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The rotational stiffness of a joint is in general calculated according to EN 1993-1-8 Article 6.3.
Stiffness calculation for joints other than column bases is taking into account only bolt-rows located above centre of compression (See also chapter: "Center of compression"). Bolt-rows used only for shear are also not taken into account in stiffness calculation.
Stiffness model for strong-axis bending for bolted beam-column joint. There might be different components used in the model based on the connection type. (See also chapter: "Stiffness coefficients").
For bolted end-plate connections, the basic components related to each single bolt row, are represented by a single effective stiffness coefficient keff,r as given by EN 1993-1-8 Article 6.3.3.1 (2). These effective stiffness coefficients for each bolt-row are, based on EN 1993-1-8 Article 6.3.3.1 (1), transformed to the equivalent stiffness coefficient keq, to be used finally in the final stiffness formula specified by EN 1993-1-8 Article 6.3.3.1 (4). The leverage arm zeq is given by EN 1993-1-8 Article 6.3.3.1 (3).
The basic formula for calculation of rotational stiffness specified in EN 1993-1-8, Article 6.3.1 (4) is used, independently of the 5% Npl,Rd limit defined by the same article.
Stiffness calculation for column base connections is calculated according to EN 1993-1-8 Article 6.3.4 Table 6.12:
The calculation is done separately for left and right side of the connection, depending on the fact whether the side is in tension or compression. For further info see chapter: "Bending moment resistance".
Stiffness coefficient for tension side kT is calculated as:
with:
|
keff,r |
effective stiffness of bolt row r given by EN 1993-1-8, Article 6.3.3.1 (2) |
| zr | distance from the bolt-row r to the centroid of connected section |
|
zT |
average distance of bolt-rows on the tension side to the centroid of connected section |
Stiffness coefficient for compression side kC is taken equal to the stiffness coefficient for component concrete in compression k13.
For further info see chapter: "Stiffness coefficients".
The rotational stiffness is not calculated for column base connections in case the design bending moment is equal to zero.
The program makes a distinction between three stiffness types:
As specified µ is the stiffness ratio Sj,ini/Sj. Determination of this stiffness ratio is specified by EN 1993-1-8, Article 6.3.1 (6). The value of coefficient ψ is given by Table 6.8.
The moment-rotation diagram is based on the values of Sj,ini and Sj,MRd.
