone structures.
1.6 Loose railings
Cause: Weakening of handrail posts, fractures due to corrosion
A characteristic defect of the railings of stairs is the loosening of the racks in the places of fastenings, cracking of the stone. The reason may be severe corrosion of metal racks, freezing at their base, mechanical effects (forced loosening), exposure to water, grinding effect from movements in the seams of particles with sharp edges.
It is necessary to periodically inspect the places of sealing of the railing posts. In the initial stage of the development of the defect, you can use a simple pouring of cement mortar, followed by grouting with a sand-cement mixture (1: 1), which stops further destruction, sometimes for many years.
When repairing more significant defects, it may be necessary to install a new nest or replace a rusted rack. Attention should be paid to the care of concrete during its curing period, since the rapid drying of a small amount of concrete or artificial stone leads to its destruction. A good result can only be achieved with proper care and normal hydration.
2.1. Breaks, cracks in concrete stairs
Cause: Cracks in tension or compression belt
Cracks appearing in the compressed chord of stairs reinforced as double beams indicate a weakening of the cross section and can cause trouble. If the edges of concrete cracks are painted, peel off, this indicates a defect in the compressed belt. After an expert assessment, it is necessary to take measures to strengthen or replace the structure.
2.2. Loosening of cantilevered (hanging) stairs
Cause: Insufficient size of the embedment length, which causes loosening; improper installation of steps, due to which water flows down to the wall when washing the stairs.
The repair method is identical to that described in clause 1.4
2.3. Facing damage, potholes, kinks
Cause: Mechanical effects: natural abrasion, waviness, damage by loads carried up the stairs
The repair method is identical to that described in clause 1.3
2.4. Abrasion of plastic or rubber mats covering treads, tears
Cause: Mechanical influences
Destroyed plastic or rubber inserts on the treads are removed, the concrete surface is cleaned, and after checking the correct slope, new ones are glued.
2.5. Breaks, curvature of railings, deformations of stringers, breaks of monolithic landings
Cause: Construction defects, errors in concrete care, corrosion of reinforced concrete, damage to concrete under the influence of acids, alkalis, oils, fats
In any case, you need expert review. After the necessary examination and calculation, a decision is made to repair or replace, in the latter case, factory-made elements can be used.
2.6. Weakening of concrete of external stairs, chipping, fractures, surface peeling
Cause: Exposure to frost during the curing period or frequent freezing of the finished concrete
Constantly wet or frequently moistened concrete stairs frost can cause great damage. Especially for outdoor stairs, frost-resistant concrete is used using frost-resistant inert concrete and with an appropriate selection of the quality and quantity of cement. Repairing old concrete stairs is only a temporary measure, as further freezing leads to their destruction.
2.6. Deformations of reinforced concrete structures, exposure of reinforcement under exfoliated concrete, etc.
Cause: Fire exposure
Under the action of fire (already at a temperature of 500 ° C), additives to concrete burn out; crushed limestone added to concrete begins to decompose (burnt lime is formed); the strength of the reinforcement also decreases. After any fire, it is imperative to conduct an expert survey and determine further measures based on it.
3. WOODEN STAIRS
The material for the manufacture of stairs inside buildings can be soft and hard wood. Frequently used designs are a spiral staircase, a straight or curvilinear non-curved staircase, which are usually well calculated and structurally simple. Defects are usually the result of damage. In rare cases, damage by insects and fungus occurs. It is also rare that defects occur due to corrosion of metal connecting elements.
The way to repair badly worn or broken steps is to replace them completely. Smaller damage is eliminated by inserts. Taking into account the opinion of experts, defects that may arise due to the influence of fungal diseases and insects should be prevented. An essential requirement is the exclusion in all cases of the possibility of moisture stair structures.
Defects in the structures of the stringers, shortcomings in the joints with the walls are eliminated in accordance with the rules for the manufacture of carpentry structures.
A wooden staircase quickly burns out in a fire, so it cannot be intended for the evacuation of people both inside and outside the building.
In the process of reconstruction of residential buildings, regardless of the bearing capacity and condition of the material wooden stairs should be replaced with reinforced concrete, stairs made of natural and artificial stone, with the exception of internal stairs in one-story houses, if they meet the requirements for material and load-bearing capacity.
4. STAIRS FROM STEEL STRUCTURES
4.1 Bending of bearing elements, cracks, fracture of connecting elements, deformation of steps
Cause: Static and dynamic overvoltage
Replacement or strengthening of load-bearing elements in accordance with the expected additional static or dynamic loads, replacement of a metal step (plate), sometimes the installation of stiffeners against possible bending.
4.2 Excessively smooth surface, not safe for walking; protrusions of connecting elements above the step
Cause: constructive effect
Replacement of steps originally made from slabs without roughening or ribbing. Eliminate, in order to avoid accidents, protrusions of the connecting elements by lowering them under the plane of the step plate (welding from the bottom side) or in another way.
4.3 Abrasion of the surface of the steps, polished; jagged edges
Cause: Mechanical influences
Rough surface creation or replacement.
4.4 Deformation of all or part of the staircase structure from high temperature
Cause: Fire
Depending on the expert opinion, the replacement of individual elements or the entire staircase structure, depending on the degree of damage.
4.5 Corrosion of all or part of steel structures
Cause: Corrosion
First of all, the elimination of the causes of moisture, then the removal of rust structural elements suitable for use, and anti-corrosion treatment.
Stairs made of steel structures are very rarely used in residential buildings; in public buildings, offices - in the form spiral staircases(due to limited space). For the most part, they are used in industrial buildings to approach the corresponding technological posts. Usually, marches of such stairs are characterized by high steps (more than 20 cm); steep stairs are equipped with double-sided railings. Increased attention to the condition of such ladders is very important in terms of preventing accidents.
Bibliography:
1. Rules and norms for the technical operation of the housing stock
2. A.V. Kolomeets, E.M. Arievich "Operation of residential buildings", reference guide, M. Stroyizdat. 1985
3. N.V. Nechaev "Overhaul of residential buildings" M. Stroyizdat 1990
4. Boyko M. D. "Maintenance and repair of buildings and structures." Tutorial for universities. Leningrad: Stroyizdat, Leningrad. department, 1986.-256 p.
