Influence of Effective Length of Elements on the Critical Parameters of Frame-Rod Structural Systems’Stability

Purpose of research.This article considers the influence of changes in the effective length of frame-rod structural systems elements operating under the conditions of constrained bifurcation.

Methods.A sign of the end moments and transverse forces has been taken as the criterion of the form of stability loss ofa frame-rod structural system element. Using this criterion, an expression has been obtained to assess the effect of changes in effective length of the frame struts on the critical parameters of the entire system, which allows varying the geometry of the structure to affect its performance.As an example, the critical parameters of the stability of a two-span frame designed from wood have been defined, to the middle element of which we apply central force Ркр, and to the extreme elements we apply forces multiplied by the coefficient α- αРкр. The type of elements’ bifurcation of the considered constructive system (constrained or forced) before and after the change of effective length of its elements has been revealed. The calculation of the unknown reactions and internal forces of the system were performed using special functions of the displacement method.

Results.Changes in efffective length of elements that lose stability passively do not significantly affect the critical stability parameters of the frame-rod structural system. At the same time, a 30% reduction in effective length of struts being in active bifurcation leads to a 50% reduction in the critical force.

Conclusion.Quite simple algebraic dependences are presented in the paper that allowus to identify elements of frame-rod systems. Their change in effective length has a significant impact on the critical parameters of the entire structure’ stability. At the same time, these criteria allow us to evaluate the resistance resource of centrally compressed elements of frame-rod structural systems.

1. Aleksandrov A.V. Issledovanie ustoichivosti konstruktsii arochnogo pokrytiya zala s ispol'zovaniem kriteriev vyyavleniya naibolee opasnykh elementov [Investigation of the sustainability of structures of the arch covering of the hall using the criteria for identifying the most dangerous elements]. Vestnik otdeleniya stroitel'nykh nauk RAASN,2004, vol. 8, pp. 14-21 (In Russ.).

2. Aleksandrov A.V., Matveev A.V. [Criteria for identifying the most dangerous elements and their use in problems of structural stability]. Bezopasnost' dvizheniya poezdov. Tr. 4-i nauch.-prakt. konf.[Safety of train traffic. Tr. 4th scientific-practical. conf.]. Moscow, 2003, pp. III — 1 — III — 2 (In Russ.).

3. Aleksandrov A.V., Travush V.I., Matveev A.V. O raschete sterzhnevykh konstruktsii na ustoichivost' [On the calculation of stability of core structures].Promyshlennoe i grazhdanskoe stroitel'stvo = Industrial and Civil Construction, 2002, no. 3, pp. 16-20 (In Russ.).

4. Aleksandrov A. V. Rol' otdel'nykh elementov sterzhnevoi sistemy pri potere ustoichivosti [The role of individual elements of the core system in the event of loss of stability].Vestnik MIITa = Bulletin of Moscow Institute of Railway Transport, 2001, vol. 5, p. 46 (In Russ.).

5. Matveev A. V. Nekotorye voprosy sozdaniya spetsializirovannogo programmnogo kompleksa dlya analiza mostovykh konstruktsii [Some issues of creating a specialized software for the analysis of bridge structures].Vestnik MIITa = Bulletin of Moscow Institute of Railway Transport, 2002, vol. 7,pp. 76-83(In Russ.).

6. Dubrakova K.O. Voprosy ustoichivosti staticheski neopredelimykh sistem iz drevesiny [Questions of sustainability of statically indefinable systems of wood]. BST: Byulleten' stroitel'noi tekhniki =BST: Bulletin of construction equipment, 2018, no.11, pp. 54-55 (In Russ.).

7. Pyatikrestovsky K. P., Travush V. I. O programmirovanii nelineinogo metoda rascheta derevyannykh konstruktsii [On programming non-linear method of calculating wooden structures].Academia. Arkhitektura i stroitel'stvo =Academia. Architecture and construction, 2015,no. 2, pp. 115-119 (In Russ.).

8. Pyatikrestovsky K. P., Khuganov H.S. Nelineinye deformatsii staticheski neopredelimykh derevyannykh konstruktsii [Nonlinear deformations of statically indefinable wooden structures]. Izvestiya vysshikh uchebnykh zavedenii. Stroitel'stvo = Proceedings of higher educational institutions. Building, 2013,no. 11-12,pp. 21-30 (In Russ.).

9. Klyueva N.V., Dmitrieva K.O. Voprosy ustoichivosti sterzhnevykh elementov konstruktivnykh sistem iz drevesiny pri silovom i sredovom nagruzhenii [Questions of sustainability of core elements of structural systems made of wood under force and environmental loading].Stroitel'stvo i rekonstruktsiya = Construction and reconstruction, 2016, no.4, pp. 13-18(In Russ.).

10. Pyatikrestovsky K.P.Nelineinye metody mekhaniki v proektirovanii so-vremennykh derevyannykh konstruktsii [Nonlinear methods of mechanics in the design of modern wooden structures]. Moscow, MGSU Publ., 2014, 320 p.(In Russ.).

11. Klyueva N.V., Dmitrieva K.O. Analiz ustoichivosti sterzhnevykh konstruktsii iz drevesiny pri silovom nagruzhenii i peremennoi vlazhnosti [Analysis of the stability of wood core structures under power loading and variable humidity].Nauchnyi vestnik voronezhskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. Ctroitel'stvo i arkhitektura = Scientific Herald of the Voronezh State University of Architecture and Civil Engineering. Construction and architecture, 2016, no.3, pp. 17-24 (In Russ.).

12. Klyueva N.V., Dmitriev K.O. Voprosy ustoichivosti sterzhnevykh elementov konstruktivnykh sistem iz drevesiny razlichnykh porod pri silovom i sredovom nagruzhenii v usloviyakh povyshennoi vlazhnosti [Questions of sustainability of the core elements of structural systems of wood of various species under force and environmental loading in conditions of high humidity].Stroitel'stvo i rekonstruktsiya = Construction and reconstruction, 2016, no.5, pp. 60-68 (In Russ.).