ON ANCHORING OF THE LONGITUDINAL TENSILE REINFORCEMENT IN REINFORCED CONCRETE BEAMS WITHOUT PRE-STRESSING
Journal Title: Вісник Національного університету "Львівська політехніка". Серія "Теорія та практика будівництва" - Year 2018, Vol 0, Issue 904
Abstract
The character of oblique cracking is significantly influenced by the method and reliability of anchoring of the longitudinal tensile reinforcement on the hinge support beams. In many experimental researches the lack of anchoring caused the premature destruction of beams along the sloping cracks. Nevertheless, such destruction of a beam along the sloping crack, at the violation of anchoring on the hinge support, should not be referred to the type of destruction under the influence of internal efforts, caused by the external loading. Pulling out of longitudinal bars of reinforced concrete beams on support, as a result of concrete cracking and adhesion violation, should be considered as a drawback of the supporting part constructing. It is incorrect to take such beams into consideration at doing the analysis of the bearing capacity of sloping cuts, because anchoring is a separate issue in the theory of reinforced concrete studies. The experimental research has shown that even by maintaining standards of current design norms concerning the length of anchoring of the longitudinal reinforcement beams are ruined because of the lack of adhesion of the longitudinal reinforcement with concrete without achieving the strength of the sloping cut. The peculiarity of the bending reinforced concrete elements is the fact that at loading effect the diagram of the stretching effort in the longitudinal reinforcement does not correspond to the diagram of the bending moments as a result of the partial loss of the reinforcement adhesion with concrete after the creation of vertical cracks, which are allowed by design norms at the exploitation loadings. To solve this problem it is suggested to use the notion of “the rule of strengthening of the stretching effort”, available in current design norms [1] and Eurocode 2 EN 1992-1-1:2004 [2] for determining the place of break in the span. We suggest quite a different approach which is based not on the displacement of stretching effort, but on the displacement of the diagram of bending moments. This method was suggested by L. O. Doroshkevych for the calculation of the shear reinforcement. The discrepancy of the stretching effort change in the longitudinal reinforcement and the diagram of bending moments is taken into account by the coefficient of diagram of moments displacement which is determined with the help of developed nomograms. The article presents the example of calculation of the anchoring length of the longitudinal reinforcement by the suggested method.
Authors and Affiliations
Solomiia Maksymovych, Olha Krochak
Keywords
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