PSI - Issue 64

Szymon Grzesiak et al. / Procedia Structural Integrity 64 (2024) 269–276 S. Grzesiak, C. de Sousa, M. Pahn / Structural Integrity Procedia 00 (2019) 000 – 000

275

7

3 2 ∙ (f ck ) 1 2 +0.12 · σ cp ) ∙ d s1 ∙ b c

V Rd,c ≥V Rd,c,min =( 0.0 γ 525 c ∙ k

(4) Another formula for the calculation of resistance V Rd,c,fe is taken from studies performed by Jansze (1997) and Finckh (2012). In the study of Finckh the formula for mean value contains a correction factor k k = 0.72 instead of 0.75. The well-known verification format is applied, where the resistance V Rd,c,fe should be greater than the acting shear force V Ed (see Formula 2). V Rd,c,fe = (0.18 · √3 · d s1 a V 3 · k ∙ √100 ∙ ρ s1 · f cm 3 ) ∙ d s1 ∙ b c with a V = √ (1−√ρ s1 ) 2 ρ s1 ∙ d s1 ∙ a f 4 (5) The analytical results were analyzed considering the shear force (see Table 4). The safety factor γ c is assumed to be 1.0 on the mean value level. The value for the shear resistance V Rd,c for this concrete beam, which has no shear reinforcement, is equal 1.78 kN (Formula 3) and is greater than V Rd,c,min with value 1.22 kN (see Formula 4). Based on this, and according to fib -Bulletin, the resistance V Rd,c,fe is equal to 4.12 kN (Formula 2) with a longitudinal steel reinforcement ratio equal to 0.015. Table 4. Results of analytical investigation. Test series V Rd,c,fe acc. to fib- guideline η (%) V Rd,c,fe acc. to DAfStb (2012) η (%) V Rd,c,fe acc. to Jansze (1997) η (%) V Rd,c,fe acc. to Finckh (2012) η (%) Unfortunately, the computed values according to DAfStb and Finckh led to a significant overestimation (above 10 kN). The values are therefore on the unsafe side and they were therefore not be taken into account in this study. Reason for this is the expression of the value of a f in the potency of factor CaL = 0.36 or CaL = 0.40. This leads to a small value in the denominator, which raises the value of the resistance V Rd,c,fe . Quotient values were then computed to express in percentage terms how much the experiment and the analytical approach agree (see Formula 6). For the B1, B2 and B3 test series, values of 90 %, 78 % and 78 %, respectively, were obtained. η= V exp V Rd,c,fe ·100 % (6) 4. Conclusions In a newly developed test setup, concrete samples strengthened using FRP reinforcement were tested until failure. CT scans were carried out on the basis of a pair of test specimens to evaluate the potential of this NDT method. Based on the results of this experimental and analytical investigation, the following conclusions are drawn: • The steel reinforced and FRP strip as well as defects such as cracks in concrete can be well segmented in 3D data made from CT scans. The methodology for segmenting the elements is presented in this paper. • The obtained failure mode (concrete cover separation) could be very well observed 3D-volume format. Furthermore, the crack surface inside the concrete sample could be inspected in detail. • There is agreement between the recalculation of the tests according to fib -guideline (fib Bulletin 90 (2019)) and the experimental results. No agreement was achieved when using the DAfStb-guideline (DAfStb 591). In addition, it is also outlined in this article that continuous investigation in this field is needed, namely for development of new testing approaches and image processing algorithms that further develop the methods for monitoring and damage control using non-destructive testing based on computed tomography. B1 B2 B3 4.12 kN with: k k =0.75, CaL=1,00 c ρ =0.15 90 78 78 11.85 kN with: k k =0.75, CaL=0,36 c ρ =0.15 31 27 27 5,25 kN with Formula 5 71 62 61 10.46 kN with: k k =0.72, CaL=0,40 c ρ =0.18 36 31 31