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The calculations related to column base connections is in general given by EN 1993-1-8, Article 6.2.8.
The bending moment resistance Mj,y,Rd is further elaborated in EN 1993-1-8, Article 6.2.8.3. Within SCIA Engineer the bending moment resistance is calculated only in case design bending moment My,Ed is not equal to zero.
The calculation within SCIA Engineer itself consist of several steps:
- The connection is split into the left and right side. The axis is located in the centroid of the connected cross- section, taking into account all possible haunches. The calculation of centroid neglects the presence of cross-sectional roundings. The left side is considered as the side which lies in the direction of the z-axis of the LCS of the connected beam. The right side is considered as the side which lies in the opposite direction of the z-axis of the LCS of the connected beam.
- The bolt-rows are assigned either to the left or right side, depending on their coordinate. Bolt-rows located at the position of the centroid or at the distance closer or equal than half of the bolt diameter are not assigned to neither of the sides and thus neglected in the bending moment and rotational "Stiffness calculation".
- Possible tension lever arms zT and compression lever arms zC are calculated for each of the sides.
The tension lever arm zT for particular side is calculated as:
with:
| hi | distance from the bolt-row assigned to the side to the centroid of the connected cross-section |
| nbr | number of bolt-rows assigned to the side |
The compression lever arm zC for particular side is taken equal to the distance from the centroid of the connected cross-section to the "Center of compression".
- The calculation of eccentricity e, depending on the design internal forces, given by the formula in Table 6.7. If the design normal force NEd is equal to zero, eccentricity e is set equal to the lever arm zC of the side, where the compression due to the moment is developing.
- The determination of the lever arm z for column base connections given by Figure 6.18 in the EN 1993-1-8 Article 6.2.8, depending on the case.
- Determination of the case using the conditions given by the EN 1993-1-8 Article 6.2.8.3 Table 6.7.
- The final bending moment resistance Mj,y,Rd is calculated, according to the formulas given by EN 1993-1-8 Table 6.7 for recognised case, as the minimum of the absolute values of the semi-resutls.
The design tension resistance F T,l,Rd of the left side of the joint is calculated according to EN 1993-1-8 Article 6.2.8.3 (2). It is the minimum resistance of the components below:
- the column web in tension under the left column flange Ft,wc,Rd
- the base plate in bending under the left column flange Ft,pl,Rd
The design tension resistance F T,r,Rd of the right side of the joint is calculated according to EN 1993-1-8 Article 6.2.8.3 (3). It is the minimum resistance of the components below:
- the column web in tension under the right column flange Ft,wc,Rd
- the base plate in bending under the right column flange Ft,pl,Rd
Only individual bolt-rows assigned to the particular side are considered in the calculation of the component resistances. The group approach calculation is not implemented at the moment.
The design compressive resistance F C,l,Rd of the left side of the joint is calculated according to EN 1993-1-8 Article 6.2.8.3 (4). It is the minimum resistance of the components below:
- the concrete in compression under the left column flange Fc,pl,Rd (the outer flange is considered in case haunch with flange is present on the side)
- the left column flange and web in compression Fc,fc,Rd (in case haunch with flange is present on the side, the initial component is replaced by the components "Haunch flange in compression"and "Beam web in compression")
The design compressive resistance F C,r,Rd of the right side of the joint is calculated according to EN 1993-1-8 Article 6.2.8.3 (5). It is the minimum resistance of the components below:
- the concrete in compression under the right column flange Fc,pl,Rd (the outer flange is considered in case haunch with flange is present on the side)
- the right column flange and web in compression Fc,fc,Rd (in case haunch with flange is present on the side, the initial component is replaced by the components "Haunch flange in compression"and "Beam web in compression")
For further info on calculation of the Concrete in compression components see chapter: "Normal force resistance".