# Steel connections in SCIA Engineer 16

15.2-16.0

## Improvements in stiffness update

Version 16 of SCIA Engineer improves the workflow of steel connection design with the following tweaks in the Update Stiffness functionality:

- Both the positive and the negative branches of the moment-rotation graph are generated regardless of the sign of load effects that are selected during the design.
- If a nonlinear function is generated for a connection and a connection is defined as "nonlinear" in the connection properties, the non-linear function is automatically assigned to the hinge generated during the stiffness update.
- Open-standing issues were fixed: e.g., a non-linear stiffness assignment does not get overwritten during recalculation of the project; only one non-linear function can be assigned between two connected members.

## Weak-axis bending in strong-axis connections

Steel connection design in SCIA Engineer has been extended with support for weak-axis bending moments and related shear forces. With the current design capabilities, strong-axis moment connections can be loaded in strong- and weak-axis bending simultaneously.

The newly implemented design method is based on the following publications:

- Neumann N, Nuhic F: "Design of structural joints connecting h or i sections subjected to in-plane and out-of-plane bending,” EUROSTEEL, 2011.
- Kristensen SO, "Single-sided structural beam-to-column joint of H- or I-profiles with bolted endplate exposed to in-plane and out-of-plane bending,“Stavanger, 2010.

The calculation approach is fully based on the component method:

- additional components need to be checked due to the different alignment of the connection relative to the internal force effect (e.g., column flange in twisting, column web in bending);
- a number of components in the connection are subjected to forces coming from both strong- and weak-axis bending;
- the current extension of the connection design procedure extends and modifies the derivation of bending moment resistance, shear force resistance and stiffness;
- In the shear resistance calculation, the 28% rule is taken into account as well as modified shear areas in y and z-directions (also taking into account haunches);
- All combined bending and shear effects are considered together: a linear interaction formula is used for both moment interaction and shear force interaction.

The weak-axis bending verification method is supported for strong-axis, beam-to-column or beam-to-beam splice connections:

- between H- and I-sections;
- with bolted end-plates;
- with two bolts per row;
- that may be both symmetrical or asymmetrical for the strong bending axis of the steel beam;

In addition:

- A setting in the Connections Setup of SCIA Engineer allows the user to disable the weak-axis bending verification;
- If the user chooses to neglect weak-axis bending and a weak-axis bending moment is present in the connection, a warning is displayed that non-zero design bending moments for the weak axis are present and that the method is switched off.
- If the user chooses to enable the weak-axis bending verification and (1) the connection geometry is not supported by the design method AND (2) weak axis bending is present in the connection, the calculation results in an error.
- The output of the connection design in SCIA Engineer has also been adapted to reflect the described extensions. Details in tabular form are provided for e.g., bolt-row classification and effective length of yield-line patters also for the weak-axis bending verification.

29/03/2016