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Redystrybucja momentów zginających w dwuprzęsłowych belkach betonowych zbrojonych prętami FRP

Szczepański Konrad, Kotynia Renata

Materiały Budowlane

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2023

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nr 4

36--40

PL

W artykule przedstawiono przegląd badań dotyczących zbrojenia niemetalicznego w aspekcie redystrybucji momentów zginających w elementach dwuprzęsłowych. Przegląd badań obejmuje analizę wpływu parametrów zmiennych dotyczących stopni zbrojenia podłużnego, typu zbrojenia (FRP/stal), klasy betonu oraz zbrojenia poprzecznego. Na podstawie przeglądu wiedzy zaproponowano program badań własnych.

EN

This paper presents a review of research on nonmetallic reinforcement in terms of redistribution of bending moments in double-span elements. The research review includes an analysis of the influence of variable parameters concerning: degrees of longitudinal reinforcement, type of reinforcement (FRP/steel), concrete class and transverse reinforcement. Based on the foreign studies the own research program has been proposed.

2

Moment redistribution in steel continuous beam according to limited plasticity concept

Maślak M.

Zeszyty Naukowe Politechniki Rzeszowskiej. Budownictwo i Inżynieria Środowiska

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2009

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z. 52 [264]

125-134

EN

Conventional approach to elastic-plastic analysis of steel continuous beam, according to which it is assumed that two plastic hinges occur in an edge span at the ultimate limit state, not always gives safe evaluations of real member resistance. The reason is mainly the possibility of unlimited accumulation of permanent strains. Therefore some limitations of moment redistribution should be defined. Two of them are proposed and discussed by the author . It is accepted that the first plastic hinge arises in the cross-section in which maximum elastic bending moment is induced; however, in the second critical cross-section its appearance is not admissible. Only elastic in the first case, or limited elastic-plastic ultimate moment in the second example is there considered. The design methodology presented in the article is connected with the reduction of member redundancy and transformation of the whole beam into unstable mechanism is not allowable.

3

Behaviour of prestressed continuous beams

Lopes S., Harrop J.

Archives of Civil Engineering

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1998

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Vol. 44, nr 1

89-105

EN

In previous research works on redistribution of moments, beams have generally been constructed in one piece and transported to the test rigs and then placed on the supports. Great precautions have to be taken when leveling the supports because small deviations from the correct position can introduce large values of unwanted moments corresponding to support settlements. Ideally, at least one support should have a measuring device to measure forces and a threaded device should also be provided to adjust the height of the support as the test progresses. The new technique described in this paper consists of joining two separate precast beams over the supports and maintaining the contact surfaces beams/supports undisturbed even when a top flange is cast in situ. This procedure minimises possible inaccuracies caused transportation and placement of the beams and is closer to the conditions of beams in practice. The paper also describes main results obtained from prestressed composite concrete two-span beams and its implication on codes practice.These codes normally allow an elastic analysis of the structure followed by an adjustment on the diagram of bending moments at the ultimate limit state. In the case of a continuous beam the adjustment is obtained by multiplying the bending moments over the supports by a coefficient, delta, and modifying the whole diagram of bending moments to maintain the static equilibrium of the structure.