The STS application performs structural safety analyses of steel column system. Singlepiece and double symmetrical cross sections are allowed. The verification is performed on the basis of ideal bifurcation loads for lateral buckling, torsional buckling and lateral torsional buckling.
Column systems The following structural systems are supported:  Cantilever column  Hinged column  Column pinned on top and restrained on bottom  Column restrained on top and on bottom
These supporting conditions always apply to both main axes. Discrete lateral supports and continuous elastic bedding can be defined in addition. For more complex supporting conditions, an interface to the BT II application is available. Appended hinged column
Cantilever columns are often used as bracing elements in hinged column systems. STS calculates automatically the corresponding equivalent loads and takes the change of the effective length into account.
Basis of calculation You can perform the design either in accordance with  DIN 18800  EN 1993
In combination with EN 1993, the regulations of the corresponding National Appendix are taken into account.
The following National Appendices are available yet:  DIN EN 1993  ÖNORM EN 1993  BS EN 1993  NEN EN 1993  NBN EN 1993  CSN EN 1993
We currently work on the implementation of additional appendices.
Analyses The following verifications are performed:  Elastic or plastic cross sectional resistance.  Resistance of the system to lateral buckling, torsional buckling and lateral torsional buckling  Serviceability
Cross sections STS allows you to calculate columns with the following types of cross sections:  Standard Isections  Userdefined doublesymmetrical Isections  Standard round and square hollow sections  Userdefined round and square hollow sections
Lateral supports Lateral supports can be defined to secure the columns against stability failure. You can enter lateral supports in STS either as a continuous support in the form of elastic bedding or as discrete supports in  the middle of the span  the third points  the quarter points or  at a point x0.
Actions You can expose the column system to vertical and horizontal loading and define head and base moments. However, you cannot define loading that produces planned torsion. Furthermore, you can define appended hinged columns in the directions of the both main axes and optionally apply the selfweight of the column as a resultant to the column head.


Combinations of actions STS generates automatically the appropriate load cases and load case combinations, depending on the defined actions, and performs the necessary analyses, whereby the decisive load case combination is determined for each limit state. Predefined loads In order to simplify the load definition, STS offers a range of predefined loads that are sufficient for most systems.
Optionally available are:  Vertical loads  Horizontal loads  Bending moments
You can enter  wind from y/z direction and  accidental impact loads in y/z direction as span loads applying to the column head.
Calculation STS calculates the internal forces and the deformations in firstorder analyses and determines the ideal bifurcation loads, the slenderness ratios and the reduction factors for the stability verifications in accordance with the equivalent bar method. The bifurcation loads are determined numerically with consideration to the torsional rigidities. Therefore, the user can also perform structural safety analyses in accordance with the equivalent bar method for more complex loading situations.
Interfaces to other applications The characteristic bearing forces can be transferred to the applications FD, ST3 and ST6. If the real load conditions do not comply with the defined standard or the loading situation leads to planned torsion, you cannot use STS for the calculation. If you have a valid licence for the BTII application (2nd Order Buckling Torsion Analyses), you can transfer the structural system to perform second order buckling torsion analyses, if required.
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