The jumper as a structure over the opening, perceiving loads from overlying walls and floors, appeared a long time ago, as soon as people began to build stone public buildings and housing.
A bit of history
For the most part, the lintels above the openings were arched, since the upper semicircular window contour somewhat weakened the load. They were made of large stones. These stones were carefully carved out, adjusted to each other, such work required a considerable investment of time and effort.
The construction of buildings took a long time, the slightest inaccuracy in the installation of lintels, especially central, castle stones, could lead to distortion and destruction of the structure. But when the magnificent building was built, his life lasted for centuries.
With the advent of brick as a building material, the lintels at first were still arched. But it was already easier to work, since the bricks were the same size, and when the jumper was installed, it was possible to make seams of different thicknesses, due to which the desired opening radius was achieved
Bar reinforced concrete lintels
When people built houses of wood, the bridge over the window or doorway was a thick log that overlapped the window with a large margin.
With the development of science, technology, the discovery of new technologies in construction, in particular with the introduction of reinforced concrete, crossbar reinforced concrete jumpers appeared. These jumpers have a rectangular cross section, their width is not more than 250 mm. They are designed to close openings in the brick walls of residential and public buildings. These products are manufactured in the 1.038.1-1 series.
The photo above shows the bar jumpers. In addition to squared, plate, beam, facade lintels and runs are produced. All of them relate to fireproof structures.
Jumper marking
All jumper names consist of five groups of numbers and letters.
For example, jumper 2 PB 19-3-p.
- 2 means cross section number;
- PB designates the name - a bar jumper;
- 19 - product length in decimeters;
- 3 - design load in kn / m (kgf / m);
- n means the presence of mounting loops.
The first digits in the marking, from 1 to 5, indicate the dimensions of the cross section of the product.
Those bar jumpers, in the name of which the first number is 1, with transverse dimensions of 120x65 (height) mm, can overlap openings in non-bearing 120 mm thick brick walls.
If the first is the number 2, then the transverse dimensions will be 120x140 (height) mm. These jumpers withstand loads up to 400 kgf / m and are used in self-supporting walls.
If the number 3 is the first, then the transverse dimensions will be 120x220 (height) mm. These jumpers are reinforced, they withstand the load of the floor.
Each jumper has a certain depth of support on the wall, depending on its bearing capacity. If the load on the jumper does not exceed 400 kgf / m, then the depth of support can be 120 mm, if the load is more than 400 kgf / m, then the depth of support will already be from 170 mm to 230 mm.
In order to choose the right jumper, you need to know the width of the blocked opening, the thickness of the wall, where the opening is located, as well as whether the ceiling is based on it.
Depending on the thickness of the wall above the opening, two or three squared bridges are laid, and reinforced is laid on the side of the ceiling.
Features of transportation and styling
Sometimes, especially before transportation, you need to calculate the volume of the bridge jumpers. When calculating, it should be borne in mind that the transport stack should have a height of not more than 2 m, and each jumper should be laid on two wooden spacers.
Bar jumpers above the openings are installed after bringing the masonry to the top of the opening, and special attention is paid to the horizontal position. The top plane of the lintel should be flush with the top of the masonry.
Jumpers are installed on a layer of cement-sand mortar M100.
The jumper located at the outer edge of the wall is installed 65 mm below the rest, forming a quarter that is necessary when installing the windows so that the wind does not blow in them.