PSI - Issue 64

Tom Molkens et al. / Procedia Structural Integrity 64 (2024) 1484–1491 Tom Molkens & Mona El-Hallak/ Structural Integrity Procedia 00 (2024) 000 – 000 4 ² (2 −1)) 2 + 2 (ℎ − − 2 ) ( 4 ² (2 − 1)) − ( 4 ² (2 −1)) = 3 3 +(2 − 1) 4 ² (ℎ − − 2 − ) 2

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4

= √(

(4)

(5)

In addition, the distance x c between the centroid of the cracked section and the most compressed fiber is used to determine the crack stiffness. Due to the small difference between E g and E cm , the same formulae are used as an approximation for those beam sections with non-symmetrical reinforcement. The crack moment is determined from the uncracked modulus of elasticity and the bending tensile strength f ct (assumed to be 0.9× the measured splitting strength f ct,sp ). Obviously, the effect of its own weight should be subtracted to determine the load for cracking P cr . = 6ℎ² = 0,9 6ℎ² , (6) 3.2. Material properties The day before the tests (at 241 days of age), classical compression tests and splitting tests were carried out on three cubes, each with a side of 150 mm. Other material parameters were derived from these tests in accordance with EN 1992-1-1. The ready-mixed concrete was ordered as C30/37, consistency class S4, Dmax = 20 mm, and with cement CEM III/B 42.5N LH LA. Glasspree FL E46 round bars from Sireg were used as bending reinforcement at the bottom and locally above the support point. The bars are externally coated with silica sand and resin during the continuous production process. Ordinary ribbed BE500A reinforcing bars were used for the stirrups and structural reinforcement at the top. Table 1 summarizes the main materials parameters: Table 1. Mechanical material parameters. Properties f cm,cube /f y (N/mm² or %) Coefficient of variation (-) Comment Compression strength concrete 45.3 0,045 Based on three tests Splitting tensile strength 3.32 0,032 Based on three tests Tensile strength of Glasspree f ft 1224 0.051 Testing report Characteristic tensile strength f fk Ø16 mm 850 - Datasheet Sireg Guaranteed bond strength f b >8 - Datasheet Sireg Tensile elastic modulus of Glasspree 46000 - Datasheet Sireg Ultimate strain ε u 1.8 % - Datasheet Sireg Yield strength of ordinary reinforcement f y 500 - Nominal value Modulus of elasticity of reinforcing steel E s 200000 - Nominal value Based on the specified modulus of elasticity of the GFRP reinforcement, the positive contribution to the moment of inertia is limited by Eq. (3) to only 0.67%. 3.3. Test setup From the static model (Figure 1), it can be deduced that for a redistribution factor δ equal to 1 (none), the negative moment extends over a distance equal to 0.27 L . No shift of the moment curve was applied to actually cause a slip, the hypothesized mechanism that can provide ductility, as explained in the introduction. With a span of 1.30 m, the top reinforcement was therefore limited to 0.35 m to the left and right of the central support point (total length 0.70 m). Measurement of the slip of the top reinforcement (a central bar, see Figure 2) was possible by providing a cut-out in