Experimental and theoretical investigations on crack spacing and stiffness of textile-reinforced concrete–strengthened reinforced concrete beams:

To improve the theory of the bending cracks spacing and the deformation of the reinforced concrete beam strengthened with textile-reinforced concrete, the experimental research was conducted first on the cracks spacing and bending performance of reinforced concrete beams with reinforced concrete through four-point bending test. Then, two theoretical derivations were conducted, analyzing the average crack spacing and the stiffness of the strengthened beam through the transformed-section method and the effective moment of inertia approach, respectively. Experimental results showed that no matter using the single-sided or U-type strengthening form, the flexural bearing capacity and crack forms of reinforced concrete beams were improved. Distribution characteristics of cracks in the strengthened beam were presented "multiple and dense" at the bottom and "few and sparse" on the top. The stiffness development of the strengthened beam could be divided into three phases: before-cracking phase, after-cracking phase, and after-yield phase, and the stiffness could be considered as unchanged in every phase. Results of average crack spacing calculated by transformed-section method corresponded with experimental results. By the effective moment of inertia approach, the calculated stiffness of the strengthened beam was slightly bigger than experimental values, which suggested that these calculating solutions may be applied into practical engineering design.