Home |Reinforcement |Is it possible to weld reinforcement for the foundation?
Date: January 13, 2019
Comments: 4
When starting the construction of a house, we hope that it will be a reliable protection for the family hearth. In order for expectations to be met, you need to make an effort in your work, competently approach the solution of many issues, one of which is whether it is possible to weld reinforcement for the foundation.
There is still no consensus on what is better – welding or knitting a frame for the foundation. If for high-rise buildings, the foundation of which carries enormous loads, welded reinforcement is the only correct solution, then when constructing one-story buildings, expert opinions differ. Let's figure out what advantages and disadvantages are inherent in welding and knitting.
Strengthening the foundation - what is it for?
A well-designed and high-quality foundation is a guarantee of the durability of the structure. A strong, indestructible base will prevent shrinkage, which causes cracks and subsequent destruction of the structure. Therefore, strengthening the foundation is a serious issue that cannot be treated superficially. Increasing the strength of the foundation is achieved by reinforcing the structure with metal mesh or rods of a certain diameter.
Should the reinforcement for the foundation be welded or knitted - this is the main question that many people think about
For low-rise buildings, a strip foundation is most often installed. You can save money and fill the foundation with regular concrete without additional reinforcement. Most likely, after some time, cracks and deformations will appear in the foundation. To prevent undesirable consequences, carry out reinforcement work with a steel frame that:
- Increases strength.
- Evenly distributes the load.
- Compensates for soil reactions during freezing.
- Will increase the service life of the structure.
Reinforcement in concrete will protect the foundation from cracking and destruction.
Methods for connecting reinforcing elements
There are various methods to increase the strength characteristics of the foundation. Private developers use any available material (waste metal, broken glass, etc.). For country houses this is an acceptable option. But to build a reliable house, even a one-story one, use proven technologies for strengthening with metal mesh or rods. If your choice is a mesh, then you only need to cut it correctly and install it properly in the prepared trenches. The use of metal elements implies the creation of a single structure from them, the so-called frame.
It is worth knitting reinforcement in cases where you need to get a good foundation on difficult soil
There are two ways to achieve this:
- tie using flexible wire for connection;
- apply welding to fix the structural elements.
Both options have strengths and weaknesses. Let's conduct a comparative analysis of each of them.
Application area
This standard applies to welded connections of rod and wire reinforcement, welded connections of rod reinforcement with sheet and shaped rolled products, performed in the manufacture of reinforcement and embedded products of reinforced concrete structures, as well as during the installation of prefabricated and construction of monolithic reinforced concrete structures.
The standard establishes the types, design and dimensions of the specified joints made by resistance and arc welding.
The standard does not apply to welded connections of embedded products that do not have anchor bars made of reinforcing steel.
Reinforcement knitting technology
There are several ways to knit foundation reinforcement with special wire. This work is carried out directly on site. You can use the services of specialized workshops where the work will be completed efficiently and within the agreed time frame. There is a small downside to this service. You will have to find transport to transport large structures. In small settlements this is difficult and expensive. Therefore, we advise you to independently master the process of knitting frame elements:
- Decide on the number of connection points.
- Cut the appropriate number of pieces of steel wire 20 cm long. The diameter corresponds to 1.2-1.4 mm.
- Fold the cut piece in half.
- Bring the resulting loop to the junction of the elements.
- Use a crochet hook. You can make it yourself or purchase it in a store. Insert the working part into the loop.
- Grab the loose ends and pull them through the hole. The junction of the rods must be covered with wire.
- Tighten with maximum force and, by turning the hook several times, ensure a tight connection of the frame structure parts.
The reinforcement is knitted using a special wire that connects the rods at the corners of the structure
Knitting using a crochet hook is one of the cheapest, but most labor-intensive methods of connecting reinforcing elements. No expensive construction tools are used here; the work is carried out by one or two workers. If you want to speed up and make your work easier, you can purchase:
- automatic tying gun. With its help, the connection speed will increase significantly, but handling it requires certain skills;
- a rotary power tool, such as a drill or screwdriver with a special attachment, which can be purchased in specialized stores.
The advantages of automated devices include increased productivity, the ability to connect structural elements in hard-to-reach places of the frame, and a significant reduction in physical costs.
Recommended current values
When welding reinforcement frames, the choice of current power indicators directly depends on the thickness of the reinforcing element, the brand and diameter of the electrode. As the dimensional parameters of the reinforcing rod increase, the values increase.
| Electrode brand | Diameter, mm | Current strength, A |
| Brands like E42, SM-11 | 3 | 100–140 |
| 4 | 160–220 | |
| 5 | 180–280 | |
| UONI-13/45 | 2 | 30–50 |
| 2,5 | 60–80 | |
| 3 | 80–100 | |
| 4 | 100–160 | |
| 5 | 140–200 | |
| ANO-5 | 4 | 160–230 |
| 5 | 190–300 | |
| ANO-6 | 4 | 180–200 |
| 5 | 180–270 | |
| OES-23 | 2 | 40–50 |
| 3 | 90–120 | |
| WCC-4 | 3 | 90–100 |
| 4 | 120–160 | |
| MR-3, E-46 | 3 | 90–120 |
| 4 | 160–180 | |
| 5 | 170–230 | |
| 6 | 280–320 |
Organization of work
When starting work on creating a reinforced frame using the knitting method, purchase the necessary tools and materials in advance. By following simple recommendations, you will quickly master the connection technique and be able to perform the assigned tasks efficiently:
- Place the bottom row of horizontal structural elements at a short distance from the ground surface - 4/6 cm. Wooden or plastic pads are suitable to ensure the required gap. Their task is to prevent the frame from coming into contact with the soil.
- Install vertical elements at a fixed distance from each other.
Keep your step even. Ensure that the bars remain stationary using locking devices. Protect metal from contact with the ground using non-metallic cup holders. It is important to comply with this requirement to avoid corrosion of the reinforcement in the future. The knitting process itself is different in that it can be done either directly at the site of construction of the building or in a special workshop - Proceed to fixing the frame elements. Pay special attention to the reliability of connections. They must withstand the stage of pouring concrete mixture without moving.
- When constructing a reinforcing frame in several tiers, maintain equal distances between horizontal and vertical elements. Provide additional fastening to the corners of the structure - they tend to move during pouring. Make sure that the corner parts of the reinforcement are bent inward and do not protrude beyond the base.
- Observe the requirements laid down in the technical specifications for the selection of grades and assortments of materials.
- Carry out simple strength tests on the frame after completion of the work. Place a board on the top tier of the structure and walk along it - the frame should remain motionless under the influence of human weight.
- Immediately before pouring concrete, additionally fix the entire structure to prevent vertical deviations.
TERMS AND EXPLANATIONS
SP 260.1325800.2016 thin-walled steel structures made of cold-formed galvanized profiles and corrugated sheets. design rules (with change n 1)
Table 30
| Term | Explanation |
| Bath welding | A process in which the melting of the ends of the joined rods occurs mainly due to the heat of the molten metal bath |
| Bathroom mechanized welding | A welding process in which the filler wire is fed into the welding zone automatically and the arc or holder is controlled manually |
| Bath single-electrode welding | A welding process in which electrode material in the form of a single (piece) electrode is fed manually into the welding zone |
| Mechanized arc welding with flux-cored wire | A welding process in which electrode material in the form of flux-cored wire is fed automatically into the welding zone |
| Inventory form | A reusable device (copper, graphite) that ensures the formation of deposited metal during welding and easy removal after welding |
| Steel bracket | An auxiliary element that ensures the formation of a weld, which is an integral part of the connection and takes up part of the load when the connection operates in the structure |
| Cross connection | Connection of rods welded at the intersection |
| Settlement (h, mm) of rods in cross-shaped connections | The amount of pressing of the rods into each other in the area heated during resistance welding to a plastic state |
| Combined load-bearing and forming elements | Elements consisting of the remaining steel half-bracket and the inventory copper half-mold |
| Mechanized submerged arc welding without filler metal | A process in which the entire welding cycle is carried out in a predetermined automatic mode |
| Manual arc welding with low mechanization submerged arc without filler metal | A process in which auxiliary operations are partially mechanized and the entire welding cycle is performed manually |
Rebar welding technology
Although welding reinforcement for the foundation is more labor-intensive than knitting, it is impossible to completely abandon it. On large construction sites, when constructing multi-story buildings, it is impossible to do without welding. The foundations of such structures bear increased loads, and therefore the strength requirements are appropriate. To weld reinforcement for the foundation, use special brands of products - A400C or A500C. The diameter of the rods is within 3-5 centimeters. Resistance spot welding is used for the work. Considering the fact that when the metal overheats, changes in the structure occur, causing a weakening of the strength characteristics, it is desirable that the welding of reinforcement for the foundation takes place at specialized enterprises or is carried out on construction sites by qualified welders.
When welding, the strength of the reinforcement is reduced and the internal structure is damaged
The production of welded frames in industrial conditions is carried out in several stages:
- The technical control department checks the quality of materials that are planned to be used in the manufacture of the frame. Material that does not meet the requirements of standards and specifications is rejected;
- Round rolled steel made of St. 0 or St. 3, previously cleaned of rust and dirt, is straightened, marked, and cut to a given size. The elements are cleaned with an abrasive tool;
- the workpieces are connected into a flat structure. Spot welding of reinforcement is carried out with a workpiece diameter of up to 26 millimeters. When working with reinforcement of increased diameter, deformations of the structure occur due to strong heating during welding. To avoid distortion, the elements are lightly grabbed;
- Using special conductors, flat elements are installed vertically above each other at a calculated distance. Conductors are manufactured with a high degree of accuracy - deviations from the specified parameters do not exceed three millimeters;
- a preliminary bunch of elements is made;
- The compliance of the spatial design with the technical design is checked, the entire assembly as a whole is corrected, and the required length of welding seams is determined. To avoid deformation of elements from overheating, the sequence of welding joints is clearly defined;
- The spatial structure is finally welded.
Most often this method is used in places where the soil has a stable position, that is, it does not settle too much
When welding directly on a construction site, the procedure is similar. The only difference is the inconvenience of using arc welding. Therefore, when assembling a frame module on site, spot welding of reinforcement is used. It is mobile, and when equipped with special pliers, you can perform work even in a suspended state, with rotation to any angle.
APPENDIX 1 (mandatory). Terms and explanations
APPENDIX 1 Mandatory
Table 30
| Term | Explanation |
| Bath welding | A process in which the melting of the ends of the joined rods occurs mainly due to the heat of the molten metal bath |
| Bathroom mechanized welding | A welding process in which the filler wire is fed into the welding zone automatically and the arc or holder is controlled manually |
| Bath single-electrode welding | A welding process in which electrode material in the form of a single (piece) electrode is fed manually into the welding zone |
| Mechanized arc welding with flux-cored wire | A welding process in which electrode material in the form of flux-cored wire is fed automatically into the welding zone |
| Inventory form | A reusable device (copper, graphite) that ensures the formation of deposited metal during welding and easy removal after welding |
| Steel bracket | An auxiliary element that ensures the formation of a weld seam, which is an integral part of the connection and takes up part of the load when the connection operates in the structure |
| Cross connection | Connection of rods welded at the intersection |
| Settlement (mm) of rods in cross-shaped connections | The amount of pressing of the rods into each other in the area heated during resistance welding to a plastic state |
| Combined load-bearing and forming elements | Elements consisting of the remaining steel half-bracket and the inventory copper half-mold |
| Mechanized submerged arc welding without filler metal | A process in which the entire welding cycle is carried out in a predetermined automatic mode |
| Manual arc welding with low mechanization submerged arc without filler metal | A process in which auxiliary operations are partially mechanized and the entire welding cycle is performed manually |
Which connection method do you prefer?
Before you finally decide whether to knit or weld a reinforcement frame, weigh the pros and cons. Each connection method has positive and negative aspects. Recommendations from specialists will help you choose the optimal solution. When constructing multi-storey buildings with an increased load on the foundation, welding is clearly chosen. The diameter of the steel bar is selected to be at least 30 millimeters. Why should reinforcement with a larger cross-section be preferred? Answer: to minimize the risk of burnout, which will weaken the strength of the connection.
The disadvantages of the welding method, which limits the scope of application, include the occurrence of internal stresses, which increase the likelihood of cracking during casting. It is problematic to use in seismically unstable areas and on complex soils, where the shrinkage process takes a long time and can cause destruction.
But we must not forget about the advantages of welding:
Speed of work, allowing to significantly reduce construction time.
- Increased rigidity of the finished module.
- Obtaining a solid foundation that can withstand heavy loads.
For private buildings, it is better to use the knitting method, which:
- it is simple and accessible, even for those starting a construction career;
- eliminates the need to search for a welding machine and a high-class welder capable of performing work without defects;
- does not create additional stress at the joints;
- allows the use of cheaper reinforcement of reduced cross-section for reinforcement.
The disadvantages include slight rigidity, which is not particularly important when constructing low-rise buildings.
Boil or knit? That is the question…
Based on the above, we draw conclusions about: which methods are better to use in private construction - bonding or welding? Undoubtedly, each of the discussed methods is famous for its advantages, but there are also disadvantages. Welding proceeds at maximum speed, and knitting is a rather lengthy process, although it does not require a special apparatus. It is best used in the construction of private houses, cottages, outbuildings, and baths. It is in these cases that the method is most effective.
And when constructing buildings with large dimensions, attention turns to welding. Rods are used that have a diameter of more than . Therefore, connections using wire will present certain difficulties. Welding in this case will be the most correct solution.
However, the disadvantages of the welding method technology do not make it possible to use it on so-called difficult soils (and swampy areas practically exclude this method). After all, if a connection is used by welding, it will not withstand the external stresses that arise during shrinkage, which will lead to a loss of integrity of the structures and a loss of their rigidity. Tying technologies will ensure the most flexible connection of reinforcement on difficult soils. Here the rods, depending on the condition of the soil, will be able to move spatially without causing damage to the entire structure.
Video about methods of connecting reinforcement using various methods:
