Calculation of the Cracking Moment of a Flexible Concrete Element Reinforced with Fiberglass Fitting

Purpose of reseach. This article discusses the normalized methods for calculating the cracking moment in elements of fine grained concrete, reinforced with fiberglass fitting without prestressing.  

Methods. In concrete elements reinforced with composite fitting, it is proposed to determine the cracking moment in the same way as reinforced concrete structures that use a nonlinear deformation model that provides a single connection when calculating the first and second groups of limit states. At the same time in current standards it is allowed to apply the calculation of the cracking moment using the elastoplastic section modulus. Accurate determination of the cracking moment is an important element of the calculation for the second group of limit states, especially the consistency of theoretical data with experimental data for concrete elements reinforced with fiberglass fitting. The following calculation methods are considered: using the elastoplastic moment and calculation using a nonlinear deformation model (two- and three-line diagrams of concrete state with parameters). Experimental data from the experiment have been taken as the initial data for the calculation of the cracking moment for the considered methods. We have considered four beams reinforced with fiberglass fitting, and one - metal. Fitting is without prestressing.  

Results. The analysis of the results of the calculation of the cracking moment is carried out by the given methods. For comparison with experimental data, the load on the beam corresponding to the cracking moment is determined. A comparative analysis of the considered methods for the calculation of the cracking moment with experimental data is performed. The calculation using the three-line concrete state diagram is the closest to the experimental results, and when using the technique with the two-line diagram, there is a margin of more than 20%.

Conclusion. These methods, based on the calculation of reinforced concrete structures, provide a reasonable convergence of results when using fiberglass fitting but provide the greatest accuracy to the experimental data for steel fitting within 9%.

cracking moment, composite fitting, concrete element, elastoplastic section modulus, nonlinear deformation model

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