Tilt stability

Tilt stability of forked parallel chord and gable roof girders
made of reinforced or prestressed concrete.

On the basis of a calculation method according to II. On the basis of a calculation method according to second-order theory, which takes into account both geometric and physical nonlinearities (Diss. Röder - Program KIPPEN), an approximation method has been derived for the case of a single-span girder supported by forks on both sides under line load, which frequently occurs in practice. The approximation method is valid for parallel chord and gable roof trusses and performs the verification of the safety against overturning by means of a verification of the ultimate limit state for biaxial bending. The simplifications of the approximation method are based on the use of linear, sinusoidal, parabolic and polynomial approaches for the courses of stiffnesses, bending moments, deformations and load application points over the girder length, whereby the governing differential equations can be integrated in a closed manner. With the derived formulas, the required bending moments can be determined and the ultimate limit state design is performed (program KIPNT2).

• Röder,F.-K., Kippstabilität ausgewählter Spannbeton- und Stahlbetonträger, Abschlussbericht eines vom Hauptverband der Deutschen Bauindustrie geförderten Forschungsvorhabens, Institut für Massivbau, TH Darmstadt, 1981

• Röder, F.-K.: Calculation of reinforced concrete and prestressed concrete beams according to theory II. Order. Dissertation D17, TH Darmstadt 1982, (also compiled in revised and updated form in Appendices A to E of the following research reports "Kippstabilität von Stahlbeton- und Spannbetonträgern")
  https://doi.org/10.13140/RG.2.2.29882.06083

• Technical paper"Zur Kippstabilität vorgespannt und nicht vergespannter, parallelgurtiger Stahlbetonträger mit einfach symmetrischem Querschnitt"  in Beton- und Stahlbetonbau 86 (1991), H.2, pp.25-32 and H.3, pp.59-64.
• Technical paper"An approximation method for assessing the tilting stability of saddle roof trusses made of reinforced or prestressed concrete" in Beton- und Stahlbetonbau 92 (1997), H.11, p.301-307, and H.12, p.341-347.
• Research report "Kippstabilität von Stahlbeton- und Spannbetonträgern 1.Auflage", Universitätsbibliothek Kassel 1999, ISBN 3-89792-008-5 (out of print)
• Research report "Kippstabilität von Stahlbeton- und Spannbetonträgern 2. überarbeitete und aktualisierte Auflage", kassel university press 2015, ISBN 978-3-86219-934-1, (Summary,Summary,Résumé)
• Technical paper "Approximate consideration of concrete creep in the verification of the overturning stability of reinforced concrete beams", Beton- und Stahlbetonbau 7/2016, pp.419-430
  https://doi.org/10.1002/best.201600022

• Technical paper "Estimation of the tilting stability for fork-supported single-span beams made of reinforced concrete and prestressed concrete" in Beton- und Stahlbetonbau 117 (2022), H. 2, pp. 119-132
  https://doi.org/10.1002/best.202100085

• The programs KIPPEN and KIPNT2 initially only took into account the material specifications according to DIN 1045:1988 and DIN 4227:1988 and have been extended over time via DIN 1045-1: 2001-07 with DAfStb booklet 525 (explanations on DIN 1045-1, Sept. 2003, and corrections, June 2005 ) to DIN 1045-1:2008-08 and finally to DIN EN 1992-1-1:2011-01 with national annex and DAfStb booklet 600 (explanations on DIN EN 1992-1-1:2011-01, 2012). All material specifications of the three DIN regulations can be selected.
• As of version 5.x, the KIPNT2 program has been extended by a graphics module so that the governing stiffness curves can additionally be displayed on the screen.
• In the KIPNT2 program, the stiffness curves were first approximated with fixed functions either as a sine or as a 6th order parabola (up to version 4.x). However, this default is too rigid and not always applicable. In order to better adapt the stiffness curves to the actual conditions, the stiffnesses in the twentieth points are now determined, and then the polygon course is approximated by a polynomial up to the 6th order. (Test versions 5.x and from version 6.x)
• The program KIPNT2 has been extended to the effect that from version 7.x onwards, for calculations according to DIN EN 1992-1-1:2011-01 or DIN 1045-1:2008-08, checks for shear force and torsion at the support cross-section are always performed with the determined internal forces. The results are output following the results of the stability analysis.
• A second enhancement in KIPNT2 now allows the long-term behavior of a beam to be approximated as well. This is based on a simplified consideration of creep in the stress-strain curve of the concrete according to booklet 600 DAfStb, Figure H5-15.
• Due to the progressive renewal of the Windows operating system, the Fortran compiler had to be changed for version 8.x. The graphics output has also been renewed as a result. As a result, the graphics output has also been renewed and extended. Whereas previously only the determined stiffness curves were displayed, the cross-section and the material behavior of the concrete used are now also shown.

The calculation program KIPNT2 (zip file) for this approximation method has been prepared for practical use with a detailed user manual (PDF) and the additional program EIN_NT2QUW for editing the input data. The program is FREEWARE from 2024. The licensing and activation required until the end of 2023 will no longer apply!

The KIPNT2 program was developed under the Windows XP operating system. The current program versions have been revised with the FTN95-Fortran from Silverfrost and run under all Windows operating systems from Windows XP. The required software is supplied with the calculation program. Further details can be found in the installation instructions (PDF).

To install, copy the zip file to a hard disk area of your choice and extract this zip file.

For the specified load case.

commented result printout of the example see user manual page 25-51