Welded connections.Welded connections.The calculation is intended for the geometrical design and strength control of statically loaded welded connections of machine structures manufactured from carbon steels. The program enables you to design over 50 of the most common types of welded connections stressed by various combinations of load. The calculation deals with the following tasks:
The calculation is based on data, procedures and algorithms from specialized literature and standards AWS, AISC, ANSI, EN, ISO, DIN and others.
List of standards: prEN 1993-1-8, EN 10024, EN 10034, EN 10055, EN 10056, EN 10279, DS 952, DIN 15018, DIN 18800, DIN 1024, DIN 1025, DIN 1026, DIN 1028, DIN 1029, CSN 050120
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Information on the syntax and control of the calculation can be found in the document "Control, structure and syntax of calculations".
Information on the purpose, use and control of the paragraph "Information on the project" can be found in the document "Information on the project".
The welded connections are solid, non-detachable connections based on the principle of local melting of connected parts using heat or pressure. The joining of components proper may be achieved technically using two methods:
An optimum result of the welding process should be a weld with mechanical properties similar as far as possible to the properties of the basic material. According to their function, we can divide welds into:
This program is designed for the calculation of statically loaded welded connections of machinery structures manufactured from carbon steels, for working temperatures ranging from -20 to 150°C. The program enables you to perform geometrical design and strength checks of force connections with the most common types of fusion welds and connections with spot resistance welds. The calculation does not consider the sudden formation of fragile fractures, change in material properties due to temperature, impact of own tensions or concentration of stress in the weld.
An accurate theoretical solution to force and strength conditions is an extremely complicated problem for welded connections, even for welds with simple shapes. That is why common technical calculations are based on a range of conventions and simplified premises. In view of the strength checks, welded parts are usually considered a single compact part with a dangerous spot (section) in the welded area. On the grounds that there is an even distribution of stress in the active weld section, only theoretical rated stress in the specified section is specified for the respective load, regardless of the technological workmanship of the weld or potential internal tension. For connections with multiple welds, an even load on individual welds is assumed.
The strength checks of the connection are performed by simple comparison of the calculated rated stress with the permissible stress in the weld. Permissible weld stress "SwA" is usually specified from the value of the yield strength of the basic material "Re" based on the required safety.
When selecting the safety coefficient "FS", it is necessary to consider the specific factors of welded connections in addition to the general principles used to specify the safety coefficients. The required safety degree should respect all the facts that were not considered in the calculation of rated stresses (technological workmanship of weld, weld quality, internal tension, weld homogeneity, shape and finish of weld surface, weld reinforcement, ignites and penetrations, etc.). Last but not least, the direction of stress and the anisotropic properties of material in the weld must also be considered. Different weld material properties in the vertical and horizontal direction result in differing values of the safety coefficient depending on the type, workmanship and load type of the welded connection.
From the above mentioned, it is obvious that the most complicated task in strength checks of the welded connection applies to the proper choice of safety coefficient. General procedures for setting safety coefficients can be found in the document "Coefficients of safety", while specific recommendations regarding welded connections are given at the end of the chapter. The procedures to specify the rated stress for individual types of welds are detailed in the following paragraphs.
Butt welds originate in the joint gap of connected parts and are usually used as load-bearing, force welds. In order to achieve perfect workmanship of the welds, it is usually necessary to perform modification of the contact surfaces of the connected parts. The method of welded surface treatment is set by the workmanship of the connection, the thickness of the welded parts, the welding method and the accessibility of the welded spot.
When designing and performing the strength checks of welded connections, the weldment with a butt weld is considered as a solid component with a dangerous spot in the area of the weld. The load-bearing weld section will be the basic characteristic of the connection for the assessment of its load-bearing capacity.
In the calculation of butt welds, the type of welds (method of weld surface treatment) or potential weld root reweldment are not considered. The load-bearing section of the butt weld is then specified only by its thickness "a" and length "L".
Note: This program is designed for the calculation of connections with uniform, fully penetrated butt welds. The recommended procedures for handling special cases of connections (partly welded welds, intermittent welds, combined welds) can be found at the end of this chapter.
Weld throat thickness:
In order to specify the load-bearing section, the thickness of the thinner of the welded parts is considered as the butt weld throat thickness "a". Reinforcement of the weld surface and root is not considered.
Effective weld length:
In a normal type of weld, so-called "end down-slopes" are formed. They result in weakening of the section at the weld's beginning and end. The effective weld length will then be smaller than the actual length (reduced by a worse-quality weld beginning and end). For more accurate calculations, we therefore recommend controlling the load-bearing capacity of welds only for that part (length) of the weld that has a rated section. The common method of setting the effective length "L" for common weld execution (fig. a) and specially treated welds (fig. b) is described schematically in the picture.
Hint: This program is provided with the function of automatic effective weld length calculation - see the switch on line [2.6].
Strength solution of welds:
When performing strength checks of butt welds, the rated stress in the load-bearing weld section must be specified first. Depending on the respective load, the individual stress components are specified in the direction normal to the weld (^) and in the direction parallel to the weld (ll). The calculated rated stresses must not exceed the values for the permissible stress.
When specifying permissible stresses, the anisotropic properties of the material in the area of the weld must be considered. Different properties of the material result in differing values of permissible stress of the weld in the normal and parallel direction.
For connections stressed by combined load, the resulting "equivalent" stress in the weld is specified from the relation:
which for s ll = 0 can be adjusted as:
The following table specifies the relations used in the calculation of rated stresses (for respective load and workmanship of the connection):
| Load | Rated stress [MPa, psi] |
| Tensile/Press. |
